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Old 07-04-2024, 02:29 PM   #1
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Is a DC to DC Charger Really Needed?

Let me say 1st that I have put all thing related to Lithium off because it has always been a very pricey proposition and of little value for how we use as the genny recharges nicely.

However, I have seen Lithium 100ahs batteries as low as $160, $250 for a new Progressive Dynamics Converter and a 40amp DC to DC for as low as $110

Given that I may soon want to replacing my AGM batteries, I question if all of these modifications despite the low cost are really necessary in my situation?

My Goal:

Increase the available AH capacity in the same space as two Group 31 AGMs

Note: I don't have any Solar and have zero interest in Solar. I can go 2 months or longer not connected to anything and not have any issues with battery draw.

Why I am confused:
a) I have been reading that some companies are now saying that converter's FLA algorithm is not as bad as once thought on Lithium batteries. Yes when charging you reach a plateau, but it will still charge a lithium battery but maybe an hour or two longer?

b) Some owners say they have dropped Lithium batteries in and not installed a DC to DC and never had any issues.

Context of how I may use if I go this direction:

Today we make it fine for two days off 125ah. I normally run the genny for 2hr/day when boondocking just to top off. Never an issue, noise not a problem, and we never overnight anywhere nor where we would be close to someone else that our genny would disturb them.

Regardless, my chops are licking to buy two 100ah Lithiums because they are so inexpensive now, plus as I understand it, I would have 190ah of available capacity that is +65lbs for us, 100 lbs less than my SLR125s, with a longer life.

I like simplicity. If I do need a DC to DC charger is 40amp all I would need? Also what is the problem if Alternator and the DC to DC are charging at the same time?

Today when we drive our Norcold absorption fridge is always on (4 years now) ever an issue with it being on inverter circuit, batteries are usually fully charged. That will not change with Lithium batteries if we buy.
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Old 07-04-2024, 06:19 PM   #2
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I have a 2015 Vista and in that time frame the standard alternator was rated as capable of 175 amps output at 1500 RPM and above.

A 100 amp-hour lithium battery when at low state of charge EACH can absorb up to 100 amps when presented with alternator charging voltage The lithium battery makers recommend limiting the charge current to 50 amps max per 100 amp-hour of battery.

So DC-DC serves three purposes, first to limit the maximum charging current to within the battery maker specs. Second, if you have more than 100 AH of Lithium batteries it limits the max draw to less than the alternator's Ford rating. If you go above the Ford rating you risk over taxing the alternator and causing it's premature failure. Third, the DC-DC converts what ever voltage the alternator puts out to the 14.4 required to fully charge the lithium batteries, this way the alternator can step back its output voltage and the lithiums still get fully charged. The alternator normally steps back from 14.4 when it senses the chassis battery is at a high state of charge.

The only other detail of installing a DC-DC charger is that you have to disable the Chassis -> Coach battery system contactor so that it does not close when the ignition is on. On my RV I have a smart BMS that I was able to configure the BMS to allow Coach system to charge Chassis system when Ignition is off, and also still able to connect the two battery systems together with the dash Boost switch. Others completely replace the OEM contactor and put in a new one that is purpose built for Lithium battery installs.

Personally I use a Renogy 40 amp max output DC-DC charger, currently costing around $ 170. Renogy now sells a 60 amp for only $ 30 more that if doing a new install and if installing more than 100 AH of Lithium batteries I would use that one.
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Old 07-04-2024, 07:55 PM   #3
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Quote:
Originally Posted by powercat_ras View Post
I have a 2015 Vista and in that time frame the standard alternator was rated as capable of 175 amps output at 1500 RPM and above.

A 100 amp-hour lithium battery when at low state of charge EACH can absorb up to 100 amps when presented with alternator charging voltage The lithium battery makers recommend limiting the charge current to 50 amps max per 100 amp-hour of battery.

So DC-DC serves three purposes, first to limit the maximum charging current to within the battery maker specs. Second, if you have more than 100 AH of Lithium batteries it limits the max draw to less than the alternator's Ford rating. If you go above the Ford rating you risk over taxing the alternator and causing it's premature failure. Third, the DC-DC converts what ever voltage the alternator puts out to the 14.4 required to fully charge the lithium batteries, this way the alternator can step back its output voltage and the lithiums still get fully charged. The alternator normally steps back from 14.4 when it senses the chassis battery is at a high state of charge.

The only other detail of installing a DC-DC charger is that you have to disable the Chassis -> Coach battery system contactor so that it does not close when the ignition is on. On my RV I have a smart BMS that I was able to configure the BMS to allow Coach system to charge Chassis system when Ignition is off, and also still able to connect the two battery systems together with the dash Boost switch. Others completely replace the OEM contactor and put in a new one that is purpose built for Lithium battery installs.

Personally I use a Renogy 40 amp max output DC-DC charger, currently costing around $ 170. Renogy now sells a 60 amp for only $ 30 more that if doing a new install and if installing more than 100 AH of Lithium batteries I would use that one.
Wow, that's a lot to unpack, thanks for the free Fireworks...

Tad confused around the max from battery mfg per 100ah, so since I know I would have 2 100ah batteries, does that mean the battery mfg say to limit to 100amp and you are also saying that if I had 100amp draw I would be within Ford's specification? If so, any idea of Ford specification.

However your recommendation is 60ah DC to DC charger to be well within tolerance of both Battery mfg & Ford?

When you say "disable the Chassis -> Coach battery system contactor so that it does not close when the ignition is on. " Are you talking about that Trombetta solenoid? Maybe someone that has had to disable can explain how difficult that is. I rather not change too much with the electrical. I don't think I have a Smart BMs? If I did, I wouldn't know where to look.

I do know my converter is Progressive Dynamics 45 amps and it is NOT for Lithium. Progressive Dynamics makes one that has Lithium program for $250.

I always thought it was odd that the converter did not also charge the Chassis battery, but I guess I have not had issues with that. It would be even more complicated if my house batteries were Lithium and Chassis AGM.

Does your coach have AGS, if so; do you know what impacts are there? I have a EC-30 that I use all the time. I am hearing those Lithium's stay above 13.6vdc all the time (80%)?
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Old 07-05-2024, 07:14 AM   #4
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dkoldman,

On mine, I simply disabled the BIS by inserting a plug connector on the negative side so I can plug it back together to restore boost function if ever needed. You can use a switch as well as my diagram below shows, but I decided after I drew that not to use a switch, too easy to accidentally get switched on.

I replaced my Trombetta a while back with a Cole Hersee that has a separate ground(neg) terminal so this was easy for me. Your original Trombetta doesn't have a separate ground terminal, it grounds through the mounting bracket so unless it is mounted to a non conductive surface like wood this won't work for you but you can still do it by interuppting the positive side of the Trombetta coil.

The Trombetta has nice long side post terminals as well meaning there is extra room to run your DC-DC charge feed right off the alternator side of the Trombetta as shown in my crude diagram. Everything else can be left as is, and in fact in my case the fat wire that goes to the house bank also brings power from the batteries to the battery switch and from there to the house distribution panels.

You will want some way to disable the DC-DC charge for times when you don't want to keep charging the house, depending on which model you buy there are various differences. My Victron has a provision for installing a shuttoff circuit which I did and I installed a small toggle switch in my battery compartment. When the switch is on, the Victron starts charging a few seconds after the engine starts by using smart sense technology.

I did my installation with custom cables ordered from BatterycablesUSA, I ended up changing a few things for neatness and to make more room on my BIS posts so I ended up ordering 7 cables total. On my charge cable from the BIS to the DC-DC and from the DC-DC to battery I used I use inline MEGA fuseholders with 60 amp MEGA fuses to match my #6 cables and 30 amp DC-DC charger and per Victron's recommendation. I bought them from Mouser, Amazon has a lot of China crap that I don't trust and they only have mountable in-line fuse holders. Using inline fuse holders means I had to have two cables from each location, a short one to fasten to one end of the fuse holder and the other one to reach the destination.

At the battery itself I installed a MRBF with a dual MRBF holder so I can feed a secondary load off the battery. (I only have a single battery)
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Old 07-05-2024, 08:13 AM   #5
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Morning , Sir! See you are still at the mods!
I try not to get involved in the lithium discussion due to little experience with Rv use.
But I can maybe help to point to changes others might propose to the solenoid as used on your Rv.
You have the three post variety of the solenoid but I might lean more toward opening the hot side of the controls wiring to the solenoid, rather than the ground side.
Do you know where taht solenoid is and what effort it may take to get in to it? Behind the breaker panel on the left side? That can be easy or near impossible as on our Vista, so some checking before deciding?

LR brings 12V from ignition hot or boost switch to coil of solenoid through it to ground at mounting screw where they also put FM ground! That closes solenoid contacts to conncet chassi and coach. That is what you DON'T WANT except when wanting a jump start for weak engine start.

Idea is somewhat simple to add a switch and make sure the switch is not changed except when you want it! That might be a simple cover like used for turning off machines while they work on them but many of those "lockout switch" covers are really commercial grade and lots more than you need.
Maybe if you go with a normal AC switch like at home, a childproof cover is good?
https://www.amazon.com/Toggle-ILIVAB...86MIASV99&th=1
Or for a small toggle switch?
https://www.amazon.com/Safety-Red-To...A1VRRJFO1VFP1B

I like the smaller hole, etc. of small togggle.

LR is 12VDC low voltage and low currect, so most any switch will do if not super small like on a circuit board. Any size big enough to fit our finger!!
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Old 07-05-2024, 08:59 AM   #6
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Quote:
Originally Posted by bigb View Post
dkoldman,

On mine, I simply disabled the BIS by inserting a plug connector on the negative side so I can plug it back together to restore boost function if ever needed. You can use a switch as well as my diagram below shows, but I decided after I drew that not to use a switch, too easy to accidentally get switched on.

Based on where my Trombetta is, I would likely need switch to access, your drawing is perfect

I replaced my Trombetta a while back with a Cole Hersee that has a separate ground(neg) terminal so this was easy for me. Your original Trombetta doesn't have a separate ground terminal, it grounds through the mounting bracket so unless it is mounted to a non conductive surface like wood this won't work for you but you can still do it by interuppting the positive side of the Trombetta coil.

I am sorry but I am not familiar with a Cole Hersee. Can I asked why or what gain to replace the Trombetta? I am a minimalist on these types of mods

The Trombetta has nice long side post terminals as well meaning there is extra room to run your DC-DC charge feed right off the alternator side of the Trombetta as shown in my crude diagram. Everything else can be left as is, and in fact in my case the fat wire that goes to the house bank also brings power from the batteries to the battery switch and from there to the house distribution panels.

I will have to come back to this in more detail. It seems like all on this forum are agreeing or saying that I must have a DC to DC charger? I have read and watched videos questioning so I am confused on the need. Randy PowerCat explained it best for me though, so I have to break it up in little pieces. Seems like the DC to DC I would need should 60amp, seems like it is possible to keep my OEM wiring in tact and use switch to activate the use of Aux Emergency switch if ever needed, seem like I may be able to store the DC to DC in compartment next to Trombetta solenoid versus my battery compartment?


You will want some way to disable the DC-DC charge for times when you don't want to keep charging the house, depending on which model you buy there are various differences. My Victron has a provision for installing a shuttoff circuit which I did and I installed a small toggle switch in my battery compartment. When the switch is on, the Victron starts charging a few seconds after the engine starts by using smart sense technology.

This I do not follow, why would I ever want to disable the DC to DC charger given I purchased and installed? Are you saying they can overcharge batteries?

I did my installation with custom cables ordered from BatterycablesUSA, I ended up changing a few things for neatness and to make more room on my BIS posts so I ended up ordering 7 cables total. On my charge cable from the BIS to the DC-DC and from the DC-DC to battery I used I use inline MEGA fuseholders with 60 amp MEGA fuses to match my #6 cables and 30 amp DC-DC charger and per Victron's recommendation. I bought them from Mouser, Amazon has a lot of China crap that I don't trust and they only have mountable in-line fuse holders. Using inline fuse holders means I had to have two cables from each location, a short one to fasten to one end of the fuse holder and the other one to reach the destination.

Duly noted on battery cable source.

At the battery itself I installed a MRBF with a dual MRBF holder so I can feed a secondary load off the battery. (I only have a single battery)
My plan is to have two Group Size 31 at 100ah or the maximum number of AHs possible that will fit into my existing battery compartment under the stairs, I do have space under a dinette bench next to steps if I had to had expand or store elsewhere.

Not sure I follow the need or intent of a secondary load?
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Old 07-05-2024, 09:09 AM   #7
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DK, I wanted to answer your initial questions.

There are a contingent of folks that say they believe that the Converter doesn't need to be Lithium capable because the standard FLA charge profile is "close enough." I think those folks are in the minority and they may have other reasons for thinking that it true. Some just don't want to spend any more money on their electrical system and feel that changing the converter is too expensive.

Many of them have solar on their roof and feel that the solar charge controller makes up the difference between the Converter's inadequate charge and the Solar Charge Controllers proper LFP charge profile.

Personally, I'd want to update my Converter to get one that has both higher output and a proper charge profile. Yes, the old Converter does OK, but generally they don't have a very high amperage output nor do they reach the correct final voltage and they apply the float phase differently. None of that is ideal or even "good enough" for what LFP batteries need.

You can decide for yourself.

Do you need a DC2DC charger? Well, that depends, too. You have said you want to disconnect the alternator charging from the new LFP batteries. So, if that's the case then you really do need solar on your roof or a DC2DC charger.

Many replace that Trombetta solenoid with a LI-BIM. This isn't perfect either but by all accounts works well enough to charge LFP batteries while driving. It preserves all the functions of your OEM alternator charging, including chassis battery charging, house battery charging and Aux emergency battery combining. It protects the alternator by using a timing function to prevent the LFP batteries from demanding so much current over such a long time by connecting then disconnecting the alternator to the house batteries while driving.

If you disconnect the alternator from the LFP batteries you will need something to charge your batteries while driving. This assumes you've been somewhere that you used up a portion of your house battery's storage capacity at one location and then are driving to a new location at which you'll want to arrive with your house batteries recharged as much as possible.

This is where a DC2DC charger is necessary in the system. This auxillary charger has a dedicated LFP charging profile and takes pretty much any 12v output and modifies it for LFP charging.

Solar, which you say you're not interested in, also plays a role in this because, assuming you are driving to your new location during the daytime could be using solar power to charge those LFP batteries if you did not install a DC2DC charger to make up for lack of alternator charging.

I would encourage you to modify your plans and add at least a small amount of solar charging to your plans. There is no need to put a solar power station on your roof. Just 200-300w will go a long way in charging your new batteries every day. And, you'll likely appreciate the difference that can make to your system.

I have disconnected my alternator charging at the BIM that my motorhome came with. So, I installed a DC2DC charger (Victron Orian 30-amp) and I have 300w of solar on my roof. The 400ah of LFP batteries do a remarkable job of powering things, including my residential 110v fridge that only runs off of my inverter and even my microwave, the coffee maker, etc. We've made no attempt to power A/C with inverted power.

The 300w of solar I have does such a good job of charging those batteries while driving that the DC2DC charger really doesn't play all that much of a role. I kind of which I had installed the Li-BIM and skipped the whole DC2DC charger thing because I had to make up for a loss of chassis battery charging while on shore power from my OEM BIM and I lost the Aux Battery Combining function entirely when I disconnected my BIM.

I hope this helps answer some of your questions about these issues. The most important part is making the change to LFP batteries. They truly are a game changer.
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Old 07-05-2024, 09:17 AM   #8
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You will want some way to disable the DC-DC charge for times when you don't want to keep charging the house, depending on which model you buy there are various differences.
I don't understand this at all. The Victron is "auto sensing" it turns on when you start your motor and it senses alternator charging. It turns off when you turn off the motor... automatically.

Also, it's a smart Lithium charger and so even when driving is more than smart enough to lower it's current as the LFP batteries need less and less charging.

Why do you want to manually turn your Victron DC2DC charger off? Ever?

Also, I find the 30 amp Victron more than enough to rapidly charge my batteries. Though I do have 300w of solar to augment that charger when driving.
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Old 07-05-2024, 09:24 AM   #9
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Originally Posted by Morich View Post
Morning , Sir! See you are still at the mods!
I try not to get involved in the lithium discussion due to little experience with Rv use.
But I can maybe help to point to changes others might propose to the solenoid as used on your Rv.
You have the three post variety of the solenoid but I might lean more toward opening the hot side of the controls wiring to the solenoid, rather than the ground side.
Do you know where taht solenoid is and what effort it may take to get in to it? Behind the breaker panel on the left side? That can be easy or near impossible as on our Vista, so some checking before deciding?

LR brings 12V from ignition hot or boost switch to coil of solenoid through it to ground at mounting screw where they also put FM ground! That closes solenoid contacts to conncet chassi and coach. That is what you DON'T WANT except when wanting a jump start for weak engine start.

Idea is somewhat simple to add a switch and make sure the switch is not changed except when you want it! That might be a simple cover like used for turning off machines while they work on them but many of those "lockout switch" covers are really commercial grade and lots more than you need.
Maybe if you go with a normal AC switch like at home, a childproof cover is good?
https://www.amazon.com/Toggle-ILIVAB...86MIASV99&th=1
Or for a small toggle switch?
https://www.amazon.com/Safety-Red-To...A1VRRJFO1VFP1B

I like the smaller hole, etc. of small togggle.

LR is 12VDC low voltage and low currect, so most any switch will do if not super small like on a circuit board. Any size big enough to fit our finger!!
Hello Morich, it has been a while. We have been on cruise control and everything was just fine and I could not be more happier with our coach. But life happens, this is elevator speech of how I got to this mod.

Returning home from 8 hour Memorial day weekend trip we had a blowout on right inside dually tire on 635 LBJ 20 minutes from home. TPMS gave no warning. It took out the entire compartment behind the dually, I lost all of the contents about $500, then the wall in front of the dually was banged so hard the inside bowed in, I later learned the impact destroyed the inside of the Magnum Dimensions csw1012 Inverter, it too list for about $500. Insurance claim would have been $2,500 and I have zero $ deductible, but I decided to pay out of pocket and fix my self without a claim. My guess is I may spend $1,200 but I am still working on it.

In the process at looking at Inverters I am gambling on a 2200 watt unit that has out of this worked display. I have purchased a 2nd remote that is wireless and portable. In the process I stumble across these 100ah Lithium batteries for $160. My current AGMs are 3.25 years old, so they are okay but not new anymore. So while trying to cost this out to convert to Lithiums, I start to learn that you really don't need a special converter algorithm, and some have been using DC to DC chargers with no issues to alternator for years.

FWIW, I am not a Lithium guy per se, I just want the most possible AHs possible per a Group 31 battery footprint. Today it happens to be vMax Tanks SLR125 ( 62.5 usable) so if the 100AH Lithium has 90 usable, I am in business to see what is minimal to convert over.

Attached is picture of my actual Trombetta. It is behind an electrical panel on Driver side opposite of the batteries. A few years ago I took this picture as that is where I found a loose wire that was feeding my Kwikiee steps causing all kinds of issues.

Your switch mod may be something I could pursue now as it would be independent if I had Lithiums or not. I could just get it out of the way. Similar goes to the new converter. The newer one will allow me to use AGM or Lithium.

Then I am left with this DC to DC charger thing. If it can go driver side that may be convenient and a cleaner environment. It could also go inside under a dinette bench.

I have lots to learn so I am still processing all of the information.
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Old 07-05-2024, 10:29 AM   #10
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Yes, always more ot learn, it seems !
One minor may be that term, " Trombetta" as that seems to be a brand of solenoid and It looks more like you have a Cole-Hershey ! Main difference seems to be the shape and materials used when I look at the two. The one you have with shiny metal body and two ears/lugs on each side comes in two types. Two big lugs, usually wired chassis left and coach right with the small wires for control. The three wire version has the small hot wire in a center lug and uses internal connections to use the mounting screw or bolt as ground, while the four post version also has a small lug for a ground wire FM as well as the small LR.
Some RV have the three lug and only one small LR wire, no ground wire FM but just use the mounting as ground. Those tend to lose ground connection if the screw gets loose.
That makes your RV with both LR and FM being a bit more reliable as it gets ground from FM but also the mounting screw. Belt and suspenders?

Trombetta is wired much the same but black bakelight is what I think I see. You can get discussion of which is better but both tend to last so long, that I'm not inclined to try to mount a different type on a $20-30 item that lasts around 15-20 years!
I'm a cynical optimistic guy? I tend to think if it is going to last 15 years, I'm likely out of here anyway!
https://www.google.com/search?q=Trom...hrome&ie=UTF-8
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Old 07-05-2024, 10:32 AM   #11
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DK, see my replies to your questions (in bold) below


I am sorry but I am not familiar with a Cole Hersee. Can I asked why or what gain to replace the Trombetta? I am a minimalist on these types of mods

The only reason I ended up with the Cole Hersee is because my Trombetta failed and the Cole Hersee seems to be the most popular replacement and it has much a higher continuous rating than the Trombetta, at 200 amps, as well as silver tungsten contacts. At the time I still had lead acid.

I will have to come back to this in more detail. It seems like all on this forum are agreeing or saying that I must have a DC to DC charger? I have read and watched videos questioning so I am confused on the need. Randy PowerCat explained it best for me though, so I have to break it up in little pieces. Seems like the DC to DC I would need should 60amp, seems like it is possible to keep my OEM wiring in tact and use switch to activate the use of Aux Emergency switch if ever needed, seem like I may be able to store the DC to DC in compartment next to Trombetta solenoid versus my battery compartment?

I can't say if you need a DC to DC charger, many go without. The length and thickness of your charge wire will somewhat limit the charge current from your alternator, which can be good in that it will protect your alternator but at the same time on a long run your LiFeP04 may not get enough. I could have probably got away without it since I have a 220 amp alternator and a 14 foot feed of #1 AWG. Mercedes used to say to limit auxiliary loads to 40 amps but they revised that to 80 amps (with the 220 amp alternator). I just decided to install one so there would be no chance of overheating my alternator.
Also it is recommended to put the DC-DC charger close to the batteries and I had plenty of room so I stuck it right inside the battery compartment. Generally it is accepted that you need at least one method of fully recharging your LiFeP04 once in a while to assure cell balancing, you can even use a lithium compatible charger for this. My converter can't do it because my wire run is too long/small.

This I do not follow, why would I ever want to disable the DC to DC charger given I purchased and installed? Are you saying they can overcharge batteries?

Most manufacturers of LiFeP04 recommend storing at a less than 100% charge, mine recommends storing at 50%. If we are heading home and know we will be storing for awhile I want to be able to stop charging and start to deplete down to that 50%. During storage, if I drive the rig somewhere or even just take it out for exercise I don't want to charge the battery back up and then have to deplete it when I get home. For example about 6 weeks ago we used the MH for a 60 mile round trip because we had an errand in the next town, and I was concerned about the MH since it had been sitting since the end of September so I thought I'd kill 2 birds with 1 stone. Without the kill switch, we would have arrived back home with a fully charged battery that would have needed depletion for storage.


Not sure I follow the need or intent of a secondary load?

My secondary load is my 12 volt absorption fridge which I wired directly to the battery with #8 AWG and improved the heating element output by 35%. It had been wired from the factory with a very long run of #12 and when the fridge was running on 12V I was only getting 11.2 volts at the element with the engine running. I now get 13.3V and 44 more watts.
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Old 07-05-2024, 10:44 AM   #12
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Thinking of the most simple,least effort/expense way to do a switch and this might fit for that?
See that yellow wire going to the small lug on your solenoid. that whole part of the RV can have several names. Newest is solid state and often called Battery Isolation Manager (BIM). I think that may be the same as BIS for battery isolation system? Different name from different RV builders, maybe?
But you have a bit older which has good and bad points. The mechanical contacts can arc and corrode to fail sooner than we like but they are easier to hear and feel to see if they are working!
Solid state is maybe more reliable with no contacts but they are expensive and if they fail it is not something you can feel or hear, so may more difficult for us folks who don't do it all the time?

But if there is slack in that small yellow wire, a really simple idea for switch might be to cut that wire, put a small jack through the wall and then add a plug to the wire to fit the jack. Insulate or cap the wire from the front to keep it out of trouble but when you dID want to power the solenoid, jus plug the wire plug into the jack to restore the connection. That makes the boost or the charge as we drive both work until you pull that plug! Something smll like a headphone jack that only needs a really small hole to mount?
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Old 07-05-2024, 10:53 AM   #13
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Originally Posted by creativepart View Post
DK, I wanted to answer your initial questions.

There are a contingent of folks that say they believe that the Converter doesn't need to be Lithium capable because the standard FLA charge profile is "close enough." I think those folks are in the minority and they may have other reasons for thinking that it true. Some just don't want to spend any more money on their electrical system and feel that changing the converter is too expensive.

This is what I am slowly learning. 4 years ago when I first considered Lithium before buying the AGM VMax Tanks it was $4,000 to go to Lithium so I just spent $500 and called it a day. My AGM are still okay, but I fell into this rathole because given I buying brand new 2200 watt inverter and have just added the Microwave as option to plug into the Inverter circuit, I started seeing the $160 Lithium batteries with BMS and Phone app, low temp cut off etc. So my plight now is 2 100ah Lithium to increase my total available AH Capacity.

Many of them have solar on their roof and feel that the solar charge controller makes up the difference between the Converter's inadequate charge and the Solar Charge Controllers proper LFP charge profile.

Personally, I'd want to update my Converter to get one that has both higher output and a proper charge profile. Yes, the old Converter does OK, but generally they don't have a very high amperage output nor do they reach the correct final voltage and they apply the float phase differently. None of that is ideal or even "good enough" for what LFP batteries need.

You can decide for yourself.

I can do the Progressive Dynamics Converter upgrade myself for about $250. I have not looked at other Converter options and I prolly should. My existing converter is 5 years old, so if I can find something that does it all and include some type of display to access and control, that may be worthwhile upgrade to make anyway.

Do you need a DC2DC charger? Well, that depends, too. You have said you want to disconnect the alternator charging from the new LFP batteries. So, if that's the case then you really do need solar on your roof or a DC2DC charger.

I may have confused. Remember I am just now learning this so I may parrot something I am told. It is not that I want to disconnect from the LFP batteries as the goal, I was told that I had to have DC to DC charger, and so once I had that; I needed to disconnect alternator from charging. I believe what I really want to do is not damage the alternator. The least expensive and less invasive path to do that is what I seek. Now I would like to keep my function to Aux / Emergency Start.

Many replace that Trombetta solenoid with a LI-BIM. This isn't perfect either but by all accounts works well enough to charge LFP batteries while driving. It preserves all the functions of your OEM alternator charging, including chassis battery charging, house battery charging and Aux emergency battery combining. It protects the alternator by using a timing function to prevent the LFP batteries from demanding so much current over such a long time by connecting then disconnecting the alternator to the house batteries while driving.

This sounds simpler and if cost is okay it may be closer to what I would have hoped if a DC to DC was not required. May be tricky for me with the wiring unless that relay o Isolator thing next to it stays in place?

If you disconnect the alternator from the LFP batteries you will need something to charge your batteries while driving. This assumes you've been somewhere that you used up a portion of your house battery's storage capacity at one location and then are driving to a new location at which you'll want to arrive with your house batteries recharged as much as possible

Yes, I never intended to suggest I would not have some charging while driving. We drive with our Absorption Fridge on inverter ON all the time as a rule. The Switch I was looking at was to turn the alternator off while the DC to DC charger was on, but in the event of emergency I could flip the switch to use the Aux/Start button.

This is where a DC2DC charger is necessary in the system. This auxillary charger has a dedicated LFP charging profile and takes pretty much any 12v output and modifies it for LFP charging.

Solar, which you say you're not interested in, also plays a role in this because, assuming you are driving to your new location during the daytime could be using solar power to charge those LFP batteries if you did not install a DC2DC charger to make up for lack of alternator charging.

I would never NOt have some form of charging. It will always be the Alternator unless I get advised to go the DC to DC route. If I do go DC to DC, I would then want option to turn On/Off Alternator charging.

Yes I have no desire or need for Solar in our application. If I turn off my disconnect switches I can go months and engine starts up fine. I did once had a yank after a long period and it was very cold outside and I did the Aux / Start button and it started right up, that was 3 yeas ago. My battery is 6 years old.

I would encourage you to modify your plans and add at least a small amount of solar charging to your plans. There is no need to put a solar power station on your roof. Just 200-300w will go a long way in charging your new batteries every day. And, you'll likely appreciate the difference that can make to your system.

If I ever did any type of Solar it would be with a portable panel. I use to say my next RV may have Solar but not sure I will ever have a next one. They cost so much and we love ours. Keep in mind I believe in concept... quality is fitness for use. My 2 AGM fullfilled all of our power needs. I just see an opportunity to get more AHs in the same space and for less money than the AGMs except for the modifications required. But who knows the future, if I ever get sound with Lithium Solar may come because I simply have no other mods to do.

I have disconnected my alternator charging at the BIM that my motorhome came with. So, I installed a DC2DC charger (Victron Orian 30-amp) and I have 300w of solar on my roof. The 400ah of LFP batteries do a remarkable job of powering things, including my residential 110v fridge that only runs off of my inverter and even my microwave, the coffee maker, etc. We've made no attempt to power A/C with inverted power.

Our unit was wired on 15amp AC circuit for our 1000 watt Inverter. I ran a receptacle from that circuit and plugged the inside Fridge that line. We have run 3 1/2 years that way with no issues. I switch to Propane when we stop so the Fridge is off the inverter. We have new 2200 watt inverter on order. I intend to use it the same way with one exception; if I need to run the microwave I now have a 2nd receptacle for it side by side the OEM to temporarily plug into. The new inverter if it proves itself has a lot of information on the display so you can see DC IN, AC Out, & Power Consumption. I am upgrading the Fuse from 150CNN to 250ANN/CNN.

The 300w of solar I have does such a good job of charging those batteries while driving that the DC2DC charger really doesn't play all that much of a role. I kind of which I had installed the Li-BIM and skipped the whole DC2DC charger thing because I had to make up for a loss of chassis battery charging while on shore power from my OEM BIM and I lost the Aux Battery Combining function entirely when I disconnected my BIM.

I don't think our OEM Trombetta charges the chassis battery from factory? I need to check, I may be wrong. But you are pushing me to this Li-BIM thing. I need to see one and see what is involved with it's install. Less parts is my preference.

I hope this helps answer some of your questions about these issues. The most important part is making the change to LFP batteries. They truly are a game changer.
Wow, this is so much information, I tried to keep up

Basically the way I view this is I have $600 set aside to buy new AGMs in future. If I can buy new LFP now for $320 and maybe $400 - $500 on modifications, I may have something going.

Based on your input it could look like this

$320 Two LFP 100ah batteries
$250 Progressive Dynamics 45amp Converter
$200 ? TBD for this LI -BIM thing you are talking about
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Old 07-05-2024, 10:58 AM   #14
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Originally Posted by creativepart View Post
I don't understand this at all. The Victron is "auto sensing" it turns on when you start your motor and it senses alternator charging. It turns off when you turn off the motor... automatically.

Also, it's a smart Lithium charger and so even when driving is more than smart enough to lower it's current as the LFP batteries need less and less charging.

Why do you want to manually turn your Victron DC2DC charger off? Ever?

Also, I find the 30 amp Victron more than enough to rapidly charge my batteries. Though I do have 300w of solar to augment that charger when driving.
See my reply to DK's same query. I also have the Victron 30 amp Orion and you can disable it with the jumper but it's hard to reach the bottom of mine in the battery compartment, thus the switch.
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Old 07-05-2024, 12:06 PM   #15
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The Li-Bim is a battery isolation manager that, like your Trombetta connects the alternator to both the house batteries and the chassis battery when your motor is running. Not all OEM setups charge the chassis battery when on shore power but the Li-BIM does. It also connects house and chassis batteries when you push the momentary Aux Battery button at the dashboard for "emergency" starting power.

It costs about $140. Here's an Amazon link:
https://www.amazon.com/Battle-Born-B.../dp/B07DY8S815

Here's a video on installing the Li-BIM in the place of a trombetta but it looks different than yours:
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Old 07-05-2024, 01:57 PM   #16
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Originally Posted by creativepart View Post
The Li-Bim is a battery isolation manager that, like your Trombetta connects the alternator to both the house batteries and the chassis battery when your motor is running. Not all OEM setups charge the chassis battery when on shore power but the Li-BIM does. It also connects house and chassis batteries when you push the momentary Aux Battery button at the dashboard for "emergency" starting power.

It costs about $140. Here's an Amazon link:
https://www.amazon.com/Battle-Born-B.../dp/B07DY8S815
I am doing my homework. I noticed that the LI-BIM 225 is made by Precision Circuits who I believe make the EMS installed by WBGO

I found this but still have a few questions, but they are closed today.

https://www.precisioncircuitsinc.com...i-BIM-Rev1.pdf

Currently, I never level run my hydraulics or let slide out unless the engine is running. At that time all batteries are not only charged but max voltage. With the BIM 225 what happens when I pull up wish to level or let jacks out but the LI-BIM 225 is resting the alternator? Do I have wait up to 2o minutes

It is also not clear to me if you have to have two dedicated wires one for Ignition and the other for the boost? I think I may only have one wire at the Trombetta, so it could be active both ways Ignition on and/or boost switch depressed? Maybe the LI-BIM is smart enough to read that wire and the voltage?

I find it interesting you have a DC to DC but recommend this solution. You are the 2nd person I know thus far that has indicated the same.
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Old 07-05-2024, 02:07 PM   #17
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LR brings 12V from ignition hot or boost switch to coil of solenoid through it to ground at mounting screw where they also put FM ground! That closes solenoid contacts to conncet chassi and coach. That is what you DON'T WANT except when wanting a jump start for weak engine start.
Are you confirming that LR (see blow up picture of my actual unit) is hot when ignition is ON or Boost Switch is pressed?

I asked because look at the LI-BIM 225 wiring. It seems to have posts for Ignition and Boost separate?

Maybe the LI-BIM is reading both the Ignition post and the voltage to know when to Close or Keep Open?
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Old 07-05-2024, 02:44 PM   #18
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Yes, confirming that the LR brings 12v from either of two places! One is the boost switch and the other is an "ignition hot" point. That second is as name implies hot when ignition is on.

But I also should correct what I was saying on the brand as I was wrong in what I had learned about the Trombeta! I see the brand peeking out and you do have Trombetta and I had always seen them as black bakelight. So that blows my idea of telling what we are looking at from appearance!

But some details bring questions??
Does the wiring need to be directly on batteries to sense voltage that much better or is connecting to the coach battery cable already connected direct to battery and run to solenid all okay?
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Old 07-05-2024, 04:07 PM   #19
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Yes, confirming that the LR brings 12v from either of two places! One is the boost switch and the other is an "ignition hot" point. That second is as name implies hot when ignition is on.

But I also should correct what I was saying on the brand as I was wrong in what I had learned about the Trombeta! I see the brand peeking out and you do have Trombetta and I had always seen them as black bakelight. So that blows my idea of telling what we are looking at from appearance!

But some details bring questions??
Does the wiring need to be directly on batteries to sense voltage that much better or is connecting to the coach battery cable already connected direct to battery and run to solenid all okay?
Attachment 189336
I watched a video of install that CreativePart had sent.

I feel pretty good about taking the positive cables from the Trombetta solenoid Chassis & house battery to connect to LI-BIM 225. I also feel good about the Ground and LR connecting to post on LI-BIM 225 marked IGN, what I am still confused about is SIG? I am not sure I have SIG wire? in the video they had a second wire to go on SIG post but it was the Boost wire. Since in that compartment I only have LR that is hot when ignition is ON and / or AUX/Start pressed, I may not have anything for the post marked SIG?

Also, is the AUX/START button irrelevant with Lithiums on House? Not sure 200ah Lithium can start the F-53 engine?
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Old 07-05-2024, 05:29 PM   #20
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Yes, I have much the same questions on the SIG wire and what it does versus what the IGN wire does? It will likely need a call or talk to somebody who knows what they put in side their product!
Part of it is something I've never looked at and may not be available. Do other RV besides Winnebago use something similiar to what we have on solenoid, BIM, etc?
My thought is that other RV may have a different setup for charging the coach while driving and what we find may not have been what they were working with in their design thinking!
But that is where I tend to have alove /hate thing with solid state! I grew up with the old stuff like points and plugs on cars. they gave a ton of trouble but when they stopped working right, you could use a fingernail file and may the points work again.
Now if I had trouble with my car, I would have little choice but to take it to a shop where they hook it to a machine to find what to do!

On the batteries, do they come with any kind of cold cranking amps (CCA) rating? That is what I use to judge how much instant power we can get, where the amp hours is more how mcuh total between full and discharged.
And that also gets back to the new gizmo being discussed! When you have the current solenoid, there are big contacts that can carry lots of current from the coach to start the RV. But what is in the new and how much current at one time can it pass?
Any engineers for the company that like to explain things???
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