LiFePO4 DC-DC Charger Wiring and Battery Boost

[7997redtail]

I think I've looked at enough posts and electrical drawings to choke an elephant. That doesn't really make any sense but I'm shaking my head trying to figure this out.

I'm switching to LIPO4 lithium batteries and I'm trying to figure out the best way to hook in the DC-DC charger/alternator protector.

One technique that I've found so far is to disable the solenoid as per the image below. Credit to bigbAZ on IRV2 for it. But I'm not to sure why you wouldn't leave the solenoid working and charging as it sits. I do note that there is the battery boost feature although I'm not to sure why that needs to be disabled.

The second part of the confusion is my understanding that the chassis battery is being charged from the alternator all the time. My chassis battery is right beside my house battery. Why can't I take a wire from the positive of the chassis battery and use that to supply the DC-DC? Im thinking there must be some kind of problem when starting. Maybe a reverse draw on the DC-DC? I could put a solenoid in this line to be off when starting.

I've included a partially completed drawing of what I have. My RV is old enough that I didn't have a BIM module, the batteries are controlled from the two disconnect relays. Could someone finish the drawing of for me?

I've used black and silver to identify the two relays. This has been mentioned as a way to identify them in similar posts about LIPO4.

I should be able to wrap my brain around this but there is just so many posts out there and none have been able to clear this up for me.

Thanks in advance.

 

[Morich]

Not sure I can answer all the question but there is one part that I can throw some light on and might work it a bit less complex to figure. But let me starty with saying there are many, many different ways to work this question, so there may not be any one totaly "right" way, just different things to consider.
I start with wanting to know what exactly each RV has as built and lacking that, some of this may need tweaking if your RV is radically different than the one I looked at earlier today?
Big thought on how and why to disable the automatic connection between coach and chassis/start battery groups?
This is a common one to talk generic ideas? This is an older version which used a "mode solenoid" whihc is just more mechanical closing contacts. Thsoe are replaced by "battery isolation manager" (BIM) on later solid state designs.

Both work much the same but one move contacts which tend to burn and the other has solid state that does the job without contacts (magic?) !!
What we get are three wire or four wire solenoids with the latter using an added ground to make it more reliable than older using the mounting screw for grounding. If the ground screw got loose, you lost the function that connected them together.
But main idea is that the FM wire is ground or it comes from the mopunting screw. Power comes from two places in the RV front on wire LR. When we start the RV engine, LR gets 12v and goes down to the coild in the solenoid to close the contacts connecting coach and chassis cables on each side of the solenoid. That is first use that lets us put some charge back into a run down coach bettery as we drive to the next siote! If we drive far enough and long enough we camp the next night with a fully charged caoch battery!
Second soleniod function is knd of the opposite as we have a place normally somewhere close to the driver to put a switch called "boost, aux" or other" when we have let the start battery go too low and we need a "jump start"! We push that switch and hold it to connect coach to start and while we crank the engine to start. Jump start without getting cables or a second car? Two functions from one solenoid setup, but that can be the problem if we have two types of batteries and don't want them connected all the time the engine runs!
One way to deal with this and still preserve some of the good function without the bad is semi-simple.
The idea is we may want to keep the jump start idea but not have it all the time to overheat anything! Okay to connect the 14-15 voltage coach to the run down start battery, but just not full time, so we add a switch in wire LR and put it where it stays off until we WANT it on! Lots of choices on where and how to put the switch in as it carries very little power so small wires work well as well most any type of small push or toggle switch. The main point is to make sure it stays off until we want it on, so hiding it out of the way or getting one with a cover to avoid flipping on when not wanted! I suggest adding it in the hot side of the coil circuit as there are some solenoids with only three wires that get ground from the mounting, not a second wire.
Possibly my brain is just more used to switching the hot side?
But that is where we first need to know what we have before planning what to do with it!
Not sure I follow what you are showing on your drawing but some guesses may help. I see silver and black and I think you mean the silver color of the "can looking" mode solenoid and the black is the battery disconnect relay? I don't think of the disconnect relay as too involved in this part of the operation as it only acts to cut off some of the power that is fed to the coach through this relay. Safety items go around this relay and stay hot no matter what the disconnect is set to do.
Think of that black item as a switch. What comes in on the left side big cable has to go through contacts inside to go out the right where wire labeled KKF feeds to the coach! But things connect on the left where power comes in, DO NOT go through contacts and stay hot!
To help sort what YOUR RV should have, this is the set of wiring drawings:

Wiring Diagrams

Look to "chassis electrical box section for this part of the drawings that shows the solenoid!
Down in lower left is a link to ID which is stamped on the smaller WInnebago wires.
This chart is the ID "decoder" list!

https://www.winnebago.com/files/files/winnebago/resources/diagram/electrical_guide.pdf

Find a wire and look at the last few letters in a long strign for the 1-3 letters of ID, then find the locations that wire goes from and to! Big help when needing to know where to find power or ground connections or jsut where the other end of a specific wire might be found!
Winn does a good job of showing the parts pretty much like they look, so the silver is pretty much like it looks as well as the black should be on the right side of it as we look in to find it! Silver left, black bakelite item on right?

Maybe that gives a start on sorting the idea? Good to gather the info before starting as a way to plan it better without mistakes!

Point to keep in mind? What good would a forum be if there were no questions, so ask away when/if confused as most of us get there at some point!

 

[7997redtail]

Very thorough as always Morich.

This answers the charging/boost solenoid wiring (and the wiring coding. I carry a hard copy of the decoder with my repair kit but hadb forgotten about it).

I'm going to contact renology and ask why the DC-DC can't be in the line going to the house batteries (call it house battery charge HBC) from the solenoid. My guess is that the DC-DC doesn't allow reverse passage of current.

I'm thinking the best solution is to parrellel HBC in a convenient location then put a solid in line. Control it to close

 

[7997redtail]

Odd, it looks like what I started but didn't finish got posted. Not too sure what happened but I'm going to start over.

Very thorough as always Morich. Thanks

This answers the charging/boost solenoid wiring (and the wiring coding. I carry a hard copy of the decoder with my repair kit but had forgotten about it).

On my drawing I have the two solenoids misspelled. The silver should be in the left.

I'm in a very bad location for Internet access so downloading is slow. I'm going to try and look up how and where alternator power gets to the chassis battery (C.

And, while I have the brain trust reading looking into this has brought up some more questions. Like:

When the RV is started, the alternator must be supplying charge power to the positive side of the chassis battery. Why can't I hook the DC-DC directly onto that line. I think it would be the same as running a new cable directly from the alternator. True?

On the battery disconnect relay it shows a dashed line (I think that is a larger battery power size conductor) going to the generator. Ive always thought the generator was only connected into the system by supply 110vac to the shore/generator power plug. That 110vac then supply's the house charger to charge the house batteries. If I'm right what does the dashed line do?

 

[7997redtail]

OMG, I just realized I was having a brain fart moment. Typical me overthinking the problem.

Disconnecting the boost solenoid ( the alternator charging of the house batteries while the engine is running) with a switch for emergency use later, is done because the lipo4 will kill the alternator. We know this.

Once you disabled the charging through the solenoid you can take an alternator source directly from the positive of the chassis battery to the DC-DC.

The advantage of switching the solenoid, over disconnecting the red wire at the house batteries, is you still have the option to use the boost option from your house system.

I really find it hard to believe I missed whatever it was.

However, I'm still interested in the big red wire from the battery disconnect solenoid to the generator question.

 

[Morich]

Maywe missing point is that connection mentioned is to feed 12Volt power to the generator starter! Yes, then when the generator is running to put out AC, that ACpower goes to the converter which "makes" 12VDC for the battery and if the disconnect is closed, it also runs those 12VDC things in the RV!
So we kind of have a big circle going on in a way!

The left side of the red line I drew is a big battery cable likel we expect battery cables. Itis a two way path as it carries power from the RV alternator to the coach batteries when the RV engine is running. But it also carries power from the coach batteries back to that connection where it meets a short second red battery cable going to the disconnect relay. If that relay is closed, thoe power goes through the contacts to the right side big post. On that post power can go to the generator starter. Also there are wires to take power to the other coach 12v fuses for lights, fans and water pump! Wire KKF does that and is a smaller wire! But real important wire because it powers the coach fuse panel!
But if that relay is open, no power goes to fuse panel for much of the coach and also no power goes to generator starter! I think this is also a big red battery cable that you can find on the generator!
The big circle idea is we send 12VDC to the starter from the coach batteries, the engine starts and if we have the cord from the generator plugged in at the outlet we get 110AC from the generator going inside tot he converter that makes the 12VDC to charge the batteries we used to start the generator! That lets us use as mucvh coach batttery as we want as the generator charges them and also keeps the lights on!

One thingthat can mess with our mind is the way we can get into thinking of the batteries as going in one side and out the other? It make make more sense to think of batteries as a "pantry" where we store extra food/power!
Some days we bring food home and store it in the pantry and maybe the next day we take some out. In the RV we can put stuff in the pantry by suing the power cord plugged in to either shore power or the genrerator as they both make 12VDc to use or put extra back in the pantry! Like the pantry, we have several different ways to get stuff put in as well as difffereant ways to take it out to use?
So a way to test this info on the disconnect cutting power to start the generator is simple. Close the disconnect and see that the generator will crank, then open the disconnect and I'm pretty sure it will NOT crank. But the disconnect switch and relay only open the side sending power to the starter and controls the generator. Only changes what come out of the generator because it won't start!

 

[7997redtail]

Interesting. I can see why a BIM came into use. I'm guessing if the BIM was controlled with a raspberry pi or arduino out something similar to a small computer, the inputs and output would be easily controlled.

I might make that a rainy day Internet search.

Thanks again for your help Morich.

 

[Morich]

Lots of small points on each RV that do make getting any plan we find work ---or not!
One big one that I spot on the drawing from your post one above is that sort of thing. That drawings shows a different model solenoid that has four posts, while the drawing for your RV as built shows a three post desing and they do come in both types. It is also true that the solenoid may get changed over theyears as they do take a beating that makes the contacts open and close way tooften and while they are passing current. That leads to far more arcing than is good for contacts and solenoid fail pretty often compared to the later solid state items. Say we might have a bunch of lights and the vent fan on, maybe a water pump running and then stop or start the RV engine? A fair amount of that current may be going through the solenoid contacts to arc when they are almost open or closed. It can be almost like a shot of lightning that burns a spot on the contacts!
But a part of the drawing that may make a definite difference is the ground! If as your drawing, the solenoid ground shown will not be an actual wire but it reaches ground through the metal case being bolted or screwed to the metal of the chassis. When they switched to using four wire types, the ground wire is still connected to the mounting screws. That would make fitting the switch in way hard!
A small point that they give us on battery cable ID, "may" still be there if you find tape wrapped on the cable, it may fit this ID chart?

Or did the cable get changed and no tape added?

 

[7997redtail]

And the information keeps coming . This is partly why I was pulling my hair out reading all the info I could find. All the different versions of stuff used on RVs. Three wire, four wire.... And it goes on. Anyways, the final answer.

I'm not to sure yet wether my relay is grounded through the case or by wire yet. Either way, a switch on the positive or negative side will work.

So for the next guy looking for the solution here is my final conclusions.

In the drawing attached, solution #1, the one I'm going to use, is what you see in a lot of answers to my original post.

Solution #1
Put a switch either in FM or LR. Either of these stop the relay from closing and providing alternator positive power to the house batteries (H. When you need to use the Boost feature you would need to close the switch. Important. Once the engine is running you need to open this switch. Otherwise you'll be charging the LIPO4 with the alternator. I don't think you need to run quickly to do this. A short charging period isn't going to hurt the alternator.

Solution#2
Put a battery disconnect switch in the line from the relay to the HB. This switch is much more expensive but if you already have one..... This solution also includes just disconnecting and same cable at the HB and safely taping it off. If you want to use the Boost feature reconnect the battery just by flip the switch or reconnect the wire,

A thought on solution #1. I think it would be best to put the switch beside the boost button. I'm going to take a look at what this will entail. Mainly just my time and a little more wire. Odds are I'll put it right beside the solenoid. But I'll check out it first.

One last note. Morichs comment above. The last part explains the solenoid ground and that there are different versions of solenoids out there. And, the battery cable legend. I've never seen this but it will be really helpful is you decide to use solution #2.

 

[Morich]

Small point if you have the three post solenoid as it changes situation one you have. When they used the three post version, it started out without wire FM and only used the ground they got through the mounting screw with no wire FM. I'm sure they found that not reliable as the screw got loose or rusty, so they added wire FM.
But the problem with that part of the plan for where to put the switch comes up because they had ground at the mounting but went double on getting ground there by adding wire FM which also brought ground to the grounding screw! So the big point is that cutting off the ground the wire brings from the dash, still leaves the ground from the mounting!
I suggest redo that part of the planning and plan to switch the Wire LR which brings the power/hot side down from the front!
When you get into working this area, there may be a handy "quickie" idea to save needing a helper to push the button up front. That dash switch puts 12VDC on wire LR to operate it and it is a big relay that we can hear or feel "thump". But if we want to tell if it the relay is moving, we have 12VDC on each of the big lugs at left and right.
That means is we toudch metal like a wire or pliers to either big lug and to small wire LR, we should hear the solenoid thump!
That tells us it moves but not if the big contacts inside are good? If we have a meter to check voltage on left and right, there is usually some small difference in coach and chassis voltages. Then if we put 12VDC on LR, both coach on one side and chassis on the other side should be the same if they are connected! IT can save you some crawling out and in some compartment if you can get in and test without helpers!
My thinking on the switch location is that I rarely will need to use it to get a "jump start" for a weak chassis battery. So my main concern is that it not get left on or turned on accidentally. That means I may want to put it out of reach of any stray fingers that may flip it and ruin my day. If I'm only going to use the switch when I need a jump start, I don't mind putting it way down in some compartment or under a cover to keep it out of trouble?? Keeping in mind it is not used EXCEPT if you let the start battery go dead to need help!
If you REALLY want to cut the work for this switch, go super simple and just hang a small strap with alligator clips to put 12VDC from one of the big solenoid posts to LR---just in case it is ever needed?
But that may depend on how many teens are around to run the radio dead on the chassis battery to need a jump start? Never happened to me!

 

[7997redtail]

All great advice. The solenoid is located front right in a compartment under the passenger area. I think a simple (current rated) switch mounted right beside the relay would be good. The alligator clip or even an insulated male/female connector would be good too.

 

[bigbAZ]

I think I've looked at enough posts and electrical drawings to choke an elephant. That doesn't really make any sense but I'm shaking my head trying to figure this out.

I'm switching to LIPO4 lithium batteries and I'm trying to figure out the best way to hook in the DC-DC charger/alternator protector.

One technique that I've found so far is to disable the solenoid as per the image below. Credit to bigbAZ on IRV2 for it. But I'm not to sure why you wouldn't leave the solenoid working and charging as it sits. I do note that there is the battery boost feature although I'm not to sure why that needs to be disabled.


View attachment 2506606


The second part of the confusion is my understanding that the chassis battery is being charged from the alternator all the time. My chassis battery is right beside my house battery. Why can't I take a wire from the positive of the chassis battery and use that to supply the DC-DC? Im thinking there must be some kind of problem when starting. Maybe a reverse draw on the DC-DC? I could put a solenoid in this line to be off when starting.

I've included a partially completed drawing of what I have. My RV is old enough that I didn't have a BIM module, the batteries are controlled from the two disconnect relays. Could someone finish the drawing of for me?

I've used black and silver to identify the two relays. This has been mentioned as a way to identify them in similar posts about LIPO4.

I should be able to wrap my brain around this but there is just so many posts out there and none have been able to clear this up for me.

Thanks in advance.

It's been awhile since I did that but I believe you can keep the BIS intact if you want. It's basically just a switch. You would just feed the DC-DC charger from the load, or house battery side of the BIS. I think I chose to bypass it for less issues with it failing and possible voltage drop due to running the charge current through an un-necessary part. However I have thought about putting it back into the circuit, it is a newer Cole Hersee 200 amp continuous rated BIS 4 terminal. I would definitely not run the charge current through one of the old Trombetta 3 terminal BIS that Winnebago used, mine was pretty flakey.

One benefit of using it, depending on how you choose to trigger the DC-DC, might be if you use a maintainer on your chassis battery with the DC-DC connected, when your chassis battery voltage rises to the DC-DC trigger point due to the maintainer it will result in unintentional attempted charging of the house. BTDT. If you use the BIS, this can't happen since it won't close without the engine running and the DC-DC will be unable to pull power. I wired my DC-DC trigger to the BIS ignition side to prevent this, when I had it wired to trigger when input voltage came up, my maintainer would repeatedly begin to attempt to charge the house battery but as soon as the 2 batteries connected thru the DC-DC the voltage would drop below the trigger point and the DC-DC would stop, it would do this over and over. Not good. I could have fixed it by putting the BIS back into the circuit but it was easier just to put the trigger wire there.

 

[klook]

I simplified even more. I put the dc-dc as a jumper around the solenoid that connects the batteries via the aux or emergency start or whatever they want to call it, and discontinued the function of said switch. It is not necessary.....I have 514ah of Lithium, I have a battery tender wired into the main chassis battery. I have a NOCO jump pack.....I carry jumper cables that will reach to the Chassis battery.......I got it covered well.
The only thing I am going to add is a remote control switch to shut the flow off to the dc-dc.

 

[7997redtail]

Ahhhhhhh. Could you do a sketch of this? Maybe use my drawing and edit your set up into it. I'm very curious.

Thanks

 

[bigbAZ]

The only thing I am going to add is a remote control switch to shut the flow off to the dc-dc.

Is your DC-DC a Victron?

 

[klook]

It is the only thing that is not Victron. It is a Schumacher.
That may change.....

 

[bigbAZ]

It is the only thing that is not Victron. It is a Schumacher.
That may change.....

With Victron you can just disable it in the app.

 

[7997redtail]

Mine is a renology

 

[7997redtail]

So it's not always what you expect. I put the switch in today. All that's left with that is a couple labels to ID it. But, the wire are not the same as the winn. drawings. I took pictures.

The first is the wiring diagram.

Second is the relay and the post with the LR wire. But with it is a wire that goes to the ground of the reply beside it. I didn't confirm it was actually grounded but it's labeled grd

Third the two wires and labels together. They were actually taped together. I tested the connection and it gets V+ when the battery boost switch is pressed.

The last one is the finished switch. I'll lable what it is and add on ON label.

 

[bigbAZ]

That wire that comes off the positive post and goes to ground contains a flyback diode, see below for explanation from Google AI.