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Old 04-02-2021, 06:43 AM   #1
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Your alternator and Lithium Batteries

I know this video is from Victron and thus it is not unbiased, but I found it interesting in that it described some types of charging that are dangerous for alternators when connected to Lithium batteries. And while the Victron DC-DC charger is mentioned it is not the center of the tests.

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Old 04-02-2021, 07:36 AM   #2
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I have been following this issue for several months in anticipation of someday changing to lithium batteries.

Mercedes says their Sprinters should limit current to auxiliary devices from their alternator to 40 amps. Some have gone as high as 60 amps with no discernable problem.

I have only seen one real world test (it was reported here or on the Thor forum) of a Sprinter and it measured 30 amps going into a 100 Ah lithium battery. A more typical installation would probably have 200 Ahs which wouldn't necessarily double the current (due to increased voltage drop) but it might very well exceed 40 amps. You almost certainly would exceed the 40 amp limit if you have 400 Ahs of lithiums hooked up.

In addition to the DC to DC charger, another somewhat cruder way of limiting the current is to use the Li version of Precision Circuits BIM. It just cycles the current on and off every 15 minutes by switching, not limiting. How well this works to prevent overheating is ????

One disadvantage of using the DC to DC charger is that it is not bidirectional. Current only flows from the chassis alternator to the coach battery, not the other way around. That means that the aux chassis start switch won't work. The DC to DC charger will block any current from the coach batteries to the chassis DC system.

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Old 04-05-2021, 06:54 AM   #3
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It is true that the B to B charger is one direction, but you can wire a bypass wire and switch around the charger. The switch would be normally open and be wired between the battery boost switch and the battery.
Big caution is that most Lithium batteries cannot be used to start the chassis.
I believe only the Lithionics 125 ah are the only ones rated for this.


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Old 04-05-2021, 07:10 AM   #4
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Big caution is that most Lithium batteries cannot be used to start the chassis.
I believe only the Lithionics 125 ah are the only ones rated for this.
Why is that? The Lithium batteries are able to produce very high currents so why can they not be used to start the coach? I am not questioning your statement, only trying to understand what the issue is.

As for Lithionics, if the 125AH battery will work I would think the 315AH battery would work as well. I am told that the Winnebago Ekko will be available at the local dealer late this week or early next week as a demo and perhaps I can find out if the standard Lithionics 320AH battery in that can be used to start the coach. Just curious.
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Old 04-05-2021, 07:34 AM   #5
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AJMike; The Lithionics 125 AH has been designed for engine cranking and is rated for 1,000 amps. I believe that the battle born site states;
"Our battery is designed as a deep cycle storage battery and doesn’t offer the cold cranking amps most applications require for starting".


I would check with Lithionics about the 315 ah. The data sheet states that it has power reserve for engine cranking but does does not indicate the rating.


I installed 2 125 AH with a B to B charger and wired in the bypass so I could use the boost switch. Never tested the boost switch as the chassis battery has never been run down enough.


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Old 04-05-2021, 08:00 AM   #6
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AJMike; The Lithionics 125 AH has been designed for engine cranking and is rated for 1,000 amps. I believe that the battle born site states;
"Our battery is designed as a deep cycle storage battery and doesn’t offer the cold cranking amps most applications require for starting".


I would check with Lithionics about the 315 ah. The data sheet states that it has power reserve for engine cranking but does does not indicate the rating.
There are now a ton of new Lithium batteries beyond BB and Lithionics - Lion, ReLion, Discover, SOK, GoPower, Dakota, Ampere-Time and lots of others - and it might be worth checking if any of those are rated for engine cranking. I guess that is another item to put into a checklist when thinking of replacing wet cell batteries with Lithium.
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Old 04-07-2021, 04:15 PM   #7
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The issue here is that lithium can absorb more energy more quickly, they want 14.5v and can take 100amps at time, most RV are not wire for house batteries directly to alternator they wired to the coach battery and share the charger...there for if you do NOT use DC TO DC your either you will over charge your house (can resolve this with a battery issolator) or burn out alternator as they are not designed to output a constant high voltage...in the boat would Balmar makes a charge controller to address this issue (simular to what DC to DC does...just share as I Era that we upgrade to battleborn lithium and sterling DC to DC charge controler and then did our boat ...
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Old 04-08-2021, 12:17 AM   #8
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Typical Lead Acid batteries (SLA) tend to have their internal resistance rise tremendously as they approach a full state of charge - which means they accept less and less current, and hence not overdrawing the engine alternator.

But LiFePO4 batteries do not, and will accept most of the current given them when charging - which is as you noted - can be very hard on alternators trying to pump out all that these batteries are willing to accept. On one hand this is one of the great benefits of Lithium batteries - they charge up must faster - especially beneficial when charging from a solar system or when running a generator. But as noted if and when connected to the engine alternator for charging it can over tax it.

This is why there are DC-DC chargers made. These devices specifically limit how much amperage charge is given to the house batteries - both by design as well as by switchable parameters in the unit itself. These are made in different amp ratings. I am considering a 20 or 40 amp Renogy model -
Amazon -
https://www.amazon.com/dp/B07Q4SVX3M...ding=UTF8&th=1

These DC-DC chargers not only limit the amperage draw on your engine alternator, but they can also be set for your specific house battery chemistry, set to differing charging modes, and can be set to a maximum voltage, at which point it greatly reduces the amount of charge coming through it into your batteries - making life much easier on the alternator.

Someone mentioned that the downside of these is that they only transmit power 1 way - which is true - as they are designed to only allow current flow from the engine into the batteries. But you can still use the dash battery connect switch (found on many RVs) which connects the house batteries to the engine battery momentarily in order for the house batteries to assist a discharged engine battery (theoretically from not being used) - it depends on how the DC-DC charger is wired in. The dash switch utilizes a solenoid to connect the 2 battery systems due to the high amounts of current the engine starter draws. But properly wired the DC-DC charger should never be connected through that solenoid at all. They have their own on-off remote switching and when off they are automatically isolated from the solenoid connection switching.

BTW - I have 400Ah of Lithium batteries - and love them. They have made all the difference in using my Motor Home as they have made my solar system much more efficient, I hardly have to use the generator any more, and they have really enabled us to boondock much more enjoyably than before when I was fighting with my old SLA batteries. Also saved several hundred lbs of battery weight too.

So it was good of you to recognize a potential problem when using Lithium batteries which may be connected directly to the engine alternator - possibly overly stressing it. But there are simple solutions, and the benefits of Lithium batteries are many.
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Old 04-08-2021, 05:34 AM   #9
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Originally Posted by HappiHenri View Post


Someone mentioned that the downside of these is that they only transmit power 1 way - which is true - as they are designed to only allow current flow from the engine into the batteries. But you can still use the dash battery connect switch (found on many RVs) which connects the house batteries to the engine battery momentarily in order for the house batteries to assist a discharged engine battery (theoretically from not being used) - it depends on how the DC-DC charger is wired in. The dash switch utilizes a solenoid to connect the 2 battery systems due to the high amounts of current the engine starter draws. But properly wired the DC-DC charger should never be connected through that solenoid at all. They have their own on-off remote switching and when off they are automatically isolated from the solenoid connection switching.
I would like to see a circuit diagram from Winnie or others showing how this is done.

I don't think it works as described above. I believe the same circuit that lets the chassis alternator charge the house batteries also lets the coach battery help it start the chassis engine through a BIRD or BIM. Both are bidirectional.

Installing a DC to DC charger makes that circuit one way.

Can anyone who has installed a DC to DC charger tell us if the aux start switch still works?

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Old 04-08-2021, 01:02 PM   #10
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Originally Posted by DavidM View Post
I would like to see a circuit diagram from Winnie or others showing how this is done.

I don't think it works as described above. I believe the same circuit that lets the chassis alternator charge the house batteries also lets the coach battery help it start the chassis engine through a BIRD or BIM. Both are bidirectional.

Installing a DC to DC charger makes that circuit one way.

Can anyone who has installed a DC to DC charger tell us if the aux start switch still works?

David
Yes - the "battery Boost" switch should stil work as a DC-DC charger is wired in differently. In fact, it should not be installed in the battery boost circuit at all. Here's why

The Battery Boost switch simply sends a small 12v power to a solenoid, activating it. That solenoid is wired on one side to the engine battery, and on the other side to the house batteries. So when pressing the Battery Boost switch it activates the solenoid, which then electrically connects the two battery systems - the point of which is to allow the house batteries to give power to the engine battery - helping to provide sufficient power to start the engine. But all power flows through the solenoid.

A DC-DC charger is wired on one side to the engine battery and on the other to the house batteries. Typically activated (turned on-Off) by a separate 12v lead. When turned off there is no pass-through current - meaning that the engine and house batteries are not at all connected.

When turned on it allows 1 way flow of electricity from the engine battery to the house batteries, though it limits the amps flowing through in order to minimize alternator draw.

When properly wired in the DC-DC charger is connected directly to the engine battery with appropriately sized cables, and to the house batteries with similar cables (cables size is determined by the max amps of the charger). These connections can be made directly without any other switching required - other than the DC-DC charger activation switch.

Properly wired in the DC-DC charger bypasses the Battery Boost solenoid circuit and the 2 circuits must - and should - function independently of each other.

For more information I suggest downloading an owners manual for one of the DC-DC chargers so you can read their recommendations for hooking it up. Here is the link to the Renogy DC-DC charger -

https://www.renogy.com/content/RNG-D...060-Manual.pdf
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Old 04-16-2021, 04:03 PM   #11
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Question, besides lighter weight, why LiOn batteries over other type batteries ?


lots mo $$ but maybe less mtce ?
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Old 04-16-2021, 04:31 PM   #12
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Question, besides lighter weight, why LiOn batteries over other type batteries ?


lots mo $$ but maybe less mtce ?
I don't understand the genesis of your question. As far as I can tell no one on this thread suggested buying Lion batteries. I only mentioned that they were one of several new Lithium batteries now available, but did not suggest that there was any particular reason for picking them over any other brand. Or am I missing something?

And what is mtce?
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Old 04-16-2021, 04:42 PM   #13
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mtce is whats called an abbreviation, in this case maintenance !


a question is something you do not know or wonder about - and was exactly why i asked - never said anyone suggested anything - the title said lithium, and nearly no mh has them std - did i - silly assumption imo.


imo - is also a abbreviation for - in my opinion - this is a common method of NOT having to spell out common concepts.


mh- motorhome


hope this lessens the confusion.
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Old 04-16-2021, 05:29 PM   #14
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mtce is whats called an abbreviation, in this case maintenance !


a question is something you do not know or wonder about - and was exactly why i asked - never said anyone suggested anything - the title said lithium, and nearly no mh has them std - did i - silly assumption imo.


imo - is also a abbreviation for - in my opinion - this is a common method of NOT having to spell out common concepts.


mh- motorhome


hope this lessens the confusion.
Then to answer your question - I, personally, can think of no reason for choosing a Lion Lithium battery over any other Lithium battery unless you get a particularly good buy on one. As far as I know they are comparable to other Lithium batteries with a group 31 size battery having about 100AH rating. Battle Born G 31 batteries are rated at 100 AH, Lion at 105 AH and ReLion at 100AH. Lithionics carries a G 31 Lithium battery rated at 130 AH although it is priced considerably higher than the others.

If I were in the market for a new set of Lithium batteries I would select one that had a BT compatible BMS so that I would not need to install an extra device like the Victron Battery Monitor and could monitor the state of the battery via a smartphone app and, to the best of my knowledge, that excludes Battle Born, Lion and ReLion batteries. Lithionics and Discover both have smart apps to monitor their status as probably do other Lithium batteries.

BTW, I had never seen mtce used as an abbreviation for anything so I did not know what that particular abbreviation was. I assumed it was an acronym for something and that is why I asked.
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Old 04-16-2021, 06:07 PM   #15
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Question, besides lighter weight, why LiOn batteries over other type batteries ?


lots mo $$ but maybe less mtce ?
To SmilingSimon and AJMike - Re; Lithium Batteries

There are lots of reasons why Lithium batteries are far superior to Lead-Acid batteries for RV use. The big negative reason is the high cost. But the many really good reasons why LiFePO4 (Lithium Iron Phosphate) batteries are better include:
* Ability to take a charge much faster - meaning you have to run your generator less. Enables your solar system to do a better job.

* Offer a higher usable capacity. SLA batteries can only offer 50% of their stated amp-Hours as usable energy before you start killing them. So a 120 AH SLA battery can only offer 55 amps max, whereas a 100 AH Lithium battery can provide 80-90% - or as much as 90 amps.

* Much lighter in weight. I replaced my 480 AH SLA batteries (240 AH usable) with 400 AH Lithium (360AH usable) and lost over 150lbs of weight while gaining 120 AH of usable capacity.

* Much longer life span. Even if properly maintained and not over drawn down most SLA batteries are pretty well shot after just a few years. My new Trojans only lasted about 1 1/2 years. My new Battle Born Lithium have a 10 year warranty.

* Along with that Lithium offer about 10x the number of duty cycles.

* Overall Lithium batteries just work much better. No maintenance and high capacity. And our solar system can really keep them charged up. Going to Lithium enabled us to really boondock for far longer than we used to.

There are tons of posts and articles all over the web about Lithium batteries and how good they are over SLAs.
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Old 04-16-2021, 06:33 PM   #16
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To SmilingSimon and AJMike - Re; Lithium Batteries

There are lots of reasons why Lithium batteries are far superior to Lead-Acid batteries for RV use. The big negative reason is the high cost. But the many really good reasons why LiFePO4 (Lithium Iron Phosphate) batteries are better include:
* Ability to take a charge much faster - meaning you have to run your generator less. Enables your solar system to do a better job.

* Offer a higher usable capacity. SLA batteries can only offer 50% of their stated amp-Hours as usable energy before you start killing them. So a 120 AH SLA battery can only offer 55 amps max, whereas a 100 AH Lithium battery can provide 80-90% - or as much as 90 amps.

* Much lighter in weight. I replaced my 480 AH SLA batteries (240 AH usable) with 400 AH Lithium (360AH usable) and lost over 150lbs of weight while gaining 120 AH of usable capacity.

* Much longer life span. Even if properly maintained and not over drawn down most SLA batteries are pretty well shot after just a few years. My new Trojans only lasted about 1 1/2 years. My new Battle Born Lithium have a 10 year warranty.

* Along with that Lithium offer about 10x the number of duty cycles.

* Overall Lithium batteries just work much better. No maintenance and high capacity. And our solar system can really keep them charged up. Going to Lithium enabled us to really boondock for far longer than we used to.

There are tons of posts and articles all over the web about Lithium batteries and how good they are over SLAs.
In my response I assumed he was asking why buy Lion Lithium batteries rather than some other brand of Lithium batteries, and that is how I responded, but if the question is why buy Lithium batteries rather than wet cells of some type, then the answer would be very different.

First, my personal belief is that not all users, even dry campers, need to replace their wet cell batteries with Lithium. I did, but that is because the 2018 Winnebago Fuse I own has a compressor refrigerator and it alone uses enough electricity during the warmer months to drop the wet cell battery state to half its fully charged state or less. Replacing the wet cells with Lithium batteries means that even in warmer months when the compressor refrigerator is almost constantly running and when my wife uses her electric tea kettle and we watch DVD movies on the TV at night we still have more than half of our battery power remaining, and the solar charges that quickly.

If you feel you need Lithium batteries, then there are significant advantages to having them. You have listed most of them, although I would add that for us there is a comfortable feeling in knowing that when we wake in the morning there will still be plenty of power left and that the solar will replace a significant amount of the battery power used during the night. Before I replaced our wet cells with Lithium I always worried that we would be out of power in the morning, and that actually did happen to use, but with the Lithium batteries I no longer worry about that or about having the solar recharge them.
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