Can a lithium pack be charged by alternator alone?

NobleOne

Learning Curve Climber
I have a T1N with a 150 amp alternator, which I understand to be more forgiving as far as using the alternator to charge the house batteries than the later Sprinter models. I know lead acid batteries must be full recharged, and that lithium batteries don’t require such (some reading indicates that they might actually live longer). This seems to lend itself to the possibility of recharging such a pack via alternator alone...no solar involved. Is that reasonable and feasible using these?
http://www.lithiumrvbattery.com/Lithium_RV_Battery/GBS_100AH_Cells.html
Or am I missing some key bit of information?
 

john61ct

New member
Yes, LFP is very fast, no need to get to Full.

But put a Sterling BB series DCDC charger in between to protect your alt setup and give the LFP its custom setpoints.
 

owner

Well-known member
If your LFP is bigger than around 50Ah it will suck very hard on your alternator.

I started off with a 50Ah LFP bank, and if its got mid to low SOC it will easily pull 80A from the alternator. So a 100Ah bank like that would pull double and your car voltage will sag badly.

I now have a 160Ah bank and have put a 30A DCDC charger between it and the alternator, just to stop that from happening.

You also dont want to be holding 14.2V on the bank once it is fully charged, so you need to be able to disconnect it from the alt on long drives. A decent DCDC will effectively do this for you automatically if set up properly.
 
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wankel7

Member
If your LFP is bigger than around 50Ah it will suck very hard on your alternator.

I started off with a 50Ah LFP bank, and if its got mid to low SOC it will easily pull 80A from the alternator. So a 100Ah bank like that would pull double and your car voltage will sag badly.

I now have a 160Ah bank and have put a 30A DCDC charger between it and the alternator, just to stop that from happening.

You also dont want to be holding 14.2V on the bank once it is fully charged, so you need to be able to disconnect it from the alt on long drives. A decent DCDC will effectively do this for you automatically if set up properly.
Did you try to charge your 160aH bank without the B2B charger in place?
 

owner

Well-known member
Did you try to charge your 160aH bank without the B2B charger in place?
I have a 4 way switch that does allow direct alternator charging if I need it but I havent been game to switch it to that position with low soc on this big bank. I imagine it would pull everything it could from alt until the 100A thermal breaker kicks in.
 

RonR

Recovering Sprinter Owner
I had the optional heavy duty alternator and initially could never get more than about 60A into a 320AH battery. After I upgraded the alternator ground wire, a lot of the factory battery cables and battery grounds I could get 100A.
The limiting factor for very high current charging is the net resistance of all the wires to and from the battery.
With factory wiring I do not think you could get over 80A, which is likely a good thing since it will limit the load on the alternator.
But...
You do need a way to turn it off. Once it is charged at about 14.2 to 14.4V (read your battery spec or watch for the voltage where the current starts to drop quickly). Then you should disconnect the alternator. Lithium does not like to be kept at max voltage and float charged. It won't be destroyed but the lifetime will be decreased.

Ron
 

NobleOne

Learning Curve Climber
What about the Orton method? Would that overcome those listed concerns/limitations? I would like to use a 300 or 400 ah setup.
 

RonR

Recovering Sprinter Owner
?? As I recall, Orton used the BtoB method with the controller / converter??

I can't comment other than to say that I think the Sprinter alternator cables and ground are inferior. As I recall they are #2 wire with a fairly long run from the alternator to the battery. In my Sprinter, they also added a 3' piece to connect to the factory battery isolation relay that could be replaced with a 6" piece.

I could never find the "official" answer but I believe that the voltage regulation point is the alternator terminal. So based on air temperature you will have around 14.3V between the alternator case and the alternator output. At 100A you will loose .16V for every 10 foot of #2 wire not counting the voltage drop of each connection. The wiring / location needs to be such that you can sink the current you desire from roughly 14.3 at the alternator.

Any eye opening experiment is to load the alternator as high as you can and then run around and measure voltages to the chassis. This includes the voltage of the alternator case, voltages on each side of a connector and voltages on each side of the isolation relay.

It is hard to get a reliable 100A in a 12v system.

Ron
 

fourgonbound

Winnebago View 24J 2017
I get somewhere around 70-80a from alternator directly to 300ah lithium battery via double 2ga wires (so equivalent to 0ga?) running 12'. Good enough for me and I don't use it much at all since I have solar.
 

eslmooney

New member
I am going LFP 4s 4p 180ah cells 720ah no solar - SBMS by ElectroDacus in a 2006 Roadtrek sprinter I am thing I need a bigger alternator, there is now 150amp.
 

NobleOne

Learning Curve Climber
I am going LFP 4s 4p 180ah cells 720ah no solar - SBMS by ElectroDacus in a 2006 Roadtrek sprinter I am thing I need a bigger alternator, there is now 150amp.
200 amp alternator Bosch AL0817N on Amazon for $311 or Rockauto for $301. Direct bolt-in for the T1N.
 

InterBlog

Member
I am going LFP 4s 4p 180ah cells 720ah no solar - SBMS by ElectroDacus in a 2006 Roadtrek sprinter I am thing I need a bigger alternator, there is now 150amp.
**OP beware.**

**Eslmooney beware.**

Even WITH the Sterling B2B, the extra wear on the alternator will make this configuration a very risky proposition.

How do I know? Because I have that exact Sterling and that exact Electrodacus in a T1N, and my Bosch 200 A alternator lasted a total of 16 months of very occasional use before its clutch pulley wore out. My alternator's effective lifespan ended up being measurable in mere HOURS.

What the alternator was DESIGNED to do and what we are ASKING it to do are two different things in this scenario, even if the numbers on paper seem to make sense. Numbers on paper are not equal to conditions of wear in real life.

At this point, I am 100% convinced that the only SAFE non-solar way to charge lithiums in a T1N is by using a second alternator. A second alternator is a very expensive proposition because of the mounting bracket availability issue. For the moment, I will omit those details and that research.

Rather than belabor the alternator failure details in this post, I'd encourage you to read this account of that failure below (non-monetized blog post).

Understand that if your alternator fails the way mine did, it could easily put your rig in danger, and your life in danger, because when its degradation causes the chassis battery voltage to fall too low and the computer to shut down, your T1N is just going to stop dead in the middle of the freeway, wherever you happen to be at that moment (possibly with a 70 mph big rig bearing down on you). That is what will happen if you don't catch that kind of failure in time to save yourself from an uncontrollable shut-down.

https://interstateblog.blogspot.com/2018/09/psa-alternator-clutch-pulley-failures.html
 

john61ct

New member
Yes just having the tool does not guarantee anything.

Maybe needs to derate the output by 80%.

Maybe a much more robust alt is required.

The Sterling is still needed to protect whatever the second alt is.
 

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