Advice on lithium battery

[Marcel Huijser]

I need to redo a battery setup, and I can use some advice.

Main power AGM/Solar/110Vinverter:
We have a main solar setup that puts power into AGM batteries mounting in box under floor (not insulated), and it has a 110V inverter connected to it. Heavy, so at the end of their life span I will probably replace with lithium. But lithium may require a new charge controller so, it is a can of worms that I may not want to open right now as this system is doing fine right now.

Lithium/Alternator:
The question is about a lithium battery that is charged by the alternator. It is not connected to solar or the AGM batteries, nor the inverter... it is completely stand-alone. It is mounted under the van on the ladder rail. This powers the air heater and the coolant heater, as well as the fridge while driving. I didn't realize until last year that you shouldn't charge a lithium battery when it is below freezing (I know this sounds stupid, but I just didn't know). You should heat the battery first and get it above freezing before charging. I don't know what brand/type of lithium battery is under the van now, nor what it's battery management system does and does not do... I still need to check this.


Questions:
1. Would you go for a heating strip on a thermostat and leave the lithium battery under the van (outside)?
2. Would you bring the lithium battery inside (with a new hole for the wires to the alternator), and potentially add a heating strip?
3. How would you power the heating strip? 12V 110V? Note that turning on the inverter (110V) for long periods is not something I can afford in the winter... not enough daylight and not enough sun to recharge the AGM batteries with solar if I leave the inverter on.
4. Replace the current lithium battery with a self-heating battery. Battle born seems to have a battery that is designed for camping below freezing.

Many thanks for your insights!

[Scalf77]

OK, so first I don't understand the thought process behind charging just the lithium battery to only run the fridge, air heater and coolant while driving. Do you also use that battery to power those devices while not driving?

Does this mean you don't use your alternator to charge you main house bank? it sounds like you don't. I am sure there is a reason, I don't see it at the moment. That also doesn't make it invalid. Actually having a lithium for the house and a AGM connected to the alternator would make more sense.

You seem to do cold weather trips so a battery with a built in heater would be a better way to go. Moving them in also is a good thing, as they tend to pick up a lot of heat under the van in the summer time. The battleborn solution is good for smaller systems, depending on the size of your total banks we maybe able to find a larger battery that will fit your needs.

-greg

[Marcel Huijser]

Thanks Greg, sorry for the confusion.
I will try to clarify what we have and what the issues are.
I recognize that what we currently have may not be the best.

Yes, we camp in temperatures well below freezing.

The Lithium battery is charged by the alternator while driving.
This battery powers the fridge while driving.
When camped, the fridge is running on propane.
When camped, the battery also provides 12V to the diesel air heater and diesel coolant heater.
The main issue is that I think the current lithium battery may not be suited for charging when it is below freezing. If it doesn't have enough charge, or if it dies because of improper use, I can't run the coolant heater in morning in winter, and I am stuck in a perhaps very remote area in winter.

The main house bank (AGM batteries, charged by solar) are not connected to fridge, air heater, or coolant heater. The main house bank is only for lights, and for powering 2 laptops (with inverter), cell phone booster, charging small devices when camped. It is currently only charged by solar (or 110 V shore power, but we are rarely camped where we would have access to 110V). It is working fine as is, though in winter I sometimes barely get enough charge from the solar panels and this makes me wish I could also charge the AGM batteries on the alternator. Perhaps I would need another charge controller, I don't really know.

Ideally, I would replace the AGM batteries with lithium batteries that can deal with very cold temperatures. Ideally, I would charge those new lithium batteries through solar, and also have the option to charge on alternator. But... that may be a very expensive undertaking, the main bank is not a big problem now, and the AGM batteries are only about 4 yrs old. On the other hand, I would have only 1 battery system then and be done (delete the current lithium battery, connect fridge, air heater and coolant heater to the new main bank).

So, rather than replacing the entire main bank and charge controller, my first thought is/was to make sure the current lithium battery is replaced by another lithium battery that is designed to deal with cold weather (heated battery, potentially move into the inside of the van).

Does this make sense?
Thanks for your thoughts and advice!

[Scalf77]

In the short term I would replace the lithium battery with another AGM, it would be a cheaper short term solution. What are you using between the alternator and lithium battery to charge?

There are a number of ways to get there. What are your current charging devices IE: Solar and Shore? You could make some incremental changes and be ready for full lithium when needed.

In the mean time when solar isn't fulling charging your house batteries, when you get home plug in and get them through a good charge cycle. Your current charging methods are probably not the best for the lifespan of your batteries.

greg

[Marcel Huijser]

Thanks Greg, much appreciated!
There is a solenoid between the alternator and the lithium battery (don't know specs... will have to crawl underneath soon). And I activate charging with a switch.