Batteries in a small van

[jpaddler]

The budget isn't an issue right now, I'll be staying in the van for work (instead of renting an overpriced apartment or bedroom from someone)

I've been researching different battery types, but FLA is out of the question.

Battleborn lithium batteries would be my first choice, next would be the Firefly Oasis, and third runner up is the lifeline agm.

I just know that with the limited space I have for solar (and winter in the rockies), I'll need to charge the batteries while I'm driving.

I'm really drawn to the ctek ds250 dual, with the smartpass, as it's an all in one solution, for charging off the alternator, and solar when I'm parked. But, unfortunately, there are no adjustments, to taylor it for the different batteries out there.

I'm just trying to figure out something that has adjustable charging parameters, so I don't screw up whichever battery I decide to go with.

I'm sure I can find a stand alone solar controller, that would have the flexibility of adjustments.

The key will be to integrate it with a 12v to 12v charger (isolator, acr, combiner, whatever other terminology is used) that has the adjustability as well.

If there is a company out there, who makes both products, and they can work in conjunction with each other, then they would get my business.

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[TechScott]

I believe the ctek has temperature compensation, and it's 14.4 at 77 degrees.
I downloaded a tech manual for lifeline agm batteries, and that seems to fall in line with their recommendations.

I know it starts out with a 15+ volt charge, to help fight sulfation. That's one of the reasons, it was unsuitable for battleborn lithium.

I'm open to other charging options, but I liked the idea of one that could charge while I was driving back and forth on the regular 200 mile jaunt, and a solar controller when I was parked. Going into the winter months, the solar will be less of a factor

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BTW, here's a link to chargers/solar controllers Battle Born lists for their Lithium batteries https://battlebornbatteries.com/charger-compatibility-table/

 

[John61CT]

> maybe diode based isolators could redeem their reputation

Problem is the drop varies a fair bit with both voltage and current.

My recommendation is as you buy a new charge source, make sure the voltage setpoint is adjustable.

Then if you go LFP in the future you're already set.

Another option is to have a lead batt - can be a starter, or just a small cheap one - be the direct target of whatever existing sources, lots of leeway there.

And use an adjustable DC-DC "batt2batt" charger like Sterling or ProMariner to carry the well-regulated charge to the LFP bank.

If you carry that bank from off-grid home to boat to van, the DCDC charger can come along and tap into whatever existing infrastructure is in place, that would be the only device to charge your LFP from any source, gennie, alt, solar, shore.

 

[John61CT]

There are modern MOSFET based isolators that don't have the voltage drop issue, but they are not cheap.

The only use case I can see is where you require high current flow but only in one direction.

 

[John61CT]

> here's a link to chargers/solar controllers Battle Born lists

I haven't seen a charge source yet marketed as LFP-ready or even sold by the cell vendor that keeps voltage below 3.45Vpc.

They **all** recommend voltages too high for maximum longevity.

I will leave it to the reader to speculate why that may be.

The **only** charge sources that I would buy for LFP let the user create a custom charge profile.

That will allow it to work with any batt chemistry.

 

[John61CT]

> I'm sure I can find a stand alone solar controller, that would have the flexibility of adjustments.

Yes in solar that is very common, no problem.

> The key will be to integrate it with a 12v to 12v charger (isolator, acr, combiner, whatever other terminology is used) that has the adjustability as well.

Wut? Any of them these devices, and there are hundreds of good ones, work together with any charge source. 99% are "voltage following".

So whatever the primary charge source is putting out, all the ACR does is close the circuit when V rises on either side, so the current flows to both banks.

Once charging stops, relay opens and the banks are isolated.

Best by far is this ​ https://www.bluesea.com/products/7620/ML-ACR_Automatic_Charging_Relay_-_12V_DC_500A

 

[John61CT]

> with the limited space I have for solar (and winter in the rockies), I'll need to charge the batteries while I'm driving.

This will only be sufficient with LFP.

Firefly less so, will still need shore power a few times a month to get to 100%.

Lifeline forget it, throwing money away.

I would strive even with Firefly, to still get to 100% as often as possible. There is a huge gap between "that won't murder them" and getting good value lifetime cycles from your $500 per 100AH bank.

Why are you so dead set against good but cheap FLA at 1/6th the price, a few pieces of plywood and some sealant. . .

 

[jpaddler]

Thanks John... Reading about the blue sea product right now.

I worked in an auto shop for a number of years, and one of my jobs was charging batteries, to test their condition. I've been around them enough, to know that I don't want the vapors in such a small living space.

Trying to incorporate a sealed, vented box into the van I have, is also an issue.

I also like the sealed batteries, because of the options for mounting them in a way that makes the best use of my limited space.

I understand that FLA is the cheapest, but it isn't practical for my needs.

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[John61CT]

OK just know a bigger investment in the bank implies spending more on the care infrastructure, like a $100+ batt monitor, as opposed to a $10 hydrometer.

Needing a high acceptance rate, and/or mounting sideways are IMO the two valid reasons to go AGM.

 

[jpaddler]

Very true... The battery monitor I'm looking at (nasa clipper bm-2) is almost 200 dollars.

I called blue sea, and spoke with them about the ml-acr. Apparently there is not voltage adjustments in it, and he recommended a proisocharger from promariner. I'm waiting for a call back from their tech support department to see if it will do what I need.

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[John61CT]

This class of device including those latter, does not do DC-DC conversion.

That would require a DC-DC charger, much much more expensive.

And I already asked you, what makes you think that's what you need?

Only Sterling and ProMariner's "batt to batt" units offer user-custom charge profiles.

 

[jpaddler]

I'm thinking, that I need something to protect the house battery bank from overcharging by the alternator, while I'm driving down the road.

If I have a lead starter battery up front, and a lithium (or agm, that has specific charge voltages) battery in the back, then I'm not sure how a automatic charging relay would be able to differentiate the needs of the specific batteries.

Maybe I'm making this too complicated, trying to wrap my head around it all.

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[John61CT]

Yes if you do invest in an LFP bank, then one of those two adjustable B2B will help you get good longevity.

Charles Sterling told me they were coming out with a 180A version RSN, but likely your alt doesn't put that much out.

Note you need to be careful, monitor Alt diode temps, most stock ones are designed for such heavy duty cycles. What vehicle?

60A probably a good size, maybe $400, check out Alan at bay-marine, great support.

The ProMariner units have the same motherboard, maybe cheaper?

 

[jpaddler]

It's a Ram promaster city, 160 Amp alternator.

In thinking that I'm making this too complicated, I called battleborn, to see if I could just hook their lithium battery up to my charging system with an automatic isolator, and they said that was fine.

I'm guessing that the BMS will cut it off, if it gets too much voltage from the alternator, and my starter battery will absorb the spikes and dips?

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[John61CT]

No, all the "drop-in" vendors tout that ability, that's their whole marketing model.

As I said, yes that higher V won't murder them, but you'll get many hundreds if not a thousand extra cycles longer lifetime by avoiding going over 3.45Vpc, or 13.8V.

Every LFP chemistry battery is the same in that regard.

And so is every vendor in the market wrt ignoring that information.

 

[John61CT]

I'm guessing that the BMS will cut it off, if it gets too much voltage

The issue is that you as the owner, wants to define "too high" much more conservatively than they do.

BMS should be a last-ditch protective defence against your equipment failing. Multiple layers of LVD / OVD are common in LFP, but usually larger more expensive banks.

 

[jpaddler]

Ok, so what can install between the starter battery, and the lithium battery bank, to stop it from going over 13.8 volts, but still get a decent amount of amps while driving?

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[John61CT]

One of those B2B chargers

 

[John61CT]

How many AH will your bank be?

 

[jpaddler]

2, 100ah lithium batteries.

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