New Sprinter owner, lithium battery for solar recommendations, 12V vs 24V questions

Hey folks,
Brand new 4x4 Sprinter 144" owner. I've got solar in my previous rig, but the 200AH bank I had didn't last as long as I'd hoped. I'd like to move to lithium for this build out, despite the cost. I've heard battle born battery's name tossed around as the current go to. How are they for value/performance? Anything I should know about lithium in general? Also, is there any real benefit of running 24V vs 12V? It seems like it simply haves the consumption of devices that are 12 or 24V but it also halves your AHs. So, what's the point? wiring with smaller gauge wire? Let's say I went with 600AH at 12V. That would give me 300AH at 24V. What's the real world performance difference? Does it make inverters more efficient?

EDIT-I wouldn't be able to charge a 24V battery bank off the alternator would I?

I plan on covering the roof with solar so I can potentially run a small window unit in the summer. I haven't done the measurements yet, but it looks like I could fit 750 to 1000w up there without too much overhang. Any ballpark suggestions for a charger/controller? I loved my Midnite Solar classic kid but that maxes at 500w.

Cheers.
Alex
 
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jonyjoe101

Adventurer
go to the hurriedyear.com website someone there has a sprinter and he shows how to run an AC with solar, he does it with agm batteries 780ah (3x 260ah agm each weighing 162 pounds total weight 486 pounds). His website has alot of pictures on how he got his van setup and the parts he used.

But pound for pound lifepo4 is the better way to do it. 100ah of lifepo4 weighs about 30 pounds, 4 of them will be comparable to 800 ah of agm (total weight 120 pounds). If that hurriedyear person can run his AC on 800 ah, you only need 4x 100 ah lifepo4 instead of the 6 you were planning to get.

There is a video on youtube "lithium battery test versus gel" that tests a 100ah lifepo4 against a 100ah and 220 ah lead acid in a worst case scenario high drain test. Below shows the results, lead acid being drain quickly drops voltage very fast and the load has to take more amps to compensate resulting in even more voltage drop draining the battery quicker.
100 ah lithium 94 ah usable
100 ah lead 31 ah usable
220 ah lead 73 ah usable

The only thing I done differently with charging my lifepo4 with solar was put a overvoltage relay (about 6 dollars) that will trip another bigger relay between solar panel and controller if the voltage goes too high. Its like a deadman switch in case the bms fails etc.
 

Joe917

Explorer
lb for lb Lithium is the way to go. $ for $ it is still not close, go lead acid.
You can charge 24v off the alternator with a battery to battery charger (Stirling is one manufacturer)
The advantage of 24 over 12v is a saving on wire gauge.
 

pdxfrogdog

Adventurer
The advantage of 24 over 12v is a saving on wire gauge.

I'm no expert, just looking for clarification on the above statement. My understanding is that selecting wire gauge should be based on the number of amps that will be flowing through the conductor and to a lesser degree the duty cycle of the flow?
 

Joe917

Explorer
I'm no expert, just looking for clarification on the above statement. My understanding is that selecting wire gauge should be based on the number of amps that will be flowing through the conductor and to a lesser degree the duty cycle of the flow?

Yes, twice the volts means half the amps.
 

john61ct

Adventurer
The ONLY advantage to wiring a rig for all-24V, or other higher voltages

unless you require specific high-amp consumers of that voltage

is a marginally lower cost in copper gauge required to cover long runs of high current with minimal voltage drop.

99% of DC load devices are sold at 12V, cheaper, available, more choices.

If supply is 24V, you would likely need to do lots of 24-12V conversion, added cost and lower efficiency.

Better IMO to go 12V by default, for a huge winch or other high-amp higher volt consumer, dedicate a bank or investigate 12-24 serial-parallel relays to switch as needed, used in trucking and race cars
 
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john61ct

Adventurer
A quality lead bank can be made to last 8-10 years no problem, but it takes knowledge and some gear to care for them properly.

LFP is fantastic but 5-7x the investment, very different and more precise care needs, so risky.
 

john61ct

Adventurer
No need to avoid multiple controllers.

If you will encounter partial shading, the ideal is a 1:1 ratio panels to SCs.

Victron MPPT gives a lot of flexibility, ant at smaller sizes under $150 per.
 

OCD Overland

Explorer
I have 4 100Ah Battle Borns, and they seem to work as advertised. I can get about 90% usage out of them before the voltage drops too low. The drawback to the BBs is that the built in BMS takes up a lot of space, so you end up with batteries that are just a tad larger than a typical T-105. I got them because I thought I would be temporarily using them with the charger that came with our camper and so it made sense. I ended up going ahead and switching the whole system over to Victron on day one, so in hindsight, I wish I'd gone with a less expensive and smaller solution.

The choice is really straightforward. You'll pay twice as much per amp hour for lithium over AGM, and you need to ask if that's worth it to you. In our case, we were limited to 200 useable amp hours with AGMs due to space limitations, and the LFPs gave us 360. We didn't think 200 would be enough, so decision made. It turned out to be the correct one, since we regularly take our batteries down below 40%.

If you're taking your sprinter as a second home, then be sure to calculate in the solar tax credits when deciding. Batteries, charger, etc. - it all counts as part of the system. And buy your panels before president **************' solar tariff comes in effect.

With the capacity you're thinking about, I'd look at a Victron MultiPlus, battery monitor and solar charge controller. Get their bluetooth enabled monitor and controller so that you don't have to deal with dongles and stuff. It works best if you have an onboard wifi/cellular router so that you can take full advantage of their VRM portal. I got our stuff from Inverter Supply - they seemed to have the best prices at the time. All the bits and pieces we got from AM Solar, who were kind enough to help get it all sorted despite us not buying the main equipment from them.

Bit of advice on the panels - give yourself at least one port for some portable panels. Being able to set up 200w or so tilted correctly, or in better sun, makes a big difference especially in winter. A Kw of solar in the shade is no better than 50w in the shade.
 
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Wow, for some reason, I never got notification that this thread was updated. So, reading and asking questions over at SolarPanelTalk, there's a real debate that Lithium is really as good as it says.

What do you guys think about the flat / flexible panels you basically glue onto the roof? Seems great for aerodynamics and all, but how much less efficient are they?

I can usually get pretty cheap leftover panels from installs in socal.
 

Darwin

Explorer
With it lithium it depends on what your needs are. If you are trying to run high draw appliances like an induction cooktop, microwave, AC, etc. Lithium I think is the way to go. If you don't need to run that stuff or are just taking week long trips or so, probably better to save the money and go with AGM.

The higher voltage battery configuration I believe starts to make more sense if you are planning this high draw appliances, 100 amps at 12 volts is a lot!

Same for the panels, I think it depends on what you are after, they work, but if you are trying to harvest as much energy as possible they are not the best option.
 

rruff

Explorer
Wow, for some reason, I never got notification that this thread was updated. So, reading and asking questions over at SolarPanelTalk, there's a real debate that Lithium is really as good as it says.

Poor charge control will kill them. Can't use LA chargers. They should not be charged when below freezing, or float charged. Otherwise, avoid overcharging and excessive discharge, and you should be good for many years.

The big advantages of LiFePO4 besides the lower weight and long lifespan, is that they are more than happy with partial charges, and do not need saturation charging.

Flexible panels: Nice idea but I don't know of any that last. If you go that route, look at ones that have an aluminum backing.
 

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