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400AH lithium cells? Best price per AH? $0.85/ AH?

15441 Views 216 Replies 12 Participants Last post by  sportcoupe
I'm looking to make a storage battery for a camper. Lithium is a better value for the money than lead IMO.

I want a 12v 400AH lithium pack as simple as can be. Fewer cells is better, isn't it? So, that's four 400AH cells I need plus a BMS.

I've heard prices are as low as $0.85/ AH if not in a hurry. Is that correct? Suggestion or comments?

Thanks!
-John
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I would not recommend EV packs or second-hand cylindricals etc, in fact any chemistry but LFP for House bank usage in a mobile living space.

New quality large LFP prismatics go for $7-9 /AH before shipping, in the US market.

Do not go Alibaba direct from China, if NG you gonna pay to ship them back? Lotsa scammers out there.

Cheapest quality deep cycle **FLA** is $1 / AH.
 

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If you treat LFP well, it will last for decades.

In the long run cheaper than good deep cycling lead.

No dropping acceptance rate as SoC climbs, no need to get to Full, little voltage sag at high currents, all are pretty compelling.

But if you murder the bank - which is not hard for noobs - you are a **lot** more out of pocket.
 

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No way bare cell prices coming down, not from quality makers.

Anything much cheaper will be factory seconds or even counterfeit scams.

An improved high-volume supply chain will just mean a bit cheaper shipping costs and added value like higher trust levels, native-English CS, local warranty returns, matched capacity or even pre-balanced sets etc without paying a lot more.

Which would of course be fantastic.

Now, quality high-current "open hardware" BMS at nominal 12V, that would be a likely place to see prices drop so DIY can have the same protections as say a Victron or Lithionics system without being an engineer reinventing the wheel every time.

Anyone know who makes those BatterySpace prismatics?
 

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Lithium batteries freeze easily

If you plan to use this battery when the weather drops below 40F you are pretty much stuck with FLA or AGM
Nope.

Cannot **charge** (much) below freezing,

nothing to do with "freezing"

but discharge is fine down to far below

Storage often even lower no problem.

See the spec sheets for Winston, CALB etc
 

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Yes, true.

Savings in wire gauge rarely offsets cost of voltage conversion gadgetry.

But for those with some good reason I can't imagine, 24V and even 48V alternators do exist, can be custom wound.

Maybe on a boat using electric propulsion or very big winches, bow thrusters etc
 

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48V as a House bank makes little sense to me, would need to run a separate 12V bank for normal devices, converters are crazy expensive. Maybe if you want an all-mains setup, run everything off a huge 48V inverter?

But no, silly to give up alt charging when it's already there.

Even 24V to me violates KISS. SCs are not a major expense overall, and wiring runs are one time, don't break like conversion gadgets.

From a practical economics POV, only if the alt is 24V already, or if really needed for important high-current devices, maybe say winches?
 

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Completely agree AGM are poor value, use only if install space requires, or money not an issue.

Yes Rolls / Surrette is fantastic. But only FLA. Their AGM are relabeled chinese.

It your batteries are gassing excesively would tell you the voltage is set too high
Normal usage to vendor charging specs produces some gassing.

But that has never been an issue for me even in a tightly sealed living space, long as good controlled ventilation is in place. Put the exhaust port in the bank area.

Yes, some people are hypersensitive or dislike the smell, so box the bank up and vent to the outside, NBD.


> Chi-Com LiFeP04

Please define, and link to LFP that you consider better quality wrt longevity.


> Only a fool would size their battery for 1-day Run time

True for lead maybe, but not if ICE recharging on demand is convenient, and solar there for the long tail. LFP makes the solar redundant.


> not an RV which is part time use

millions live mobile full-time


> You are right golf cart batteries last about 3 years as designed.

Well coddled, even just-decent GCs can go 6-7 years and still be above 70% SoH.
 

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This is one way to reduce problems of paralleling, but
Last thing in the world you want to do is install Pb batteries in parallel
Finally!

I think

> Guaranteed to cut cycle life in half

is overstating the case though, for just a few paralleled strings.

I personally like / need two strings for redundancy, in critical and/or remote full-time use cases.

But it is indeed my understanding, that going **past 3-4 strings**

(not of single cells paralleled to get higher AH, but of multiple-unit strings)

will result in balancing issues and shorter overall cycle lifetimes.

Can you confirm that is the case? Are there other issues? Can you concisely describe **why** paralleling too many strings is bad?

Any links or cites to back it up?

Would be greatly appreciated
 

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How many cycles are the LiFePO4 cells expected to last?
From top-notch vendors, makers like

Systems: OceanPlanet (Lithionics), Victron, MasterVolt, Redarc (Oz specific?)

Bare cells: ​Winston/Thundersky/Voltronix, CALB, GBS, A123 & Sinopoly

If I have missed any sold to consumers, please let me know.

Their spec'd cycle lifetimes appear to actually be very conservative, perhaps building in some expected abuse.

Very much unlike the lead batt industry, where even perfect coddling rarely matches claimed lab performance, marketing departments have too much influence vs engineering.

But IMO, following the vendor LFP charging specs for day to day usage is IMO inherently abusive, compared to avoiding the voltage shoulders.

With the latter, looks like decades' daily use is possible, certainly 3-5x their lifetime estimates,

if well coddled, no big mistakes, and in a gentle House cycling use case. It is possible that calendar lifespan will end up being more influential than # cycles.

Kindest explanation is, longevity is not their primary goal, violent-currents military and EV usage is the assumption for their testing and research.
 

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> a huge system in excess of 1000 watts, and that requires 24 volts or higher

Not "huge" and a 12V setup is fine.

My favorite setup is a ~250W / 40+Voc panel paired with a Victron 75/15, around $120. Super efficient and full-featured, custom setpoints and data logging from my phone.

Add as many such pairs as you like over time to fill the roof or on slideouts, portable folding, whatever.

No need for the panels to match, and each is MPPT optimized for azumith angle or partial shading conditions.

Maybe 80AH avg per day each into the bank, including some days less than ideal conditions. Get 5-6 pairs and run 16k btu aircon off it

Yes silly I know.

But going to 24V House setup just to save a bit of money on thick wiring or cheaper SCs is sillier.
 
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