Battery recommendation needed

[kmbush56]

Hi Will, thought I’d ask what you guys think...out of this list which is the best to use in my off grid camper (4x):​

1) SOK Battery LiFePO4 Deep Cycle Rechargeable Lithium Battery 12V 206ah Built-in BMS,Low Temperature Disconnect.​

2) Ninthcit 3.2V 230AH LiFePO4 Deep Cycle Battery Cells with Iron Phosphate, Grade A Replacement Automotive Lithium Motorcycle Batteries with QR Code, Perfect for Boat, Marine, Golf Cart, Camper(4PCS)​

3) Ampere Time 12V 300Ah Lithium LiFePO4 Battery, Built-in 200A BMS, Max 2560W Power Output, Easy Installation, 4000+ Deep Cycles, FCC&UL Certificates, 10-Year Lifetime,​

4) LOSSIGY 12 Volt 300AH Deep Cycle Lithium Ion Rechargeable Battery, The Perfect Replacement for Solar Wind system, RV, Marine Off-Gird Battery, Built in 200A BMS, 4000-7000 Cycles​

Many tks!​

 

[chrisski]

Looks like you have three drop in lithium batteries listed and one build it yourself. Do you want to go through the process of DIY with the process of choosing a BMS, busbars, wIrving, cases, etc? Different direction than the other three. That’s he route I’m going, and I’ll save 50% once I’m done, not the 75% I had planned.

Can’t speak much on the others. I did not think SOK, had a low temp cutoff, but if it does not, that just means battery charging needs to be shut off for cold temps a different way.

 

[Rocketman]

How much power does your camper need? Both as a capacity (Ah’s) and also all at once (Amps). Without results from an energy audit - it’s tough to help.

Do you want to make your own battery?

If you only need 80Ah’s - the best answer might be the cheaper one( it’s 2.5x your needed size)… unless you need certain features that other batteries have: low temp charger cut-offs, heating, a certain level of amps to run a inverter, etc.

Help us - help you…

 

[rmaddy]

I did not think SOK, had a low temp cutoff

It does. It's listed as a feature of their batteries on their website.

 

[kmbush56]

Tks so much for your replies! Ok so I don’t know if I have all the time to build it?..not sure how hard that’d be..but I’m really looking for reliability and less weight and less size which the SOK seems to offer. Will P said it was well built in his vid so I’m leaning that way but curiousity killed the cat on the others. I’ll be in the woods boondocking far away. Lossigy offers a great price for lotsa ah (To run a/c we calculated about 600ah required for our 800w of solar panels including grey days, but I’d go to 800 if necessary ). I have a micro air 364 slo start for our a/c to help the cause. So w that, thoughts?..tks : )

 

[Rocketman]

Ok… air conditioners are a more difficult item to run. It can be done, but takes planning ahead and lots of equipment.

To run the A/C you need an inverter- probably a 3000w. You will need three or four batteries paralleled to got the amps high enough to fully drive the inverter on the A/C. The LCR (locked rotor amps) need to be overcome. Your slo start will help. How many amps does it take to start it? That is a very important number to know while planning also how many watts does the a/c take to run.

You will be able to run it for a while. Then you need to refill those batteries. Which is another story…

(Many people find a Honda generator Is a better way to run the a/C’s.

 

[kmbush56]

Tks Rocketman, appreciate the reply! Ok so I should have mentioned the a/c is a 13500btu. Need to check those exact numbers(my new meter comes tomorrow) The inverter is a 4000w so am hoping it’ll do the trick. I assume locked rotor amps is “in rush amps. “? We’re trying to avoid the generator as much as possible. Have a dc-dc converter 40amp to help charge the batts off the truck but do have small gen in case of emergency. I take it four batts will be a lot better than 3?

 

[Isaac-1]

I recently bought a pair of 200 Ah LiFePo4 drop in batteries for my motorhome, and when making the purchase I splurged a bit and bought a pair of ReBel 200 AH models with smart Bluetooth BMS that were discounted due to being a bit off spec. Even though I just got them installed I feel splurging for the smart BMS with Bluetooth was one of the best moves I could have made as it really does give a lot of information that would otherwise require me to invest in a battery monitor system to have, as well as it lets me do all sorts of fine tuning on the fly, I can even turn off charging and discharging separately from my phone.

 

[Isaac-1]

You are asking if 4 batteries is better than 3, generally yes, but look at the continuous amp output rating on each one you are considering, some 200 AH batteries will have a 100 amp max continuous discharge rate, some will have 150 amp, and a few will have 200 amp.

 

[Rocketman]

Yes inrush covers the locked rotor amps.

Each battery has two important numbers…
The size Ah which is the total amount of power it holds I.e 206ah or 300ah.

The Amps the bms can output. Many are 100 amps.
So four batteries with a 100a bms can put out 400 amps * 12v = 4800 watts *85% inverter inefficiency = 4080 watts. Which is probably the max on your inverter. 4000watts/120v = 33a @ 120v. Hopefully that will be above the inrush and your inverter can handle that amount of power. (Many cheaper ones struggle being ran hard).

Make sure you use class T fuses, and proper sized cable (my guess is one 4/0 or two 2/0 to both positive and negative).

Also make sure you have a good battery monitor (shunt style). (I like Victron Smartshunt, but there are others).

 

[kmbush56]

Hmm, ok great, should be able to find in rush that out soon. The SOKs have 206ah w only a 100a max discharge rate.

EWCS 4 Gauge Premium Extra Flexible Welding Cable 600 Volt​

Is what I bought. Hope that’s good? If not pls let me know I’ll change it, tks. Hoping the slo start will help the in rush situation...?
Ok tks for the T fuses tip, I’ll find those! Ok I need to check the battery monitor, it’s a cheaper one here

bayite DC 6.5-100V 0-100A LCD Display Digital Current Voltage Power Energy Meter Multimeter Ammeter Voltmeter with 100A Current Shunt. Any good?​

 

[Rocketman]

Stop buying stuff before you have everything figured out - that is as great way to waste money on stuff you don’t need.

4 gauge is NOT nearly large enough for parts of your system - other parts it will work. Find the wire size charts ( they are discussed on this site or on the internet).

4 gauge wire will carry between 125 and 180 amps - this wire will be fine between a single battery and a buss bar. Because each battery can only do 100 amps (maybe a little more for 30 seconds). Are you planning on wiring the batteries up this way?

If you are running four batteries - each paralleled - that’s 400 amps at 12v. Go find out what wire will handle that…

Remember you are the system engineer- it is YOUR job to make sure everything is running right and correctly. Make sure you plan and figure everything out first - do the math! We have been assuming you need four batteries- maybe the math works for three batteries. Wire sizes need math behind them.

There are several more aspects of lithium batteries you need to make sure are covered. Many converters that originally shipped with RV will not work correctly with lithium batteries. You need to determine if that’s an issue on your rig.

 

[rmaddy]

4 gauge wire will carry between 125 and 180 amps

I would only use 4AWG wire for 80-100A loads and only if the length is short enough.

If the plan is to run a 4kW inverter then you do not want to do that with a 12V system. The amperage is just too high. 48V would be MUCH better. 24V would be doable.

 

[kmbush56]

Ok tks for your replies! I just started the project..go easy on me, lol . Note: I have watched over 1000 videos tryin to understand this stuff, and I came here to cross check what I’ve been told (double checking is good : )
Ok, that said,
1)The plan was 3-4 206ah SOK batts w 100amp max draw each. (4x100amps)

2) I have a 4000w inverter which was meant to hopefully easily cover the 2750w draw from the A/C (13500 btu) and using a microair slo start to help w the inrush (to be calculated when my meter arrives).

3) I have 4 x 200w Panels in two strings in series, and those 2 arrays are to be paralleled per Will Ps book if that makes sense (didn’t do the math yet.)

4) The rv has a 12v system and really hoping to keep it all 12v if possible. ..

5) I will check the converter I got with the rig. It’s a 2022 forest river 192rbs FEx.
And I’ll change all the wiring to 2ga or whatever the chart says, perhaps I read it wrong. Tks

Anything I might have missed. ..that making sense?

 

[Rocketman]

The wiring needs to be two 2/0 or one 4/0 (two-aught or four-aught). (Need to verify for yourself)
The wire sizes go:
6
4
2
1
1/0
2/0
3/0
4/0
(Then something like MCM…)
So we are talking MUCH bigger wire than 2 or 4 or 6 gauge. It is also hard to work with.

Also read the recent thread about “classT fuse vs anl fuse”. You will want a 400 amp classT fuse just after the battery buss bar.

When working with extreme amps (400 amps @12v qualifies as extreme), really make sure everything is perfect.

Also, if your only large load is the inverter- you would be better of having the battery, inverter, and solar chargers at 24v (or 48v) and then running a 24v to 12v converter to run your 12v stuff. Get a 24v charger (or an inverter/charger) to recharge the batteries off of shore power or generator.

 

[Rocketman]

Also, I would draw up you plans, checking everything- including the size in your camper, and size of equipment. Label each cable for how many amps it will take. Fuses, wire size, approx length, connections to camper, etc.

Drawing it - putting it on paper (or computer) shows where the problems can be.

 

[kmbush56]

Ok, agreed. Plan is coming soon but was looking at diagrams till now. Any place I can find good detailed diagrams for my type of system?
And tks, I noticed it’s not 4/0 I bought but 4gauge. Will exchange for 2/0 for all battery bank and system where applicable.

 

[kmbush56]

Also, I wanted to make it expandable to 1200w

 

[rmaddy]

Will exchange for 2/0 for all battery bank and system where applicable.

Please keep in mind that to handle 400A you need two 2/0 wires in parallel for each connection. A single 2/0 wire is only good for 200A.

Does the manual for your 12V 4000W inverter make any mention of a suggested wire size?

 

[kmbush56]

I haven’t gotten the inverter yet..... :-(