Add a 50Ah LFP to a 100Ah LFP

[MachineYearning]

I have an existing solar system in a small camper that uses a 100Ah Renogy LFP and 200w of solar. It runs everything fine, mostly. I also would like to use my Engel fridge in my car for occasional overnight trips.

It would be very useful if the 50Ah portable system I build for the car could also be used in the camper to add capacity during the shorter winter days.

tl;dr Can you use two different sized batteries of the same chemistry (LFP) from different manufacturers? Not happy with past Renogy interactions.

I got this idea when I saw several YouTubers building expansion packs for Bluetti, Ecoflow and the likes. Those cells aren’t matched for sure, but they also aren’t wired directly together either. Given they are capable of charging from multiple sources.

Thank you for your time.

 

[MisterSandals]

Can you use two different sized batteries of the same chemistry (LFP) from different manufacturers? Not happy with past Renogy interactions.

By "use" do you mean connect in parallel?

If so, the short answer is yes but it won't charge and discharge evenly. Make sure the battery makers say they can be paralleled (because of the possible increased amps and the BMSs).

I would consider using them separately if possible. And I'd consider using a hobby charger like a BattGo ISDT to easily charge one from the other (charge from portable to camper battery) and back if/when solar tops off camper battery. Just a thought. I love little hobby chargers like this for moving power between batteries.

 

[MachineYearning]

Yes parallel. I had envisioned just connecting the batteries with XT60s, but just plugging the fridge into the little guy saves some amps on the big battery.

Full disclosure, everything was fine till the wife ordered a portable induction burner. Very appealing to not have to get out or ventilate in cold weather to make coffee and I would love to ditch propane. I can use it as much as we need when the sun is out but our last trip was way up in Washington state with less than ideal sun.

Furiously googling the dingus you suggested. I can charge a portable battery in the truck, which has a built in inverter. The camper is a slide in and I have been trying to keep it as stand alone as possible with the idea of it being fully functional off the truck.

Again, many thanks.

 

[MisterSandals]

Furiously googling the dingus you suggested.

Amazon.com: ISDT T8 Battgo Lipo Battery Balance Charger Discharger 30A 1000W DC 2-8S LCD Display Digital Smart Battery Balance Charger for Li-Po Li-Hv Li-Ion Li-Fe NiMH Ni-Cd Pb : Toys & Games

Amazon.com: ISDT T8 Battgo Lipo Battery Balance Charger Discharger 30A 1000W DC 2-8S LCD Display Digital Smart Battery Balance Charger for Li-Po Li-Hv Li-Ion Li-Fe NiMH Ni-Cd Pb : Toys & Games

www.amazon.com

Not available anymore but they have bigger and better ones.

I have thousands of Ah of charging off of it. I have solar charging a 206Ah LiFePO4 bank continuously.
From this bank i charge all my utility batteries and individual cells.
I have been charging 280Ah cells (at 1S 3.6V) around the clock for about a week for my capacity testing. Its a worker!

 

[JoeHam]

Absolutely you can parallel them as is.

Don’t over complicate this.

Just be sure to have them at the same Voltage when you parallel them and you will be fine.

The off grid garage did a video where he parallels a 5 Ah with a 280 Ah battery and had no problem.

Each battery contributes what it can to a load and absorbs what it can from a charge while they stay at the exact same Voltage since they are in parallel.

Easy peasy.

Edit: It was a 304 with a 5.

See here :