Mixing different LiFePO4 Batteries

[jrcromer]

Fortress here. Do you have a need for additional power as well as additional battery capacity? Best bet is to get a small 48V inverter and use a cascading system architecture (ie ac coupled grid to load to grid to load). Lots of “obsolete” 48V battery inverters are perfect for this. If not, fill out a support ticket every now and then and request a refurb unit for expansion. We don’t usually have them available, but we do get them from time to time.

Edit: Will has offered differing advice on this. The DIY crowd is usually more adventurous than manufacturer warranties allow. But BMS units are intended to play defense, not offense. I’d look to the solar industry for guidance on this - are 200W modules allowed in parallel with 300W strings on the same MPPT? What about in series? Series is worse than in parallel, but that doesn’t mean parallel is allowed.

 

[WoodySolarVan]

Any battery config you want to match as close as possible AH. Rule of thumb for lead acid is if adding batteries to existing bank new battery should be within six months to a year of existing.


It's like having a tv remote and removing only one battery and replacing it with a new one - leaving the other. Sure that might work but overall capacity is reduced etc etc... Get as close to ah with new battery as possible. Regardless of brand.

 

[itsbana]

Fortress here. Do you have a need for additional power as well as additional battery capacity? Best bet is to get a small 48V inverter and use a cascading system architecture (ie ac coupled grid to load to grid to load). Lots of “obsolete” 48V battery inverters are perfect for this. If not, fill out a support ticket every now and then and request a refurb unit for expansion. We don’t usually have them available, but we do get them from time to time.

Edit: Will has offered differing advice on this. The DIY crowd is usually more adventurous than manufacturer warranties allow. But BMS units are intended to play defense, not offense. I’d look to the solar industry for guidance on this - are 200W modules allowed in parallel with 300W strings on the same MPPT? What about in series? Series is worse than in parallel, but that doesn’t mean parallel is allowed.

Hey @jrcromer Thanks for the response. I occasionally have need for more power (when charging EV) but always need more battery capacity. The Solark 12k inverter i have wasnt marketed clearly and it expensive to parallel another one right now.

I have made the request for the refub so thanks for that suggestion. Finger crossed it works out.

 

[Logic28]

Yeah, LiFePO4 in parallel is fine. Just ensure each parallel string has OCPD and that they are top balanced before being connected together, and it should work great.

Sorry Pls read below

 

[Logic28]

Yeah, LiFePO4 in parallel is fine. Just ensure each parallel string has OCPD and that they are top balanced before being connected together, and it should work great.

Would it be better to add a BMS between the two different brands in parallel or would it be just a waste ? and, BTW, I don't seem to find an DC OCPD rated 100A. Thanks

 

[ChillnGrill]

I have 6 eg4 lifepower4 rack batteries and want to add more. Can I add trophy rack batteries to my eg4 rack of batteries to give me more AH's?
And do they need to be the same AH ie 48v100ah

 

[fopoku2k2]

I am successfully running power walls of different AH's but the same voltage (48v). I am running 3 power banks.
1.0 48v 280AH grade B,
2.0 48v 280AH grade A and
3.0 48v 160AH grade A

off-grid garage on youtube has also been running mixed AH's in parallel.
Will Prowse also has videos on youtube about mixed AH's in parallel

 

[Logic28]

I am successfully running power walls of different AH's but the same voltage (48v). I am running 3 power banks.
1.0 48v 280AH grade B,
2.0 48v 280AH grade A and
3.0 48v 160AH grade A

off-grid garage on youtube has also been running mixed AH's in parallel.
Will Prowse also has videos on youtube about mixed AH's in parallel

Many Thanks for your input, I am waiting for two batteries to arrive and I'll do the same

 

[furiousgeorge]

Good info here, but would like clarification...

I have a 9mo old 12v,100ah battleborn and would like to expand capacity. Can I safely add pretty much any matching chemistry, voltage, and capacity battery in series? Say a 12v, 100ah renogy lifepo?

Thanks!

 

[clydeps]

. Can I safely add pretty much any matching chemistry, voltage, and capacity battery in series?

No. Series connection of identical batteries is possible, but different batteries, even if the same nominal capacity and chemistry, will have differing internal resistance. What is likely to happen is that you will end up with one battery reaching 100% charge before the other, but the current won't drop because the other battery is still accepting charge. The BMS might try to cope with this by bypassing current but that's not what the BMS is designed to do.

So it might work, but it's risky.

Putting batteries in parallel OTOH is pretty safe if you stick to the same chemistry. If one battery reaches full charge (or discharge) before the other the current simply flows to the battery that still wants it. Even different capacities in parallel will work ok. What will happen is that during the charge cycle one will suck more current and charge faster, but the other will catch up towards the end. Same on discharge.

I have a 9mo old 12v,100ah battleborn and would like to expand capacity.

Surely you would do that by adding a battery in parallel anyway? If you put them in series you need to change everything else from 12 to 24V anyway. Doesn't make any sense to me.

 

[proost]

Yeah, LiFePO4 in parallel is fine. Just ensure each parallel string has OCPD and that they are top balanced before being connected together, and it should work great.

Based on @Will Prowse comment, how should I top balance off-the-shelf 12V 100ah batteries before connecting them to an existing bank? I saw plenty of information on DIY batteries and top balancing cells but I didn't find anything re: "Plug-n-Play" batteries like BB/Lion/Redodo/Zoom. I currently have an eight 12V battery bank in a 24V config made up of Lion Energy batteries. Six are UT1200s (three pairs) and two are UT1300s. I used to have eight total UT1200s but a post detached from the case of one and Lion Energy sent me two new UT1300s connected in series and then paralleled with the rest. I just charged them up and connected them per their instructions.

Today, I picked up two Redodo 12V 100ah batteries that I'd like to add to my Lion Energy bank but now wondering if I need to do something more than just charging them full using a regular 12V battery charger before connecting them to the bank. They have an installed BMS with OCPD but not sure about the whole top balancing process or if I need to do it.

Thanks so much for the assist.

 

[Will Prowse]

Based on @Will Prowse comment, how should I top balance off-the-shelf 12V 100ah batteries before connecting them to an existing bank? I saw plenty of information on DIY batteries and top balancing cells but I didn't find anything re: "Plug-n-Play" batteries like BB/Lion/Redodo/Zoom. I currently have an eight 12V battery bank in a 24V config made up of Lion Energy batteries. Six are UT1200s (three pairs) and two are UT1300s. I used to have eight total UT1200s but a post detached from the case of one and Lion Energy sent me two new UT1300s connected in series and then paralleled with the rest. I just charged them up and connected them per their instructions.

Today, I picked up two Redodo 12V 100ah batteries that I'd like to add to my Lion Energy bank but now wondering if I need to do something more than just charging them full using a regular 12V battery charger before connecting them to the bank. They have an installed BMS with OCPD but not sure about the whole top balancing process or if I need to do it.

Thanks so much for the assist.

Just charge them to full and you should be good to go. Top balancing in those packs will occur automatically and over a few months of cycling

 

[proost]

Just charge them to full and you should be good to go. Top balancing in those packs will occur automatically and over a few months of cycling

Perfect! Thanks Will. Any issues with age difference between batteries? The UT1200s are four, the UT1300s are new and of course these Redodos. Lion Energy didn't seem to have any issue with adding the UT1300s but there's a lot of information out there about not mixing batteries of different ages. I can imagine have batteries of different ages in series but in parallel?

Edit: I think I found my answer in another thread. DISREGARD!

 

[KMac55]

Hi Everyone,

I have an issue where I bought a LIFEPO4 Fortress Evault (Was an arm and a leg) but now I see where I need some more capacity as the evault is 18.5KWh and I really need maybe an additional 10 as a buffer. That being said I can't afford to buy another evault right now so was wondering if I could get two eg4 batteries and parallel them with the current Fortress one.

I would then have the 370ah Fortress
and then 200Ah EG4

Is that something I can do.. the installers are saying I must use another Fortress battery but I wanted to seek a second opinion.

From the quoted statement im thinking Will means If I have both batteries top balanced I should be able to connect them in parallel and have 570ah of batteries..

How do you assess credibility between Prouse's rational explanation based on real life data, and messages from highly motivated battery salespeople?