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Mixing different LiFePO4 Batteries

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SeanVincent

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currently have a 24v MPPTSolar setup with two BB 12v 100Ah batteries in series (thx Will designed to your specs). These run as a glorified battery backup for my key home electronics. Adding solar panels this month.

With recent power outages would like to double capacity. Looking at adding (in parallel) to the existing system two Lion Energy batteries in series.

is this a good or bad idea? Seeing mixed thoughts on this.

links to the Lion Energy specs:UT-1300
Existing BB specs: BB10012

appreciate any and all feedback. Able to procure the Lion Energy for $700 and seems a good deal.
 
I’m not an expert, but Info from Lion Energy indicates that batteries in Series need to be matched, but batteries in parallel can be different, so the installation you describe should be OK
 
Spoke with BB & Lion they both told me no even in parallel. I see people do it though.
 
Both mentioned BMS concerns. At the time I had Renogy's 100ah battery (last years model) I wanted to add 2 of their new Smart lithium and they said don't do it....really?! So then I called BB & Lion, they also didn't recommend it. Probably just wanting to sell me more batteries maybe. From what I've observed and read I would feel comfortable having similar batteries (12v 100ah) from different companies in parallel. In my case, I had a use for my Renogy so I bought 3 Lions.
 
OK so when I searched OCPD acronym I came up with Obsessive - Compulsive Personality Disorder, thought about it a minute I'm thinking Over Current Protection Device. Am I close? Sorry I'm new.
 
Will Prowse said:
Over current protection device
Click to expand...
Pretty much the same setup as the solar shed. Think the concern is using the built in MPPT charger in the MPPT Solar unit vs a third party tied on. Appreciate everyone’s input. Tying in the solar panels this weekend and hope to power key home devices moving forward.
 
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I think in theory you can do that with any type of battery, as long as they are all the same type, and thats mainly just based upon cell voltages.

LIPO/NMC/traditional lithium formulas operate at 3.7V/cell
LifePO4 is at 3.2
LTO is like 2.8

Stick in the family and you should be ok!
 
madmax said:
I think in theory you can do that with any type of battery, as long as they are all the same type, and thats mainly just based upon cell voltages.

LIPO/NMC/traditional lithium formulas operate at 3.7V/cell
LifePO4 is at 3.2
LTO is like 2.8

Stick in the family and you should be ok!
Click to expand...
So are you implying I can't mix my 16s 48v Nissan leaf battery banks with a 16s 48v lifepo4
 
Will Prowse said:
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.
Click to expand...
I could use some further advice and/or explanation on this please.

I have 2 x 100ah BB's in my camper (travel trailer) with solar and the whole camper runs through a 3kw inverter. Everything's wired either 12vdc or 120vac (just like the camper was set up from the factory) to make it simpler ... at least for me. Batteries are wired with 4/0 cable. Assume the max draw out of the batteries for short bursts of time.

I'm adding 2 x 100ah SOK batteries (they just got delivered). How do I do this?
- Wire 2 x 200ah in parallel (12vdc) banks and tie them into the system?
- Wire 4 x 100ah in parallel (12vdc) and then tie them into the system?
- Wire 4 individual batteries up to a junction block?

And then ...

- What OCPD (over current protection device) should I use.
* What current limit size.
* Should I put one on each battery, each bank of 2 or after all 4?

I hope I'm making a mountain out of a mole hill but I want to do this right (or as right as I can).

thanks,
john
 
Batteries in series need to be matched. Not good to mix old and new cells in series.

As LFP cells get older their terminal voltage slump (or charging terminal voltage rise) will get greater for given cell current. If you want to check this you have to put a moderate load current (0.2-0.3 CA) and wait a minute or two for terminal voltage to level off and reach equilibrium for the given load current. It will also take a minute or two for battery rested open circuit voltage to recover after load is removed.

If you add two new series 12v batteries, do it as if you are adding another parallel 24v battery with original. Do not strap the middle 12v battery connections between the two 24v strings together.

You will likely not get perfect current sharing on the two 24v batteries. If you have a clamp on DC amp meter periodically check how the total inverter load current is being divided between the two parallel batteries. If you are less than 20% variance consider it good.

Just have to make sure you don't draw excessive current or charge current on one series string. You may see the current sharing change over the state of charge. Usually the newer battery will be providing more of the inverter power initially then as its capacity is consumed the older battery will supply more of the inverter load current.
 
I have the same novice problem. I bought a 24V battery then I found out that the MMP solar unit got (the hybrid green 2.4K watts thing) works better with two batteries?

Not because I got the wrong voltage. It’s just the two videos I have seen they use two 24v batteries, for optimal use of the inverter. So I go buy a second of the same brand and distributor and it’s $400 more for the same thing a month later.
I got the first battery from PLX devices based in Cali (so be aware). So can I get any other battery of any brand? As long as it’s also 24v and hook them up parallel?
 
Will Prowse said:
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.
Click to expand...

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..

Thanks in advance
 
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.
 
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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.
 
jrcromer said:
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.
Click to expand...
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.
 
Will Prowse said:
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.
Click to expand...
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
 
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