Mixing Lifep04 and Li-Ion

[gvastardis]

Hello,

New here but long time lurker of the forum.

Im putting together a battery bank now that will have both LG Chem Server Rack Lithium Ion batteries and Lifep04 Server Rack batteries from Signature Solar. I just ordered the BMS from Battery Hook up and soon as they get there I will set them up on the LG Chem Batteries.

The LG chem are 189ah @ 51.2 volt and the Signature Solar are 100ah @ 51.2 volt

With that being said i am mixing two different chemistry batteries with two different capacities. Does anyone have any experience doing this?

Ive thought about this 100 times over and in my mind i cant see why there would be any issues with a good BMS. The packs will obviously connect and disconnect at different times but maybe I am wrong.

Any input would be greatly appreciated.

 

[MisterSandals]

Lifep04

Not a battery chemistry.

i am mixing two different chemistry batteries with two different capacities.

I cannot imagine this working out, especially without knowing what you are doing.

This might save some time in the future:

Up in smoke... learn from my mistake!

Did your experimental battery or home built inverter experience a rapid, unplanned disassembly? Reverse polarity a $3K inverter, and see it go up in smoke? Share it here!

diysolarforum.com

 

[gvastardis]

Not a battery chemistry.


I cannot imagine this working out, especially without knowing what you are doing.

This might save some time in the future:

Up in smoke... learn from my mistake!

Did your experimental battery or home built inverter experience a rapid, unplanned disassembly? Reverse polarity a $3K inverter, and see it go up in smoke? Share it here!

diysolarforum.com

Let me further clarify. LiFePo4

How do you know it wont work out. I am placing both sets of batteries on a common bus. Two different batteries with two different capacities.

 

[MisterSandals]

LiFePo4

LiFePO4 ... less Po (polonium) more PO4 (phosphate... one phosphorous, 4 oxygens)

How do you know it wont work out. I am placing both sets of batteries on a common bus. Two different batteries with two different capacities

I do not know but I am pretty sure any manufacturer would say not to, for legal liability reasons if nothing else.
I wouldn't do it, especially in my own home but these guys have done it:

mixing LifePo4 and LI-ION packs

Hey guys, Long time listener first time caller. I recently upgraded to a pair of the LG ESS packs(14s 189ah LI-ION) and I have my old pack (16s 172ahLifePo4). I have no real use for the LifePo4 cells and was wondering if I could put them in parallel. with the LifePo4 discharge being much flatter...

secondlifestorage.com

Mixing lipo and lithium ion batteries

Lithium ion batteries have high specific energy and lipo have high c rating (high power). Is it possible to put lipo and lithium-ion batteries in parallel if they are at the same voltage and protected by charge control or BMS circuitry? This would give you a battery that has high energy density...

endless-sphere.com

Note that LiFePO4 is fairly benign but Li-ion and LiPo are explody when things go sideways.

 

[RCinFLA]

LG chem are 189ah @ 51.8 volt and the Signature Solar are 100ah @ 51.2 volt LiFePO4.

LG Chem cells are likely 14x 4.2v to 3.0v (58.8v - 42.v) operating range. LiFePO4 cells are 16x 3.65v to 2.5v (58.4v - 40v) operating range

51.8v / 3.7v per cell is 14 cells in series. 51.2v / 3.20v is 16 cells in series.

These are not compatible. The two arrays would be at significantly different state of charge for same net array voltage. The LiFePO4 have a flatter discharge voltage curve than the LG Chem batteries. The voltage ranges do not tell the whole story. In parallel the LG will initially supply much of load current then later in discharge cycle LiFePO4 will dominate current supply.

 

[gvastardis]

LG chem are 189ah @ 51.8 volt and the Signature Solar are 100ah @ 51.2 volt LiFePO4.

LG Chem cells are likely 14x 4.2v to 3.0v (58.8v - 42.v) operating range. LiFePO4 cells are 16x 3.65v to 2.5v (58.4v - 40v) operating range

51.8v / 3.7v per cell is 14 cells in series. 51.2v / 3.20v is 16 cells in series.

These are not compatible. The two arrays would be at significantly different state of charge for same net array voltage. The LiFePO4 have a flatter discharge voltage curve than the LG Chem batteries. The voltage ranges do not tell the whole story. In parallel the LG will initially supply much of load current then later in discharge cycle LiFePO4 will dominate current supply.

I realized that but i figured the bms would disconnect when the capacity of the smaller bank ran short.

 

[Ampster]

i figured the bms would disconnect when the capacity of the smaller bank ran short.

Those two chemistries have different shaped discharge curves. I would never mix them because a lot of energy will be flowing between the packs as physics tries to equalize the voltages as they discharge. I would also not want to overwork my BMS to compensate for the different capacities.
Let us know how it works out.

 

[gvastardis]

Those two chemistries have different shaped discharge curves. I would never mix them because a lot of energy will be flowing between the packs as physics tries to equalize the voltages as they discharge. I would also not want to overwork my BMS to compensate for the different capacities.
Let us know how it works out.

Ive seen a number of threads of ppl who have done it. Most importantly i dont want an unsafe situation. I hate to do it but i think ill have to sell the LG's

 

[gvastardis]

@Will Prowse will you do a video discussing this?

 

[BigGun]

I've thought about using a Li-ion battery bank connected to a charger to charge my Lifepo4 battery bank in power outage situations , but not permanently hooked up

 

[Ampster]

Ive seen a number of threads of ppl who have done it.

No doubt people have done that. Did they explain the issues and offer advice about how to optimize the situation. Sometimes experiments like that are like gambling stories. People always brag about their winnings and rarely brag about all the losses it took to get there.

 

[gvastardis]

No doubt people have done that. Did they explain the issues and offer advice about how to optimize the situation. Sometimes experiments like that are like gambling stories. People always brag about their winnings and rarely brag about all the losses it took to get there.

Has anyone successfully made two banks of different chemistry batteries with some type of switching mechanism?

I really want to figure out how to do this safely so i dont have to sell any of these.

 

[Bvillebob]

I believe Steve_S has a lead/acid and a lithium he switches bck and forth, not used at the same time. Not sure how he handles the different charging parameters, you might want to message him.

 

[Shinebox]

I believe Steve_S has a lead/acid and a lithium he switches bck and forth, not used at the same time. Not sure how he handles the different charging parameters, you might want to message him.

You can mix lithium and lead because they can be set up to compliment each other and make up for inherent weaknesses in each chemistry. As far as the OP, you seem to be seeking approval for what you’ve set out to do, however RCinFLA I think has distilled the obvious issues with what you’re proposing.

 

[HighDesertOffgrid]

With that being said i am mixing two different chemistry batteries with two different capacities. Does anyone have any experience doing this?

I have had a 7s 23p li-ion (about 55ah) connected to my lfp batteries for about 18 months. Of course, it has it's own 20a bms and is fused. No ill effects thus far.

 

[RCinFLA]

You can do it but must consider that each battery type contributes a difference percentage of load or charge current depending on where it is in its SOC discharge curve.

To stay safe, you should assume only one of the batteries' types is taking most of current, restricting discharge and charging current to the limit of the lower of the two types, with no sharing of the load/charge current between batteries. You won't get higher current capability with the two in parallel but will get more overall AH capacity.

 

[Goboatingnow]

LiFePO4 ... less Po (polonium) more PO4 (phosphate... one phosphorous, 4 oxygens)

I do not know but I am pretty sure any manufacturer would say not to, for legal liability reasons if nothing else.
I wouldn't do it, especially in my own home but these guys have done it:

mixing LifePo4 and LI-ION packs

Hey guys, Long time listener first time caller. I recently upgraded to a pair of the LG ESS packs(14s 189ah LI-ION) and I have my old pack (16s 172ahLifePo4). I have no real use for the LifePo4 cells and was wondering if I could put them in parallel. with the LifePo4 discharge being much flatter...

secondlifestorage.com

Mixing lipo and lithium ion batteries

Lithium ion batteries have high specific energy and lipo have high c rating (high power). Is it possible to put lipo and lithium-ion batteries in parallel if they are at the same voltage and protected by charge control or BMS circuitry? This would give you a battery that has high energy density...

endless-sphere.com

Note that LiFePO4 is fairly benign but Li-ion and LiPo are explody when things go sideways.

LiFePo4 is Li-ion. They all are.

 

[cs1234]

@Will Prowse will you do a video discussing this?

I wouldn't think he would. He has mentioned his current preference for LiFePO4.