Two different lifepo4 battery Amp hour ,135 ah and other 100 ah connect in parallel .

[mrel]

Hello

(1) lifepo4 battery lithium iron phosphate , four cells connect series in each cell 3.2 volt at 135 amp hour give total 12.8 volts , now if connect another set of battery in parallel lifepo4 iron phosphate battery rate at 3.2 volts at 100 amp hour .

(2) If one set of battery rate 135 ah and the other rate at 100 AH and connect in parallel would still get more amperage?

mrel

[SunEagle]

Hello

(1) lifepo4 battery lithium iron phosphate , four cells connect series in each cell 3.2 volt at 135 amp hour give total 12.8 volts , now if connect another set of battery in parallel lifepo4 iron phosphate battery rate at 3.2 volts at 100 amp hour .

(2) If one set of battery rate 135 ah and the other rate at 100 AH and connect in parallel would still get more amperage?

mrel

You will get more amp hours if the batteries are the same voltage and if you wire them in parallel but the issue is that they probably will not charge or discharge equally. So one of them will not last as long since it will cycle more than the other.

[Ampster]

There will be eddy currents between the different packs as the voltages equalize between the packs.. The additional cycling may not be as severe as with Pb since the discharge curve is much flatter and there is no Peukerts. Some users on other forums have reported good luck with mixed sizes of lithium packs. Maybe it is too soon to tell.

[SunEagle]

There will be eddy currents between the different packs as the voltages equalize between the packs.. The additional cycling may not be as severe as with Pb since the discharge curve is much flatter and there is no Peukerts. Some users on other forums have reported good luck with mixed sizes of lithium packs. Maybe it is too soon to tell.

I agree. Some different battery chemistries will act better than others. Hopefully the Li Fe does better.

[Ampster]

I agree. Some different battery chemistries will act better than others. Hopefully the Li Fe does better.

I should have clarified for the most part I was referring to LFP (Li Fe) cells. When you consider that even a 100 Amp prismatic LFP battery consists of several pouches in parallel then adding another group of parallel pouches makes little difference unless you are talking about big differences in capacity. 100 vs 135 Ahrs is not considered big. The other assumption is that there should be a separate BMS on each pack to keep the cells balanced within the pack. That is another reason that paralleling LFP cells is less problematic. The BMS offers some risk mitigation and monitoring current for each pack can tell you if eddy currents between packs is excessive.

[PNjunction]

SunEagle is exactly right. While you would get additional capacity, the smaller capacity one would be worked harder and not last as long.

This is basic battery stuff, not LFP specific. Same rules.

In fact, the guys over at wheelchairdriver who have converted to LifePo4 for their chairs, have constructed what they call "Add-Ons" such as these. They give additional range, but of course they don't last long because they get hammered.

Gotta' hand it to those guys - they *SIT* on top of their LFP banks, not like us lounging on the couch with the batt in the garage.

Different application though - they use LFP energy cells, and not power-cells like we do for sub-c applications (ie, your typical cheap plastic prismatic is right out for their use)