How close do lipos have to match to be run together?

[MikeP323]

When running two 3S or a 3S and a 2S (I use these in series) I have always run the same manufacturer, the same Mah and the same C ratings together.
I am wondering if perhaps say a 7.4V 70C 5500Mah would be compatible with a 11.1v 70C 5000 Mah. I have been told that mah is akin to fuel in the tank?
I usually run my ESC's on Auto cell count and with zero protection but I NEVER run more than four or five laps on an approx 1/8th mile course.

Does they always have to identical ? Are Mah and C rating equally important? Thanks for any info anyone might have.

[Fluid]

Running packs with different capacities risks over-discharging the lower capacity cells because the LVC only knows the average voltage of the packs supplying it. The lower capacity packs may also run hotter than the higher packs. As long as you only discharge the lower capacity pack down to 60% then you should be safe. Personally I only run identical packs in series.



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[Erroneous]

Just to add to Fluids response. The 5500mah pack will try to charge the 5000mah pack to 5250 while wired in series. Once the circuit is complete aka plugging into the esc. Im with him, I only run the same mah, c, manufacturer and age packs together.

[zooma]

Just to add to Fluids response. The 5500mah pack will try to charge the 5000mah pack to 5250 while wired in series. Once the circuit is complete aka plugging into the esc. Im with him, I only run the same mah, c, manufacturer and age packs together.

I don't follow this. I know that current flows from a higher voltage to a lower voltage. But you are saying that it also flows from a higher capacity to a lower capacity. I question that.

[NativePaul]

You are right to question that, it is BS.

[MikeP323]

Thanks Guys - I guess the safest thing to do is continue with totally matched packs as I was doing.

Thanks for the replies.

[Erroneous]

I stand corrected. And thinking about it now, makes no sense. If the mah exchange where true the lower mah pack wouldn’t run out first.