Connect two 12S Packs with different Ah in parallel

so they would just die faster?

No it will stress the cells out… drastically reduced lifespan

Sorry, this is interesting. How exactly does that work? Is the current drawn primarily from the low internal resistance cells and then they get recharged from the other cells? The P-pack will self balance. Current will be drawn from all cells.

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In order to keep the cells at the same voltage they have to discharge at a certain rate, the amp draw is proportional to the capacity

i just read that using diodes would work. ?

I mean I’m not an expert by any means but the load will be disproportional. The highest voltage cells will suffer the most amps, and that may be the lower rated cells

He’s using the same cells in both packs. And it’s is true that when it’s under load, it will draw more from the larger pack. But at cell level, each p should discharge at the same rate when both packs are connected in parallel.

And yes it’s better to use 2 separate BMS and charge them separately. And it’s safer to disconnect the parallel plug when you charge.

the question was, if one could connect 2 x 12S packs with different battery types, eg. 30Q + 35E

Oh. I missed that. In that case he’s absolutely right. It will discharge evenly but how much it damage the cells still depends on how many Amp each pack discharge.

Like @Pedrodemio said in my thread, you would need both packs to be charged to a perfect 100% before being connected. The pack that is the Extra Range pack would them need to be connected through the pack on the boards charger port. The charger port on the board would NEED to be connected to a bms. This would then work as a XR battery pack. Until the one day you forget to charge both to 100%…

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Sure, but I can’t really see how that would be a problem as long as the difference in the capacity isn’t extreme. I imagine mixing up 30Q and 30E would be fine (though maybe the different C rating rather than different capacity would cause trouble). Also, it looks like @directC is considering using a big battery (22P?) so the load per cell would be pretty low.

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That’s a fair point, that pack should be fine to draw 200A and I can’t imagine you’d need more than 10kW for a skateboard

Exactly, it’s not needed to be perfectly, 1v of diference is perfectly fine

And about two different cells, since most Liion cells have a similar low voltage limit, it should be fine, but it’s always good to keep and eye on it

If your main cell can take the current you set on the vesc, by joining another one you are only decreasing the load

Yes, but as I said, if you normally use your main pack, with the currents dialed in for it, and connect a different one, it will not get stressed, on the contrary it will be less stressed

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Yep, to be sure, calculate the internal resistance of both complete packs, and check how the current will be distributed between them, if it’s bellow the limit of both packs go ahead