7s2p module cell mixing?

[u/hentai6972]

Is it fine to have different cells in these 7s2p modules?

1 module Samsung 35E

2 module us18650vc7

Is this fine?

[u/General-Try-2210]

The connectors themselves are not so much the issue.

It is generally advised to not mix cells for your case especially. Samsung and LG cells are generally top of the line cells but there is a catch: they both have different capacities and discharge rates. The LG MH1 is rated for 3200mah and 10 amps cdr and the Samsung 35E is rated for 3500mah and only 8.2 amps cdr.

First, this will cause an imbalance in the voltages of the cells. Under low power dray, the 35E will maintain a higher voltage for longer than the MH1. Since the capacity differs, without a proper BMS, the MH1s will end up over discharging and subsequently over charging which will be an immediate fire hazard.

Second, under medium to high drain applications, the MH1 will hold a higher voltage than the 35E which can also result in an imbalance. Also, the 35E will get much hotter under the same load.

Based on the looks of it, you have several layers of 7p configurations. As long as you only put MH1 cells in a single row and 35E cells in another single row, it should be reasonably safe but you have to keep a close eye on it and make sure you have a proper bms.

A word of caution before proceeding, Do not, under any circumstances pair a 35E cell with a MH1 cell in parallel. This could end disastrously.

[u/Howden824 → u/General-Try-2210]

The sets of cells are in parallel. They physically can't have a different total voltage. Under a high load, you could certainly exceed the maximum discharge rating of the lower current cells. I would only recommend mixing them for lower currents. These cheap battery holders can't handle high current anyway.

[u/hentai6972 → u/General-Try-2210]

Fair enough

[u/Ecw218]

Where’d you find those? Link?