Bottle battery cell count


New Member
United Kingdom
I've been given a 36V bottle battery by someone who no longer has the bike. I've taken the casing off to check it and was surprised to see that there appear to be two empty spaces for cells, so was concerned someone might have removed the cells leading to an unbalanced battery.*

There are three round layers, each of which has positions for 14 cells. The top layer only has 12 cells installed though, the bottom one has 14 and I can't see the middle layer. There are no signs that cells were ever welded to the links in the empty positions. The connection links are complex, there are links and wires and I can't see them all, so it would take hours to work out the connections and some of it would be guesswork.

I'm assuming that the middle layer has 14 cells, making 40 in total, and they are wired in 4 sets of 10. 10 in series would make 3.7 x 10 = 37V nominal - about right. If they were 2500mAh batteries, 4 sets in parallel would be 10000mAh or 10Ah - about right.

So it all adds up, it just seems a bit odd to make a battery holder with empty spaces. I suppose it might be the only practical combination in that shape. I'm inclined to assume the battery is OK, am I right to do so?

(*I'm checking it because it has a long history! I won't bore you with that unless you need some of these statements explaining.)


Well-Known Member
You're correct. There are 40 cells arranged 10 x 4, That is ten series groups with 4 cells per group in parallel. often called 10S-4P. The AH rating is P x the Ah of the cells, And 4 x 2500mah gives you 10000mah or 10Ah,
40 cells ÷ 3 layers = 13 1/3 cells/layer, . So you will see two layers with 13 cells and one with 14.