testing battery capacity

[gothicsurf]

It's a general question with which most probably do not bother. Does anyone have any thoughts on gauging / testing battery capacity better than a general historical sense after use. The battery I have is from a reseller who has them rated 3Ah over any of the same type that fit in a specific carriage. For an additional battery it would be interesting to test whether the 17Ah battery capacity is appreciably greater than those at 13Ah.

There are dedicated battery capacity testers but inaccessible to most who are not ebike repair shops. Could there be any methods of gauging capacity more precisely than an eventual impression that the smaller battery may seem to last about as long as the '17Ah' one?

 

[amberwolf]

pretty much any "wattmeter" or "coulometer" (coulombmeter) connected between the battery and your system will measure the capacity of the battery as you ride it.

hook it up between charger and battery to measure the recharging capacity (which will be slightly higher from losses and balancing).

some google searches for them

coulombmeter ebike - Google Search

wattmeter ebike - Google Search

i prefer the cycle analyst from grin tech because it also does a bunch of other things for controlling an ebike, and is bidirectional so it can measure current either way, and it remembers everything when powered off (most of them don't do either of those). but i've also used generic rc wattmeters like watts up and turnigy wattmeter which is a clone of the wu and has itself been cloned a bajillion times.