A RC/hobby balance charger is gets my vote. Its what I use for EV batteries and complete pack testing.
Depending on the model/brand there are feature like regenerative discharge and external discharge which can greatly improve the discharge rates for capacity testing. iCharger is known to do this well, I like their units for this type of work and they have various models in different price ranges that can all pretty much do the same thing. Im sure others can too, but I dont have first hand experience.
Balance chargers work well regardless if you are testing a single cell or a complete module as it is balance aware.
Thanks Chrimp daddy
I have an icharger 1010 B+ but the 1010B pdf manual dosen't say anything about regenerative discharge or external discharge, one website selling the 1010B+ has listed under features "external capacity resistor is connected, iCharger 1010B+ produces a maximum discharge power capacity of 280W (@40V/7A)." regenerative discharge has the same.
not sure I want to take a chance on letting the magic smoke out of the charger. it was hard enough getting it into the charger to begin with.
I will look at the other Ichargersand other Rc/hobby balance chargers
Thanks daromer and Geek
I looked and looked for the1010B+ pdf and all I could find was the 1010b pdf and I saw the link that Geek gave but figured it was the same one I had which was for the 1010b model. will look at the other Ichargers
I have an iCharger x6 and love it. I didn't know of the x8 when I bought the x6, or maybe it wasn't available yet. Either way, both are a great choice for testing large format cells or large battery packs. I use it to test my 300p batteries at 30A with the regenerative mode
Discharge is up to 10A, up to 60W (I never used them beyond ~25W). They beep when discharge to a selectable voltage is finished.
Then they display the total amp-hrs and watt-hrsdischarged, and the average voltage.
In between discharge tests I charged the sixteen cells per batch connected in series, using the Chargery BMS-24T, which I found worked quite well. Here is a picture of a stack of pouches being charged:
Note the plastic sheet insulators between alternate electrodes! Also how I numbered the clips I used to extend the Chargery's leads, and a bit of color coding that helped me avoid errors at connection time (as you all know, cell testing can be mind-numbingly tedious and repetitive!). The larger red and black insulated clips are simply joining pairs of + and - electrodes in series; so alternate pouches are flipped upside down.
I recorded the data using a rudimentary OpenOffice ODBdatabase:
This database accepts multiple discharge session entries per cell, using the cells' serial numbers to identify them. So afterwards I could summarize the max, min, and average AH for each cell, from which I develop a sorting list to ensure each "supercell", or block, gets the same average AHrs as the others (I think of this like choosing team members for school-yard sports teams; you want to have an equal mix of strong and weak players on every team).
I have more photos showing a bit more detail of the construction of the discharge rack, in case anyone wants to see.
So to answer the OP's question, these little ebay dischargers worked well for me; and I see there are many new versions available now, with substantially higher power rating, bigger heat sinks and fans, nice enclosed cases, etc.
I managed to check cell voltages on one battery, not too sure how accurate this is hard to hold the negative lead from my cheap harbor freight multimeter on the negative post.
all the vt#'s are printed on the circuit board. just a hair out of balance. Almost half a volt.
These weigh 164 lbs about 80 kg something to remember I am not as young as I once was.