I currently only have NiMH rechargeables, but I assume this will soon change and I'll start using Li-ions also.
I'm looking for budget options to test them. Should I buy separate NiMH and li-ion devices, or is there one device which combines all battery types? Do different li-ion chemistries need different testers? What about NiMH/NiCd/NiZn/other chemistries I'm not aware of? I've seen many of the testers devices also function as chargers, but there are also dedicated capactiy testers - are they more accurate? cheaper?
For li-ion cells you might get an idea using a linear current regulated driver (those who pack AMC7135) maybe a luxmeter and babysitting it with a stopwatch. The general idea is to watch the luxes drop significantly then you have reached the Vf of the led. Better use a XP-G led since they have lower VF. At that time the led goes notceably dimmer the battery voltage should be around 3,3V?!?. For many that is an empty cell already (actually many refer li-ion empty at 3.6V).
The method is silly but you get a good estimate what the cell can provide. aT least that's what i will do not wanting to spend for a hobby charger. For Nimh AA's this method would not be of any use im afraid.
For nimh you could check initial current draw of a flashlight of choice monitor it through the test now and then till the light stops. Use the current average with time to get your capacity. Again this will only be good for a very rough estimate.
Ue a medium mode which does draw usually around 1000mA for less margin of error. You might repeat that a few times and use an average.
That will be good if you want a rough idea of the capacity, for exact measurements this will be no good. Using a salf made contraption that monitor both current draw and voltage of the battery would be best althrough i have no idea how much do you need to compensate having those two multimeters attached. Very impratical and be sure your wife of other better half isn't watching you doing it. That will take care of possible sanity checks and alot of explaining.
if you want to test if the battery is full go for a Digital Multimeter i bought one of these for measuring,did not arrive until now but i could not resist
Looks exactly as one of mine and i've been pleased so far with. No probelm measuring currents above 3A with stock probes. Also reasonably accurate compared to a very expensive Fluke multimeter. Voltage wise almost the same. Current wise about 5% difference which does not bother me at all. Not tested through entire range of application just the usual flashaholic need. VDC up to 20V and DC current setting for up to 10A. Be sure to switch the postive lead holes for required operation otherwise you may damage it. :)
For AA and AAA Nimh-batteries i use the Maha MH-C9000. It has a "refresh/analyze" function to test the batteries. That way you know the real capacity of each cell.
The Maha MH-C9000 is not a low budget charger, but it is one of the best chargers you can buy for AA and AAA Nimh-batteries.
Thanks for the advice, but I want a complete device, not a DIY project...
As for the La Crosse, Maha, Angeleyes and the like - they are all for NiMH only, as I understand.
Maybe what I need is a hobby charger like the iMAX B6? It can be bought in roughly the same price as the NiMH devices mentioned above. It can charge/discharge/show capacity of all relevant battery types, if I understand correctly. Only drawback is that I read not so good reviews about it...
RC hobby chargers are probably the simplest and easiest way to have a capacity measurement device. They range from the 20s to the hundreds, and as always, you get a couple more features in the higher priced ones, but better accuracy, and reliability.
The ones from hobbyking are worth a look at, they offer a wide range, and have a review system in place that helps to seed out the not so good from the really good. If money was not a big concern, the iCharger 106+ is recommended, however their lower cost ones also work fine. The cheaper ones still provide most of the important functions, including capacity. The areas that tend to be lost with decreasing cost are the electrical limitations and tolerances. You may not be able to discharge at high currents (limited to 2.5W say) and the accuracy may reduced, and you may lose the ability to calibrate, however for the flashlight user, they will be very adequate.
Capacity functions should work for all chemistries with hobby chargers given its independent of the type of battery used.
Can I use the iMAX B6 if I don't care for balancing (which I read it doesn't do too well)? It seems to be the cheapest of them all.
Any other suggestions? This is almost only for capacity measurements, or single cell charging - more than that I think I'll use a dedicated charger (already have a GP fast for AA/AAA, and the XTAR WP2 should arrive soon for most li-ions).
The iMAX B6 has some bad reviews. While this will partly be down to it not being the best quality availlable, I suspect the main reason is that due to it's price it vastly out sells any of the alternatives.
I've not tried the XTAR WP2 but I'd be supprised if the iMax wasn't better, it gives you the option to charge your batteries at the right current for each one rather than what ever the fixed current is on the XTAR.
I have three different imax B6 clones - and I've always been suspicious of the mAh results. I have sent a couple of cells to old4570 which I have tested. Hopefully they will arrive soon in Australia and we'll see how Matt's figures compare to mine.
I am afraid that my results may be accurate. If they are accurate then I have a lot of crap cells.
If anyone has a Schulze or iCharger or something with known reliable measurements, I'd be happy to measure an RCR123 (New) or 14500 (Which will be a junk cell) and send it for testing.
I've never actually tried this. I really ought to do so.
I'll check a few cells on all three to them to see what happens. I'll charge all the cells on the same charger so that the results ought to be consistent. Voltmeter checking isn't that hard - so that at least they all start at the same voltage.
I should have done this already but it never occurred to me to do so.
Thanks for the idea!
If anyone can think of refinements to the methodology please do let me know.
I really do want to know.
The variables I can think of are:
Voltage
Temperature
Internal resistance of the cell (I have no way of measuring this but am relying on consistency of the cell over less than 10 cycles)
If anyone can think of any other variables that might have an effect on the result please let me know.
About internal resistance - you might at least diferentiate between them by measuring current for each in a same flashlight under same conditions (voltage, temperature of flashlight).
