Maybe I should've qualified that statement just a bit instead of throwing it out there....Originally Posted by Acetronics
In my experience (which I know isn't as much as some, more than other, but it's enough for me), whether I'm using a constant voltage source or a constant current source (or even a plain 'ol wall wart power supply), when you shut off the charger, immediately afterwards, the battery voltage is quite high, then starts to drop off a bit as the battery 'self equalizes'. And it seems to me that the rate at which it does this 'self equalization' business is always changing a bit different because of temp, age, how far discharged the battery was in the first place, etc.etc. I could never get decent, repeatable numbers on the graph (I whipped up a voltmeter with an RS-232, imported data into a PC, put them into a spreadsheet and tried a few things out a few years ago on NiCads and NiMH when I was working on the P/S for my mp3 player).
What did seem to work for me, and was fairly repeatable, was just to watch the battery volts while keeping the charger on. I kept an eye on the negative delta-V. I had options in the firmware to switch from NiCad to NiMH modes to vary the amount of negative delta-V before shutting off the charger. Then, I'd let the battery sit for an hour without a load, let it do it's 'self equalization' thing. Then I'd connect it to a load resistor while plotting the discharge voltage. This seemed to be repeatable and accurate enough for me. One thing I never did do was to hook up a thermistor to check for a large delta-Temp. As you may well know, temp is one thing that'll easily tell you if you're on the verge of an overcharge or not.
When I first started the project, I tried it thinking that checking the battery voltage with the charger disconnected was the way to go. But, like I said, the voltage drop just wasn't repeatable and I'd end up with a 1/2 charged battery packs.
So that's my thought process. As far as newer battery charging technologies and methodology...well, that's all fine and good and it just may be that much better...but...what I ended up with worked and the numbers (mAh on the load resistor, etc.) seemed to work for me...and...it was simple...which I think was the main key!
I just did a quick search on 'reflex' charging. At first glance, it looks like the only people that are 'FOR' reflex charging are the people trying to sell chargers...and the people saying it's crap are the university's, researchers, etc. I'll keep looking, don't have enough information to base an opinion yet...
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