Re: Charging NIMH Batteries - Getting HOT in Charg
doesnt your RS charger have 8 Cell slots. they are all wired in series, so they are all getting the same blast, but then you still (somehow) have to temp monitor 8 batteries. because they are all imbalanced , so they will all heat different, because they are not all charged yet.
I have a charger that does the vdrop and charges each of 10 cells seperate, shutting each off as they are (alegeldy) charged. it would need 10 seperated curcuits.
which brings up another pet peeve, and that is series charging, even 2 cells in series charging, never get "rebalanced" making thier out of balance further off.
UNLESS they are slow overcharged. (or discharged prior)
with very SLOW overcharging, series charging in 2x chargers, and 8x chargers , or Best example, power tool chargers, they can re-balance the cells.
I have good luck with a charge rate that is so slow, it is speced for the overcharge rate (or lower). at that slow charge rate, i dont get bulge, overheat, or venting.
so is the worlds stupidest charger, the best one?
(if we cant make the worlds smartest)
BUT, trickle charging isnt the best, to reassemble the plates, and get the stuff out of the electrolyte, a HARD FAST charge for the first 80% is best (if you can ALWAYS prevent ANY overcharge of any sort, and dont overheat).
AND
slow long permanent trickle, or overcharging , is not so good either, I might choose it over the Vdrop method (and its flaws and misses), but its not great either.
then PULSE charging, can get the elements back into place, without boiling the cell. hard hitting, without heating.
so to ME a ultra smart charger, will:
1) work with single cells (lots of them, as seperate units)
2) blast them at first (but only if discharged)
3) never overcharges (but always fully charges)
4) slow down at the end (it could do this with a Vhigh)
5) always pulse charges
6) fully top off SLOWER
7) after full charge does short burst Slow rate pulses, at long pause intervals, to maintain charge without trickle.
8) temp watch (to late)
9) battery pressure watch (to late)
10) Vdrop (to late)
11) can cycle them (discharge) if ever needed.
it is to late to see the pressure rise, because your already bubbling then, after all what is the pressure from.
it is to late to get the temp rise , because the internal temps are already higer than the external, and probes dont make great contact. (burned batteries are brown in thier tight interior)
internal temps on Large cells, can be WAY different than the external temps.
I would bet temp RISE, might totally occur BEFORE pressure and vdrop (boiling), and is still the best bet (like Big Al said). but some temp rise is normal, and batteries that are not so good but usable , will temp rise higher (ok toss them). sounds like the best plan, if you can calibrate it, just like the Vdrop, but before Vdrop occurs.
all of the above "indicators" can represent Damage, so the only flags were using , other than Vhigh are a cell being damaged. and Vhigh can vary also, so we might not be fully charged, or it might never reach it.
another fatal flaw in smart chargers:
Topping off by re-applying to the charger, the smartest chargers in the world, become the stupidest when you just want to top off a bunch of cells.
there they go again, torture testing them. If the power goes out, or you mix the cells up, or put them back on the charger, or move to a different charger , or different human touches them, or you put them in something ,or you dont know how much or if it was used (its still fully charged) , etc etc.
so they must be able to detect a Vhigh loosly at least when first placed on the charger, then work FROM there,
to completly top off the battery.
if its high, just SLOWly top it off, if its low, then charge it normally, till it reaches Vhigh.
that leaves only one thing again, Slowly pulse overcharging it, after some set Vhigh.
WHY
because they arent going to heat up , pressure rise, or vdrop , before they are being damaged.
and each time you put them back on the charger (or power goes back on), the charger is again braindead, and they are cool. so all the charger can do is find the flags again.
did you ever notice, that the protection and charge Specifications for a LI-Ion is about the same thing you would want to do with these?
why does the li-ion get personally singularly babied, and the ni-mhy tortured?
a good Li-ion charger would also, pulse charge them quick without heating, taper off near the end (a specific voltage) , and stop charging before there is any buildups of pressure or heat.
Oh oh i rambled again, and i couldnt afford the ultra charger anyways /ubbthreads/images/graemlins/smile.gif