Question about NiMH AA battery discharge in serial

stockae92

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if multiple NiMH AA batteries are in a known charge state (i.e. all individually charged to full status), if i discharge them in serial (like in a mmag), will they discharge at the same rate?

(meaning can i make a battery pack out of 2 NiMH AA batteries, change them and discharge them with no problem?)
 

VidPro

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yes.
A bunch of points, from reading and experience:

I think the talk of one cell in series discharging faster is a heat issue. not sure, but in a flashlight one is always getting hotter.
In eventuality some of the cells will be better or worse, no matter what you do.

hard impact on any rechargable can effect it, so mabey some of it has to do with a cell being damaged, from dropping the light or the cell.

some tabbed cells can Jam into the Base of the next cell, i have a set of Ni-Mhy D cells that they put a paper ring around the top (around the tab) so it would decrease the impact of the tab going into the base of the cell above it, if the light was dropped.

pack makers prefer to match the sets of cells they put in a pack, even if its matching the low ones, you would have a better pack with less imbalances

Overdischarging a pack, can result in one battery being reverse charged, but only when any one of the cells is completly dead (0v) and the operation is continued.

at the end of a ni-mhy battery packs chargeing, a good circuit will input a low current (preferably pulsed) that will "overcharge" but at acceptable rates, the batteries that are fully charged. this will bring the ones that are not fully charged up to thier top charge. (balancing through carefull overcharging).

and finally
Ni-Mhy or Ni-Cd packs would be much BETTER if they could be dissasembled , SO you can individually cycle them (even very low) and individually charge them.
if you made a pack that charges with a jack, if you could dissasemble it say once a year, and cycle individually, and even low cycle them (which can ONLY be done individually) you would make a longer life pack.
also then you can switch positions, so the heated one is different.
 

VidPro

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also your more likely to have an imbalance when in parellel, in series they SHOULD have the same current flow going through each cell.
in parellel even a Short wire between the parellel sets, can cause the "first" cell (or set) to discharge faster.
especially in a high-discharge rate.
to fix that, either mondo connections in good quality copper, or "center tapping" the parellel set. which electrically would insure the exact same power drop via the connections.
 
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