charging several batteries at the same time

[Jimski]

Hey all,
I want to charge 2X 1700 mAh Nicad batteries on the same charger, at the same time.
the charger is a TLP with all options.

should I plug them parralel or serial ?

I was gonna go parallel since I have two male plugs than I can both stick in the charger's output.

plz tell me if it's wrong.

thanks for your help!

[Mantelope]

This is a terrible idea, you'll probably mess up your batteries. Besides, it would be no faster than charging one and then the other, since the charger's going to be outputting the same power anyway.

[Jimski]

wouldn't I get a better charge with a longer charge on both batteries at the same time , than with a short charge on each one sequentially ?

I just have 1h to charge both of them...

I know I won't mess them up if done properly -
I'm just worried about the change from 8 cells to 16 cells, for the charger.

[Naglfar]

Batteries don't get 'more charge' if you charge them slower.
If it normally takes 1 hour to charge 8, it will take 2 hours to charge 16.

There is no advantage whatsoever from an electronics perspective in doing this, it will just put extra stress on the charger because you're drawing more current than normal, though it shouldn't hurt anything.

[Jimski]

ok thx I'll just go sequentially then.

...
someone told me the chemical process was done better with a slower charge.
sounds logical, is that relevant?

thanks!

[Kos-Mos]

actually it is more about the way the charger detects the peak...

Think about a funnel.

If you drop a whole bucket of sand in it, it will take a few seconds before the sand actually go through. The funnel will "look" full.

While if you drop the sand a little slower, the funnel will have time to empty at about the same rate you fill it.

Same with the batteries. If you charge, say your 1700mAh pack at 3A, then the charger will detect the pack to be full, when it is not.

At 1.5-2A, the battery has time to assimilate the energy you push in it, so when the delta-V will occur, the pack will really be full.

Don't even THINK about charging 2 batteries with a charger not made to do it (ie: independent outputs) In parallel, the charger will probably blow from over current, and the pack would take about 2.5 times the normal charge time. In serial, 100% garanty to melt the charger.

[Jimski]

lol
thanks, sir.

[Azathoth]

Also, I don't believe your charger is rated to charge more than a 7-8 cell pack.

[Styrak]

Also, how would a smart charger tell when the battery(s) were charged? If one pack is charged? If both packs are charged?

Bad idea.