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home made battery pack?

k1c's picture

The old, cheap portable dvd player will not charge any more.  The label says 7.4v 3500 mAh on the battery cover.  Corded power is 12v dc. 

It looks like I can't use my 1.2v rechargeables in serial or parellel, since I get either more volts or more amps per hour, but not both.

Another way would be to buy battery cells with more mAh (original 3500 mAh barely covered one movie).  For example, can I buy 6 1.2v cells, connect them in serial, and use the power connector from the oem battery, and assume the player will work?

Also, will the new batteries charge through the player?

Again, thank you in advance.

I bet 6 1.2s will work OK (post #207058, reply #1 of 5)

I bet 6 1.2s will work OK

Greg

In terms of mAh, and from the (post #207058, reply #2 of 5)

In terms of mAh, and from the standpoint of device operation, it never hurts to have cells with a larger rating (other than they may be physically too large to fit).

Rechargeable cells come in 4 flavors -- lead-acid, Ni-Cad, NiMH, and Li-ion.  These have nominal voltages, respectively, of 2.0, 1.2, 1.2, and 3.6V.  Note, however, that when combined into a "battery" the battery's rated voltage may not be an exact multiple of 1.2 or whatever, since that figure is approximate to begin with.

If you replace the cells of a battery with new cells of the same type (eg, NiMH for NiMH) then you'd replace the cells 1-for-1.  And, if the cells are of the same type (and not Li-ion), the existing charger should work so long as the new cells do not have a substantially different mAh rating (not differing by more than roughly 2x).

If you replace Ni-Cad with NiMH, the charger will probably work but may not produce the best battery life.

Li-ion batteries are a different breed -- they need a special charge-discharge controller integrated with the batteries.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

BTW, outfits like Batteries (post #207058, reply #3 of 5)

BTW, outfits like Batteries Plus will rebuild the battery packs for you.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Thank you both.  The battery (post #207058, reply #4 of 5)

Thank you both.  The battery is lithium and couple of flat cells, but I don't see any controller on it, unless it looks like a piece of thin cardboard.  There is definitely no circuit board on the battery pack itself.

I'll make one with NiMh batteries I have and see if it works (1.2v 2000 mAh AA), then maybe go to buying the new cells and charger.

It the cells are lithium and (post #207058, reply #5 of 5)

It the cells are lithium and there are a "couple" of cells flat, that would be both of the two cells in the pack, right?  2 x 3.6 would be 7.2V, near your 7.4V.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville