Recell NiCad battery with NiMHs?

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DrBunsen's picture
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Would I be able to recell a NiCD battery (Powerbook 180) with NiMH cells? The NiCDs I can get easily only go up to 900mAh, whereas I can get 2100mAh NiMHs for not much more.

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Dr. Webster's picture
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Assuming that the output para

Assuming that the output parameters are the same as the original NiCad battery, the PowerBook should run fine off of what you propose. However, you wouldn't be able to recharge the battery with the PowerBook--NiMH cells charge differently than NiCads, and require special circuitry. Trying to charge a battery with a charger not designed to work with it could be dangerous, as the battery may leak or explode.

If you really wanted to make a higher-capacity PowerBook battery, I'd make an external one that plugs into the power-input port, rather than hack a battery module.

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rael9's picture
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Don't think so

I'm not certain, but I don't think so. My battery charger has seperate settings for NiCad and NiMH, so I assume they need different settings to charge them.

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DrBunsen's picture
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Parallel extra cells?

I was wondering about paralleling another set of (perhaps larger) cells off the ones in the battery - either mount a small socket on the outside edge of the battery, run two wires to the appropriate contacts, or wire straight to the terminals inside the lappy, then plug out to a matched voltage NiCad external pack. Hopefully the 165 batts aren't "Smart" enough to stop me.

(I haven't got the machine in front of me right now and I can't recall if it's a 165 or a 180 - it was definitely NiCad though)

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martakz's picture
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Ive charger NiMh batts in a N

Ive charger NiMh batts in a NiCad only charger before in emergencies...when batteries were really needed. Its ok, but you have to work out the math and time them.

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Jon's picture
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I've seen Dr. Bob and maybe o

I've seen Dr. Bob and maybe others refer to the "ramp-time" of charging cells. I'm not going to implicate them in what I'm telling you, but that is the source for my idea. NiMH and LiON batteries have a fast charge period, then a trickle charge to full power. If you know the ramp specs for the particular cells you are using, the output specs of the charger you are using (assuming a typical one power level NiCad charge unit), you could "work out the math" as martakz said, and only give them the initial stage of the ramp charge.

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dankephoto's picture
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PB 1xx NiMh batteries . . .

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3486528793

I always wondered how these worked, perhaps they have some sort of altered charging circuit built-in to the pack? Seems unlikely though . . . :?

Dan K

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Jon's picture
Jon
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That might be quite likely.

That might be quite likely. The NiCad pack should have a themocouple or something to cut power if the pack starts to overheat. IIRC there is a sensor or something pointed towards the battery mounted on the mobo of the 1xx series. If the pack didn't have a built-in sensor, that could be it. A little creative circuitry and a thermal producing agent and they can tell the PB to send charge power pretty simply. Then they take the power and do what they want with some charging circuitry in the battery pack, and when the battery thinks it's full, signal the PB to shut off charge power so we don't over work the power rectifiers by leaving them in full charge power all the time... Now that I'm thinking about it, someone with a fair knowledge of ciruitry and power system engineering wouldn't have much trouble making a NiMH charger that could "fool" a NiCad system.

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dankephoto's picture
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Interesting point Jon, now I'm curious . . .

to see what's inside those PB 1xx NiMh packs, but I'd rather not drop $37 (incl. shipping) for the privilege. Tongue

Perhaps Doc Bunsen will do the honors, buy and open the sucker to see what's inside.

Laughing out loud

Dan K

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