Thread: Cordless tool batteries

Do lower voltage batteries last longer.

or are NiCad batteries longer lasting than Metal? The other common denominator was that the older batteries (on record, above) were Nicads.

Derek

Re. Cooling NiCad packs. I only used to only cool mine if I wanted to use them again on the same day, and I used a six-pack esky and a small ice pack. After a race they were sometimes too hot to touch, and you are meant to not charge them until they are cool.

I was told by the guy that sold me the Metabo that he wouldn't recommend any power tool with the NiMH packs. I think I read somewhere that the high rate of discharge incurred by running a big power tool wasn't good for them in the long run. This may have something to do with the internal heat dissipation and its effect on the electrolyte or anode/cathode. It may also change in time as technology improves, as it certainly did with NiCads.

I only use them for small appliances like my kids' Gameboys and my CD MP-3 Player, Video Camera and Digital Camera. The benefit of not having to flatten them every time you want to charge them outweighs the slightly higher purchase cost.

NiMH RC racing packs came in just after I left the hobby. This co-incided with when we sold our last house and moved up where we are now. Also my wife used to complain about every second Sunday at the Track, and money spent on small trivial (to her mind) electronic items. It was easier not to start up the hobby again given I live in a renovation in progress, however I have an off-road buggy to use in the back yard about 90% built, so maybe there's hope...and it's of a sufficiently high standard to be raced one day

Mick

I have a 7.2 V Black&Decker drill it lasted 16years heavy use for the first 3 or so. Them I bought some batteries from Dick Smiths and soldered them in, not easy to do this repacked battery was much longer lasting than the original, even if I could have found one. The cells are not expensive can’t remember how much as I put them in 2 or 3 years ago.
Glenn

...if any budding electronics hobbyist would like the circuit diagram for the discharger I mentioned earlier, let me know. It's easily modified for use with different voltage packs...

Mick

Mick,

Yeah, I'd be interested in having a crack at the discharger.

Hi all,

This is the Discharger I referred to. Please note it's powered by the battery pack, so if you have a high-voltage pack, then adjust the Zener value and the relay coil voltage to suit...and make sure the capacitors are rated accordingly.

The values will work for a 7.2v (6 cell) pack. I used a ten-pack of 12v tail-light bulbs in parallel as the load. Just make sure when they're glowing (and they do very brightly even with a 7.2v pack) that they aren't touching anything (I used to dangle them off the table in mid-air).

Just sand back the nickel-plating near the bayonet fitting, and solder them together with a high-powered electric iron. Then solder all the lead contact ends together.

Mick