Knackered Drill Battery Question

I have a drill/driver with two batteries. One battery is losing its charge rapidly so I thought I would have a bash at soldering up a new set of sub-d cells. The current ones (12 @ 1.2volts) are NICD. I have heard that NIMH do not suffer from the same memory problems as NICD so I have two questions. First, is it true about NIMH being less prone to memory problems and secondly will the charger (it is one of these one hour fast charge jobbies) work OK with NIMH? While we are at it, are there any gotchas I need to know about?
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Tinkerer



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NIMH batteries do not suffer from the memory effect. However, the chargers are not compatible. You must use the appropriate charger.
Peter Crosland
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On Sat, 29 Oct 2011 18:56:58 +0100, Peter Crosland wrote:

My Makita chargers will do either (but not Li) and I found out by accident (carelessness) that the battery from an Aldi combi could be recharged in the Mak's charger. The Aldi combi is useful to leave in the shed (I wouldn't leave the Maks there) but thebattery's not good, so I have a dozen LSD NiMH AA cells to lash in and see what happens.
BTW, the Aldi combi is 2.4Ah but doesn't last as long as the 1.3Ah Makita; yesterday the Combis in Aldi had only 1 battery of 1.2Ah!
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On 30/10/2011 08:52, PeterC wrote:

Same here. I switched from 1.3 a/hr Ni/Cd to 3 a/hr Ni/Mh without any problems.
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Dave - The Medway Handyman www.medwayhandyman.co.uk

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Well, that really depends on what the charger is. Some of the chargers were not properly designed for nicads and just did a fast hope for the best charge and often cooked the batteries. Those will also cook the others of course!
Often these cheepo ones were also supplied with those mini vacuums. Absoluter rubbish. I do find that after a while any charger will have issues with series charging as batteries age and their capacities alter you get the backwards charging effect in use of one or more cells. It ; pays not to run it as it starts to slow to try to stop this battery knackering mode. Brian
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Another problem you might have is that the NiMH may struggle to supply the current, if the drill is making use of the higher current capability and lower internal resistance of NiCDs.
Also, I don't know, but I doubt you can charge NiMH as fast as NiCds.
I have an old but very nice electric screwdriver. I have replaced the 3 sub-C NiCds twice now. Tagged ones still seem to be around as replacements.
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Andrew Gabriel
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On 29/10/2011 18:59, Andrew Gabriel wrote:

Certainly isn't a problem with Makita, quite the reverse if anything.

Don't know either. I switched from 1.3 a/hr Ni/Cd to 3 a/hr Ni/Mh. The bigger capacity batteries obviously take longer to charge.
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On Sat, 29 Oct 2011 16:32:18 +0100, "Tinkerer"

In terrestrial use NiCd do not have a memory effect either, it is a bit of a myth. They do suffer from the far more common overcharging they get.

Not really.

Possibly, but there are differences in the way end of charge is detected so using an older NiCd charger with NiMh may lead to overcharging. You are probably better sticking with NiCd which are usually a bit better than NiMh in drill applications anyway.
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On Sat, 29 Oct 2011 22:33:58 +0100, Peter Parry wrote:

They don't like being left fully charged for months on end either, the self discharge naggers 'em as well.

If you can get NiCd cells at a sensible price, they are starting to become a bit scarce. I don't know enough about the charge detection to know if the differences mean that a NiMH battery will get over charged in an automatic fast charger. Suggest that as the OP is now aware that there could be a problem that they try a few charge cycles ona flat battery and see if it gets "too hot" FSVO "too hot". Warm I wouldn't worry about but "oh that's hot" I would, time how long it take to get to that stage and put the charger ona timer so it can only be on for that long or a bit less. Also don't leave the battery in the charger powered or not. Trickle charge doesn't seem to do Ni based batteries any good, niether does the slow discharge through a de powered charger due to component leakage currents.
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Dave.




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Thanks for the responses. I now feel more qualified to make my choice which, in view of what has ben said, will be to play safe and stick with NICD.
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Be careful if sourcing cells from China via Ebay. There are tagged Sub C Ni-Cads doing the rounds which are a total con. They aren't of the capacity described, and can't supply much current - the latter essential for a power tool. Although to be fair they aren't described as being suitable replacements. The trouble is decent replacements might cost more than a new drill with batteries and charger...
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wrote:

Thanks for the tip. I have actually ordered some from Hong Kong but as it is as much for me to play and see if I can do it, and 12 only cost 13 with free postage, I don't stand to lose a fortune if they are not fully up to scratch. Be interesting to see what they are like. The seller certainly had a very high feedback marking on eBay with nearly 20,000 entries.
--
Tinkerer



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I'll take a bet with you now. They will be useless for a drill or any other power tool that needs a lot of current. You'll be able to stall it simply by gripping the chuck with your hand. They *might* be ok for a torch.
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*Never put off until tomorrow what you can avoid altogether *

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wrote:

You're probably right but at least I can see if I can solder it all up. To be honest, the drill driver is only a Challenge from Argos and was dirt cheap although it has been more than adequate for my needs.
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"Dave Plowman (News)" wrote in message wrote:

--

I've just re-celled a DeWalt 18v pack with Chinese sub d cells (15 off) and
it seems so far to be fine. I'm a tad sceptical about their 2900 mAH rating
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