Author Topic: Cordless drill battery packs  (Read 4400 times)

Re: Cordless drill battery packs
« Reply #25 on: 13 June, 2015, 03:07:23 pm »
Battery 2 now fixed and on charge.

That got easier with the second one, for anyone interested I would not recommend attempting without a Dremel. It would be possible, but it is one of those jobs that is made so much easier, especially if you have to replace the "top" two batteries where you wouldn't be able to get anything else in to slice them off.

Couple of tips: Write all the polarities on each of the batteries. Create a numbering scheme and write the numbers on each of the cells. You will need a heavy duty soldering iron. Tin everything before re-assembly. Try not to short out too much......

Re: Cordless drill battery packs
« Reply #26 on: 02 September, 2019, 07:55:59 am »
Doin' the resurrection shuffle.

The Koo Power battery is still going strong, the repaired Makita ones less so, but that's no surprise.

Anyone know if there is a similar alternative to the Koo Power? They appear to have disappeared from the marketplace.


  • Timelord
Re: Cordless drill battery packs
« Reply #27 on: 02 September, 2019, 02:04:53 pm »
I've got a clone of a Makita BL1830 (so a differently-shaped 18V Li+ battery) as well as one of the genuine article.  Subjectively the only difference is that the clone is a bit sloppy with the physical tolerances, so is a bit stiffer at sliding into the tools/charger.  I haven't attempted to measure the capacity, thoguh.


While the capacity seemed adequate, the inherent shoddiness became apparent when, after an afternoon of enthusiastic hole-sawing a couple of years ago, it refused to charge.

Opening it up revealed a complete absence of cell-balancing circuitry, and a several of cheap-looking cardboard cells that were b0rked beyond hope.  I re-configured the remaining good cells as a battery of half the capacity, charged them individually with the bench supply, and got a little more use out of it before they too succumbed.

I replaced it with an official Makita battery, as the original one from 2014 was still fine.  Internet research has informed me that they balance the cells properly, but suffer from an overly paranoid design feature whereby the battery management circuit intentionally bricks itself after three failed charges.  One common cause of failed charges is if the cells that are tapped to power the battery management are allowed to completely discharge (ie. by a discharged battery being left lying around for months).

The take-home lesson being that if you have an official Makita battery:
a) Make sure it isn't allowed to completely self-discharge
b) If it fails to charge in the official charger, don't just try again, open it up, check the individual cell voltages, and if necessary recharge them directly before letting it anywhere near the official charger again

Alternatively, if you use third-party batteries, some sort of bodgery to balance the cells will make them last longer.
Careful, Kim. Your sarcasm's showing...


  • Mostly Harmless
Re: Cordless drill battery packs
« Reply #28 on: 02 September, 2019, 03:34:06 pm »

If you have a NiMh unit, I would spend the money on upgrading to a Li-Ion based unit. The batteriers last longer, and they are more powerful.

At out Hackerspace we're in the process of junking all out NiMh units and replacing with a couple of much higher quality Li-Ion units.

Beer, bikes, and backpacking

Re: Cordless drill battery packs
« Reply #29 on: 02 September, 2019, 05:33:11 pm »
There's little doubt that my Makita is a little long in the tooth, but it is still up to a job of work, replacing the drill, jigsaw and batteries would be £350, which I would spend if it was needed, but given the occasional use it gets these days it is hard to justify.

Re: Cordless drill battery packs
« Reply #30 on: 02 September, 2019, 06:14:10 pm »
I estimate that I have spent a grand or two on cordless tools that variously blew up and/or had failed batteries, during which time I have had very few failures with mains powered tools (which BTW have had much heavier use).  Thus despite the fact that they are undoubtedly nicer and more convenient to use on some occasions, I have called 'enough' on cordless power tools and I shan't buy any more.

One of my chums who has persisted with them has had to build change balancing circuitry into all his Li-Ion batteries that lacked it (which turned out to be most of them).