I am just wondering if there might be any gotyas...
Long ago I bought a Makita drill kit with 3x 18v 1.3Ah NiCad battery packs and its charger. The charger is marked 7.2 to 18v, NiCad or NiMh. two of the packs now need replacing, but I am thinking to recell them as a cheaper option.
Is there any reason not to directly replace the 15x 1.3aH NiCad cells in the packs, with 15x 6Ah NiMh? Do the battery packs in some way identify themselves to the charger please?
I can't answer the specific Makita question but I believe NiMh cells need slightly more accurate attention to the Delta-V charge / peak monitoring than NiCad so will generally also charge fine (or the other way round in your case, as long as the charger is NiMh ready).
Also (and unlike Lithium) you are generally just looking for that charge profile so a charger can theoretically deal with a range of voltages (cells) without having to know any specific numbers.
It is ideal of course to know how many cells and therefore what the expected battery voltage should be and then you can also manage faulty cells (although this can also be done to some degree by monitoring pack temperature).
I have a generic 18V drill I'd like to re-cell with NiMh (more for the S&G's) so will be interested to see how you get on if you do d-i-y.
Cheers, T i m
Harry Bloomfield a écrit :
A rather confused write up, but this suggests not, that I can just swap NiMH for NiCad. Replacement cells ordered, thanks.
You cannot swap NiMh for NiCd on the same charger, unless the charger is 'NiMh aware'
The charger itself includes both NiCad and NiMh in its spec..
I changed from NiCd to MiMh on my Makita stuff without problems, I'd guess Makita chargers are smart enough.
Its a nice theory, but in the past I have found the cost of buying decent cells has always worked out more than buying new OEM batteries...
(a bit of shopping around got three 2.8Ah NiMh packs for about £150)
The charger will certainly do both. IIRC there are some extra contacts on some of the packs (probably a temperature sensor) - although the charger will also work on packs without them.
Is that 6Ah rating genuine? (i.e. not 6 ebay Ah!)
Unlikely to be a genuine 6Ah, more likely 3Ah, but they were cheap enough to have a go with.
How are you going to fit them? The interconnections are usually welded. And 'tagged' types you can solder usually poor quality - and expensive.
Very neat, but only doing the negative side. Can you do positives "through" the battery without wrecking it, by grounding to the can?
Wouldn't think so, he's looking at a dual spot electrode for the other end
Are this ort of replacement any good? Seem to have good feedback. My 18V Makita battaeries are shagged and, althogh I have a new 18V Bosch combi, having 3 or 4 drills is usefull at times:
Based on my previous experience, I would stump up the extra money for a real one. I did try an ebay 3Ah battery. Performances was ok when new, but the life span was very poor. Put it this way, my original drill came with 3 batteries, one of which started failing after some 8 years. I bought an ebay replacement, and it needed replacing along with the remaining 2 of the original set about a year later.
Even neater. I did have a hunt for anything on YouTube, but didn't spot that. I wonder if copper is the right electrode material, or whether it would be better to use little bits of tungsten (scrap TIG electrodes?)
Does look like quite a handy gadget to have if you are likely to fix many batteries.
I've had several "third party" replacement Makita batteries, two had shorter life than originals (probably 50% though, so still cost effective), others have been more or less comparable. And I have had shortish life out of one original.
According to my lads who have researched this more, some Makita hardware
*including batteries* is being advertised as having a free replacement offer. Sounds unlikely to me especially for batteries, but possibly if their "multiplier" is right it might be worth doing to keep users locked into the brand. One of them is about to try it out (six months of very hard use).
Ah, hence the 1-year guarantee! Thanks, I'll not bother with them.
My experience of replacing Nicad with Nimh has not been good. I find the output currents are lower and the periods between recharges shorter. YMMV. I don't understand why battery makers don't come up with Li battery packs and chargers to replace Nicad packs. The market must be big enough and Li control chips are now only a few pence each.
NiMh tend to have higher auto discharge characteristics - so if left on the shelf for a few weeks they are more likely to be flat than NiCd.
Probably because its more in their interest to sell new tools. ;-)
You may also find that the current demand of the tool is different. I am not sure whether the tool itself has any battery protection built in, or if that is implemented just in the battery. You would need a new charger as well in most cases. By the time you have done that you have spent the lions share of the price of the whole tool.
The charger is very inexpensive. Just look at ipad etc chargers. The tool battery pack has battery low voltage protection chips. These are now very cheap because of the production volume. There are a few Li replacements for some manufacturers, Sears, I believe.
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