Converting old cordless tools to new lithium batteries.

Kinda. I have Makita batteries and adapters to Ryobi and Worx, which also covers a random Spear and Jackson hedge trimmer I found cheap on ebay (didn't initially fit the Worx adapter, until I cut away a small plastic tab and now it does).

However, first of all you're going to need to find an adapter to your B&Q shape of battery. You may find that difficult. You could 3D print your own, but another option is to buy a 'base' that fits on a modern battery and then glue it to the plastics of one of your old batteries, eg:

Every tool battery has BMS circuitry, but the question is whether they contain chunky MOSFETs to shut off the power, or whether they ask the tool to do it for them. I believe the Makita modern 'star' LXT do contain MOSFETs - you can look at teardown videos of a type of batteries to confirm whether the MOSFETs are there or not.

However most batteries have state of charge indicators on them, and a general rule of thumb is to never let them go below 50% (ie 2 bars out of 4) when using adapters. By doing this, even if you don't have in-battery MOSFETs you shouldn't have a problem.

Don't discount Aldi (Ferrex, Workzone) and Lidl (Parkside) as they are often sources of cheap batteries and chargers. You may not be able to buy a standalone base plate for those batteries but you may be able to find an adapter to <something else> and then hack that. Although I did find a Ferrex base:

Theo

I think Big Clive said because ryobi lithium ion batteries were compatible with older ryobi nicad/nimh tools they contained hardware to prevent over discharge. The problem is they are the shape with a tongue rather than a brick lite Makita ones.

I think batteries for Aldi ferrex 40V tools are unobtainable, as are the chargers, although anyone good with a soldering iron should be able to rebuild a pack with tagged 18650 cells.

I have an old Wickes drill which I could locate a battery for.

I had bought a Parkside drill and had the idea of adapting the Wickes one to take the batteries as I had more than one.

I found an ‘adaptor’ on EBay which is, essentially, the mounting for the battery, with connectors, to two flying leads.

I simply bolted it to the body of the Wickes drill and wired the leads to the connector. It works a treat. I use the Parkside charger.

I’ve seen adaptor which do much the same for more popular brands but simply slide or clip into place.

Slight thread-drift here...

I have an old Qualcast hedgetrimmer-on-a-pole which would still work brilliantly well if only the ni-cad batteries inside the pack hadn't rotted completely away. I think the charge management is in the charging base, isn't it(?), because it looks like there's an array of bog-standard ni-cads inside. Is there any reason - safety would be a good one - why I can't just buy a spot-welding tool and a cluster of shop-bought ni-cads and make up my own array to stuff back into the casing?

Thanks,

Nick

NiCd stuff often had a fairly dumb slow charger - I had a drill where there was a transformer, bridge rectifier, two resistors and an LED. It relied on the transformer + resistor limiting the charge current. There were just two wires to the battery - not even a thermistor in the pack.

Not sure if you can still buy nicads nowadays, but if you can then doing a swap as you suggest would be doable. If there are any other components like thermistors or thermal fuses then transfer them over from old to new.

(Check Aliexpress for spot welding tools, they are about $25 including delivery)

Depending on the voltage, I would probably look at replacing with lithium-ion using some of the suggestions in this thread though - either using a third party tool battery or making your own lithium pack + BMS + external charger. You may well find the tool performs a lot better with lithium, as the internal resistance under load is a lot lower.

Theo

If they look like bog standard Ni-Cads then they probably are.

Chargers for Ni-Cads seem to work OK with NiMH batteries but not Lithium Ion ones which have different charge characteristics. So bog standard NiMH equivalents to your Ni-Cads should just work. If the set needs a spot welds, then buy tagged replacements and then you only need a soldering iron.

The reason I would be wary of using lithium-ion is because the individual cells each have their own battery management circuit, don't they? I'd be wiring them into an array to be stuffed inside the pre-existing battery casing that the expired cells would have been removed from and I'd be worried that spot-welding them together might bugger up the internal electronics. At least with ni-cad (or I suppose NiMH as well?) the controller is simpler and the error factor is less lethal if it does go wrong.

Nick

No, there isn't!

Hot-melt glue to join the batteries, maybe attach a thermal sensor to the pack.

Or get tagged cells, or find a company that re-cells packs. The last may be a good deal, as they'd buy cells in bulk and might get better quality ones at a good price.

Thomas Prufer

No. The BMS needs to be able to connect to each cell, so for an N cell pack that means N+1 wires but you only need one BMS board. The BMS will typically disconnect the pack from the outside if it detects a problem like overtemperature, and will use the N+1 wires to balance the cells internally. Outside the battery you don't see this - there are just two wires for positive and negative. Given the vastly higher energy density of lithium ion over NiCd you may find there's space in the pack for a BMS board.

For charging typically you are applying a constant-voltage/constant-current (CV/CC) supply with the CV set to the maximum cell voltage you want to charge them to - eg if it's regular lithium ion that's 4.2V per cell so the CV charger for your N cell pack is set to 4.2*N volts. Then there is a current limit (let's say 1A). Let's say it's a 10 cell pack so the voltage limit is at 42V, then if the pack isn't fully charged (let's say it's at

Fast charging is another thing and I suggest not doing that with a DIY pack.

NiMH has a higher internal resistance which makes it less good for a tool retrofit, as it's less able to deliver the power than NiCd.

Fair enough if you want to avoid DIYing the BMS/charger, but then look at going for a pre-made pack and adapting it to your tools - if the tool accepts a given voltage then it doesn't care how you made it.

Although it's worth being mindful of high state of charge voltages, eg a nominal 1.2V NiCd is about 1.4V when full, while a 3.6V nominal lithium ion it's 4.2V. An '18V' NiCd pack (15 cells in series) goes up to 15*1.4 =

Theo

AA and AAA nicads are widely available. It's even possible to get higher powered nicads which might be more suitable for power tools, eg:

No. Chargers for NiCds are specialised but will work on any NiCD. Be careful about substituting NiMh for NiCd though. They are sufficiently different to potentially get over charged by a NiCd charger.

Not always, if they are smart/fast ones.

Smart charging attempts to drive a constant current through the cells until the voltage starts to *drop*.

Once this happens the cells are charged. With NiCd the 'delta peak' is quite large. With NiMh it is a lot smaller.

Obviously trickle charging works with both equally well.

Li-ion is far more like a car battery. Just keep charging at a constant current, no more than the cell capacity in Ah till you get to 4.2v per cell, then STOP

I.e. on s 4.2Ah pack you charge at 4.2A maximum

Or else <FX smoke and flames>

Not always.

I've been running multicelled batteries in RC aircraft for years. IT works if the batteries are well matched to start with and are not abused.

They do come with access leads to individual cells which you can buy chargers for but I never have

Yup

Almost all power tools use sub-C sized cells. They are widely available tagged for making packs out of without a spot welder

Best deals from Ali Express with usual caveats

Google 'tagged NiCd sub-C'

Those are emergency lighting batteries, which are rated up to 1C (4A for the D size, 2A for the sub-C size):

Looks like the Panasonic N-1700SCR:

Not as good as lithium, but better.

You would also be paying £72 to recell an 18V pack.

You can no doubt find shady cells around Aliexpress for much less, but I expect performance or longevity to be poor.

Theo

Correction, C=1.7Ah not 1Ah so: Max current at 8C = 13.6A Voltage drop in cells = 13.6*0.06 = 0.816V Voltage available for tool = 18-0.816 = 17.18V Power available for tool = 17.18*13.6 = 233W

Better than the other type, but still not as good as lithium.

Theo

When I shifted platform from my original Makita 18V NiMh drill and ID to LXT, I also bought a couple of adaptors to let me run the old tools from the LXT batteries. The BMS ought to take care of the battery (LXT batts have quite decent management systems).

You can't use the old charger for the LiIon batts though - so the adaptor should only be used to make the new batt fit the old tool, not the old charger fit the new batt!

No reason at all, not to, but to make it worth the effort - make sure you buy quality NiCads. I recelled a Makita drill battery some years ago, it's still good, better than when new.