Power tool batteries

I'm a noob to batteries, I don't know much about the subject but I just acquired a load of battery tools which were the display in a closed down DIY store, Makita, Dewalt, Bosch and Worx all good stuff, but there are either no chargers, and buying new chargers would cost a fortune. I'd like to rewire the tools with charging sockets on the batteries and just use my imax B6 mini charger.

First project is a Makita 18v li-ion battery, can anyone tell me how to wire the 7 pin balance charging socket on the battery to the imax, and anything else I need to know ?

I've got 8 battery drills now so I can just leave the battery on the tool and recharge it , and use another drill.

Makita uses a proprietary BMS, not sure if that would make much sense. I would disassemble the batteries and check the individual cell voltages to decide what to do with them. If they are overdischarged, which is very likely, they will not charge on the original charger nor an IMAX B6 (or similar) anyway.

You can disassemble the pack to expose the battery then us an ex charger to boost the voltage cell by cell to 3v. With all cells balanced at 3 v you can reassemble and see if charger takes pack back up to 4.2 v

Note all cell must read exactly same to be bqllanced

If original battery charger doesn't charge from 3!up the 4.2 then there are several hacks to hwl

First is to charge each cell up to 4.2 and bypass the bms

Second I'd to run a 7 wires harness and leave connector hanging ouside housing.

You can then use a third party bms

maybe i am wrong but i think he/she means the batteries are okay but he got tools without a charger.
For example he has the drill but not the charger for it so i wants to charge the battery with the imax instead.

and now he is asking how to wire a connector so he can simply use the imax as main charger

You can't know if they are okay, being display batteries they are probably overdischarged and you have to check for that. And if they are then this isn't reversible with the original charger nor with an IMAX B6.

Waterworks said:

I'd like to rewire the tools with charging sockets on the batteries and just use my imax B6 mini charger.

First project is a Makita 18v li-ion battery, can anyone tell me how to wire the 7 pin balance charging socket on the battery to the imax, and anything else I need to know ?

Click to expand...

A 7 pin balance lead is wired (in order) from most negative through to most positive. So at one side you have the -ve rail and the other you have the +ve rail, and all the wires in between are connected in sequence with the interconnects between series cells. hope that helps, youve gotta start getting your hands dirty somehow. : )

As for anything else ... well I would advise you NOT to go ahead with your plan of wiring a balance lead and using an external balance charger (imax or anything else) without first disconnecting the existing (internal) BMS in the pack. in worse case it could damage your charger or something else.

If you didn't follow the rough outline in para one, I would caution you on proceeding with lithium battery construction. I've been lucky so far with my escapes from accidental fires becoming serious -- and I consider myself very capable with all electrics. safety is really important to me ... so I do have a plan in place before any construction, EG doorway clear for rapid exit to concrete pad outside ...

Most top power tool manufacturers today like Milwaukee and Dewalt use proprietary circuits. Practically, the charger, batteries and tools have data pin(s) in addition to the power pins. Trying to charge them with something else in most cases will simply not work. Neither will the tools if the data-good signal is not present. Powering them with correct voltage/current is not sufficient.

Some even got as far as circuit lock-down if you try to change cells.

In such cases, what you can do in most situations, is open the batteries and manually charge the cell pairs.

Can you remove all the electronics that prevent other chargers being used ?

Yes, remove or bypass, but in some cases you will not be able to use the batteries in the tools their are intended for anymore.

But why would you make your life more difficult than it needs to be?

Task: Check and charge power tool batteries

HowTo, step by step:

1. Measure voltage across the main terminals, sort them into two groups: a) Dead batteries, voltage between 0V and 12.5V and b) Good batteries, voltage over 12.5V
Assuming 12.5V as the threshold here, this is just a rough estimate as it will differ from manufacturer to manufacturer what they think is a acceptable.

2a. These are our assumed dead batteries, decide what you want to do with them, i.e. do you want to rescue it or not.
If no, then disassemble the battery to reclaim the cells.
If yes, then disassemble the battery case. See if it uses a BMS, like Makita. If it does then you might have to replace the BMS and they tend to disable the outputs and this can't be undone. Probably not worth it, but you can reclaim the cells. If it doesn't use a BMS, check the voltages of the individual cells. See if you can get access to the individual cells with croc clips or something similar. If not, attach temporary wires.
Then recharge the cells, you will need an adjustable bench power supply for this, especially if the voltage is very low or even 0V. You have to carefully recharge the cells with very low current, like 10mA. If the cell was 0V, see if it holds the charge, i.e. charge it to 1.0V, detach the power supply and see if the voltage drops back to 0V or if it stays above 0V. If it stays then you can continue, if not then you have to decide whether you want to replace the dead cells.
Once back up to voltage, like 2.5V per cell at least, you can charge with any charger through the main terminals. Be aware that this is not a balance charge, make sure you start with the same voltage on all cells and don't charge to 4.2V on the first attempt, go for 4.1V instead and monitor the cell voltages constantly. Being undervoltage cells they might start drifting.

2b. The good ones will charge on the original chargers., the ones you don't have. Consider getting them, usually used ones can be found pretty cheap.
If the batteries don't have BMS they can also be charged through their main terminals with any charger. Same procedure as on the final step of 2a, charge and monitor.

3. The ones you do not want or cannot rescue can be disassembled to reclaim the individual cells. Testing procedure can be found all over the forum but it needs to be adjusted for high drain power tool cells. Check the models of cells you're getting, charging and discharging at 1A will probably not be enough to actually test the cells. You need more current.

Looks like the manufacturers have made the li-ion batteries far too complex for my skills to repair, I will sell the li-ion tools and concentrate on the ni-cad ones which have no BMS in them.

Not a good idea. NiCd is dead tech. Li-ion ones can be cell-replaced if you're careful with the specific protections. Even intent to upgrade one of my batteries with high current 26650 if I manage to fit them in the casing.

NiCd is heavier, less energy dense, and will give you less cycles. But you can use it in extreme cold, it's simple to charge (mostly), and it has gotten dirt cheap. DeWalt still produces a line of tools using NiCd batteries.

I'd agree with you, sell what has no use to you and use what you know how to use.

Li-ion works in extreme cold. It fails in extreme heat.