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Old 01-03-2020, 07:31   #1
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Charging n 16.8 v Li-ion drill battery

So my relatively cheap Li-ion charger for my 16.8 v cordless drill died. A new charger is almost as much as the drill. (It's an OK drill.) I'm trying to avoid an expensive solution and wondering if I can use an old computer charger to charge the batteries. The computer charger is outputting about 19 volts.
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Old 01-03-2020, 08:36   #2
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Re: Charging n 16.8 v Li-ion drill battery

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Originally Posted by Epicurean View Post
So my relatively cheap Li-ion charger for my 16.8 v cordless drill died. A new charger is almost as much as the drill. (It's an OK drill.) I'm trying to avoid an expensive solution and wondering if I can use an old computer charger to charge the batteries. The computer charger is outputting about 19 volts.
No.

Your old charger would have built in intelligence to end the charge when your Li-Ion battery was fully charged thereby preventing overcharge, thermal runaway, and a spectacular fire!

If you had a CC/CV power supply that you could set to about 16.5v then you might get away with it if you monitored closely and disconnected the charger when the 16.5v is reached. It would probably be ok if gif you left it for a few hours under those conditions but Li-ion don't like to be left on float for too long.
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Old 01-03-2020, 09:51   #3
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Re: Charging n 16.8 v Li-ion drill battery

Thanks. I suspected something like that although I thought the intelligence was in the computer. Do we commonly have those CC/C V power supplies? I don't have to fully charge it, which is probably better for it anyway. Can I put it in parallel with 5 or 6 18650's (in series) to give it a partial charge? I haven't found any cheap chargers on the usual Chinese internet websites.
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Old 01-03-2020, 10:19   #4
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Re: Charging n 16.8 v Li-ion drill battery

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Originally Posted by Epicurean View Post
Thanks. I suspected something like that although I thought the intelligence was in the computer. Do we commonly have those CC/C V power supplies? I don't have to fully charge it, which is probably better for it anyway. Can I put it in parallel with 5 or 6 18650's (in series) to give it a partial charge? I haven't found any cheap chargers on the usual Chinese internet websites.
In a computer the intelligence is normally in the battery and the charger is dumb, in a hand tool the intelligence is often in the charger and the battery is dumb - that is why it would be dodgy to use a computer charger for your power tool (both are dumb!)

Reasonable cheap CC/CV chargers are available but you will need to know what you are looking for - they would normally require a DC input and the be of the boost (less common) or buck (common) variety.

You would require a boost charger in order to raise a 12v source to 16.5v or a buck charger to drop 24v source to 16.5v.

If you have 24v available then look for a DSP3005 (30v 5a) in the normal places (Amazon, Aliexpress, Bangood, Wish etc).

Or just cough up for the correct charger
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Old 02-03-2020, 09:23   #5
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Re: Charging n 16.8 v Li-ion drill battery

Epicurean,

If you're not already convinced, watch this video. Especially at the 4 min mark.
<
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Old 02-03-2020, 13:13   #6
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Re: Charging n 16.8 v Li-ion drill battery

I employ a 150 watt voltage booster regularly for various things, and have charged a 24v Nicad battery with it several times successfully, but then I also destroyed it by not discharging the battery much, then charging it, forgetting and overcharging.

That 'gotta get it and keep it full' lead acid mentality came back to bite me.

Current had increased well over 150 watts and the cells were popping an crackling ominously, and continued to do so for a long time after I ripped the wires off.

I have a wattmeter inline to read Volts amps watts amp hours watt hours, but I should have had a temp sensor with an audible Alarm on the battery.


Obviously Nicads have different requirements and less consequence if overcharged compared to lithium. I did have it on some brick pavers away from anything flammable at least, but I wish I also had a full face shield when I heard it crackling and snapping and needed to disconnect the boost converter.

I think If I were to try charging a lithium power tool battery I'd make sure it was dead and put in ~65% of the rated capacity and then stop, at least initially.



These can be had for under 2$ slow boat from China.
I put mine in a old inline powerbrick with a 60mm fan bridging the two heatsinks, and 45 amp anderson powerpoles on input and output, and use it as a Lead acid Battery to lead acid battery charger regularly. If I ever employ it on another chemistry again I will be doing so under much more rigorous observation than my most recent Nicad attempt.

The now batteryless powertool, I use an 18 and 22AH AGM (same size, different weight and age) battery in series, on 8' of 10 awg. Less convenient, but way more power when heavily loaded than the Nicad ever had.

My voltage booster regularly takes float voltage back upto 14.8v for charging these two 12v AGMS separately from my main battery bank.

I tried charging them in series. One battery read 13.5v the other 15.5. Wont be charging them in series again.

There are lots of voltage converters that look like this one, some are buckers, some are boosters, and some are buck/boost. I have a buck boost with 2 potentiometers, the second being a current limiting potentiometer which would be a better choice for Dc to DC battery charging than one with voltage only potentiometers, but I was unaware of this option when I installed the sub 3$ single trimpot booster in the ventilated powerbrick casing several years back.

I replace the tiny trimpots with 22awg or thinner wires to a larger remote fingertwist potentiometer on all of these, so I do not have to bust out the reading glasses and the jewelers screwdriver each time I need/want to adjust charge voltage / fan speed/ led brightness.

The potentiometers are usually 10K ohm, but on the 10 amp buck/boost converters I like best, they are 200K ohm, and I never found any 10 turn pots of that value. A few, on some 5 amp buckers, have been 50K ohm.
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Old 08-03-2020, 03:45   #7
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Re: Charging n 16.8 v Li-ion drill battery

Ikanode I am a believer! Isn't that why they ban the Galaxy's from airplanes?

Sternwake: I could do that. When everything else on the boat is done I'll have more time to monkey around. I have the parts. But it just seems like this must be a common occurrence. Anyway, not finding the exact same battery charger mine had I ordered another Li-ion charger and will just splice it in. It was cheap enough.
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