Is this a bad idea? Protech 701 Charger

[joshconsulting]

My WF-139 does the job, but I'm getting tired of using it to charge AW 2600 18650 cells. The 350 mA trickle takes nearly 8 hours to charge a battery. AW says the batteries are fine for a .7C charge, meaning that with a 1.8A charge I could fully charge the batteries in an hour and a half, less then 1/5th the time.

I have a (very) old Protech Supercharge AC/DC 701 designed to charge RC battery packs; it is capable of delivering 1 amp at 12v. I'm a newbie at how charge circuits work; do they output at a specific voltage that can only charge a battery of a specific voltage, or are they voltage-agonistic? I tried a cheap Trustfire 14500 and it had no problem, I only gave it around 100 mA but the charger and protect circuit didn't seem to have a problem with it. As long as I monitored voltage and terminated at 4.20, would I have any problems if I ordered an 18650 battery holder and used it to charge my battery as 1.5-1.7A instead of 350 mA?

 

[Mr Happy]

Yes, you would have problems. Lithium ion cells need to be charged with a CC/CV algorithm. The constant current is only the first part of the charge. When the voltage reaches 4.20 you need to switch to constant voltage for the remaining part of the charge until the charge is complete. This requires a specially designed lithium ion charger.

It is very dangerous to use constant current charging without any automatic voltage control. You may think you can stop the charge when the voltage reaches 4.20 but it might only take a moment's distraction and you could miss it. If the charge continues beyond that point the cells will eventually burst into flames in a very spectacular manner once the voltage reaches a critical threshold.

Please do not ever attempt to charge lithium ion cells using other than a properly designed charger.

 

[joshconsulting]

AWs are supposed to be protected against overcharge somewhere in the 4.3-4.4v range, enough to shorten the lifespan but well before venting would occur - is that considered effective, or is there a risk it wouldn't work? The charger has a 15 minute timer, so I could easily rewind it every 15 minutes until the desired charge was reached, and as long as I checked the voltage of the cell and, say, set it on 2 minutes at 4.17 it would overcharge it by a few minutes at most.

 

[Mr Happy]

OK, yes, I missed that they were protected cells. Even so, it is not a good idea to rely on the cell protection for this purpose. The cell protection is designed as a safety feature, not a method of charge control.

 

[joshconsulting]

I don't plan to rely on it; with a 15 minute timer and checking of the cell voltage before setting the timer, it *shouldn't* happen, ever (then again, so far I've managed to put cells in backwards in both the charger and flashlight 60% of the time. I love protection circuts ).

 

[alfreddajero]

Im not familiar with that charger....did a search online and really cant find any specs for it......is it capable to charge lith cells. If its made for nimh or nicads then i would not attempt it at all. Okay just realized it was more or less a power supply.....

 

[joshconsulting]

Im not familiar with that charger....did a search online and really cant find any specs for it......is it capable to charge lith cells. If its made for nimh or nicads then i would not attempt it at all. Okay just realized it was more or less a power supply.....

Like I said, it's old, I couldn't find much on it online either. It's made for charging 7.2\12v NiCd battery packs, would this make it bad for LiIons?

 

[Mr Happy]

Like I said, it's old, I couldn't find much on it online either. It's made for charging 7.2\12v NiCd battery packs, would this make it bad for LiIons?

Look, you want to blow yourself up, who are we to stop you? :shakehead

 

[alfreddajero]

Mr. Happy already said that it would def not be a good idea even if the cells are protected......You might want to get a dedicated 18650 charger....i have the WF139, and the HXY to charge 18650's only. Another choice would be is to get a hobby charger that has lithium charging settings. I have this charger since my other hobby is RC's but i have not charged any lith cells using this charger.

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXLCJ6&P=ML

 

[joshconsulting]

Look, you want to blow yourself up, who are we to stop you? :shakehead

That's why I'm posting here, was hoping I didn't have to buy a new charger but not at the risk of my life

Can the HXY be relied on to terminate at 4.2V? It can be bought for $7 shipped (1x18650) or $14 shipped (2x18650) and advertises itself as a '2A' charger. Good idea?

 

[alfreddajero]

Well i got mine from shiningbeam and so far it has served me well.....i also use flat top unprotected cells and they come of the charger at 4.15-4.17 and to make sure i use a dmm when they come off the charger to check the voltage of the cells.

 

[joshconsulting]

Guess it's only 1 amp instead of 2, but still - 2 1/2 hours is better then 8, and it frees up my charger for 14500s

I'll probably order the one from ShiningBeam, I couldn't find a US seller with google. Thanks for the tip!

 

[alfreddajero]

http://www.shiningbeam.com/servlet/the-127/HXY-Digial-Li-dsh-Ion-Battery/Detail

Direct link.....it should save you some time, and i like my other charger freed up as well to charge my other lith cells.

 

[joshconsulting]

http://www.shiningbeam.com/servlet/the-127/HXY-Digial-Li-dsh-Ion-Battery/Detail

Direct link.....it should save you some time, and i like my other charger freed up as well to charge my other lith cells.

Already ordered it, thanks a lot! Now no need to worry about terminating charge etc. etc. :twothumbs

 

[alfreddajero]

And please remember that if you run your 18650's til the circuit kicks in basically when the cell has no charge then expect it to take longer for the cell to charge.....i like to rotate my cells and the cells that are kept away are only half charged and never depleted, so it doesnt take long for the cell the charge.

 

[joshconsulting]

Yea, I like to charge my cells as soon as I know I won't need them for a half hour or so - they go straight out of the light into the charger, and I just drop them in the light whenever I need them, so they stay at ~4.2v almost all the time. AW says it'll shorten the life to 3-4 years or so, but I can handle that. Given my track record, they'll probably be lost before then

 

[ubetit]

Already ordered it, thanks a lot! Now no need to worry about terminating charge etc. etc. :twothumbs

Before I gutted my 2 bay charger to use as a cradle for my hobby charger, my charger like that would overcharge to almost 4.3 volts. I'd watch it the first few times.

 

[joshconsulting]

Bleah. Ordered the HXY, tested it as outputting 241 mA into my AWs. Hoping I got a faulty one, emailed Shining Beam about getting a replacement. Glad this happened with a US seller instead of a HK one, I have no doubt I'll be happy with the CS when this is over

 

[Locoboy5150]

Pro Tech, wow there's a name that I haven't heard in a long time. I've been into R/C since 1983 and I remember when Pro Tech was in business. They disappeared without a trace though.

I wouldn't use that charger because, if it's a peak detector charger (I can't remember if the 701 is or not) it was designed for NiCd batteries, the only type of R/C batteries available at that time. Only a few R/C battery chargers from that era are capable of charging anything other than NiCd batteries. My Tekin BC112C is one of the few from back then that can charge NiMh batteries for example, but that's only because it is one of the later production models. The early BC112Cs can only charge NiCd batteries.