Charger Suddenly over charging !!!

Batteries, Chargers, and Battery Management Systems.
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David LaFerney   10 mW

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Charger Suddenly over charging !!!

Post by David LaFerney » Jun 26 2017 11:22am

Since last fall I've been using a charger I built using a Drok boost voltage regulator ( https://www.amazon.com/DROK-Numerical-R ... al_qh_dp_t ) to charge my home built 18650 battery packs for 2 bikes that my wife and I ride weekly - and no worries it has always worked great.

Until suddenly the charger started charging the 25.2 volt packs about 2 volts higher than the set point - about 4.43 volts per individual cell - which gave a noticeable performance boost, but of course is hard on the batteries and potentially dangerous.

So obviously I need to replace the charger or find and fix the problem. But I would also like to come up with some kind of over voltage safety cut off circuit to add some backup safety in case of future malfunctions. Hopefully, there is an off the shelf solution. Any ideas?

Also - what is a reliable charger for custom voltages like this?

Someone is probably going to ask about my BMS - I'm not using any. I have the packs internally separated into 6s4p modules with power and balance leads from each module - when charging I parallel everything and use a battery medic to parallel balance while charging and then use a wiring harness to connect the modules in series for use. So no balance on discharge - which isn't really an issue so far. And I use a fuse for overcurrent protection on the bikes.

Since everything starts out balanced to within 2-3 1/100s the battery medic keeps up pretty good during the main charge, and when the charging current starts coming down at the end of the process the BM has no problem correcting any remaining imbalance issues - so it all ends up perfectly balanced and fully charged. Until something broke that is.

Jon NCal   1 kW

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Re: Charger Suddenly over charging !!!

Post by Jon NCal » Jun 26 2017 2:20pm

icharger is a good balance charger. I use the 106B+ icharger.
Last edited by Jon NCal on Jun 26 2017 4:42pm, edited 1 time in total.

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fechter   100 GW

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Re: Charger Suddenly over charging !!!

Post by fechter » Jun 26 2017 2:25pm

The charger is adjustable, isn't it? Without a BMS there aren't many easy ways to make a safety circuit. I have seen some Chinese volt/amp/ahr meters with a relay that can cut off the charger when a programmed limit is reached. Handy to have the meter function on a charger too.

Over charging batteries is very dangerous and probably the most likely cause of battery fires.
Charge those things in a safe place like a fireplace.
"One test is worth a thousand opinions"

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cal3thousand   1.21 GW

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Re: Charger Suddenly over charging !!!

Post by cal3thousand » Jun 26 2017 2:34pm

Since you have balance taps at the 6S level, get some Cell Log 8 devices. They will alarm you if any P cell group goes too high (and/or low) of voltage and are adjustable. Cheap insurance for sure.

Also, there are definitely safer and more reliable adjustable chargers out there. I use potted Mean Well LED drivers and would be much more confident in one of those versus this exposed circuit board that has been thrown together (for the record, I have one of these things you use, but only have it for spare/emergency, not main charger)

And then, at the top prize level for consumers is the Satiator by Grin
Get a Cycle Analyst and a Multimeter, you're still a noob if you don't have at least one of each.

Planning on posting questions or buying anything on this site? Put up your country (at minimum) on your profile. This is a worldwide forum and we haven't reached clairvoyance.

John in CR   100 GW

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Re: Charger Suddenly over charging !!!

Post by John in CR » Jun 26 2017 11:35pm

Throw it in the trash before you start a house fire. Seriously. A charger that overcharges once can never be trusted again, so don't put you and your loved one(s) (and neighbors if you live in a multi-family dwelling) lives at risk over something so cheap.

If you feel you have to use it until you get another delivered, then protect yourself with a cut-off timer, which is always something prudent to use anyway, even with trusted chargers.

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dogman dan   100 GW

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Re: Charger Suddenly over charging !!!

Post by dogman dan » Jun 27 2017 5:27am

Amen John. The pack and the charger belong outside now. Don't make your house look like mine.

miuan   10 kW

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Re: Charger Suddenly over charging !!!

Post by miuan » Jun 27 2017 6:02am


David LaFerney   10 mW

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Joined: Aug 16 2016 7:31pm
Location: Cookeville, TN - Southeastern United States

Re: Charger Suddenly over charging !!!

Post by David LaFerney » Jun 27 2017 10:12am

Miuan - Thanks! That is exactly what I was hoping to find. I just ordered one off of ebay - less than $9 - just search for xh-m602 https://www.ebay.com/sch/i.html?_from=R ... 2&_sacat=0

Every one else - Thanks for the responses. I agree with all the warnings, and I've always tried to be safe. I'm thinking that no matter what kind of charger you use there should be some kind of redundant safety measure in the loop because any device can (and will eventually) fail - 2 safety measures failing at the same time are much less likely though. For 9 bucks you could run through 2 of the xh-m602 circuits for tripple redundancy. I probably won't - at least not until I check it out first.

I'm still shopping for a new charger though and would appreciate suggestions - I think I'm going to start a new thread for just that.

To the mod that moved the post - sorry, I'll try to better in the future.

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