Generic Lithium battery pack charger

Electronics
#1

Does such a thing exist? I have a small battery mower I use for a small area - Sunjoe 28V mower.
It has ceased to charge. I have spent way more time than it’s worth trouble shooting this $100 mower. It has an internal Li battery pack that has 14 cells. The pack looks clean and intact. The cells all read exactly 3V. So I suspect they are good and the charging system has quit working. I can’t even figure out the charging system. It has what appears to be a way undersized wall wart charger that is 6V DC and plugs into the mower. The power adapter input is fed to what I expected to be some sort of regulator board. But the board has no electronics. The 6V is fed into a bundle of 3 wires. Two are high amperage that feed back to another bundle that goes to the motor regulator.

I saw the diminutive power adapter and the lack of any regulation outside of the battery pack and I guessed that it was simply a ‘trickle’ charger. A horrible way to charge Li batteries but I never cease to be amazed at pitiful engineering in throw away consumer products these days.

Then I noticed that the adapter was 6V. So I guess there must be some sort of internal boost converter to charge this pack? Or perhaps there is an internal smart charger that charges and equalizes individual cells? Maybe I’m not giving the company enough credit for their technology. That is, it looks like 6V DC is fed to the 28V battery pack. But I did not disassemble the pack to see how it’s configured. Just opened the case to count the cells.

Well, not sure why it’s not charging but I thought perhaps there is a generic Li charging gadget for folks like us that can charge any pack. I realize that simply charging all cells in series is not the best way to do it. Some cells become under or overcharged as cell differences develop. But I’m trying to salvage this thing if I can.

What do you think?

#2

I’ve found sucess in the RC market finding what you are looking for. I don’t have any packs that are all the way up to 14 in series, but for my packs it works great.

You can find it on ebay and amazon for cheaper than direct, but be careful not to get a clone.

#3

That charger can do a lot, but it does so very slowly from my experience in the mid size RC packs. That said, for safety, piece of mind and cost, you should just get a newer mower. The Ego line is a really good option and has removable packs when cells inevitably go bad.

Having now thrown 3 LiPo packs out of my house as they caught fire. I only count myself as lucky I haven’t had the house burn down. Even knowledgeable people light these batteries up given enough time. But, us DIYers are starting to look like motorcycle organ donors when it comes to LiPos. It isn’t if your going to have a fire, its when.

Careful, and I wish you the best of luck on your project.

#4

Check the fuse?


(yea, not the same pack as yours, but with the way these companies operate, I can’t imagine yours is THAT much different once you’re inside…)
#5

That goes up to 6S. It sounds like a 7S battery if the voltage is 28V (7S2P).

#6

This guy did a FAQ about charging Lithium Ion batteries.

His question was “Should you be at home when you charge a Lithium Ion battery?”

His answer was “Absolutely, the flames are beautiful to watch.”

One of my favorite random quotes about charging Lithium Ion batteries.

Better safe than sorry, unless you are looking to do endless paperwork about setting your home on fire.

The cautionary comment would be pretend your Lithium Ion battery ARE going to catch on fire. What is around them? What are they sitting on? What is above them? How do you get them outside? Do you have the right kind of chemical fire extinguisher?

There are some really smart 18650 battery chargers that will tell you everything that is going on while the battery is charging. For a random sized battery pack, much harder to get useful intelligence.

#7

Mal - This pack has 18650s in it. Are those applicable to a LiPo charger? 6 vs 7 cells, noted, thanks, luke!
Diplo and Nick - Yeah re fire risk - it will be on the floor of my garage!
jast - great vid re the battery pack. I will reopen my pack (it’s internal to the mower, not a removable unit typically. I suspect I’ll find a board like that. It does give 21 V on the output, consistent with undercharged Li ion x 7 cells so I suspect it’s not the fuse. But certainly could be the (presumed) hidden controller board.

Thanks, again, will update.
DJ

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#8

Modern chargers for RC hobbies support many battery chemistry types including lithium ion like the 18650. Before charging be sure to select the proper battery chemistry type (or expect fire).

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#9

THIS… When I charge batteries they are on the granite countertops in the kitchen or some other place like that where there isn’t something directly overhead like the bottom of a cabinet and where they aren’t on a flammable surface. While I haven’t had a Lithium battery go up yet I did have a NiMH battery charger melt itself down. That was a sight!

#10

My most exciting moment with Lithion Ion batteries was when I worked for a bank. I had a “build your own” cell phone charger brick. I could put up to 4 Lithium Ion batteries in this thing. What I was not paying attention to was the source of the batteries. The batteries I used had an unknown origin and I did not have a good way of testing them.

It was a long walk from the parking lot to my desk. Stadium size building. About 5 minutes. Within the building it was 3 minutes to get to the entrance/exit.

I was at my desk and needed something from my carry bag. Usually it was room temperature in the bag. I got whatever I needed and noticed the bag was warm. That was odd…

I went back into the bag and found my new battery pack was HOT. And while going outside would have been smart, I was 3 minutes from the door.

I took the battery pack apart and separated the HOT batteries. Then I waited… I did not know if any of the batteries were now self contained igniters. It was an interesting and looong 10 minutes. Then the batteries started cooling off.

The conversation that did not happen was “Hey Boss, the funniest thing happened when I set the building on fire.” I had that conversation in my head about 20 times. I cannot image that conversation would have gone well.

#11

I get a kick out of the fake Chinese Li battery brand called Ultrafire :stuck_out_tongue:

And they are rated at 5000 mAH. :lying_face:

#12

100% agree with you

#13

Their 'zon / 'bay marketing innovations have long surpassed 5Ah in 18650 - suspect they’re past the 10Ah mark now, unlike those rubes at Panasonic, Sony, LG, Samsung that have been stuck at ≤3.6Ah for years now.

/s

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