What's up with my battery?

[swbluto]

First, I was doing 15 amp tests on my Ping battery using my new testing method. It cuts out after about 4 seconds.



I then took off the "duct tape"/saran-wrap and measured the faulty cell group's voltage correctly(It was 3.20 volts - not bad, but still .06 volts below the group average). I then did the discharge test except this time the battery didn't cut out. Instead, the voltage on the faulty cell group kept dropping and dropping, even past 1 volt! Woah, this thing is supposed to have LVC!(And that's probably what was cutting it out before) After a while, I noticed a burning smell and I eventually discovered the mosfets were burning as I could see a trail of smoke rising from them! What??? It was doing this with a constant current of 13.5 amps which seems like a normal amount of current(I usually run upto 20 amps or so). I ran the thermometer I have and it reported "Hi", which is basically anything above 225 degrees Fahrenheit.

I think it's possible I might have discharged some static electricity but the board couln't be that sensitive, could it? Also, the volt-meter's probe was accidentally touching one of the "voltage detector's" legs and the probe was attached to a cell in the middle of the battery but that couldn't do any harm, could it?

Anyways, help!

 

[liveforphysics]

You are in luck. The battery is still as good as new. You can still use is as a boat anchor with no decrease in boat anchoring performance.


I don't know the specs of your pack, but let's say it's 20Ah made from 4P 5Ah cells. I would think you would observe the effects you are seeing if somehow the tabs were to have been cracks or torn somehow on the other 3 buddy cells that should be helping that weak cell. Check for that, as I think it would be unlikely that all of the cells in P would be bad.

 

[swbluto]

Pack: 48V10Ah Ping 1.0

Eh, I was needing to repair/replace the group of cells that went extremely low in voltage so I just did it. And, make no mistake, repairing a ping battery is a serious PITA. I ended up ripping off a cell's tab while I was trying to yank the faulty cells out(It's so hard to remove the cell tabs at times), so I ended up having to replace three cells instead of the original two. Thank goodness I ordered more than two! Anyways, I'll be building a cell tester really soon so I can start testing these cells.

As far as the BMS, I kind of question if I destroyed its LVC functionality somehow and if somehow I contributed to the fact the mosfets were burning during what I presumed was normal operation. Are smoking mosfets normal for 13.5 amps? So, uhhh, yeah... I'll definitely be thorougly testing this battery before putting it back into action. I think I may... gasp... get *another* BMS.

If I do, it's definitely not going to be another Ping BMS.

 

[monster]

whats the voltage drop when you pull 20amp from a 10ah ping? that would seem a bit on the high side. 13.5amp is quite high also (but probably safe). at the moment im trying to stay above 48V under load on my ping 3V/cell

 

[swbluto]

Oh, yeah, that's a good idea. I should measure the voltage drop across the mosfets during discharge - I have a feeling they might be abnormally high although I don't really know what's "Abnormal" but anything over 1 or 2 volts sounds like a lot! Yeah, I think during the testing of this battery, I'll be creating the "cell and battery tester" I've been wanting to build for such a long time.

 

[swbluto]

Ok, did a quick "let's see if it cuts out on my scooter like it usually does when I try to hold it still" and dang, that thing took off like a bat out of hell! And, it never cut out. That's strong evidence that the over-current cut-out functionality is dysfunctional(As well with the LVC cutout - I'm guessing the "cut-out" mechanism is dysfunctional, whatever that is), but now I needed direct confirmation. I hooked up the nichrome+water load and I tested it at 20 amps, no problems. I shortened the nichrome - 53 amps? It just kept going. I shortened it even more and 73 amps?! It kept going... and then since the nichrome was so short, the alligator clips touched each other and... boom... short circuit. It was pretty amazing because it just kept flashing and sparking like fireworks under water! Wow. Did the battery cut out? Nope. Given the last way I destroyed the battery's BMS was when I short-circuited it, I have a feeling if it wasn't destroyed before this testing, it's destroyed now. Oh well, it needed replacing anyways, right? :lol:

Now this really sucks. I've had 2 bms's killed so far and this hobby just keeps getting more and more expensive....

I need to either repair the BMS or.. get a new one. The problem is is that I don't have a "rework station" so removing the NAND chip might not be practical, so getting another BMS is about my only practical option(Well, I could repair it if I wanted to, maybe, but... I just don't want to. I just want to move beyond this inferior technology.). Now... where to find one? I can tell you I'm certainly not going to use a Ping, for the lack of adequate balancing and the fact they're so easily destroyed by a short-circuit - it's supposed to protect the battery from over-current, not destroy itself in the process, right?!! Perhaps I'll use a simple "LVC board" and place a big fuse on the line and keep the BMS for charging as the charger-BMS circuitry still seems to work.

 

[liveforphysics]

You are in Seattle right? I'm 15min mins from Seattle. If you want to fix it or beef it up or whatever, you can come by my place. I have all the tools to repair most anything.

Seriously though, I don't know why you guys even mess with Ping batteries. It's gotta be the absolute most crappy battery you can buy. It's not even cheap anymore either, which was the only thing is used to have going for it.

 

[Aerowhatt]

You are in Seattle right? I'm 15min mins from Seattle. If you want to fix it or beef it up or whatever, you can come by my place. I have all the tools to repair most anything.

Seriously though, I don't know why you guys even mess with Ping batteries. It's gotta be the absolute most crappy battery you can buy. It's not even cheap anymore either, which was the only thing is used to have going for it.

Sounds like a waste of time repairing the BMS. Running the cells up to 73 amps and more with a short circuit, every cell is marginal if not toast at this point. That's why the BMS has current protection to start with.

Other LiFePO4 batteries have come down some but are still harder to get what you want. A lot of people have had success with Ping batteries. I have six in service without a complaint in many miles of use. A couple of the BMS boards modified to hold to 3C too! If you stay within their limits you get good results from them in my experience. The ones I bought were all V1 so I've had them in service for a long while. Got them at good prices mostly at auction. Now with other prices somewhat lower I might make a different choice but it wouldn't be based on reliability it would be based on C value. You can't take a product and short circuit it then run it up over 8C rates when it's rated for 3C max and expect a decent outcome. From what I've seen the people that treat Ping's batteries and BMS with a little respect see a good result for their investment. I know I have!

Lets take a blender and chop up some gravel with it . . . see how it holds up.

Aerowhatt

 

[swbluto]

Hmmm... this is very interesting.

I know that the over-current protection was to protect the cells from over-current, but I reasoned that was likely due to heat issues and thought a second or two wouldn't hurt much(It was solely a test to see if the over-current functionality was damaged). If it does unacceptably damage them, well the battery needed replacing anyways! :lol: For now, I'm planning on developing a custom LVC cutout board and using a fuse for over-current situations. The charger functionality still apparently works, so I can keep the BMS for that purpose.

And, I'm not going to defend my purchasing decision in detail but let's just say I was MUCH more of an electronics n00b when I purchased it nearly 9 months ago. The "ping battery" was much more n00b friendly than other solutions that existed at the time(and wasn't lead or something that was projected to have a cycle life at least 3 times less than LiFePO4).

And, thanks for the offer liveforphysics. It'd be nice to have access to some tools to get the job done, but I don't want to feel responsible for destroying another's machinery and I haven't identified the exact problem as of yet. But, still, it's very interesting... do you actually live near Seattle? May I ask where? I'm planning on going to the Seattle Robotics Society at Renton Technical college tomorrow and I'll be bringing my electric scooter for show and tell so I might be near the area... And I actually live in Shoreline, WA near 175th ave.

I'm curious, though, because I was under the impression you were situated in California since, if I recall correctly, Methods had convinced you to dive into electric bikes suggesting you two were geographically close to one another(or at least at one time) and I believe Methods lives in Livermore, Ca.

 

[liveforphysics]

I ate at that crappy drive-in styled pizza/burger place near 175th in shoreline just yesterday when I went to visit a lady friend.

I like about 15mins south of Seattle in SeaTac. I have lived in CA, but only for a short time, and never near Methods. We have been friends for about 8 years from being on a very tight-knit engine design forum together for years.

Don't worry about breaking my tools. All my premium stuff got stolen when my house was robbed, and the stuff I got left is stuff that I haven't been able to break, and that means I doubt you will be able to. When I need to lift a chip with a zillion legs off a board, I just set a heat sink on top of the chip, mask off the area around where the chip mounts with foil tape, and heat with a heat gun from the bottom. Generally takes about 20seconds until you see the solder turn shiny-liquidy, then you just lift the chip off with twezers. Piece of cake, quick, and it doesn't hurt the chip or the board if you do it right.

I don't think that just a few seconds of hard current will damage the cells much, or if it did, hey, no big loss, they were high Ri garbage Ping cells to begin with It would take 7 of the biggest Ping packs (48v20Ah) to be capable of suppling the power for my bike, and it would be 140lbs and a massive volume of duct-tape covered garbage. With 16lbs of LiPo battery all in a neat compact little custom polycarbonate saddle pack, I'm able to fit same power that 140lbs of Ping packs would provide me. I guess Ping packs work fine if you are looking for a 1 purchase solution to give you the absolute worst charger with the worst BMS and the worst cells with the worst duct-tape and cardboard packageing, and you never plan on having a powerful bike. Then it's perfect.

 

[dogman dan]

Clearly the ping is not the solution for your needs. But it sure is working good for my dinky little 36v bike with it's ho hum motor that so boringly gets me to work, day in, day out. I did take the tape off it once, just out of curiosity. Hey it is what it is, a battery that was better than lead last spring. The only reason pings prices got so high, is thanks to mr lau. :lol:

 

[Aerowhatt]

I don't think that just a few seconds of hard current will damage the cells much, or if it did, hey, no big loss, they were high Ri garbage Ping cells to begin with It would take 7 of the biggest Ping packs (48v20Ah) to be capable of suppling the power for my bike, and it would be 140lbs and a massive volume of duct-tape covered garbage. With 16lbs of LiPo battery all in a neat compact little custom polycarbonate saddle pack, I'm able to fit same power that 140lbs of Ping packs would provide me. I guess Ping packs work fine if you are looking for a 1 purchase solution to give you the absolute worst charger with the worst BMS and the worst cells with the worst duct-tape and cardboard packageing, and you never plan on having a powerful bike. Then it's perfect.

I guess it all depends on what your needs and abilities are. I think at best one should actually have experience with something before trashing it. Two of the ping packs I have ride as a range extender on a bike which peaks out at 9,900 watts DC input. For less than double the price of the premium lead range extender pack they replaced, I got a cut in curb weight plus at least enough cycle life to match the price of the lead extender in dollars per mile and a bonus of 47% increase in overall range. Yeah crap can treat you pretty good if you do the same in return.

Aerowhatt