what are the signs of an unstable li-on battery?

Hi ESFMs,

I have a question about how to tell if your lithium battery could explode on that next charge.

The reason I'm worried about this is because I had a bad experience with my first battery a few years ago that resulted in the burning down of my room.

My current battery is occassionally turning itself off and recently, if won't connect when plugging it in after several attempts. It eventually becomes reliable again but occassionally, it just drops out. At first I thought it was a bad connector but after changing them twice, it still does it.

Ive been noticing that the light on my charger occassionally flickers green/red.

Are these signs of a bad battery? Are there clear signs that a battery could be unstable and potentially combustive? I really don't want another fire on my hands.

Clinton

Those could be signs of an unbalanced battery, but that in itself is an early warning of a bad battery.

The big signs of an impending fire is any of:

1. A sweet smell ( the polymer leaking)
2. Puffing or even packs which are no longer parallel from top to bottom (may need to open the pack to check. This is indicative of delamination and/or gassing)
3. Excessive heat during charge or discharge (excessive internal resistance oe short)

In addition to Sunder's suggestions you might want to check cell voltages. If they are all within about .2 volts, great. If not, the balancer (if installed) may not be enough to keep the cells in balance - in which case one cell will almost surely see an overcharge, leading to a higher risk of fire.

More info what battery ? How you charging ? Bms ?

999zip999 said:

More info what battery ? How you charging ? Bms ?

Click to expand...

Its a 48 volt 30 AH battery, 4A charger. When I charge it at home, I just have it plugged into a single power. Though I use an extention cable so I don't have to unstrap my battery from my frame all the time.

I also charge it at cafes occasionally and a couple of outdoor power points. Rarely more than an hour of charging in those instances. Except at cafes. I usually charge there for 2-3 hours. But again, the cafes are occasional these days. Maybe once every couple of weeks.

And yes, it has a bms.

billvon said:

In addition to Sunder's suggestions you might want to check cell voltages. If they are all within about .2 volts, great. If not, the balancer (if installed) may not be enough to keep the cells in balance - in which case one cell will almost surely see an overcharge, leading to a higher risk of fire.

Click to expand...

How do I test for cell voltage? Will I have to open and pull the pack apart? What equiipment do I need? Other than multi meter?

Hey, I think I know why my battery keeps shutting itself down. I think my charger might be tripping the bms into shutting the battery down.

My charger has gotten worn a fair bit around the leads and I think that it may be damaged inside of something. 2 times that I had this issue was after catching my charger flicker green and red.

I got home today and went to charge it with this crappy charger and this time it wasn't responding. For fear that the battery was totally dead this time, I plugged it back in to my controller but there was no spark and no power. I speculated that maybe it was shutting itself down because the charger might be faulty so I fetched my other charger (slightly weaker 3A instead of 4A) and it too didn't respond at first.

I checked the battery with my watt meter and it wasn't responding. I panicked a little for a while and proceeded to open the pack to see if there were any loose connections. Everything seemed fine but I only removed one side of the pack and only looked at the power leads, the charging leads and that one purple wire coming from the bms and Pairs with the black power lead.

After sealing that one side up and putting the battery back in its case, I tried the watt meter again and this time it was responding. I tried my crappy charger and I heard a loud spark from inside the charger. Unplugged it instantly and I could smell something had burnt. Then I tried the spare charger and I found it only works if I angle the connector a certain way.

I'm not sure why my plug is only charging if I angle the lead a certain way but could this be the source of my battery shutdowns, or is it more likely the dodgy charger?

The strange thing is that I just tested that charger 2 weeks ago and it didn't seem to matter what angle I put it, it charged either way. The charging plug is always straight and the connector is one those 2.6mm ones that just slide in, so I don't see how that could be putting much stress on the connector.

How do I volt test the charging connector?

Also, still would like to know how to test each volt test each battery. So I need to pull the whole pack apart? Will I have to break their connections and then re-solder them?What equipment do I need?

No problem can we have a link to your battery or picture of the half open battery. There should be a collection about 13 sense wires maybe 14. Start at neg end as # 1 and make a writen list. Important. Like .
1. 3.99v
2. 3.85v
3. 3.55

13. Xxx volt
I still don't know what chemistry you have ? This will tell you state of charge.

The spark when you connect to power can wear the connector, making it only touch when you angle it. Anderson power poles for example are rated for 100,000 cold connects, or 250 full power connects. The inrush current from a 30Ah eBike battery would be high... likely higher than the rating for PP45s.

Not sure what you're using, but if its a spring connect type connector rather than a pin and socket type connector, its probably that for the loose connecrion issue.

As for the health of the battery bit, 999zip999's advice is good. Show us photos and take some measurements and we'll go from there.

ClintBX said:

How do I test for cell voltage? Will I have to open and pull the pack apart? What equiipment do I need? Other than multi meter?

Click to expand...

Just a meter. You have to take the pack apart enough to get to either the end of the cells or the BMS board, where all those voltages are brought to. Check each with a decent meter. NOTE - do NOT short the pins on the BMS board! If you do, then you will at best melt the wires to the battery pack; you will be shorting the cells out directly.

Clintbx yes be careful don't cross probes when checking voltage of cells. I tape or put shrink tube on probe so only the end shows. Plus where do you live ?

Sunder said:

The spark when you connect to power can wear the connector, making it only touch when you angle it. Anderson power poles for example are rated for 100,000 cold connects, or 250 full power connects. The inrush current from a 30Ah eBike battery would be high... likely higher than the rating for PP45s.

Not sure what you're using, but if its a spring connect type connector rather than a pin and socket type connector, its probably that for the loose connecrion issue.

As for the health of the battery bit, 999zip999's advice is good. Show us photos and take some measurements and we'll go from there.

Click to expand...

I'm talking about the charging cable. Not the discharging one. As I said, its a simple slide in connector. Not sure the name of this charging connector.but its also labeled as a 2.1mm.

I'll attach an image of the connector. While I'm at it, I'll also show what blew in my charger.

I autopsied the charger and something blew alright. Not where I had expected.it though.

Before plugging in the new charger check to make sure the polarity is right. So you let the magic smoke out. Still need to know state of charge of battery pack. So let's see the cell voltages.

I think you guys might be right. There might be a weak cell. Since charging with my spare charger, it only seems to charge to 53.5 volts. Before that, it would charge full to 55v.

Oh, by the way, not sure if I mentioned this. This is a 48v 30ah pack. I think its a 13s. And its chemistry is LiniCoMn204. Can't details on the exact configuration.

I bought this pack on aliexpress but I used the app on my phone so I don't have the browser link. But heres the share link I just found. Hope this helps.

battery 48v 30ah lithium ion triangle Battery for 1500W motor
http://s.aliexpress.com/ZJbYjiYj
(from AliExpress Android)

I want to do the cell test. I'm just working up the courage because I'm afraid of messing up my pack entirely and its still under warranty. I dont want to void that.

Chinese batteries rarely have a working warranty by the time you ship it there and ship it back you just paid for a new battery. They many send you a replacement cells for you to fix or they may send you a BMS for you to replace or a replacement charger.

999zip999 said:

Chinese batteries rarely have a working warranty by the time you ship it there and ship it back you just paid for a new battery. They many send you a replacement cells for you to fix or they may send you a BMS for you to replace or a replacement charger.

Click to expand...

Aside for the 2 way shipping costs, the time for it to get there and back is a massive inconvenience. But I'll keep that in mind about getting them to send a replacement cell or bms. I might need that.

Okay, I'm just about to open my pack and do this. I'll take some photos and get a reading on each of the cells and report back.

I've never done this before. Wish.me luck.

Good luck

Okay, managed to do it. After testing each of the 12 sets of cells (I guess I was wrong about the 13), I got a pretty consistent reading of 3.47v for each. There a couple of 3.48Vs.

I also tested all 3 major ground wires and they all read at 45.2v. Might I add that I did this right after a long day of riding and was nearing an empty charge. 45.2v is exactly what my throttle indicator and my watt meter were reading too.

Though, I might add that on one of my retests with the ground wires to the bms, I thought I saw 46.2 on all 3 of them.

Anyway, I don't know what that means. 3.47 doesn't sound low but correct me if I'm wrong.

Here are some snapshots.

I think you've missed a string. 12 x 3.47 = 41.64v

You said the pack voltage = 45.2v There's a missing 3.56v somewhere, which is roughly one string.

The good news is if that's the case (and I'm rounding a few 1/100ths of a volt there), the pack seems reasonably well balanced, but most packs are top balanced. You want to charge the pack up and measure again?

What is the voltage of your charger ? Do be careful that thing is very alive. A lot of stored energy. Or it will teach you.

999zip999 said:

What is the voltage of your charger ? Do be careful that thing is very alive. A lot of stored energy. Or it will teach you.

Click to expand...

Well, the label on it says 54.6v but I would like to know for sure. How do you test a charger? I have that slide in 2.1 mm connector. How would I test through that, or would I have to take the connector off?

Sunder said:

I think you've missed a string. 12 x 3.47 = 41.64v

You said the pack voltage = 45.2v There's a missing 3.56v somewhere, which is roughly one string.

Click to expand...

Yeah, I thought that was odd. Either I miscounted or I left one out. Though I checked and rechecked the whole row. At first I tested them in pairs, i.e; 1&2, 3&4, 5&6...etc to 11&12. But then, I noticed that in one of the tutorials, you have to test in a cascading sequence. I.e; 1&2, 2&3, 3&4...etc. So I did that and then I counted in my head only 11 combinations. I assumed that maybe the positive and the negative on each end would be the 12th. I didn't test that but wouldn't that just give me the voltage of the whole pack? Anyway, I factored that 12th 3.47 but even then, that adds up short of that 3.56v or so.

Sunder said:

The good news is if that's the case (and I'm rounding a few 1/100ths of a volt there), the pack seems reasonably well balanced, but most packs are top balanced. You want to charge the pack up and measure again?

Click to expand...

I was afraid you were going to say that. I'll have to do that one before I leave the house I guess.

ClintBX said:

Sunder said:

The spark when you connect to power can wear the connector, making it only touch when you angle it. Anderson power poles for example are rated for 100,000 cold connects, or 250 full power connects. The inrush current from a 30Ah eBike battery would be high... likely higher than the rating for PP45s.

Not sure what you're using, but if its a spring connect type connector rather than a pin and socket type connector, its probably that for the loose connecrion issue.

As for the health of the battery bit, 999zip999's advice is good. Show us photos and take some measurements and we'll go from there.

Click to expand...

I'm talking about the charging cable. Not the discharging one. As I said, its a simple slide in connector. Not sure the name of this charging connector.but its also labeled as a 2.1mm.

I'll attach an image of the connector. While I'm at it, I'll also show what blew in my charger.

Click to expand...

5.5mm x 2.1mm DC male/female socket connector.
Plug charge in to mains only and turn on, with your meter probes simply poke one in the center 2.1mm hole and the other on the connectors outer casing, outer casing is neg and inner is pos.

Thanks Hemo. I tested the charger and it has a reading of 53.4 volts.

Just putting 2 and 2 together here. Would it be accurate to say that the main reason my battery is only charging to 53.5 volts is because that's what this charger's voltage true rating is at?