John in CR
100 TW
cal3thousand said:
Thank goodness that wasn't a headlamp.
"LiPO", another "be careful" warning...
- Thread starter pdf
- Start date
Thank goodness that wasn't a headlamp.
23skidoo
10 W
- Joined
- Feb 22, 2012
- Messages
- 98
Thanks for sharing this report.
So to have a safe system without bms or cycle analyst or even voltage monitoring:
1) design the bike so that the battery wire is unplugged routinely to turn the bike off. This can also be used in the rare event of controller run-away. The battery should be stored in a fire safe area anyway away from the bike.
2) use either a route which is known to be within the bike's capacity or set a LVC on the controller such that the weakest cell is still in the safe range.
3) balance charge routinely ( this isn't that hard if you set up connectors well).
4) store and charge the battery in a fire-safe place.
Would this explosion and fire have been contained in an ordinary fireplace?
So to have a safe system without bms or cycle analyst or even voltage monitoring:
1) design the bike so that the battery wire is unplugged routinely to turn the bike off. This can also be used in the rare event of controller run-away. The battery should be stored in a fire safe area anyway away from the bike.
2) use either a route which is known to be within the bike's capacity or set a LVC on the controller such that the weakest cell is still in the safe range.
3) balance charge routinely ( this isn't that hard if you set up connectors well).
4) store and charge the battery in a fire-safe place.
Would this explosion and fire have been contained in an ordinary fireplace?
speedmd
10 MW
Thinking the grill may be a good place, as long as I pull the tank out so no one preheats it by accident. 
10 kW
23skidoo said:
About the ordinary fireplace, yes, that would have been fine, with the following caveats. 1) there was a lot of smoke. If the fireplace vent is not open, you will have some pretty hellacious smoke damage to deal with. Don't underestimate what a PITA this will be either. Had a friend go through that from a grease fire. And 2) it looks like some sort of goo (don't know how else to describe it) was propelled a few feet away when the cells popped (they don't "explode" as was inferred earlier. The pressure eventually ruptures the pouch with a loud pop). Presumably the goo was burning as well but not sure about that.
I like your list. I'll add that the reason I posted this in the beginning is that while, from a single cell level, what this scenario entailed was dramatic, from an AVERAGE pack perspective, it would not have appeared extreme. Some cells were flat and some were around 3v, leading to a low pack voltage but one that could in fact be recharged. There is a lot of badly referenced information on the net about using LiPO for vehicle applications. I want to emphasize this, not for those already using LiPO correctly and not for those not using it, but for people starting to get into LiPO. A lot of people are bulk charging LiPO. Done judiciously and in concert with cell level checking, I assume this is probably relatively safe although I would not swear to it. I am not advocating or decrying BMS vs anti-BMS, LiPO vs. anti-LiPO or anything.
It is really not that hard to forget to disconnect and have a controller soft-switched off kill a pack. Unwiring a pack for balance charging is kind of a pain; that is why we bulk charge after all. The tendency may be to try to "rescue" the pack by forcing the low cells up to chargeable state and then balance charging. This will "work" and the pack will, in fact, balance charge. However, this pack is (or at least some cells at any rate are) history. Dispose of any bad cells. That is my message. Probably worth more than you paid, in this case. If you are already treating LiPO with the proper respect, this is not for you!
LiPO is awesome. Small pack, big discharge rate and high capacity. But respect it. Just Google "LiPo fire"
(for example: http://www.flyinggiants.com/forums/showthread.php?t=51563)
I am willing to bet this guy never thought, "Hmmmmm. I could burn down my house with my family inside but what the hell, let's give it a go!". Here is my message: It is probably easier than you think to get momentarily stupid or lazy.
I don't know how many, if any, LiPO fires result even with judicious monitoring. Maybe none. But I do know people get stupid and lazy.
sharkmobil
10 W
Okay, all emotions aside, how do you "properly" restore a diminished LiPo cell? I left a pack with a 2s-6s monitor for week, the whole pack got ridiculously unbalanced. Seems kind of crazy, since both items are being sold by HK as a symbiotic pair with no fine print.
Anyways, I could spring A123 18650 cells to life by giving them a gentle zap of 18v, don't think that will go well with LiPo pouches?
Anyways, I could spring A123 18650 cells to life by giving them a gentle zap of 18v, don't think that will go well with LiPo pouches?
Ykick
1 GW
sharkmobil said:
Sorry, but if you can't figure out how to manipulate series cells back into balance you shouldn't be messing with RC Lipo. Step away from the lipo my friend....
cal3thousand
10 MW
We need to reiterate the LiPo is an ADVANCED PERFORMANCE chemistry. It should be treated and respected as such. Like Nitrometane compared to diesel fuel!
One must FULLY understand the chemistry and the underlying risks and care requirements. If done right, you won't kill anyone. If done wrong...
What would scare me is seeing any cells in my pack VERY low. if it doesn't say 3.x-4.x V, I have concerns. In the 2.x V range and I'm VERY concerned. If I saw a cell get down to 1.x V, I don't trust it AT ALL. wouldn't let that thing charge unless in a controlled situation. It's getting pulled from my pack and treated like a crackhead cousin.
If you can't live with those requirements, don't use LiPo. It's not for saving money, it is for performance! Want a battery you can abuse? look elsewhere.
One must FULLY understand the chemistry and the underlying risks and care requirements. If done right, you won't kill anyone. If done wrong...
What would scare me is seeing any cells in my pack VERY low. if it doesn't say 3.x-4.x V, I have concerns. In the 2.x V range and I'm VERY concerned. If I saw a cell get down to 1.x V, I don't trust it AT ALL. wouldn't let that thing charge unless in a controlled situation. It's getting pulled from my pack and treated like a crackhead cousin.
If you can't live with those requirements, don't use LiPo. It's not for saving money, it is for performance! Want a battery you can abuse? look elsewhere.
10 kW
sharkmobil said:
First, an answer to your question: If all cells are above 2.7, just put it on a balance charger. It will work fine.
If the voltage was below 2.7 in any cell, get rid of that cell. If you either can't or don't want to bother with that (some people have luck with this, I find it too tedious), get rid of the pack.
If the balance charger gives you an error condition, get rid of the pack.
This is not emotion, but is based on experience. If a cell gets damaged, I believe something irreversible happens to the chemistry of the cell and it effects the internal resistance. At that point, you have some cells that have high internal resistance mixed in with some that are fine. When you try to charge this pack, it is going to keep discharging the cells that are OK to keep them in line with the sick ones. The charger can only dissipate so much energy through the tiny balance resistors and I don't think the chargers are made to deal with cells that are at significantly different levels of internal resistance.
What you describe is exactly what I was trying to accomplish. What I determined is that I was not able to successfully resuscitate the cells that had gone way low. I am not sure what the definition of "way low" is, but I've seen the rule of thumb 2.7v several places. I think there is probably a time dependent part of this process and that dipping to, say, 2.0 instantaneously and then recovering to over 2.7 is probably OK but I don't know.
Second, I'd seriously consider Ykick's advice. You can fiddle with your charger settings or a single cell charger to get a damaged pack to charge, but the result is not worth it and the potential hazard is definitely not worth it.
sharkmobil
10 W
Ykick said:
You are excused. Thanks everybody else for information.
speedmd
10 MW
Interesting the pockets / swelling in the bad cells can not be reversed. They must get something like the bends sickness and develop many internal shorts also. Wonder if charging slight puffies in a vacume chamber would help at all. Lipo reminds me of electrolytic capacitors, tons of storage and one tiny short develops, and they are toast. Would be a real improvement if the chemistry / construction could self heal like poly caps.
Ykick
1 GW
Thanks for this thread pdf - RC LIPO WARNING is a good thing even if the truth hurts.
Diesel - Nitro comparison is quite accurate. BMS or not, RC Lipo is NEVER plug & play. I would never, ever leave unattended current (even a few mA) flowing on these bad boys. The notion of "zapping" these cells in an attempt to revive is simply head-shaking....
Diesel - Nitro comparison is quite accurate. BMS or not, RC Lipo is NEVER plug & play. I would never, ever leave unattended current (even a few mA) flowing on these bad boys. The notion of "zapping" these cells in an attempt to revive is simply head-shaking....
arkmundi
10 MW
See Floont's precautionary tale - moral of the story - LiPo is high risk and unnecessary, since LiFePO4 is wholly adequate to our needs and much lower risk.
gwhy!1
100 kW
If you don't what to risk having a battery fire then don't use any kind of battery, as any battery can, and do cause fires.. never think that one type of chemistry is safer than another as this will lead to problems , treat all chemistries with the SAME respect or you will get it in the backside at some point.
10 kW
gwhy! said:
This is untrue and dangerous advice, with all due respect (I like your builds by the way). Treating all materials the same because they are molded into the same device leads people to saturate in their attention to real danger. Note that US airports were on "code orange" alert for better than 10 years after 9-11. This was ridiculous. People simply can't treat every battery as a signifcant potential fire hazard. How many batteries are in your house right now? In your fire (smoke) detector for goddsake.
Posting from another thread:
No, battery type is not irrelevant. LiCo oxide decomposes at a much lower temperature than any other lithium chemistry, 150 deg C. LiFePO4 decomposes at 310 deg C. Then atmospheric oxygen is not required to support combustion and the fire is self-sustaining, catalytic, and very hot. It is simply not true that chemistry is irrelevant. All batteries can burn. Some much easier than others. It is a fact. For the above, see Journal of Power Sources, Volume 226, 15 March 2013, Pages 272–288. But we have to disabuse ourselves of the notion that "all batteries burn so therefore the potential hazard is equal". It just isn't. All alkanes burn also but I am a lot more careful with gasoline than kerosene for a good reason.
RC LiPO is potentially more hazardous. Use it if you like but use it with appropriate care or use a different battery. Yes, a car battery can cause a fire, but at what frequency per installation?
gwhy!1
100 kW
pdf said:
how can you say that this is dangerous advice .. any energy source should be treated with respect,,
I think its more dangerous to give the impression that one type of battery chemistry will never cause a fire when in real life this is not true..
anyway thanks for the shout out about my builds
speedmd
10 MW
Agree, any one of these ebike batteries is a instant on high current welder ! Having had shorts develop in the past on small mower size battery systems, I can say from experience to be careful with any of them.
999zip999
100 TW
I had a fire with round cell Konions. Just moved them from one spot to another all pos. ends straight up. The voltage below 2.2v and some lower had not been charged in 6 mos. just moved them and up in fire they went. Used tool batteries. Vented fire out the vent and lit the battery next to it and so on.
cal3thousand
10 MW
gwhy! said:pdf said:
how can you say that this is dangerous advice .. any energy source should be treated with respect,,
I think its more dangerous to give the impression that one type of battery chemistry will never cause a fire when in real life this is not true..
anyway thanks for the shout out about my builds
True. We can't say that there are NO risks for LiFePO4 (diesel is still combustible). But there are definitely higher risks with LiCo (Nitrometh)
For my current build an 18s 4p battery was made out of 12 HK Turnigy Nano Tech packs at 8000 maH each. This makes a total of 75 V at 32 Ah when fully charged.
Prior to assembly all cells where charged individually with a 1 cell charger. This process takes time but is well worth the effort. At exactly 3,85 V i left all cells sitting there for 2 month.
in one of the packs one cell had lost 0,34 V. I could probably have used it but decided not to. For safety reasons it was swapped with a fresh one.
After assembling the pack it was, to this very day, only bulk charged a couple of times.
To ensure a fast, secure and error free connection time after time, a custom plug with 42 pins was utilized. After plugging this into the bikes dashboard, all cells are accessible via the charger.
The 3 installed battery medics show me each cells voltage. While riding along these displays are checked every now and then. To me this is way better then trusting those often faulty bms systems.
According to my cycle analyst, the pack has done 178 cycles so far. With no signs of capacity loss.
Another vital issue with Lipo is the correct storage voltage. Even though this means you´d have to give the pack a final charge before riding, this will prolong the packs total lifespan. In my case the cells are balanced to 3,85 V. Even if the bike just sits in the basement over night this is the way to go. A fully charged pack will die faster. Over the winter the cell voltage is checked on a weekly basis.
So far i´ve had no lipo fires around me.
Prior to assembly all cells where charged individually with a 1 cell charger. This process takes time but is well worth the effort. At exactly 3,85 V i left all cells sitting there for 2 month.
in one of the packs one cell had lost 0,34 V. I could probably have used it but decided not to. For safety reasons it was swapped with a fresh one.
After assembling the pack it was, to this very day, only bulk charged a couple of times.
To ensure a fast, secure and error free connection time after time, a custom plug with 42 pins was utilized. After plugging this into the bikes dashboard, all cells are accessible via the charger.
The 3 installed battery medics show me each cells voltage. While riding along these displays are checked every now and then. To me this is way better then trusting those often faulty bms systems.
According to my cycle analyst, the pack has done 178 cycles so far. With no signs of capacity loss.
Another vital issue with Lipo is the correct storage voltage. Even though this means you´d have to give the pack a final charge before riding, this will prolong the packs total lifespan. In my case the cells are balanced to 3,85 V. Even if the bike just sits in the basement over night this is the way to go. A fully charged pack will die faster. Over the winter the cell voltage is checked on a weekly basis.
So far i´ve had no lipo fires around me.
pixelzpusher
100 mW
- Joined
- Apr 10, 2013
- Messages
- 45
I've been working with lipos for 8+ years now in the RC hobby and last year, got into the e-bike craze. Before getting into e-bikes, I've never heard of "bulk" charging. One guy on this forum recently lost his house from bulk charging 35S packs. If that's what he did, that's over 140 volts being charged!!! I've never charged more than a 6s pack on my smart charger and have never heard of bulk charging until I came across endless-sphere forums.
The bottom line with lipo and any battery chemistry is controlling risk. Lipo is riskier than other battery chemistries, but doesn't mean other chemistries have no risk. Bulk charging anything is adding risk. Look at it this way. If you bulk charge 35s and each cell is out of balance by .01 volts, multiply that by 35. That means one cell, with the least amount of resistance, can be overcharged by .35 volts. If each cell is out of balance by .02 volts, then you can overcharge one cell by .70 volts and so on. If you charge only a 6s pack, you reduce the risk and over charging voltage of unbalanced cells a lot less.
No matter if you have a BMS or not, it won't save you from unbalanced cells during a charge. The BMS is similar to an external battery balancer. Some are better than others, but the basic bms that comes with a high voltage 48v pack is a battery balancer. It can only re-balance your cells at a certain amperage. It will not keep up with a battery charger. If you charge your lipo at a conservative 3 amps, 3000 milli-amps, that's still 20x more amps than your balancer is balancing. My external battery balancer and even smart chargers, will only re-balance individual cells at 150 milli-amps. Lipo users need to check their cells on a weekly basis to see how badly cells are out of balance. Your charger won't know which cells are out of charge. It will only top off the pack at the voltage setting based on the pack size, 6s, 8s, 10s, etc.
Things to reduce risk that I do:
- Charge your lipos while you are in the same room. Do not charge them unattended.
- Charge lipos in a lipo fire retardant sack.
- Do not charge more than 1C.
- Do not bulk charge. I've never charged more than 6s packs at 1C.
- Store your lipos in a metal can with a latch.
- Stop using packs with high unbalanced cells. Keeping them in use is penny wise, pound foolish.
- Get an external battery balancer and balance them often.
These recommendations will not guarantee nothing will happen, but it greatly reduces risk. Again, all battery chemistries have some risk. It's reducing the risk that's important.
The bottom line with lipo and any battery chemistry is controlling risk. Lipo is riskier than other battery chemistries, but doesn't mean other chemistries have no risk. Bulk charging anything is adding risk. Look at it this way. If you bulk charge 35s and each cell is out of balance by .01 volts, multiply that by 35. That means one cell, with the least amount of resistance, can be overcharged by .35 volts. If each cell is out of balance by .02 volts, then you can overcharge one cell by .70 volts and so on. If you charge only a 6s pack, you reduce the risk and over charging voltage of unbalanced cells a lot less.
No matter if you have a BMS or not, it won't save you from unbalanced cells during a charge. The BMS is similar to an external battery balancer. Some are better than others, but the basic bms that comes with a high voltage 48v pack is a battery balancer. It can only re-balance your cells at a certain amperage. It will not keep up with a battery charger. If you charge your lipo at a conservative 3 amps, 3000 milli-amps, that's still 20x more amps than your balancer is balancing. My external battery balancer and even smart chargers, will only re-balance individual cells at 150 milli-amps. Lipo users need to check their cells on a weekly basis to see how badly cells are out of balance. Your charger won't know which cells are out of charge. It will only top off the pack at the voltage setting based on the pack size, 6s, 8s, 10s, etc.
Things to reduce risk that I do:
- Charge your lipos while you are in the same room. Do not charge them unattended.
- Charge lipos in a lipo fire retardant sack.
- Do not charge more than 1C.
- Do not bulk charge. I've never charged more than 6s packs at 1C.
- Store your lipos in a metal can with a latch.
- Stop using packs with high unbalanced cells. Keeping them in use is penny wise, pound foolish.
- Get an external battery balancer and balance them often.
These recommendations will not guarantee nothing will happen, but it greatly reduces risk. Again, all battery chemistries have some risk. It's reducing the risk that's important.
SamTexas
1 MW
Exactly! Unfortunately, this simple fact does not register with some members here.pixelzpusher said:
And this is just one of the many deficiencies of current BMSes.
meelis11
100 W
How much does it help to put LIPO to charging bag?
I doubt that bag can survive 6S 5000mAh lipo or two in one bag, maybe it gives you extra minute or two to react if you have smoke alarm nearby and it goes off?
I doubt that bag can survive 6S 5000mAh lipo or two in one bag, maybe it gives you extra minute or two to react if you have smoke alarm nearby and it goes off?
Ykick
1 GW
meelis11 said:
Not much but at that point any containment is better than none!
I've found old cookware (5qt pots) to be handy vessels for RC Lipo charge/storage. They take a lot of heat and have handles that might be useful if trying to move flaming bricks to a better location. Not advised, of course but better than nothing.
My MAIN rules - never charge unattended and always check every cell before and after charge. They charge at high rate so it's relatively easy to do the former. I sometimes break the latter rule but only when riding my usual commute and pack voltage winds up within a few mV's of where it should be for the end of that commute. Any deviation is cause for concern.
Frequent visual inspection (puffers) along with "smell test" is another useful RC Lipo survival technique. Any odor of sweet solvent and there's likely a pouch rupture to be found.
I know alternatives are beginning to make inroads and that can't happen soon enough but lack of sensible, proven, methods of interconnecting and overall pack size still present tough obstacles to overcome IMO. In the meantime, I'll stick to nitro but only if willing and able to baby and carefully qualify every cell in a pack.
cal3thousand
10 MW
Method's Detector add a layer of protection by cutting charge on cell level HVC. If your charger fails or if your packs are WAY out of balance and you bulk charge, it will cut current <--- that's the most crucial part to remove when something is awry, the current.
liveforphysics
100 TW
For those saying it's because LiCoO2 off-gasses some O2 at 150C that makes it dangerous, why are the laptops/phones/tablets most of us have collections of around the house not burning down?
If you're reaching 150degC for some reason, that reason is both causality and the source of the problem (whatever that reason may be).
QC and materials quality on RC LiPo seems to be in a race to the bottom, likely driven by price wars.
Cans/confinement just means you get a shock wave as well as flames.
If you're reaching 150degC for some reason, that reason is both causality and the source of the problem (whatever that reason may be).
QC and materials quality on RC LiPo seems to be in a race to the bottom, likely driven by price wars.
Cans/confinement just means you get a shock wave as well as flames.
