LiPO PSA - How Not to Bun Your House Down

Morning all (or whatever it is where you are),
I had a good scare last night that provided a stark reminder of why we treat LiPO (and all batteries really, but particularly LiPO) with the respect and care we do. Most who read here regularly are generally well aware of the dangers and how to mitigate them, but not everyone, and a reminder never hurts anyway.

I charge my LiPO outside on a cement surface and at least 18" away from anything flammable, but I have sometimes slacked a bit on how close it is to any flammable objects. Don't be me, don't slack on safety.

Last evening I went outside and hooked up a pair of 4s parralell LiPO for a quick bulk charge and came back inside. That was making a mistake before I even started. It was late, I was tired and distracted, and there was no good reason it needed charging right then. Don't charge before bed or when you're just not paying attention. Well, I proceeded to forget I put those on the charger, until about an hour or so later when my gf and I hear these popping noises. I immediately knew what it was and ran outside, hoping I wouldn't find everything already in flames. Luckily it wasn't quite there yet. The two packs were puffed out to balloons, split open, and smoking. Ohshityouidiot.gif

I had left these packs far too close to flammable objects including a large outdoor carpet, my bike itself, and some assorted bike stuff. Those objects in turn could have easily spread the fire to the house itself eventually if left unattended. I quickly unplugged the packs from the charger, grabbed them by their wiring harness, and tossed them far into the gravel driveway where they could do no harm. This was actually not very smart and I could have hurt myself because about a minute later one of those packs exploded in flames, and I do mean exploded! If I had been holding that when it went up I'd probably have been blinded! I did need to get rid of it ASAP but I should have taken a second to protect myself first. Again, don't be me.

It was quite the show, and my gf was shocked at how much energy a relatively small battery can hold. After the pyrotechnics settled down I buried both packs in gravel to let thermal runaway do its thing and safely expend all their energy into the rocks.

I realized what had gone wrong fairly quickly, it was my fault and a stupid mistake. I had not changed my charger settings and it was attempting to charge my 4s LiPO to 20.75v (5s @ 4.15v/cell). The charger just kept dumping energy into these poor things well past their capacity to hold that energy, and boom was the inevitable result.

Kind of scary. If I hadn't been right there to hear those initial pops as the first few puffed cells popped there is a very high chance I'd have come out to a full blown fire by the time I realised anything was wrong. I am actually glad it happened though because it turned out okay and was a priceless reminder to never slack on safety, especially when other are involved (my gf and my beautiful 2 month old baby girl)!

From now on I will be doing a couple things differently. Outside or not I will be charging inside a fireproof container. I will be keeping a large bag of sand/dirt nearby to dump into that fireproof container in case of fire (water or fire extinguisher will not work!). I will also keep a pair of safety goggles and fire resistent gloves nearby. And above all I will just be more aware and safety conscious from here on.

The energy density of these things is crazy, don't forget it or underestimate the damage they can do. Safety first! Have fun, but stay safe!

If the charge source does not automate the cycle termination

based on **some sort** of algorithm to judge when the pack is full

it is not a charger.

PSUs, DC-DC voltage converters etc are not safe, unless you are sitting there with an ammeter and DMM watching and manually stop-charging yourself.

Actually just adding a HVC control to cut the upstream input to your source is a good idea, no CV stage needed, "charge to" a V setpoint and Stop.

Ideally both automating the process, the latter as backup for the former, as a good BMS acts s a failsafe for when the charger fails.

Which would still not justify walking away for long if this is happening indoors or even near an occupied dwelling.

Shit..

You know what, i tried to be the "poster child" for safe lipo usage and even i have had some close calls. I had the best protocols. I had the most expensive and accurate balancing charger money can buy, which produced me graphs and showed me the balance of all cells in real time. I taught a lot of people how to use lipo safely.

I've seen a pack that was shipped to me emit smoke on it's own without any abuse early into this hobby.. and a sales rep at hobbyking actually sent me some new multistars 'for review', thinking i'd continue to say good things about the company.. and they shipped me one pack that was puffing and another with 2 cells that had low voltage. I disposed of both.

If they're trying to get someone to be an influencer and they ship 2/2 bad packs then just imagine what the general public is getting. As far as i know, quality control has not improved since then.

For your own good i am hoping you feel a little skittish about lipo from now on!

I still like the idea of lipo but i think 21700's in an agnuism 3d printed cell holder is the next best thing..

john61ct said:

If the charge source does not automate the cycle termination based on **some sort** of algorithm to judge when the pack is full it is not a charger.

Click to expand...

Problem is that:

1) there's no way for a 2 terminal charger to know what voltage the pack wants; anything bigger than about a 3s could be one of several S numbers. Example - a 4s battery at 4.0vpc looks exactly like a 5s battery at 3.2vpc.

2) You can have an amp-hour safety - but then you have to enter the amp-hour capacity of the battery. And that's subject to user error. AND it's not foolproof anyway. If you plug in a half-charged battery of the wrong S-number it will still be able to put in enough energy to damage cells.

3) You can have a thermal safety, or ID line to identify the battery, or mandatory-to-use balancing connectors, but that requires battery packs that support that.

You could solve this by placing requirements on batteries - all batteries have to have thermistors, or ID lines that tell the charger the S number of the battery, or overcharge protection, or balance connectors that must be used. Lots of ways to do that. But then you'd get a hodgepodge of standards and people will still build their own batteries anyway without that stuff.

Well it seemed obvious to me that the owner knows what is required and selects the right charger, and/or programs it correctly

as appropriate for the pack.

The actual Ah capacity can be unknown, so long as the owner "rounds down" for safety / longevity in selecting / programming it appropriately.

Of course user error can be fatal, just as in dealing with any high-energy fuel / hardware.

Buying a single non adjustable charge source per pack category, each with incompatible connectors maybe?

swapping connectors is not hard.

I completely agree it takes a certain amount of intelligence, common sense / knowledge / skills experience and caution / attention to detail / sobriety etc

along with using all that to select the right gear, develop solid checklisted procedures etc

in order to engage with this hobby safely.

JackFlorey said:

1) there's no way for a 2 terminal charger to know what voltage the pack wants; anything bigger than about a 3s could be one of several S numbers. Example - a 4s battery at 4.0vpc looks exactly like a 5s battery at 3.2vpc.

Click to expand...

The iCharger is actually smart enough to figure this out. It will ask you what cell series you want to charge at after making it's best guess in bulk mode. It also remembers your last setting.

It's also expensive AF.. but we know what a lipo fire costs... a lot more than the premium for an icharger, lol.

I never understood people thinking a decent charger should cost a small fraction of what a good pack costs.

Especially at high voltages over 1000W, $300 is dirt cheap for reliability, IMO even if not too adjustable.

Even secondhand, or dumb PSUs and DCDC converters with no stop-charge intelligence

but then you need to add the cost of good BMS or other HVC.

Getting good balancing circuitry, same deal, people thinking that's worth less than a family meal out. . .

First rule of LiCo chemistry management:
Never let it charge without direct supervision.

I trust no tech, because tech does fail sooner or later. LiCo fire is slow to start, and gives warning signs that you can’t miss. You will never burn a battery pack that you are watching, because you will have plenty of time to stop it.

The safest charging is bulk and fast. Buy high C-rate LiCo, charge it in 10 minutes. You will never be tempted to leave them charging alone. Charge just before riding. Monitor heat, and voltage at individual cell level. If you never discharge below nominal voltage, all cells will keep within reasonable balance. When they start to need balancing occasionally, it is time to start shopping for new ones.

Trying to stretch the life of LiCo is accepting a loss of performance and a risk of discharge fire. If you buy the best, run your own quality cycling test before use, and manage strictly, they might last 500-600 cycles before losing 20% capacity. Most are losing 20% capacity after 300-400 cycles. This 20% capacity loss is the red line, after which they need balancing every time and their safe C-rate is very low. Most of the time, they will start to heat during fast charging, well before reaching that much capacity loss. LiCo is not a long lasting chemistry, it is performance oriented. Modern BMS and conservative charging may trick you into thinking LiCo can be safe and last long. Tricks that may even make you think that cheap LiCo can be safe, but that is all bullsh*t. If long life is a priority, don’t be a fool, choose another chemistry.

There you go, you are watching. I was fast asleep when my house burned down. I don't watch my shit charge, but its sure as hell outside when I charge it. Nothing combustible anywhere near it.

As for this case, the mistake is clear, charging a 4s pack with a charger set to 5s. Makes me think, time to wipe the 14s charge profiles from my satiator. At the moment I have only a 6s lipo pack for my mower. After Chinas new year before I buy anything new.

Those packs might have not exploded, but when you tossed them it caused more damage. Easy to do, I have held an over discharged lipo in my hand. It was hot enough to melt the shrink, so you do want to get it away from you fast. After that one, I started keeping a flat shovel handy.

Problem is dont parallel charge lipos in bulk. Lol.

Parallel charging is dangerous, well known, in the hobby world. We started with pigtails.. and they were quickly found to be dangerous.. then moved to supposedly " safe parallel" boards.. and they are even not the best, even though they are fused from cell imbalance issues.

Just dont. Unless I am there, at the field, I never parallel charge my hobby lipos, that which I have alot of big ones for my helicopters.

Dont parallel charge hobby grade lipos. Lol.

A real balance charger would have noticed and safety code error out in an instant, would not have even tried to charge. You never use a bulk charger with hobby grade lipos in parallel. In series I have charged up to 20s without problem. Only 1p though.

10 years ago I brought a lot of used Makita packs with the green Sony vtc 5 cells I think. When I opened some up they would shot flame out of the top With out pulling cells from case just the top off.
These were returned Makita packs that were supposedly tested. I think they are just charged up to 12 volts and put in the mail. maybe they were dropped in water or something or something else but there was a lot of defective Makita packs out there. Yes garage fire.
I brought 35 packs and he only found 20 packs the next day he found 15 more outback right next the rejected pack ??? When they came there was a Canadian postal strike so they sat on the docks for a month when I got them allow them or at 8 volts not 12v . Not only that he was getting all these Makita battery packs for free. Well that's what happens when people get greedy.

Thanks for all the great replies. Hobby LiPO can be great stuff, but it's not worth losing your house or even lives over, which is a real risk if you don't treat them with the respect and care they require. I did not. Batteries have come a LONG way in recent years and the power density is incredible, treat it as such, like it's a 10 gallon drum of highly flammable fuel, because it basically is. Stay safe and have fun!

john61ct said:

Well it seemed obvious to me that the owner knows what is required and selects the right charger, and/or programs it correctly

Click to expand...

That's one hell of an assumption, even for DIYers.

Many people barely know how to connect a charger to the battery correctly, and also remember to plug the other end of the charger into the wall. A relative of mine actively *won't* charge his trike, even though it's as simple as plugging the AC cord into the wall (the other end is fixed to the trike) and somehow expects it to magically work anyway.

I've known plenty of people that have trouble charging a celphone or other device; heck, where I work the little scanners we use are often completely discharged when I come in to work, because no one will listen to me when I tell them the VERY SIMPLE steps to ensure they are seated in the charger and actually charging! A significant percentage of the time they're not even IN the charger at all, just sitting on a desk!

When charging actually requires changing (or confirming) settings on a charger...good luck with that.

theloadedquestion said:

...Hobby LiPO can be great stuff, but it's not worth losing your house or even lives over, which is a real risk if you don't treat them with the respect and care they require.

Click to expand...

Today, lots of round cells are the same LiCo chemistry, and ebikes are often LiCo powered without the owners being aware of the dangerous chemistry they are charging everyday. Those are even more dangerous, because they break one important rule of LiCo management: do not enclose in hard casing. That is making a fire risk, an explosion risk. Then, they rely on a BMS and automated charging, that are often very good but still; tech does fail sooner or later. Those ebike owners are living in an illusion of safety, trusting what they purchased and charging anywhere close to combustible materials, even in their home. As they are aging, the LiCo fires from round cells are now outnumbering the RC Lipo fires.

The thing people find amazing when they have one, is how big a fire a 500wh or so size lithium battery fire is. In my case, the fire was 1500 wh of cells. It went up really fast, within 2 min of it starting the bike had started a fire that fully involved a motorcycle full of gas and a car just filled with gas. Car fires are big too, and I had one in my house.

By the time I got pants on, and ran out the front door to try to put the fire out, the garage door had melted and collapsed, and flames were shooting out the garage door 40 feet tall.

Yeah, charge that shit outside.

I guess the bright side is, you got outside, and with your pants on.