It sounds like a good way to get a fireplace going.
2 Likes
I’m no expert but since I’m bored and having my morning coffee at 1pm on Day 24 of the quarantine, my thoughts: The first is that the explanation that unbranded batteries are a factor is just click bait, as Rob goes on to say (“the origin of the footage is unclear”). Clearly he doesn’t know that these particular batteries are branded or not. I’ve had great experience with unbranded cells with a little bit of research.
The second is that there’s a few different battery chemistries out there, and judging by the explosion those are Lithium Ion, which are notoriously explodey, especially under certain circumstances. A much more stable chemistry is LiFePO4 (“LFP”), which is why those are the ones used in RVs.
One of the issues with Lithium Ion batteries is that they’re fragile, and if over discharged (which can happen even from sitting) will form little short circuits between the internal cells called dendrites that make them really dangerous to recharge. That’s why if you find a big LiOn battery pack thrown out somewhere the prevailing wisdom on places like Endless Sphere is you shouldn’t use it, because you don’t know if its history. (I personally still use them, and haven’t had any issues, but I mark them and treat them with extra caution).
And that’s one HUGE battery pack, looks bigger even than an eBike battery, which makes me think it might be for an electric motorcycle… And who knows how damaged the thing is by over discharge from limping home and things like that.
And incidentally every eBike and similar that I’ve seen uses LiOn batts (the explodey ones), which is why they all say not to charge them indoors. Not that people listen…
Oddly so do our laptops and cellphones, which don’t seem to explode that often, nor do they have a recommendation that we should only charge them outside… Given how frequent fires are in the eBike world I have no explanation for that. Better BMS (“battery management systems”) maybe? I know there’s a few fires, but given how many laptops and cellphones there are in the world, doesn’t seem that many to me.
And incidentally Tesla uses the explodey chemistry too, but they have famously excellent BMS. And a fire here and there…
6 Likes
Sitting right next to me, in my living room:
I may need to get a fire extinguisher…
Edit: Both the battery and the charger are from, what I believe to be, trusted brands.
3 Likes
For those wondering what you use a battery like that for. I have a small polyester boat and a trolling motor. It’s absolutely lovely to boat around, making almost no sound at all. The top speed can be beaten by a moderate jog and the first step down from that is basically walking speed, but we don’t have anywhere to be except for on the water.
2 Likes
Ha that is pretty funny. Safe chemistry though:
And a sweet charger, I love everything Victron makes. Cruising around on a lake with an electric motor sure sounds super fun right about now.
1 Like
Daaaaang it!
I was gonna post that
1 Like
I noticed the battery is labeled “LFP,” so it should be the safer LiFePO4 chemistry.
1 Like
Yeah, lithium batteries do like to burn - uncontrollably. That happens with exposure to air. So think, auto crash or say an overheating event which warps the case. There are now some formulations coming on stream that are not problematic under heat. But there have been a lot of electric buses catch fire and there is no putting them out. Also, Tesla cars that have spontaneously combusted while in the workshop following an accident.
1 Like
Yeah once you pierce a LiOn battery, it ain’t going out. To be fair, gas tanks are pretty combustible too.
I wonder if Tesla is moving away from their old chemistry now that they’re building their own batteries? I’d be really surprised if in 5 years the batteries powering electric vehicles bear much resemblance to the current chemistries. But who knows, we’ve kept gasoline around for a long time despite it being one of the most flammable substances on the planet.
1 Like
(1) Use a good BMS and charger compatible with your battery.
(2) Charge it in an enclosure (box) that will at least keep some of the explodeyness inside.
Really basic lithium battery stuff but I guess not all that common knowlege.
1 Like
One of the more unfortunate episodes in EV history was when the patents for large-format nickel-metal-hydride batteries wound up in the hands of Chevron, which promptly buried them under onerous licensing conditions. It was only a couple of years ago that the patents finally expired, but in the meantime the world moved on.
3 Likes
I think its just the thing with lithium that you can’t just pump the electrons back in. Back in the day I heard of a guy who was charging individual NiCd cells by connecting them to a car battery. He would hold the cell in his hand and when it got warm it was charged.
Those days are gone. You need a charger with smarts. You need to monitor temperature and your charger needs a model of the charge state of the battery. Listen to Elon.
Interestingly with electric bike scale lithium ion battery packs, that’s exactly what they do. This is the general type of charger most people use:
They just pump out a steady 42 volts (for a 36 volt battery pack) and wait for the pack to reach the same voltage. For better or worse!
I’d be very surprised if that’s the full story of what is going on in the system though. Typically the individual cells (somewhere in the 3-4V range) in a pack will have a load leveling circuit across each of their two terminals, to accommodate non-identical aspects of the series elements. As @Michael_R_Smith states above, to effectively charge there should be a current sensing variable voltage element (possibly in the e-bike pack itself) that presents a higher voltage to a lower-charge state battery and ramps it down according to an established curve as detects the current flow diminishing. There’s even a sort of Xeno’s paradox effect where it takes longer and longer to charge the final percentage, so in a sense the batteries never reach “full”. (caveat - I don’t do e-vehicles, but have built some systems with LiFePO4 banks)
Aha good point, there’s of course a BMS (battery management system) built into the battery pack, which in theory levels out the cells.
Here’s a cool vid of a battery pack being built, including the BMS installation (that board on top of the thumbnail is the BMS):
The BMS’s are getting fancy, some even allow bluetooth connections so you get battery info straight from the BMS.
1 Like
That’s a great build vid, & sweet spot welder! Appreciate his liberal application of kapton - (might help prevent the OP subject). Found out the hard way once that it’s not safe to assume 48VDC can’t conduct through the human body, (hint - blood is more conductive than dermis).
2 Likes
I didn’t know that Harbor Freight sold lithium batteries.
1 Like
Also, it looks like that socket is somewhat overloaded. It looks like all the nearby electronics are going into it.
I had a similar situation years ago, when computer power supplies came with a switched power out socket so you could power your monitor from it.
In my workplace we figured that plugs which would go into the power out socket were great for international travel because you could always get a local power cable for it, so I built a power board which plugged into my computer power supply to switch my reading lamp, speakers, printer, etc.
It was a nice setup until years later my wife plugged a 2400W fan heater into it…
Video from China,
You can see the milk brand and red bags as well as the decoration.
