LiPo battery charging station -

macirish

As we require bigger and bigger batteries - charging them becomes an increasingly risky proposition.

For your consideration - here's a charging station that might mitigate the risk involved.

A steel drum and some concrete blocks. The block goes in the bottom of the drum, the battery goes inside the block. A piece of metal window screen goes over the top of the drum

In the event of an explosion the drum contains the fire - and the screen stops the flames.

Thoughts?

Anyone have the equipment to test this concept? This would make a good youtube video.

MikeDYur

I think the concrete block alone would be enough of a safety factor, plenty of space for gas expansion. Even if you put a flat block on top. The shrapnel that would be involved in an explosion would be lightweight, so there isn't anything that would crack the block, except the initial pressure of the explosion.

xanadu

That would be much better than what most people have. RC fields have similar concrete surfaces for charging lipos.

I use ammo boxes, with lipo bags of questionable quality inside. 1 battery per bag, 2 bags per box. I hope I never have to find out if they don't work.

I would love to do some lipo fire testing, but I'd have to drive 2 hours to the desert.

MikeDYur

xanadu wrote: »

I would love to do some lipo fire testing, but I'd have to drive 2 hours to the desert.

Controlled explosions in the city are frowned upon these days, some of the stuff I done as a kid with BP or match heads would get more than a few neighbor's attention.

xanadu

Yeah, especially around here, no so much after the rains but that will change again. I can't help but mention during the drought I was extremely paranoid about flying in a dry field. Lipo storage did not bother me as much as the potential to ignite a field surrounded by houses.

Bottom line is you really can't be too careful. Safe storage and safe flying, for everyone!

macirish

There's some youtube videos of ammo box LiPo explosions - not encouraging. Ammo boxes or concrete appear to resolve the issue most of the time if they are outside and away from any structure.

I read about a longtime RC shop owner - who apparently had a long history with LiPo batteries. He had a batch charging for a meet - left the shop for just a few minutes - came back to a burnt down business.

With the barrel, block, screen combination - I was looking for a way to charge inside my shop - but even that may be unrealistic.

Yes, I know that properly handled there is a small risk - but you can't throw a blanket on a LiPo out of control - at that point the ship has sailed.

Duane Degn

Have you seen the bags intended for use when charging LiPo batteries?



It looks like Parallax only sells a small one but there are all sorts of sizes available online.

There are videos showing how well these things contain the flames. I've heard LiPo cells really stink when they burn. I keep intending to move my charging station from the basement into the garage so if there's ever a fire the smoke won't stink up the house.

Here's a link to a video testing one of these bags with a small(ish) battery.

I think it's hard to bet these sorts of bags for containing possible flames from a charging LiPo pack.

Edit: FWIW, I use a bag like the one shown above when I charge my LiPo packs.

macirish

Here's the you tube I found about this.



Looks like a good choice is an ammo box without sealing the lid - but even that probably has it's limits.

One way or the other none of these tests look like something my wife would forgive me for if it happened in the house...even if it didn't burn the house down.

garyp

Yikes, I build chargers and charge single cell lithium (cell phone type) batteries all the time
should I be worried :S

macirish

Short answer, yes. Lately EVERY battery I get has large print warnings about NOT charging the battery unattended. You can bet this means they (the industry) - know that this is a big hazard - and they want some insulation from the inevitable lawsuits.

My guess (and it's only a guess from the videos on you tube) is that the Li-Po bags are sufficient for smaller batteries.

Longer answer -

But even then - if the bag is on your desk or workbench - and lets loose, you'll probably have a mess to clean up.

Larger batteries letting loose (no definition of 'larger') will be an exponentially larger mess.

Battery design that pushes the limits of size (Samsung cellphone problems) or isn't manufactured to high quality standards present the greatest risk. The Samsung batteries have blown up without warning.

I haven't seen any indication that there is a standards organization (such as UL) putting their stamp of approval on LiPo batteries. We all live in a cocoon with incredibly dangerous energy within hands reach - but standards and engineering make it safe. LiPo battery technology appears to have outrun those organizations.

The charger is a critical piece of the problem - if it doesn't stop automatically - the battery is going to overheat and explode - that much seems to be a given.

garyp

Thank you,

Does anyone know if there is a difference between Li-Po and Li-ion, as far as charging and fire hazards are concerned.
I have been using the MCP73863 chip as my charger. The datasheet says it works for both.
I limit the charge rate to ~1/2C, and the cut off voltage to 4.1, to extend battery life. I'm hoping this also lowers the risk.

sleepless in Wisconsin :0

Duane Degn

garyp wrote: »

Does anyone know if there is a difference between Li-Po and Li-ion, as far as charging and fire hazards are concerned.

From what I've read, a Li-Ion cell is a LiPo in a can. I think the can reduces the fire danger a bit.