Building a Battery that will NOT cause you to wake up dead

Batteries, Chargers, and Battery Management Systems.
999zip999   100 GW

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Re: Building a Battery that will NOT cause you to wake up de

Post by 999zip999 » Feb 04 2013 8:59pm

It not just the fire but the sooth that the packs expell as this stuf will coat and stick to everything. You will need a sand blaster to remove it.

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bowlofsalad   1 MW

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Re: Building a Battery that will NOT cause you to wake up de

Post by bowlofsalad » Feb 05 2013 12:10am

999zip999 wrote:It not just the fire but the sooth that the packs expell as this stuf will coat and stick to everything. You will need a sand blaster to remove it.
This sounds like another fine reason to charge a battery in a fireplace or something.

etriker   100 kW

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Re: Building a Battery that will NOT cause you to wake up de

Post by etriker » Feb 05 2013 8:37am

dm9876 wrote:
That nfpa article is an excellent reference. (someone posted it earlier in this thread as well)

I think that we are discussing interesting things, but there is no one answer. 'safe' chemistries. quality of products etc are all relative anyway. Different choices are appropriate for different situations (budget being one of them). I feel certain that most of the bad rap on HK lipo for example is nothing to do with the quality of the cells (not that I am defending it) but other factors not accounted for (mechanical / electrical abuse etc).. people effectively configuring and riding prototype systems every morning when they are still half asleep....

I think the only real path forward in this debate is for us to collaboratively generate a kind of FMEA (Failure Modes and Effects Analysis). It is complicated since it is not just the 'battery' to be considered but everything as a system. We cannot just isolate the battery itself in the analysis, but lets not let that stop us.

maybe the wiki is a good place for the output of this discussion?

If we could achieve this, then at least people can have a structured way to assess their individual choices and a better understanding of the risks.

For each failure mode listed, the mitigations could be many. At worst it is a 'handling procedure' / manual user monitoring & management. At best, a passive defence or a highly reliable / redundant automatic management

We could even score a battery system based on weightings of probability, severity of the failure etc and the quality of the mitigation.

Dean
I hope everyone reads that. It helped me become a better master BMS.

The master BMS is human. The slave BMS is the master BMS's electronic tools that he watches over.

The slave BMS does not know if the battery is being charged in the house or way out in the yard.

The master BMS does.

Reading this forum is a good way to become a better master BMS. :)

etriker   100 kW

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Re: Building a Battery that will NOT cause you to wake up de

Post by etriker » Feb 05 2013 10:02am

One of my slave BMS tools is a Hyperion 1420 charger.

The firmware can be updated in the Hyperion 1420.

It is my job as the master BMS to make sure the firmware in the Hyperion 1420 stays updated.

I also have to make sure the firmware in the master BMS stays updated. :)

Stay on top of it kids ! :)

el_walto   10 kW

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Re: Building a Battery that will NOT cause you to wake up de

Post by el_walto » Feb 05 2013 11:21am

I just got a Hyperion 1420. It is awesome. I would recommend it to anyone messing around with lipo. Only thing i wish is that they would make it a bit more compact.

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bowlofsalad   1 MW

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Re: Building a Battery that will NOT cause you to wake up de

Post by bowlofsalad » Feb 05 2013 6:21pm

el_walto wrote:I just got a Hyperion 1420. It is awesome. I would recommend it to anyone messing around with lipo. Only thing i wish is that they would make it a bit more compact.
I don't mean to offend, but I am guessing this some how relates to not causing a battery to light on fire, maybe you could elaborate?

dm9876   10 mW

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Re: Building a Battery that will NOT cause you to wake up de

Post by dm9876 » Feb 05 2013 6:35pm

amberwolf wrote:A possible start is making the pack container "airtight", not in the sense of keeping the gases in, but in keeping any new oxygen out.
I too am interested in this approach. I was looking at building a pack using these 'pelican' style hard cases, they would provide impact protection as well.

http://www.jaycar.com.au/productView.asp?ID=HB6381

My concerns with this approach are that sealing it up is also insulating it and the heat from one failure may more readily propagate to other cells. Main concern though is ABS is flammable, with its own kind of nasty smoke and its a gamble if the failing cells would generate enough heat to burn the plastic case... any thoughts on this?

From what I can see, even the expensive pelican brand cases are ABS (not 100% sure though). Polycarbonate cases (more fire resistant ) don't seem to be available in that style, only in the smaller, water proof OtterBox style cases like this

http://www.otterbox.com/otterbox-2000-c ... lt,sc.html

Dean

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Re: Building a Battery that will NOT cause you to wake up de

Post by kfong » Feb 05 2013 10:27pm

Not sure why carbon fiber is not mentioned. This is the current approach I'm using. Nothing else could withstand my torch test. This is why the space shuttle is covered with it along with ceramic tiles. The use of LiPo bags to prevent fires works quite well. I plan to encase all my LiPo with CF this way. If I get a fire, I loose the pack and perhaps damage the bike. I consider this better than loosing the house. I would never recommend LiPo's for Ebikes, but I still use them because of the cost and power density. I charge in the garage, and always balance charge with a quality RC charger.

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johnrobholmes   1.21 GW

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Re: Building a Battery that will NOT cause you to wake up de

Post by johnrobholmes » Feb 05 2013 11:52pm

CF is conductive. Its similar to a lightly painted steel box in risk, any abrasion to the resin exposes conductive material.

kfong   1 MW

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Re: Building a Battery that will NOT cause you to wake up de

Post by kfong » Feb 06 2013 10:32pm

Easily solved by using an inner layer or two of fiberglass cloth.

dm9876   10 mW

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Re: Building a Battery that will NOT cause you to wake up de

Post by dm9876 » Feb 10 2013 8:00pm

Re: My earlier statement about ABS vs polycarbonate cases. I found some data here: http://www.tcforensic.com.au/docs/article10.html

(Celcius)
ABS: melt range 88°-125°, ignition 416°
Polycarbonate: melt range 140°-150°, ignition 580°

Also found there are polycarbonate cases available from progressive RC, They quote 6mm thick, which sounds pretty solid.
http://www.progressiverc.com/prc-hardline-cases.html

I cannot find much real data on lipo burn temperatures. Some news articles seem to quote 600 deg. C (yeah I know, solid source of data :-) but I guess is it dependent on if it just fails and vents or if it actually ignites, which might be prevented or reduced in a sealed enclosure.

I'm no thermal design engineer but I guess the temperatures reached are more determined by the rate of heat release from the batteries and how fast the heat is removed (probably not too fast in the sealed plastic case scenario)

wrapping in some heat resistant material may limit localised melting and slow the transfer of heat to adjacent cells, but it still seems that anything short of metal is not going to deal with the situation.

Also need a vent of some sort, so as not to make a bomb. Everyone says no to metal, but properly lined and insulated it seems to be the way to go and is also what all the commercial packs seem to use.

Dean

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