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

Batteries, Chargers, and Battery Management Systems.
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Re: Building a Battery that will NOT cause you to wake up de

Post by Arlo1 » Jan 31 2013 11:37am

999zip999 wrote:3000 cycles a 9 year battery ??
NMC is what Zero used for 2012 and claimed almost 500,000 km to 80% capaticy!
Does your project need a high performance motor drive, battery charger or other power electronics developed? Let's talk!
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Re: Building a Battery that will NOT cause you to wake up de

Post by mistercrash » Jan 31 2013 11:57am

I just called EIG America and talked to a guy named ''Tim'' if I heard correctly, I was inquiring about their modules because I was interested in knowing if it was possible to have a 72V40Ah module built by them. He told me that EIG America doesn't sell the modules and they are sold to companies who make different kinds of EVs. They do however sell the 20Ah cells to companies that make batteries. I told him that I can make a battery but that I am not a company so he told me I can buy a minimum of 60 cells (a box) and it would come to $6000 delivered. :|
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Re: Building a Battery that will NOT cause you to wake up de

Post by amberwolf » Jan 31 2013 2:48pm

EIG datasheet
EIG NMC datasheet.PNG
shows 1000 cycles to 80%.
Max continuous 5C.
Peak 10C <10sec.
eig1.PNG
eig1.PNG (64.71 KiB) Viewed 6281 times
About 0.25V sag at 5C vs 1C.
eig2.PNG
eig2.PNG (120.19 KiB) Viewed 6281 times

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

Post by Hillhater » Jan 31 2013 4:50pm

...shows 1000 cycles to 80%.
true,.. but that is to 100% DOD !!
What might that be on a typical 85-90% DOD cycle. ?
What is the Whr/kg for those EIG cells ?
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Re: Building a Battery that will NOT cause you to wake up de

Post by Hillhater » Jan 31 2013 6:08pm

OK, looking for a cell chemistry "safer" than RC LiPo..
what do we know about the HK LiFePo4.. ??
such as this 8.4Ahr, 4s, 13.2v , 30C, LiFePo4 pack for $75
http://www.hobbyking.com/hobbyking/stor ... _Pack.html.
Not in the A123, or EiG class maybe, but has anyone tested them ?
..Is it likely to be any "Safer" than LiPo ??
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Re: Building a Battery that will NOT cause you to wake up de

Post by amberwolf » Jan 31 2013 6:46pm

Hillhater wrote: what do we know about the HK LiFePo4.. ??
such as this 8.4Ahr, 4s, 13.2v , 30C, LiFePo4 pack for $75
http://www.hobbyking.com/hobbyking/stor ... _Pack.html.
Not in the A123, or EiG class maybe, but has anyone tested them ?
..Is it likely to be any "Safer" than LiPo ??
If it's from HK, then not really possible to say, because their QC is nonexistent.

It's "safer" in that it is *less* likely to burst into flame when the cells are contaminated or defective, simply because of the chemistry, but not any less likley to be crappy cells in the first place. ;)

If it's gonna cost you $75 (presumably not including shipping) for that ~13.2V 4s 8.4Ah pack, estimated at only ~110Wh, when you could spend the same money (per JRH) for the single brand-new EIG cell that's nearly 3/4 of that Wh and guaranteed QC and consistency. I would guess that after shipping and whatnot, as well as weeding out the defective cells in the HK packs (both DOA and early-failures, not including longer-term-failures), the EIG cells would be *cheaper* per Wh.

Hillhater wrote:
...shows 1000 cycles to 80%.
true,.. but that is to 100% DOD !!
What might that be on a typical 85-90% DOD cycle. ?
What is the Whr/kg for those EIG cells ?
Per the datasheet I posted above:
http://www.endless-sphere.com/forums/do ... &mode=view
it's 175Wh/kg for Specific Energy, and 2300Wh/kg for Specific Power at 50% DOD 10sec rate.

Energy Density is 370Wh/l, and Power Density at the same rate/DOD is 4600Wh/l.

As for the less-than-100% DOD lifecycle, I'd guess it might well be in the 2-3x (or more) range vs 100% DOD. I dunno if Liveforphysics did full longevity tests like that on the Zero EIG packs, but you could ask him, if it's publicly disclosable info.

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

Post by mistercrash » Jan 31 2013 7:00pm

What amberwolf said. A couple years back, I bought HK LiFePO4 2s2p and 3s2p packs for RC stuff and they all ended up puffing either when used or just sitting at storage charge. From the reviews of those batts it seems quite a few are just puffers for no apparent reason.
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Re: Building a Battery that will NOT cause you to wake up de

Post by Hillhater » Jan 31 2013 7:34pm

Sure, the risk with HK is their QC, but we are after a "Safer" pack, that is not going to burst into flames.
If this HK LiFePo4 "fails safe" ..IE no flames,.. than that is a major plus, and knowing that the actual failure rate of (sorted/tested) HK packs is pretty good anyway, then they could be a good option.
COST
Being realistic, JRH only has a limited supply of those EIG's, and i suspect the price of $100 / cell quoted to "mistercrash" is more likely the price we should be looking at for small quantities of cells.
So EiG would be $1.56 /Whr, ( delivered ??)
and the HK's would be $0.72 /Whr ( inc delivery from Au W/hse )
That looks like half the cost to me !
..and not a huge increase over normal HK LiPo at $0.50 /Whr

Im sure they are not as good quality as the EIG's, but they are generally available, and if they dont burst into flames on failure, then they have to be a better option than LiPo.
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Re: Building a Battery that will NOT cause you to wake up de

Post by amberwolf » Jan 31 2013 8:44pm

Hillhater wrote:Sure, the risk with HK is their QC, but we are after a "Safer" pack, that is not going to burst into flames.
If this HK LiFePo4 "fails safe" ..IE no flames,..
Not "no flames" just "less likely", by the nature of the chemistry. Problem is, HK cells appear to be commonly contaminated or otherwise not quite right, and what that does to the the flammability of the insides, we have no way to know until something happens.

There've been reports on ES of LiFePO4 small-pouch-cell packs that burned, for reasons not known but probably related to overdischarge or overcharge and likely overheating. Even a Ping pack could do so, but he appears to be using a more reliable source for cells than HK (or he is screening them out better before building packs from them), based on the types of problems reported between each kind (though there is far less feedback available for the HK packs/cells, there appears to be a higher percentage of that feedback as bad).


That's the whole problem with anything from HK or any other non-factory source for cells: you don't know what quality the cells actually are, or what kinds of contamination they may have internally. What causes them to puff just sitting there at a nominal middling voltage? Known-good-quality cells don't do that. Contamination or other chemistry or assembly issues probably do, and the results of that on flammability cant' be known without testing.

If the contamination or other issues are different between different cells, or batches (as seems likely), then testing isn't even useful, becuase unless you know what the actual issue is with the cell under test, and with each cell that you see puff (neither of which you can really know), then you can't apply the test results to actual cells in use. :(


Not to say that the HK cells might be a cheaper alternative...but they can't be known to be fail-safe, and that is AFAICT the point of this thread. ;)

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

Post by Arlo1 » Jan 31 2013 10:10pm

I like looking into other cells but you guys are kinda going off track... Here is how it is.
If you can find me a cell 100% never ever ever ever to make flames then maybe we can use that to make sure it is safer.
But what I am getting at is all cells can make fire so we need to look at how to stop that fire from becoming a bigger issue.
If you test whatever cell you chose and make it burn then try that same thing in the box how do we stop that from spreading to the next cell or out of the box to what ever else is in the garage. Where I live there is no place safe to charge out side without some rain damage or a kid hurting themselves or a thief so charging will be happening in my garage.
Does your project need a high performance motor drive, battery charger or other power electronics developed? Let's talk!
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Leaf motor controller build. http://endless-sphere.com/forums/viewto ... 27#p963227
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Re: Building a Battery that will NOT cause you to wake up de

Post by 999zip999 » Jan 31 2013 10:27pm

Buy a strong battery good c-rate lifepo4
What is the battery for ?
You match a battery and controller.
A 9v for a fire alarm and some steel wool will start a fire.

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

Post by Arlo1 » Jan 31 2013 11:29pm

999zip999 wrote:Buy a strong battery good c-rate lifepo4
What is the battery for ?
You match a battery and controller.
A 9v for a fire alarm and some steel wool will start a fire.
What i'm working on is modules.... Say ~1kwh each.
For my ebike I would use 1 module
or for my e-ysr with colossus I will use 4 modules
or for my drift trike I will use 2 modules
or my dune buggy 2 modules with 2 on charge etc.

But it really doesn't matter because Here is the problem we stray away from the cheep and powerful batteries then we loose most of the people who really need to be building this.
I will be using turnigy lipo until I can get a performance/cost wise = that is safer.
So lets say we build something that CAN save a fire from the danger and hope it will be some logical easy cheep additions to what others who have no safety can add to their build then maybe less houses will burn down. But if you try to force saggy or more expensive batteries as the safer way to do it then we will have the people who use the dangerous batteries still catching fire.
When I build a electric car is another story because the cycle life and the energy density will matter more then the power density do to how many I need for a good range.
Does your project need a high performance motor drive, battery charger or other power electronics developed? Let's talk!
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Leaf motor controller build. http://endless-sphere.com/forums/viewto ... 27#p963227
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Re: Building a Battery that will NOT cause you to wake up de

Post by amberwolf » Feb 01 2013 12:12am

I see your point. If the pack were properly built, we could use magnesium flares for cells and still not burn the vehicle or garage or house down. ;)


I expect that to properly flame-proof many batteries, it's going to make the pack larger than acceptable (and maybe heavier) for a number of uses.


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. (yes, I know that some of the stuff in cells will release it's own oxygen once heated enough--but if it's nto able to bring in fresh from the air then it will have a very limited supply, and once exhausted can no longer burn, even if the cells remain hot from the energy release and other chemical reactions themselves). There was a video posted in another thread a long while back that showed a cell (pack?) deliberately damaged/set ablaze inside a closed cash box (which isn't airtight but wouldnt' allow free airflow), so that as the cell(s) vented their gases could escape but would also push air out of the box, and prevent inflow of new fresh air. AFAICR there was no general ignition of everything, presumably because of that.

A similar test is planned for my ammocan pack, using defective RC LiPo cells in place of the working ones it has, where I will overcharge them the same way that resulted in fire in my test videos back in July (2012?), but inside the closed modified ammocan. I'll use wires the same type and size as the pack itself uses now, for exit, and bundle up some old wire in there to represent the large amoutn of pack wiring there'd be, as well as some foam padding and whatnot that would normally keep the cells from bouncing around or rubbing, etc. Then parallel wire a bunch of bad cells in there, and run them up to 5V+ at dozens of amps, which should ignite at least some of them (maybe all). Dunno when I'll get this done, as I still ahve to separate more bad cells out of some packs, to use in addtion to the ones already watiing to be used. I will also use any other bad cells I happen to have of other types (probably all LiCo, just different sizes). I probalby only have enough bad cells to make up a couple of 6s-equivalent packs, where the can actually can hold 14s2p at least, probably more. Was hoping to accumulate more donations of packs with bad cells to do the test with, but that's about it so far.

The ammocan is modified so that it has an exit hole for the wires, and those wires dont' fully seal the hole, but it is pretty small. Another way to do it was mentioned by Dogman (and others) by drilling at least one hole in the ammocan and then using very thin (possibly pre-scribed) tape over it so in the event of a fire it would rupture the tape rather than bursting the can from pressure.

Methods and/or Stochastic also discussed doing this test.


It wouldnt' mean that nothing bad could happen, but it should mean a fire-containment vessel for the pack is easy and cheap to make, as the principle coudl be applied to many shapes and sizes of metal pack containers. Other materials would probably also work.


Fire-retardant materials like Nomex between packs or cells would also be helpful. If I had more Nomex than the firefighter pants I use for riding in the cold/rainy times, I'd try the test with Nomex wrapped around some cells that arent' hooked up to the PSU so they shouldn't burn or be damaged, and see what happens to them when the rest of the "pack" ignites.

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

Post by amberwolf » Feb 01 2013 12:16am

On another note: I have been waiting for a reply from an undisclosable source (sorry, NDA involved) on permission to post some data about the EIG cells.

I've been using some pre-used (unknown conditions) cells in a long-term test on CrazyBike2 including for my lighting pack, for some time now. One thing I want to report is the safeness of these cells under a condition that would probably be "fatal" to many other cells, and the hardiness of them after the incident. It's partly documented in my CB2 thread but some details had to be left out at the time.
http://www.endless-sphere.com/forums/vi ... 39#p566839


I used to park my bike out front of my workplace, and normally no one ever messed with it, but once I forgot to unplug my 12V pack's connector, and someone turned on my headlight and a turn signal (when I didn't have a working blinker, and had to manually blink them), and it sat there on at least a ~6A load during the shift till it ran down to 0V on all cells. :(


I recharged it at a 100mA current limit, back to 4.0V/cell, using a lab PSU. At the time, expecting it to blow up and flame out, I did it outside on concrete with a metal trashcan over it...but nothing happened, except that it charged normally up to 9.6V when I had to leave for work, so I unplugged it from the charger. When I got home 5 hours later, it had actuallly gained another 0.75V, not sure why. Possibly because the outside temperatures had increased during the day (though cooled later before I got home; still might have left the pack a bit warmer than when I left).


Continuing charging at 250mA at some piont (I forget exactly what voltage I changed it), and then with no problems for a while upped it to 500mA, it reached 11.1V at about 12Ah back in it. I kept disconnecting it when leaving the house, and it always held it's voltage after disconnection from charger and meter.

The cells stayed in balance even when they were at extremely low voltages (0V up to 3V), from my periodic checks during the recharge cycle. They were within 0.02V of each other each time I checked, using the Fluke 77-III.

Eventually it got up to 12.2V, with 12.3V as the final goal (4.1V/cell). Still in balance, still no problems charging, no sign of heat or swelling or anything unusual. Charge current had dropped to 0.49A with the voltage rise. Had about 18Ah in it then. Later it finally reached full, at something close to 20Ah.


Discharge testing then began:
http://www.endless-sphere.com/forums/vi ... 99#p570899

I used the Venom RC charger from SoSauty. Some notes:
The Venom says it will do 5A discharge testing, but that isn't really true. It might do 5A at a certain total wattage, which is a lot lower than the wattage put out by the pack at 12.3V. At that voltage, it only does 2.0A. Eventually, when the pack reached about 11.8V, it increased to 2.1A, and later to 2.2A at around 11.6V. (this was the opposite of the way I wanted to do the test, but at least it was a test. Also, due to the inaccuracies of the Venom I discovered in the testing, I suspect at least a half an amp less current draw than it reported throughout the testing).

Given the Venom's inaccuracies in readouts that I've determined, there's essentially no balance issues with teh cells (it read at most 0.03V difference, and I don't think that was a real difference, just problems in the Venom itself).

There was no heating of the cells during charging or discharging AFAICT.

There is some data on the cells via Logview, but bugs in Logview I wasn't aware of led to loss of much data. Screenshots of some of the data is in posts after the link above.

I also did recharging via the Venom, which was around 4A in reality, and I was convinced the pack wasnt' going to burst into flame yet, so I started using it on the bike again for the lighting pack. At some point I got an Accucel6 from Ebikefanatic, and have been using it to recharge it as 3s (4.2V/cell...yeah, I know it's only supposed to go up to 4.15V on these cells...but it already survived a 0V event, so, what's the harm? ;)) at 5A. I haven't tried logging the charging yet, but I expect that's not 5A constant, probably a lot lower as voltage goes up to maintain wattage, just like the Venom did.


I also did a couple of 0.5C recharge tests with the big Sorenson, at 10A, from fully discharged (3.0V/cell) to max (4.15V/cell), and no cell heating. I did a similar test when I first started using the cells, though at that time I had incandescent turn signals (before Texaspyro sent me those MR16 LEDs I put in there), and was using a 4s / 16.4V pack, before I took one cell off to keep from blowing up the LEDs.


I typically use at least 8Ah before I recharge, and have a couple times let it go to 14-16Ah used just to see if it's still got the capacity it had, and so far it still does, matchign the voltages it should have according to the EIG datasheet for that SOC. I use the headlight on bright most of the time (day or night), so 6A constant load, and additional intermittent few hundred mA load with turn signals and brake light, for my typically-10-minute trip to work and back home, with occasional trips elsewhere for up to an hour and a half or so of riding time, and very occasionally 2 hours.


So far it's had maybe an 8Ah cycle every few days since late spring, maybe midsummer? I forget exactly. And usually doing similarly before the incident.


Anyhow, just to say that at least at about 0.3C discharge levels, and 0.5C or 0.25C(peak) charge levels, these cells can be killed to 0V, and still be brought back and used without issue for up to full capacity. I don't yet know how cycle life will be affected, and I have not done a high-rate discharge test because of the way I use this little pack, but in my usage scenario, there's been no discernable damage. I'd like to be able to test the internal resistance of an undamaged cell (should be <3milliohms @ 1khz) and one of the ones taken down to 0V, but I don't think I have the test equipment for that.


There is also a traction pack but it has not experienced any unusual conditions. (14s at first, then 16s; would use more but the charger I have doesnt' go any higher and I haven't gotten round making a super-long extension cord for the 220V for the big Sorenson so I could stick it in series with it, or use the Sorenson and an Artesyn "server" PSU in series for high-rate charging. So it gets charged at max of around 4A, but the charger ramps it's rate up and down so average is probably 2A or less.)

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

Post by etriker » Feb 01 2013 9:43am

So far we are all all using cells that can flame out ?

You can put them in an ammo can but those are kinda heavy for an ebike.

And you don't want to pack them away so you can't watch them close up or get to them quick if they start smoking.

No hard cases.

You are the master bms even if there is a slave bms.

The very poor HK quality control has given rc lipo a bad rep.

There is higher quality rc lipo out there ?

If I were going to make an ebike battery pack using rc lipo and did not know how to test and connect the cells I would hire someone other than hk to test and put the cells together for me.

http://www.nfpa.org/assets/files/pdf/re ... hazard.pdf

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

Post by Arlo1 » Feb 01 2013 10:33am

etriker wrote:
The very poor HK quality control has given rc lipo a bad rep.
The people on ES who never watch there indiviual cell volatages while bulk charging give RC lipo a bad name.
Does your project need a high performance motor drive, battery charger or other power electronics developed? Let's talk!
www.powerdesigns.ca
Leaf motor controller build. http://endless-sphere.com/forums/viewto ... 27#p963227
YSR build http://www.youtube.com/watch?v=BRo8r5g4NBg
Never above 4.2v never below 2.7v EVER!!!
Support me on Patreon. https://www.patreon.com/user/posts?u=6842045
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Re: Building a Battery that will NOT cause you to wake up de

Post by etriker » Feb 01 2013 10:39am

Arlo1 wrote:
etriker wrote:
The very poor HK quality control has given rc lipo a bad rep.
The people on ES who never watch there indiviual cell volatages while bulk charging give RC lipo a bad name.
Right ? They helped HK too.

I am not so sure our votes mean a lot in our elections.

When we really vote is when we spend our money !

HK does not get any more of my votes ! :)

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

Post by Arlo1 » Feb 01 2013 11:16am

etriker wrote:
I am not so sure our votes mean a lot in our elections.

When we really vote is when we spend our money !

HK does not get any more of my votes ! :)
Ive seen all kinds of RC lipo fail this way. If you over charge any cell on any brand of RC lipo it will burst into flames.
Does your project need a high performance motor drive, battery charger or other power electronics developed? Let's talk!
www.powerdesigns.ca
Leaf motor controller build. http://endless-sphere.com/forums/viewto ... 27#p963227
YSR build http://www.youtube.com/watch?v=BRo8r5g4NBg
Never above 4.2v never below 2.7v EVER!!!
Support me on Patreon. https://www.patreon.com/user/posts?u=6842045
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Re: Building a Battery that will NOT cause you to wake up de

Post by Arlo1 » Feb 01 2013 11:19am

BTW Im not saying HK lipo is the best... it is one of the worst for quality control but its again not worth the 3-6x the money for something from the local RC shop.
And remember I can not order RC lipo from ANY USA seller because its not allowed across the Canadian US boarder.
Does your project need a high performance motor drive, battery charger or other power electronics developed? Let's talk!
www.powerdesigns.ca
Leaf motor controller build. http://endless-sphere.com/forums/viewto ... 27#p963227
YSR build http://www.youtube.com/watch?v=BRo8r5g4NBg
Never above 4.2v never below 2.7v EVER!!!
Support me on Patreon. https://www.patreon.com/user/posts?u=6842045
http://www.undergroundelectrics.ca/

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

Post by etriker » Feb 01 2013 11:23am

Arlo1 wrote:
etriker wrote:
I am not so sure our votes mean a lot in our elections.

When we really vote is when we spend our money !

HK does not get any more of my votes ! :)
Ive seen all kinds of RC lipo fail this way. If you over charge any cell on any brand of RC lipo it will burst into flames.
I overcharged an A123 copy 18650 cell and it swelled way up and exploded.

I had a car battery explode in my face once when I was doing jumper cables.

I think they can all explode and trust HK lipo the least of all batteries.

On account of the ones I bought and tested and what I have read online.

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

Post by John in CR » Feb 01 2013 6:04pm

jonescg wrote:How can we make our current crop of cells as safe, convenient, failure-resistant (not proof) without compromising on size, weight and simplicity?
Simple:

1. Don't take your battery pack off the bike all the time. Plugging/unplugging regularly is at least half of the problems, though typically smaller incidents, though damage in that process quite possibly causes some of the catastrophic failures.

2. Don't charge or store your bike were it can cause damage to anything else. As long as these batteries can't ignite a concrete wall then I'm good to go and can sleep like a baby without "waking up dead", though i've been told that I snore loud enough to "wake the dead". :mrgreen:

John

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Arlo1   100 GW

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

Post by Arlo1 » Feb 01 2013 9:43pm

John We all know you have a sweet deal. But the reality is most people my self included, need to bring the e-bike or electric motorcycle in out off the rain or snow or away from neighborhood children or criminals etc.
Does your project need a high performance motor drive, battery charger or other power electronics developed? Let's talk!
www.powerdesigns.ca
Leaf motor controller build. http://endless-sphere.com/forums/viewto ... 27#p963227
YSR build http://www.youtube.com/watch?v=BRo8r5g4NBg
Never above 4.2v never below 2.7v EVER!!!
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Arlo1   100 GW

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

Post by Arlo1 » Feb 02 2013 12:50am

Here is a link to inside the telsa pack on a rav4
Ill put this in the first post as well.
Does your project need a high performance motor drive, battery charger or other power electronics developed? Let's talk!
www.powerdesigns.ca
Leaf motor controller build. http://endless-sphere.com/forums/viewto ... 27#p963227
YSR build http://www.youtube.com/watch?v=BRo8r5g4NBg
Never above 4.2v never below 2.7v EVER!!!
Support me on Patreon. https://www.patreon.com/user/posts?u=6842045
http://www.undergroundelectrics.ca/

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

Post by bowlofsalad » Feb 02 2013 2:07pm

If the risk of fire is great, perhaps some type of flame retardant container would be the way to go. One option that comes to mind is a small furnace (example http://menards.com/main/heating-cooling ... c-6884.htm), perhaps with an exhaust of it's own. There are a lot of options there, I don't know if there is any shock risk involved in a metal container for such an idea, but you could insulate (electrically) at least the handle to a door if needed. If you really wanted to eliminate the shock risk, a brick or mason style fireplace might be acceptable.

This seems like a fairly viable option for a charging container. It likely sounds costly, it sorta does, but the cost of either a very high quality series of batteries or a new garage/home seems to be a far greater expense. It would be a hassle to remove the battery from the bike, but I am sure there are plenty of quick release options. There are plenty of DIY fire place options, but you could probably find some cheap used locally.

Originally, while reading this thread, I was imagining a locking, outdoor, old (maybe broken) refrigerator with a padlock on it. I don't know what would happen inside of that box though, maybe the doors would get blasted open even with a padlock. Either way, it's less likely someone is wheeling off a fridge behind a garage, and nobody will accidentally (kids) get into it. Personally, I like both ideas, each come with pros and cons. But I think this concept is great as it puts a lot of my own fears to rest concerning this issue.

I've been doing a lot of research on batteries for a while, and fire has been a great worry for myself for a while, but this might snuff those worries out.

TL;DR Charge the battery in a fireplace.

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

Post by dm9876 » Feb 04 2013 8:21pm

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
Last edited by dm9876 on Feb 05 2013 12:30am, edited 1 time in total.

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