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Monday, January 3, 2011

Battery History Lesson from a Nerd King


Justin Lemire-Elmore is a founder of a very small Canadian company that sells electrical supplies for do-it-yourself electric bicycle enthusiasts. His website contains a wealth of information that many thousands of DIY builders have put to great use (myself included) like this hub motor simulator. He also has a degree in engineering physics from the University of British Columbia.

Justin is a bit of a legend in the hot-rod electric bike community. He has personally designed and manufactures several gadgets to meet the needs of DIY electric bike builders.

He recently gave a 2 hour talk titled "Lead Free Since 2003" to the Vancouver Electric Vehicle Association (VEVA) about his seven year struggle with different battery technologies, which was video taped (poorly) and can be viewed by clicking on the following links (in sequence). Oh, and the battery on the video camera pooped out five minutes before the end, which explains why there are no concluding remarks: 1/6 2/6 3/6 4/6 5/6 6/6 1/5 2/5 3/5 4/5 5/5

You should also download the following PDF which will let you see what he is talking about in the video:

He sums it all up below (taken from a post on Endless Sphere): was an almost therapeutic experience to get all that off my chest too! It gave some closure to this whole chapter of trying to work out custom ebike packs with all the various Chinese cell and pack assembly companies. From now on it'll be just eZee batteries with Samsung / Sanyo / Panasonic cells and programmable O2micro BMS circuit. Don't care what's the price at this point. Just want reliability.

My own personal feeling is that unless the cells are coming from a long standing big company with years and years of expertize and R&D and internal know-how in battery manufacturing, then they're not going to come close to the standards needed for a consumer industry. Almost all the new companies eagerly selling larger format EV batteries fall way short of this category. I mean we got 4 sample 48V headway packs earlier this year, and have already had to do cell replacements in two of them. A hobbyist can put up with those kind of statistics, an industry can't.

BionX was smart and used Sony cells in their lithium packs. Much as some might begrudge them charging $1200 for a replacement 36V 9Ah lithium pack, at least their users almost always get 3-4 years of regular use from the batteries before they start to wear down, and virtually never have cell problems. Sony can't afford the risk associated with their cells having problems. In hindsight I would have so happily paid twice as much for our packs to have those kinds of statistics, and at the end of the day our customers (assuming they weren't put off by sticker shock) probably would have too.

For now, we're taking a gamble on Samsung being able to deliver a reliable LiMn ebike cell, and they are assembled into packs for eZee at the same facility that does the BionX pack assembly. It's only been 6 months that we've been dealing with them though, so too early to say if that typical lifespan will be 12-18 months or 3-4 years. I'm sure hoping it's the latter because ebike users really deserve it.

For all the talk of LiFePO4 lasting 5-10 years and thousands of cycles, we've yet to see anything firsthand that comes close to consistently delivering this in practice with the ebike grade LiFePO4. I'm sure A123's are up to the task, but I have sincere doubts about all the other manufacturers.

As for the house burning down at the end of the slides (video cutoff just before I got here), that occurred to my very close friend just this summer. She happened to have a battery pack that had all the EU ebike certifications, including the stringent UN38.3 shipping tests, with a UL/CSA certified charger. Went to walk the dog for 15 minutes with the battery charging by her door and came back to the suite in flames, with the battery pack and charger (which had been beside her coat rack and a wicker basket) right at the epicenter. The fire investigation that followed was inconclusive at determining the exact cause or event sequence that lead the pack to do this.

Just 4 months before that I was actually on a tour of this very battery facility and saw the test rooms where they drive nails through the cells, heat them up to 100oC, charge them to 10V, pound them with a sledge hammer, etc. and in all cases the cells wouldn't fail with flames. So what happened that would cause a 2 year old battery that hadn't shown a single sign of strange behaviour to suddenly burn down a house? I have no idea.

Following are a number of links documenting my experience with an electric bike I have been riding since 2005:

Videos: (video has over 700,000 hits) (view from helmet cam, with afterburner) (with trailer going uphill)

Blog posts:

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  1. You don't state which battery manufacturer was able to 'drive spikes, heat to 1000*C, or charge to 10 V", but I can tell you, FWIK, any of those things would cause a normal Li-Ion battery to catch fire. ie, those test were bogus.

    Li-Ion batteries I know of have caught fie for no known reason.
    Usually suspected to be internal crystaline growths that short the anode and cathode and cause a tiny short, leading to overheating , then a chain reaction of more overheating till the cell catches fire. Impossible to detect and hard to prevent

  2. Thanks for putting this up Russ. Wouldn't have know about it otherwise.


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