syndr0me

iTrader: (32)

The damage done by regular overcharging is cumulative. That is, over time, the battery becomes more dangerous and volatile, increasing the chance of a fire. Whether or not it would play out like that with these packs in the real world is up for debate, I suppose. Just because it doesn't burn up the first time doesn't mean it won't the 50th time. Be smart. Don't cheat.

Verndog

iTrader: (16)

Exactly. And at the club racing level or even local event level I dont see that happening, especially if they already dont check for approved motors and weights. Likely it will take a burned face, death or some catastrophic event to get serious on this issue. Hope its not me, or someone I'm close to.

Is this enough to make people want to stop this??

http://www.lewrockwell.com/vance/man-burned.jpg

ta_man

iTrader: (168)

Someone posted a table on HobbyTalk a while back that showed resting voltage vs state of charge (or discharge). Here it is:

100.00% 4.20 8.40 12.60
90 4.13 8.26 12.39
80 4.06 8.12 12.18
70 3.99 7.98 11.97
60 3.92 7.84 11.76
50 3.85 7.70 11.55
40 3.78 7.56 11.34
30 3.71 7.42 11.13
20 3.64 7.28 10.92
10 3.57 7.14 10.71
0.00% 3.50 7.00 10.50

If the packs are over the 7.5V I have found that discharging the SMC packs to 7.4V at .8C (4A for the 5000 and 3.2A for the 4000) will leave them ending up at 7.5V (resting) for an estimated 35% charge.

If they are already under 7.5V charge 'em up a bit then discharge as above.

The .8C wa determined by experiment to see what discharge rate would leave them at 35% with a 7.4V discharge cutoff.

mkdut

iTrader: (19)

While I agree that it is important to charge Lipos via the recommended methods, I think your illustration is a little extreme. I also don't see the same over sensationalized statements being made about NiMh. If ever there were a reason to make such statements it would be against these batteries. How many Nimh batteries have you seen violently explode versos lipo? My guess is you would be lucky to have seen a lipo even fail let alone explode yet it is somewhat of a common occurance to have a Nimh pop at local events.

By the way, I have run the SMC 5000 the last two race weekends and these batteries are awsome. Especially when I peak them at 10 amps prior to the main.

Verndog

iTrader: (16)

IMO there is good reason for the fact you haven't seen a LiPo fire. Most people are following the safety rules of charging. Listen around and you'll find that isn't always the case. My point is only being made on intentional overcharges. Overall lipos are safer and there will be less incidents....until people begin to push the window and ignore the rules.

You may think that illustration is extreem but is it? A LiPo burns hotter, longer and more extreem then the quick boom / pop of a nimh. Here is a pic of what a lipo fire did to a car and the work area...tell me you've seen even close to that damage with NiMh...then tell me that pic is extreem.

mkdut

iTrader: (19)

Yes I still think it's extreme. I do agree with your description of a Lipo fire but the only way that this would fit your description is if the person was sleeping on the Lipo while it was being charged. More appropriately a Lipo fire has more to do with the facility burning down than individual harm. The reverse is true for a Nimh explosion

Nice picture, though I have seen worse with a Nimh fire when a cell vented and caught fire in the back of someones vehicle. Also why don't you post a link to the story behind this photo?

And, what was this person doing running Lipo in a 1/12th?

mkdut

iTrader: (19)

Found it on my own. It's funny that you post pics that illustrate your overcharging of Lipos but in fact the story behind the fire is far from that.

http://www.rctech.net/forum/showpost...&postcount=168

catastrophic yes, due to overcharging no. And 50 cycles with a drop to 2950 mAh? Sounds like a bad pack to start with.

Grizzbob

iTrader: (2)

Extreme or not, it's really a simple matter to prevent. Just as ROAR seems to be doing & as Tamiya is doing with the TCS, it's EASY to just put a voltmeter to a pack & if it reads too high, they can't run(until they at least pull it down a bit). And it seems to work, as I haven't heard of a SINGLE incident with any TCS or ROAR race since they began to allow LiPos. I think as long as all tracks that allow LiPos follow their example, it'll work out just fine, a little dilligence should go a LONG way.....

Verndog

iTrader: (16)

The pic is not to illustrate overcharging, where do I say that? I said this is a pic of a lipo fire, only meaning to show the potential damage that can occur once a lipo has ignited. Go back and read my earlier posts, I'm asking how much risk, and would like to avoid being burned blinded or worse.

http://www.rctech.net/forum/showpost...&postcount=955

I doubt sleeping on a lipo is required for serious injury / burns....ever seen someone lean over the table to see charger status?...measure distance from their face to the lipo that nobody is enforcing sacks to charge.

If all your comparisons with nimh are true, where are all the nimh sacks, and why are they allowed to air transport nimh but not the majority of lipo??

mkdut

iTrader: (19)

You make a statement and show a picture by doing so you try to make a link between the two whether you say so or not.

Ah, now you are reacting to my extreme example.

My point exactly. Where was all the concern when the M80's were going off in the pits? The reason they are not banned is because there have been no highly publisized failures of Nimh and to say the are not banned is also not true. I had AAA Nimh confiscated in Puerto Vallarta for safety reasons.

Don't get me wrong I thing you're right regarding the seamingly lack of concern, I just think you are going about it the wrong way.

Still Bill

iTrader: (16)

This thread is supposed to be about the SMC 4000/5000 lipo packs. I didn't expect it to be hijacked with thoughts about the safety of lipos...A separate topic.

Please, please, please...Start your own thread about the lipo safety aspect and have at it.

Thanks. From a guy that always charges his lipos in a sack.

Verndog

iTrader: (16)

It started as a question to a knowledgeable battery authority that may well include SMC packs. Someone with clout IMO needs to push tracks to check voltage to keep lipo safety high. The only other push from what I can tell is going to come after people or property become victims to those needing to win.

If people want to turn a blind eye to it today fine, hopefully they wont have to turn 2 blind eyes to it tomarrow. I'm done with it...back to SMC related posts.

stocker

iTrader: (2)

good info, thanks!

Jake S

iTrader: (67)

ugh any pictures of this smc saddle pack lipo?

Danny/SMC

iTrader: (2)

Here is a picture of the prototype pack in a D4. The production packs will be shipping out to our distributors at the end of this month.

We will take pictures of the production packs when they come in.