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NiMH veteran, needs a crash course in LiPo

NiMH veteran, needs a crash course in LiPo

Old 08-11-2008, 09:09 AM
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Originally Posted by OTE_TheMissile
Yeah I think I'll hang onto the bag. I'd like to keep using the phrase "I'm on fire tonight!" strictly as a metaphor for my on-track performance
That and I think lipo's have a tendancy to make people lazy, and they leave their packs in their cars and trucks while charging them since they only need one pack per vehicle. In hte last year I've watched two people catch their cars completely on fire, when a pack had a problem, and watched the car melt to the ground. And I heard about another guy that burned his Caddy's engine compartment out when he had his charger and pack hooked to his car battery. These things burn and spark and skyrocket like they're napalm and not just blow up like nimh's. Using the bag just develops good, safe, habits.
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Old 08-11-2008, 10:49 AM
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Originally Posted by szakcajaru
Good advice Pete, except for the "return the bag" part. After running lipos for a couple of years now, and watching a few other folks' go up in smoke and start quite a blaze, IMO it's an item well worth having if for no other reason than a safety precaution. Better safe, than sorry.
szakcajaru, im sorry anout that, you are correct...and I understand. I guess I have just been really fortunate then not to have one burst or see it happen near me.. Mike sorry, keep the bag. i dont need a fire at my house you lipo noob.
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Old 08-11-2008, 10:57 AM
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Hehe, you're also talking to the guy that had 2 throttle return springs, an O-ring wrapped around the carb neck and throttle arm, and a failsafe/onboard temp gauge in his 1/8th Buggy.

It's like helmets or racing seats, they're just not things you should cheap-out on
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Old 08-11-2008, 11:35 AM
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eww.not you got me thinkin about it, and maybe i should require the bags.. but then I would have to sell tham at my shop...
and I think they are like 20$ arent they?

I also need a fire extinguesher down there...
man., now im all worried.
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Old 08-11-2008, 01:48 PM
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1. I really can't recommend a charger with the specifics you set out, because i've been using an ICE for a couple years now and never really looked at another charger.

2. yes. the one I use is an astro blinky balancer. does the job pretty well.

3. yea it'll just dump but without a cutoff you'll run the risk of ruining your pack.

4. lipos do work under cold conditions. they just output more power when they're warm. Some packs do warm up during discharge and it's perfectly normal. Now, leaving it in your truck won't harm it, just as long as you don't short out the terminals. if that happens then your lipo goes bye bye.

5. All you have to do to store your lipos is discharge them down to 3.7v per cell and you can even toss them into the freezer. for some reason they LOVE the cold when stored.

6. Depends on the pack really. some claim between 100-200 cycles. others have 300 cycles. The first sign of a lipo going south is they don't take anywhere near the mah during charging they once used to.

7. 4.9 amps. never more than 1C for a pack. It doesn't matter if the manufacturer claims otherwise, you never charge over the rated mah. to find out the charge rate you take the mAh of your pack; in this case 4900mah, and divide by ten which gives you 4.9 amps.

besides, there is no benefit to charging higher than 1C. Do you really need to risk the pack puffing up on you just so you can save twenty minutes on a charge? not in my book it's not.
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Old 08-11-2008, 02:23 PM
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Originally Posted by RC Corral
eww.not you got me thinkin about it, and maybe i should require the bags.. but then I would have to sell tham at my shop...
and I think they are like 20$ arent they?

I also need a fire extinguesher down there...
man., now im all worried.
ROAR rules require them
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Old 08-11-2008, 02:46 PM
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Originally Posted by RC Corral
I also need a fire extinguesher down there...
man., now im all worried.
Sometimes sand is the preferred method of suppression.

ROAR Event Safety Specifications

Rule 1.5.16: At all ROAR events, functioning portable UL approved 2-1/2 pound minimum, ABC rated dry chemical or halon fire extinguishers, equipped with capacity gauges, must be in the pits and at trackside.

Tracks must have two (2) 5 gallon buckets of sand one at pit entrance and pit exit. Also, the track must have several 5 gallon buckets of sand placed
in the racers pit/table/chair area.
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Old 08-11-2008, 05:26 PM
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ok. Im on the case.

I gotta get the latest rules downloaded.

Im still working on the spectator barriers to be roar legal.

but yeah. Mike. LiPo


youll never go back.
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Old 08-11-2008, 06:27 PM
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Oh I know that. Remember I'm the one running with the theory that the NiMH batteries being produced today are low quality so that the battery companies can put more funding into LiPo packs and push the public to buying them.

I mean c'mon...I used to get two years out of my NiMH packs before they got too slow to race with, this last one I bought halfway through last winter electric season about 6-7 months ago and now it's 100% toast

Hell, those Epic Dreadnaught 3000 sticks I bought for the 6x6 some 4 years ago were next to useless when they were new...but they haven't got much worse in all that time.
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Old 08-14-2008, 05:16 AM
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OK, so until I get my own charger...my Old Man has a Dynamite Vision Peak that has a LiPo setting rated for 2-3 cells, but it can only go up to about 2.5 amps.

Thoughts?
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Old 08-14-2008, 05:55 AM
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Originally Posted by OTE_TheMissile
OK, so until I get my own charger...my Old Man has a Dynamite Vision Peak that has a LiPo setting rated for 2-3 cells, but it can only go up to about 2.5 amps.

Thoughts?

No biggie, it will just take longer to charge them up. It won't hurt them to charge them slower, and it has been my experience that LiPOs don't really get any benefit by charging them at a higher amperage rate as the old NiCD and NiMH cells did.
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Old 08-14-2008, 06:34 AM
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Cool cool

Now, something else I'm wondering as I worked on my late model last night:

Say I'm charging my pack, it's in the bag and all, and for whatever reason it goes off. Is there anything at all that I can or should do or try to do?

Unplug the charger/charge lead, try to get the bag on the ground or at least move it so the vents aren't pointed at anything that could catch fire? Or should I just get the hell away from it and go for the nearest fire extinguisher/sand pail?
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Old 08-14-2008, 06:42 AM
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Originally Posted by OTE_TheMissile
Say I'm charging my pack, it's in the bag and all, and for whatever reason it goes off. Is there anything at all that I can or should do or try to do?

Unplug the charger/charge lead, try to get the bag on the ground or at least move it so the vents aren't pointed at anything that could catch fire? Or should I just get the hell away from it and go for the nearest fire extinguisher/sand pail?
Sand sand sand......... it has to be extinquished somehow, things don't burn without oxygen. Halon I suppose would work, others might be questionable.
I use a bag at the track but at home I have a clay pot I stole from the wife I put them in while charging, and my plan is, if a problem develops I just take the whole thing outside and flip the pot over in the dirt.
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Old 08-15-2008, 08:27 AM
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Originally Posted by RC Corral

I have never balanced the cells, but if you built a simple comparator circuit, you could balance them yourself.

Pete
So you don`t really need a balancer ? I`m gonna be making the switch soon and learning about lipos as I go .
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Old 08-15-2008, 08:55 AM
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Sounds to me like lithium balancers serve the same purpose and have the same importance as a nickel tray: do you absolutely need one? No, but will they increase the useful life and consistency of the pack? Definately.
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