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Old 04-05-2013, 10:15 PM   #91
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Originally Posted by EAMotorsports View Post

If I need to get right back out on the track for practice I dont wait...Just recharge and go. Same for heat races. If I am not up for a few hours I'll just let the pack sit, then discharge and recharge before I am up again.

EA
great info, thank you.

So basically if you have time, you discharge the remaining capacity and immediately recharge to get it fully charged right before your next run?
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Old 04-05-2013, 10:59 PM   #92
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No need to discharge ! Just a slight balanced charge to equalize the cells before you let the pack sit.... Avoid leaving the pack unequalized for too long after a run. It should get an equalizing charge right after your run..... Discharge is just a psychological remnant of the old Nimh days, with the belief that it will boost Performance by recharging the full capacity of the pack at the 40amp rate, rather than recharging some of the capacity at 40amps... All it really does is spike the risk of violent fires more than anything else.. Charge from 7 to 12 amps and you should be fine... I usually charge my 3300 packs at 6amps and easily keep up down the straight with those that charge at higher amps, and I run a (weaker) novak 13.5t motor... You go figure.... I guess their mentality helps sell lots of new chargers and power supplies....
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Old 04-06-2013, 08:10 AM   #93
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Originally Posted by bertrandsv87 View Post
No need to discharge ! Just a slight balanced charge to equalize the cells before you let the pack sit.... Avoid leaving the pack unequalized for too long after a run. It should get an equalizing charge right after your run..... Discharge is just a psychological remnant of the old Nimh days, with the belief that it will boost Performance by recharging the full capacity of the pack at the 40amp rate, rather than recharging some of the capacity at 40amps... All it really does is spike the risk of violent fires more than anything else.. Charge from 7 to 12 amps and you should be fine... I usually charge my 3300 packs at 6amps and easily keep up down the straight with those that charge at higher amps, and I run a (weaker) novak 13.5t motor... You go figure.... I guess their mentality helps sell lots of new chargers and power supplies....
Eric discharges his pack to flex it and create heat wile charging . since he charges at 40a and only had to put 2100+-mah back in pack it wouldnt have and heat to it when done charging.
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Old 04-06-2013, 09:04 AM   #94
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Nope. I have a power supply thats from an HP Server I got on ebay for 13.00 shipped. It puts out 47 amps and is super light and small. Dont buy into the progressive RC power supplies they try to tell you you need.



If I need to get right back out on the track for practice I dont wait...Just recharge and go. Same for heat races. If I am not up for a few hours I'll just let the pack sit, then discharge and recharge before I am up again.

EA
We have two HP server PS converted to 24V but never brave enough to go 40amps into these Lipos which are rated for 5C charging but did one just for test a 30amps and the PowerLab did confirm a much lower IR at higher charging currents.

What voltage did you discharge it down to before recharging them back up?

It would be interesting to find out if there is a performance difference if you discharge after each run or just throw them back on the charger at 40amps...
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Old 04-06-2013, 09:43 AM   #95
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If you discharge at a high rate, it will warm the cells internally. Charging at a high rate will also warm up the cells internally. If you do both, you have warming on the discharge then warming on the charge, which will now take a little longer. Time it all to finish just before your next run and it makes sense that you would have some pretty punchy batteries. Just need to be cool enough to pass tech and not spontaneously combust.

It is racing. People will do what they can within the rules to get an edge. Especially in stock racing.

I don't push the limits most of the time. I'm too safe and far too lazy for that. I might charge at 12-20A but usually well before my next qual and just a top up from the last run, so most of time my batteries are stone cold and well under 8.4V by the time the horn sounds. I mainly just race to have fun and don't really push the limits. Frequent coffee and smoke breaks and shooting the shh with everyone is what makes it so enjoyable for me. When I get in a tight race though, my inner competitor comes out.

I have no problem if someone else wants to push the limits of the rules, as long as they stay within them and keep a close eye on their stuff and take precautions when doing the more risky things. It's racing.

I've only been racing for 3 years now, but raced quite a bit in that short time. I've witnessed 2 lipo fires, ever. Both were in cars, on the track. If more people start messing around with crazy charge cycles though, it will probably become more likely that I'll witness a pit fire in the future. Hopefully anyone getting too experimenty will take extra precautions. Lipo bag in an ammo box in a paint booth in a bunker.
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Old 04-06-2013, 02:51 PM   #96
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I don't if Roar still abides by their 1C charging rule of old or expanded it to 2C or 3C , but I am sure that it is impossible to tech.... I guess temping the packs is an OK way to sort of equalize the racer's battery output, and I will live in peace with others that crank the amp charge rate to get an edge , but it's twice as fun when I beat them anyway though....
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Old 04-06-2013, 02:56 PM   #97
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By the way, nobody charged their lipos at higher than 40amps yet ???
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Old 04-06-2013, 06:53 PM   #98
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By the way, nobody charged their lipos at higher than 40amps yet ???
If ICharger or PowerLab releases a more powerful charger, I'm sure some racers will.
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Old 04-06-2013, 08:10 PM   #99
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So......believe the guy who's won Snowbirds, made the main at the Nats, has tested more batteries than any of us will own in a lifetime,.........or believe the guy who's won?
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Old 04-06-2013, 08:35 PM   #100
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I believe some racers will always have that edge with their batteries, but the risk of being disqualified and causing fires are not justified to me.... It is good to know how to make batteries more punchy, but it's not the spirit of Rc Spec Racing... I will concede that edge anytime and always race for FUN not GLORY... ROAR will get better at eliminating that edge and I am sure they will come with power Supply rules and charge rate rules if racers endanger other's lives by charging at an excessively high rate for their 15 Minutes of fame....
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Old 04-06-2013, 11:23 PM   #101
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Originally Posted by bertrandsv87 View Post
I believe some racers will always have that edge with their batteries, but the risk of being disqualified and causing fires are not justified to me.... It is good to know how to make batteries more punchy, but it's not the spirit of Rc Spec Racing... I will concede that edge anytime and always race for FUN not GLORY... ROAR will get better at eliminating that edge and I am sure they will come with power Supply rules and charge rate rules if racers endanger other's lives by charging at an excessively high rate for their 15 Minutes of fame....
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NiMh you can charge them at 10% higher than rated. LiPos, good chargers is already preset for 1s,2s,3s,and 4s. Charge to 4.2v per cell @ Mh its rated cuz of Fire or explosion of cells. LiPos are better, cuz they can be charged anytime. Good charger turns itself off. They don't need to be top off like NiMh. Kudos to manufacture of charger to keep this hobby safe. We don't know with the Covered Lipos, if cells are blouted out. and temp. Good charger we cant see temp while charging. We see temp after the run. we let then cool down till we charge them.
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Old 04-07-2013, 04:39 AM   #102
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If we were to predict the upper limit of the amp charge rates, assuming that the largest lipo pack to fit a touring Car while maintaining a raceable weight is 7700mah, then you would need a power Supply/charger system to crank more than 92.4amps.... 100+ amps charging systems will be the next thread....lol.... Not too long ago we were charging Nimh packs at 7amps. 40 amps is almost six times the charge rate of the nimh cells. Hopefully the next battery chemistry won't follow that trend, and have us shooting for 240amps...lol...
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Old 04-07-2013, 05:05 AM   #103
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I think we're reaching the upper limit of practicality. We will be needing 36v or 48v systems in a few years.
How many of these 24v 1400w systems will your race facility's 15A electric services going to support? Voltage will have to go up to keep the current down.
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Old 04-07-2013, 06:04 AM   #104
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I think we're reaching the upper limit of practicality. We will be needing 36v or 48v systems in a few years.
How many of these 24v 1400w systems will your race facility's 15A electric services going to support? Voltage will have to go up to keep the current down.

Track will have to increase the size of there circuit breakers.
Lipos batteries are getting better all the time.

20 amp charging is good to get the benefits of lower IR but
if time is a issue then 40 amps are fine.

If the lipo sits for a time and gets cold then discharge and charge at 20 or more.

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Old 04-07-2013, 09:11 AM   #105
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This was posted on Hobbytalk:

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There is more to this charger than just its ability to charge at high amp rates. How it charges a pack is as important as its high amp rate capabilities. Similar to the GM VIS charger in the NiCad days, the way the iCharger charges a pack increases the Lipo's performance, simply put.

For instance, I have noticed a difference even when comparing the iCharger to my GFX and LRP chargers. If I charge the same pack on the three different chargers at the same amp rate to 4.22, it cycles about the same on the GFX and the LRP: 1.6 IR, 4V for 90-95 seconds, and 3.82V @ 240. When I charge it on the iCharger, the IR drops to 1.4-1.5, 4V for 100-105, and 3.83-3.84 @ 240.

I certainly don't know howit accomplishes this, (and I would be lying if I said I even care...lol) but more importantly I do know what it does and have witnessed the performance difference first hand. This is what convinced me to not just buy a 4010 but to sell them as we'll.

Hope this helps - :thumbsup:
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