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Old 10-03-2008, 09:04 AM   #61
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Originally Posted by billjacobs View Post
The only reason people are talking about a new battery war is because the hardcore r/c racer market has more money than sense. If you make a gentleman's agreement to run a specific lipo pack (brand and model,) the "battery wars" will never even start.
Hey Bill, why don't you all make a gentlemen's agreement to run RS4 sport chassis, HPI radial tires, etc. I'm sure your particular group of racers would have a great time and be quite competitive with one another. Of course if you wanna go race at a different track or a big event, you'll be at a disadvantage. The battery war will never end, regardless of what type of cell we use because we are RACING. RACING implies pushing to go faster, learning to not only drive better, but tune your chassis, and also your power system to the nth degree.

Ya wanna run a spec class? Spec a LiPo and cute little LiPo only charger (many will only charge at 1c), for your club and get your guys on-board. But realize that the rest of the hobby isn't going to follow your lead. If they were we'd all be racing TCS or HPI challenge rules.
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Old 10-03-2008, 09:25 AM   #62
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Does any one have a simple math formula to calculate the C-rating ?
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Old 10-03-2008, 10:18 AM   #63
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Does any one have a simple math formula to calculate the C-rating ?
From one site:

What does the C rating mean?

The C rating is a measure of how long it takes a battery pack to discharge under a given load, expressed in fractions of an hour. As an example, a battery discharging at 1C would be empty in 1 hour, a 2C discharge would empty it in 1/2 an hour, and so on. For example: a 4000 Mah battery being discharged at 4000 ma, then it would be empty after an hour, and discharging at a rate of 1C.

From another:

C Rating
LiPo cells are also commonly given a C or current rating. This is the maximum average recommended discharge current for the cell. For example, the Thunder Power 1900mAh packs have a 6C rating. To determine the maximum recommended discharge rate multiply the capacity times the C rating. 1900mAh x 6C = 11,400. So the maximum recommended discharge rate would be 11,400mA or 11.4 amps. If your application has a higher amp draw, remember that LiPo cells can be wired in parallel, and with 2 cells in parallel each cell sees half the total current. With 3 cells in parallel, each cell see one third the current.
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Old 10-03-2008, 10:33 AM   #64
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C Rating
LiPo cells are also commonly given a C or current rating. This is the maximum average recommended discharge current for the cell. For example, the Thunder Power 1900mAh packs have a 6C rating. To determine the maximum recommended discharge rate multiply the capacity times the C rating. 1900mAh x 6C = 11,400. So the maximum recommended discharge rate would be 11,400mA or 11.4 amps. If your application has a higher amp draw, remember that LiPo cells can be wired in parallel, and with 2 cells in parallel each cell sees half the total current. With 3 cells in parallel, each cell see one third the current.
There is the problem with the current rating system. Every manufacturer has a different definition and method of determining "maximum average recommended discharge current". To some this means "the max average current before cell damage occurs". To others it means "the max average current before the cell puffs up making it unuseable." Still others define it as "the max average current before the cells explode." Even more disturbing is that some define it as "Brand XXX claims their cell is a 20C pack, so if we want to outcell them we need to 'rate' ours at 25C".

This subject came up a while ago, I think it was Jim from Tekin who was trying to get all of the battery manufacturers to follow a standard procedure to rate lipo packs. Nobody could agree and it went nowhere, so we have packs hitting the market with made up C ratings and nobody to call them on their BS.
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Old 10-03-2008, 12:30 PM   #65
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Originally Posted by 94eg! View Post
For a 5000mah pack, 2C = 10amps...
Well, is it advantageous to charge at 2C rather than 1C? Beside charging quicker.
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Old 10-03-2008, 12:50 PM   #66
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Well, is it advantageous to charge at 2C rather than 1C? Beside charging quicker.
IMO======no

The only thing that helps is keeping the battery warm during charging....
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Old 10-03-2008, 01:49 PM   #67
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Originally Posted by trailranger View Post
The notes say it's a Li-Ion not a Li-Poly
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Old 10-03-2008, 02:16 PM   #68
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Heard people at the IIC were charging their Lipo's at 10 amps. Is there a real advantage to this or is it just the NiMH school of thought carrying over to Lipo's? I was under the impression that 1C was enough and never over 2C.
Yes, 2c = 10 amps with a 5000 pack but from what I've seen on the track, it makes no difference charging between 5 amps and 10 amps. Battery temperature is more important.

On the C rating thing, I would rather have the C rating replaced with an actual IR rating. I think that's what we really feel between the low C and high C ratings. A cell rating standard like we have for NiMh is some thing that we'll be waiting for a long time.
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Old 10-03-2008, 02:36 PM   #69
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Thing is, im a club racer. i'll USE my equipment, but I won't ABUSE it. If you want to belive X Y and Z will make you faster do it, but I know I havn't got the $ to replace it when it goes bang when its charged at too higher amperage etc etc.

There are plenty of other ways to make yourself faster, setup, motor, tyres etc etc.

There's only a battery war if you're too weak minded to think the guy next to you has something massively overpowered to what you are using. Mentality, use what you have, not what you think you need.

If you're a big time racer at the big events, with big bux in pocket, go for it. If you're an average Joe hanging out at your local club, wise up.
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Old 10-03-2008, 02:42 PM   #70
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I have been charging mine at 12 amps on a GFX. The battery comes off the charger cooler than when it went on. When the charger starts ramping the current down, there is not enough juice being exchanged to keep the pack warm. While charging at higher than 1c may not kill the pack or substantially shorten it's life (for competitive racing), it won't enhance the performance of the pack. That will require an external heat source to get the temp up, or a massive dump load prior to charging to get heat into the pack.
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Old 10-03-2008, 02:45 PM   #71
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or you could simply take a small heating pad to the track with you and store them in there keeping them warm before you go out and race.
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Old 10-03-2008, 03:22 PM   #72
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Originally Posted by JamesArluck View Post
There is the problem with the current rating system. Every manufacturer has a different definition and method of determining "maximum average recommended discharge current". To some this means "the max average current before cell damage occurs". To others it means "the max average current before the cell puffs up making it unuseable." Still others define it as "the max average current before the cells explode." Even more disturbing is that some define it as "Brand XXX claims their cell is a 20C pack, so if we want to outcell them we need to 'rate' ours at 25C".

This subject came up a while ago, I think it was Jim from Tekin who was trying to get all of the battery manufacturers to follow a standard procedure to rate lipo packs. Nobody could agree and it went nowhere, so we have packs hitting the market with made up C ratings and nobody to call them on their BS.
I agree, I see these C Ratings as the maximum before catastrophes like fire and like puffing. The manufacturers need to post a mean value above 1C and below XC where the batteries can supply a peak efficiency C rating relative to the current draw of your car. What most people aren't aware of is, is what the maximum current draw for their cars are. I personally want a pack where the C Value is above my maximum peak current draw. That should be easy if everyone would standardize their numbers.

Anyone ever bench their car for current draw to see what its normal operating requirements are Vs. a one time short duration peak load?
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Old 10-03-2008, 03:51 PM   #73
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Originally Posted by JamesArluck View Post
There is the problem with the current rating system. Every manufacturer has a different definition and method of determining "maximum average recommended discharge current". To some this means "the max average current before cell damage occurs". To others it means "the max average current before the cell puffs up making it unuseable." Still others define it as "the max average current before the cells explode." Even more disturbing is that some define it as "Brand XXX claims their cell is a 20C pack, so if we want to outcell them we need to 'rate' ours at 25C".

This subject came up a while ago, I think it was Jim from Tekin who was trying to get all of the battery manufacturers to follow a standard procedure to rate lipo packs. Nobody could agree and it went nowhere, so we have packs hitting the market with made up C ratings and nobody to call them on their BS.

good post man maybe these guys will do a search on c rating read the post from repitable Like Jim from Tekin Danny from SMC and get the hint C ratings are meaningless a 28 c smc isn't the same as another brands 28c
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Old 10-03-2008, 04:10 PM   #74
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Originally Posted by timmay70 View Post
I have been charging mine at 12 amps on a GFX. The battery comes off the charger cooler than when it went on. When the charger starts ramping the current down, there is not enough juice being exchanged to keep the pack warm. While charging at higher than 1c may not kill the pack or substantially shorten it's life (for competitive racing), it won't enhance the performance of the pack. That will require an external heat source to get the temp up, or a massive dump load prior to charging to get heat into the pack.
Lipos actually cool down as they charge...that's why some are trying to warm them up with other means before racing since Lipos work even better when warmer, allegedly. Danny from SMC has posted on this on the SMC thread.
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Old 10-03-2008, 04:38 PM   #75
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warming them up is a flyer trick that's been carried over to the car world.

they did it to make sure they had the battery's maximum power available. now it looks like it's being used to get an edge in racing.
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