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Old 07-26-2014, 04:52 PM   #16
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Eric , i have to put ya on the spot .
what is the best way to test packs to find out 2 things :
1)instant current flow? (like on the start of a race, high amperage demand )
2) how long it can handle said amps ?(which im thinking would show quality of the cells)
i would think a adjustable dummy load and a volt meter.
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Old 07-26-2014, 08:23 PM   #17
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There are a lot more than just two battery manufactures. And within each manufacture you can get different "grades" of cells in your packs. Some choose the cheaper cells to make more $$ and some use the higher grade cells for better performing packs. Just all up to how much each company wants to spend on their packs.

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Can you name three?
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Old 07-26-2014, 09:01 PM   #18
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Can you name three?
http://www.alibaba.com/corporations/...-----BIZ1.html
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Old 07-26-2014, 09:32 PM   #19
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Yeah, those are companies that buy the cells and package them, not produce them.
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Old 07-26-2014, 11:56 PM   #20
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Can you name three?
Yes I could. But I'm not going to. No need for it. I know what I need to know about lipos bot from RC ans dealing with them outside if RC.

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Old 07-27-2014, 12:00 AM   #21
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Originally Posted by jlfx car audio View Post
Eric , i have to put ya on the spot .
what is the best way to test packs to find out 2 things :
1)instant current flow? (like on the start of a race, high amperage demand )
2) how long it can handle said amps ?(which im thinking would show quality of the cells)
i would think a adjustable dummy load and a volt meter.
The only way to test c rating is to destroy the pack. No other way. But you can put a data logger in a tc or any other car and watch the amp draw spikes and see that mod cars on high load will pull 70+ amps.

I've seen mod oval cars able to dump a 7000 1s pack in 3 minutes. Do that math and you'll see some serious amp draw numbers.

Numbers are irrelevant anyway. What maters is what's fast on the track first.

EA
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Old 07-27-2014, 06:28 AM   #22
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There are a lot more than just two battery manufactures. And within each manufacture you can get different "grades" of cells in your packs. Some choose the cheaper cells to make more $$ and some use the higher grade cells for better performing packs. Just all up to how much each company wants to spend on their packs.

EA
I was told that buyers go through the lipo packs and pick
out the good lower IR cells to sell as brand X.
Is this true??
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Old 07-27-2014, 07:42 AM   #23
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I was told that buyers go through the lipo packs and pick
out the good lower IR cells to sell as brand X.
Is this true??
No. The manufacture will do this and sells them as a higher grade pack. You can pay more to get these packs. Some buyers do and some don't. Some don't and say they do! I bet u can figure out who does that!

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Old 07-27-2014, 10:04 AM   #24
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Originally Posted by EAMotorsports View Post
The only way to test c rating is to destroy the pack. No other way. But you can put a data logger in a tc or any other car and watch the amp draw spikes and see that mod cars on high load will pull 70+ amps.

I've seen mod oval cars able to dump a 7000 1s pack in 3 minutes. Do that math and you'll see some serious amp draw numbers.

Numbers are irrelevant anyway. What maters is what's fast on the track first.

EA
I did, and I haven't seen more than 50A continuously (for less than five seconds).

Draw spikes are one things, continuous current is another. How long is that spike? 1/100 second? 1/1000 s? You need to quantify it somehow.

I challenge you to show us a data log from those cars that allegedly dumped a pack in 3 minutes.
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Old 07-27-2014, 04:51 PM   #25
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I did, and I haven't seen more than 50A continuously (for less than five seconds).

Draw spikes are one things, continuous current is another. How long is that spike? 1/100 second? 1/1000 s? You need to quantify it somehow.

I challenge you to show us a data log from those cars that allegedly dumped a pack in 3 minutes.
I dont have to quantify anything to anyone. If you want to know ask several of the top Oval racers in the country that did it at the Snowbirds.

I dont have to show a data log of it. I witnessed at the Snowbirds last year. Also saw several melt the bullet connectors off of the speedo wires from the current draw as well.

Anyone here thats good at math figure up what amp draw it takes to dump a 7000mah battery pack in 180 seconds.

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Old 07-27-2014, 04:58 PM   #26
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I have a chassis dyno here for Oval racing that helps tune motors. On it using 3.8V as supply voltage to the dyno during a dyno run a 13.5 Open motor will pull around 40 amps (Constant no a spike or peak) when setup properly. So go to a 3.5 motor and the amp draw ill increase drastically.

Every oval racer usually has a chassis dyno to get motors to repeat a 4 minute run on the track and tune them to run better. Most also use what they call free rev amp draw to start with. Usually its around 20 amps free rev (No load).

Just FWIW

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Old 07-27-2014, 05:14 PM   #27
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Why all the confusion guys??? Just get Thunderpower, and call it a day....ok.... Also if these oval guys were dumping 7000mah packs in three minutes, then either the packs were not really 7000mah or their setups were too power hungry, and generated too much heat....
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I dont have to quantify anything to anyone. If you want to know ask several of the top Oval racers in the country that did it at the Snowbirds.

I dont have to show a data log of it. I witnessed at the Snowbirds last year. Also saw several melt the bullet connectors off of the speedo wires from the current draw as well.

Anyone here thats good at math figure up what amp draw it takes to dump a 7000mah battery pack in 180 seconds.

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Old 07-27-2014, 05:51 PM   #28
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Why all the confusion guys??? Just get Thunderpower, and call it a day....ok.... Also if these oval guys were dumping 7000mah packs in three minutes, then either the packs were not really 7000mah or their setups were too power hungry, and generated too much heat....
In oval it's all about lasting for 4 minutes. Max current draw at the highest level the system can support. Peak RPM at the fastest lap times. Anything less and you're not racing oval and definitely not winning.

As far as buy one battery brand and call it a day, why? I know a guy who designs battery specs for Johnson controls and not into RC at all. He sends his specs out to multiple mfgs for bids. He has to. Every generation of battery that comes out is an improvement on the last. The key is to find good batteries and keep the best for racing packs. Maybe just approach Kokam with your specs and have a battery of your own.
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Old 07-27-2014, 07:13 PM   #29
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Running offroad i can agree thunderpower is probably the best to use . They can be banged around and not cared for (as much) and hardly ever give any issues with puffing or build quality . But when it comes to onroad SPEC racing their are other companies that will outpreform them if cared for properly
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Old 07-27-2014, 07:27 PM   #30
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I did, and I haven't seen more than 50A continuously (for less than five seconds).

Draw spikes are one things, continuous current is another. How long is that spike? 1/100 second? 1/1000 s? You need to quantify it somehow.

I challenge you to show us a data log from those cars that allegedly dumped a pack in 3 minutes.
For a pack perhaps not, as the wiring and connectors are frequently the weak part of the chain. But here is a 2.2Ah cell being tested at up to 50C continuous, 110 amps, for a full discharge, by a well known independent tester. Better cell capability provides better performance, higher voltage under load, even when the current is much much lower.

C rating is a very common and very useful rating method for batteries overall, has been for a long time and will continue to be. Relatively new to RC is all.

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