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Old 04-09-2007, 09:22 PM   #1036
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Originally Posted by TEM
I got a T35 but somehow I'm not inclined to put my lipos to it and discharging at 30amps.
That's what you do when you race them, but you have some 40-50A peaks added to the mixture. A 3200 should be OK with 20-30C steady load that is 64-96A continous discharge. 30A should not make them much hotter than a 5 minute race... I'm gonna get a t35 soon and I won't hesitate to put my LiPo to a test with it

I don't understand either why the manufacturers hesitate to show us discharge curves... I can;t think of anything else but probably it would show something worse than the IB4200
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Old 04-10-2007, 08:36 AM   #1037
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Cells are a lot hotter coming out of a complete 30-35amp linear discharge from the T35 than they do just off the track(I only did 19T so mod guys can tell me otherwise). There are people out there NOT recommending a complete linear discharge off IB's. The linear high current does strain the cells. Which is another contributing factor in newer dischargers being pulse high current. Its slower but the cells stay cooler. The only time I use high current linear discharge is to bleed off a pack after a run. And I got a cheap indi reactor 30 to free up my charger for that purpose. What I'd really like to see (prior to lipos of course) was nimh sub cells with good punch, high voltage, less capacity but better durability. 19T is a huge class but who manages to dump a 4200? Just waste more time discharging after a run and waste more time charging it back up! Meanwhile the life cycles are lower than anything I've seen! We can pull off 8 min TC with 4200's but its just a dumb idea for the general RC public until we get tires and motors designed for 8 mins.

Without getting too far off subject; Any brave soul out there who'd be willing to put a new 3200 or 4800 lipo on the T35 and do a linear 30/35 and give us some numbers?
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Old 04-10-2007, 10:34 AM   #1038
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4800 Orion lipo on a Tekin DIS350 at 30amps to 6v. 7.26 ave voltage.

4200IB WC cells hold well over 7.5v according to the numbers... and at 35amps.

Most lipos we tested did not like a constant discharge. Most did not do anything close to what they claim in terms of 20C.

Loads in TC mod are more like 120amps on BL! Ave discharge is about 42amps doing the math of dumping a 4200 in 6 minutes, but we never really pull 40 amps. Way more and way less gives you an average in the middle

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Old 04-10-2007, 01:09 PM   #1039
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TEM, you've got a point... anyway I will still try it on my LiPo so we will see I guess...
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Old 04-10-2007, 02:01 PM   #1040
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All hail Tekin Prez!!! Finally someone did a linear high current discharge on these bad-boys!...

So the mystery is solved! These lipos DONT like linear high current discharge. And since the numbers will look ugly, they don't give it to us! I'm thinking about an alternative method that can be used for an alternative standard (hint hint Tekin!, beat CE to making the standard machine for discharging Lipos!) Maybe a pulse discharge? Rectangular curve; 1-2 second 30amp with .25-1 second in between? Or how about a saw tooth pattern? God knows how you're gonna get an approximated equivalent avgV or IR calculations out of that! But its something to consider.

Not knocking them yet. I still haven't had enough time to do track testing. I was there one day but couldn't get the right setup after the weight difference and different power band.....
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Old 04-10-2007, 02:14 PM   #1041
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Quote:
Originally Posted by TEM
All hail Tekin Prez!!! Finally someone did a linear high current discharge on these bad-boys!...

So the mystery is solved! These lipos DONT like linear high current discharge. And since the numbers will look ugly, they don't give it to us! I'm thinking about an alternative method that can be used for an alternative standard (hint hint Tekin!, beat CE to making the standard machine for discharging Lipos!) Maybe a pulse discharge? Rectangular curve; 1-2 second 30amp with .25-1 second in between? Or how about a saw tooth pattern? God knows how you're gonna get an approximated equivalent avgV or IR calculations out of that! But its something to consider.

Not knocking them yet. I still haven't had enough time to do track testing. I was there one day but couldn't get the right setup after the weight difference and different power band.....
This is cool as long as people understand that they only need to discharge their lipo one in a while to grade them and pick out thier strong packs. Regularly discharging LiPo serves no purpose and just shortens thier life.
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Old 04-10-2007, 02:25 PM   #1042
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Quote:
Originally Posted by AdrianM
This is cool as long as people understand that they only need to discharge their lipo one in a while to grade them and pick out thier strong packs. Regularly discharging LiPo serves no purpose and just shortens thier life.
Yeah I know... The whole discharge thing was a comparison. Which now I'm thinking about it; Tekin Prez might have to redo the test! Discharging a lipo to 6 volts is not a good comparison to discharging a nimh cell down to 0.9V per cell!!! What was I thinking!.... Maybe we should look at 30 or 35amp linear discharge average voltage over the first 400 seconds? Then it's almost heads up comparison that useful cause we stop when the race is over!

Either way, he did answer the question of why Orion doesn't publish 30/35amp linear discharge data!
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Old 04-10-2007, 02:46 PM   #1043
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Quote:
Originally Posted by TEM
Either way, he did answer the question of why Orion doesn't publish 30/35amp linear discharge data!
Actually he did not, we have sent the request to Kokam and will publish it once we receive it. We do not race dischargers so we do not base our R&D for our packs on linear discharge as it is not the best test of a pack. We have the advantage of a close relationship with Kokam and access to their data which is the most accurate as they themselves make the cells at the same site.

Just yesterday we discharged a couple of packs at 30amps and brought them down to 7V to test a battery that we balanced to make sure it would stay balanced as it had been run several times out of balance creating almost 1 volt difference per cell. This did not harm the cell at all and does no purpose but to check it to make sure the balancing fixed the issue. As Adrian said there is really no need to discharge a Li-Po cell unless there is concern that there may be an issue.

We are not hiding anything nore have we ever.
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Last edited by MrBlack; 04-10-2007 at 03:12 PM.
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Old 04-10-2007, 03:08 PM   #1044
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Quote:
Originally Posted by UN4RACING
Mr. Black heres a picture of my custom lipo brushless case.
I heard of your lunch box test station.
Tell me that does not save some space.
I agree here is images of my little powerplant:

10A Power supply
Avionics LiPo charger
2 x Avionics Flight Chargers
Volt meter
2 x 4800's (over a 100 on one, over 200 on the other)
2 x 3200's
SBS balancer
2 x Avionics 3S Micro Heli/1:18 Lipo packs
3 x Avionics 2S Micro Heli/1:18 Lipo packs
1600mAh NiMH pack (left in there by mistake)
2 x packs yet to be revealed

Outside case dimension 14" x 11.5" x 5.5"
Attached Thumbnails
Platinum Lipo-bundle.jpg  
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Old 04-10-2007, 03:18 PM   #1045
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You may rise.. LOL

Just sharing data. We were curious how they would handle the standard discharge test everyone is use to and assumed these questions would come up. We agree it may not be a good test, It was just a starting point. We are exceptionally good at breaking stuff and always have to try. That is engineering. Blew a few up on purpose as well with overcharge and dead shorts. We would have done a 20c, 80amp if they had performed better on the lighter load.

http://www.kokamamerica.com/kokam_catalog.pdf

Most of the data is here except for the Orion 4800 2P which is made just for them. The 3200 is listed and they do make a 4800 1P under their own name.

Actually after reviewing the data it was 7.12v at 30 amp. Except for the Orion, all the packs we tested swelled and got hot but some had simliar numbers.. The first few test anyway. So we went to 20amps and saw 7.38. Our Dis350 is not that accurate truthfully so it could be a little better.

All of our lipos are now weak and about 75% capacity except the Orion pack which has remained pretty strong.. They have hundreds of runs on them with a 3turn BL on carpet. Some were junk right away after the tests. You get what you pay for.

If we could find a cell as good or better than the Orion we would be selling it.

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Old 04-10-2007, 03:50 PM   #1046
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Mr. Black, I apologize if you took it the wrong way. I didn't say you were trying to hide or mislead anyone. I just said that lipos don't like the high current linear discharge and the numbers will look bad that way. I also mentioned that someone out there (maybe tekin?) can develop the right tests for lipos and make it a standard we should use! It's all good....
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Old 04-10-2007, 04:22 PM   #1047
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Quote:
Originally Posted by TEM
Mr. Black, I apologize if you took it the wrong way. I didn't say you were trying to hide or mislead anyone. I just said that lipos don't like the high current linear discharge and the numbers will look bad that way. I also mentioned that someone out there (maybe tekin?) can develop the right tests for lipos and make it a standard we should use! It's all good....
I think the problem is that a 30 amp linear discharge is not really high current, and more importantly, not a realistic portrayal of what the battery endures in a car. As Tekin mentioned, you get spikes of of 120 amps in some cars. It is in these conditions where LiPo will shine. But until there is the ability for us to test them this way, we are stuck testing them to the same antiquated standard we test NiMH.

Using the 30 amp test data, we could easily argue that LiPo is not as good as NiMH and should be allowed in all racing classes, especially since they are "not as good". But we all know that this is not the case.
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Old 04-10-2007, 04:24 PM   #1048
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Quote:
Originally Posted by TEM
Mr. Black, I apologize if you took it the wrong way. I didn't say you were trying to hide or mislead anyone. I just said that lipos don't like the high current linear discharge and the numbers will look bad that way. I also mentioned that someone out there (maybe tekin?) can develop the right tests for lipos and make it a standard we should use! It's all good....
No worries I did not take offence, I just wanted to clear things up before they snowballed as this is the internet after all.

I am also still trying to find a solution for you on the TA-04 chassis. I have seen several drivers run these at the Tamiya track on a weekly basis, and this weekend I will ask around and see what they did if anything and see why the 4800 will fit and not 3200. They are within 1mm of each other and it seems odd that they are fitting so tight for you. I am very close with Tamiya and want to make sure our customers can run them in TCS as this series is very popular and a favorite of ours.
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Old 04-10-2007, 06:09 PM   #1049
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Man....excuse me for not being fully up on the reasoning but...

....why is there so much discussion about discharging packs that don't really need to be discharged? I mean it seems to be the dominate discussion around here. Did I miss something?

I've had mine since Oct '05 and only discharged it once, and that was because I accidentally turned the nob on my ICE while I was pressing it down, and moved it from charge to discharge.

Hell, I've never even balanced mine, but mine works just as well as the ones people are buying out of the case right now.

So again, sorry if I missed the point of the discussion about discharging...

...but what was the point again?
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Old 04-10-2007, 07:59 PM   #1050
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Quote:
Originally Posted by TEM
I also mentioned that someone out there (maybe tekin?) can develop the right tests for lipos and make it a standard we should use! It's all good....
This may or may not be a reliable source for LiPo discharging it is up to you to decide:
http://www.duralitebatteries.com/pdf...t%20Review.pdf
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