R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Electric On-Road

Reply
 
Thread Tools Search this Thread
Old 03-13-2007, 01:09 PM   #916
Tech Adept
 
ljohnson's Avatar
 
Join Date: Feb 2004
Location: Delta BC, Canada
Posts: 183
Default

Quote:
Originally Posted by linger
Here's a plot of the Kokam 740mAh 20C cell. There are 12 cells on this plot. ...
Very cool. What are the units on the y axis?
ljohnson is offline   Reply With Quote
Old 03-13-2007, 01:40 PM   #917
Tech Champion
 
Join Date: Oct 2005
Location: Cincinnati, OH
Posts: 5,360
Trader Rating: 38 (100%+)
Default

Quote:
Originally Posted by linger
Here's a plot of the Kokam 740mAh 20C cell. There are 12 cells on this plot. 6 are charged at 2C, and 6 charged at 1C. Out of each group of 6, 2 are pulse discharged at 16-20C, 25-30C, and 34-41C.

All the cells charged at 2C dropped like a rock regardless of discharge rate. All the cells charged at 1C held up really well regardless of discharge rate - losing less than 5% capacity at 450 cycles. These are full charge/discharge cycles with a cutoff at 2.8V/cell.

Testing of cells 2000mAh and below had similar results. Hopefully, Cliff will be able to share results of 2C charging of cells greater than 2000mAh.
Great Info! Im surprised it is such a big cutoff. I guess it would be wiser to invest in another charger and battery pack then try to speed up the charging.
or8ital is offline   Reply With Quote
Old 03-13-2007, 08:57 PM   #918
Tech Master
 
sim600's Avatar
 
Join Date: Dec 2003
Posts: 1,624
Trader Rating: 15 (100%+)
Send a message via ICQ to sim600
Default

It also looks like a big difference between the top and bottom cells when new - 60 vs 40 (is that Y axis runtime?)
__________________
ModRC.com
sim600 is offline   Reply With Quote
Old 03-13-2007, 09:16 PM   #919
Tech Master
 
sim600's Avatar
 
Join Date: Dec 2003
Posts: 1,624
Trader Rating: 15 (100%+)
Send a message via ICQ to sim600
Default

MR JOLLY,
I was wrong about the amps and volts. I paid more attention to my setup (my charger has a built-in balancer but is sort of wired the same way as yours, needing 3 wires to balance and 2 to charge), and the amps are constant at near the amps you set it at and it only starts dropping off only when the battery is at 4.2volts. I guess this is what they mean by constant current, constant voltage. The charger tries to maintain a constant current unless the voltage is reached, in which case, it charges at constant voltage (and dropping current). Of course, this doesnt solve your problem with the open circuit error. Maybe a tab in your battery is broken or melted or maybe something came out of your connector.

This brings up another question. Would we be able to get more life out of our batteries if we charge it to 4.1 volts at 1C (Lithium Ion mode charges to this voltage) and then charge the remainder at under 1C, say 0.5 C?
__________________
ModRC.com
sim600 is offline   Reply With Quote
Old 03-13-2007, 09:48 PM   #920
Tech Adept
 
Join Date: Sep 2004
Posts: 179
Default

Quote:
Originally Posted by sim600
This brings up another question. Would we be able to get more life out of our batteries if we charge it to 4.1 volts at 1C (Lithium Ion mode charges to this voltage) and then charge the remainder at under 1C, say 0.5 C?
I believe that is the way some balancing chargers work. They charge the cells to about 4.1V and then slow down....varying the current to the cells that are lower...until all cells reach 4.2V.
Disaster is offline   Reply With Quote
Old 03-13-2007, 10:00 PM   #921
Tech Adept
 
Join Date: Sep 2004
Posts: 179
Default

Quote:
Originally Posted by Iceracer
Bad news. Tower's price on the Peak 3200's has jumped back up to $80.00.
Now up to $90!!! the Orion is cheaper at $85.

I've seen this kind of thing at Tower before. They seem to have some sort of computer model that plays with pricing. If sales are down, and inventory up, I think it might lower the price to see if this affects a change. Then if the sales increase, and the inventory decreases, it reacts with a price hike. All the people reading this thread and jumping on the deal drove their sales up and their inventory down...BINGO. New higher price.

I've been bitten by this where I saw a good price, and stored it in my wish list. When I go back to buy it, it is way up in price. I've also had the case where I buy one item to try it. When I decide it is good, I go back and the price has been hiked up. Sometimes it almost seems as if my one purchase caused the computer pricing model to react.

You can take advantage of this by trolling Tower for parts. For example they had 4 similar Duratrax Micro Street bodies....only difference was the color. One week the yellow body was half the price of the others. A few months later it was back up in price but the white body was 1/3rd the price of the others. I doubt the more popular blue body will ever see a sale.

When things quiet down the price may go down again...but I've tried to wait out other parts that have never gone back down. SIGH!
Disaster is offline   Reply With Quote
Old 03-13-2007, 11:30 PM   #922
Tech Master
 
linger's Avatar
 
Join Date: Aug 2001
Location: Retired
Posts: 1,132
Trader Rating: 1 (100%+)
Default

Quote:
Originally Posted by sim600
It also looks like a big difference between the top and bottom cells when new - 60 vs 40 (is that Y axis runtime?)
Actually, the difference is due to the different discharge rates - see my previous post. The Kokam cells are extremely closely toleranced...probably the closest I tested out of 10+ manufacturers.
The Y axis is analagous to capacity. The test was for a non-RC application to simulate the number of high discharge "pulses" before my device drains the battery. The highest discharge rate hits the voltage cutoff earlier - so less "pulses" per charge.
__________________
I used to be a spitter, now I'm a swallower. I graduated.
linger is offline   Reply With Quote
Old 03-13-2007, 11:57 PM   #923
Tech Regular
 
Join Date: Jun 2002
Location: Melbourne, Australia
Posts: 449
Default

I was lucky enough to still have a few in my shopping cart at the cheaper price after they raised the price A few days later I submitted the order and they appeared to have honored the deal since they have shipped it.

Quote:
Originally Posted by Disaster
Now up to $90!!! the Orion is cheaper at $85.

I've seen this kind of thing at Tower before. They seem to have some sort of computer model that plays with pricing. If sales are down, and inventory up, I think it might lower the price to see if this affects a change. Then if the sales increase, and the inventory decreases, it reacts with a price hike. All the people reading this thread and jumping on the deal drove their sales up and their inventory down...BINGO. New higher price.

I've been bitten by this where I saw a good price, and stored it in my wish list. When I go back to buy it, it is way up in price. I've also had the case where I buy one item to try it. When I decide it is good, I go back and the price has been hiked up. Sometimes it almost seems as if my one purchase caused the computer pricing model to react.

You can take advantage of this by trolling Tower for parts. For example they had 4 similar Duratrax Micro Street bodies....only difference was the color. One week the yellow body was half the price of the others. A few months later it was back up in price but the white body was 1/3rd the price of the others. I doubt the more popular blue body will ever see a sale.

When things quiet down the price may go down again...but I've tried to wait out other parts that have never gone back down. SIGH!
__________________
Awesomatix A700L (building) | VBC Wildfire D07 (building) |416WE/X Smokem | Hobbywing 120A v2.1 | Sanwa M11x
itchynads is offline   Reply With Quote
Old 03-14-2007, 12:08 AM   #924
Tech Master
 
sim600's Avatar
 
Join Date: Dec 2003
Posts: 1,624
Trader Rating: 15 (100%+)
Send a message via ICQ to sim600
Default

linger,
Thanks. I understand now. That's a relief. Had me a bit worried about dealing with LiPo matchers. Haha.
__________________
ModRC.com
sim600 is offline   Reply With Quote
Old 03-14-2007, 07:49 AM   #925
Tech Adept
 
Rainey's Avatar
 
Join Date: Nov 2004
Location: Brandon, Ms
Posts: 86
Default

Quote:
Originally Posted by itchynads
I was lucky enough to still have a few in my shopping cart at the cheaper price after they raised the price A few days later I submitted the order and they appeared to have honored the deal since they have shipped it.

I did the same thing. Was going to order them Friday bit got busy and forgot. Saw the post about the price going up so Monday when i got to work, i still had 2 saved in my shopping cart at the cheaper price. Thought i would take a chance and send the order to see if i would gewt them at the "old" price. Looks like it worked because they have been shipped with the invoice showing the reduced price. bought 2 with shipping (and $20 off) for about 59.95 per pack!
__________________
www.rcracingxtreme.com
racers running races for racers !
Rainey is offline   Reply With Quote
Old 03-14-2007, 10:50 AM   #926
Tech Addict
 
Tsquare's Avatar
 
Join Date: Sep 2004
Location: San Diego
Posts: 618
Trader Rating: 4 (100%+)
Default

Quote:
Originally Posted by linger
Here's a plot of the Kokam 740mAh 20C cell. There are 12 cells on this plot. 6 are charged at 2C, and 6 charged at 1C. Out of each group of 6, 2 are pulse discharged at 16-20C, 25-30C, and 34-41C.

All the cells charged at 2C dropped like a rock regardless of discharge rate. All the cells charged at 1C held up really well regardless of discharge rate - losing less than 5% capacity at 450 cycles. These are full charge/discharge cycles with a cutoff at 2.8V/cell.

Testing of cells 2000mAh and below had similar results. Hopefully, Cliff will be able to share results of 2C charging of cells greater than 2000mAh.
Thank you for taking the time to put this information together. You saved me alot of money
Tsquare is offline   Reply With Quote
Old 03-14-2007, 08:02 PM   #927
Tech Adept
 
Join Date: Nov 2006
Posts: 154
Default

I have a 4800 lipo. I'm happy with it . However I don't know which way to go.

#1
race 5 min
charge 20 min
race 5 min
charge 20 min
race 5 min
charge 20 min
...
...
...

#2
race 5min
race 5min
race 5min
charrrrrrrrrrrrrrrrrrrge 1 hour
race 5min
race 5min
race 5min
charrrrrrrrrrrrrrrrrrrge 1 hour
...
...
...
xtaiji is offline   Reply With Quote
Old 03-15-2007, 12:05 AM   #928
Tech Elite
 
Join Date: Sep 2001
Posts: 3,117
Trader Rating: 69 (100%+)
Default

when i ran stock, i did somewhat similar to the 2nd option ...

fully charged lipo
5 min 1st qualy
5 min 2nd qualy
charge
5 min 3rd qualy
5 min 1st main
charge
5 min 2nd main
5 min 3rd main
fully charge, store for next race

when i ran mod, i did the 1st option

fully charged lipo
5 min 1st qualy
charge
... and so on

ive read from this and the orion platinum thread that it doesnt matter if you charge it whenever during the day, punch remains the same most of the time, i charge it right after using so i am sure that it is always ready to run at least 5 minutes in stock or mod
marvi is offline   Reply With Quote
Old 03-15-2007, 03:09 AM   #929
Tech Adept
 
Join Date: Nov 2006
Posts: 154
Default

Quote:
Originally Posted by marvi
when i ran stock, i did somewhat similar to the 2nd option ...

fully charged lipo
5 min 1st qualy
5 min 2nd qualy
charge
5 min 3rd qualy
5 min 1st main
charge
5 min 2nd main
5 min 3rd main
fully charge, store for next race

when i ran mod, i did the 1st option

fully charged lipo
5 min 1st qualy
charge
... and so on

ive read from this and the orion platinum thread that it doesnt matter if you charge it whenever during the day, punch remains the same most of the time, i charge it right after using so i am sure that it is always ready to run at least 5 minutes in stock or mod
Thank you. I'll read that.
xtaiji is offline   Reply With Quote
Old 03-15-2007, 05:09 AM   #930
Tech Initiate
 
IlikeRCstuff's Avatar
 
Join Date: Mar 2007
Posts: 27
Default

If fully charged, how many mAh are you putting back in after a 5 min run with a novak 13.5?
IlikeRCstuff is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
NIP Team Orion 3200Mah Lipo Race Pack limbohz R/C Items: For Sale/Trade 0 05-30-2008 10:36 AM
Peak 3200mah carbon spec lipo aus jd 2703 Australia For Sale/Trade 8 04-23-2008 09:12 PM
Team Orion Carbon Edition 3200mAh LiPo squearl R/C Items: For Sale/Trade 7 03-11-2008 06:35 AM
Team Orion Carbon Edition 3200mAh lipo batteries dido41 R/C Items: Wanted to Buy 3 07-26-2007 04:10 PM
2 Team Orion Carbon Edition 3200mAh LiPo Batteries CCristo R/C Items: For Sale/Trade 1 05-04-2007 11:48 AM



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 12:18 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net