R/C Tech Forums

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

Reply
 
Thread Tools Search this Thread
Old 01-15-2009, 02:24 PM   #1
Tech Master
 
JAM MaxAmps's Avatar
 
Join Date: Jun 2007
Location: Nine Mile Falls, WA
Posts: 1,061
Exclamation MaxAmps.com's Official Stance on pack heating and bumping....

Lipo Battery Warming Devices/”Bumping” Lipo Packs: Do not under any circumstances attempt to “heat up” your batteries or increase the voltage of a pack above 4.2V per cell using these devices or techniques. Some insidious lithium polymer retailers/distributors have suggested using these devices and techniques to increase the performance of your lithium polymer packs. THIS IS NOT SAFE AND IS LITERALLY PLAYING WITH FIRE!

Devices on the market that heat up lithium polymer batteries can increase the risk of a fire. Lithium polymer cell manufacturers suggest that 140 degrees is NOT a safe temperature for a lithium polymer cell. At 140 degrees, the pack can become unstable and very dangerous. The small increase in performance is not worth the risk of a fire. PLEASE STAY SMART AND SAFE BY NOT USING THESE PRODUCTS!

Some retailers/distributors of other brands of lithium polymer batteries have suggested that their customers and racers “bump” the voltage of their packs using settings other than the lithium polymer setting on their charger. The manufacturers of lithium polymer cells suggest a voltage range of 3V-4.2V. Increasing voltage above 4.2V per cell is not safe. You should never attempt to charge your packs beyond the voltage set for lithium polymer packs on your lithium polymer charger. Using other battery settings to “bump” the voltage beyond 4.2V per cell can cause fire and injury. The small increase in performance is not worth the risk of fire. PLEASE DO NOT USE THESE METHODS!


Best regards,

The MaxAmps.com Team
__________________
Jason
CMO
[email protected]
www.NitroKillers.com www.MaxAmps.com Caster Driver
JAM MaxAmps is offline   Reply With Quote
Old 01-15-2009, 02:45 PM   #2
Tech Champion
 
Jason Pelletier's Avatar
 
Join Date: Jul 2007
Location: New York
Posts: 8,820
Trader Rating: 33 (100%+)
Default

Quote:
Originally Posted by JAM MaxAmps View Post
Lipo Battery Warming Devices/”Bumping” Lipo Packs: Do not under any circumstances attempt to “heat up” your batteries or increase the voltage of a pack above 4.2V per cell using these devices or techniques. Some insidious lithium polymer retailers/distributors have suggested using these devices and techniques to increase the performance of your lithium polymer packs. THIS IS NOT SAFE AND IS LITERALLY PLAYING WITH FIRE!

Devices on the market that heat up lithium polymer batteries can increase the risk of a fire. Lithium polymer cell manufacturers suggest that 140 degrees is NOT a safe temperature for a lithium polymer cell. At 140 degrees, the pack can become unstable and very dangerous. The small increase in performance is not worth the risk of a fire. PLEASE STAY SMART AND SAFE BY NOT USING THESE PRODUCTS!

Some retailers/distributors of other brands of lithium polymer batteries have suggested that their customers and racers “bump” the voltage of their packs using settings other than the lithium polymer setting on their charger. The manufacturers of lithium polymer cells suggest a voltage range of 3V-4.2V. Increasing voltage above 4.2V per cell is not safe. You should never attempt to charge your packs beyond the voltage set for lithium polymer packs on your lithium polymer charger. Using other battery settings to “bump” the voltage beyond 4.2V per cell can cause fire and injury. The small increase in performance is not worth the risk of fire. PLEASE DO NOT USE THESE METHODS!


Best regards,

The MaxAmps.com Team


Yea, Their dangerous enough as it is. < maxamps
__________________
Island Raceway & Hobby
Jason Pelletier is offline   Reply With Quote
Old 01-15-2009, 03:02 PM   #3
Tech Master
 
rearviewmirror's Avatar
 
Join Date: Nov 2008
Location: Melbourne / Austin
Posts: 1,844
Trader Rating: 17 (100%+)
Send a message via AIM to rearviewmirror Send a message via Yahoo to rearviewmirror
Default

I should have warmed my batteries up some last night. There was a significant drop in performance when the temperature hit the low 40's. I wouldn't warm them to 140, but maybe 80-100 would have been nice!
__________________
ARCTIC DOG RACING (Nitro free since 2009)

"Straights are for fast cars, curves are for fast drivers...."

8ight-E / 8ight-TE / T4 / Slash
rearviewmirror is offline   Reply With Quote
Old 01-15-2009, 03:10 PM   #4
Tech Legend
 
Cain's Avatar
 
Join Date: May 2002
Location: West Fargo, North Dakota
Posts: 29,535
Trader Rating: 240 (100%+)
Default

I think Jason's comments are directed towards those who recommend REALLY heating the packs to those excessive temperatures he mentioned.

Out here when I had time I would usually put the charged pack in my coat pocket or pants pocket and keep it warm that way (we have temps in the negatives outside, so indoors in the 40's). I doubt the human body will cause it to burst into flames, but if you see someone crisped at the track, then don't try it!
__________________
Member - Red River Radio/Control Car Club
< Tekno EB48SL / SCT410.3 | Tekno EB410 x 2 | Yokomo YZ-2 DTM x 2 | LC Racing EMB-1 Buggies and Truggies >
Cain is offline   Reply With Quote
Old 01-15-2009, 03:15 PM   #5
Tech Champion
 
Jason Pelletier's Avatar
 
Join Date: Jul 2007
Location: New York
Posts: 8,820
Trader Rating: 33 (100%+)
Default

Quote:
Originally Posted by rearviewmirror View Post
There was a significant drop in performance when the temperature hit the low 40's.

Yea i have noticed this. When i get to the track after work my batterys feel like crap for the first 5 minutes.
__________________
Island Raceway & Hobby
Jason Pelletier is offline   Reply With Quote
Old 01-15-2009, 03:20 PM   #6
Tech Regular
 
Shawn Palmer's Avatar
 
Join Date: Sep 2003
Location: Speed Passion USA Support HQ
Posts: 498
Default

I know I'm technically a competitior, but I'd like to (almost) 100% agree with you.

I know Jason's been directly involved with lipo for many years as well, but I was flying Lithium Ion cells even before Lipo came to the flight industry (2001ish?). I've flown/driven only Lipo ever since (8 years now - man I'm old!).

If you start at room temp (75degF), there is actually a discharge performance increase (lower IR, higher average voltage) at 85degF, 95degF, up to around 110degF. BUT - that's about where the tangible benefits end - at 110degF. Battery IR, voltage under load, cycle life - basically everything good about a lipo is irreversably damaged at any temp above 140degF (although my good friend Linger dissagrees about the exact temp that damage starts sometimes).

Pre-heating (heaven help me for saying this publicly) actually can extend the cycle life of a pack IF and ONLY if it's being used at near full discharge capacity. Aircraft use near full capacity quite often and pre-heating has been used since it was discovered to help cold weather flyers since like 2003ish. However, 10th cars and trucks almost NEVER do.

My experienced stance is anything up to 110F is OK, but anything more absolutely does nothing to increase performance, and that 140F mark is danger danger danger!

As far as increasing the resting voltage - I totally agree with NOT doing it for the same reasons as above - it is detrimental to IR, voltage under load and cycle life. If you do it, you're cheating yourself out of hundreds of good cycles from your pack.

Where I disagree with Jason, is that there are actually ZERO real benefits! When two packs start at 8.4v and lets say 8.5v, it only takes about a millionth of a second for the discharge curves (voltage under load) to become identical. If you're racing where having .2v more for a millionth of a second really matters - then by all means turn your 400 cycle lipo into a 50 cycle fire hazard, but not at my local track please! (Adrenaline Raceway and Farmers Hobby & Raceway in Tampa if you're interested )

Readers please ignore my signature - I'm here as an informative presence, not a competitive one.
__________________
Shawn Palmer
Speed Passion USA Sales Manager
USAsupport <at> King-Golden <dot> com
www.SpeedPassion.net
www.SpeedPowerrc.com
Shawn Palmer is offline   Reply With Quote
Old 01-15-2009, 03:48 PM   #7
Tech Master
 
rearviewmirror's Avatar
 
Join Date: Nov 2008
Location: Melbourne / Austin
Posts: 1,844
Trader Rating: 17 (100%+)
Send a message via AIM to rearviewmirror Send a message via Yahoo to rearviewmirror
Default

Quote:
Originally Posted by Shawn Palmer View Post
I know I'm technically a competitior, but I'd like to (almost) 100% agree with you.

I know Jason's been directly involved with lipo for many years as well, but I was flying Lithium Ion cells even before Lipo came to the flight industry (2001ish?). I've flown/driven only Lipo ever since (8 years now - man I'm old!).

If you start at room temp (75degF), there is actually a discharge performance increase (lower IR, higher average voltage) at 85degF, 95degF, up to around 110degF. BUT - that's about where the tangible benefits end - at 110degF. Battery IR, voltage under load, cycle life - basically everything good about a lipo is irreversably damaged at any temp above 140degF (although my good friend Linger dissagrees about the exact temp that damage starts sometimes).

Pre-heating (heaven help me for saying this publicly) actually can extend the cycle life of a pack IF and ONLY if it's being used at near full discharge capacity. Aircraft use near full capacity quite often and pre-heating has been used since it was discovered to help cold weather flyers since like 2003ish. However, 10th cars and trucks almost NEVER do.

My experienced stance is anything up to 110F is OK, but anything more absolutely does nothing to increase performance, and that 140F mark is danger danger danger!

As far as increasing the resting voltage - I totally agree with NOT doing it for the same reasons as above - it is detrimental to IR, voltage under load and cycle life. If you do it, you're cheating yourself out of hundreds of good cycles from your pack.

Where I disagree with Jason, is that there are actually ZERO real benefits! When two packs start at 8.4v and lets say 8.5v, it only takes about a millionth of a second for the discharge curves (voltage under load) to become identical. If you're racing where having .2v more for a millionth of a second really matters - then by all means turn your 400 cycle lipo into a 50 cycle fire hazard, but not at my local track please! (Adrenaline Raceway and Farmers Hobby & Raceway in Tampa if you're interested )

Readers please ignore my signature - I'm here as an informative presence, not a competitive one.
^^ Good informative posting!
__________________
ARCTIC DOG RACING (Nitro free since 2009)

"Straights are for fast cars, curves are for fast drivers...."

8ight-E / 8ight-TE / T4 / Slash
rearviewmirror is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
MaxAmps.com's Official Stance on pack heating and bumping.... JAM MaxAmps Electric On-Road 33 01-17-2009 07:53 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 12:56 AM.


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