Chargers for batteries with built-in thermistors

leak · Apr 21, 2012, 10:26 AM

I'm wondering why JST-XH3 chargers for 3.7V batteries with a thermistor are so hard to find.

I just read about how recharging LiPo batteries should never be left unattended. So I figure another way to go is to use a thermistor controlled battery charger that will interrupt the recharge if the battery would get too hot and keep it within safe limits.

PGR · Apr 21, 2012, 12:30 PM

The biggest potential problem with this idea is LiPo cells can suffer from a phenomenon known as thermal runaway and once the process begins you typically can't stop it by interrupting the charge cycle.

In other words, it's usually not enough to simply stop the charge cycle when a LiPo pack begins to heat up.

Pete

gulio · Apr 22, 2012, 08:52 AM

Yes, the cell can be far outside the limits AND be cool as a cucumber. That's cool.

PGR · Apr 22, 2012, 10:42 AM

It's always been my understanding that there should never be any heat generated by a pack during a charge cycle, and that's been my personal observation since 2004 when I began using LiPos.

But I need to qualify that a little: I typically charge at 1 or 2C and I can only recall charging at 3C a couple of times when I had some friends waiting on me for a formation flight. Consequently, I don't really know from personal experience whether packs will warm up at the maximum charge rates some packs are rated for and I have no desire whatsoever to find out.

Pete

gulio · Apr 22, 2012, 11:17 AM

My experience is that they will not warm much even at max rates. Maybe 1-2 degrees , and if one charges after use then they'll even cool down some. The newer max rates of 5-12C don't even warm much over a couple degrees. When multiplying the max rates by 2-5 times heat is generated similar to the heat generated by discharging at those same rates. I have limited experience charging at the discharge rates and it seems that similar temp increases happen whether discharging OR charging. It does kinda make sense that that would hold true.

I think a good point is that cell temp is a terrible predictor of charge status without a bunch of other info.

Apr 21, 2012, 10:26 AM	#1
leak Registered User Joined Apr 2012 1 Posts	Chargers for batteries with built-in thermistors I'm wondering why JST-XH3 chargers for 3.7V batteries with a thermistor are so hard to find. I just read about how recharging LiPo batteries should never be left unattended. So I figure another way to go is to use a thermistor controlled battery charger that will interrupt the recharge if the battery would get too hot and keep it within safe limits.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
New Product G.T.POWER charger built-in lithium battery internal resistance testing system	GTPOWERlisa	Batteries and Chargers	4	Oct 07, 2012 11:46 AM
Discussion wall charger battery for the radian in the uk	alefveld	Electric Sailplanes	0	Mar 08, 2012 07:44 AM
Question what charger parameters for AA batteries with orion advantage charger	le varan	Batteries and Chargers	4	Dec 17, 2011 01:27 PM
Question Looking for a AC/DC lipo charger with built in AC adapter......................	mtdoramike	Batteries and Chargers	6	Jun 02, 2009 08:16 PM
Discussion The Ultimate LiPo Charger For EDF (with BUILT-IN ballancer)	bmaaa	Electric Ducted Fan Jet Talk	3	Mar 06, 2006 11:46 PM

RCG Sites

About RCG

Features

Tools

Media

Topics

Apr 21, 2012, 12:30 PM	#2
PGR Low AltiDude United States, CA, Costa Mesa Joined Jun 2004 7,547 Posts	The biggest potential problem with this idea is LiPo cells can suffer from a phenomenon known as thermal runaway and once the process begins you typically can't stop it by interrupting the charge cycle. In other words, it's usually not enough to simply stop the charge cycle when a LiPo pack begins to heat up. Pete

Apr 22, 2012, 08:52 AM	#3
gulio That's a funny word NE Ohio Joined Apr 2003 3,662 Posts	Yes, the cell can be far outside the limits AND be cool as a cucumber. That's cool.

Apr 22, 2012, 10:42 AM	#4
PGR Low AltiDude United States, CA, Costa Mesa Joined Jun 2004 7,547 Posts	It's always been my understanding that there should *never* be any heat generated by a pack during a charge cycle, and that's been my personal observation since 2004 when I began using LiPos. But I need to qualify that a little: I typically charge at 1 or 2C and I can only recall charging at 3C a couple of times when I had some friends waiting on me for a formation flight. Consequently, I don't really know from personal experience whether packs will warm up at the maximum charge rates some packs are rated for and I have no desire whatsoever to find out. Pete

Apr 22, 2012, 11:17 AM	#5
gulio That's a funny word NE Ohio Joined Apr 2003 3,662 Posts	My experience is that they will not warm much even at max rates. Maybe 1-2 degrees , and if one charges after use then they'll even cool down some. The newer max rates of 5-12C don't even warm much over a couple degrees. When multiplying the max rates by 2-5 times heat is generated similar to the heat generated by discharging at those same rates. I have limited experience charging at the discharge rates and it seems that similar temp increases happen whether discharging OR charging. It does kinda make sense that that would hold true. I think a good point is that cell temp is a terrible predictor of charge status without a bunch of other info.