Power FLARM battery temperature

I am using NiMh rechargable cells in my PowerFLARM portable.
Yesterday, while charging, I noticed that the base of the case was hot
and I disconnected the unit immediately. When I opened the battery
compartment I found all cells were hot to the touch and that each was
about the same temperature.

I was more interested in preventing damage than recording the
temperature but estimate it to have being the region of 35-40 deg C.

When charging the same cells in a stand-alone charger they don't get
anything like this hot. Applied voltage was 13.8.

If you use rechargeables in your portable what peak cell temperatures
are you seeing during charging?

Andy

On Monday, March 18, 2013 10:33:49 AM UTC-4, Andy wrote:
Applied voltage was 13.8.

Surely that isn't the voltage across the (six) batteries during charge, that would be much too high.

Possibly useful info:

I use a LaCrosse charger for AA batteries, most of which are the low self discharge type, usually charge at 500 mA. The batteries will get warm at end of charge and voltage usually peaks around 1.5V just before cutoff. I don't think the voltage goes above 1.4V for more than ten minutes (but have not paid close attention). Most of the charge happens at 1.2 - 1.35 V/cell. This gives perfect results in a charger that has four batteries more or less exposed. Same cycle in a totally enclosed space might get pretty toasty.

If you are seeing more than 9V across the batteries at any time during charge, I'd really wonder about that.

T8

On Mar 18, 8:04*am, Evan Ludeman wrote:
On Monday, March 18, 2013 10:33:49 AM UTC-4, Andy wrote:
Applied voltage was 13.8.

Surely that isn't the voltage across the (six) batteries during charge, that would be much too high.

Possibly useful info:

I use a LaCrosse charger for AA batteries, most of which are the low self discharge type, usually charge at 500 mA. *The batteries will get warm at end of charge and voltage usually peaks around 1.5V just before cutoff. *I don't think the voltage goes above 1.4V for more than ten minutes (but have not paid close attention). *Most of the charge happens at 1.2 - 1.35 V/cell. *This gives perfect results in a charger that has four batteries more or less exposed. *Same cycle in a totally enclosed space might get pretty toasty.

If you are seeing more than 9V across the batteries *at any time during charge, I'd really wonder about that.

T8

Didn't measure the voltage applied to the cells,. 13.8 was the
voltage applied to the PowerFLARM Portable. Well within its specified
range.

Andy

On Mar 18, 8:19*pm, Andy wrote:

Didn't measure the voltage applied to the cells,. *13.8 was the
voltage applied to the PowerFLARM Portable. *Well within its specified
range.

I made some measurements over the weekend. With 13.8 volts applied to
the portable the highest cell temperature I saw was 62 deg C. This
was immediately after removing the battery compartment cover. When
the cells were fully charged the temperature dropped to about 35 deg
C. Highest measured voltage across all cells was 9.2V but it was not
continuously monitored.

Cells were 2000mAh Lenmar. Probably not the highest quality cells
and not new. Temperature was measured with an uncalibrated IR spot
thermometer. Ambient temperature was about 25 deg C.

Version 1.00 of the manual says the case plastic was tested to 60 deg
C and will deform at 84 deg C or lower.

Your results may be different but the caution in the manual seems
justified - "When the unit is being charged never allow it to remain
unsupervised".

Andy

On Monday, March 25, 2013 10:00:24 AM UTC-4, Andy wrote:

I made some measurements over the weekend. With 13.8 volts applied to

the portable the highest cell temperature I saw was 62 deg C. This

was immediately after removing the battery compartment cover. When

the cells were fully charged the temperature dropped to about 35 deg

C. Highest measured voltage across all cells was 9.2V but it was not

continuously monitored.



Cells were 2000mAh Lenmar. Probably not the highest quality cells

and not new. Temperature was measured with an uncalibrated IR spot

thermometer. Ambient temperature was about 25 deg C.

PF isn't getting the end of charge cutoff right. They need to fix that. My $0.02.

This may go better with better batteries (Sanyo 2500 mAH). But a fast charger must have peak charge detection and cut off and it must work reliably, else you are going to cook something.

Good luck.

T8

On Monday, March 18, 2013 9:33:49 AM UTC-5, Andy wrote:
I am using NiMh rechargable cells in my PowerFLARM portable.

Yesterday, while charging, I noticed that the base of the case was hot

and I disconnected the unit immediately. When I opened the battery

compartment I found all cells were hot to the touch and that each was

about the same temperature.



I was more interested in preventing damage than recording the

temperature but estimate it to have being the region of 35-40 deg C.



When charging the same cells in a stand-alone charger they don't get

anything like this hot. Applied voltage was 13.8.



If you use rechargeables in your portable what peak cell temperatures

are you seeing during charging?



Andy

I thought for sure that I read somewhere that you were supposed to REMOVE internal batteries from the Portable when connecting to an external power source(?) .. It may be that it was never intended to "charge" batteries at all. That might explain the high temps.

Curt - 95

On Monday, March 25, 2013 9:29:37 AM UTC-7, CLewis95 wrote:
On Monday, March 18, 2013 9:33:49 AM UTC-5, Andy wrote: I am using NiMh rechargable cells in my PowerFLARM portable. Yesterday, while charging, I noticed that the base of the case was hot and I disconnected the unit immediately. When I opened the battery compartment I found all cells were hot to the touch and that each was about the same temperature. I was more interested in preventing damage than recording the temperature but estimate it to have being the region of 35-40 deg C. When charging the same cells in a stand-alone charger they don't get anything like this hot. Applied voltage was 13.8. If you use rechargeables in your portable what peak cell temperatures are you seeing during charging? Andy I thought for sure that I read somewhere that you were supposed to REMOVE internal batteries from the Portable when connecting to an external power source(?) .. It may be that it was never intended to "charge" batteries at all. That might explain the high temps. Curt - 95

Yes if the batteries are not rechargable.

From the Manual.

Rechargeable internal Batteries
The device features an internal NiMH battery charger. When the device is turned off and electrically connected to the vehicle or aircraft battery (either via “Power” socket or power pins on the RJ45 socket), inserted batteries will be charged if the ambient temperature lies within the allowed range for charging NiMH batteries.
If non-rechargeable batteries are fitted to the device, never connect your device to an external power source (e.g. aircraft or vehicle battery)!
The internal batteries may only be charged if the device is resting on a non-flammable, dry base. When the device is being recharged, never allow it to remain unsupervised.
The integrated charging circuit will only charge batteries at an ambient temperature of up to about 40 °C (104 °F). If possible, charge your batteries in a cool, dry environment.

Richard
www.craggyaero.com

Andy I thought for sure that I read somewhere that you were supposed to REMOVE internal batteries from the Portable when connecting to an external power source(?) .. It may be that it was never intended to "charge" batteries at all. That might explain the high temps. Curt - 95


Yes if the batteries are not rechargable.

The manual is clear on this - "The battery type must be set under the settings menu. Never use disposable batteries when the battery type is set to “rechargeable”."

There is no requirement to remove non-rechargeable batteries when connected to an external power source as long as the correct battery type has been selected in the menu!

Andy

On Monday, March 25, 2013 3:23:52 PM UTC-7, Andy wrote:
The manual is clear on this - "The battery type must be set under the settings menu. Never use disposable batteries when the battery type is set to “rechargeable”." There is no requirement to remove non-rechargeable batteries when connected to an external power source as long as the correct battery type has been selected in the menu! Andy

Well it seemed clear enough from that reference but elsewhere it says this:

"The integrtated charging circuit does not know about the battery setting. It will attempt to charge any type of battery...."

One would be tempted to ask why the changing circuit doesn't know about the type of battery when the user has entered that information. How hard would it have been to disable the charger based on specified battery type? Why does the device need to know the battery type if not for charging protection?

Andy