NiMH Charger Without Temp sensor

[ColorMaker]

We have a battery back assembled with 10 2700mah cells in series for 12 votls. We designed the back with temp sensor. Supplier of charger 12 votls .9a has discontinued the charger with sensor input and now offer only output for charging. How critical is this temperature monitoring ?

JM

 

[Turbo Guy]

Is the battery buried in a device or casn the cells been seen / felt during charging?

A 0.9A charge rate is only a C/3 charge rate for those 2700 mAh (2.7AH) cells and most would agree that is on the low side. Why not a real charger that can charge them at 2 to 3 amps?
There are many hobby chargers which can charge at 5 amps. or more that have temp. probes as an option. I never use charger connected temp. probes myself but use a digital theromter instead ( indoor / out type with wired probe). I also use a IR temp. gun to measure indivual cells in a battery pack.

How critical is this temperature monitoring ?

High temps. 125 plus will shorten the cells life. They casn stand 140 or so a few time but their life will be shortened.

Size / quality of cells matters also. Would these be consumer grade AAs / C , D, SubC , 4/5 As or what?

 

[ColorMaker]

Buried, This is a desktop charger we sell with our products so we need to stay witin the $50 range. We were getting the charger with sensor but the manufacturer sent the last shipment without the sensor so I wanted to know if it would be safe to use. The charger can be set for .9 or 1.8 charging current. Are both safe without temperature monitoring ?

JM

Is the battery buried in a device or casn the cells been seen / felt during charging?

A 0.9A charge rate is only a C/3 charge rate for those 2700 mAh (2.7AH) cells and most would agree that is on the low side. Why not a real charger that can charge them at 2 to 3 amps?
There are many hobby chargers which can charge at 5 amps. or more that have temp. probes as an option. I never use charger connected temp. probes myself but use a digital theromter instead ( indoor / out type with wired probe). I also use a IR temp. gun to measure indivual cells in a battery pack.



High temps. 125 plus will shorten the cells life. They casn stand 140 or so a few time but their life will be shortened.

 

[Turbo Guy]

Not enough imformation.


Are these smart ( peak detection) chargers?
Dumb chargers that charge at a somewhat constant rate , tapered rate, timer equiped,etc?

Did the temp. probe ones ever or routinely trip the high temp. limit and so what was the high limit?

What type of cells are they? I read NiMH 2700 mAh but that could be AAs, SubC, C, D or several other sizes.

Are they high quality cells such as Sanyos , GP ,Intellect , etc. or elcheapo purchased from lowest bidder?

How critical is the application and what service life is expected?

Sorry but there are so many variables here.

 

[ColorMaker]

2700 PowerEx AA
They are peak detector chargers from Tenergy, I beleive dv. To my knowledge Temperture trip has not been used its only a backup. The link below is the charger we received but does not include temp s.

http://www.tenergybattery.com/index...facturer_id=0&option=com_virtuemart&Itemid=27

Not enough imformation.


Are these smart ( peak detection) chargers?
Dumb chargers that charge at a somewhat constant rate , tapered rate, timer equiped,etc?

Did the temp. probe ones ever or routinely trip the high temp. limit and so what was the high limit?

What type of cells are they? I read NiMH 2700 mAh but that could be AAs, SubC, C, D or several other sizes.

Are they high quality cells such as Sanyos , GP ,Intellect , etc. or elcheapo purchased from lowest bidder?

How critical is the application and what service life is expected?

Sorry but there are so many variables here.

 

[Turbo Guy]

Specs. say that 1.4A rate should work just fine. In that this charger has performed well in the past and the temp. sensor was not apparently needed, with luck the currently vesion will provide the same level of service.

My past experience with Tenergy products has ranged from very good to very poor. As an indivual I have first hand experience with a rather small sampling so my results may or may not be typical.

 

[mpf]

My first experience with "Smart Charger:with automatic voltage detection" resulted in 6 AA NiMH batteries getting too hot told and leaking their insides out.
The problem is the voltage detection will not work if the batteries are already fully charged or nearly so. I charged my torch, used it for a few minutes then put it back on to charge again, and went away. 30mins later the charge was still charging but the batteries were toast.

Ever since then I have only used temperature controlled charging circuits. The rate of rise of temperature will ALWAYS turn off the charging even if charging a fully charged battery. The over temp. is a back up.

IMHO if you are sending this out to customers you need a temperature controlled charger.

matthew