Hot batteries!

[nightbreed]

I ask you all, when u charge your 7.2V sticks with those chargers that handle many different types of batts, does your batt become very hot? I don't mean warm. HOT. Can pick up but feels like a glass cup of hot water left to cool for a few minutes.

My charger is a Speed EX15. I discharge the batt at 20A, then it charges at abt 3.5A. Takes something like 40 minutes to charge a 3300 batt. My 1500 batt is not so hot, just warm.

The charger has readouts for Voltage, Capacity and ....er...is it Ampere? The Capacity reading for a charged 3300 batt is 338x for one and 35xx for another. Both of them have Voltage readings of 8.xx after charging. I don't know if these means anything....

Tried charging a 12V batt, but donno whether it worked. Haven't set up my starter box to try yet.

Also, when I connect the 7.2V batt to the croc clips, should I connect them 1st BEFORE turning on power or After? I tried connecting after...got sparks. I hate the fact that the leads are exposed like that. My daughter likes to touch my RC stuff.....

Thank you for reading!

[nic]

If you charge it at 1C... it bound to get very hot if the charger doesn't know how to reduce the current as the batt reaches its peak capacity.

For Nihm... heat will damage the battery... so if you have been heating it to that extend... the battery capacity will drop... sometime very drastically.

[nightbreed]

...er...what is 1C? Also, forgot to say it is a 3300mAh NIMH GP batt......

[nic]

1C => 1 x the capcity of the battery.

So, if you are using 3300, 1C = 3.3 Amp
if using 2200, 1C = 2.2 Amp
etc etc

[nightbreed]

I get it. Thanks! So as long as charge below the capacity of the battery, it will not be so hot? Just takes a longer time to reach full charge?

[nic]

Yes... if you charge at 1C... it suppose to take 1 hour.. or maybe slightly more, pending on your charger, the condition of your batts and also the input power source (how clean and stable it is).

If you charge at 0.5 C.. it will take you 2 hours (or slightly more)
If you charge at 2C.. it will take you 0.5 hour...
etc etc

Peak detect chargers are smart enough to vary its current and gradually tapers off as the batt reaches its full capacity. However, this can also be a nuisence when the charger detects wrongly (not unusal) and stops the process way too early.

Best is.. read the manual that came with your charger.. .and refer the specs of your batteries (check the manufacturer web site...), these will tell you more details specific to the batts and the charger that you have.

Cheers.

[nightbreed]

Thanks nic! The 'instructions' that came with the charger not very instructive nor informative. I anyhow poke button...seems to work...

[X34]

Don't use nicad program to charge nimh or vice versa. The wrong program can cause the batt to overheat and explode.

Max temp for nimh is normally 40 deg C. Car boys tend to run them higher. At higher temp the batt is only good for 3 to 6 charge.

[AceViperX]

Actually it is not because of the charge rate that causes the battery to heat up. It is true that a higher charging rate will cause a NiMH batt to heat up faster when it reaches its peak but during charging the battery should only be slightly warm. The C cell batteries can be charged at 1.5 to 2 C without severely affecting its performance.

Also the charging method for a NiMH is different from a Lipo. A Lipo charger will reduce the charge rate as it reaches a voltage of 4.2v per cell. But a NiMH charger detects a full charge by noting a slight drop in voltage as it peaks, and this is irrespective of the actual voltage of the cells. This is what a delta-peak detection means.

If your batts are very hot after a charge, it probably means your charger isn't sensitive enough to detect the peak voltage. Does it have a peak detection setting? If it does, then you may need to set it to a more sensitive level.

If you charge it at 1C... it bound to get very hot if the charger doesn't know how to reduce the current as the batt reaches its peak capacity.

For Nihm... heat will damage the battery... so if you have been heating it to that extend... the battery capacity will drop... sometime very drastically.

[haowee]

My battery is 1800mah. When I charge it it is warm only. But when I use it until the battery is flat, it is very hot. It can almost burn my hand. Very hot.

[nightbreed]

Hmm. It doesn't see mlike my charger has peak detection thingy because there is nothing for me to set. So anyway, I guess I'm not doing anything wrong. But time will tell......

[Mad Armour]

Hmm. It doesn't see mlike my charger has peak detection thingy because there is nothing for me to set. So anyway, I guess I'm not doing anything wrong. But time will tell......

Think your charger's peak detection sensitivity is fixed.

[Awallisk]

Actually it is not because of the charge rate that causes the battery to heat up. It is true that a higher charging rate will cause a NiMH batt to heat up faster when it reaches its peak but during charging the battery should only be slightly warm. The C cell batteries can be charged at 1.5 to 2 C without severely affecting its performance.

Also the charging method for a NiMH is different from a Lipo. A Lipo charger will reduce the charge rate as it reaches a voltage of 4.2v per cell. But a NiMH charger detects a full charge by noting a slight drop in voltage as it peaks, and this is irrespective of the actual voltage of the cells. This is what a delta-peak detection means.

If your batts are very hot after a charge, it probably means your charger isn't sensitive enough to detect the peak voltage. Does it have a peak detection setting? If it does, then you may need to set it to a more sensitive level.

So what the setting should be for the peak charge rate? for 7.2V 3600MAH and 1400MAH and 6V 1000MAH(5 cell receiver batt) :

[AceViperX]

So what the setting should be for the peak charge rate? for 7.2V 3600MAH and 1400MAH and 6V 1000MAH(5 cell receiver batt) :

It really depends if your the delta peak setting on your charger can be set. If it cannot, then your only way to avoid really hot batteries is to monitor its temp as it reaches its peak.

[Awallisk]

It really depends if your the delta peak setting on your charger can be set. If it cannot, then your only way to avoid really hot batteries is to monitor its temp as it reaches its peak.

I'm using a PitBull X3 charger and what is peak setting should be set for all three type of battery?