Just checking if my GP batt is normal.

[gomobile]

Hi All,

Just finish charging my 2700 GP batt and i realise one of the batt is hot to the point that it's impossible to handle, i have to leave it on the table before i can touch it without burning my fingers. Is it normal for rechargables to heat up so badly when charging?

Only one of the batt seem to be specialy hot and takes longer to cool than the other three.

 

[morningstar]

Hi All,

Just finish charging my 2700 GP batt and i realise one of the batt is hot to the point that it's impossible to handle, i have to leave it on the table before i can touch it without burning my fingers. Is it normal for rechargables to heat up so badly when charging?

Only one of the batt seem to be specialy hot and takes longer to cool than the other three.

Yes, that means that battery is depleted. If you drain the battery to a point so low, it'll take a long time to recharge esp. those 2700 mha. FYI, there are cases of people charging batteries until the charger compartment melted!!!

 

[Artosoft]

Then, if you have charger with opt to slow charger, use it.

I hear that's why now some charger sold without its chamber's lid. To prevent too hot when charging.

Regards,
Arto.

 

[Scaglietti]

Hi All,

Just finish charging my 2700 GP batt and i realise one of the batt is hot to the point that it's impossible to handle, i have to leave it on the table before i can touch it without burning my fingers. Is it normal for rechargables to heat up so badly when charging?

Only one of the batt seem to be specialy hot and takes longer to cool than the other three.

Mark that battery. After the next use, check if the same battery is heating up more again. If it is so, there may be a fault in the battery. It might have discharged more than the rest of the battery.

I have set of 4 Energisers which 2 of it will discharge much faster than the rest. They are faulty ones which cannot hold charge more that 1 or 2 days.

BC

 

[sulhan]

Hi There,

The heating of battery that you are experiencing is probabaly due to topping off charging - i.e trying to finish off the 80~100% of the battery capacity.

Nimh batteries does not heat up to the "too hot" level when charging to its 80% capacity - in general.

Therefore, a timed/smart charger that match the batteries capacity is important. Say an NiMh charger is to charge a 2500mAh and its internal pumping of current of fast charge stops after say 2hrs (where 80% of it has been reached) the subsequent topping off is done in a trickle charge sequence where lower current is used through some specific cyclic instances until the battery reaches its 100% capacity. E.g Using a charger suited for a 2000mAh may not be good for 2500mAh.

Therefore, if you have a non timed/smart charging that just does a dead-reckoning type of charge, you may end up in heated batteries - and even venting due to the expansion of safety features within battery.

Repeatitive over heating will result in electrolyte degradation and even vaporization that may result in shortening of battery life - lowered capacity as time goes by.

The best approach is to use match dedicated charger by capacity if possible. Although there are other charge status measurement via DV/Dt sensing...in any case best to use proprietary chargers by manufacturers of the battery brands themselves.

High speed charger (e.g 1hr) types are usually dedicated charger that are timed for charging specific battery suited for these charge rate. Do not just chuck any other brands into these battery chargers...

 

[OlyFlyer]

Hi All,

Just finish charging my 2700 GP batt and i realise one of the batt is hot to the point that it's impossible to handle, i have to leave it on the table before i can touch it without burning my fingers. Is it normal for rechargables to heat up so badly when charging?

Only one of the batt seem to be specialy hot and takes longer to cool than the other three.

I have also a set of four GP 2700mAh that I bought together with a GP charger. I read later that the high capacity batteries need a new type of charger too, one that charges each battery individually, not by pair or all the four at the same time. The one I have is a bit slow, 3-5 hours but that supposed to be better than the fast chargers. During charging these batteries get very very hot, so hot that I can not hold them for more than a few seconds after a while the charger started to work. That is normal. Those batteries have internal thermal protection so that is OK, just give them a few minutes to cool off after charge before you put them into your gear.

I actually had the same problem with one battery as you describe, and in fact even worse, one battery always flashed red (charging error) when I tried to charge it the second time, i.e. after the first use. Of course, I marked the battery as scaglietti says, I tried it in all positions, mixing with all the other three. No help, still red. I checked the battery with a volt meter and noticed reverse polarity, which I thought was strange since I only used it together with the other three in my flash. So I charged the three OK ones and when those were ready I tried the failed one by itself again, thinking to give a last chance before I returned to the seller. It charged without a problem. The battery is clearly marked but I can not see any more problems with it. Since then it has been charged at least 20-30 times without a problem.

To the best of my knowledge, the polarity can not be reversed if used normally, my flash works fine and as I said, I did not abuseed or short circuited the battery nor did I inserted reversed into the charger or the flash. So, why did it happen? :dunno: I guess it has something to do with manufacturing. I always use my flash batteries until the flash stops working since that happens without any noticable warning signs. I also have two sets of 2500mAh Sanyo batteries, and these gets also very hot every time. In fact, I feel a bit uncomfortable to charge them while the family is sleeping, so I try to do it during the day. Maybe I am just too cautious.

 

[OlyFlyer]

Hi There,

The heating of battery that you are experiencing is probabaly due to topping off charging - i.e trying to finish off the 80~100% of the battery capacity.

Nimh batteries does not heat up to the "too hot" level when charging to its 80% capacity - in general.

Therefore, a timed/smart charger that match the batteries capacity is important. Say an NiMh charger is to charge a 2500mAh and its internal pumping of current of fast charge stops after say 2hrs (where 80% of it has been reached) the subsequent topping off is done in a trickle charge sequence where lower current is used through some specific cyclic instances until the battery reaches its 100% capacity. E.g Using a charger suited for a 2000mAh may not be good for 2500mAh.

Therefore, if you have a non timed/smart charging that just does a dead-reckoning type of charge, you may end up in heated batteries - and even venting due to the expansion of safety features within battery.

Repeatitive over heating will result in electrolyte degradation and even vaporization that may result in shortening of battery life - lowered capacity as time goes by.

The best approach is to use match dedicated charger by capacity if possible. Although there are other charge status measurement via DV/Dt sensing...in any case best to use proprietary chargers by manufacturers of the battery brands themselves.

High speed charger (e.g 1hr) types are usually dedicated charger that are timed for charging specific battery suited for these charge rate. Do not just chuck any other brands into these battery chargers...

While as a general discussions, the above is true, as a specific discussion on NiMH it is partially wrong.

It is normal that NiMH batteries can get very hot, which is clearly stated in the manual for all my batteries. There is no way to avoid heat, the faster you charge the hotter they get. The more capacity they have the hotter they get, since they need more current to charge. This has nothing to do with brand. I have the GP 2700 and the charger that came with it is also a GP intelligen charger. Charging is NOT timed. The only timer in the charger is one that indicates error if the batteries are not charged after 14 hours. In that case charging stops and the error led flashes. Charging works through checking of heat, current and voltage, but not timed. Timed NiCd chargers are dangerous and should never be used with NiMH type, since it may cause explosion. In a proper charger the heat is checked to avoid overheating which may demage the batteries or cause fire. If there is a tendency of overheating the charge current is lowered automatically, which in turn increases the time it takes to charge. Chargers should never be covered or placed somewhere without some free air around them.

The charger I have for the GP 2700 is one that can charge ANY NiMH batteries BELOW 2700mAh of ANY brand. There are just two warnings, don't mix brands and don't mix capacity. You can charge 1, 2, 3 or 4 batteries at a time and charging time varies, depending on the capacity of battery and the discharge level they are in. Even when charging 4 that has been used in my flash (where they are connected serially) during charge the ready indicator LEDs are not lit all four at the same time, but depending in which order each battery is ready.

It is a common misunderstanding that fast chargers are better than slower ones. That is wrong. For the battery life, the slower you charge the better it is (within a reasonable limit). But it is true that a charger that is not designed for the capacity of your batteries may not be able to charge them fully.

 

[morningstar]

TS, if you area heavy of Nimh batteries, you might want to consider getting a Battery Analyser, you can read more about it here http://www.eastgear.com/shop/product_info.php?products_id=935 . But it is not cheap lah.