Rayovac Hybrid coming out of the charger burning hot

[WildChild]

I'm using a Sanyo Quick Charger from Costco (gray, came with 2500 mAh Sanyo cells). When my Rayovac Hybrid are ready, they always are burning hot. What could explain that? They are the only NiMH I have that does that. I use it with Energizer 2500 mAh, Duracell 1800 mAh, Eneloop without any problem.

 

[Mr Happy]

What's the model number on the back of the charger? There are many different Sanyo chargers out there and the knowing the particular charger may give more insight.

Perhaps the Hybrids are not giving a good end of charge signal and they are terminating on a back-up test like high temperature or timer...?

In spite of a strong desire to believe otherwise, not every NiMH cell is born equal.

 

[WildChild]

This one: http://us.sanyo.com/batteries/pdfs/MQH01_manual.pdf

 

[Mr Happy]

Oh...that's a quick charger

I guess the quality of the Hybrid's may not be as good as the other cells. How is the temperature in the middle of charging? Good quality cells will stay cool until 5 minutes before charging is over and then suddenly start warming up. Poor quality cells will get steadily hotter all through charging and then get extremely hot right at the end.

If you have a Maha C9000 it would be an idea to put them through a conditioning cycle or two.

 

[WildChild]

I have no Maha C9000 (but I would like to have one some day). They are approximately 9 months old and they have been cycled, down to 1V every 3 weeks. They are being used in my XBOX controllers.

 

[SilverFox]

Hello WildChild,

Interesting...

That is one of my favorite chargers. It allows for quick charging AA cells in the outer slots, or a little slower charging using the inner or a pair of slots. You can even go to slower charging by flipping the switch over to NiCd, but I am not sure what termination is used with it in that position.

The evidence suggests that your cells are developing higher internal resistance. The charger is supposed to monitor temperature and shut down when the temperature exceeds 104 F, so there may be a malfunction of the charger.

If you want to try something...

Flip the switch to NiCd and use one side or the other. The idea is to not use the Quick charge feature. You will have to keep track of temperatures at the end of the charge, but you may be able to charge cells with higher internal resistance this way.

I have not tried this, so understand that it is an educated guess...

If that works better, then you can try the NiCd position with cells in the Quick slots only to speed things up a little.

Tom

 

[WildChild]

Thanks for your reply! Those Hybrid have been acting like that since the beginning. I just decided to ask about this now! Even the charger becomes hot with those. I'll try something else. I have a new charger of the same model I have not been using much (2-3 times) and on other NiMH only. I'll try to charge them in this charger to see what happens.

[edit]By the way, the charger does stop the charge (red light turning off).[/edit]

Hello WildChild,

Interesting...

That is one of my favorite chargers. It allows for quick charging AA cells in the outer slots, or a little slower charging using the inner or a pair of slots. You can even go to slower charging by flipping the switch over to NiCd, but I am not sure what termination is used with it in that position.

The evidence suggests that your cells are developing higher internal resistance. The charger is supposed to monitor temperature and shut down when the temperature exceeds 104 F, so there may be a malfunction of the charger.

If you want to try something...

Flip the switch to NiCd and use one side or the other. The idea is to not use the Quick charge feature. You will have to keep track of temperatures at the end of the charge, but you may be able to charge cells with higher internal resistance this way.

I have not tried this, so understand that it is an educated guess...

If that works better, then you can try the NiCd position with cells in the Quick slots only to speed things up a little.

Tom

 

[Black Rose]

I've haven't noticed that with the Hybrids I have here, but I charge them at a rate that runs for 2 hours (0.5C on a C9000).

Next time I have some that need to be charged, I'll try them at 1C and see if they heat up like yours are.

 

[WildChild]

Tested with the newest charger, on fast channels. Both cells came out at around 1.46V and they were still burning hot. They started to heat in the middle of the charging process and they heated up fast in the last 10 minutes before the charging process ended. I'm now trying to charge my second set on my regular charger on the slow channels.

 

[WildChild]

With a 2h charge, they did heat but not as much.

 

[Black Rose]

I got bored and decided to do a test on my C9000.
I discharged 2 Hybrids and 2 Eneloops at 1A and then took them out of the charger to let them cool down.

Once they were cool, I placed them in the C9000, Hybrids in locations 1 & 2, Eneloops in 3 & 4, and charged at 2000 mA.

After 35 minutes, the temps (Celcius) were as follows:
32, 35, 31, 29

After 55 minutes, the temps (Celcius) were as follows:
34, 39, 34, 31

After charge termination (62/67/64/62 minutes) I couldn't keep my fingers on the Hybrids for more than 5 seconds, they were too hot.

The measurements are far from scientific, but do show that not all batteries are made the same.
I used my wife's candy thermometer (shhh, don't tell ) to get the temps. The thermometer was dipped it in cool water and dried off between each cell reading to cool it down.

I had expected the two middle cells would be warmer than the outer two cells just because of the charger design and the extra cooling capability of the outer cell chambers.

 

[alfreddajero]

Coming from the RC world you can try putting on a heatsink on that brand of cells......so this way the heatsink will take the heat away while its charging.

 

[Meltdown]

interesting. when I charge my D sized Titanium NiMH's on an Energizer Accu charger they come out so hot I can't hold them for long...??

will that kill my cells? I have two identical chargers and they both do this.

 

[HarveyRich]

Not exactly sure what this will add to the conversation here, but if you're interested in a really quick charger, it might be useful to know that I have a very quick charger and the batteries get warm, but not hot, usually. It is the NiMH single channel Vanson charger Model V-8000. Typically it can charge a fully discharged AA cell in 35-40+ minutes, depending upon how many Mah in the battery. The unique aspect of this charge, to me anyway, is that there's a fan built into the charger which blows air across the batteries and helps to keep them from heating up much too quickly because of the quick charge aspect of it.

From the specs on the back, it looks as if it is charging 4AA batteries at 4A or 4AAA at 1.7A.

 

[alfreddajero]

Yes heat will kill the longevity of the cells......they will become shortlived.

 

[alfreddajero]

I found this by doing a search.....some great info on batts.

http://www.whenshtf.com/showthread.php?t=2153