Questions about aa nimh and charging

[T-roc87]

Hi all! I have been searching but haven't found my answers. I have a hyperion 0606i battery charger which is almost identical to the triton eq. I bought this for my r/c mini revo but want to use it for charging my nimh aa batteries. First off i was hoping some of you guys could share with me how you are charging your aa batteries with a hobby charger. Right now i picked up a battery holder that holds 4 aa but i added a 3rd wire so i could also charge just two aa if i please. I only need to charge my batteries 2 or 4 at a time since i have a fenix l2d q5 and a fenix tk40 which i got for christmas. I also modified the battery holder by replacing the tiny 22awg wire with some 16awg.
Next question. I have some duracell 2650mah batteries and waiting for my eneloops to arrive. I see most guys recommend .5 to 1amp for charging and 1 amp for discharging. Is this recommend becuase the batteries heat up to much if you try to match 1 amp per 1000mah? I am use to r/c trucks and the rule of thumb is usually 1amp for every 1000mah. Just wondering.
Also, great forum here guys and a plethora of knowledge.

 

[mfm]

Next question. I have some duracell 2650mah batteries and waiting for my eneloops to arrive. I see most guys recommend .5 to 1amp for charging and 1 amp for discharging. Is this recommend becuase the batteries heat up to much if you try to match 1 amp per 1000mah? I am use to r/c trucks and the rule of thumb is usually 1amp for every 1000mah. Just wondering.
Also, great forum here guys and a plethora of knowledge.

You are correct, charge at 1C (1A per 1Ah). You can read more here: http://www.batteryuniversity.com/partone-11.htm

 

[SilverFox]

Hello T-roc87,

Welcome to CPF.

Hobby chargers are set up to charge NiMh cells in series. Many of us use clamps to hold the cells as most of the cell holders will melt if you choose a charge current over around 1 amp. You should keep an eye on your set up to be sure it is capable of higher currents.

When charging cells in series it is possible to end up with balance problems, so make sure you take a little extra time to balance the cells that you are charging.

If your charger uses -dV termination, the strongest signals are obtained by charging in the 0.5 - 1.0C range. With 2650 mAh cells, that would be using 1325 - 2650 mA. However, most 2650 mAh actually come in a little under that and end up in the 2400 - 2500 mAh range.

Cells with capacities over about 2000 mAh are consider high capacity cells. They tend to have higher internal resistance, so they will heat up more when charged at higher rates. This leads many people to favor the 0.5C rate over the 1.0C rate.

Also, if your charger uses a different termination method you can explore different charging rates. The goal is to minimize overcharging while still ending up with a full charge.

Tom

 

[T-roc87]

Thanks guys for the great info. Thats what i was worried about. I read some one else say that about the aa holder. Do you have any pictures of a clamp system? I will have to search around. One last question then. Is it better to just charge in parellel over series then?

 

[SilverFox]

Hello T-roc87,

Just do a search in this section for battery clamp, or improved battery clamp and you should find a thread by CPF member Cy.

Parallel charging doesn't work for NiMh chemistry. Don't use it.

Tom