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[ChrisH1981]

Good morning all. I have a question relating to nimh batteries. I have just purchased 2 new 7.2 nimh packs from hobbyking. They are Turnigy 5000 mah. I have purchased them to replace some older nimh sticks that I had, one of which had a bad cell. I am unfamiliar with battery technology and so I want to look after these batteries and charge them with care. Firstly, do I need to condition these batteries before first use? Will cycling them before use help the batteries to condition?. And secondly, how should I charge them after discharging them? How many amps should I charge the batteries at? High or Low? Your thoughts are appreciated!

[canabus]

Hi Chris


Divide 5000mah by 1000 equals the maximum charge rate 5 Amps .


For safe charging half of that 2.5 Amps !!!


I never charge at the maximum charge rate because it heats up the battery and you do not get a full charge, also shorten the battery life.


I use the same for Lipo batteries, but with a balance charger and safety bag.


Canabus 

[ChrisH1981]

Hi Chris


Divide 5000mah by 1000 equals the maximum charge rate 5 Amps .


For safe charging half of that 2.5 Amps !!!


I never charge at the maximum charge rate because it heats up the battery and you do not get a full charge, also shorten the battery life.


I use the same for Lipo batteries, but with a balance charger and safety bag.


Canabus

Thanks good advice! Do you use a smart charger to charge your nimhs also?

[Dave_S.]

I have a couple of packs of exactly the same voltage and capacity, I charge at 2.5A and have had no problems with them whatsoever.

[justboatonic]

Good morning all. I have a question relating to nimh batteries. I have just purchased 2 new 7.2 nimh packs from hobbyking. They are Turnigy 5000 mah. I have purchased them to replace some older nimh sticks that I had, one of which had a bad cell. I am unfamiliar with battery technology and so I want to look after these batteries and charge them with care. Firstly, do I need to condition these batteries before first use? Will cycling them before use help the batteries to condition?. And secondly, how should I charge them after discharging them? How many amps should I charge the batteries at? High or Low? Your thoughts are appreciated!

There is a fallacy that nicads had a 'memory' but this only ever manifested itself under strict laboratory conditions. As far as Im aware NIMH cells are not shown to have any 'memory.'
Always charge ANY battery at 1C to prolong their life. 1C = the pack's capacity. For a 5000mah pack, 5 amps is 1C and is fine.
The best way to condition cells is to discharge all of them in a pack to the same voltage before recharging. This can be difficult with sealed packs covered in a plastic sleeve. The RC car boys frequently use a 'discharge tray' where all the cells in the pack are in physical contact with a positive and negative terminal attached to either a resistor or bulb. To use a discharge tray,you may have to cut into the plastic sleeve covering both sides of the pack for this to work.

These trays safely discharge each individual cell down to the same nominal voltage.
If you fast charge NIMH packs ie at multiples of C such as 2C (10 amps for a 5000mah pack), 3C (15 amps for a 5000mah pack), every 5 or so charges should be a slow charge. This is normally 1C or less with the idea being to charge each cell slowly up to capacity. But as I mentioned, if the cells arent discharged to the same level, you can create an inbalance in the pack that could eventually make 1 or more cells go bad.

[ChrisH1981]

There is a fallacy that nicads had a 'memory' but this only ever manifested itself under strict laboratory conditions. As far as Im aware NIMH cells are not shown to have any 'memory.'
Always charge ANY battery at 1C to prolong their life. 1C = the pack's capacity. For a 5000mah pack, 5 amps is 1C and is fine.
The best way to condition cells is to discharge all of them in a pack to the same voltage before recharging. This can be difficult with sealed packs covered in a plastic sleeve. The RC car boys frequently use a 'discharge tray' where all the cells in the pack are in physical contact with a positive and negative terminal attached to either a resistor or bulb. To use a discharge tray,you may have to cut into the plastic sleeve covering both sides of the pack for this to work.

These trays safely discharge each individual cell down to the same nominal voltage.
If you fast charge NIMH packs ie at multiples of C such as 2C (10 amps for a 5000mah pack), 3C (15 amps for a 5000mah pack), every 5 or so charges should be a slow charge. This is normally 1C or less with the idea being to charge each cell slowly up to capacity. But as I mentioned, if the cells arent discharged to the same level, you can create an inbalance in the pack that could eventually make 1 or more cells go bad.

Excellent post there, thanks very much for sharing your thoughts