T E A M
Well, I'm sure those who have used NiMH for high drain applications will kind of do some research on the batts.
For myself, after hearing a lot of theories, myths, collecting info from the RC EP Car guys, and doing my own research, I have come to some conclusion for my own theory about my applications.....
My amp draw on my cells are about 30 amps peak......kinda being abused, but still within 10C continous draw limits for 3600mah Sub-C cells.....and I cannot afford to have flight failures.....so battery & flight duration is critical to me.
It's up to the individual who choose to believe or not, and I welcome comments so that I can experiement more on my charging methods.
Myth 1:
NiMH batteries should be trained to charge at 1.5C or 2.0C or above, so that they can deliver high current output for punch.
My findings:
I think it's not necessarily true. I cycled my packs at 1.5C ratings, and the punch is also not evident...In fact, I find that the batteries cannot sustain longer usage time when charging at 1.5/2.0C rate. Battery will NOT attain full capacity.
When charged at 1C or above, packs should be cooled down to allow chemical reaction to rest and set in, before applying a low current trickle charge to top off & re-peak.
Overall, I find that charging at below 1C rating (slow charge) is still better for my application. My packs will last longer. Punch is always attained when I re-peak my cells at 1C rating just prior to my flights.
Despite manufacturer's recommendations to charge at 1.5C, I still think that the advantages of low current charge is better.
Low current charge at about 0.5C helps to equalise all the cells in the pack. Higher current charging at 1C or above will result in unbalanced cells.
Myth 2:
NiMH batteries must be discharged prior to charging. (all my EP car friends like to do that)
My findings:
I think it's a waste of battery life to cycle NiMH batts. Why? They do not have memory effect. Only good advantage for batteries to be cycled is to re-balance individual cells in the pack. drain off individual cells to 0.8v per cell, and then recharge till peak to check for the pack's capacity.
Just my two cents worth of info sharing... I strongly welcome comments if anyone have experiemented and tried different charging techniques.
For myself, after hearing a lot of theories, myths, collecting info from the RC EP Car guys, and doing my own research, I have come to some conclusion for my own theory about my applications.....
My amp draw on my cells are about 30 amps peak......kinda being abused, but still within 10C continous draw limits for 3600mah Sub-C cells.....and I cannot afford to have flight failures.....so battery & flight duration is critical to me.
It's up to the individual who choose to believe or not, and I welcome comments so that I can experiement more on my charging methods.
Myth 1:
NiMH batteries should be trained to charge at 1.5C or 2.0C or above, so that they can deliver high current output for punch.
My findings:
I think it's not necessarily true. I cycled my packs at 1.5C ratings, and the punch is also not evident...In fact, I find that the batteries cannot sustain longer usage time when charging at 1.5/2.0C rate. Battery will NOT attain full capacity.
When charged at 1C or above, packs should be cooled down to allow chemical reaction to rest and set in, before applying a low current trickle charge to top off & re-peak.
Overall, I find that charging at below 1C rating (slow charge) is still better for my application. My packs will last longer. Punch is always attained when I re-peak my cells at 1C rating just prior to my flights.
Despite manufacturer's recommendations to charge at 1.5C, I still think that the advantages of low current charge is better.
Low current charge at about 0.5C helps to equalise all the cells in the pack. Higher current charging at 1C or above will result in unbalanced cells.
Myth 2:
NiMH batteries must be discharged prior to charging. (all my EP car friends like to do that)
My findings:
I think it's a waste of battery life to cycle NiMH batts. Why? They do not have memory effect. Only good advantage for batteries to be cycled is to re-balance individual cells in the pack. drain off individual cells to 0.8v per cell, and then recharge till peak to check for the pack's capacity.
Just my two cents worth of info sharing... I strongly welcome comments if anyone have experiemented and tried different charging techniques.