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Old Oct 24, 2005, 11:01 AM
L58
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Joined Sep 2005
46 Posts
charge rates

I just purchased a mkII field charger and was wondering what rate to set it at for a 7 cell 1150mah nimh battery(for my slowstik). Also, could I use an old receiver charger or similar to power the field charger? Any help would be greatly appreciated.
Thanks, John
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Old Oct 24, 2005, 11:33 AM
Yep I got another one.
mohillbilly's Avatar
Springfield, Mo.
Joined Jan 2005
2,529 Posts
It depends on the size of the cells. If it the frist charge on the pack used the lowest (200mah) after the frist few charges it depends on cell size. I know mine came with a little chart. AAA size cells 400mah, AA size 600mah, A size 1A, and up two 2A for bigger. I know I have poped a pack for AAA GWS cells from charging them at 1A but that was a full charge cycle. I sometime peak my already charged cells @ 1A before I go fly just to get them done fast but its not the best thing to do. Lipos work fine and actually very safe as long on you put it on the right setting. Big Lipos take awhile since you can only charge them at 1A.
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Old Oct 24, 2005, 11:37 AM
Yep I got another one.
mohillbilly's Avatar
Springfield, Mo.
Joined Jan 2005
2,529 Posts
You can't use the TX xharger to power it. BUT you can use other wall plug power supplys just make sure it out puts 12V DC and at least 2A. I use a lawn mower battery with a small car trickle charger hooked up to it. that way I dont run out the battery to much. Some times with I take the battery to the field and charge ALOT of packs off of it it will get too low. this makes the MKII beep forever! and will flash red to green or yellow to green and not shut up. thats the error note letting you know it low on volts or bad connection. the beep after a cycle will be the same color as what it was charging and flash fast and shut up after about 5 to 10 sec.
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Old Oct 24, 2005, 12:01 PM
Naturally altered
Joined Feb 2005
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Maximum charge rate for NiMH`s is 1C. That would be 1.15 amps for your pack. That`s the MAX, charging slower will help with longevity of the pack. 1 amp would be a good compromise. As mohillbilly suggested, it`s best to use a slow charge (200ma) on the first few cycles. This will equalize the cells. You can also do a slow charge every 20 cycles or so.
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Old Oct 24, 2005, 12:13 PM
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Missouri
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NICD's can be charged at 3C, NIMH's at 2C and Lipos at 1C. 1500mah charged at 2C would be 3amps charging rate. 1C = 1 hour, 2C = 30 min and 3C is 20 min charging time.

The max temp the battery can get during charging is 160 degrees. It's a good if the battery gets no hotter during charging as it would normally get during discharging.
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Old Oct 24, 2005, 12:57 PM
Oldie but goodie
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United States, CA, Orange
Joined Jun 2003
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"C" ratings aside, for long pack life charge at the minimum rate that will provide enough power for your plane to fly acceptibly.

Most of my smaller NiCd/NiMh packs "AA" size or less get charged @1A. The 2/3"A" size which is common for the S.S, can be charged @2A without harm if the power is needed.
When I was r/c car racing, I regularly charged my (matched) 3300Mah sub-"C" packs @6-7A. Usable lifetime was reduced, but one had to do this to be competitive.

BTW, I have a tiny 145Mah NiMh pack that gets charged @1A. Anything less and the little plane it goes to, does not have enough power to fly.
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Old Oct 24, 2005, 07:46 PM
L58
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Joined Sep 2005
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Thanks for all the replys. I appreciate all the help since I'm new to the electric scene. Was a little disappointed in the quality of the slowstik though. The tape didn't stick, measurements very vague, etc. I guess the old, "you get what you pay for" is in effect.
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Old Oct 24, 2005, 11:28 PM
volare est vivere
ray foley's Avatar
United States, OH, Toledo
Joined Jan 2005
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Rememer to cool the batteries when charging NIMH packs at over 1C. I routinely use 1.5C for NIMH cells and use a computer cooling fan in a coroplast tube as a battery cooler. This necessary accessory runs on 12 VDC, is made from a RS muffin fan, recycled coroplast from an old election sign . and duct tape. If you dont have one, go make one.

TTFN, rjf
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Old Oct 25, 2005, 11:06 AM
Oldie but goodie
Popsflyer's Avatar
United States, CA, Orange
Joined Jun 2003
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ray foley;

I know from personal experience that cooling NiMh cells while charging is NOT a good thing. Depending on the discharge rate, the pack(s) will be extremely flat like when they've been sitting overnight, and re-peaking does not help.

Best way to reduce temperature is to lower the peak setting on your charger.
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