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All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> MRC Charger Product Support (i.e. Super Brain, etc) >> SB 989 problem
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SB 989 problem - 7/7/2007 11:52:18 PM   
saucisse


 

Posts: 8
Joined: 5/1/2007
From: Quebec City, QC, CANADA
Status: offline 		I'm trying to charge a 6cells 7.4V nimh pack with my superbrain 989 and the max mah that went in once the charging was finished is 915mah after an hour of trikle charge at 0.10.

THis is a new pack and I did 5-6 cycles charging at 2600mah, peak sensitivity at 5mv. Discharging at 3500mah, cut of at 1v/cell.

CAn someone tell me what I'm doing wrong?

THanks.
       Post #: 1

RE: SB 989 problem - 7/8/2007 12:01:51 AM   
guver


 

Posts: 9118
Joined: 3/7/2003
From: LaGrange, OH, USA
Status: offline 		You might be confusing capacity (mah) with rate (amps) ? If I understand properly.

The trickle charge you mentioned .1 amps will add 100 mah in 1 hr. The fast charge rate is what info is missing and the 5 mv is good.

If the pack is a large subC pack then a rate of 3 amps or so and if it's a AA then use 1 amp or less.

I think I don't quite understand what your asking, anyways, Welcome to the forum.

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       Post #: 2

RE: SB 989 problem - 7/8/2007 12:57:43 AM   
saucisse


 

Posts: 8
Joined: 5/1/2007
From: Quebec City, QC, CANADA
Status: offline 		Hi guver!

I'm chargin at 2.6amps...sorry my mistake.

What I mean is that the charger displays the amount of mah that were added in the pack during charging... when charging's completed, the pack fully charged shoud show somewhat around 2600mah, no ?

Thanks!

< Message edited by saucisse -- 7/8/2007 1:00:36 AM >

(in reply to guver)
       Post #: 3

RE: SB 989 problem - 7/8/2007 1:10:55 AM   
guver


 

Posts: 9118
Joined: 3/7/2003
From: LaGrange, OH, USA
Status: offline 		Yes, if it was empty or close to it. 2.6 amps is good rate.

If you are getting 915 when charged what are you getting when you discharge?

If its the full 2600 then it was full and if it is only 915 then the pack was only partial full. Obvious , I know.

I sure like doing a slow c/10 charge for 15 hrs right off the bat with a non-peaking charger and then I prefer manual charge or a manual discharge rather than "cycling"

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       Post #: 4

RE: SB 989 problem - 7/8/2007 6:14:45 PM   
saucisse


 

Posts: 8
Joined: 5/1/2007
From: Quebec City, QC, CANADA
Status: offline 		Getting around the same when discharging then charging...

(in reply to guver)
       Post #: 5

RE: SB 989 problem - 7/8/2007 6:20:02 PM   
guver


 

Posts: 9118
Joined: 3/7/2003
From: LaGrange, OH, USA
Status: offline 		It could be a weak cell of two in the pack or the pack is just bad. Best thing to do to make sure is to do a c/10 charge for 15 hrs on the empty pack and then discharge it normal to check capacity. This will guaruntee it is full before you start the discharge. Right now it's hard to tell if you are operating on the bottom half or the top half of the pack.

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       Post #: 6

RE: SB 989 problem - 7/8/2007 8:25:07 PM   
saucisse


 

Posts: 8
Joined: 5/1/2007
From: Quebec City, QC, CANADA
Status: offline 		I just took apart the pack so I can check each cells one by one...what would be the correct procedure to do so

I should get the same mah in when charging then when discharging a cell, right?

(in reply to guver)
       Post #: 7

RE: SB 989 problem - 7/8/2007 8:49:18 PM   
guver


 

Posts: 9118
Joined: 3/7/2003
From: LaGrange, OH, USA
Status: offline 		When chargeing at a fast rate the capacity should match the capacity on the battery, and be a bit less when dischargeing at a fairly fast rate.

You can charge the whole pack at c/10 rate with a charger that doesn't shut off for 15 hrs and then discharge each cell noting the capacity of each one seperately.

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       Post #: 8

RE: SB 989 problem - 7/9/2007 2:43:02 PM   
Tim@MRC


 

Posts: 366
Joined: 7/24/2006
From: Edison, NJ, USA
Status: offline 		Also, it very typical for a new NiMH battery to false peak. You might have to go through a few cycles to get a true capacity rating. Guver is right, a slow charge is usually the best way to determine the capacity of a battery, but with NiMH you can safely charge them at 1C all the time with no detriment to the battery and still get a fairly accurate determination of the capacity. It's on the discharge that I would go a little slower to accurately tell how much is in the pack. A high discharge rate tends to drop the voltage in the battery too fast. I would discharge at 1C also, just to get an accurate reading.

(in reply to guver)
       Post #: 9

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All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> MRC Charger Product Support (i.e. Super Brain, etc) >> SB 989 problem
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