The first few NiMH charges  
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All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> The first few NiMH charges
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The first few NiMH charges - 4/19/2002 1:34:51 AM   
woodscra


 

Posts: 895
Joined: 12/10/2001
From: frisco, TX, USA
Status: offline 		I know for the first charge of a new NiMH it is best to do a good c/10 trickle. How many times should I do the slow trickle charge before I can start fast charging it to get full capacity?

Thanks.
       Post #: 1

The first few NiMH charges - 4/19/2002 1:37:00 AM   
Vince


 

Posts: 1650
Joined: 2/2/2002
From: Nederland, Tx.
Status: offline 		One C/10 charge is sufficient to stabilize the voltage peak. After that it's perfectly OK to fast charge them with a NIMH rated charger.

Vince

(in reply to woodscra)
       Post #: 2

The first few NiMH charges - 4/19/2002 2:00:21 AM   
z11355


 

Posts: 176
Joined: 3/6/2002
Status: offline 		first is most important but it usually takes
about 3-5 full cycles to get a NiMH pack up
to rated output. I was doing 2-3 C/10
cycles before I would ut the pack in use.

(in reply to woodscra)
       Post #: 3

The first few NiMH charges - 4/19/2002 2:10:49 AM   
Red Scholefield



Posts: 5042
Joined: 12/8/2001
From: Newberry, FL, USA
Status: offline 		I would also recommend doing 2 or 3 slow charge cycles before hitting them with a fast charge.

_____________________________

Red S.
AMA 951 Leader Member
Disclaimer: What I have written here are my thoughts and in no manner shape or form reflect the views of RCU

(in reply to woodscra)
       Post #: 4

The first few NiMH charges - 4/19/2002 2:42:39 AM   
woodscra


 

Posts: 895
Joined: 12/10/2001
From: frisco, TX, USA
Status: offline 		Thank you for your information. I will go with doing 2-3 slow charges first.

Do you guys just use them to drain them some or are you guys discharging them?

Another question, when I come home from flying with my new NiMH, I will have no idea how much is left in the battery. Is it OK to charge the battery at 16-18 hrs at the trickle charge rate again even though the pack may (and likely) will be half full?

(in reply to woodscra)
       Post #: 5

The first few NiMH charges - 4/19/2002 5:30:07 AM   
z11355


 

Posts: 176
Joined: 3/6/2002
Status: offline 		I only discharge them a few times a season
to make sure of their capacity.

Don't confuse 'trickle' rate w/ 'slow charge'
rate.

This is where some sort of decent charger
or cycler comes in handy, so you can see
what is going on w/ your batteries. I know
as a fact that my machines draw about 250mA per flight from the pack

Battery Clinic:

Is this a 250 mAh average discharge, because you put no time dimension with it. If you draw 250 mAh (note time referance) with a flight, how long are your flights?

z11355: Average. I know from experience
that a 'standard' flight on my
helicopter will draw out somewhere around
220-250mA of charge from the time I power up to
power down. That is about 10 minutes of
flight. I can put the machine back on the
charger and be fairly accurate as to how
much charge the charger will put into the
battery.

BC: Best way to check this is to discharge a fully charge pack, record the capacity, charge fully, go fly and record the time the systeme was turned on. Discharge pack immediately when returning to the shop and see how much is left. This will give you a reasonable handle on just how much your system is using per minute. Knowing this you can get a pretty good idea of how long you can expect to safely fly on a fully charge pack.

Z: Done that. However, w/ multi-kilobuck
machines, I tend to play it a bit conservative
and will throw it backon the Sirius for a bit after 4 flights on a 1700AU pack.

< Message edited by z11355 -- Apr 19 2002 11:19AM >

(in reply to woodscra)
       Post #: 6

The first few NiMH charges - 4/19/2002 9:58:09 AM   
Bern


 

Posts: 16
Joined: 2/12/2002
From: Simi Valley, CA, USA
Status: offline 		A fully charged 4.8V NiMH pack should read 5.6V or better. Do not discharge the pack beyond 5.0V.

Battery Clinic: The accepted protocol for discharge cut of (the level below which you should not go so as to not reverse a cell) is (N-1) X 1.2 volts. Or in the case of a four cell pack (4-1) X 1.2 = 3.6 volts. Normally one volt per cell is acceptable for packs up to 8 cells. This are voltages read while the pack is still on discharge. Taken off the charter the voltage will spring back to 4.8 or better.

Get a good meter and read the pack as you take it
of the charger. Record this voltage. When you return home from flying and before charging, check the voltage. This way you can figure how long to charge.

Battery Clinic: Reading voltage to determine capacity is a pretty much a guessing game. About the only way you can determine capacity remaining is to discharge the pack. The pack voltage at end of charge, when pack is fully charged, will be somewhat dependent on the charge current. It should read something between 5.8 and 6.0 volts when charging at C/10

Contrary to popular belief fast charging
does not fill the packs full. Some cells need more time. Slow charging is still best.

Battery Clinic: A topping charge (C/10)of 2 or 3 hours is recommended after fast charge terminates to take pack to maximum level of charge.

It also may take more than 2-3 times to get a NiMH pack to top performance. Have seen 7-8 times before the cells perform to capacity. Trickle charging is not good unless it is very low capacity (Battery Clinic: charge current) where the pack does not get hot. Email me if you need help.

< Message edited by Red Scholefield -- Apr 19 2002 8:38AM >

(in reply to woodscra)
       Post #: 7

The first few NiMH charges - 4/20/2002 6:50:46 PM   
jmulder



Posts: 1276
Joined: 12/16/2001
From: NC
Status: offline 		I didnt know to slow charge my nimh batts. first. I've had them for just a few weeks and now for some reason they wont charge up at all. I dont know if it's the battery or the charger. I have the Hi-Tec 340 and it never cuts off now. It worked fine for a few weeks but now.....well......nothing....Any suggestions?

(in reply to woodscra)
       Post #: 8

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