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Scorpion Power Hitec RCD
HelicopterMain Discussion › discharging 5 cell and 4 cell nimh batteries
ch53jay

Heliman

Capitol City, Cali

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I am learning about nimh batteries charging and discharging. My first concern is discharging and i have bought a hitec x1 pro and am trying to discharge my 5 cell nimh 1900 mah aa battery pack and need to know what amp and volt to discharge it at. My second ques is what amp and volt to discharge my 4 cell nimh 1800 mah aa battery pack at. Then my final ques is what amp and volt to charge the 4 cell aa battery pack at and my 5 cell aa battery pack at. Thanks for all you help. Jarrid

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02-03-2017 08:12 AM
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Richardmid1

rrProfessor

Leeds, England

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Ok, voltage doesn't matter when talking about charge and discharge so the same will apply for a 4 or 5 cell battery.

So the capacity of your packs is 1800 and 1900mAh or 1.8 and 1.9Ah. Therefore a 1C (1x Capacity) charge or discharge would be at 1.8 or 1.9A.

I personally would start a discharge at 0.5C (900 or 950mAh)(0.9A or 0.95A) and check the battery periodically to make sure it's not getting too warm.

With charging, slowly is kinder to the battery so start at 0.1C (180 or 190mAh)(0.18A or 0.19A). You can go upto 0.5C but again check the battery isn't getting too warm.

60% of the time, it works every time!

02-03-2017 10:44 AM
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MartyH

rrProfessor

USA

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+1 ^^^^as explained.

You can go 1C with no problem. I have done so routinely since the 1990's. I'm using a Litco Alpha 4. If you have the time, a C/10 charge is more gentle to the batteries and offers maximum life.

02-03-2017 12:49 PM
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Ace Dude

rrProfessor

USA

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You may find this FAQ helpful:

http://hangtimes.com/rcbattery_faq.html

  

02-03-2017 12:57 PM
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BeltFedBrowning

Key Veteran

Kansas City

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+1. I discharge mine at .5c and charge at .3 amp if there is time. The batteries like it better. If you are using the charge/discharge on your charger, the .3 amp charge may time out before it finishes.

perfer et obdura; dolor hic tibi proderit olim

02-03-2017 01:59 PM
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ch53jay

Heliman

Capitol City, Cali

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Please excuse my ignorance
1) so the nimh discharge for my 4 or 5 cell 1800mah nimh battery pack will be 2.0 amps and the cut will be .5v?
2)and the charge current will be .5a?
3)the auto charge current will be 1.0 a?

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02-03-2017 02:09 PM
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Richardmid1

rrProfessor

Leeds, England

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Your charger will cut off the discharge when the pack is discharged. I always thought you discharged them fully but maybe that's Nicd. If your charger says the discharge cutoff is 0.5v/cell then that's what it is.

60% of the time, it works every time!

02-03-2017 02:46 PM
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Heli_Splatter

Key Veteran

Silver Spring, MD by way of Sidney, Ne - USA

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I have never discharged any of my NiMH packs. They seem to do it all by themselves.

02-03-2017 03:08 PM
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jharkin

Senior Heliman

Holliston, MA - USA

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Read the authority on Ni' batteries: Red's battery clinic

http://hangtimes.com/redsbatteryclinic.html

For discharing NiMH you have some options.

If you want to discharge them to verify capacity, the industry standard is to discharge them at C/5 (5 hours) down to 0.9 volts/cell.

Thats:
380mA to a 4.5v cutoff for your 5 cell
360mA to a 3.6v cutoff for you 4 cell

The rule is if this tests gives you at east 85% of the capacity on the label the cells are good. If they dont, do 2-3 full dicharge/slow charge cycles and test again. If they still fail, its disposal time.

If you want to check usable capacity as a reciever pack the old rule of thumb is to use the same rate but a 1.1 volt cutoff (so 5.5 and 4.4 respectively)

If you want to do a quick discharge 1C is fine. The only reason you would need to do this is if the cells are tired or where abuse and you wanted to do a few cycles to try and refresh them. In general NiMH do not suffer the "memory" effects of nicad and dont really need periodic cycling.

For charging either use a wall wart type slow charger at C/10 (180mA) and time it to 16 hours - or use a peak detecting charger set to 0.5C-1C (900ma-1.8A).

A few tips on fast charging:
- Make SURE the charger is set to NiMH not NiCD since they have different dV settings.
- Do notuse a peak detection charger lower than about 0.3C, use a timer instead. Ive tried really slow charging on a peak charger and it sometimes misses the peak and overcharges them....
- If the cells get hot (not warm, hot) during charging, stop the charge.
- If these are low self discharge NiMH ("Eneloop" cells, its better to keep the charge to around 0.5C.... they dont fast charging.

-Jeremy
Whiplash-G
Helix 700G
T-Rex 450 fbl conversion
alot of planks

02-03-2017 08:29 PM
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ch53jay

Heliman

Capitol City, Cali

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ok I have the hitec x1 pro with powerbox 17a and the selections i have are as follows
1)trickle <100mh>
2)peak delay <1min>
3)temp cutoff <50c>
4)discharge current <.2 a>
5)discharge voltage <1.0v/cell>
6)delta peak sense <4mv/c>
7)battery volts <6.0 (5 c)>
8)charge current <0.1 a>
9)nimh charge current <0.3 a>
10)nimh auto charge current <5.0 a>
11)nimh discharge <0.3 a> cut: <4.5v>
12)nimh repeak <1>
13)nimh cycle <discharge/charge> <3>
14)rest time charge / discharge <8 min>
15)ext. temp <0 c> int temp <24c>
16)input power <low> cutoff <11.0v>
17)capacity cutoff <on> <2200mah>
18) safety timer <on> <120min>
Everything in < > brackets are on the lcd screen of hitec x1pro with epowerbox17a charger is adjustable. I have read and tried to understand the reds battery clinic and understand some of it but when it comes to programming the charger to do specific tasks for the nimh battery I get confused. If you could please educate myself on each of the numbered steps listed above for a 5cell AA HR6 1900 mah technical products battery pack so i can try to decipher the settings this way and maybe it will make more sense to me. Again thanks for your help and patience to help me understand real world application, Thanks

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02-03-2017 10:16 PM
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ch53jay

Heliman

Capitol City, Cali

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Just to add i think this is why im getting glitches is because of my ignorance to how critical battery information and understanding really is to a 90 size large scale gas helicopter.

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02-03-2017 10:27 PM
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JuanRodriguez

Elite Veteran

The Villages, Florida

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If I were you, I would consider dumping the old battery technology and go with something like a A123 LIFE battery.......

Been there, done that and old enough to know better.....

02-04-2017 12:02 AM
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Heli_Splatter

Key Veteran

Silver Spring, MD by way of Sidney, Ne - USA

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+1 on dumping Ni-xx technology. I quit buying that several years ago and have never looked back.

02-04-2017 11:58 AM
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tommytt1

Veteran

Mercerville, NJ, USA

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I use nimh, life, li ion, and Lipo. I use the nimh in my 90 because of the weight to help balance. They all have there pluses and minuses.

5cell AA 1900mah seems small on a 90 size helicopter to me.

I use a sub C 3000mah running through a deans T connector.

I made a mistake once, but I was wrong?

02-04-2017 01:24 PM
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JuanRodriguez

Elite Veteran

The Villages, Florida

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Only thing I use NiCd or NiMh batteries for anymore is for bench testing my stuff.... So for me, they do have their place !

Been there, done that and old enough to know better.....

02-04-2017 02:03 PM
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MartyH

rrProfessor

USA

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You can use the 5/4 AA size 5 cell NiMH for non hard 3D 90 size nitro helis. I use the JR brand 4500ma pack in this size in my Raptor 90's.

02-09-2017 06:57 PM
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