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All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> 'Suggested' charge and discharge rates
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'Suggested' charge and discharge rates - 12/10/2004 7:04:53 AM   
JasonWilliam


 

Posts: 161
Joined: 10/18/2004
From: Pleasanton, CA, USA
Status: offline 		Hello all. Is there some universal suggested charge / discharge rate table I can reference? Or rather is this something specific to the battery make/model/current state? I'm trying to figure out how quickly I can charge my batteries, and am not having much luck.

For example, my 700mAh 9.2v pack took 50 or so minutes at a charge rate of 1.5mAh. However, my 1300mAh 1.2v wants to take over 70 mins at 1000mAh (anything over this supplies too much voltage to the cell and shuts down my Duramax Ice).

Basically, how do I know what is a safe rate to charge my bats at? What is a safe rate to discharge them? I'm only talking NiCd and NiMH...

A couple other random questions: should I cycle charge my bats every time? What is meant by Peak Charge? And last but not least, what do you use for a power supply to your field charger? Right now, I'm using my starter battery... I have a feeling this is a less that ideal choice.

Thanks for your time guys!

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RE: 'Suggested' charge and discharge rates - 12/10/2004 3:44:53 PM   
pettit



Posts: 2138
Joined: 12/19/2001
From: Durham, NC, USA
Status: offline 		(Red, back me up please, or correct me if I'm way off base)

Roughly speaking, the battery capacity (say 700 maH) divided by 10 (C/10) is the overnight charge rate. 16 hours worth. Charge the 700 pack at 70 milliamps overnight.

Quick charge is C/5. Charge the 700 at 140 milliamps until the charger stops charging.

Fast charge is C/1. Charge the 700 at 700 milliamps, but not too often.

The 1300 maH battery, C/10 = 130 milliamps overnight, C/5 at 260 milliamps until the charger stops charging.

You only need to discharge your batteries every month or so. Check and note the capacity your cycler gives you. Then when you see a degradation in capacity, think seriously about replacing that battery.

A peak charger monitors the voltage on the battery as it is charging. Basically when the voltage stops increasing or slightly starts to decrease, the charger stops charging because the battery is fully charged. I think your charger does that.

Somewhere around here (Reds Battery Clinic) is a conversion for a PC power supply to run any 12 voly charger. They're cheap and can put out close to 10 amps.

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(in reply to JasonWilliam)
       Post #: 2

RE: 'Suggested' charge and discharge rates - 12/10/2004 4:12:11 PM   
JasonWilliam


 

Posts: 161
Joined: 10/18/2004
From: Pleasanton, CA, USA
Status: offline 		Great info Pettit, thanks! A couple follow up questions:

-Your charging formulas seems to indicate you never want to charge beyond 1C. I've seen folks doing so (2C, even saw a 3C) at the field. Basically, they pumped as much jucie into the thing as they could, without taking the voltage beyond the threshold of the bat. Is this not a good practice?

-Take my single sell 1.2v glo plug ignitor battery: it wont take a charge amp of anything over 1000mAh, even though its a 1300mAh bat. The stated error is an over voltage situation, and the charger shuts down. Does this indicate I've got a bad battery?

-Regarding discharging: I understand that its a good idea to note the capacities across various discharges. But, at what rate can I discharge it? Is there some rule of thumb (1C, 2C ect...). Is there some C not to exceed?

-I'm looking into a PC power supply for home use. Is there anything wrong with using your starter battery (12v, 7.2A) at the field? I just want to make sure I'm not damaging my starter bat, my charger and my charing bats.

Thanks again!

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(in reply to pettit)
       Post #: 3

RE: 'Suggested' charge and discharge rates - 12/10/2004 4:36:24 PM   
Rodney



Posts: 4782
Joined: 12/8/2001
From: FL
Status: offline 		While some companys may have other limits, the general limits are 1C max for NiMh and 2C max for NiCad batteries if you want maximum life. If you exceed those ratings, expect reduced lifetime and possible catastrophic failures. Both NiCad and NiMh benefit by a so called formation cycle or two when first put into service or after an extended storage period, that's the 0.1C charge for 16 to 20 hours, it may require three cycles of this to get maximum output from your battery. It may even help to discharge each cell down to 0.9 volts under a C/5 load prior to the formation cycle.

(in reply to JasonWilliam)
       Post #: 4

RE: 'Suggested' charge and discharge rates - 1/24/2005 1:30:49 AM   
broter


 

Posts: 4
Joined: 1/14/2005
From: Vashon Island, WA, USA
Status: offline 		Thanks for the helpful thread.
What rate would you use for routine discharging for NiCad nad NiMH.
Thanks.

(in reply to Rodney)
       Post #: 5

RE: 'Suggested' charge and discharge rates - 1/25/2005 3:37:34 PM   
Geistware



Posts: 12946
Joined: 4/9/2002
From: Locust Grove, GA, USA
Status: offline 		I do something a little different. I know that my setup has an average discharge rate of 1.8 amps. I know this is from measuring my capacity removed over time. With this said, I always cycle or discharge may packs at 0.9 amps (I run two packs) This lets me know what my discharge or average flying time is for the real world. I have only been doing this for 2 years but I have over 600 successful and one unsuccessful flight over that time.

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(in reply to broter)
       Post #: 6

RE: 'Suggested' charge and discharge rates - 1/25/2005 3:55:46 PM   
JasonWilliam


 

Posts: 161
Joined: 10/18/2004
From: Pleasanton, CA, USA
Status: offline 		Geistware, are you indicating that .9amps is drawn during flight? I assume you're talking about an Rx battery? What about a Tx battery?

Thanks!
-J

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Develop your choice of intentionality.

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       Post #: 7

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