PDA

View Full Version : Charge/Discharge Rates


Programmers
2008.06.04, 11:10 AM
I am assuming if I have a 1000mah batter and I charge it at 1000ma it will be quickly charged? I'm completely new to manually programming my charger and am interested in this. I've found some good resources, such as battery university and three racing blogs but none answer my questions. Does it go without saying? I dunno. Here's my questions...

Generally, for a good slow charge - what rate should I charge a 900/1000mah AAA battery at?

For a good discharge - what discharge rate would I discharge the above battery at?

For an accurate analysis of my battery - what would be the recommended charge and discharge rate?

- Does speed make a difference here or would a quick analysis be as accurate as a slow one?

I would really really appreciate some advice here. :)

Tom.

schmenzer
2008.06.04, 11:51 AM
What charger are you using?

If you had a totally dead 1000mAh battery and charged at 1000mAh it would take an hour to fully put back in those 1000mAh. This is called 1C charging and is good for our NiMh batteries. Of course a battery is never totally dead but if you discharge you batteries after use you will be pretty close.

For a slow charge use 1/10th C or 100mAh.

Ideally, for discharge you would approximate the actual use of the battery in the car. Chargers that have an automatic discharge/charge cycle typically discharge at 1/2 the charge rate so 500mAh for a 1000mAh charge but this is not always true. Dedicated dischargers like the PN Racing AAA Discharger discharge at 1 Amp. This is more like what our cars use and is better than auto settings on chargers.

Just as important as discharge rate is the low voltage cutoff for the cell. If you are going to recharge right away .7 is good. If you are going to discharge and store batteries .9 is better.

Greg

Programmers
2008.06.04, 11:55 AM
I have the MaHa MH-C9000...

I don't think I can choose my amps for the analysis or can I?

mk2kompressor
2008.06.04, 12:46 PM
for testing,
discharge @1c(1c of 1000mah batt)
charge @.5c

slow charge i do .5c(100 is best for break in)
fast charge 1.5c
i peak before the race with 2c

based on the duracell 1000mah i use:)

Spoon
2008.06.04, 01:53 PM
I have the MaHa MH-C9000...

I don't think I can choose my amps for the analysis or can I?

Yes you can. The instructions go through the methods for setting the charging current for all of the modes.

This probably repeats some of the information that you've found but I tried to compile as much as I could here.

http://blog.128racing.com/2007/01/battery-care.html

Programmers
2008.06.04, 06:04 PM
for testing,
discharge @1c(1c of 1000mah batt)
charge @.5c

slow charge i do .5c(100 is best for break in)
fast charge 1.5c
i peak before the race with 2c

based on the duracell 1000mah i use:)
That was just the sort answer I was after, thanks!

Yes you can. The instructions go through the methods for setting the charging current for all of the modes.

This probably repeats some of the information that you've found but I tried to compile as much as I could here.

http://blog.128racing.com/2007/01/battery-care.html
That post is fantastic. I've previously linked it 1/2 times from here. Very useful and how I treat my batteries now is based around what I learned on that! :cool:

Cheers for the instruction book advice - I'm a dummy for not reading it in the first place. I was gonna ask how I work out a C but there's a chapter on it... :o

Cheers guys!

R1WURKS
2008.06.08, 06:52 PM
just FYI, we have found that higher discharge rates have showed better results in testing . 3amps showing best performance so far.

mk2kompressor
2008.06.08, 07:20 PM
i go to 2a discharge on mine but the maha will only do 1a.
good to see a respected battery man on here r1wurks:D

EMU
2008.06.09, 03:16 AM
For testing,
I use 1A charge and discharge for all of my cells. Just to keep the numbers consistant between all the different types of cells that I use. I have different cells for different classes that I run. Some are better suited for low amp draw applications, and some are better for high amp draw.

My Lacrosse chargers both show higher discharge numbers than my Maha charger. Which I assume is mainly because the discharge amperage is lower. The highest I can discharge with the Lacrosse is 500mA, half of what I can with the Maha. I use the Lacrosse to cycle, and the Maha to test cells.

For cycling, I usually use 700mA charge, 350mA discharge or 500/250mA depending on the cells I am cycling. Lacrosse charger auto sets the discharge to half the charge.

When racing, I usually use my Duracell 30 minute chargers. They charge at 1.7A, which is a little high... but I really only use them to peak and repeak the cells. Not to do a complete charge. I used to use the Energizer 15 minute charger for this purpose, but after the cells started venting, and corroded the contacts on the charger, I got rid of it. I havent had any venting issues with the Duracell, Maha or Lacrosse chargers.