a088008

I currently charge my 1100 Mah NiMH battery at 1.25C, but have heard of people charging at 2C.

Does a higher charge current mean more power (within the limits of the battery of course)?

A specific question: Would charging my battery pack at, say, 0.1C give me less power than 1.25C and should I consider 2C charge current?

-Q.

Tom Smith

My Feedback: (1)

The battery can hold only as much as it is designed to hold. The charge rate simply determines how soon it gets charged to it's maximun allowed capacity. A slow rate is best because all the cells get evened out and charged equally. Fast charging , if one cell is lower than the rest, will peak before the low cell is up to snuff, giving you shorter flights. I slow charge my packs every couple of month to even out the cells. Try 2c and see if the pack gets hot. If it only gets warm, then you are probably OK. If it gets hot, then reduce the charge rate. Heat is the enemy of any cell. Tom

a088008

My pack gets fairly warm on 1.25C, so I think I'm not going to try any higher rate. I generally charge at night, so I'll slow charge from now on.

Thanks for the advice.

-Q.

HitecRedneck

I wouldn't charge it any faster than 1.5 C If it get hot that's one thing but if it gets warm that ok.

a088008

I charged my pack at 0.2C last night and then flew it today.

There was not much power and I just managed to land the beast before power dropped below stall speed.

I'm wondering if the charger did not "false" peak. If not, it's back to my old 1.25C charge rate.

-Q.

Steve Lewin

How long did it take to charge ? That always gives you a good hint. If it wasn't around 5 hours then it didn't get a full charge.

Personally I never use peak chargers at less the C/2 and it's worth being aware that many of them have a time cut-off that prevents them from charging long enough for a full charge at low rate e.g. my little CG340 cuts off after 2 hrs. Time to check the charger manual ?

Steve

a088008

I did not keep track of the time. I usually commit the start time of the charge to memory, but I could not remeber it this time.

I'll check the manual, but as far as I know there is only a 90 minute trickle charge cutoff.

-Q.

hoppyfl

Most manufacturers recommend 1C as the "best" charge rate that puts the maximum charge into the battery with the least damage to the battery and the best delta V for the charger to detect.
hoppy

Cougar-RCU

My Feedback: (2)

I have a stupid Question for you guys.
What does 2C and 2/C and 1.25 C mean>?
When I use my charger? my LED screen
has 0.3A while charging... is this where I would
change that reading to 2.0 A ??
Thats
Jeff

NCC-1701

C is the capacity of the battery.

NiMH cells have a higher internal resistance than NiCads. This will cause them to heat and damage the cells if charged too quickly.

Cougar-RCU

My Feedback: (2)

Ok. I have a 1200 Mh nimh battery. what shoud the setting be then>?
thanks
Jeff

BillK

If you want to charge at 1C you set your charger to 1.2 amps and it will take it 1 hour to charge. 2C would be 2.4 amps and take 30 minutes to charge.

Cougar-RCU

My Feedback: (2)

I think you have made it clear to me now. thank you
so just for the heck of it. 2C a 2400 mah pack would be
2.4 amps? So this is also the same method for nicads as well?
thank you very much
Jeff

Cougar-RCU

My Feedback: (2)

The same numbers in discharging as well?

hoppyfl

As a rule, NiMH should be charged at 1C and NiCd at 2C.
Charging NiMH above 1C may damage the cells depending on brand and size.

Discharging?? On the bench I use 2C or about.

hoppy

Steve Lewin

C is the one hour rate. It is the same number as the capacity of the pack
.
So C for a 2400mAh pack is 2400mA which is the same as 2.4A

2C for a 2400mAh pack will be 2 x 2.4A = 4.8A

2C for 600mAh pack will be 2 x 600mA = 1200mA or 1.2A

etc.

The value of C does not change whether it's NiCd or NiMH or some other type of battery but the rate at which you can safely charge does.

Steve

Cougar-RCU

My Feedback: (2)

Thank you very much.. sorry for being so stupid on this stuff
I am trying to learn my screens on my new charger. (triton)
and the book seems to think that I understand it all *LOL*
The only other question I had was at the top upper right
It reads out mah like a count up or down.. what is that
telling me?
Thanks
Jeff

Flying Fish

Being new to e flight I would just like to clarify on what has been discussed to this point.
Most recommended Nimh charge rates should be 1c and
Nicad rates should be 2c.

If i charge my 8 cell 720 mah pack at 1c it would be .72 A
and a charge time of about 45 minutes.

Is this correct??

Thanks,
Brian

a088008

Almost.

Charging at 1C for 1 hour at 720ma would fully charge your battery.

Think of the charge rate as water flowing into a bucket.
The bucket has a certain capacity, so the faster the flow the faster the backet fills up.

Now 1C means that a certain flow rate will fill the bucket in 1 hour. Therefore 720 ma charge rate for 1 hour = 720 mah which is how the battery capacity is measured.

-Q.

Steve Lewin

Very close but charging is not 100% efficient. In effect some of the energy going in is "wasted" driving the chemistry that charges the battery. So in fact if your battery was completely flat it would take approximately 1.2 hours at a C rate to fully charge it. Putting it simply, if you expect to get 720mAh out of a battery you always have to put more than that in.

But anyway rates that high should only ever be used with peak detecting chargers so the charger will decide when the battery is full. Since you rarely start off with a completely flat battery it could take almost any time up to about 1.2 hours.

Steve

bobbdd

Can you tell me what the Delta peak v. is ? On the Brain it has settings for 5,10,20,30,40,50 Dv. Someone said use 10 Dv for NiMh and 20 Dv for NiCd,is this correct I am still confused about what Delta Peak is.


Thanks

hoppyfl

Look at the application manual for NiMH. The section for charging will explain everything. Read the whole manual and you too can become an expert.
hoppy

http://data.energizer.com/datasheets/frames.htm

bobbdd

Your right but that's alot of reading.I guess I'l get started.