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some really beginner questions about charging a battery

eagle4

New member
#1
Hey guys, I'm almost finished my bloody wonder, its taking bloody ages (... get it... ;) )

anyway last night i finally hooked up the electronics and nothing seemed to work, wasn't 100% sure about the batteries in my transmitter, they work in my tv remotes but anyway, i decided to pop my battery on charge, just to make sure that part of the system was working, and its the first time I've used my charger.

This is my battery - Turnigy 500mAh 2S 20C Lipo Pack
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9187

when i plug it into my charger i dont know what amp setting to have it on. i set the charger to 7.4 volts cause thats whats written on the battery, however as it charges the volts displayed on the charger slowly increase, it got to about 7.8 after about 10 minutes of charging.

the specs say max charge rate (C) = 2. Does this mean 2 amps? what's the C for? my default the charger had itself set to 0.5 amps, would you recommend charging at this rate or as high as it can go for the battery?

My charger is Just Another Charger and i have it plugged into the mains power.
http://www.hobbyking.com/hobbyking/...harger_80W_6A_2_6S_Balance_Charger_w_PSU.html

Also, after having it charged for about 10 minutes i wanted to see if at least something worked on my system so i plugged it in, however as i went to plug it in the moment the male met the female plug there was a super tiny spark between the contacts, not sure if this is normal? I've checked thoroughly and there is no short between any of my solder joints or any frayed wires or anything like that.


Also any other tips and tricks you might know about batteries and chaging please let me know.
 
#2
the c=2 is twice the capacity of the battery c=capacity. So max rate of 1 amp is your max charge rate. Have a care though, you're battery will last much longer at a lower rate of charge. .500 mah will charge your battery in one hour from completely dead, 250 will take 2 hour (it's simple math really) but the slower practical charge will be more gentle then the hard fast route.

Also, it's a lipo pack, not a Life pack. This makes it a tad more dangerous. If abused lipos have no problem with popping and catching fire. Life's are much more stable. You could overcharge a Nicad battery too and blow that one but generally they didn't catch fire. So take your Lipo out of your transmitter, put it in a fire proof area and charge it and be present while it's on the charger.
Your charger is a balancing charger, so go ahead and use that option as well. This will keep the cells pretty close in the lifetime of the pack.
Tiny spark during reconnection. Did you have the transmitter switch on? Everything still works? I don't know what transmitter you have but I wouldn't think that it would spark lest it have circuitry on board that uses power while the transmitter is off. Perhaps it has charging circuitry of it's own inside and you just added a voltage discrepency to that circuit when re-attaching.

If all works, then continue as is but DO use the balance charging option at as slow a rate as you're willing to take. I'd do the charge in half an hour route myself as I rarely let the battery drain all the way down anyways, so it will be less then half an hour for a flight.
 

colorex

Rotor Riot!
Mentor
#3
when i plug it into my charger i dont know what amp setting to have it on. i set the charger to 7.4 volts cause thats whats written on the battery, however as it charges the volts displayed on the charger slowly increase, it got to about 7.8 after about 10 minutes of charging.
That's fine. 7.4 is just the nominal voltage of the battery. When charged it may be around 8.4 volts! So this is normal.

the specs say max charge rate (C) = 2. Does this mean 2 amps? what's the C for? my default the charger had itself set to 0.5 amps, would you recommend charging at this rate or as high as it can go for the battery?
C is not a specific measurement. It is a factor. You multiply the C rate by the big number stated on the battery to see what the maximum charge rate is. So = 2C * 0.5 Ah = 1 A maximum charge rate. Dont charge higher than 1 Amp.

Also, after having it charged for about 10 minutes i wanted to see if at least something worked on my system so i plugged it in, however as i went to plug it in the moment the male met the female plug there was a super tiny spark between the contacts, not sure if this is normal? I've checked thoroughly and there is no short between any of my solder joints or any frayed wires or anything like that.
Sparks are everywhere. Electrical switches and outlets in your house spark slightly when you turn them on or plug something in. Same for planes. Had there been a short, you would have gotten a huge spark, and maybe even some flames :)
 

eagle4

New member
#4
Thanks heaps guys,

MrClean, this battery isn't for my transmitter, its for my plane, sorry if i didn't make that terribly clear. I have the hobbyking HK65 in case you're still interested.

Why don't they explain the C rate lol, wouldnt it just be a lot easier for them to just have the max amp value?
 

Ak Flyer

Fly the wings off
Mentor
#5
Lipos all charge the same whether it's for a car plane boat or transmitter. The other guys are correct. You can charge at 1 amp. Your battery will have a charged voltage of higher than 7.4 when it's done. That's normal. If you can't read the battery or don't understand the formula it's usually safe to charge at whatever the discharge rate is. I can charge a 1000 mah pack at 1 amp or a 2200 at 2.2 amps. Higher rated batteries charge faster but at the discharge rate it usually takes about an hour no matter the size as long as your power supply is up to the task.

It's good that the guys mentioned fires. They are nasty when they go. I've never experienced this for myself but I never reuse a pack that's gone puffy. It's a good idea to get a lipo charging pack or at least charge on a fire proof surface in an open area like on a ceramic plate or brick or something.