Unsure about li po charging

[easypickingsere]

Hi all, just bought my first real life heli on saturday and been reading articles on this forum for some time so finally joined up for your expert help.

Heli I went for is a mini pred 3d, now I dont want a discussion on how appropriate or how good/bad this heli is, just need advice on charging.

Ive flown on clearview rc simulator for hours now and can manage with the blade cp-kn to fly around and very rarely crash, explained to the guy in my local shop this and he said with care this heli might well be ok aslong as i do take care not to push things too quick. (getting a coax for in the house regardless)

Being new to the whole Li Po scene I have been alarmed at potential hazards with these cells over old nicads. The charger supplied with the heli has a dial which ranges from 0.3A round to 1.2A. I understand that 1A is what to charge on, but I am unsure where on this dial I should set to charge to achieve this. Bat is a 3 cell 11.1V by art-tech (supplied within package) 0.3 is postioned at 2 o'clock on dial and 1.2 at 10 o'clock. Any help will be greatfully appreciated.

[David Drew]

It depends on what capacity the lipo is.

If it is,say, 800mah then charge at 0.8 A. If 1200 mah then 1.2A, 1800 mah = 1.8A.

This is known as 1C, that is, charging at a rate that would replace the whole capacity in 1 hour.

On a 1200 mah batt, charging at 2.4A would be 2C. 3.6A would be 3C and so on.

Normally we charge at 1C. Some people charge at 2C or above, esp the better packs, but this is recognised as shortening the life of a batt.

So, for the moment stick to 1C or less, and never leave a charging batt alone. They can catch fire if things go wrong.

In reality, if you only discharge to the recommended 80% (20%) left in the pack, charging at 1C will take less than an hour.

David

[easypickingsere]

Many thanks for the quick reply!. Looking on the batt it states it is 1300mah and 11.1V am I to assume from your info that setting charger to max (1.2) will be fine for this type of cell?

Will be charging on an extension lead out side the door after seeing the videos on the net lol.

[David Drew]

Yes, 1.2 will be fine.

If you want to, put it in an oven dish or similar. TBH, it is very rare for a batt to catch fire. Normally it has been knacked by the user first and they are trying to push charge into a knacked batt.

2 other things. If you fully charge a lipo, store it in the warm as it will go overcharge if cooled down below about 10 deg, or charge to about 50% and store at that. A knacked batt will puff up and swell.

Never had one do it to me mind you. But many have.

Also, try to balance charge every few cycles. Balance chargers are not really expensive, or you can buy a V Balancer for use with a normal charger.

David

[easypickingsere]

Nice one thank you very much for clearing that up for me been paranoid about doing first charge! The supplied charger is a balance charger so I take it all is good and just to keep using that.

Weather permiting going to take it on its maiden flight/crash on the weekend is it ok to charge li po and immediately go out to the rec' and fly without fear of problems?

[David Drew]

Yes, just keep it warm till right up to flying

[easypickingsere]

Great stuff thank you very much for your help really set my mind at ease, hovering it hasnt worried me as much as charging the batts and burning down our flat. Looking forward to good weather

[DIJ]

A couple of points worth a mention, is that unlike nicads, lipos don't self discharge very much, so you don't usually need to give them a top up charge if they have been sitting for a couple of weeks.
Also, don't make the mistake of over discharging lipo's when flying, as thats the quickest way to kill them.

[easypickingsere]

Good point on the topping up, am familier with this through power tools (builder), will just practice my hovering until i notice a drop in power then land and disconnect. Thank you once again for both of your imput, really glad this site exists or may of found my life long interest in rc heli's short lived

[DIJ]

No problem, and I hope it goes well. If you're undeceided about which coax you want then may I suggest you check out the Blade mCX

[163phil]

Hi matey and welcome to the forum.

If you're concerned about charging LiPo batteries, try this: http://www.fast-lad.co.uk/store/lipo...80-p-4111.html

Should put your mind at rest

[David Drew]

will just practice my hovering until i notice a drop in power then land and disconnect. found my life long

Too late then I'm afraid, the lipo is struggling. You will damage it.

If you have a meter on the charger do it like this.

Hover for 4 mins on a full batt.
Recharge and take note of the amount you put back in.

For a 1000 mah batt, you do not want to go below 20% left in the batt, so you are working towards dischargeing to 20%, 80% used.

If after 4 mins it takes 400 mah to top back up you have used 40%, so you can then fly for 8 mins to get down to 80% used, 20% left.

You are using 100 mah per min. So 8 mins.

If it takes 500 mah to recharge you are using 125mah per min, so 800 / 125 =6.4 mins etc etc.

You will soon know what to set your Tx timer to and keep your discharges above 20%. As yourflying changes, so will your consumption.
Hope this is clear!!

David

[cjcj1949]

Some times the supplied batteries aren't very good. You can tell how good they are by how warm they feel after a flight. If they are hot rather than warm then you can make them last longer by only using half of the capacity. You don't need to be afraid of lipos so long as you follow the instructions. Most of the problems were caused by people using the wrong program. With a balancing charger with no options you should be ok. Lipo charging absorbs heat and the battery should get cooler. It's a good idea to measure the individual cells after charging. You can buy little meters to plug into the balance connector for about £5 and also you can get various checkers for use in flight.
Lipos are getting better all the time, but as fast as they get better we expect more from them.

[easypickingsere]

Great! thanks once again for all of your advice on this, will go out and purchase a meter for checking batts and will do the checks on the amounts used.