stashu

Just getting my H9 Mini Pulse plane ready. This is my first E-plane, and I just bought my first Li-Po battery last night. TP2070 Extreme was the type and brand. I have been skiming the post here and am somewhat confused on the dangers of the batteries. Gasoline is dangerous too but if used properly it is safe. Anyway I have many question on the Li-Po's.
Does anybody have a site or article or a Li-Po's for dummies article?. Questions like are they dangerous just sitting there, or just during charging, what does a 9 volt cutoff mean and why. Can I put my plane on a holding pipe on the ground and run it till the batteries quit as to get a idea of flite time, or will the batteries get too hot?-what amp can I safetly charge at for speed or for a longer lasting battery. Questions like these

Thanks for any help

Stash

Fliprob17

I was a little worried when I first jumped to LiPo's, but if you take care of them, there is really very little to worry about. They are most dangerous/likely to flare up when being charged or discharged, not so much just sitting there. The 9 volt cut-off is for a 3 cell LiPo, is equates to 3.0 volts per cell. That is pretty much the standard per cell number for LiPo's. So a 2 cell LiPo would be 6.0 volts, etc.. I would not recommend running an entire battery with the plane on the ground. You need proper air flow to keep the motor and ESC cool, the battery will not heat up too much, but the motor and ESC will. As far as charging, a 1C rate is the max. to safely charge LiPo's. So in your case, using 2070mah, take the 2070mah and divide by 1000 to get amps = 2.070 then multiply by 1 for the C rating = 2.070 amps. That would be the max. If you want extended battery life you want to be somewhere around a 75% of the 1C rate. so 2.070 x 0.75 = 1.55 amps.

GravityWorks

hello there, to give you an idea of how dangerous these batteries are, here is a story for you.
I baught my first lipo battery, a 3e 1800mah 3 cell 11.1 volt, I used a cheap wall charger and flew it til the motor would not lift my heli anymore. Then one day while charging i noticed that the battery was "puffy" on one side so I took it off the charger and put it outside to cool off. I went inside and got a glass of milk and came back outside to check the battery, as I reached down to grab it, the battery caught fire right in front of me, and before I knew it the whole thing was engulfed in flames and it looked like a road flare on one side, shooting flames out 12 inches from the batery. Man that sucked.
Anyway I have had manny bateries since then and have learned how to take care of them. here are a few tips.

1. BUY A GOOD CHARGER, a balance charger that utilizes the balance plug.
2. check the voltage often, with a multimeter, check each cell seperatly you can do this from the balance plug. there are 4 wires on the plug the left 2 are one cell, the right 2 are another cell, and the 2 in the center are the third cell ( I mean the 2 in the middle leaving 1 on each side for a total of 4 wires) see below.
3. Never let any cell get below 2.9 volts... EVER. and never let any cel charge above 4.25 volts MAX.
4. even though you have one battery, treat it like 3 seperate batteries (if you have a 3 cell) each cell is seperate and must be treated as such.
5. If you dont own one, buy a ceramic pot. (cooking pot) and charge the battery inside of it, the ceramic pot is fire proof and will contain any amount of explosion from a lipo battery. (safty first)
6. get a low voltage indicator, they can be purchaces for less than 15.00 and will alert you, via a very bright L.E.D. when the volts drop below 3.1 volts on any cell, they are invaluable because it is very hard to tell how much flight time you have left.

balance plug diagram for checking each cell.

1 2 3
/ \/ \/ \
l__l__l__l
l_______l
I hope this helps you out. if you dont "get" any of this or need more help let me know.

Cheesehopper

I know all about the 1c charge rate and stuff, but how long should I charge it for? (11.1v 1050mah Li-Po)

jdetray

A lipo is fully charged when each cell reaches 4.2V. A proper lipo charger will stop charging when the pack is fully charged, so you do not have to time it.

If you charge at the 1C rate, charging any size lipo pack will take a bit more than 1 hour. In theory, charging a fully depleted pack at 1C would take exactly 1 hour. But since charging is never 100% efficient, it will take somewhat more than an hour.

If you charge at 0.5C, it will take a little more than 2 hours. At 0.25C, it will take a little more than 4 hours, etc.

- Jeff

Prophex

Not to make a new topic about it, but I've recently bought the Multiplex LN-5014 Multicharger (you can find all the info on http://www.multiplexusa.com/ ), to charge my flight packs and a LiPo battery pack. However, the manual doesn't say anything about how much current you need to run through your batteries in order to charge them ... (I can choose anything between 0.1A - 5A)

Then I found [link=http://www.yourzagi.com/batterybasics.htm]this[/link] webpage which explained a bit about charging currents. As I understand it, you need to charge your battery with the same amount of mah as the pack has. So say a 4-cell 800mah NiCd pack, would be charged for 1 hour at 0.8A; a 2-cell 1500mah LiPo pack, would be charged at 1.5A for 1 hour and so on ... Is this correct ?

In short: How do you calculate the charging current of a NiMH, NiCd, LiPo and LiIon pack ? (and what's the difference between a fast charge and a normal charge ?)

Fliprob17

Battery Example: 2100mah 3 cell 11.1 volt LiPo - You take the mah rating and divide by 1000 to get amps = 2.1 amps, then multiply that by the C rating (typically 1C) = 2.1 amps x 1C = 2.1 amps - that would be a max. charge rate. To be safe and extend your battery life, stick to something around a 75% of the 1C rate, so 2.1 amps x 0.75 = 1.58 amps.

Prophex

Does this also apply to NiCd and NiMH batteries or only to LiPo's ?

Fliprob17

I only use that for LiPo's. The NiMh's that I use don't cost that much, so I charge them at a higher rate. But really, for anything, the lower the charge rate, the less stress on the battery.