PDA

View Full Version : why is my battery getting hot?


losi24
12-25-2005, 03:35 AM
well, i got my GWS BN-2 going today. it was too foggy to fly so i decided to run a battery pack to test thrust and whatnot. i have a GWS ICS-480 15A ESC running the two 300H motors swinging 5040 props. i am also running 3 servos. i am only seeing about 3 minutes of 3/4 throttle. also i smelled something burning after the LVC kicked in and took the battery pack out. the shrink wrap is melted off. not just a little melted, i mean melted off of half of the battery. i could hardly hold the battery. i thought it was because of the battery. it is a 9.6V 750mAh GWS Ni-MH. i also have a 8.4V battery of the same chemistry and size. i tried the 8.4V battery and it still got pretty warm after about 1 minute of run time. why is this happening? am i pulling too many amps? in the manual all it recommends is a ICS-100 or a ICS-300 ESC. thanks for any and all help!

rcnerd
12-25-2005, 03:52 AM
It's not the esc....I think the 480 is up to the task, and the esc doesn't play a role in current draw...it either handles the demand or it doesn't. The 750 gws batt is aaa's right? These batteries are great and a good value but they don't like currents which drain them faster than about 10 minutes. I'd say your'e probably in the 'hood of 15 amps, since the batt is 750 mahs, 7.5 amps would be "10C" (10 times capacity, 1/10th of an hour (six min) runtime), and 15 amps would be 20C or three minutes. I would say 8C is a good max for the aaa nimhs.
Better options for batteries might be 2/3 a batts, which are shorter and fatter, and range from 500 mahs (nicad) to 1100 mah nimhs. Also nicad aa's can be quite good for the price, or maybe 4/5 aa batts. nicads can handle higher current than nimh, and shorter fatter batteries can handle higher current than tall skinnies.

What type of batt is reccomended?

losi24
12-25-2005, 04:04 AM
it recommends a 6 cell 400-600mAh Ni-Cd or a 7 cell 500-800 Ni-MH. so i need a new battery? would it hurt to use this 8.4V?

losi24
12-25-2005, 04:06 AM
the Electrifly 8 cell 1100mAh 2/3A pack is only about 20 bux at my LHS. i may have to grab one.

rcnerd
12-25-2005, 04:27 AM
it recommends a 6 cell 400-600mAh Ni-Cd or a 7 cell 500-800 Ni-MH. so i need a new battery? would it hurt to use this 8.4V?

if by "hurt" you mean melting than yes, probably....:D


that 1100 2/3 a pack sounds more appropriate....

also consider that leaving the plane on the ground tethered and running at a constant throttle position may pull more current than actual flying for a couple of reasons....

meatball
12-25-2005, 03:26 PM
Do not use AA batteries with the current draw of two engines. Im sure you'll have absolutely no problem if you get a KAN 2/3 650 or 950 pack (or electrifly 1100 2/3). These batteries have much more room to let out current, and it wont heat up as much.

A good analogy I read somewhere on these boards (someone can take credit) is a clown car. The AA batteries are like 15 clowns in a volkswagon. The 2/3 cells (or KAN) are like 15 clowns in a city bus. If theres a bomb in the car and the bus, the clowns in the volkswagon are going to fit and punch eachother and try to squeeze out of the car, where as on the bus, they can file out in an orderly fashion.

Also, on www.foamyfactory.com (http://www.foamyfactory.com) in the building guide, he states that using the GWS-300 the AA Sanyo cells are fine, but moving up a little bit to the GWS-350C, you need the 2/3 KAN's. Theres no doubt that those two motors need as much or more current then the GWS-350C

qban_flyer
12-25-2005, 04:48 PM
the shrink wrap is melted off. not just a little melted, i mean melted off of half of the battery. why is this happening? am i pulling too many amps? in the manual all it recommends is a ICS-100 or a ICS-300 ESC. thanks for any and all help!

That melted pack is toasts, losi. Those AAA cells are not large enough to handle two 300s.

They can barely handle one, let alone two.:eek:

hoppy
12-26-2005, 12:40 AM
The 300H with 5030 (Not 5040) props draws 8.5A at 9.6V and 7.5A at 8.4V. The 5040 would draw even more:( Doubling those numbers for the two motors would yield 15 to 17A. This is in excess of the capability of the batteries you have mentioned. A pack of 2/3A KAN 1050mah would work.

GWS recommends a 4025 with the 9.6V battery. http://www.gws.com.tw/english/product/powersystem/edp300h.htm

I'm at a loss as to why they would recommend a 800mah NiMH pack. Maybe I'm missing somehting?

Matt Kirsch
12-26-2005, 01:16 AM
Depends on who recommended it... A LHS owner might not have known better and was only trying to be helpful. If it was GWS... I'd have to wonder myself.

hoppy
12-26-2005, 03:06 AM
It is GWS recommendation.:(
http://www.gws.com.tw/english/product/airfly/bn2.htm

rcnerd
12-26-2005, 05:12 AM
Do not use AA batteries with the current draw of two engines. Im sure you'll have absolutely no problem if you get a KAN 2/3 650 or 950 pack (or electrifly 1100 2/3). These batteries have much more room to let out current, and it wont heat up as much.

A good analogy I read somewhere on these boards (someone can take credit) is a clown car. The AA batteries are like 15 clowns in a volkswagon. The 2/3 cells (or KAN) are like 15 clowns in a city bus. If theres a bomb in the car and the bus, the clowns in the volkswagon are going to fit and punch eachother and try to squeeze out of the car, where as on the bus, they can file out in an orderly fashion.

Also, on www.foamyfactory.com (http://www.foamyfactory.com) in the building guide, he states that using the GWS-300 the AA Sanyo cells are fine, but moving up a little bit to the GWS-350C, you need the 2/3 KAN's. Theres no doubt that those two motors need as much or more current then the GWS-350C

-he is using two *motors* not engines.;)

-AA's will be fine...if they are Japanese Sanyo or Panasonic Nicads. You are right though, A's would be better...especially if it's a nimh pack.

You'd be pretty amazed at the current handling ability of a AA nicad... Although 17A cont is a little much...but an actual flight would likely be more dynamic than a continuous load. I'm a huge believer in AA nicads...they can be found for SO cheap....Balsa products had a bunch of 7 and 8 cell nicad packs in the clearance section of their site for under $2...PER PACK!!! I bought 4 7 cell 150 mah nicads for $1 each...LOL! As well, liquidation or surplus places often are good sources for SUPER cheap nicads...make sure they are sanyos or panasonic if you need them to last. The cheaper, chinese nicads are hit and miss...I've found some that rival the Sanyos and others that hold only 200 mahs new even though they are supposed to be 700's.

qban_flyer
12-26-2005, 05:20 AM
-he is using two *motors* not engines.;)

-AA's will be fine...if they are Japanese Sanyo or Panasonic Nicads. You are right though, A's would be better...especially if it's a nimh pack.

You'd be pretty amazed at the current handling ability of a AA nicad... Although 17A cont is a little much...but an actual flight would likely be more dynamic than a continuous load. I'm a huge believer in AA nicads...they can be found for SO cheap.....

I used to fly a GRAUPNER Speed 600 on eight cell 1000 mil Sanyo AA NiCad packs pulling in excess of 17 amps. swinging an 8X4 propeller direct drive. AA packs in the BN-2 will make that model too heavy, and in all probability, unflyable!

Packs are still around and are as good today as they were back in 2001.:)