Lipo fire! Toasted Blackjack!

[xletts]

Hi guys, I have had my BJ for about a month, used it several times but the last time my Lipos exploded!!! You should have seen the fire! It looks like the cost to fix my BJ (toasted ESC, batteries, radio box, repaint, etc) will be more than the cost for one of those new UL-1 hydros. What do you reckon? Fix the BJ or get the UL-1?

NB: Those of you who are running 6Cell lipos on the standard BJ - be very afraid!

[Ub Hauled]

Get the hydro...
sorry for your loss, but you saw that coming, didn't you?

[xletts]

Ha, now that I know more about these things...I can see I SHOULD have seen it coming! I miss read the spec that said 7.4v lipo 3600 mah 20 c or better to mean MORE IS BETTER! So went for 2 x 11.1v 2200 mah 25c - result = KABOOM! Others on the forum say they are running 6cells without a problem - any one care to chime in and tell me what I have done wrong??? Unlucky or stupid?

NB: I even bought the ESC programmer and set it to "lipo"

[JimClark]

I need to read better. Better go back to elementary school

post deleted

[kookie_guy]

any pics?

[Fluid]

... Others on the forum say they are running 6cells without a problem - any one care to chime in and tell me what I have done wrong??? Unlucky or stupid?....

Anyone can say anything on the Internet.....I suspect that if they ran 6S they used enough battery, didn't do it for long, or if they did they used a small prop. The primary cause (other than using 6S) was that your packs were clearly underpowered - they only accept a 55 amp draw while the manufacturer suggested 72 amps minimum - so they overheated, couldn't supply enough power to the ESC, the ESC burned up from the ripple current and shorted the cells......

Sorry about the damage, glad it didn't happen in your home. Don't make the same mistakes on your next boat. Like Jan I can recommend the UL-1.


.

[xletts]

The primary cause (other than using 6S) was that your packs were clearly underpowered - they only accept a 55 amp draw while the manufacturer suggested 72 amps minimum - so they overheated, couldn't supply enough power to the ESC, the ESC burned up from the ripple current and shorted the cells......

.

Can you explain how you got to this? I DONT want to make the same mistakes on my next boat so totally want to get the right batteries! Thanks!

[xletts]

any pics?

Yeah, I'll put some up soon for you - good for a laugh at least

[Meniscus]

any pics?

LOL! short and to the point!

[kookie_guy]

Can you explain how you got to this? I DONT want to make the same mistakes on my next boat so totally want to get the right batteries! Thanks!

you were using 2200 mah packs, rated at 25c.

discharge rate = mah x c rating / 1000
= 2200 x 25 / 1000
= 55 amps

To use 25c packs at the min 72 amps required you would need....

72 = Y x 25 / 1000
Y = 72 / 25 * 1000
Y = 2880 mah packs

Personally, I am going with 4900mah packs rated at 20C, 30C burst. So I will be able to give 98 amps / 147 amps burst. hope that helps

[xletts]

Thanks, that helps alot. I had no idea that the minimum amp draw was so important...the manufacturers only seem to bang on about the maximum does this have anything to do with the motor you use also or is it just ESC v's Battery?

[Doby]

With LiPos,,,get the highest "C" rating you can afford.

[kookie_guy]

Thanks, that helps alot. I had no idea that the minimum amp draw was so important...the manufacturers only seem to bang on about the maximum does this have anything to do with the motor you use also or is it just ESC v's Battery?

the max they talk about is the safe current the ESC will provide. The current draw is determined strictly by the motor and the load applied to the motor. For example, if you were to do a bench test, you would see a motor draw a certain amount of current (amps). If you were to put a load on the motor by trying to stop the shaft with your fingers (don't try that) the current would go up, because it's taking more effort (current) to spin that motor.

So if you are using a bigger prop than stock, you are putting more load on the motor, which means the current draw will go up.

[AndyKunz]

Fix the BJ or get the UL-1?

Get a Miss Elam.

Andy

[Meniscus]

Or a Miss Vegas if you want to do the conversion. Many think that the Vegas is a better hull, but like anything else, it's up for debate. LOL!