Positive earth battery maintainer/charger

I asked a friend in the charger business if he could modify one of his products for me for use on positive ground systems. If there's any interest in this here, I can probably get him to do a few more. The difference is that the 2-pin SAE output connector has the polarity reversed, so you can hook a permanent mount pigtail to your battery and have the exposed terminal be positive. Too much risk of accidental fireworks with a normal polarity pigtail.

Stu

I used* a regular battery tender on mine, with the pigtail. Yup, I let it touch the frame once, blew a fuse instantly but no other harm. Lesson learned. It's now zip tied to the frame in a way that makes it hard for the exposed terminal to touch unless you really try, and I keep the little rubber cap on when not in use. No problems since.


* Until I recently put in a "LiPo" battery, which doesn't need charging - 1-2% loss of capacity PER YEAR of sitting - and (this is the real attraction in my mind) weighs a few ounces.

BrianK, how are you handling charging the lipo. And what type of lipo are you using? They are pretty cheap from hobbyking. And would be an awesome solution. thanks

I got mine from Jim Ong d/b/a Maviryk Design - http://www.mavirykdesign.com/default.html. Jim is or was an EE grad student doing this to put himself through school. He may have graduated by now - didn't have the website when I dealt with him.

I haven't been charging it at all. Per Jim, they really don't need it unless they somehow become discharged. They can sit a long time without discharging much. He's got some FAQs on his website, and there's a lot of "learning" out there in other bike forums. The big boys in this arena are Speed Cell and another one I don't remember. Apparently a couple of former friends, now bitter competitors, run the big two companies. Lot of dirty linen in the forums. I ran across Jim when he posted in one of these threads, took a flyer and ordered from him, and was pleased with his responsiveness and with the product.

I put in a four cell, figured it's all I need with kick-only start. Has been great. Took out a big heavy conventional battery and replaced it with the four cell (just saw on Jim's site it weighs 0.8 pounr - I'd have guessed it was even less.

Happy with the purchase and will be replacing the batteries in my other bikes with Jim's LiPo batteries when they need it.

They are not LiPo batteries, they are A123 cells. There is a big difference in how the two are charged and handled. I use alot of lipos in my rc stuff. I can fly a 6 pound helicopter for 8 minutes on 2000mah at 22.2vdc. Great capacity and light weight. The a123 cells are what several people are using in real car and motorcycle projects for pure electric power. I'ts a nice option insteas of heavy conventional batteries, plus the raw amp output is staggering.

BrianK said:

I used* a regular battery tender on mine, with the pigtail. Yup, I let it touch the frame once, blew a fuse instantly but no other harm. Lesson learned. It's now zip tied to the frame in a way that makes it hard for the exposed terminal to touch unless you really try, and I keep the little rubber cap on when not in use. No problems since.

Click to expand...

I hear ya. But this bike is a customer's. And I don't want a call on Sunday afternoon telling me the bike is dead, and can I come fix it? This'll hopefully eliminate that problem.

Stu