# Building a small battery pack for jetski



## rwaudio (May 22, 2008)

powerhouse said:


> Aside from dreaming about electric cars, I enjoy riding stand up jetskis as a hobby. Well, time came to buy a new battery, since mine died, However instead of using Lead acid, I decided I might as well try to use lithium instead.
> 
> Some riders are currently using some shorai batteries, such as this one http://www.shoraipower.com/p-152-lfx14a2-bs12.aspx
> 
> ...


Is the battery normally charged by the jet ski (alternator)? I was helping work on a sea doo a few weeks ago and the battery problems were cause by a loose wire on the alternator, so I know that has one. If you are using Li-Po it won't charge very well from a normal alternator as a lead acid replacement. LiFePO4 nominal/charge voltage is much closer to lead acid when using 4 series cells to replace a "12v" battery. If the battery is only used to start the jet ski and doesn't need to run ignition or anything like that you should be just fine charging it when you park it.


----------



## powerhouse (Apr 1, 2011)

The jetski has a stator with a charging flywheel, so I suppose it does 'recharge' the battery. However, how would I charge a pack of 4 of those blue 7.4v 4amp batteries, and balance them at the same time? Would I have to connect each cell individually to the charger? What if I were to remove the small pouch cells from each battery, and solder them together to make one giant one?


----------



## T1 Terry (Jan 29, 2011)

Bugga,
I got all excited thinking someone was building an electric jet ski to get rid of the noisy smokey ICE these things use. It doesn't appear to be the case here though. Has anyone attempted this with Li cells?

T1 Terry


----------



## MN Driver (Sep 29, 2009)

T1 Terry said:


> Bugga,
> I got all excited thinking someone was building an electric jet ski to get rid of the noisy smokey ICE these things use. It doesn't appear to be the case here though. Has anyone attempted this with Li cells?
> 
> T1 Terry


There is a company that was exhibiting at the Minnesota state fair grounds as part of a "Living Green Expo" here a few months back. They had two boats, a slow lounger boat that ran off of lead-acid cells and a faster one running off of 48v 60Ah of GBS cells. Their flyer says 24mph and 2.5 hours run time but I think the 2.5 hours is with their upgraded 100Ah pack.

http://go-float.com/rx1

Seemed interesting but I'm not sure how fun 24mph is as I'd aim for 40mph or higher myself but it would be a challenge to get enough battery into something so small to have fun for a long enough time for it to be worth going out on one.


----------

