Last weekend I decided to dust off my EVT 4000 and set about getting it back on the road. It's been sitting idle for a couple years under utilized. I might want to sell it but even if I do the first step will be to make sure it's running well again.
The last time I rode it the top speed was under 20 miles/hr .. very weak, for a bike that easily gets to 30 miles/hr with good batteries in it. Also I'd noticed some white powder in the bottom of the battery compartment. Also it had sat without being put on a charger for several months. That was last year some time and I must admit to having not done anything about it since, not even putting it on the charger.
Over the weekend I pulled the batteries out. This bike has four 12v50ah SLA batteries (Genesis) and a fifth battery (12v18ah) because it has a turbo mod where the fifth battery can be switched into the system giving a total 60v system.
The 50ah batteries look okay but one of them has some white powder and there's a bit of powder in the compartment. But it's not terribly bad. Also the compartment has some peeling paint and rust. It's been sitting outside for a long time but with a scooter cover over it. These batteries each read 12.8v or so. Obviously they're suffering from "sulfation" leading to the weak performance.
The 12v18ah battery however is in much worse condition. I didn't take a voltage reading but the swollen case tells the story of a dead battery. It took a lot of grunting to get it out of the place EMS had wedged it into.
As a test I installed a string of 4x 12v18ah batteries that I have sitting around and took the bike on the road. It easily hit 30 miles per hour and was a lot of fun to ride. Oh yeah, that's why I bought that scooter, it's fun to ride! In any case the important thing to note is the prior poor performance wasn't because of the bike - but because of the batteries that are obviously in sad condition.
My first thought is to see about reconditioning the existing battery pack. If that fails I might get a LiFePO4 pack but there is this consideration about selling the bike. Do I want to put a lot of $$'s into a bike I'll just be selling? Maybe not. Anyway..
Took a look around - there are two products which claim to desulfate batteries in this condition. "Battery Life Saver" and "PulseTech". FWIW At the EAA Silicon Valley meeting a couple months ago someone gave a presentation on these and showed that they do improve battery life.
Both of them appear to have the same use/design idea. They come in voltage ratings of 12v, 24v, 36v, etc and are connected across a battery or battery pack. The unit self powers off the battery and does some kind of square wave signal across the battery. Reading between the lines the square wave signal has to be at the right frequency to resonate the sulfation crystals such that the crystals break up and are reabsorbed into the electrolyte.
I've ordered a 12v Battery Life Saver. They recommend one usage is to go through several cycles of charging, and discharging, with the BLS connected across the battery. I'm thinking to connect the 12v50ah batteries in parallel, with a charger and the BLS, then maybe put it on a timer such that every day there is one charging period followed by the rest of the day on a discharge.