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Electric scooter problem

This may be off the range of what you allow, and if so delete it and I apologize.

I have an Ego electric scooter, sit down, a long established company, two sealed(very sealed, no way to get inside) 12 volt batteries connected together for 24 volts.

I am not on my third set of new batteries. here is what happens: by the way, neither the dealer nor the company can diagnose it:

With a new, already charged set I get full range and full power for about 3 to 5 weeks, but the more I charge it, or use it, the less range and power I get.

The front battery will mostly always read 13.4 volts, but the rear battery, while starting out with same voltage, eventually drops to 10.4 or so.

It’s always the rear battery. The wires are good, replaced, all that is fine, the dealer says the charger and controller are fine.

The only thing I can see is that the rear battery is against the motor, and the motor gets hot.

Is this the problem? Can I solve it with an asbestos shield between? Or any other ideas.

I had an old one for four years and eventually it did this, I put in two new sets, second set free from dealer, but it did the same thing.

Now, I bought a new one, and now, 2 months into it, it is starting to do the same thing.

ideas? off topic for your site, and if so, delete this.

Chapel Hill

Sorry, in line 4, I meant to say, I am NOW, on my third set…

and sorry one more time, for a typo, but at the bottom of original submission, I mean: "Now I bought a NEW ONE, and I mean, an entirely new eGo scooter. And also, could it house current problem? my current reads a relatively steady 120 volts, but jumps up and down on the digital meter sometimes, from 116-122, rapidly, as fast as the readout can print them, but usually it’s steady.

Make sure that those two batteries are matched in amp-hour ratings. Put a 10 amp-hour battery in series with a 12 amp-hour battery and the smaller (10 amp-hour) battery will go dead first and if you keep trying to milk that last minute of use out of the scooter, the battery that dies first becomes reverse charged.
This is a sure fire way to ruin batteries.

Deep cycling is death to batteries. Most golf courses aim for a 50% depth of discharge for the most cost effective use of batteries in golf carts.

Next time you are in the hardware store or near Radio Shack, pick up a cheap analog multimeter with an old fashioned meter. You’ll find it much easier to read and therefore more informative.

Digital meters are new, and advanced, and shiny and display a lot of digits. But they are poorly suited to applications where voltages or currents are not rock steady. Wrong tool for this (and most in my experience) home and automotive voltage/current measuring needs.

Interesting problem. First thing to determine is whether other people have this problem, and for that, the Internet is your friend. Fire up Google or Altavista or whatever and search for discussions of this. Amongst the wealth of guesses and misinformation, you may find that some smart and talented folks have looked into what is going on and maybe even have some answers.

Assuming that the two batteries are identical, you could keep monitoring your battery voltage until the rear battery starts to show signs of deterioration – down to 12.4 volts say – then swap the batteries and see what happens next. You’ll possibly learn something, It’s not entirely clear what.

It’s certainly not impossible that motor heat is killing your batteries. Insulation probably won’t hurt and might help. You could tuck a temperature probe from Radio Shack or down between the rear battery and the motor and see how warm it is down there.

Good Luck

How about rotating the batteries so the one now in back is moved to the front? Let’s see how that works.

BTW I would expect heat to have impact if that motor gets hot enough. It also could be due to a high resistance connection on one batter and not the other.

I own one of the first 10 EGo’s made. The problem is two batteries in series won’t automatically stay in balance. After awhile one gets undercharged and the other overcharged. It helps if they are periodically charged separately with a 12V charger. There is a device called a Powercheq you can attach to actively keep them balanced. ANother approach, the one I take, is to bring out the center connection to a separate jack and use 2 12V chargers. There are a few companies that make a 2 channel charger.

Here’s a shot of me on my electric bike and my wife on the EGo:
http://mysite.verizon.net/tbrown59/jpg/ride_on.jpg

Good reply-sounds like NO.2 isnt getting a full charge-Kevin

Deep discharging most types of batteries (Ni-Cads don’t mind deep discharge) quickly destroys them. Limit the discharge to 1/2 capacity and they will last MUCH longer. HEAT is every batteries enemy. Don’t let them EVER get hot…

Your batteries are probably AGM or Gel-Cell lead-acid type. How many Amp-Hours are they rated for? (how big are they)?

You probably have 12 cells, 6 in each battery. ONE of those cells will be a little weaker than the rest. That’s just the way it is with batteries. If you ride your scooter until the voltage starts to drop, say down to 18 or 20 volts, that weak cell is completely dead and is being reverse-charged by the remaining cells. That will DESTROY that cell and ruin the battery…

It’s two 12V 34-35AH size ‘U1’ batteries in series. They are a popular size in electric wheelchairs. Normally the cells inside each battery are well matched, but the two batteries are not matched to each other. Even if the discharge is not very deep, during charge one battery fills before the other and gets chronic overcharging.

Vibration is also death to batteries. Make sure that your battery is not being excessively vibrated or shocked (not in an electrical sense) when going over bumps. Is the motor jarring against the battery when the tires go over a bump?

Poor current controller. The batteries are at the limit. The current control is the way to save them. The battery will die if the current is allowed to exceed the capacity of the battery. I also posted this elsewhere. Sorry but the manufacturer of your scooter does not support the failure of this controller. ‘Fact’ motors are hard inductive sources when they start under load. This triples the instantaneous current they need to start moving. The current controller is the only part of the system to protect the batteries from being cooked. And thats all folks, you cant get ther from here.

On the recharge issue the problem is most likely that too much current is being supplied. A slower charger though means less satisfied customers. Charging a battery too fast is almost worse than draining too fast. The manufacturer of these systems is cutting corners on design. The symptoms from these scooters relates to abuse of design. For both charge and discharge. Were any of these scooters provided by medicare? If so I would ask whether these providers a just sucking up medicare money.

Make sure you are using deep discharge batteries designed for the kind of service they are getting.

I’m sorry euryale1 but you’re off the track here. The eGo has a high quality 180 amp motor controller and it’s not the problem. You’re guessing at what’s going on, but I own one of the things and I’ve taken measurements. Please read my post above and here:
http://community.cartalk.com/posts/list/2129679.page#2641510

It uses sealed lead acid AGM batteries which are similar to “gell cell”. They’re designed for deep discharge.

http://www.batterystore.com/Powersonic/PS12350.html