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Battery FAQ
Battery Application Chart


Listed below may be more than you ever wanted to know about batteries for mobility vehicles.  I guess I'm one of those guys that when you ask what time it is, I tell you how to build a watch...  Nevertheless, the following are questions that our guys get asked about batteries and their use in scooters and power wheelchairs:   

1) What are the common symptoms of battery problems?

If your scooter or power chair has one of these symptoms, replacing the batteries may well solve the problem:

"It doesn't have the power it used to have..."
"When I start off, it runs for a few feet and stops..."
"When I plug it in to charge it, it never stops charging..."
"When I turn it hard to one side, it shuts off..."
"I charge it overnight, but the gauge on the handle still is in the red..."

2) Why do you recommend AGM batteries over GEL cell?

First, let's talk about the similarities in the two.  Both are maintenance free, require no water to be added, and can be mounted in any position.  Both use lead plates and similar chemistries for charging.  Both are acceptable for unrestricted travel.  The differences start in manufacturing.  Gel batteries have lead plated with traditional leaf separators between cells.  Silicates are added to the liquid electrolyte allowing it to become gelled.  AGM, is a product that uses a process where the lead plates have a separator made from an absorbent glass mat (hence its name), permitting 100% of the electrolyte to be captivated and soaked into this material.

This AGM technology creates a dramatically improved cycle life and offers a lower cost per cycle for the end user.  In fact, today's better AGM batteries now nearly double the cycle life of Gel batteries.  Also, the Gel battery normally takes 10-20 cycles of use before it starts to perform at its rated capacity; whereas the AGM reaches 95-100% capacity from the start.

The bottom line, without the 14 letter words is this:  High quality AGM batteries are cheaper to buy initially, and last through more cycles (discharge and recharge) than comparable quality Gel cell batteries.  Seems like a "no-brainer" to me!

3) If AGM is better, as you say, why don't we hear more them than we do about Gel cells?

Part of the deal is the cost; Gel cells typically cost more, and many people believe that more expensive equals better quality.   I really believe that if AGM batteries cost more, they would be used more.  The other reason is that Gel cells were the first type of maintenance free batteries that came on the market, replacing the old "wet acid" type batteries first used on electric wheelchairs.  No doubt, they were a great improvement over those dinosaurs, but AGM is quietly taking over the mobility market.

4) Should I charge my scooter every time I use it?  Won't that wear it out quicker?

This probably is the biggest misconception out there among scooter users.  Many people believe that the battery needs to be completely dead before it should be charged.  Others think it will "wear out" the batteries to charge them "over and over".  Let's look at this by using one of the battery industry terms, DOD (depth of discharge).  This means the amount of power discharged from the battery before it is charged again.  Batteries should be able to perform about 800 cycles at 60% DOD.  However, if the depth of discharge is only 30%, the number of cycles would more than double to an estimated 1,800 cycles.

Simply put, if you charge the batteries before they get down so low, they will last much longer than if you wait until they get low, or if you let them sit for days without recharging.  Here in our Nashville shop, if a customer comes in complaining that their batteries only lasted a year or 18 months, when we start asking questions, in nearly every instance, they were not charging the scooter for days or weeks at a time.  They didn't use it that often, and they didn't think of charging it between times. 

There is a lady here that works in inventory control in a warehouse in downtown Nashville.  She uses her scooter 6-7 hours a day during work, then loads it up every night and uses it at home.  She charges it, religiously, every night.  Even with all this use, she is going on her 5th year with the last set of batteries we sold her.  The more you use them, and the more you recharge them, the better for the batteries, and the longer they will last!

5) The batteries are supposed to be "maintenance free"; does that mean I don't have to do anything?

Pretty much.  I would check the terminal connections every so often, especially if run time seems to be diminishing.  Loose connections can add resistance to the charge input, and result in low charge.  Also, check the battery temperature by feeling the battery sides.  They should be slightly warm while charging; if they are hot to the touch, stop charging and have the batteries checked.  Also, look for "bulging" in the batteries (where the case swells severely).. A certain amount of bulging is OK, especially in larger batteries, but severe bulges signify a blocked valve, and should be immediately taken out of service.

Don't "baby" new AGM batteries when it comes to initial use.  AGM batteries come to you at nearly 100% capacity, and require no preconditioning (Gel battery manufacturers suggest an initial conditioning time of the first 5-10 cycles before the battery is deeply discharged - Universal Battery AGM batteries do not require that type of special care).

6) I had my batteries checked, and one of them is much worse than the other; do I have to replace both of them?

Normally, you should replace the set.  If one battery is bad, chances are the other one is not far behind, especially if they are several years old.  Placing a new battery in series with one that is half used up will result in much reduced service life of the new battery.  In effect, "the old one will drag the new one down".  The only exception is if a battery goes out within the first 6 months of service, and you have been charging them regularly, the one bad battery can typically be changed without causing a problem to the set.

7) Do I need to vary the times that I charge my batteries?  I've heard that batteries have a "memory"...

The only batteries that had a "memory" were the older ni-cad (nickel-cadmium) batteries that were in use several years ago.  Today's modern sealed lead acid batteries have no such memory.  The only thing you need to think about is to charge the scooter after each use, and to charge at least twice a week if you don't use the scooter very often.

8) Shouldn't I just leave the batteries on charge all the time, then?

That probably won't hurt the batteries themselves, although it might be a little "overkill".  I wouldn't suggest that, though, because although the batteries would be OK in that situation, it surely wouldn't help the charger you are using, and replacing the charger can be quite expensive.  Just keep the batteries charged each time you use the scooter or wheelchair, and charge it every few days if it is not being used.  Probably the easiest way to do that is to plug in the charger at bedtime, and unplug it the next morning. 


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