HELP: battery capacity too big for charger?

[DBJ]

Hello,

I'm hoping someone can please help me with what is probably a very easy problem:

I needed new batteries for my chair and was hoping to get just 50 Ah ones but all the store had were the more expensive 80 Ah ones. It was much more than I needed but I bought them anyway, brought them home, hooked them up and just as I was about to attach the charger I noticed that the front of the charger indicates "for rechargeable batteries 28-60 Ah". "Oh no, I have 80's!" I looked on the back of the charger and amongst all the caution and danger warnings it also indicated:
"Caution: This battery charger is for use only with 12 cell (24 volt) 28-60 amp-hour, gel cell batteries. Other types of batteries may burst causing personal injury and damage" They seem pretty serious about warning me that I shouldn't use it for my batteries. Now I'm in a bind because I can't return the batteries (it had single lead posts which had to be drilled to mount the fuse).

What will happen if I use this charger on my chair/batteries? Do I need to buy a new charger?
The old batteries had no Amp-hour rating on them so I don't know if they were also 80's, but I suspect they were substantially less.

My chair is: Invacare Storm Arrow MKIV
Old batteries: "MediChair MK Deep Cycle" part # 8G24
New batteries: Haze 80 Ah, Group 24 Deep Cycle Gel
Charger: Invacare model: BAT-GC0811, 24 volt, 3.8 Amp.

Any advice you could offer would be greatly appreciated!

Dave
Vancouver, BC

[Burgerman]

Your old batteries were very high quality group 24 73Ah gel batteries.
Your new batteries are low quality and could likely be AGM and not gel, and are a direct replacement. They wont last as long, And will give about the same range.

The charger is designed for gel batteries. You now have AGM. The capacity is not important.

It will charge them, without danger, but isnt ideal since its a few tenths of a volt lower than really needed.

I have to add that a 3.8 amp charger wasnt big enough for your old or new batteries. To replace say 60Ah takes about 24 hours with that charger. Even if it tells you its charged earlier.

Buy an 8 amp soneil 3 stage modern charger asap.

[DBJ]

Wow- thanks for reply and great info! I'm loving this site already.

I made a mistake in my post- it was the charger's INPUT power that was 3.8 amps (at 110 volts). The OUTPUT is actually 8 amps.
I'm a bit upset to hear that my battery is AGM because the salesperson specifically stated that they were NOT the AGM type but were gel batteries. And they were a bit pricey ($220 each). He told me that these were designed for wheelchairs and were the replacement I needed.

After reading your post, I pulled one out of the battery box and it contains the below wording. Please let me know if any of this information changes anything. Now I'm a bit worried that I have the wrong batteries.

Haze Marine Gel
Code # HZY-MR12-80

TTorque= 5.7 NM
CZ0 hr= 80 Ah
VEOD = 1.7 VPC
CCA SAE = 425 amps
MCA SAE = 600 AMPS
VCYCLIC = 2.35-2.4 VPC
Temp = 20-25 deg C
Advanced VRLA Technology
Microporous Polymer Separator
Thixotropic Gelled Electrolyte

[Burgerman]

Useful info.

Yes its gel.
Your charger should be fine.

It is a pretty low current battery, high resistance, so will not give the torque or "power" your originals did, and frankly you wont get the cycle life that the MK would have provided either. But then they seem cheaper too. At least compared to UK prices.

[Burgerman]

http://www.europa-batteries.com/documen ... _EN_v2.pdf

Your batteries.

These give around 285 cycles when deeply cycled to 75 percent, as we do in a powerchair, compared to 500+ for the MK ones at 80 percent that you removed - so these will live just over half as long before replacement.

The starting amps for eg give an idea of FULLY CHARGED power when you want some amps fast (say climbing a curb, turning on thick carpet). My Odyssey 68Ah batteries give for eg over 1000 amps, compared to these at 425.

What this means to you as a wheelchair user is that they feel more "discharged" long before they actually are under use as voltage sags under load.

[DBJ]

Awesome- thanks so much for the info, Burgerman. I appreciate your help.
I'm stuck with these batteries now, but I guess I learned a lesson about trusting that store next time.

Thanks again,

Dave

[Burgerman]

For future reference, for normal people in normal use, just buy the biggest MK gel or Sonnenschien gel that you can get in.

If you are abnormal and want more power and do sport, off road etc buy Odyssey.

And forget the rest no mater how much you save.