Just called up the local battery place and checked out what they had for deep cycles. They have the following available:

Group 24 - 85 Ah - $80
Group 27 - 95 Ah - $86
Group 31 - 105 Ah - $100

I had used 70 Ah as the capacity for a group 24 battery. Looks like they have a bit more than I had thought. Good for another few minutes of run time at least. However, it looks like the group 27 is the best bang for your buck.

Edit:

I also called up another place. They said they could get me a group 27 battery rated at 105 Ah for $92.

This is great. Can't wait to see you mow the lawn.

Last night, Ben Nelson came over and was kind enough to bring a few batteries with him. These are the same batteries he is using in his electro metro. They are 100Ah gel cell batteries. They are not exactly in the greatest condition, but they have to be better than the starting batteries I was using. Testing should commence this weekend!

http://ecorenovator.org/pictures/ecorider052.JPG

I did another round of testing tonight with the new batteries.

The first test was just with two of them, so another 24V test. This confirmed the ~50A draw while mowing. It also confirmed that 24V is just not enough power to mow the lawn. The mower slowed way down and also the blades weren't spinning fast enough to cut the grass very well.

Here is the 24V setup. The new batteries are quite a bit larger (and heavier!) than my starting batteries. I used quite a bit of strapping to keep them in place just to be safe. I think Ben said they each weigh around 70 lbs.

http://ecorenovator.org/pictures/ecorider053.JPG



Here you can see the size of these batteries compared to the multimeter.
http://ecorenovator.org/pictures/ecorider054.JPG



After the 24V test assured me that it wasn't enough voltage, I strapped another battery to the front to do the 36V test. Yeah, the 2x4s make it look funky, but I needed to get them up so they'd clear a linkage for the mowing deck. I also kinda like the cool bayonet styling it has going on. :)

This test was much more successful. At first I had the mowing deck belt slip on me (mmm, burning rubber smell), but with a quick adjustment of the linkage that was fixed. The pulleys are still oversized for 36V, so this will still need to be fixed. However, at 36V the mower happily chugged along at a good speed in 1st gear mowing the grass. It was pulling 50-60A from what I could guess. The needle bounces around quite a bit unfortunately. Perhaps a digital gauge would be a better idea.

Here is the setup.

http://ecorenovator.org/pictures/ecorider055.JPG

Hey, you've got room on those 2x4's for at LEAST 2 more batteries!

Speaking of bearings...
 

Go back to the bearing place after you pull your front wheels off, and see if they have any bearings that will fit in place of the bushings that are already there. The bushings just pop out, they're not press-fit, but packed bearings will allow them to spin more freely... might be worth a couple amps draw, but definitely worth not having to grease them every 10-15 hours.

You should also check/replace the fluid in the transaxle. It's probably 40 years old, and should have been replaced around 100 hours.

Thanks for the tip on the bushings. I'll check that out.

The transmission reportedly had problems and was rebuilt not too horribly long ago. The previous owner said it randomly pops out of gear. However, I haven't had this problem yet.

Hey Tim,

Your mower is starting to look like early versions of the Electro-Metro, when it had lots of wood supports in it!

The Group 31 Gel batteries are a little wide too fit in cross-wise in the Elec-Trak. Since your mower doesn't really have a front end on it, that might not be an issue for you.

I do assume you will do something more classy than 2x4s when you are all done! :rolleyes:

This weekend me and my wife took our dog out for a little hiking trip. On the way over to the trail, I saw my exact mower for sale on the side of the road, and right next to it was a snow blower attachment! I was quite excited to find one for my exact model of mower. So, we turned around and I did end up picking it up later that day. Maybe I'm getting ahead of myself, but I just couldn't pass up the opportunity. I'm very exited to have this. My driveway isn't exactly short. :)


http://ecorenovator.org/pictures/ecorider056.JPG

http://ecorenovator.org/pictures/ecorider057.JPG

Wow. Nice find.

Winter is going to be tough on your batteries. I suggest: long extension cords.