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.

I got a chance to do some mowing with the mower finally! I still haven't resized the pulleys, but it does work great as is. The deck is spinning a bit fast yet and it really shoots the grass out pretty far. It had no problem cutting through ~6 inches of grass!

I had to do all the cutting in 1st gear as 2nd is still too fast. I did notice that when the deck is engaged and you're actually cutting grass, the mower does slow down. So, 1st gear is no longer as fast as I'd like to do actual mowing. So, I will still be resizing the pulleys, but I have a much better feel for how much to resize them now.

Oh yes, I got video this time too. :)

YouTube - EcoRider In Action


Finally happy Darin?

Nice video!

It doesn't seem that slow. No slower than a push mower anyway. Was that first gear?

You can really see the force of the air coming out the discharge chute.

Yup, the cutting was done in 1st gear. I did try 2nd and it was pretty fast for mowing.

I love the fact that the mower has full moon hubcaps on the back tires. Very AERO!

I would complain that I would like my Elec-Trak to go a little faster.

Guess that's the difference in gearing between a stock manufactured mower and trying to build one yourself.

Those batteries look like they hold up OK?

The batteries really don't last too long. Once I load them up off of a fresh charge the voltage plummets down to around 35.5V. However, they did last longer last night then they did the other time I had it out. I don't know how long these have been sitting. Perhaps a little exercise will be good for them.

It's alive!

Are those actually moonies on the wheels, or are they weights?

I think they're just moonies. I haven't tried to take them off though.

If you can pick up the assend of the tractor, they're not weights. The smallest weights I know of are 35# per wheel, and most are 55# and higher. I can pick up the rear end of most tractors to about hip height, but if they've got weights, I can only get one tire off the ground.

Good story. I'm new here but like what I see so far!

How do you know when you reach 50% depth of discharge? If you got a hour run time while only taking the batteries down 50% that would be great!

-Ryan

Hello and welcome to ER beem0!

You can monitor battery pack voltage to know when you've gotten down to 50% dod (depth of discharge). Right now, I've just been using a voltmeter across all the batteries. I plan on using an individual LED battery monitor (3 bar graphs basically) very similar to this. A guy from the local electric car club has designed a similar unit and will be making a batch of them.

I've been going over my battery choices and I think I am going to settle on three group 31 12V batteries. These won't give me the run time I really want, but the more I think about it, the less I want to lug around six 6v batteries. The mower is already heavy enough with Ben's three gel cells on it. I don't even want to think about three more batteries of that size. Plus, I have to mount them all too. The group 31 will be rated a tiny bit over 100Ah and give me about a half hour of run time to 50% dod. This is acceptable. I also looked at the numbers, and assuming I used the mower once a week and ran the batteries down to 100% dod, I would still get roughly 11 years out of them. If I went down to 50% dod, I would get 22 y ears. I'd have to double check that though. So, going to 100% dod, and my 1 hour of run time is possible for a hit to the life of the batteries.

I actually have built up a Simplicity to be electric. I'm very happy with it, but just struggling with knowing if I'm hurting the batteries and also charging them correctly. What voltage levels do you go down to for 50% DOD? Under load or no load?

I'd recommend some batteries in the back for increased traction and less steering effort. I'm running 48V and have two in front and two in back.

Ah, great! Perhaps you could start a thread that explains your conversion. I know I'd be very interested. :)

Anyway, for a DOD chart, I would use this (found here).
http://ecorenovator.org/forum/attach...1&d=1253138604

So, if you're measuring a 48V system, 42V would be your absolute minimum you'd ever want to go. 50% dod would be down to 48.2V.

If you are using unbalanced batteries, you really want a meter like the link I posted before that monitors each battery. However, if your batteries are pretty well matched, you can just use a regular voltmeter.

Great website. I've seen similar tables, but where I stuggle is the load vs no load (aka open circuit) question. When I start the motor, the voltage will drop say from 12.7 to 12.2 yet the bats should be fully charged. It would be nice to know the state of charge while mowing, but seems to be difficult. I think I might just measure the no-load voltage after mowing for a half hour. If it is at say 50% I will use the loaded voltage measurement i had at that half hour time as a cut off.

I have a hydrostic tranmission, so I'm probably pulling more current then you. I went with Interstate SRM-29's. They are very heavy, but two in front and two in back I can't even tell. I think it actually handles better then stock and definatly has better traction!

Thanks,
Ryan

Unfortunately, you do check your battery voltage for SOC under load. The point being, you never want the voltage to sag under 10.5V or you risk damaging them. The voltage sag really does tend to screw things up when you're putting a big load on the batteries though.

Voltage really isn't the best way of measuring SOC though. The only way to really know is to use a specific gravity tester (which only works on flooded batteries), but thats just not practical while you're using the mower.


I did look up your batteries and they don't have an Ah rating on them. I would double check and make sure that they aren't a hybrid battery (aka marine starter). They are a mix between a starting battery and a true deep cycle battery. Marine starting batteries aren't built for constant deep cycling like full blown deep cycle battery is and definitly won't last as long.

Oh man, I hope these are true deep cycles. Interstate told me these are what can use and have a rating of 126Ah (using 20 hr method). I was looking at AGM and Gel, but went with just these flooded lead-acid for cost. These seem to work good, ran a half hour mowing and no signs of slowing. I have a 6000W motor.....can't even slow it down going up hill. I pull around 70amps mowing at a good speed, and can hit up to 120amps going up hill. I really need to find a way to lower the current draw.....that is my next task after fully understanding the batteries!

Thanks for the help!

Well, if they are rated for 126Ah they're likely true deep cycles, and if they recommended them for your application I'd be even more sure. That is also a really high rating for a 12V battery.

I will be taking your advise about positioning the batteries in the back side (at least two of them). With the batteries as they are in the pictures I do sometimes have some problems with traction. However, I think that mainly stems from the mower's ability to turn pretty sharply. It even turns far enough to wedge the front tire under the front foot rests.

I went and bought a hydrometer and it shows my batteries are in better shape then what the voltage measurements reflect. Based on that I mowed for about 30-40 minutes and only went down about 50% DOD. I think that is pretty good!

Wow, thats great news. Sounds like you got yourself some great batteries there. I might have to look into getting some of those. :)

I'm now trying to understand how much life I can get out of them. I read you can get anywhere from 300-500 cycles out of deep cycle bats, but is that over a certain amount of time? I mean if I mow my lawn 30 times a year, does that mean i can get 10+ years out of them?!?! That is hard to believe, but would be awesome!

I think that might be close to possible. The guy I called up last week said the batteries he pulls out of floor cleaners are about seven years old. If proper maintenance is kept up on them, I don't see why you should expect anything less.

Any more progress on your tractor? The grass isn't growing much now, but I have a plow I'm going to put on for fall/winter task. I think it will work great, but we will see how the bats perform in the cooler weather.....

Not much lately. I've just been calling around to get prices on batteries.

I've been wondering about the colder weather thing, as well... My father has a few spare tractors and we've got 3-5 HP 110AC motors that we could use for a conversion, I just wonder how the batteries would fare in the cold weather, and if we'd need to store it indoors.

I just assumed that it wouldn't need to be stored indoors as long as it was left on a trickle (1 amp motor cycle charger) while not in use.

Well, I just ordered the batteries! I ended up going with three 150Ah group 31 size 12V. This should give me a fair amount of capacity and were pretty reasonably priced at $94 each.

Wow, 150Ah! You should get some good run time! Which brand? I'd be interested in knowing more about them.

Thats exactly what I thought when his secretary said 150Ah. I had to speak with him directly to verify. This weekend I talked with one of the more battery wise members of the local EV club and he explained things to me. What happens is they can use more plates in the battery to get the amp hours up. However, this means that the plates must be made thinner. This effectively shortens the overall battery life (how many cycles you get out of them). He suggested that since I went with these batteries that I really try hard to not bring them down below 50% DOD to maintain long battery life. He had suggested Trojan T1275s to begin with since they use a much thicker plate and they can hold up to more cycles. However, those batteries cost upwards of $180 and I wasn't willing to dump $540 in batteries on my first EV project.

I also haven't heard anything from the battery supplier. I'll be giving them a call today to see what the status of the batteries is. I returned Ben Nelson's gel cells this weekend, so I have nothing to run the mower with at the moment. I'd really love to get the battery racks made and get everything bolted down so I can finish up this project.

Yes!!! Been a while since I posted, but I had to brag on this...

Took my restored E15 Elec-Trak for its first drive, today! Took a couple laps around the back yard before parking it in the trailer. I couldn't believe how little current it used. D1 only used 20-30 amps at max. throttle depending on terrain, and D2 only used 30-40. Now kicking in the field weakening really caused a surge (up to 100 amps) briefly, and a HUGE surge in speed! Good thing it is a smooth adjustable resistance. I don't think I'll be using it that much - D2 at full throttle is just fine (about the same as 4th gear on my old Dynamark)!

Don't know how much total energy it will use, I bet it takes more than 2.5 cents per mow, but it still WAY better than the old ICE mower.

I was impressed that it stopped well even without using the brake, and maintained a nice steady speed even going downhill. It behaves a lot like the ICE tractor did in this manner. Guess that's typical for a shunt wound motor.

Now I have the space in the garage to work on the caster arrangments for the deck, which is all that is left to do before I can mow...WITHOUT hearing protection! The biggest adjustment is going to be the front mounted deck. When I sat on the tractor it finally hit home how much bigger this is than the old ICE mower. To top it off, the deck will be about 6 feet in front of me.

I put together an online restoration diary to document all this, since it might help somebody. The address is:

http://www.davesevs.com/E15restoration/E15 home page.htm

It isn't linked from my main EV page or home page yet, so if you go there, you have to use the back button to get back to it. And it isn't complete, but it is done up to installation of the hood, and that was only a week ago. I'll get the rest up in a few days.

(...and this time it is in regular HTML format )

The batteries finally came in. Apparently they're not a common item this time of year or something. Anyway, my wife picked them up yesterday morning and they are sitting in the garage now. I would really love to get them hooked up, but I don't really see that happening with the work that needs to be done before the in laws get here this weekend to do work on the garage. We'll see though. I would love to make the last cut of the lawn this year with the mower!

As stated, I'm not going to get to work on the mower until sometime next week. So, I figured I'd at least get a shot of the batteries for ya. They are monsters.

http://ecorenovator.org/pictures/ecorider058.JPG

I took a little time this morning and made an EValbum page for the mower.

This weekend I'm hoping to be able to make the battery racks for it. The in laws took back the push mower of theirs we were using for the past year when they came down to do the garage work. I still need to get the grass cut at least once more this year because it is looooooong.