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Sylvester's gone to School

This was Crsmp5 (burnt toast) original idea, I thought I should promote it to it's own forum as it is has been so popular.

Sylvester's gone to School

Postby karmann eclectric » Wed Nov 25, 2015 3:26 pm

More detailed writings are posted at
So far, we've rehabbed the brakes. Getting the vacuum pump running again was a big difference in stopping power! The vacuum switch had failed, but I had one in my parts stash. Y'all know that all restoration work takes twice as long, and with a class of 16 year-olds, that is at least doubled! Yesterday we replaced the failed dc-dc converter and got the vacuum pump running. Today we started fitting a vacuum accumulator, tested an alternative vane-style vacuum pump (much quieter), and figured out how the vacuum switch works. Decipering the original wiring is a challenge, but this harness is pretty much un-hacked, so I want to keep it that way. We ran new wires for the dc-dc in order to relocate it.

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Re: Sylvester's gone to School

Postby karmann eclectric » Tue Jan 19, 2016 3:18 pm

More on my blog, but we have fairly well gutted the electrics. Final battery count keeps rising, as I now have 24 Valence U-27XP to play with from two donors.
11 if these Group 27 batteries will fit in the main tray since we finished cutting out some the center partitions (Weakens the tray, but weight is reduced by more than one third from the Lead-acid pack. Looks like two batteries will fit in each of the unused body cavities ahead of the rear wheels, and two each under the seats, if we choose. Add up to five batteries in the motor compartment, and the count stands at 24. This would give the truck a 39.9 kWh pack weighing only 1056 lbs. That should be good for up to 200 miles at low speed around town, or no less than 114 miles on the highway!
Battery placement is still being decided, and we may use fewer batteries to keep is simple and safe.
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Re: Sylvester's gone to School

Postby luckham » Thu Jan 21, 2016 1:12 am

I redistributed my batteries to improve driving.
I had four in a box behind the rear axle, a space that does not exist in the Kurbwatt.
I moved two to the engine compartment (total 8 + 1 house) and added the remaining two to the center tray area(total 10).

This has balanced the vehicle out much better, the front wheels are much more positively attached to the ground, it was too easy to lay rubber before.
Entertaining but not practical. One of these days I need to measure the actual tire loads to see how its balanced compared to original specs.
batteries with straps.jpg
Battery tray
batteries with straps.jpg (53.99 KiB) Viewed 11246 times

Lead acid 108 volts @ 25 KW(new) 1150lb these are old batteries my range is maybe 25 miles which is plenty for my needs.
While I was moving batteries around I also swapped out the hard welding cable wires to braided straps this has significantly improved my battery connections and reduced loosening of the batter post nuts due to vibration and strain.
Load some picture either here or on your blog of the battery install
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Battery balance

Postby karmann eclectric » Thu Jan 28, 2016 7:16 pm

Indeed- I've got a lot to decide on weight distribution, since a second set of 12 Valence UXP-27 has been procured for this project. The 'final' plan is to use 20 of our 12V 130 Ah batteries, arranged in two strings of ten. That 120V nominal setup keeps it safer with the high school mechanics, but the pack could be switched into a 240V series setup for adult activities... Rounding the capacity of each battery down to 1.5 kWh yields a minimum total capacity of 30 KWh. That's on par with the newest LEAF!
In the Kurbwatt, there are large voids below the cargo floor in front of the rear wheels. They're large enough for three of these batteries, but only two can fit behind the driver unless we re-route the main pack cables. In addition to these five, there's room for two batteries placed on end below each seat. That's nine or ten batteries added down low and between the axles! We could stuff up to fourteen in the main battery tray by placing some on end (that 12" height barely clears the rear door opening, and the first two rows of batteries would be about 1/2" too tall if set on end- striking a floor beam). There's also room to place four batteries on end between the bumper and the battery tray box, in a new fixed tray that bolts to the bumper mounts and would not have to be removed when servicing the pack (but pull the four batteries it carries). Alternatively, the tray could be rebuilt longer to accommodate two more. As our goal is only 20 batteries, I'm inclined to leave off that four-pack and set the final battery up front in the motor bay. It may necessitate using a different battery than the Valence for our 12V house loads, but that's one of the easiest compromises of all.

Btw, good 'ol Motion Industries helped me find replacement tray rollers for only $13 apiece after exhaustive online searching. Turns out that Grumman used an 11/16" Hex bore bearing normally used on conveyors. They're rated at 800 lbs apiece and the tray has eight of 'em, but they get a lot of side loading, and several of the originals were completely blown out... ... d.jpg?dl=0
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