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I installed all my copper bridge plates, bussing two 35 amp slices together to make a 70 AH string, 44 in series broken into four batteries. I'll likely target 170 volts as my series charge voltage target, that should give me around 3.8 volts per cell (max is listed as 4.35 volts, a little headroom to work with while I figure out what sort of monitoring I want to do on these packs (they're clearly not designed with a cell-level BMS in mind, so it'll take some creativity.) I used no-ox-id A anti-oxidant wax on all the bridge plates, but it would make way more sense to have a future run of bridges tinned or nickel plated to avoid having to burnish all those plates.

After assembling the batteries, I paralleled them for a couple hours to let them equalize - first through a .25 ohm, 120 watt resistor, then just with clipleads (which were small enough wire that they behaved as resistors.) Finished with four batteries sitting at 40 volts each,equalized to within 0.1 volts of each other.

I've chosen to mount two of the 22-slice batteries under the hood, and two of them under the seat. With just a little bit of fiberglass modding, and some re-arranging of how many slices are in a pack (and maybe moving the coil for the throttle sensor) you could likely fit all 88 slices under the hood, but I wanted to try to design a project that would be accessible to almost anyone who is comfortable wielding a wrench. The Vicor DC-DC is mounted on a little stainless plate, along with a big heat sink which I added years ago, and I stuck that on the vehicle's left side wall (right bottom of the under hood picture.)

This layout uses the existing battery and charger cabling, and is really a drop-in replacement - I cut off six top-post crimp lugs, crimped on some two-hole 1/0 lugs in their place, and bolted everything up. There's one bus-bar jumper between the two front batteries, and one cable jumper under the seat - other than it's the cables that are already attched to the vehicle.

I'll be designing a nylon-webbing hold-down system for the batteries - there is now about 100 pounds of battery in each compartment, so there's not so much need for the metalwork that held the original 300-odd pounds of lead in each compartment. Meanwhile, the batteries seem content to sit somewhat wedged into place while I test things out.

For now, I don't have the charger in place - but there's room for my new Manzanita Micro PFC-30, or the original Zivan. (These photos don't show the front busbar bridging the two batteries, so there is actually less room than it looks like - but it'll still all fit fine. The Zivan can also fit on top of the Enerdels if someone chose to do that.)

The installation of the four batteries into the sparrow took about three hours, with lots of photo-taking in-between. Everything came up working, my e-meter said 160 volts, and I took it for a little ride up and down the block. My gut feel is that it took almost as long to remove the Optimas as it did to put in the Enerdels.

The first thing I noticed was there's no sag to the battery pack. I'm used to seeing a voltage drop-off when you draw 60 or 70 amps from the Optimas, and that drop-off increases if you draw a couple hundred amps. That's not the case here - the pack was at 160 volts, and 100 amps was provided at 159 volts on the e-meter. Combine that with a vehicle which weighs at least 400 pounds less than it did yesterday, and it's a very responsive combination. It also reminds me that these batteries will not be gentle on any kind of a short - they put out power, lots of it, and any stray metal object crossing the 156 Volt bus will be summarily turned into a ball of blue plasma. One nice thing about the terminal layout - with an odd number of slice-pairs (11 pairs per pack) the terminals come out on diagonally opposite ends of the battery, so it's very difficult to inadvertantly short out a battery - even setting it down on a metal table is OK. (But don't do that.) I am a little concerned about the stainless brake lines which run along the firewall - I have spiral-wrap and snap cover over them, but I want to add more, and fasten them to the firewall to keep them far away from the 80 volts by many, many amps that's sitting right there between the front compartment battery pack and the firewall.

I then tried a little stronger acceleration - I have the 600 Amp Raptor, with the ramped-acceleration mod, but even so I was gentle on the go pedal, not knowing quite what to expect.

At about 1/3 of the way down, the Raptor was drawing over 200 amps of 159 volts - still no sag on the pack! That's when this happened:

Yes, I broke a drive belt - which I was unable to do with the ramped acceleration modified Raptor 600 and a fresh pack of Optimas - I used to hit the 300 amp limiter when accelerating onto a highway without issues, and indeed had not broken a belt since that modification to the controller. This belt was relatively new mileage-wise (I had changed it because the old one looked ratty but hadn't broken) but was still 4 years old - so I'm going to replace it with the Gates Carbon GT belt, turn the controller limit down a bit, and see where we go from there. (Gates doesn't even make the aramid fiber belts any more.)

So far, my experiments show a pretty easy installation, good compatibility with the existing cabling (I think I'm going to replace the negative side black power cable, it's streched pretty taut and I'd like to add a couple inches to let me mount the ammeter shunts nicely on the firewall) and (so far as five minutes' operation showed) a very good driving feel.

There'll be longer and more detailed writeups with lots more pictuures as I get farther along in the process.

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Page last modified on August 10, 2012, at 05:49 PM