These are some projects that might be helpful in conversions

From http://www.cameronsoftware.com/ev/EV_BatteryManagementSystems.html

Each battery has a regulator which consists of

• 2 - ring terminals, with hole for 5/16" bolt, and crimp for #6 wire
• 2 - 6.8v 5watt zener diodes
• 2 - #PR2 flashlight bulb

Solder a zener diode into each ring terminal where the wire normally goes. Solder a 6" piece of wire to the other end of the zener diode. Solder the flashlight bulb between the free ends of these two wires. Now you have the two zeners and flashlight bulb all wired in series.

Lee added on 8/09 - Since there are two zeners in series, and they have a 5% tolerance, I measure their actual zener voltage, and match them up in pairs with the same total. I have a bench power supply with knobs to set the voltage limit and current limit. I set the current limit to some value like 100ma, and set the voltage limit higher than the zener voltage (like 10v for a 6.8v zener). Connect the zener, and the power supply automatically supplies a fixed 100ma. Measure the voltage across each zener. Sort them into bins (6.5v 6.6v 6.7v 6.8v 6.9v 7.0v 7.1v). Use pairs that add up to the same total
6.5v + 7.1v = 13.6v
6.6v + 7.0v = 13.6v
6.7v + 6.9v = 13.6v
6.8v + 6.8v = 13.6v

Fill the space between the zener and ring terminal with epoxy glue. Likewise, dunk the bulb and its wires in epoxy glue. This makes everything waterproof and acid proof, and helps conduct heat. The zeners get their heatsinking from the large ring terminals and battery posts they are bolted to.

Lee wrote on 9/2/09 - On mine, the diodes are potted with a thermally conductive glue inside a "heavy duty" copper ring terminal. The ring terminal is bolted to the battery to act as a heatsink for the heat produced by the zener.

Put one of these circuits across every 12v battery. If the charging voltage exceeds about 13.6v, the zeners begin to conduct and the lamp lights. At about 15v, the lamp is fully lit and is bypassing about 0.5 amps.

Use a photocell to detect the light being produced. When any of these battery regulators lights, the photocell sees it and either switches the charger off, or to a low-current trickle charge or float voltage setting.

6 V Version -

Comments and an ansii schematic by Lee (5/06) -

I published the version for 6v batteries a year or so ago. Basically, I suggested the same parts (two 6.2v zener diodes), but with *two* #PR2 lamps. Each lamp has a zener in series. This makes two parallel paths, so it shunts twice the current -- 1 amp max instead of 0.5 amp max. This is more appropriate for >100 amphour batteries.

One zener and one lamp in series, wired across the 6v battery. Use two such regulators across each battery. Physically, you'd put one zener in the ring terminal on the + battery terminal, and the other zener in the ring terminal on the - battery terminal. Like this:

If the 6.8v zener lets the voltage get too high (gel cells, for instance) try a 6.2v instead.

You want a zener that draws negligible current when you aren't charging. The fully charged voltage for lead-acid is around 2.1v/cell, which is 6.3v for a 6v battery, 8.4v for an 8v battery, or 12.6v for a 12v battery.  AGMs tend to be a little higher, and floodeds can tolerate a little more. [The lamp]  provides a roughly constant current once the zeners start to conduct.

I used a pair because two 5w zeners are cheaper than a 10w zener. Also, I could put one in each battery terminal, to split the heat between them rather than concentrating it all at one point. Also (I never do anything for one reason :-) because the temperature coefficient of zeners around 7v is roughly zero.

The resistors act like just a backup system. Someday the bulb may burn out or get broken. The resistor means you don't lose *all* regulation.

Your charger has to be smart enough not to charge excessively. The charger has to be at a low current when the regulators begin working, and has to shut off after a relatively short time. You can do this "open loop" by arranging the charger so it automatically delivers low current for a short time. For example, a transformer-rectifier charger that is adjusted to deliver <1 amp at 2.5v/cell, and has a timer to turn itself off in 1-2 hours.

Or, you can do it "closed loop", where the light from the regulators commands the charger to cut back and turn off.

This is a parts list by Chris Zach, parts from Mouser

• 606-PR2, PR2 Chicago Miniature Incandescent Base Flange 2.38V .5A
• 526-1N5341B, 1N5341B NTE replacement Diodes/Rectifiers 6.2V 5W ZENER DIODE
• 610-CZ5342B, CZ5342B Central Semi Diodes - Zener 6.8V 5.0W
• 660-MF1/2DLT52R10R0F, MF1/2DLT52R10R0F KOA Speer 1/2Watt Metal Film Resistors 10ohms 1% 100PPM

And of course you need potting compound:

• 1 590-832-TC-450ML Epoxy Compound 1 1 0 $29.95

The smaller lugs are standard Home Depot 12-10 gauge yellow lugs; the smaller diode fits in them. For the larger one I used heavy-duty 6ga tinned eyelets, with a 5/16" bolt hole, from Waytek Wire, part# 36472.

Here is a link to a PDF that shows the steps in making the Zener regulator

I got these drawings of Mark Brueggemann's when I got my partially finished S-10

Side view, showing the gas lift attachment and the fabricated frame that the bed sits on.

This shows fabricated frame that the bed sits on and the pivot hinge details

Solectric S-10

When I was thinking about my conversion I really thought that the Solectric S-10 configuration was very well done.

They had 2 motors, 2 controllers and the battery pack all rear of the cab. The bed tilted up at almost 90 degrees.

Here you can see the rear of the S-10 with the bed tilted up, the 2 motors with the drive shafts facing to the rear. The rectangular aluminum box that they are bolted to has a rubber drive belt which in turn connects to the drive shaft of the rear end. The other end of the tail end of the motors connected to the cross member. You can see that the drive shaft has 2 universal joints to permit it to flex with the up and down of the axle.

Here is a view of the motors from the bottom rear of the truck. It looks like a different truck, cleaner.

You can also see that that there are 6 leaf springs. My US Electric S-10 also has 5 springs. As manufactured by GM it had a GVWR of 4800 Lbs, but US Electric added another leaf to make the GVWR of 5600 Lbs. So maybe the Solectric also has a GVWR of 5600 lbs.

Comments?

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