Saturday, January 24, 2009

Possible Design Defect

In my opinion there is a design defect in the Electro Automotive VW wiring scheme:

I have lost two 12 vdc vehicle aux. batteries. Last week, the second aux. battery ended up fully discharged … and frozen. (The temp in my barn has been in the 0-25 deg. F range.)

Remember from my last blog entry, I discussed long maintenance charges?

Here's the problem:

Whenever external power is plugged into the car outlet for charging, the 12vdc fan is activated to ventilate the rear battery box. The fan is powered from the aux. battery During this time, there is no recharging of the aux. battery. It's the same as leaving the car lights ON, when leaving the car ... albeit, with a much lower current draw.

I frequently plug in my charger in the afternoon, upon return home, and leave it ON all night, as my PFC-20, turns OFF at the appropriate time. It seemed like there was no downside to this technique. Several times, when the power was plugged in for extended times, even with the charger OFF, the aux. battery became fully discharged, eventually resulting in my buying a new battery.

During the worst of this winter, my car stays in the barn. In order to preserve the batteries, I use my PFC 20 to frequently charge the batteries. Last week, I left the charger on for 24 hours, in 10 deg. weather, with the charger set at the appropriate float voltage. When I checked later, I discovered the fan stopped, the aux, battery dead ... and frozen! I now have to buy another new battery.

I think it's a poor design to run the battery box ventilator with a 12vdc fan, powered from a source that isn't kept charged. I plan on replacing the fan, ASAP, with a 120vac fan that runs from external house power whenever the vehicle is plugged in.

If this situation applies to you, I suggest you replace the 12vdc fan with a 125vac fan, wired in appropriately.

Just my opinion.

Friday, January 09, 2009

Winter Upkeep: Part 2

In battery lore, there are two critical numbers: The first is the "Charge to" voltage, sometimes referred to as the "Acceptance" voltage. This the the voltage the pack should be charged to after usage. The second number is the "float" voltage. This is the voltage the pack should be held to when not being used i.e., the pack should float along at this voltage when idle. Both voltages are computed, based upon battery type and battery temperatures, among other things.

In the case of my pack, the float voltage at the 30-35 deg.F, is 105.95 - 106.25 volts. Using a thermometer, my PFC20 charger and a lab quality digital voltmeter, I am going to float the pack for a day, or so, to do a rather lengthy "equalizing balance."

(CLICK photo for a larger image)

Sunday, January 04, 2009

Winter Upkeep

It's not the best electric vehicle weather ... especially considering that we're having a hard time even getting our Volvo XC90 (4-wheel drive!) out to the county road.

So, for the time being the VW is staying in the unheated garage/barn. While there, I'm being very careful to keep the batteries fully charged. I have a chart from the battery manufacturer (U S Battery) that states the "charge to" and "float" voltages. Using my HP precision digital voltmeter to monitor my Manzanita Micro PFC20 charger, I periodically do a charge to the "charge to" voltage, followed by a 30-min equalizing charge. This is the same technique I used last year. Even though the vehicle sat for about three months in temperatures as low as -10 degF, when I reactivated the VW, last spring, I saw virtually no loss from the batteries! I hope I can say the same thing this spring!

As far as the video, I mentioned in an earlier blog, that will have to wait until spring. I will get it done ... promise!