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Old 02-22-10, 03:16 PM   #30
bennelson
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Join Date: Sep 2008
Location: SE Wisconsin
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The Electro-Metro would definately be the energy hog.

It uses a charger which is adjustable for 72 to 108V battery packs, and can pull up to around 1800 watts from the wall, but typically, we don't like to do that.

For the last while, I had been running the Metro at either 96 or 108 volts. Lets set the car up as 96V, because the math is so easy.

Also, we'll turn down the amperage on the charger, with 5 amps, used as an example.

At a 5 amp rate of charge on a 96V system, that is 480 watts. The PV panels I have are rated at 60 watts, and I have 8 of them.
60w x 8 = 480 watts!

Not bad, the car and the solar system are PERFECTLY MATCHED! Of course that doesn't account AT ALL for the built-in inefficiencies of inverting from 48V DC to 120vAC and the charger converting to 96+V DC again.

Also, my batteries are 95 amp-hours. (lets round to 100 to make it easy.)
If my batteries are half run down - we need to replace 50 AH of energy to fill them back up. If we are charging at 5 amps, that's ten hours of charge time.

That might be possible in the height of summer. Around the solstice I might be able to get that much. Otherwise, Its more likely that I would have to let the car sit for MORE than one solar day to get that much energy.

On the other hand, if I just have to run a couple of errands, I may only run the battery pack down just a little bit. Perhaps little enough that only 5 or six hours of solar charging would be needed.

Also, since the solar panels are routed to stationary batteries, and THOSE are hooked up to the inverter, I COULD charge an EV at night, but I would want to make sure my PV system batteries outweigh my EV batteries, and have a low-voltage cut-off to deactivate the inverter if the system batteries drain too low.

Alternatively, my electric motorcycle uses 4 55AH AGM batteries. If those are run half-down, that's only 27.5AH to replace. If the cycle is hooked directly to the solar charging system (instead of through an inverter and AC to DC battery charger) it would be much more efficient.
The PV panels basically make 1 amp each. So 27.5AH/8 amps is just under 3 and a half. The PV would recharge the cycle pretty quick - only half a day.

The Citicar (with a 48V battery pack) would be similar in charging, except that is would have a battery pack double the capacity of the motorcycle. Still only 8 hours of sunshine for a complete charge.
Again, these are all round numbers and battery voltage changes as the batteries charge, etc. so some of this will just have to be tried out in the real world, once I get all this going!

I imagine I would charge EVs from the solar system when I would be at home during the day. At night, (off-peak!) or if I need to turn up the charger (for whatever reason) I could just plug EVs straight into my wall grid-power as I have been doing so far.

PS: I just ordered a Xantrex C-40. It's only $140, has a warranty, and could be repurposed in the future, should I decide to upgrade to a MPPT charger or other system. This is just the basic version - no fancy display or remote reading - but I can upgrade to that in the future if I wanted to.
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Last edited by bennelson; 02-22-10 at 03:20 PM.. Reason: typo
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