More battery lore

I had a great conversation with Lars' friend Greg this evening and got a much better sense of what we need. Here's the summary.

Battery type
We need Golf Cart batteries, NOT deep cycle batteries. GC batteries are designed for our application, and are way cheaper than what I've been looking at up till now.

Configuration
One string of 8 6V batteries is better than two strings of 12V batteries. More capacity for the money. We could also consider one string of 6 8V batteries, but I don't know that there's any advantage. We are not constrained by size limitations on batteries.

Power Consumption
A typical 200 amp-hr 6V battery costs $60 and weighs 60 lbs. If power consumption at the batteries (taking into account mech./elec. losses) is 2KW (2.7 HP), and assuming we only get about 100 amp-hr out of the batteries due to the discharge rate we can expect to get 2.5 to 3 hours of continuous operation before a recharge. Fortunately, nothing is continuous on the playa, so I'm betting we can get 4 to 5 hrs between charges.

Chargers
We can buy a small on-board 110V charger from Greg for about $300 that allows the vehicle to plug in anywhere. We should have a 1.5KW (2HP) generator in camp for the purpose. Recharge time is about 4 hours. We could also trade off recharge time for ride time, i.e. 3 hrs on, 3 hrs. off.

When to re-charge
An outstanding issue is determining WHEN to recharge! It's not easy. There are expensive devices that measure current vs. time to calculate it. Being kind to the batteries is key to the success of the vehicle so we will have to research that one.

Maintenance
New batteries need to be charged/discharged about 20 times to break them in. They also need to be "balanced" occasionally. I think that means charging them all the way up until they're venting some gas. Have to verify that.