The truck as it is has daytime running lights. Combine that with using the heater blower motor, and other additional loads that winter creates, it adds up to a fair amount of power.
On the Electro-Metro, I just used the stock 12V battery, and recharged it at the same time I charged the main battery pack. That's a pretty short-range vehicle, and even so, I still felt like I was rather beating up my poor 12V automotive battery.
What I really want is for the truck to basically perform the same whether it's running on diesel or electric. If I have a DC/DC converter, then I won't need a separate charger for the 12V battery.
I really might not fire up the diesel for days at a time. If I'm just running into town, I don't want to have to waste the fuel to warm it up.
On the
motorcycle, I have
a DC/DC converter I bought for $10 that was designed for computers. It's only 100 watts, but it runs on a range of 36-72V - perfect for a motorcycle. It didn't work so well when I was originally running a 36V system on the motorcycle. The headlight and other 12V electrics ran straight off the converter. One night, I was coming home in the cold and dark, and had a big hill to climb near the end of my trip. That meant my batteries were low. The extra amps of climbing the hill dropped my system voltage below the minimum that the DC/DC ran on and *POOF* no more headlight going uphill on a dark country road!
I planned to alter it so that there was a small battery in parallel with the DC/DC converter, but when I upgraded to four 12V batteries, it was moot. Even with my main battery pack nearly dead, it was still more than enough juice for the converter.
In the truck, I'd like to take good care of the 12V battery. I'll probably start off running just a used auto battery, but I'd like to upgrade to maybe something like an Optima Yellow Top in the long-run. A lithium 12V battery would be great, but it's one more thing to spend money on, and I think I'd rather have my alternator trying to murder a lead battery than a lithium one.
It seems to me that what would make the most sense for a Plug-In Hybrid is to have the alternator charge the 12V battery when the engine runs, and a DC/DC converter charging it when the engine doesn't.
Which makes me wonder - if the truck is in Hybrid Mode, should the DC/DC converter be running or not? I guess if the engine is killed, then it SHOULD be on. On the other hand, if I'll be turning the engine back on soon, why bother? The battery will just start charging from the alternator next time the engine starts. I guess the only thing I wouldn't want to do is have the alternator and DC/DC converter BOTH running. They might not like each other that much.
I already have a DC/DC converter around that I salvaged a while back, but it runs at a higher voltage than the Metro was running at, so I never installed it in the car. It just looks like a power supply - a rectangular brick with some wire terminals and air vents. It's a decent power level though. I'll have to dig it out and see what the specs are on it.
I don't know what system voltage the truck will have yet. I've always told everyone who asks what voltage to use "As high as you can afford!". Probably 144V, but who knows at this point. The Open Revolt was originally designed for up to 144, so I think that's a good goal.
As far as throttle, I actually kinda like the idea of a motorcycle twist grip on the stick shift. When I was first getting the Electro-Metro going, I didn't have a dedicated pot box for it, but I DID have the one from the motorcycle. So, my first drive around the block in a homebuilt electric car WAS by twisting the throttle on the stick!
The shift knob in my current gas truck is a big black plastic knob from some sort of industrial machinery. It's big and flat with notches out of it for a godo grip with your fingers. Sometimes as I drive, I twist it a bit as I would in a twist-throttle hybrid truck.
Is it weird that I already imagine doing that kind of thing?
I guess that in my life, the lines between what is and what could be are a bit blurrier than for most people. Which is a good thing, I think. It means I do things that other people can't even imagine, and therefore can't make happen.
I think I would take a 0-5Kohm potentiometer and embed it in a nice twist knob with a good grip. Something that would still be good and solid for shifting through the gears, but could get a good twist of electro-power!
A thumb lever pot could work too, but I really like the idea of something twisted.
EDIT: Hmm. A boat throttle could work too. That way I would have cruise control!