Open Source Plug-In Hybrid Super-Truck

[mechman600]

Originally Posted by Hondo

Hey Ben, if I were you I would take the dc to dc converter out of the picture. I could usually go 3 or 4 days without recharging my accessory battery on my Fiero. Unless you are planning on not starting that diesel engine (which would recharge the accessory battery) for days, why do you need the converter?

I highly advise using a DC-DC converter. My Electric Booger doesn't have one, and accessory voltage isn't ever quite high enough. It starts off ok, but soon it's 12.4..12.2...11.9...dimming lights, windshield wipers slow...etc. It's bloody annoying charging the battery (at least the way I have it set up), always monitoring how much it needs, etc. It would be nice to just plug in and walk away and this is the one thing that makes this impossible. Keep in mind that my accessory battery is a new massive group 31 battery out of a highway tractor, not a puny car battery.

I want a DC-DC converter bad!

Do you know what brand you would go with? The Kelly looks good and is very cheap and I haven't heard bad things about it.

What is your system voltage going to be?
Are you going to try to integrate the ICE throttle control and EV potbox into the same pedal or keep them separate? I think a motorcycle twist grip pot as a gear shift lever handle would be great for controlling the EV side.

I don't see any problems with your configuration. A massive sledge hammer ought to make a nice hump in the floor. Batteries behind the axle shouldn't be a problem either, as long as you don't use flooded lead acid.

Looks good!

[bennelson]

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!

[mechman600]

Originally Posted by bennelson

...but I really like the idea of something twisted.

Ben - this whole project is a bit twisted!

[bennelson]

Here's what I'm thinking for the throttle.

I'd hack an e-cycle twist throttle, combine it with a stick shift knob, and mount it to the stick.

The driver can then both shift and e-ccelerate with one hand.

[Ryland]

Originally Posted by bennelson

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.

If you had two large power diodes that were rated high enough then you could isolate the dc/dc converter from the alternator and whatever one was putting out a higher voltage would charge the battery, that seems like the simplest solution if you want an alternator, is there a problem with not having an alternator and just running all of the electrical loads off of the drive pack? still having a battery that the DC/DC converter kept charged, for starting the diesel engine, but once the engine started the drive pack would recharge that starting battery.

[Daox]

It really just depends how complicated you want to make this thing. Best efficiency would be to never run the alternator unless you have to. So, you could have an alternator disable switch that kills it in hybrid and EV mode, and in ICE mode. However, you'd probably still want some circuit to watch your pack voltage and kick out the dc-dc at some point if you have a very long ICE trip to make so it does kick on the alternator eventually.

The simpler thing to do would be to disable the alternator in hybrid mode (and EV mode obviously) and just turn it on in ICE mode. With a little tinkering (probably just a relay or something) this could be built right into your mode selector switch.

I take it you still haven't heard back on from that forklift guy on the motors?

[bennelson]

No, still haven't heard back from that forklift guy. I'd really like to call and hassle him, but hey, don't look a gift horse in the mouth either....

I think this project is going to be an exercise in "practical" fuel economy and driving, rather than "Theoretical Best".

While an alternator is mechanical and not ideal efficiency, it's also practical, reliable, and already there. For those reasons alone, I'd rather not remove it. Once the project is rolling, I may then be able to start experimenting with disconnecting it, and if everything works great, then remove it.

In general, I want things to be redundant at this point. I have a feeling that I'm going to be driving this truck on one system or the other BEFORE the other one is finished. Since it's home-brew and of questionable workmanship, the redundance will be handy.

When I converted the Metro, I welding a tow-bracket mount to the front. If anything ever went wrong (which was SEVERAL times) I could just tow it home with my pickup truck.

Since I'm now converting a pickup truck, it's going to have to tow itself home. That means that both the ICE and EV systems need to be fully functional by each ones self.

As Daox said, some sort of control over the alternator and DC/DC through the mode switch seems like a good idea.

As for having a DC/DC converter but NOT an alternator, I can see situations where I would drive until the battery pack runs out and then drive on the engine. At that point, I would need the alternator.

[mechman600]

Originally Posted by bennelson

As for having a DC/DC converter but NOT an alternator, I can see situations where I would drive until the battery pack runs out and then drive on the engine. At that point, I would need the alternator.

Ooooo...good point. I was going to mention the elusive alternator delete mod that everyone here wants to do and rarely does and how you have the perfect chance to do it....but then you mentioned this ^. Better keep the alternator, at least for a little while.

[bennelson]

I was driving home today, and got a reminder that there are ALREADY commercially-available diesel-electric plug-in hybrid trucks that I see nearly every day!

The local school bus company owns 14 hybrid busses. Here's one I took a photo of at a traffic light.



The best part is that they solar-charge them! The car port that they park under has a giant grid-tie PV array that nets out to how much power the busses use through the year. I believe the bus is THIS ONE, in case you are interested.

I also dug through my box of misc EV components and found that DC/DC converter. It's rated at 15 amps at 12V, and has an output voltage adjustment, so I should be able to turn it up into "12V battery charging range".

It's a brick that's about 8 x 2.5 x 4 inches and will run on 110-330VDC

I think 180 watts should be enough for a truck DC/DC converter. Regular headlamps are usually 55 watts each. Taillights and radio can't take much power. I'm not sure how many watts the heater blower runs, but if I was in EV mode anyways (and thus using the DC/DC instead of the alternator) I'd probably just be using a seat heater.

There's always the possibility of converting to HID or LED headlights as well, which should also lower the 12V power load.




I guess technically, this is just a power supply, but it can run on either AC or DC.

[bennelson]

I took a look at the DC/DC converter last night.

It appears to be some sort of electronics power supply that can run directly from either DC or AC power, and provide up to 180 watts.

I rigged it to run from 115 volts AC from the wall with a cord. I tested the output from it, and sure enough, I get 12+ Volts. I tested it with a 12V bulb and a couple other small items.

Next, I played with the adjustment potentiometer on it. I was excited to see that it has a wide range of output. At the highest, it put out 14.25VDC. At the lowest, it output 9.25VDC

I should be able to use this in the truck, running off the main battery pack to output 14.1V (or whatever charging voltage I want) to the 12V truck battery. The only downside is that it's obviously NOT weatherproof. I'll have to make sure it is properly protected from the elements, but still gets plenty of cooling. It doesn't have a fan on it either. I could add a small 12V DC fan real easy. It didn't get hot at all in use, but I wasn't loading it down to hard or for too long either.

I ran it through a Kill-a-Watt energy meter on the AC side. By knowing how much energy was going in, and the wattage of the loads I was connecting, I can calculate the efficiency. Looks like the power supply is over 90% efficient. (I was just doing quick math in my head. Hard to hold electrical contacts and write down numbers at the same time.)

At the same time, I also dug out a box of misc. winter EV-related parts. In there, I found that I had a battery heater blanket that's pretty big. I think it's designed to wrap around 6 Group 24 batteries at once. Thats about 150 watts of heat.

I also found that I had a 30 foot, 60 watt, electric pipe-warmer tape. That's a material that you wrap around pipes to prevent them from freezing and bursting. It runs on AC power and has a built-in bi-metal switch. When temperatures are low, it turns itself on. When things are warm enough, it turns itself off.

I thought the pipe-wrap might work well for heating the fuel tank on the truck. Diesel is never especially warm, but if I ever want to use veggie oil, I know that has to be nice and warm to run. I know I'll need additional heating for a veggie tank, but the pipe wrap might work well for the diesel/bio-diesel tank.

Another fun item I realized I had was a 1-ohm resistor. Recently, I read on another thread on Ecomodder of somebody using a one-ohm resistor for something or another and mentioning how nice the math works out on it. I can never remember all those electrical laws, so I just looked it up on a calculator. Sure enough, at 12V, one ohm draws 12amps. And 12V x 12Amps is 144 watts. That's pretty hot for a 6-inch cylinder.

It may actually be enough power for a decent, basic electric defroster. I think if I had it mounted on a bracket with a small DC fan, pointed towards the windshield, and a 15-amp fuse, it might work well. Look a little funny, but work well.