# Generator



## Shawncrockett (Dec 26, 2014)

Hi there, I am very novice at the whole ev scene. I purchased an electric truck (tiger mini-truck) from a local unniversity. The truck has an 5w motor in it. It is a 72v motor and sevcon 72v controller. The truck is programed to only go 20 mph almost the same speed in all 5 speeds. I believe that the controller can be reprogramed to go 65 mph because the motor is barely rotating. I spoke to a company in Utah that said that they could reprogram it. My delta Q charger doesnt seem like it is working so I think a new charger is in order. My Question: I have a 3500 whatt generator in the bed of this little truck. I was hoping that I could hook up the generator to a step down (Variac) transformer to step the voltage down to 72 volts. The motor says 139A on it which I'm assuming is 139 amps. The motor says 45v so I dont know what the amp draw on this but the generator has 13 available amps on the 120v pole and 30amps on the 210 pole. Will the generator work? If its not enough amps can I supliment it with my lead acid deep cell batteries. Any help would be appreciated thanks.


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## arklan (Dec 10, 2012)

ok so..

theres 2 things i suspect u wanna do
1 u want to get rid of the batteries and run it directly off the genset
2 u want to use the genset as a portable charger when u run out of juice

number 1 u cant
number 2 u can but u still need to get that charger working


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## madderscience (Jun 28, 2008)

It is very likely possible to reprogram your system for a higher top speed. there might be legality problems exceeding certain limits (if you care), but most likely you can go to at least 25mph, or 35mph depending on your jurisdiciton, for the maximum legal speed for NEV class vehicles. In the right chassis a 72v system will be able to hit 65mph if it can put out enough amps, but it will be pushing it with any "full size" 4 wheel vehicle. A truck of any sort isn't the best candidate for getting to 65mph on 72v. The best normal car chassis for this would be a 3 door geo metro or similar or low slung fiberglass kit car of some sort.

The bigger problem getting to 65mph is simply power. power goes up proportional to the square of speed due to wind resistance, so you are going to need a lot more power to maintain 65mph than you would at 20mph. a 3500 watt generator will not be enough to maintain power to do this in any normal 4 wheel vehicle. Most EV conversions of regular, relatively aerodynamic cars need 10-15kw from the batteries to maintain 60mph. So a 20kw generator would be more realistic in such a case.

Another problem I have heard of more than once with the generator-in-the-back approach is that many portable generators make very noisy, unclean power that can damage high power switching circuits like EV battery chargers and motor controllers. It would be a good idea to ensure you have a quality generator like a Honda brand or such, and add a good sized line filter to the output at the bare minimum. Also, a switching power supply based charger (as most of them are) will be more efficient than the variac and bridge rectifier approach most likely. (speaking as somebody who has built and used a variac-and-bridge-rectifier based EV charger) 

It is probably going to end up noisier and using more gas than a regular car of similar size and weight if you try to use the generator all the time as the main source of energy. It will also be a lot dirtier than a regular gas car with functioning emission control components. So a lot of extra work for no real gain under many usage scenarios.

if the nameplate on the motor gives amps and volts specifically then you are probably right in what it is rated for, but make sure you aren't interpreting part numbers incorrectly. 45V and 139A seem like odd values for such ratings. Your biggest limiting factor is probably the controller, it should have a KW rating on it someplace or a part number you can look up to find the specs. divide that value by 746 to get horsepower, e.g. 20,000 watts (20kw) divided by 746 is 26hp, more or less.

Good Luck.


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## Shawncrockett (Dec 26, 2014)

What a great comment, thank you very much guys. I was able to reprogram my charger and it works great. I had 6 12v batteries in this little tiger truck but it initially came from the manufacturer with 12 6v flooded lead acid batteries. I bought the thing on auction and it did not have cables or batteries. My 12 deep cycles got so hot they melted the lead that contained the ss bolts that i put my leads too. I am at an impasse now because if I either replace the 12v with 6v and get heavier cables or I go Limn 18650's. My generator idea is still on the burner and debating using two 72v chargers or a variac/bridge rectifier. This would strictly be for back up or extended range (rare). The truck will be my pr/ bidding truck for around town. Most of the time the speed limit is 35. The city here allows recreational vehicle to be licensed for street usage within city limits and the county does as well. The generator that I have is fairly noisy and stinky compared to vehicles of its size IE. gator, razor, mule... So the plan would be only to use it when necessary. I bought a 40v Ryobi limn battery on ebay for $20 that is working I am thinking of getting a little ribbon welder and start making my own lithium batteries. Thank you again for your input. I would like to eventually use these ideas for semi trucks and mount solar panels to the roof of the trailers for additional energy. Thoughts are welcome...


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## Moltenmetal (Mar 20, 2014)

Solar panels on vehicles aren't going to add any significant fraction of the energy needed to operate them unless they spend a week or two parked for every day they're on the road. And an EV tractor capable of dragging a semi-trailer at any appreciable speed for any appreciable distance? Forget about that too.

Best of luck with your little truck though- it should be a lot of fun and will teach you a lot.


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## Shawncrockett (Dec 26, 2014)

In talking with a solar panel expert (who of course wants to sell panels) he said that there are 40% efficient panels that produce 1000w per hour. Being able to place 20 3'x5' panels would produce a peak 20kw, even if it was only half that at 10kw would contribute. Just a thought. What does anyone know about titanate batteries. Would this be a good option for large trucks? why or why not? I may be way off base on the solar panels but I think as prices go down they start to have roi.


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## Shawncrockett (Dec 26, 2014)

Another question I have is why are my leads melting the SS bolts out of the lead of my battery posts? I have 6 12v deep cycle batteries. I took them out. The manufacture stated that the truck was designed for 12 6v trojan batteries. I think part of the problem too is that I was using 6 gauge battery wire. If I traded to lithium ion batteries or lithium titanate would I still have this problem?


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## major (Apr 4, 2008)

Shawncrockett said:


> Another question I have is why are my leads melting the SS bolts out of the lead of my battery posts? I have 6 12v deep cycle batteries. I took them out. The manufacture stated that the truck was designed for 12 6v trojan batteries. I think part of the problem too is that I was using 6 gauge battery wire. If I traded to lithium ion batteries or lithium titanate would I still have this problem?


It is difficult to give a guy like you advice due to so little information provided. Please fill in at least your location in the user profile so it shows up in the post header. Thanks. Also, please tell us about the vehicle and systems with photos especially where the problems occur. Thanks.

As far as the trouble with the battery terminal heat: Check for "ampacity". I suspect you meant a 5kW motor, not 5w. So for general nominal figures, take 5000W and divide by 72V for about 70 Amperes. That, and maybe a healthy safety margin to say 100A, is what your cables and terminals need to carry, or for ampacity.

Now, I suspect your problem was more to do with the quality of the terminations than the wire gauge, but certainly #6 sounds small. Let's look at how you had the battery terminals assembled. It is unlikely that it was the battery's fault. And the proper method, parts, tools and cable can be used for Pb-Acid or Lithium.

Regards,

major


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## Hollie Maea (Dec 9, 2009)

Shawncrockett said:


> In talking with a solar panel expert (who of course wants to sell panels) he said that there are 40% efficient panels that produce 1000w per hour. Being able to place 20 3'x5' panels would produce a peak 20kw, even if it was only half that at 10kw would contribute. Just a thought. What does anyone know about titanate batteries. Would this be a good option for large trucks? why or why not? I may be way off base on the solar panels but I think as prices go down they start to have roi.


Just FYI, 40% efficient solar panels would utilize exotic multijunction cells. These are usually bought by satellite manufacturers who are paying $25,000/kg to launch them into orbit. They would likely be...out of your price range.

Standard panels available to us mortals max out at about 20%, so I would recommend using that as the number for any estimates you might do.


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## Shawncrockett (Dec 26, 2014)

Awesome thank you...


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## Moltenmetal (Mar 20, 2014)

Just plain forget about panels- they're at least an order of magnitude too low in energy density to be useful on a vehicle. You can easily find data on how many kWH per year you will get out of a properly oriented kW of panel nameplate capacity for your region- the sun isn't at peak power all day all year, so these factors are important. Then remember that about half the panels will be in shade if you try to use the sides. Select a real panel you can buy rather than worrying about efficiency calculations- the ones I've shopped for give about 1/3 to1/4 the nameplate capacity per unit area that you're assuming. You'll soon see that you'd be far better to focus on efficiency in the vehicle itself than trying to turn it into a solar collector.


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## Shawncrockett (Dec 26, 2014)

I had planned on purchasing panel sets for my shop, to check efficiency but it sounds to me like the price points need to lower substantially in order to wrap. I looked into the cost of titanate batteries and they are about 4 times the cost of lifepo batteries. The durability claims to be up to 10 times that of limn but time will tell.


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## Caps18 (Jun 8, 2008)

I have 1.7 kW of solar panels on my roof of my house. They produce 14 kWh on the best day in the Summer, spending all day with no shade.

My battery pack on my truck is 24 kWh, so even with 350 lbs of solar panels, I can't even drive a small pickup truck the full range in a day. Now, since I don't drive that much every day, the energy will build up day after day, and it should even out.

I'm not saying it is impossible (I have a future project in mind), but it isn't the most practical. It would take 90 panels to produce enough power to drive a heavy vehicle (3000 lbs) at 60 mph. 300 Wh per mile for 60 miles = 18 kWh. 18000 Watts per hour / 200 Watts per panel = 90 panels. And if you had the panels on the vehicle, it would add another 3800 lbs.

As for the gas generator, there is a guy in Canada who did add one to his pick-up truck to make it into a plug-in hybrid. And if I ever were to take a trip across the country or travel from Seattle to Alaska, I would be using a generator to help recharge the batteries.


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