DIY Electric Car Forums banner

Newbie hello AND my first question.

3529 Views 9 Replies 5 Participants Last post by  Ziggythewiz
Hi, I am just beginning my EV project and I am very excited about it. I bought a cheap 82 Dodge Rampage with toasted engine, manual trans:), manual rack&pinion steering:), and, after a simple master cylinder change, manual brakes!:D No extra drag on motor, or vacuum pump, etc!
I have been internet researching constantly and going back and forth about how to do it, either high efficiency which = high$$$ or inexpensively but not as fast and rangey. After finding an awesome deal on 8 new 155Ah 12v sweeper batteries with matched charging system (all from an electric Ranger vehicle?) and cables and trays and holddowns and a 48v-12v DC-DC unit, I think I have now settled on a simple 48 volt system. The car is light, just over 2200lbs curb weight, and the batteries add 693 back to it after I strip the ICE parts. Not sure what the motor and controller will add or what the ICE parts will subtract, but I doubt the weight will be much over original weight, maybe 2500 but I doubt it.
So now I am ready to buy a motor and controller and pot box. I keep thinking the 48v-72v D&D ES-15-6 would be good along with the Alltrax 7245 controller, because if I ever want to upgrade to 72 volts, I won't have to change either one.
Any thoughts on my choice? I don't have a big budget at all and they seem to be available and cost is very reasonable. Not knowing much about the different types of motors leaves me at a disadvantage, so I hope someone here will know something about whether the combo will work decently.
I am aiming for a 40-50 mile range. My one way work commute is just under 10 miles of 99% flat ground with 1 RR overpass and 1 freeway overpass to go over, only 3 or 4 lights once I get to town, so I was hoping to charge every 2 days. I was told I can charge it at work too!

Thanks in advance for any and all advice, info, criticism, etc...
:)
1 - 10 of 10 Posts

· Registered
Joined
·
4,005 Posts
Your car will probably be much heavier than stock. You're not getting 50 miles on lead, especially not at 48V. I wouldn't go under 120V, and higher is more fun.

Why would you want to charge every 2 days? With lead, that's not even an option. They need to be charged at least nightly. Since you can charge at work you're much better off shooting for a 15 mile range, that's what I treat mine as with 840 lbs of lead.
 

· Registered
Joined
·
1,379 Posts
The Rampage is a good vehicle concept and pretty light, too bad they didn't catch on in a bigger way.

You'll want to charge more often. Lead acid batteries will last much longer with more shallow charge/discharge cycles rather than fewer deep discharges.

48V is barely enough for a city car, and not really enough for a freeway vehicle. You'll only have around 20 hp with typical components. The other problem with 48V is you get more of your power from high current (power = current * voltage). This means bigger cables, motor runs hotter, etc.

My car was 48V, but it was only good for about 40 mph (although I did hit 55 mph once really leaning on it).

Final thought, if you want a really cheap conversion, you could go with a shunt motor that spins a constant speed. Then you don't have a controller, just a contactor. You'd take off by slipping the clutch, and change speeds by shifting. That's what I did for a while, it's crude but it worked. You'll want to be sure to have a big diode across the contactor to prevent arcs. Another thought is to go with a series motor, but use an old golf cart contactor controller, that would have 24V with resistor, 24V, and 48V steps.
 

· Registered
Joined
·
3 Posts
Discussion Starter · #4 ·
OK Thanks for the info. This is definitely a city car with some slow semi-rural area to go through. I never get over 45 on my commute and about 40 on the way home. I don't have any problem going a little slower. No freeway driving needed.
So, would it be better to add all the batteries and go with 96 volts? What kind of range are we talking about with just one set of 155aH batteries at 96v? I would get more speed I assume, but do I need it? Not really. However, I can plug in every night or every day at work, or both even. I am not looking to go super cheap, just simple I guess. I still want to use a controller I think, but there are so many I just have no idea which, or which motor is best on a budget either. The D&D I mentioned is less than $700 +shipping and the controller and pot box add another $650 +shipping for just over $1400. Not sure what else I need other than gauges but I am totally clueless which are the best for my budget. Simple is good and I could definitely use some suggestions there.
 

· Registered
Joined
·
1,379 Posts
Glad to hear you can afford a controller -- your car will be a bit more efficient and definitely drive better with one. I'd suggest go with 96V.

Range, well, YMMV. :rolleyes: Many conversions use around 300 Whr / mile. 155 Ahr * 96 V / 2.0 = 7400 Whr ( the / 2.0 is for Peukert effect, losses, and not running the batteries all the way flat).

7400 Whr / ( 300 Whr / mile) = 25 miles

That's a very rough calculation and assumes the batteries are fairly fresh and good condition, the alignment is good and the car rolls freely, you drive gently, etc.

155 Ahr is a big battery, these things must weigh well over 100 lbs each? They might also not like high currents. I'd humbly suggest getting a Harbor Freight battery load tester like this one: http://www.harborfreight.com/500-amp-carbon-pile-load-tester-91129.html and testing the batteries to make sure they are up to 500 Amps. Wear safety glasses, don't make sparks, and cover up the battery when you test it!
OK Thanks for the info. This is definitely a city car with some slow semi-rural area to go through. I never get over 45 on my commute and about 40 on the way home. I don't have any problem going a little slower. No freeway driving needed.
So, would it be better to add all the batteries and go with 96 volts? What kind of range are we talking about with just one set of 155aH batteries at 96v? I would get more speed I assume, but do I need it? Not really. However, I can plug in every night or every day at work, or both even. I am not looking to go super cheap, just simple I guess. I still want to use a controller I think, but there are so many I just have no idea which, or which motor is best on a budget either. The D&D I mentioned is less than $700 +shipping and the controller and pot box add another $650 +shipping for just over $1400. Not sure what else I need other than gauges but I am totally clueless which are the best for my budget. Simple is good and I could definitely use some suggestions there.
 

· Registered
Joined
·
3,143 Posts
If you want to see how a bare-bones low-end 48VDC conversion looks and drives, check out: http://forkenswift.com/. He reports about 318 W-Hr/mile and it will go 30 MPH with a range of 20 miles. That's using old batteries and lots of cheap/free components, so he did it all for under $1000.

My own preference is three phase induction motors and you can probably get a 20-40HP motor for under $500. And chances are it will last for many years with minimal maintenance. It can be controlled with a commercial VF drive which you might find on eBay for less than $500.

But you will need to boost the 48VDC to about 300VDC for the drive. For small projects like my electric tractor, it's possible to use automotive inverters, but I'm building my own DC-DC converter. It's only rated for about 2HP but I may build a bigger one. I estimate that a 20HP (15kW) unit would cost about $500. If you are interested in going this route and you have electronic assembly and testing skills, maybe I could help you build one. I'd build one myself but I'm not ready for an electric car yet. Here is my latest video of my project:
http://www.youtube.com/watch?v=j5TyhdY-cHQ&feature=plcp

If you can get enough batteries for 300V then you won't need the DC-DC converter. But that's at least 24 batteries, and if they are like the ones you have (155 A-H) the weight would be about 3000lb and probably at least $3000. LiPo would be half the weight but three times the price. But if you used the 40 A-H at $44 each from http://www.balqon.com/store.php#ecw...ct11900673&mode=category&offset=0&sort=normal you could use 100 of them which would be $4400 and you'd have 12 kW-Hr which might give you 40 miles range.

In any case, I'll be interested in seeing your progress, and I'm willing to help if I can. Good luck, have fun, and be safe!
 

· Registered
Joined
·
4,005 Posts
Range, well, YMMV. :rolleyes: Many conversions use around 300 Whr / mile. 155 Ahr * 96 V / 2.0 = 7400 Whr ( the / 2.0 is for Peukert effect, losses, and not running the batteries all the way flat).

7400 Whr / ( 300 Whr / mile) = 25 miles
That's rather generous. I don't know about sweeper batteries, but I'd divide by 2 for Peukert and another 2 for DOD.
 

· Registered
Joined
·
3 Posts
Discussion Starter · #8 ·
That's rather generous. I don't know about sweeper batteries, but I'd divide by 2 for Peukert and another 2 for DOD.

I think I understand the Peukert Effect but I am clueless as to what DOD is.
 

· Registered
Joined
·
4,005 Posts
Depth of Discharge (DOD) is how far (in %) you discharge a battery during use, so if you use a 130 AH battery to 80% DOD, it is now at 20% capacity, and has 26 AH left in it.

For lead acid, the recommended Maximum DOD is 80%, and recommended typical DOD is 50% for long battery life.

For lithium (LiFePo4) the recommended max is usually 80% DOD or 70% for longer cycle life. Each chemistry is a little different, YMMV, and the different manufacturers each have their own stats.
 
1 - 10 of 10 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top