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electric vehicle and ultracapacitors

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If pulling short bursts of high amp loads followed by extended runs of lower loads was so debilitating to batteries why do common lead acid forklift battery's last for so many years under those working conditions even while most often only getting a proper recharge when they have been drained to the point of being too dead to work?

If massive capacitor banks where able to add even 10% more life to a forklift battery thats being ran in that type of working conditions they would be all over the place by now and I would likely have seen them as standard equipment on then new models.

I can see the potential benefits of them in an EV for efficient regenerative braking applications but still if the vehicle is not being driven in a constant start and stop application that ability to recapture braking energy is other wise of no practical purpose especially if the capacitor bank cost several times what the battery bank costs.
 
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forklift batteries...

I can see the potential benefits of them in an EV for efficient regenerative braking applications but still if the vehicle is not being driven in a constant start and stop application that ability to recapture braking energy is other wise of no practical purpose especially if the capacitor bank cost several times what the battery bank costs.

Big traction batteries are really a different construction than most deep-cycle batteries and can take massive abuse but have a low CEF what can take 8 or more hours of charging at 200 to 400 amps to get a full charge.

Forklift Battery Charging | Forklift-Battery-Charger.com
Because of the construction of forklift batteries, they have certain characteristics differing from regular (smaller) lead acid batteries. Lifespan of lead acid batteries is directly related to the thickness of the positive plates, the thicker the better for deep cycling life. This is why 6 volt golf cart batteries (thick plates) will last longer than the same amp hour pack made up of 12 volt batteries. Automotive battery plates are about .040 inch thick, while a golf cart battery will be about .070 to .100 inch thick. Forklift batteries ordinarily are .250 inch or thicker, and use lead-antimony for plate material. This material increases plate life, but increases water loss and gassing, so proper maintenance is mandatory for good battery life.

I know people who take good care of traction batteries (solar energy off-grid) and have used sets for 20+ years. So if someone is running them dead every week that's stupid.

We agree that stop/start traffic is where a ultra-cap assist system could help but most of the short range cars would operate in this environment. I still don't see them as very cost effective but when has that been a reason not to do something? :)
 
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Interesting! Its been too long for me since I had to deal with those battery's to any extent. Being good with high powered electronics I tended to work more with the speed controllers and charger units. That and fixing cables.

So once again the whole issue comes down to getting the correct batteries for the job.
 
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EV batteries take repeated abuse in the course of a single trip. 500+ amp draws sometimes every 5 minutes in traffic. think everytime your tach on your car jumps up to start from 0 or pass someone. I think it be compared to everytime you start from 0 mph or downshift to accelerate faster. definitely not momentary draws. the high discharges can be 4 to 5 seconds in some cases. especially in city traffic. drive a prius in manhattan and youll be lucky to get 20 miles per gallon yet its rated by the epa for 48 mpg city. Thats a test I have done myself, so I know that from first hand knowledge ;)

In this case we can add a NYC driving test and the range for an EV would drop massively, unless you add capacitors to mitigate the high discharges.

Id have to do some tests to see how much more batteries heat up in an EV. have a temperature monitor on each battery.

the 10 percent range increase wasnt in a plug in prius. a plug in prius has an addon battery pack and a circuit board is made to trick the computer that the state of charge that is broadcasted over the canbus is higher thus making the car run longer in ev mode. 2010 models no longer broadcast the SOC and they have to figure out another way to trick the car into thinking it has more battery and run longer in EV mode.

the increase was in a converted EV. Ill be able to tell you what range increase I get to testing my vehicle out.

I think this boils down to the draws from a battery in an EV and temperature increase do to environment and over discharging cannot be reproduced in formulas on paper. range calculations for an EV are also have too many variables. The nissan leaf has enough battery capacity to take it 100 miles yet there are so many variables to conditions and the way the driver drives that can vary the mileage as low as 60 miles to as high as 130 miles. The volt's range can vary from 25 miles to 50 miles.

as was mentioned, the driving habits of the driver greatly impact what will happen. thats a variable in this equation that cannot be defined. when you drive a prius looking at the mpg number you before a hypermiler and try to get it as high as you can. Ive gotten a prius up to 55 miles per gallon intown.

Thats why I keep arguing for capacitors. In theory they eliminate peukart effect, higher battery temperatures, stresses on the batteries which cause failure, high discharge rates that decrease the amp hour capacity, and can take abuse and kep coming back. at 1 million cycle life, the abuses may bring it down to 500,000 cycles but they just keep ticking.

I mentioned before this discussion always ends up turning into a cost comparison game, an arguement over the real beneifts of capacitors, and the idea that batteries have always operated ok in these situations and always will (logical fallacy).

the ultracapacitor itself has only been around for at best 5 years to the general public. in the last 5 years the price of these capacitors has dramatically dropped due to the demand rising for them. before that at 10 years ago the prices were "if you have to ask you cannot afford it"

Testing will tell. I have the capacitors already, that isnt the problem.

I posted this thread to get the project discussed and how it can be done, not to discuss whether it was a good idea or not. as far as regenerative braking being essential here i AGREE. so lets put in a way to keep these capacitors charged is by a 15000 watt generator. when the generator cannot keep up with the demand the batteries lend a hand. they can recharge the capacitors when needed but can only send 200 amps at best.

second design:

everything is in series. the capacitors are series for 54 capacitors for 145.8 volts. the batteries are behind them at 144 volts all in series. the batteries are 6 volts and there are 25 of them. the generator is behind the batteries, able to produce 200 volts into the batteries and capacitor string. able to surge to 300 volts. the controller is able to see the energy storage amounts and can be programmed to only deliver 144 volts to the motor.
 
tecate group has a nice ultracapitor sizing tool, a spreadsheet.

I entered in the following values

working voltage: 145 vdc
minimum voltage: 1 vdc
current: 600 amps dc
time: 9 seconds


it gave me:

maxwell boostcap 3000 recommendation
number in series 54
number in parallel 1
total capacitance 55.6
total ESR 15.66 milliohms
weight 29,700 grams
volume(L) 21.5536
energy stored at working voltage 584,028 joules
energy stored between working voltage and minimum voltage: 584,000 joules
balancing resistor recommendation 52 ohm

if anything it shows these monsters store some incredible power!

the sizing tool is at **broken link removed**

interesting to note, a typical converted EV takes 200 watt hours per mile. 584000 joules is equal to 162 watt hours...
 
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I work in a huge warehouse, with about 300 pieces of battery powered equipment. Most will not lift a load, when the battery discharge is getting dangerously low, which is good, since it leaves enough to drive to the battery changing station. Some of the older equipment, and the tuggers can be driven until they die, and need to be towed in to get the battery changed. The batteries are pretty well abused, wouldn't swear that they are properly maintained, nor fully charged every time they are put back into service. We get some (10-20) batteries replaced every 2-3 years or so, but not really a lot considering the number we have in the warehouse. We have a lot of equipment, and spare batteries on chargers to keep everything moving 16-20 hours a day, and most of us work at a fast pace. Still have a hunch that if the battery was right for the job in the first place, you wouldn't need the capacitors, or they would have been in industrial equipment long ago. A new Forklift battery costs around $3,600 a few years ago, but not sure if that's brand new, or re-manufactured... I'd have to guess that maybe the car battery is a little too small, because of the size and weight restrictions of the vehicle, maybe cost as well, since it's the only consumable part on the car...
 
forklift batteries are also 2000 pounds for a nice sized one.

I have looked at using forklift batteries, they can take the abuse and laugh. the weight just makes them unusable unless you want to convert a semi lol
 
My old Ford Electrica used 16 6 volt 220 Ah that weighed about 100 pounds a piece and for a small sized car, 1984 Ford Escort hatchback body, it didn't have any trouble with the added 1600 pounds or with four of us 250 pound guys in it on top of that going for a joy ride. The only suspension changes they made where an upgrade to set of heavy duty higher capacity springs and tires Vs the stock ones.

My point is if the vehicle is set up for it adding considerably more weight is no big deal if the added gains are justified to extend the longevity of the vehicle. If I was ever going to build a full electric vehicle of my own I probably would go with doing it to a full sized 3/4 ton pickup and go with multiple smaller sized forklift type batteries or one designed for that level of abuse.

Years ago I was at a manufacturing place in Minneapolis that had the largest electric forklift I have ever seen, big ugly looking lime green thing. It had a 15,000 pound lift capacity so I am assuming it probably weighed at least double or triple that itself. I think it used two 48 or 60 volt battery's in series but what amazed me was that even when carrying a 10,000 pound load it still could accelerate with out effort and easily do at least 10 MPH on level ground.
To me that pretty much convinced me that if I had that drive motor and similar battery system in an electric pickup, even if it weighed in at 12,000 pounds, it would still have no problem doing highway speeds for some distance or substantial stop and go driving all day long.
 
the balancing resistor size that they recommend, would that mean I just need to put that size resistor between each cell for a passive balancing system?

a 52 ohm 2.7 volt resistor?

basically in parallel with the busbar is what Im reading. the recommendation for my 54 series ucaps is 52 ohms. this would be a simple balancing system just for testing cost, i wouldnt have to buy the active balancing boards at 65 dollars a pop, although if all successful I will pay the extra money for a active balancing system.
 
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buying a forklift and just transferring parts is more money than buying a boat load of caps LOL

I have serious doubts about that considering you get a good traction motor and controller plus the battery and a load of other assorted electrical and mechanical components plus when it is all gutted out there is the several tons of high grade cast iron that brings around $200 a ton scrap value.

**broken link removed**

Bank for the buck this would be my recommendation for a source of cheap and compatible parts for a DIY EV.;)
 
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I think it all boils down to how sophisticated you want to make the charge controllers. Since they will most likely be home brew if you want to get the very most out of your system. Might be time to start a flow chart. Some things are more important that others. For example you want to charge the caps first with regen then batteries then what? Mechanical brakes? You want to start with caps (if they are charged) then batteries? Gas engine to charge the caps? To what level? Need to leave room for regen. Charge the batteries with the generator? Why not? One thing for sure, you will be moving around a lot of amps in a lot of different directions. This will need a lot of processor power to manage things and a lot of high power switches.
PS. 52 ohms sounds way to high to balance the 3000F caps.

Maybe there is an easier way. What is the internal resistance of each of your batteries. What voltage. What is the ESR of each cap.
 
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OK once again let's go back to the mechanics. Most fork trucks run off hydraulics! The motor never see's a locked rotor.
You can not compare apples and oranges. Forget about the caps and use a nice hydraulic transmishoin.
 
^ I think you have to go back to basics.

1. What do existing electric vehicles use and why?

2. Do you think you can make a DIY system without the multi-million $$$ investment the manufacturers had when they designed their systems?
 
Every electric forklift I ever worked on or drove had the traction motor/s directly coupled to the wheels through all mechanical gearing. The lifting mast is powered by an electric motor driving a pump but not the wheels.

Over all from when I had my electric car and on up I have always wondered why electric powered mining trucks, commercial warehouse equipment, trains, and even golf carts have been using battery based or heavily assisted drive systems for some 5+ decades without problems or reliability issues yet the pubic EV manufactures refuse to look at why those proven electric drive systems work so well and last so long despite being used in very harsh working environments.

Is it because big, robust, well built, efficient, and durable are all things not associated with or expected from typical vehicle design of today? :(
 
Well said. The last thing the public needs is long lasting economical transportation.

Maybe its my paranoia, but to me it seems that the car makers are using technology to ensure it is cheaper to buy a newer car then keep an older one on the road.

In the past:
Sealed beam headlights cost about $3 each, and you cold get halogen.
A full set of wheel bearing and seals for my 79 Toy truck cost about $50.
A automatic transmission from the 70's can be rebuilt for about $500 including labor.

Now a headlight lens cost what about $100. I understand that on the latest cars the wheel bearings come in a cartridge, no idea what that runs. Transmissions are a couple of grand.

Are the headlights any better. The wheel bearings are no better. The transmissions seem to die more frequently.
 
I understand that on the latest cars the wheel bearings come in a cartridge,

My 1974 Ford lost a front wheel bearing once. Two new bearings and a new seal for about $35 and a buddy of mine and I changed it on the side of the street in front of his house with a bottle jack, a vice grips, a tube of bearing grease, and an oak stick. :)

My 1999 Ford F250 has the single piece non rebuildable cartridge style that are about $450 and the special tools required add about $100+ more.:mad:


Relating to the new EV tech it just bewilders me as to why they have so much unnecessary extra junk on it to do simple functions that usually serve themselves to be more costly than cost saving in their application and function. :(
 
tcmtech, the answers are quite simple (I work in the automotive industry, BTW).

For starters, the reasons electric drives are often used on trains or large trucks (diesel engine -> generator -> electric drive motor) is because it would be difficult to make a transmission/clutch system to withstand the tremendous torque of getting something so heavy moving from a standstill. An electric motor develops gobs of torque even at low RPM, perfect for getting that large mass moving.

The equipment you are speaking of is also all heavy-duty. It's easy to make something when you have lots of room and weight/size isn;t really an issue. These are very real problems for vehicles that people want to drive, that have room for them and their passengers and luggage.

The biggest problem is that people are picky. Modern vehicles deliver in so many ways. They start immediately and without fuss (due to modern fuel injection). They are comfortable to ride in. They respond well to driver inputs (drivability - this is a BIG issue). When you start off from a stop, your car will accelerate smoothly. There are no jerks or unpleasant changes in velocity. Transmission shifts are smooth and free from lurches. When you step on the brakes, you get a nice feeling in the brake pedal and the car stops consistently every time.

Electric vehicles are very hard to get to behave this way. People come in for repairs all the time as soon as their car behaves differently from the past. If there's been a slight chage in the transmission shifting they notice it. If the car feels sluggish or has less power, they notice. If there's any noise or vibration when braking, they notice. Getting a vehicle to balance, for example, mechanical brakes and electric (regen) brakes smoothly and without apparent transistion to the driver is very difficult. Especially if the driver presses the brake just hard enough to use regen, and then presses harder (maybe someone pulls in front of them) to invoke the mechanicl brakes.

A perfect example of this is the CVT transmission. They work great but feel "wierd" to people because of the constant engine RPM and lack of shift points. Many manufacturers that make CVT's introduced a simulated "shift" so it would feel more like a regular transmission.

And then there's the safety issue. Modern cars are extremely safe in an accident. Try taking a car and adding in 800lbs of batteries and see if the vehicle behaves the same in a serious collision. I wouldn't want to modify an vehicle in such a way and expect it'll remain as safe as it originally was.
 
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