# 120v FLA or 72v Li-ion?



## Roy Von Rogers (Mar 21, 2009)

hans j said:


> Next year it will probably be time to replace my aging US125 batteries in my caddy. I am torn between just replacing them (and likely have all the range I really need) or buying half a pack of Li-ions (at least 200Ahr).
> 
> My truck weighs 3300 pounds and 1350 of that is batteries only. I can drop almost 1000 pounds by switching over the the 72v pack (and going full 144v then next year). Currently I can get 15 miles in 50* weather with over 5 year old batteries. I can actually drive freeway speeds for a while, the car only pulls 200 amps on a good day on the freeway but still gets up to 60-65 mph.
> 
> ...


 
Your always better off to go higher voltages, instead of high amps. Dont know which Zilla you have for max input voltage. 48 100ah lithuims would be better then 24 200ah. You can control how much voltage to the motor with the Zilla. It reduces the amperage the system and wires need to handle, and gives you some room for motor voltage adjustment to suit your motor.

Btw mixing lead with lithium not a good idea.

Roy


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## hans j (Mar 31, 2008)

My Zilla handles 144v so the plan was to get half a pack this year and then the other half next year. I never intended on mixing battery types, just getting rid of the FLA all together.

So pretty much I would end up with the highest voltage possible for my controller (and probably motor) with the highest amp hour. I guess I could just as easily do 144v 50ah batteries but then what will my range be?

I was under the impression amp hours is distance, voltage is speed. Most of my driving is on 25-40 mph streets, so why not make the most of it?


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## piotrsko (Dec 9, 2007)

the only problem is that 1/2 the pack would be older and cycled. Worst case is at some point the older cells will have different characteristics, and possibly different chemistries so the whole pack will be harder to balance.

How many watt hours in the pack you use now?


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## dougingraham (Jul 26, 2011)

hans j said:


> So pretty much I would end up with the highest voltage possible for my controller (and probably motor) with the highest amp hour. I guess I could just as easily do 144v 50ah batteries but then what will my range be?
> 
> I was under the impression amp hours is distance, voltage is speed. Most of my driving is on 25-40 mph streets, so why not make the most of it?


72V * 200AH = 14.4kwh

144V * 100AH = 14.4kwh

Same amount of energy. The range should be the same if the car is driven exactly the same way. With the higher voltage pack you will have much better acceleration and top speed.

The motor controller is a switching power supply that converts the high voltage from the traction pack to a lower voltage that feeds the motor. The only time this is not true is when the controller is at full throttle. Then the motor sees pack voltage. But you don't do that for very long.

If I understand correctly your vehicle would weigh about 2300 lbs with a 144V pack of 100AH lithiums. With a reasonable mix of driving conditions you could see 250 to 300 wh per mile. Assume 300 as reasonable conservative number that makes your range about 48 miles to flatten your pack. Call it a safe 38 miles (80% DOD).

If you feel the need to double that in a year go ahead and buy another set of the 100AH cells and pair them up, new with old and then series those together to make a 200AH pack. Because the weight will go up you won't quite get twice the range but it will be pretty close to twice.

Best Wishes!


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## Guest (Nov 5, 2011)

It's always better to have the higher voltage pack but if you can't I would not go with 72 volts. It just won't have the ummph to get you to a good speed. Around town at 45 mph or slower you'd do OK but not great. Minimum I now say for a heavy vehicle is 120 volts. Better if you can go to 144 or higher. My original electric Ghia was 72 volts. It was fun but was way better when I upgraded to 96 volts. I also did a 77 Midget with 120 volts of lithium. It was way better than 72 volts. I plan on going up to 156 soon. The higher voltages are also easier on the batteries. So go with the high voltages. The highest you can do the better. 

Pete


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## hans j (Mar 31, 2008)

dougingraham said:


> If you feel the need to double that in a year go ahead and buy another set of the 100AH cells and pair them up, new with old and then series those together to make a 200AH pack. Because the weight will go up you won't quite get twice the range but it will be pretty close to twice.


This is basically my plan except using 200ah batteries. I would like to do a higher voltage but that would mean a new controller and motor adding to the expense.

I searched again on evalbums for cars similar to mine and found a couple nearly exact builds. The original builder of my car first listed a 40 mile expected range with the us125 batteries. He was getting 30 miles out of two strings of Optima yellow tops. A couple cars are claiming almost 60 miles in the same little pickup with the same us125 batteries.

I still plan on doing a lot of aerodynamic improvement to the car. Have a lightweight tonneau cover I need to finish, salt flat discs on the wheels and going to do a mostly full belly pan and wheel well liners to reduce drag. I have been shaving weight where I can too.


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## rwaudio (May 22, 2008)

It may not be apples to apples as I have an 11hv and I'm not sure if the RPM/volt relationship is even close.

Testing on 50v (16S3P pack of 123 pouches) runs the motor at about 1100rpm and although it drives nice, top speed is limited to about 50-60km/h (in 4th or 5th gear, can't remember) doubling the pack to 100v made a night and day difference to the drive-ability of the car. Peak RPM moved up to about 3000rpm under light load and I was easily able to keep up with traffic and even a brief period on the highway at 120km/h (I did need 5th gear though) It's not ready for daily use though and I would say it needs much more voltage, I don't have testing to back it up but I would say 200v on the 11hv would be the minimum. If the relationships are similar I would be willing to bet that 100-120v on a regular motor would be the lowest part of the sweet spot to run it.

For a bit more background the car probably weights around 2600-2700lbs right now, the pack will easily put out 1000A I'm using a Soliton1 capable of 1000 motor/battery amps. On this voltage the current doesn't help, I can peg the meter for a fraction of a second before I'm voltage limited so the current doesn't mean anything and power drops off very quickly. I will be using 240-300V in the end so my voltage problem should go away.

If you are considering 72v of lithium, I would recommend trying to drive your truck on 84v of lead (to compensate a little for sag and weight) if you are happy with the performance on 84v of lead you'll be fine with 72v of lithium, otherwise strongly consider 120-144v of lithium, even if you have to use smaller cells to fit your budget.


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## charliehorse55 (Sep 23, 2011)

The Zilla can handle up to 400V input, so you could start with 144V @ 100AH now, and then add another 144V 100AH pack in series to give you around 300V nominal.


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## dtbaker (Jan 5, 2008)

hans j said:


> Anyone have experience with a 2000 pound 72v car? Other specs are Zilla Z1k, low RR tires, 4speed clutched trans and 8 inch ADC motor.


my suzuki swift (just about 2000# stock curb weight) started as a 96v lead-acid build weighing in at almost 2600#. (wimpy) Curtis 1221c and ADC 8" motor. It was 'ok', but pretty lethargic. Got 35-40 miles max range for about 12 months, but by 18 months and 7000 or so miles the range diminished to a questionable and saggy 25.

I upgraded to 120v x 100ah (38 cells) Thundersky, and it made a world of difference. Zappy is VERY drivable and I've got a 50 mile range, although I usually drive less than 25 on any given day... weight is down to 2020#, brakes and handling are much better.

I would NOT recommend starting with lower voltage, and would not recommend adding more a year later if you can help it... save up, or borrow money, and go with the full configuration.


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## dougingraham (Jul 26, 2011)

hans j said:


> This is basically my plan except using 200ah batteries. I would like to do a higher voltage but that would mean a new controller and motor adding to the expense.
> 
> I searched again on evalbums for cars similar to mine and found a couple nearly exact builds. The original builder of my car first listed a 40 mile expected range with the us125 batteries. He was getting 30 miles out of two strings of Optima yellow tops. A couple cars are claiming almost 60 miles in the same little pickup with the same us125 batteries.
> 
> I still plan on doing a lot of aerodynamic improvement to the car. Have a lightweight tonneau cover I need to finish, salt flat discs on the wheels and going to do a mostly full belly pan and wheel well liners to reduce drag. I have been shaving weight where I can too.


My suggestion was 144V of 100AH now and add another 144V of 100AH next year paralleling (buddy pack) the individual cells to give you 200AH later. I suspect you wont feel the need to do this as performance and range will be better than you have ever seen with just the 100AH.

200AH of Lead is about the same as 100AH of lithium at the same voltage except the lithium weighs a lot less. And the lithium should last 2 to 3 times longer at least. So it is a triple win.


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## EVfun (Mar 14, 2010)

The Zilla comes in several models, with a maximum pack voltage ranging from 156 to 348 volts. 400 volts is the absolute maximum input (*Do Not Exceed*) for the -EHV models. I have a Zilla Z1k-LV (156 volt pack maximum) and a Zilla Z1k-HV (300 volt pack maximum.) 

The -HV is currently in the buggy, running at 102 volts (32 cell LiFePO4 pack.) I can say that dropping from 120 volts of Optimas down to 102 volts put a dent in the freeway flexibility. With the Zilla replacing the Curtis the Buggy is startling around town, even with the lower voltage pack. I used to run down the freeway in 3rd gear at around 4200 rpm with the Prestolite MTC-4001 motor. Now I find that to be nearly the top speed in 3rd, so 4th is typically used on the freeway at about 3200 rpm. It will still do it, but if I had more range I would be concerned about over heating the motor. You really want to meet your freeway power with as much rpm as possible (highest possible motor voltage) to keep the amps lower.

Range is measured by how many watt hours of power you have stored on-board. Watts are volts times amps. The range for a 72 volt 200 amp hour pack should be nearly identical to the range for a 144 volt 100 amp hour pack. Often, the slight range advantage goes to the higher voltage pack since it help reduce resistive losses.



charliehorse55 said:


> The Zilla can handle up to 400V input, so you could start with 144V @ 100AH now, and then add another 144V 100AH pack in series to give you around 300V nominal.


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## hans j (Mar 31, 2008)

dougingraham said:


> 200AH of Lead is about the same as 100AH of lithium at the same voltage except the lithium weighs a lot less. And the lithium should last 2 to 3 times longer at least. So it is a triple win.


I keep on forgetting that... The price for the 100ah is basically half the 200ah so I can afford the full 144v pack of 100ah when it comes time to replace it, but that higher ah is just so tempting. But definitely the lighter weight will be my biggest increase in distance! Shedding 1000 pounds and gaining 24 volts while I am at it.

My main goal with my EV is to be able to drive up to the ski resort. About 26 miles from my house with the last 16 miles gaining about 3500 feet in elevation. pretty much all down hill and if I had to I could find a place to charge up there.

My Zilla is a LV, (#003 even) with a Hairball 1 (#014). I thought I had read they would only handle 144v max but even if it can do 156v, I really question whether my 8" ADC can. I have read of people going 144v on that motor at least.

Thanks for the info guys, keep it coming.


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## EVfun (Mar 14, 2010)

I take it yours is one of the early Zillas with a separate hairball and precharge unit? The very early units may have had slightly different specs, so I would inquire with Otmar at Cafe Electric before going over 144 volts. Mine are newer, January '08 and March '09 units.


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## steven4601 (Nov 11, 2010)

Look on the bright side, 3500 feet worth of regeneration when going back!

I only know metrics, but entering some numbers resolves this
mass = 1500kg (~3000pounds?)
earth-g = 9.8m/s
height = 1000meters
E = mass * earth-g * height

= 4083 watt/hours of energy needed or added to the vehicle vertical potential. (assuming no extra losses)

if your going with 100Ah @ 144v without regeneration you will be able to climb it 3 times if there are no losses . 
with regeneration that would largely depend on the losses only.


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## EVfun (Mar 14, 2010)

I see the need for about 48, 200 amp hour Lithium cells to do this 35 mile trip and return. Here is how I get there:

35 miles at 350 watt hours per mile (not bad for a pickup EV)
Steven is suggesting I add 4083 watt hours for the climb
A Zilla doesn't do regen so you are getting none of that back
That is a total of 28,583 watt hours
48 cells at 3 volts under load times 200 amps hours equals 28,800 watt hours on board.


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## hans j (Mar 31, 2008)

I think what Steven was saying it that theoretically it should only take 4083 watt hours to do the actual climb. I would like to believe it but I just don't see it happening. My current pack is 120v 240ah which does equal 28,800 watt hours but it's just not going to happen on this pack and really don't see it happening on a brand new set of floodies.

If Li-Ion ah is nearly twice that of FLA, then the 100 ah pack would be very similar, but weigh 1000 pounds less (much less weight to haul up the hill). I don't have any good way to measure w/mile but the original builder was measuring 250w/m and I am figuring about 300w/m. It's a VW rabbit with a truck bed on the back. This is the original evalbum page: http://www.evalbum.com/3484 

I can still get a little bit of weight out of it by changing the bumpers to aluminum and my old charger is pretty heavy too, but I am just about maxed out on reductions. Future battery racks will be made of aluminum too.


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## EVfun (Mar 14, 2010)

With lead acid batteries you cannot use all 240 amp hours at EV rates due to Peukert's effect. Nawaz Qureshi at USBattery used to be quite supportive of EVs (I have no idea if he even works at USB anymore) and estimated that at EV rates about 57% of the listed capacity of a golf cart battery is available. That indicates that your 120 volt pack of lead has about 16,400 watt hours available.


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## dtbaker (Jan 5, 2008)

EVfun said:


> With lead acid batteries you cannot use all 240 amp hours at EV rates due to Peukert's effect. Nawaz Qureshi at USBattery used to be quite supportive of EVs (I have no idea if he even works at USB anymore) and estimated that at EV rates about 57% of the listed capacity of a golf cart battery is available. That indicates that your 120 volt pack of lead has about 16,400 watt hours available.



I'd say that is not a bad estimate... I used usbattery 8v x 12 for a 96v system. 20-hr rate was like 185ahr or something like that. under BEST conditions after break-in I got maybe 38 mile range. If you extended their curves, my best guess is that the 1-hr rate for the usgc8vhcx would be right around 100ah useful, but sagging probably.

with 120v x 100ah of LiFePO4 (thundersky) I'm at 50%DOD at 25-30ish miles, so could squeeze out 50 if I were willing to go that deep. I have not gone further than 40 miles, and that took about 80 ah according to CycleAnalyst.


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