# Warp 9 high voltage/low current or low voltage/high current??



## nzev (Nov 20, 2008)

We're looking at building an EV, we're selecting a battery pack size of 
about 20Kw/Hrs to give us the range we want.

We're wanting to know if the Warp 9" is best suited for a low Voltage/high 
current, or high Voltage/low current?

We could run 60x 100Ah Thundersky Batteries giving us a peak voltage of 192 Volts or 40x 160Ah cells, giving us a peak voltage of 128volts, which would you recommend??

We are wanting to build a performance EV not a slow turd......

Cheers

Simon Wilkinson
New Zealand


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## EVfun (Mar 14, 2010)

Higher voltage. I believe that the Warp 9 has nearly the same torque/amp curve as the ADC 9. The ADC 9 makes quite a bit of torque per amp so it doesn't make as many RPMs per volt. The ADC 9 inch makes 80 ft/lb. of torque at 400 amps while the smaller ADC 8 inch makes only 64 ft/lb. at 400 amps (the 8 inch is happier than the 9 inch on 96 to 132 volt cars.)

Horsepower = amps * volts * efficiency / 746
Horsepower = torque * rpm / 5252

(torque in ft/lb. and efficiency percentage expressed in decimal form)


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## nzev (Nov 20, 2008)

The recommended operating voltage for the Warp 9 or 11 is 150-160volts, with a maxium of 170 volts.....


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## evlowrider (Jul 23, 2009)

I choose to get 48 skyenergy cells (120AH) for a nominal voltage of 156V. I have a warp 9. 144V seemed to be the norm wit a few ppl going to 156V, I havent seen anyone go higher than that with a stock warp9.

Can't tell u how it goes yet, still building.

Pete.


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## Tesseract (Sep 27, 2008)

nzev said:


> We're looking at building an EV, we're selecting a battery pack size of
> about 20Kw/Hrs to give us the range we want.
> 
> We're wanting to know if the Warp 9" is best suited for a low Voltage/high
> ...



Keep this simple rule of thumb in mind: acceleration from a stop requires AMPS; go faster on the highway requires VOLTS. I would say for a modern conversion that ends up weighing 1000-1500kg you will want 750A+ of motor current for brisk acceleration from stops and a pack voltage of 156V to 192V to reach real highway speeds (that is, 120km/h, not barely hitting 100km/h).

The WarP 9 is in imminent danger of zorching (commutation failure) at as low as 100V if the current is also at 1000A, so the maximum recommended voltage of 170V probably assumes a much lower motor current (after all, the most popular controller available at the time the WarP 9 was released was the 500A Curtis 1231C). Conversely, motors wound for a high voltage and with neutral brush timing and interpoles, like the Kostov's and the new WarP 11HV, will prefer running at a higher voltage and less current (e.g. - higher RPM, lower torque).

Addressing your question more specifically...

Fellow forum member Dimitri has the second lowest pack voltage for a Soliton1 installation - 40 x 160Ah LFP pack (128V nominal) - and he routinely drives on the highway, but he has also said he'd like to have a few more cells. 

The lowest pack voltage Soliton1 customer is running 72V x 220Ah in a MGB... acceleration is fine, but honestly, that's just too low a voltage for even a small, light car.

So, given all that, I'd go with a 50 x 160Ah pack so you have 20.5kWh worth of usable energy and 20% in reserve (for best cell life). Going with a larger number of lower Ah cells - at least ThunderSky ones - doesn't seem to be a good trade-off because you have to limit battery current to 2C, maybe 2.5C, if you want to avoid swelling problems.


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## Guest (Mar 21, 2010)

Your rules of thumb are pretty much on, but I'd like to chimb in that this is kind of a variable thing.

We have a 2190 lb speedster. It has a significantly lower voltage than Dmitri's at about 120 volts. I see right about 300 amps cruising at 65 and if I accelerate strongly it goes to 540 amps. This is two strings of 36 TS 90Ah cells.

The advisory I saw from Netgain was 192v top voltage and it was entirely about commutator/brush arcing.

It's a hardy motor. The chart shows 72v and 324 amps or thereabouts from memory. In "general" you can go up in voltage and down in amperage from there. But of course for short bursts, we know of reports of 1000+ amps.

At 120v, my torque is severely diminished above about 4000 rpm and really starts to decline at anything over 3200. But we can do 95mph top speed at 120v, so it kind of widely depends on weight and gearing as well.

In Speedster Part Duh, we have gone to higher gearing, a 3.44 Ring and Pinion and a fourth gear of 0.70. The Speedster really only needs two gears, 3rd and 4th with that top speed of 95. By going to the higher gearing in the Part Duh version, I'm hoping to get 3 gears in the game, and increase the top end to 110 mph. I don't really need to go that fast, but that was the spec on the original 1957 356A.

Again, we'll be at 36 x 180Ah for 120 volts. But of course in Speedster Part Duh we're moving to the HPGC AC-50 AC induction motor. It will be interesting to see how they compare. 

My intent is to then run them both on a chassis dynamometer to get real numbers at all RPMS and draw a curve of the results.

Jack Rickard
http://evtv.me


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## nzev (Nov 20, 2008)

An email reply from Jim Husted from Hi Torque Electric........

Hey Simon

In as much as the Warp9's have a voltage limit of 170 volts I'd go with the higher voltage and limit it to 170 volts. They'll take a full punch from a Zilla2k (limited to 170 volts to motor) with the weakest link being the brush leads. Keep an eye on heat to make sure you're not over-taxing it with to many high amp takeoffs to frequently. You'll probably net about a 25% increase in power at the higher voltage.
Jim


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## nzev (Nov 20, 2008)

An email reply from George Hamstra (from the manufacturers, Netgain )........


Simon,

Tough questions.... as high/low are relative... I am not a "battery 
guy" either, so this is what I would suggest:

 Determine the min charge voltage of your pack to be around the 
maximum motor voltage. In other words, if the motor is going to be run 
at 160 Volts (good voltage for the motors), then when you pack is 
discharged it should be slightly above this voltage - so you don;t 
damage the batteries by taking them too low - Lithium packs are expensive...

So, if each cell has a fully charged voltage of 4.0 volts and a 
fully discharged voltage of 3.0 volts, you would need 54 cells to 
provide 162 volts when discharged, or 216 when fully charged.

Volts = RPMs, Amps = Torque

Hope this helps!

George


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## nzev (Nov 20, 2008)

Hi Jack, do you mean you cruise at 100amps, not 300amps (i would hope anyway)


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## Guest (Mar 22, 2010)

nzev said:


> Hi Jack, do you mean you cruise at 100amps, not 300amps (i would hope anyway)


At about 70 mph, we're pulling 280-300 amps I would say. NOT 100 amps. But we are significantly lower in voltage as well - probably seeing 112v at that point. 

The cells never operate at 4.00 volts. The "fully charged" voltage on LiFePo4 cells is 3.400 v. We charge to 3.65 v average across the pack and wind up at about 3.34 or 3.35 v per cell.

One of the things i have simply FAILED to convey to the BMS guys, is that these cells sag in voltage under load. I just got a SECOND 1500 watt load and can gang them now for 3000watts. I put a four cell TS 90Ah bank on it and loaded to 200 amps. The voltage of all four cells drove to about 2.8v. These are FULLY CHARGED cells.

So I've seen pack voltages of 100v on my 120v pack at 540 amps. Not unusual, but it would wreck totally all the low voltage monitoring circuits these guys are working on. 

But yes, 300 amps. Not 100 amps.

Jack Rickard


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## Matthijs (Jun 19, 2009)

jrickard said:


> At about 70 mph, we're pulling 280-300 amps I would say. NOT 100 amps...Jack Rickard


Most members here with some real world TS battery experience advice that a pack should be planned for 1C or less cruising with acceleration less than 3C. Knowing that you have extensive knowledge on these cells and driving the Speedster for a year now what do you think about this? Do you trust the specsheet of TS cells and their cycle life claims with your 3.3C discharge at cruising speed?


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## Guest (Mar 22, 2010)

Matthijs said:


> Most members here with some real world TS battery experience advice that a pack should be planned for 1C or less cruising with acceleration less than 3C. Knowing that you have extensive knowledge on these cells and driving the Speedster for a year now what do you think about this? Do you trust the specsheet of TS cells and their cycle life claims with your 3.3C discharge at cruising speed?


I think it is total bullshit generated by too much typing at each other. 

I know the source of it. I have corresponded with him. He should know better. But he is VERY good about devoting time to these forums and a just awe inspiring amount of disinformation based on total fabrication. 

I ROUTINELY and DAILY do 3C. I would do 4C if they would do it. It doesn't harm them whatsoever. I kind of get the idea they like it.

Jack Rickard
http://EVTV.me


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## DIGGER11 (Mar 16, 2010)

So at a discharge voltage of 2.8v, I should use about 52 TS LiFePO4's to ensure that I don't go below 144v for my Warp 9???
This would give 166v at 3.2v which is the cells theoretical voltage.

If say, I could fit in another 10 cells, and the speed contoller limited the voltage to say 166v, would there be any benefit to do this ? As I would be voltage and current limited by my 500A Curtis anyway ?????


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## Guest (Mar 23, 2010)

DIGGER11 said:


> So at a discharge voltage of 2.8v, I should use about 52 TS LiFePO4's to ensure that I don't go below 144v for my Warp 9???
> This would give 166v at 3.2v which is the cells theoretical voltage.
> 
> If say, I could fit in another 10 cells, and the speed contoller limited the voltage to say 166v, would there be any benefit to do this ? As I would be voltage and current limited by my 500A Curtis anyway ?????


With 52 TS cells, not the new LiFeYPo4 but the cells I have used, you would charge to 3.65 v per cell for 189.8 v. After charging, the pack would settle to an initial voltage of 3.35 per cell or 174.2. At a 2C discharge rate, they would indeed sag to about 2.8v or 145.6v.

Jack Rickard
http://EVTV.me


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## Tesseract (Sep 27, 2008)

DIGGER11 said:


> ...
> If say, I could fit in another 10 cells, and the speed contoller limited the voltage to say 166v, would there be any benefit to do this ? As I would be voltage and current limited by my *500A Curtis* anyway ?????


IF your speed controller could do that, then yes. But the Curtis can't. In fact, the Curtis isn't going to much like seeing more than 160V or so at its B+ and B- terminals (i.e. - fully charged 12 x 12V lead-acid pack) and it is does not have any internal provisions to protect itself against such an occurrence.

In other words, don't do this.


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