# Planning Jaguar XJ build



## major (Apr 4, 2008)

itchyback said:


> Distance, 100kms in a 1700kg car using the 'sizing your battery' page seemed to suggest i would need 350Ah batteries, i thought my calculations were generous which is why i dialled it back to the 300Ah. Again, am i on the right path here because no one else seemed to have that many Ah's?


Hi itch,

Lot of questions. Hopefully other members will chime in. I'll start with this. Use Watt hours (Wh or kWh) to figure battery pack range, not Ah. That will give you accurate comparisons of different systems even when they have different voltage. Also helpful with range predictions is to use the energy usage in Watt hour/km (Wh/km) or Wh/mile. I had a nice drive in my little EV yesterday and got 250 Wh/mile. I can use up to about 24 kWh from my battery, so it gives me an absolute range of 96 miles. My drive was only 57 miles and I put in about 14 kWh to recharge it after I got home. BTW, I have a 70Ah battery pack 

Welcome to the forum,

major


----------



## evmetro (Apr 9, 2012)

Yeah, what major said about watt hours. I like to estimate the completed build weight so that I can use the standard 10% of weight in pounds = your watt hours per mile rule. A 5000 lb car should use roughly 500 watt hours per mile, a 2500 lb car should use about 250 watt hours per mile, etc. Once you have your estimate of how many watt hours your build will use, it is simple to multiply that number by the desired number of miles of range that you seek. If your car is going to average about 250 watt hour per mile and you want to have a 100 mile range, you would need 25 kwh after using 80% of your total energy. (25,000 watt hours, in case you are new to this, and 31.25 kwh total pack)
I am building a heavy Cadillac Eldorado right now and am using a 300ah pack, but the like major is saying, I used the 450 watt hours that my 4500 lb car will use and my desired range/budget to determine the amp hours of my pack.


----------



## itchyback (May 28, 2014)

Ah, thanks for the replies and help, i've obviously missed the volts and ah balance.
ok, 
so my car = 4000 pounds = 400wh/m x 60miles = 25Kwh x 1.2 = 30Kwh pack required
so i could get 144v x 200ah pack (medium speed)
or 48v x 600ah pack (slow)
or 250v x 120ah pack. (lightning quick)

With those figures my original calculation of 300Ah would have got me 100 miles at 144 volts which is cool, but not necessary. Although if my car gets heavier, 2000kg (4400pounds) than i would need the 144v x 300Ah batteries to get me the same distance.


----------



## arklan (Dec 10, 2012)

1700kg is about 3500 pounds
3500 pounds is roughly 350 watts per mile
100km is roughly 62 miles
350 watts per mile times 62 gives u a 21700 battery pack at 100% depth of discharge dod
21700 x 1.2 to give u the extra 20% so u use 80% of battery dod gives u a battery pack of 26040 watt hours
nominal voltage of ur being 144v
26040 divided by 144 gives u 180ah
assuming $1.35 per ah at 3.2v or 42.1c per watt, the pack will cost $24300 with lithiums and weigh 267kg
lead will cost between 5-10 times less and weigh 2-3 times more and u need to use 1.5 times more ah to get the same numbers
thats a pretty good size pack there, what would u be doing with the car?


----------



## Duncan (Dec 8, 2008)

arklan said:


> 1700kg is about 3500 pounds
> 3500 pounds is roughly 350 watts per mile
> 100km is roughly 62 miles
> 350 watts per mile times 62 gives u a 21700 battery pack at 100% depth of discharge dod
> ...


_

Fixing the numbers - looks a bit better! 

For that range Lead is basically impossible 
- you enter the death spiral 
- need more batteries 
- which makes the car heavier so you need more batteries

Effective max range on lead is about 40 miles
and at that 50% of the car's weight is lead - they don't call them "Lead Sleds" for nothing! 

Then you get the lead life problem - 18 month to 2 years - if you are lucky!_


----------



## itchyback (May 28, 2014)

I'd like to register the car in Australia and drive it as my daily wheels. 

Lead isn't really an option because the cars gvm (2100kg) cannot be exceeded under the registration requirements. 

I was looking at the transmission stuff this morning. Man that has done my head in. at this stage I just feel its so complicated - bugger the cost i'll go direct drive. Unfortunately the sky isnt the limit for $$. 
I saw some 2 speed transmissions which seem like an option. more reading to do before I understand this though.

What do you guys think of the motor/ transmission options?


----------



## donx03 (Nov 19, 2011)

ItchyBack,

There is a company called Epic Car Conversions which specializes in JAGUAR XJ conversions, BMW's, Porsche's, Toyota, Mazda, MG, Austin, VW, Subaru, you name it they have it.

Take a look at the attached photos & the following youtube video,

https://www.youtube.com/watch?v=wdDjFtZX0No

They can supply you with a complete custom conversion kit for your application with every nut & bolt to make your 1st time conversion a success.

You can email them directly,

Dan AT EpicCarConversions.com

-From what I hear they're car meets all your requirements.


----------

