EV Conversion Research

Open for any sort of non-technical discussion regarding EVs
Post Reply
PepePepeson
Noobie
Posts: 6
Joined: Thu, 20 Dec 2012, 03:35
Real Name: Nathan
Location: Brisbane

EV Conversion Research

Post by PepePepeson » Fri, 21 Dec 2012, 13:53

Hi

I've just recently started researching doing an EV conversion with a friend that I work with. The goal will be to have a car that I can drive to pick him up and then drive us both to the station each day for work. I also can't imagine why it can't be used for quick trips on the weekend if needed.

We would like to keep the cost down, so I'm thinking lead-acid batteries, which I know are bigger and heavier per kW or V or Ah.

Which brings me to my point! ;p

Choosing a donor car.

Does anyone have any reasonable resources for finding the weight and GVM of cars? I've had a search around for a while this morning and can't find anything useful.

I'd like to be able to take the kerb weight, remove some ICE weight and work out how much weight I have to play with for the electronics. Basically to work out if a particular car is suitable as I'm looking at all cheap donor options at the moment.

Thanks!
Pepe.

User avatar
evric
Site Admin
Posts: 500
Joined: Sun, 20 Jul 2008, 01:57
Real Name: Eric
Location: Adelaide SA
Contact:

EV Conversion Research

Post by evric » Fri, 21 Dec 2012, 14:07

Hi Pepe,
Just a word regarding Lead Acid batteries in EVs.
Basically they are not really suited to EVs.
Most people who start off this way usually, within 18 months, change over to LiFePO4. The lead acid batteries deteriorate fast due the the fact that they cannot supply the large currents required for long periods.

My advise is to save a bit more money initially and put in the Lithium batteries first off. This will also save you remaking the battery boxes.
Prius Plug-in Conversion: http://www.evplus.com.au ...Holden Barina EV: http://www.evric.kestar.com.au

User avatar
coulomb
Site Admin
Posts: 3779
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

EV Conversion Research

Post by coulomb » Fri, 21 Dec 2012, 14:19

PepePepeson wrote: Hi
Welcome!
Does anyone have any reasonable resources for finding the weight and GVM of cars?
There doesn't seem to be much money in car research, so the information is a little hard to find at times.

I often use the online car sales sites, e.g.

http://www.carsales.com.au/car-research ... earch.aspx

I think a lot of them use Redbook for their data, so you can cut out the middle man, so to speak:

http://www.redbook.com.au/cars/research

But the sales sites are also useful for getting an idea how common a candidate donor vehicle is, and what you might have to pay for it. In fact, that site may lead you to actually buying the donor.
I'd like to be able to take the kerb weight, remove some ICE weight and work out how much weight I have to play with ...
Yes, but unfortunately ICE weight isn't something you often see. 200 kg for a medium sized car (e.g. Corolla) including all the gear (fuel tank, exhaust, radiator etc) is a starting point. Note that the ICE for a smaller car could be a lot less than that.

For a cheapie, you'll likely be wanting a cheap motor, so you should read at least a part of this sort of thread:

Using a forklift motor, and choosing a good one (from DIYelectriccar, a more American focused forum, but still with good information). Warning: this is a huge thread, with many posts of the form "I just found this at the tip, is it any good?". So you need to pick and choose what parts to read.

Good luck!

[ Edit: added warning re thread size ]
Last edited by coulomb on Fri, 21 Dec 2012, 03:25, edited 1 time in total.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

User avatar
Johny
Senior Member
Posts: 3729
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

EV Conversion Research

Post by Johny » Fri, 21 Dec 2012, 14:25

PepePepeson wrote:The goal will be to have a car that I can drive to pick him up and then drive us both to the station each day for work.
About what range would you require Pepe?

PepePepeson
Noobie
Posts: 6
Joined: Thu, 20 Dec 2012, 03:35
Real Name: Nathan
Location: Brisbane

EV Conversion Research

Post by PepePepeson » Fri, 21 Dec 2012, 15:12

evric wrote:Just a word regarding Lead Acid batteries in EVs.

Thanks for the info. I've just started my research, and one area that's probably lagging behind the others is batteries. I might have to look into second hand lithiums.

coulomb wrote: I often use the online car sales sites, e.g.


Thanks. It did cross my mind, but I'll take a look, and also take another look at RedBook. Perhaps it was just the particular car I checked that didn't have any details.

I have looked around for second hand forklift motors, but there's bugger all available. Guess I'll need to call some places and do a bit more legwork before I rule that out, though.

Johny wrote:About what range would you require Pepe?
It's just under 25km each way, so 50km round trip.

So if I aim for a set up with a range of 100-120km, that should help the batteries last a reasonable amount of time.

Tritium_James
Senior Member
Posts: 683
Joined: Wed, 04 Mar 2009, 17:15
Real Name: James Kennedy
Contact:

EV Conversion Research

Post by Tritium_James » Fri, 21 Dec 2012, 15:28

A decent rule of thumb regarding weight is: by the time you've taken out the petrol engine, exhaust, fuel tank, etc, and then put in your electric motor, electronics, cabling, fuses, empty battery boxes, etc, you'll be back at the original weight of the car. Then add the weight of your batteries.

Yes, it's possible to do better than this - but don't count on it!

User avatar
Johny
Senior Member
Posts: 3729
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

EV Conversion Research

Post by Johny » Fri, 21 Dec 2012, 15:49

PepePepeson wrote:It's just under 25km each way, so 50km round trip.
OK. Mine weighs about 1080kg and gets about 142 Wh/km battery to wheels - with regen braking and at 70 to 80km/h. If you remove 10% for regen and add some weight you could probably estimate about 180 Wh/km.
For 50km you would need 9 usable kW/h. With lead that would need almost double that in pack capacity - a 16 to 18kW/h pack - and that just squeaks it in. If you want to travel faster than 70-80km/h you'll need a heap more capacity as well.

PepePepeson
Noobie
Posts: 6
Joined: Thu, 20 Dec 2012, 03:35
Real Name: Nathan
Location: Brisbane

EV Conversion Research

Post by PepePepeson » Fri, 21 Dec 2012, 17:08

Johny wrote:OK. Mine weighs about 1080kg and gets about 142 Wh/km battery to wheels - with regen braking and at 70 to 80km/h. If you remove 10% for regen and add some weight you could probably estimate about 180 Wh/km.
For 50km you would need 9 usable kW/h. With lead that would need almost double that in pack capacity - a 16 to 18kW/h pack - and that just squeaks it in. If you want to travel faster than 70-80km/h you'll need a heap more capacity as well.
Thanks for the info/calculations.

One question though, how do I convert kWh to ampere, or a way for me to work out how many physical batteries I need to make a pack of a certain size?

User avatar
Johny
Senior Member
Posts: 3729
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

EV Conversion Research

Post by Johny » Fri, 21 Dec 2012, 17:14

PepePepeson wrote: One question though, how do I convert kWh to ampere, or a way for me to work out how many physical batteries I need to make a pack of a certain size?
Just divide by your nominal pack voltage. So if you had 12 of 12V batteries making 144 Volts - divide say 16000 (16kw/h) by 144 -> requiring 111AH usable. Look up peukert factor for Lead acid to see what I'm driving at re usable.
Here's a wiki link:
http://en.wikipedia.org/wiki/Peukert%27s_law

User avatar
Johny
Senior Member
Posts: 3729
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

EV Conversion Research

Post by Johny » Fri, 21 Dec 2012, 17:15

Johny wrote:
PepePepeson wrote: One question though, how do I convert kWh to ampere, or a way for me to work out how many physical batteries I need to make a pack of a certain size?
Just divide Wh by your nominal pack voltage. So if you had 12 of 12V batteries making 144 Volts - divide say 16000 (16kw/h) by 144 -> requiring 111AH usable. Look up peukert factor for Lead acid to see what I'm driving at re usable.
Here's a wiki link:
http://en.wikipedia.org/wiki/Peukert%27s_law

User avatar
4Springs
Senior Member
Posts: 568
Joined: Thu, 23 Dec 2010, 01:14
Real Name: Christopher Walkden
Location: Selbourne, TAS

EV Conversion Research

Post by 4Springs » Fri, 21 Dec 2012, 17:16

Hello Pepe, my car (see the 4Springs' Brumby thread) is similar to your requirements, so I thought I'd add my 2 cents worth.

My lead-acid battery pack gets me 50km range. This is with 140AH @ 144V = 20kW nominal. As Johny said, the 140AH that the battery manufacturers quote needs to be about halved for EV use. I get 50km range over certain terrain, driving slowly (60kph), which uses about 13kW. This is a bit more than Johny's 9kW, probably because my car is heavy and not very aerodynamic.
Having said that, I would not use lead-acid if I wanted to go 50km very often. Lead-acid does not like to be flattened, so you would want a larger battery pack than mine. At 500kg, my battery pack is very large already. I can only carry it because I used a ute, which has a GVM somewhat larger than most vehicles that size.
The reason I went for lead-acid was to get some experience under my belt. I wanted to prove the concept without laying out quite so much cash (and time) upfront. Now that I have a working EV which is useful and fun to drive (even the wife uses it in preference to the other cars!), I will put effort into researching my new lithium battery pack.

James' rule of thumb regarding weight certainly applied to my car (EV - batteries = original weight). I was surprised just how light everything was - 100kg for a 4 cylinder engine!

You may also investigate the idea of charging at or near the station. I have found businesses and councils very helpful, even offering free electricity! If you could get your range requirement down to 25km then the vehicle could be very cheap to put together.

PepePepeson
Noobie
Posts: 6
Joined: Thu, 20 Dec 2012, 03:35
Real Name: Nathan
Location: Brisbane

EV Conversion Research

Post by PepePepeson » Sat, 22 Dec 2012, 03:36

Some more food for thought, thanks everyone. There's a government building within a few meters of the parking, so I wonder if they'd be interested in loaning some kWhs.

Looking forward to having some time to read through your Brumby thread, 4Springs.

Thank you to everyone for sharing your experiences, no doubt it will save us much valuable time and effort as we proceed.

Cheers,
Pepe.

PepePepeson
Noobie
Posts: 6
Joined: Thu, 20 Dec 2012, 03:35
Real Name: Nathan
Location: Brisbane

EV Conversion Research

Post by PepePepeson » Sat, 22 Dec 2012, 21:42

Considering the range we were hoping for pretty much requires a ute or LiFePO4s, I'll look for ute donors and the possibility of doing two 65-70kph EVs. One with a range of 10km, one with a range of 20km.


zeva
Senior Member
Posts: 422
Joined: Sat, 15 Dec 2007, 05:09
Real Name: Ian Hooper
Location: Australia
MSN: sigmunky@hotmail.com
Contact:

EV Conversion Research

Post by zeva » Sat, 22 Dec 2012, 22:17

To throw another spanner in the works.. there is a problem with running a battery pack sized for only short driving range: The smaller your battery pack is, the harder it has to work (proportionately) to drive your vehicle.

Generally the most economical cells around (say flooded lead acids, or large format prismatic lithiums) can only sustain about 1C continuous without hurting their service life, which means they shouldn't be discharged full to empty in less than one hour of driving. So for battery pack of such cells sized for 20km range, you'd have to stay below 20km/h to avoid overworking the batteries!

For a short range vehicle, your best option may be to use slightly more powerful cells such as Headways, which can sustain 2C continuous comfortably enough. Although the cells are a bit more expensive by capacity, it may be the cheapest option overall.

Also FWIW, LiFePO4s are the most economical option in the long run since their cycle life is 5-10x higher than lead acid batteries.
Ian Hooper
--
"Never doubt that the work of a small group of thoughtful, committed citizens can change the world." - Margaret Mead
http://www.zeva.com.au

User avatar
Jeff Owen
Groupie
Posts: 157
Joined: Thu, 13 Nov 2008, 15:53
Real Name: Jeff Owen
Location: Brisbane

EV Conversion Research

Post by Jeff Owen » Sat, 22 Dec 2012, 23:06

Pepe
Do you attend the AEVA Brisbane branch meetings?
What area of Brisbane do you intend to drive the car?

PepePepeson
Noobie
Posts: 6
Joined: Thu, 20 Dec 2012, 03:35
Real Name: Nathan
Location: Brisbane

EV Conversion Research

Post by PepePepeson » Sun, 23 Dec 2012, 01:05

Haha! Thanks, zeva. Good to know. What about a bigger battery pack and only use 20% of it?

Hi Jeff, I haven't been to a meeting, but would be interesting to attend. I lie in Goodna, so west side of Brisbane.

User avatar
Simon
Senior Member
Posts: 431
Joined: Sun, 19 Aug 2007, 19:38
Real Name: Simon
Location: Perth WA
Contact:

EV Conversion Research

Post by Simon » Sun, 23 Dec 2012, 01:37

It's best to get the biggest capacity pack you can afford. My first lead acid agm pack only lasted 9500km before it couldn't give me the range I needed.
The current Lithium pack is still very small for a car (only 6.5Kwh) but gives me over double the range of the original lead acid battery. Even though 95% of the time I only use 30-40% of my tiny pack's capacity in a day there are still times I wish had got a 10Kwh pack that would let me go further on the odd occasion. But at the time I decided it wasn't worth spending the extra $.

User avatar
mjcrow
Groupie
Posts: 87
Joined: Tue, 22 Apr 2008, 06:11
Real Name: Michael Crowley
Location: Adelaide

EV Conversion Research

Post by mjcrow » Mon, 24 Dec 2012, 18:10

Engine weight table here http://fixrambler.com/engineweightchart.txt it's American and a little out of date but might be useful Image
Last edited by mjcrow on Mon, 24 Dec 2012, 07:12, edited 1 time in total.

Post Reply