Step Twelve - Creating the Battery Racks

This is the next step in the conversion process and is so far the most brain stressing, trying to fit twelve heavy little cubes into an odd shaped metal & glass box (batteries into a car). Before I can build the racks to hold the batteries, I need to know which batteries I'll be using.

After a few weeks of stressing and annoying battery dealers with quote requests I have decided which batteries to use. It's a big moment in the conversion process but now that I know the details I can start building the battery racks!

I wanted to use Hella Endurant MDC27/105 batteries, rated at 105A/hrs and 575 Cold Cranking Amps (taken at 0°F or -18°C). More realistically on a hot summers day this will be closer to 940 Warm Cranking Amps (80°F or 26°C). You can see what your own battery CCA rating would be like in real conditions here. It's interesting the difference that temperature makes. As long as these batteries fit, then I'll buy them!

More good news too - I've purchased my Curtis 1231C controller from EV America. These are very popular & reliable controllers with a maximum output of 500Amps at 144 Volts. As I'm using the FB1-4001A motor it should give me close to 60 horsepower (but with loads of torque!). Good stuff!

The dimensions of the MDC27/105 batteries are (length x width x height): 322mm x 171mm x 240mm and weighing in at 22 Kg each. For all my friends up in the USA currently scratching their heads that equals 12.6 inches x 6.73 inches x 9.44 inches and weighing 48 pounds each.

But first it's time to create the battery racks. I've hacked away with the angle grinder in the engine bay and cleared some space as you can see by the second photo at the bottom of the page. According to my cardboard mock ups this allows me to fit 5 batteries side-by-side in front of motor, and one behind the motor! That's 6 in the front, and 6 in the back! This was my plan before I even started the project which is just perfect! This layout will not only look organised, it'll allow the motor to be accessed/removed for any reason without removing all the batteries.

I've dropped the battery rack plans (photo 5 & 6) off to my trusty welding guy. My rear battery box will be mounted onto the boot floor.

While it's more common to mount the rear battery box into the boot floor instead of sitting on top of it I must stress that this is to be a simplicity-first electric car and anything too difficult will be removed from the plans! Besides, with the height of the battery box, it would be poking quite a bit through the floor anyway so I'm not bothered. If I don't like it, I'll pay someone to put the battery box into the floor.

I've got busy in the meantime installing the recharging socket where the gas cap used to be.

I apologise for the low quality photo in this picture. My digital camera's warranty recently expired so it's beginning to play up and puts lines in every photo!

You can see that the petrol cap is gone and in it's place there's the two ignition plugs & sockets I bought from Pick-A-Part in Auckland in video number eight. They're all wired up to the wealth of cables in the boot (photo at the bottom of the page) and will eventually feed two individual cables to each of the 12 batteries. How will it work you wonder? Ahh, it will all be explained when I create the charging system! You'll all have to wait a little for that one.

After two cold winter nights of soldering and taping, the recharging sockets & plugs are installed and ready to be hooked up.

During the socket install my vacuum pump arrived from Pete Papas in Florida. This fantastic guy threw in a vacuum switch and a couple of vacuum-locking valves along with the pump at absolutely no cost. I couldn't thank him enough - he's saved me almost $150 NZ! Thanks Pete!

I couldn't resist connecting the Thompson 12v vacuum pump up to a battery to see what it sounds like and whoah, those pumps are actually quite loud!

While waiting for the main battery racks to be created and installed, we've created a sturdy battery tray for the accessories battery and mounted it in a similar location to the previous battery.

This new battery tray allows the battery to sit right in the corner of the engine bay and out of the way. It all adds up to a tidier electric car.

I put newer, smaller main connectors onto the accessory battery also as the current draw won't be high anymore (no engine to start) and it'll be only used for the lights, indicators and wipers etc. We then used high strength metal strapping to secure the battery from lateral movement. It's a cheap and secure way to stop the battery from moving.

It really makes great use of that otherwise empty section of the engine bay (can I still call it an engine bay?).

I then installed a little fuse box that becomes live only when the ignition is on (via a relay attached to the ignition switch).

This fuse box allows me to connect things that I only want running when the ignition is on, such as the vacuum pump and the main contactor etc. In the photo on the left you can see I'd already hooked up the motor overheat buzzer.

This little buzzer puts out such a whopper of a noise for it's size that I had no concerns mounting it inside the engine bay. Hopefully it will never have to go off but it's good to know it's there.

All the spade-connections on the top of the fuse box become live when a fuse is connected. There should be plenty of space available for future connections. Anyone got any ideas of extra gadgets I could throw in there? :)

The next day I thought of an idea to shut up the noisy vacuum pump for the brakes - enclose it in a wooden box!

I had some pieces of board lying about in the garage so I measured (badly) some sections, screwed them together and made a box for the pump! Problem was, where on earth was I supposed to put it?

I tried a handful of places but this little vacuum pump is bigger than it looks.

In the end I decided to go with the space behind the passenger headlight, straight opposite the newly installed accessories battery. Rob popped over and we set about creating a new shelf on the other side of the car to hold the vacuum pump box.

After the shelf was installed, and after some redesigning and fine-tuning to the shape of the vacuum pump box, we got it to fit in the space behind the headlight - just!

We fired it up to test our work. What a difference! It's a lot quieter now.

The vacuum pump box looks like a bit like a wooden clog for space travel. I had to give it that weird shape to make it fit.

Still, it makes great use of an otherwise empty space.

At first the pump was going on and off constantly due to little leaks here & there. It took a while to get all the little leaks out of the system but now I have it pretty airtight. Once the system reaches optimum vacuum (20 seconds from normal atmospheric pressure) it stays there with no problems.

After it reached the appropriate vacuum I started timing it to make sure the pump didn't kick in. 30 minutes of waiting later I got bored and stopped timing it. It works well with no leaks now.

Another thing I ticked off the list while waiting for the battery racks was the installation of the recharging cables underneath the car. As you can see at the bottom of the page, the 12 smaller recharging cables for the 6 front batteries are installed under the car. They run from the "gas" cap to the front grille, ready for those big deep cycle batteries!

During the excitement of all of the above, a reporter from the local paper the Taranaki Midweek got in contact regarding the electric car and did a story about it. If you have 2 minutes for a light read, you can view the story by clicking here!

Finally! The day of the racks arrived after many weeks of waiting! However plans were about to be changed as good news and bad news both greeted me when my battery racks arrived at long last. Unfortunately the front rack which will have 5 batteries in a row refused to fit in. Having 5 side by side isn't the problem, that fits fine. The big problem is the length of the batteries. The rack was touching the front of the car frame, stopping me from getting it in by about 2cm (half an inch). Looks like my measurements were off by a tiny fraction, although I knew it would be super-tight anyway.

So I dropped the racks off first thing Monday morning to be reduced to fit smaller batteries. The biggest drawback to reducing the battery size is that the expected range of the car has decreased from about 70km to about 50km. While this doesn't pose a problem for our local driving distances, it doesn't sound as cool when telling people. On the plus side, the battery purchase will be a lot cheaper using smaller batteries.

In the meantime I received a quote on twelve Hella Endurant MDC24/85 Deep Cycle batteries. These are only 85 Amp-Hour batteries but on the plus side, they're cheaper and I'll remove 36 Kg (80 lbs) from the overall weight. The cold cranking rating of the smaller 85Ah batteries is rated at 515 CCA (or 844 warm cranking amps) so the performance of the car won't change luckily.

The smaller MDC27/85 batteries dimensions are (length x width x height): 276mm x 170mm x 240mm and weighing in at 19 Kg each. That equates to 10.86 inches x 6.73 inches x 9.44 inches and weighing 42 pounds each.

My battery racks were resized within the week and they fitted in perfectly.

The next task was to install the rear rack into the car. This was something I could do without welding as the rack was to be bolted in.

I wanted it to be secured so well that the vehicle inspector would be impressed. Considering the Tredia's tow-bar was secured with six bolts and the rear rack is secured by twenty six bolts I can't really see any problems myself... :)

It ended up taking most of the weekend but I drilled and bolted in the rear battery rack all by myself! 26 big bolts later the rack was installed!

You can see the underside of the car (and the 5mm thick steel plates holding the rack in) in the photos at the bottom of the page. There's no way this rack is going to budge in an accident. And it looks good too!

(Sigh) I can't begin to explain what a relief it is to get those things installed!

Now that the rear rack is bolted in it's time to finally get those (now resized) front racks installed.

My trusty welder arrived with an army of noisy saw-drill-spark-smoke making tools and got stuck into welding up the front racks ready for the batteries. He's used to working with restraint systems in cars and was confident that the racks are all installed much stronger than required by law. That should keep the EV inspector happy when it comes time to get the car legal.

The ultra-tough racks were resized and strongly welded in place to the chassis of the vehicle (not the sub-frame) to leave the crumple zones still able to crumple in an accident.

So after lots of delays regarding my battery choice, and delays due to battery rack design and subsequent fitment problems, I can finally breath easy.

Now that the racks are in, I'm off to the bank to borrow $2500 for the twelve Hella Endurant batteries.

While I'm waiting to hear if the bank loves me or not, it's time to install the components into the "control box".

You can also check out the video of the rack installation saga below. It's so much easier than reading the whole page. :)