Battery Vehicle Society

So, I'm finally getting things going for the lead to Lithium conversion for my City El.

I'm using 100AH Thundersky Lithium Ion cells which I got from Reap Systems. I'm also using Reap System's BMS unit. It will prevent the lithium cells from either going undervoltage or overvoltage. Unlike the Lead acid system the City El uses I have to wire in about thirty or more cables to various parts of the car and batteries to ensure that everything works as it ought.

I've chosen to use 12 cells, giving me a pack voltage around about 42 volts. I know the City El in it' stock format can handle this voltage without anything blowing and it should give me a bit of a performance increase over the original 36 V pack tension.

Here's a picture of the BMS:


It's a really compact unit and so I've decided to install it under my car's seat, where the original (but missing) capacity meter board would be. It also gives me a perfect cable tunnel between the under-seat and back of car area making sure my cabling is neat and tidy. When I'm done I hope you won't be able to tell it's been upgraded.

Because the BMS uses special plugs and has a special numbering system for the pinout I've decided to label each cable at both ends with a simple numbering pattern. For example, I've used V0 for the Voltage sense, negitave side, V1 for voltage sensor, Cell 1, etc etc.

It seems to be working at the moment and will enable me to solder another connector in place when I've got the cable installed in the car.



Tonight I've finished the voltage cable sensors (13 wires in total) and I've heat shrinked the entire lot together after checking the continuity of each wire. Hopefully with all the cables heat-shrinked together they will be a little more robust in the harsh environment of a car.

So, keep up to date for more progress. I'm really hoping to get the car ready for Sunday's Microcar rally near Bristol!

wow , that looks really great .

It won't be of any surprise at all to know I'm following this conversion with a lot of interest

If it's not too rude a question, what sort of financial outlay would be required ?

Well, see, I brought second-hand (or rather, new 'old' cells) which have been sitting a few years. They'll have a higher internal resistance than new ones, which work out at £1.20 per AH per cell. I needed 12 cells for my car

The BMS retails at about £500 if I remember correctly, but again, I've got a second hand one.

So yes, money and kind words!

I had a very productive day today. I finished off the loom to the voltage and temperature sensors as well as cutting the angle I'm using to keep the cells under compression.

. The City El has a really nice and easy-to find hole in the body panel for the brake lines and wires to pass through. If you take off the handbrake you can get to it I'm going to pass the loom through there on the way to the battery compartment.



I've also tried the fit of the mounting board that the BMS will sit in. It'll be tight but it should just fit (where the old capacity meter used to be).

I finished the binding of the cells into three packs of four cells (so they fit in the battery tray of the EL) and could compare them to the old Lead acid batteries I'm taking out.


It's surprising how much smaller they are. Without the 'fins' I've made up for compression they'd look even smaller. There's a good bit of space in the battery compartment for me to make up suitable insulation but I'm not decided yet weather to use some kind of insulating foam or not. I have polystyrene blocks which of course will help.

The test fit of the cells worked a treat too. There's a little less room width ways than I'd hoped for, but plenty of extra length.



Tomorrow I hope to start the other looms and also start work on fitting the display etc!

Wow! Impressive stuff. You've been busy, Nikki.

Thanks Mike!

Well, today has been insulating day with the cells.

Now normally of course you try to keep all your Lithium Ion cells in a nice warm compartment alltogether. But in the City el, where the batteries are normally 3*12V I had to concentrate on insulating the batteries in groups of 3*14 V (or four cells a piece).

By the time I'd put cell compression on to prevent the cells expanding I was a bit strapped for space. I was going to use polystyrene blocks but then after talking to Kelvin had a bit of a brainwave and decided to try and find some of the foil/foam/foil/foam/foil sandwiches that you can get to insulate attics etc.

I headed to B&Q and found out that the smallest they did these was in a huge roll at £170 a throw!

Luckily they sold a kit deisnged to let people insulate their garage. It was only £40 and was the perfect thing for my batteries.


Here's the box, so if anyone wants to do it they know what to look for. Apparently it insulates as well as 100mm of glass fibre insulation. I decided to use two layers.

[ur;=http://www.flickr.com/photos/aminorjourney/727565875/in/set-72157600628045492/][/url]
It was like wrapping up presents! secure each layer with tape and then use cable ties on the second layer to pull everything together I also taped things up from there to make it look neat.

. All three packs insulated and in position!

Now all I have to do is to finish the other parts of the loom and I should be in business!

Nikki.

So... I'm confused.

Where are you planning to put the 6 litre V12?

Outstanding !

At least you have had more succes than me recently, after spending the entire morning sanding down the battery tray out of my mini-el, then carefully washing it,drying it & cleaning it with "pre-paint" I went on to paint it.

After using Hammerite "rust inhibitor" grey primer followed by several top coats of black Hammerite I was a little unhappy at the finish. So I thought I would add another top coat of ordinary satin black - not a good idea after all. Reacts quite nicely giving a unique dimpled finish

I've walked away from it for tonight, I'll review the problem tomorrow to see if its back to square one or a "bodge it" salvage option!

With the battery tray you sadly have to be quite picky. You're bound to get acid spilling in there and all manner of lovely things.

You can buy galvanised ones, but that's probably pushing the boat out a little TOO far

Nikki you've got me confused, what are the fins for? I would expect them to be for heat dissapation but then you wrap them in insulation am I misising somthing?

Mark