Saturday, January 31, 2009

Front battery racks

I was going to post all of the battery rack and battery installation in one post but there is a lot involved and it's taking longer than I thought so figured I'd break it up some.

After reading through the Thundersky documentation I found on their website it said if you want to remove a cell from a group to discharge all the cells of the group first. Turns out these cells will expand and become ruined if they are used. It was hard to read the directly translated documents but it also sounded like you were fine if you recompressed the cells before use.

SinceI knew I needed groups of cells other than the five they came in I didn't hookup and start charging the cells immediately as I've noticed others doing because I didn't have a good way to discharge them again in a timely fashion.

I built a quick and simple cell compressor more for storing the od cells while I was waiting to build a new group. So for example I needed a group of seven which left three cells sitting around. I didn't know exactly how many cells I would need in each group and designed as I went (I'm bad at planning really far ahead).

Here is a new group of the seven cells. I got some huge zip ties and a tool to tension them. I noticed this actually is providing better tension than the stock setup. The stock setup is loose enough that the cells can still shift a little which allows them to get out of alignment. This method keeps the cells very snug. Below is also the first base frame for the group.

Another shot of the frame as I progressed. The batteries will sit on top of the motor mount and be allowed to move slightly with it.

The rack placed on top of the motor mount frame.

Here is a near completed battery rack holding three groups of seven cells above the motor. All three racks, especially the center are angled forward to account for the slope of the hood. There are very tight clearances all around between the sides and hood.

Just another shot from the front.

Here is the rack all painted. You'll notice I added some feet on the sides near the back. These, including the length of the rubber feet rivoted on, are 1/4" inches longer than the rest of the feet. This allows for all this weight to be evenly displaced downward on the engine mounts instead of only towards the center.

I can't remember the names of these things but they are basically a really long nut. They may be called couplers which is what they do. They are used throughout the racks with the threaded shafts to provide adjustable points for securing the cells as you'll see later.

Here is the rack bolted in place on the motor mount frame. Again notice those feet I mentioned earlier on the outsides of the motor mounts applying most of the weight to the outside and avoiding sag and strain.

Here are the 21 cells in place for a test fit. All looks good.
A final shot with the support bars securing the cells.

Now there is some room up front where the radiator use to be. Technically this isn't the best place for batteries. In case of an accident they are not as well protected and can be ruined during a front in collision. Of course so can the batteries over the motor if the crash is bad enough. Either way I don't have the room to pick and choose the locations so they are going in here.

After doing some measuring I determined I can squeeze nine cells in here. I changed my mind a couple times but then finally decided on the best way to secure the frame as well see in a second.

This rack needed to built in two pieces and bolted together to allow it to fit into the confined space and get to the mounted points.
Here is the front cross member which convienently had two bolt holes where the original engine stop was. This was the rubber bumper used to stop the engine from dropping too far down when you discount the tranny. I'll be using it as one of the main mounting points.

Here is a shot of the frame in place. I had to also drill holes in the side frame (unfortunately no other available holes).

Here are those side holes that were drilled. You can see these beems with the front bumper removed.

The finished assembly.

I installed the finished assembly. Things were so tight I couldn't help but scrapping a little of the paint. I hate that!

I wanted to add this picture since I forgot to mention it earlier. The white plastic sheet seen here was also used on the first three groups of cells to protect from anything that may come up from the road. The plastic is what is called wonder wall. It was thin, very hard and yet could bend without breaking. It was very lightweight and cheap so seemed worth trying out. When I get things rolling I plan to come back and build a lightweight shell around the batteries with this material. We'll see how that works out later.

One final shot with the 30 cells in the front of the car. This leaves another 15 to fit into the trunk.


Dimitri said...


excellent work, man!!! Looks great!!! I can't wait to get my hands on these batteries.

Anonymous said...

Do you think it´s a good idea to place the holder (yellow triangle bar) directly above the saftey vent of the cells?

Brian said...

That's an excellent point which I didn't consider. Those valves give access to a cavity that surrounds the battery. It contains simply water and is used to cool the intenral cell. If the cells become extremely over heated they are suppose to release the pressure, sadly this also means it's too late and you've damaged your cells. I have a BMS system which is monitoring the temps of the cells and it screams at me if they reach too high of a temperature so as long as I pay attention I should be safe. If I had thought of this before then I should have supported them on the edges.

Anonymous said...


interesting information about the "watercooling".
But I found no information about it on the Thundersky HP.
Do you have any ressources according to this feature?

Thank you very much in advance!

Markus (aka Anonymus post 2)

Brian said...

There is nothing that I've found on this officially. I learned this from the yahoo group for Thunder Sky batteries.

There was discussion on if these cells, as claimed, could truely be positioned in any orientation. The general consensus was that after a couple years some cells could start leaking the water out the vent cap. It was then explained that after this water leaked out the cell lost it's ability to cool and the over heating would create air pockets in the lithium cell and lead to greatly reduced cacpacity.

Brian said...

Here is a good post and picture showing the structure of the vent.

Since these vents are threaded the venting happens through the spring and diaphragm type object shown.

Looks like I'm good on my mounting style, thank goodness. :)

Anonymous said...

I don´t think it´s water.
It think this guy is right:

But your holder bar will not block the saftey valve, the spring could still open.
So I think you may only get problems when the cells produce a lot of gas.

Brian said...

The bar across is not solid and will still allow the venting. So even in that case I think it's good now after seeing that post.

California Lemon Law said...

Really excellent guide. Thanks for sharing. btw.. Before I can build the racks to hold the batteries, I need to know which batteries I'll be using.

California Lemon Law