openinverter forum

Great build!

What charger are you using?

bobbyj_408 wrote: ↑Fri May 14, 2021 4:15 am Great build!

What charger are you using?

Thanks! I'm starting with a TC 3.3 kW charger. If I drive the car frequently I may upgrade later.

rjmcdermott81 wrote: ↑Fri May 14, 2021 11:17 am Thanks! I'm starting with a TC 3.3 kW charger. If I drive the car frequently I may upgrade later.

Nice! Yeah that makes sense. I'm thinking the same for my build. Did you also buy that from ElectricGt?

bobbyj_408 wrote: ↑Fri May 14, 2021 1:38 pm

rjmcdermott81 wrote: ↑Fri May 14, 2021 11:17 am Thanks! I'm starting with a TC 3.3 kW charger. If I drive the car frequently I may upgrade later.

Nice! Yeah that makes sense. I'm thinking the same for my build. Did you also buy that from ElectricGt?

I did - price was good and I was already buying things from them so I went that route. They are super helpful.

More progress. I have the steel mounts in place for the top 3 batteries. (everything is just tack welded for now as I build out the whole box) Set in the car Placement of remaining batteries in the engine compartment

More progress before I head out of town for the next couple of days. The 4-battery box will be attached to the rest after I test fit it in the car.

Alright - 11 batteries placed so far with 5 more to go.

2 more in the bay which makes 13. 3 more to fit in the trans tunnel to get to 40+ kwh.
and the hood clears everything:

rjmcdermott81 wrote: ↑Tue May 18, 2021 2:22 am More progress before I head out of town for the next couple of days. The 4-battery box will be attached to the rest after I test fit it in the car.

Love these boxes!

Similar to our current approach. What about the big holes there, are your cells made watertight already so you don't have a watertight box or will that be covered?

Interesting modules as well, at first I thought you are doing a Lead/Acid build until I looked up the manufacturer.

janosch wrote: ↑Tue May 25, 2021 9:37 am

rjmcdermott81 wrote: ↑Tue May 18, 2021 2:22 am More progress before I head out of town for the next couple of days. The 4-battery box will be attached to the rest after I test fit it in the car.

Love these boxes!

Similar to our current approach. What about the big holes there, are your cells made watertight already so you don't have a watertight box or will that be covered?

Interesting modules as well, at first I thought you are doing a Lead/Acid build until I looked up the manufacturer.

The holes in the aluminum are for the fittings that will connect to the cooling plates that are sandwiched between the battery modules. You can see them in the picture below. Also, this is just the structural part of the battery box to support the batteries in place. After I have everything framed out and fit I plan to do final welding (it's just spot welded now) and then create a watertight exterior. I'm leaning toward fiberglass for the exterior with removable panels for easy assembly.

Alright, feeling positive. All 16 fit without changing anything on the car. So far the only modification to the car has been to cut out the spare tire well which could easily be put back.

Three batteries in the trans tunnel Here is the box back out of the car Next step is to make sure I can bolt all the batteries back with the cooling plates and hoses.

All good - everything fits. Finished the welds on everything

Since this is my first time, it has taken me a while to get all the mounts fabricated. I have everything together now and just need to clean things up. Most of the weight will fall on the motor mount points on the subframe in the center, then I have two mounts attached to the transmission mount in the trans tunnel with the stock bolts, and then the front sits on a cross member in the engine bay and is held in place with two small bolts.

k, I'm done working on the battery cage. I added thru-bolt holes and nuts that will allow me to secure the external shell and cleaned up the welds. Next up is painting and then I can start assembly.

Painting done - just a simple epoxy primer to protect everything.

Okay making progress on the exterior of the battery box. Aside from making fiberglass in the lab I don't really have much experience so I'm learning as I go. This is the bottom so I didn't spend a ton of time on aesthetics, when I work on the top of the box that will be visible I'll spend quite a bit more time on a mold. I think once the bottom is painted it will work fine.
Taking it off to cleanup the edges
Test fitting it in the car
A final coat of resin, some sanding and then paint and I'll start putting the battery box/batteries together.

k, the surface finish on this isn't great but it's the underside of the battery box. I'm more using this to experiment with how I can give the top cover a cool look.

Quick sand and cleanup with the DA I wanted to paint it flat black but the only single-stage flat black at the PPG store was this fancy ratrod black. I paid too much for it's intended purpose.

Looking for feedback on my wiring/bus bar, contactor, fuse, and manual shutoff arrangement. The masking tape represents wires or bus bars.

The plan is to have the pack split in half by a contactor that is actuated when the key is turned + a manual shutoff switch that is external to the battery pack in case of an emergency. I also placed a fuse on the most positive point of the battery in case there is some sort of short. I'm not sure if this is overkill since there is a fuse in the HV box.

Here is the pack: Contactor and manual shutoff: Fuse:

I cut and fit all my busbars today and my son and I started to cut and crimp all the connecting wires. The busbars were way easier to make than I expected.

What does everyone insulate their busbars with? I saw reference to plasti-dip at some point but didn't know if there were easier solutions.

A large heat shrink tube can work for insulation.

For a straight busbar like that you might want to consider adding some kind of bend to it to allow thermal movement if the batteries are rigidly bolted down. Otherwise they could losen up in time. Of course depending on how variable temperatures it will be seeing.

That battery frame is very well considered.

Another thought: would it be simpler/safer to use 70mm2 HV cables clipped to the frame in rubber mounts rather having those larger angled bus bars?

The fuse and contactor set—up you describe is the same as mine. In my mind it makes sense to have a fuse on the battery side of the contactors (as well as the one after the main contactor).

Boxster EV wrote: ↑Tue Jul 13, 2021 2:07 pm
Another thought: would it be simpler/safer to use 70mm2 HV cables clipped to the frame in rubber mounts rather having those larger angled bus bars?

Good points on the risk of the rigid bus bars coming loose. It's just as easy to make these out of cabling. I think I will go that route.

Personally, I didn't add a bend to my busbars, but my battery modules also aren't rigidly bolted down. They have some allowance for movement even while being inside a steel frame, so basically the busbars dictate their exact position. It's worked for 3 years so far but I wouldn't necessarily recommend it. I believe this wouldn't pass TÜV though, they want modules to not move at all.

I did use Nord-Lock washers though. They definitely should help with not allowing bolts to back out if things move, at least if you're able to torque them to spec without breaking your modules. This all is a bit fiddly to be honest.

Alright, plan revised. I actually thought using busbars was the preferred approach going in, but making this out of cabling is much much easier and forgiving. I'm waiting on more lugs in cabling from EVWest but I have it mocked up enough now to push forward. I also consulted with my EE friend (I'm an ME so not nearly as knowledgable on this stuff) and he definitely agreed with y'alls comments on using cabling instead.

Starting the fiberglass top cover for the battery box.