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Discussion Starter #1
Dear all,
I'm currently mapping out the LIFEPO4 battery pack locations on my donor car and it'll actually be split in two distinct ones : under the bonnet and in the boot. As for the latter, I'd like to keep as much loading room as possible and am therefore thinking about two options:
- trying to fit some batts under the external rear part of the car and some inside the car in the boot and bolting in a cage structure on each side in the metal bottoming the boot for securing the batts (dunno if that's clear
).
- cutting out the boot bottom to fit in a bespoke metal cage for holding the rear battery pack (approx 25 batts). I have a rather clear understanding of where the most solid parts of the chassis are located at the rear end but was just wondering about how chopping off metal from the boot bottom would affect the body's structural strength

I know some converters did this but if any of you had made that irreversible decision, what are the things to consider to do this right?
Thanks
 

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The only "body mods" I've done are on a fiberglass plane. That said, the theory is the same.

Where to go for advice depends on whether you want to sand resin or bend metal and pop rivets. For small changes that don't affect vehicle safety, I'd be inclined to recommend aluminum and either screws & nuts or blind rivets. I'm not a serious fabricator, and in any case am poor at giving such advice when I can't "see" the project. You would do well to find someone locally who is and discuss your project over a couple of beers.
 

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Discussion Starter #3
Hi Pholly,
To give you an idea of what I intend to do, an example can be found here. Although I won't be doing something that extreme, what he did in the trunk is interesting and corroborates what you said about aluminium and rivets. But I was just curious to know about any rule of thumb to appreciate the true impact on structural strength of cutting out significant body panels. The basic reason for asking is that engineers spent quite some time and money designing cars and I don't want to pretend I'm a smart aleck who can rethink the whole thing ruthlessly as if there wouldn't be any impact. I think this would be minor but how can I make sure it is? :confused:
 

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Here is my under the car rack. Make sure it doesn't wiggle, I had to add some diagonal braces to make it more rigid.







The top of this rack bolts to the bottom of the rack inside the car.


Pictures early on of the construction:



 

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Nice work! We are installing aluminum boxes in place of the fuel tanks. We are creating an edging on the top edge of the box which holds the box from dropping. This edge must be sealed and bolted to the original body structure. In most cases in uni-body style frames you must replace what you remove. If not your body/frame may twist under high torque. I will post pictures soon.

Here is my under the car rack. Make sure it doesn't wiggle, I had to add some diagonal braces to make it more rigid.







The top of this rack bolts to the bottom of the rack inside the car.


Pictures early on of the construction:



 

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Discussion Starter #6
Etischer: that's a sweet example of option number 1. Thanks for sharing. I may not have as much vertical clearance as you seem to have though... Are these TS 90AH?
LithiumManiacs: I can't wait to see the pics :D
 

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I don't think it's that big of a deal unless you plan to do baja races with it. If the frame of the battery box is solid, and it is solidly attached to the car, then you've added back the structure - maybe even more. Here are pics of what I did in my trunk to keep pretty much all the original storage capacity:
 

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Obviously I cut between the unibody frame rails that run to the back end of the car and bumper. You want to make sure you're not cutting through any brake lines by accident! Oops. Once you remove the exhaust, there is a surprising amount of real estate for the spare tire well in most cars. Carrying a can of "fix a flat" and roadside assistance on your insurance is usually fine protection, especially since these are around-town commuters.
 

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Discussion Starter #9
Good lord, that's exactly what I'm after. Thanks for that! And you even packed it with Lead-Acid! :eek: Must be pretty tough stuff.
If the frame of the battery box is solid, and it is solidly attached to the car, then you've added back the structure - maybe even more
That's a statement I'd like to make to the fellows proofing my conversion but I doubt it'll suffice... Is that something you can measure yourself and quite easily? (e.g. metal thickness, overall resistance, quality of welding etc...) These guys may well require a crash-test to prove me wrong :(
I also read these rear structures had to be 2G force-resistant of the overall batt-pack weight to be safe. How can that be measured effectively?
Thanks
 

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Good lord, that's exactly what I'm after. Thanks for that! And you even packed it with Lead-Acid! :eek: Must be pretty tough stuff.

That's a statement I'd like to make to the fellows proofing my conversion but I doubt it'll suffice... Is that something you can measure yourself and quite easily? (e.g. metal thickness, overall resistance, quality of welding etc...) These guys may well require a crash-test to prove me wrong :(
I also read these rear structures had to be 2G force-resistant of the overall batt-pack weight to be safe. How can that be measured effectively?
Thanks
I have no idea what type of testing or approval you'd need in France. In America, each state has different rules for these types of home-altered vehicles. Indiana, where I live, has NO rules. Cars require no inspection at all to be licensed. That's sad frankly (you should see some of the crap that people drive down the streets here), but makes it very easy for hot rodders and EV converters!
 

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Discussion Starter #11
I would need to prove (whatever the way) that I haven't altered the car in a way that makes it unsafe for road use (whatever that means). I can't believe we have so many hurdles here. This put me off many times but I'm stubborn. There has to be a way... :rolleyes:
I think I need to seriously consider option n°1...
 

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I am pretty sure that the steel rail edging, and plastic liner I used, are WAY stronger than the sheet steel I cut out after bolting it back together. Plenty good full of lead, and should be even better after upgrade to Li!

I also cut the front rail out completely and replaced with a steel u beam that was flat for front batteries......
 

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Thanks for sharing Dan. Actually, I will be cutting out some steel. :D
just make sure the rack you put in is stronger than what you cut out! attachments can be tricky finding something solid for support. Also keep in mind that the rack needs to stay put (full of batteries) in the worst case of a roll-over accident!
 

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I cut the floor out of the back of my car over where the original fuel tank was and built a fiberglass box to go in there. I did not modify or cut into the frame rails but did cut right up next to them. The box is then fibreglassed into the car to make it more ridged and support the box. I have 21, SE 180s mounted in it. I used the original straps that held the fuel tank in to add extra support. You can see pics of what I did at my garage entry available here.
http://www.diyelectriccar.com/garage/cars/242
 

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Discussion Starter #16
Wow, I'm impressed :eek: You guys come up with so many creative ways of fitting your packs. That's very motivating. I think I'll go for a metal structure to strengthen the area between the frame parts and design an aluminium case to hold the batteries within the frame. The these bits have been clearly identified and I think I'm comfy about the final layout. :D
 

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steel edges, or thicker AL edges are a good idea.... but I used PLASTIC liner as it is non-conductive, and better insulator from the cold during winter. The polypropylene is acid-proof, and pretty easy to 'heat weld' together. I idea of conductive shell around all the batteries made me nervous. Lots of people use marine grade plywood too.
 

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Discussion Starter #18
I concur with the non-conductive bit. That's why I thought applying an insulator by spraying a few layers of Plastidip inside the box. I think it should do the trick.
 
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