Battery box safety

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Alibro
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Battery box safety

Post by Alibro »

I have been working on my EV conversion for over a year now and finally got round to thinking about hooking up the HV. At the moment the pack is only temporarily setup for testing but I've been doing a bit of research and just realised my original plan might not be safe.
I have a VW eGolf battery pack which is great but very bulky so I was planning to have some modules in the engine bay, some in the fuel tank space, some in the exhaust back box area and the rest in the boot. This would mean four different battery boxes. :o
With my original zero safety plan I was going to run cables between each box and connect them directly. I wasn't even thinking of using a fuse. :shock:
Having had a few minor issues this last year I'm now a bit more wary of things going wrong so would rather do it right and am planning at least one contactor (maybe two) and fuse in the main battery box but what other safety measures should I be taking.

ZeroEV have a page about it here https://zero-ev.co.uk/guides/HVBatteryWiringBasic.html and seem to be saying I should have a fuse and contactor in the first box and a fuse and contactor in the last box with a fuse and service disconnect in the middle boxes.

What safety measures are others taking for their HV battery boxes?
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Re: Battery box safety

Post by muehlpower »

In addition to the right cable sizes and fuses, I think a mechanically stable structure is very important. My box is welded from aluminum profile and has a tin cover at the top (1mm) and bottom (2mm). The inside is lined with 1mm polycarbonate panels. The fuse and the cable connections can be reached by extra covers. Inside, all connections are insulated with caps.
In my case, the box is on the underside of the car and is therefore exposed to moisture and mechanical hazards.
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Alibro
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Re: Battery box safety

Post by Alibro »

That's a very nice looking box.
My first two are made from 3mm steel angle frame covered in 1.6mm sheet. I haven't made the other two yet and may try to get the remainder of the modules in the boot to avoid having to make a fourth.

This is a box I made to go under the fuel tank but I didn't allow for fuses and/or contactor so this may need adjusted.
IMG_20210731_210115039.jpg
IMG_20210831_173523090 (1).jpg
IMG_20210731_213533925_HDR.jpg
And this still has to have a lid made for the upper section but will hold six large modules under the bonnet
IMG_20220602_220004531.jpg
IMG_20220603_181957814.jpg
IMG_20220618_153351558.jpg
I would like to have made mine with aluminium but don't have the welding skills unfortunately.
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Re: Battery box safety

Post by rstevens81 »

Apparently yoga mat material is a good choice for insulating the box, which I'll probably use as it's nice and flexible and can be glued on with spray adhesive)

Electrical boxes also look like a good choice also ...
https://www.cef.co.uk/catalogue/product ... osure-ip66
(Not advertising just a representative example)
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Re: Battery box safety

Post by Alibro »

rstevens81 wrote: Thu Jun 30, 2022 3:56 pm Apparently yoga mat material is a good choice for insulating the box, which I'll probably use as it's nice and flexible and can be glued on with spray adhesive)

Electrical boxes also look like a good choice also ...
https://www.cef.co.uk/catalogue/product ... osure-ip66
(Not advertising just a representative example)
My battery box needs to fit the space available so has to be made to size.
Yoga mat??? Is that a good insulator? I guess it has to be better than nothing but not sure about the insulation rating. :?
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Re: Battery box safety

Post by rstevens81 »

Yoga mats are made of Nitrile rubber (NBR) which is basically nitrile gloves so pretty good for putting on the inside of a battery box as all your trying to do is stop any live metal bits making contact in a bump
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Re: Battery box safety

Post by Alibro »

rstevens81 wrote: Thu Jun 30, 2022 7:18 pm Yoga mats are made of Nitrile rubber (NBR) which is basically nitrile gloves so pretty good for putting on the inside of a battery box as all your trying to do is stop any live metal bits making contact in a bump
That's good to know.
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Re: Battery box safety

Post by alexbeatle »

One of my battery boxes will also be the high voltage junction box. My boxes are aluminium.
I think I'll tape out all of the aluminum in the areas with "exposed" terminals using the 3M scotch 130C. It has 760V/mil dielectric strength.

https://www.mcmaster.com/high-voltage-tape/
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Re: Battery box safety

Post by zippy500 »

That Zero Ev link is not working now, Like to see the drawing.

Other users have mentioned about fitting a blow off vent valve, to home made boxes.

Does anyone have a link to these ?
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Re: Battery box safety

Post by arber333 »

zippy500 wrote: Sat Jul 16, 2022 8:30 am That Zero Ev link is not working now, Like to see the drawing.

Other users have mentioned about fitting a blow off vent valve, to home made boxes.

Does anyone have a link to these ?
I have tried some different ways of (non)blow-of valve. The most intreguing i have seen was on the Ipace battery box, two of them. After a faulty capacitor almost blew my rear battery box apart i take this quite seriously. Lately i just have 60mm hole to the side of my inox box and i tape it over with aluminum tape, both sides. In case of overpressure it should tear and relieve the box.
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Re: Battery box safety

Post by Alibro »

arber333 wrote: Sat Jul 16, 2022 9:11 am
zippy500 wrote: Sat Jul 16, 2022 8:30 am That Zero Ev link is not working now, Like to see the drawing.

Other users have mentioned about fitting a blow off vent valve, to home made boxes.

Does anyone have a link to these ?
I have tried some different ways of (non)blow-of valve. The most intreguing i have seen was on the Ipace battery box, two of them. After a faulty capacitor almost blew my rear battery box apart i take this quite seriously. Lately i just have 60mm hole to the side of my inox box and i tape it over with aluminum tape, both sides. In case of overpressure it should tear and relieve the box.
A perfect seal is so unlikely in my boxes I'm not going to worry about it.
I'm more concerned about having a Service Disconnect and fuse so I was thinking about making my own service disconnect.
I have the PDM from a Leaf and cables so have all the connectors required to make two or three.
IMG_20220716_181238954.jpg
IMG_20220716_181252532.jpg
I haven't taken the connectors apart yet so don't really know if this is feasible or not but I suspect the cables would need to be cut and joined then probably potted in resin or such.
What do you guys think?
Have any of you tried this?
Do Service Disconnects need to be a certain type of connector?
Is there a cheap source for Service Disconnects?
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Re: Battery box safety

Post by alexbeatle »

zippy500 wrote: Sat Jul 16, 2022 8:30 am That Zero Ev link is not working now, Like to see the drawing.

Other users have mentioned about fitting a blow off vent valve, to home made boxes.

Does anyone have a link to these ?
https://www.evcreate.nl/shop/batteries/ ... ttery-box/
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Re: Battery box safety

Post by Cookie6000 »

Alibro wrote: Sat Jul 16, 2022 5:58 pm
I haven't taken the connectors apart yet so don't really know if this is feasible or not but I suspect the cables would need to be cut and joined then probably potted in resin or such.
What do you guys think?
Have any of you tried this?
Do Service Disconnects need to be a certain type of connector?
Is there a cheap source for Service Disconnects?
In the process of tidying up my rear pack, I am reusing the same connectors as you have there in the pics. The panel mount one attached to the battery box and the other I intend using 35 or 50mm sq butt splices to lengthen the HV back to the service disconnect and fuse in the boot via two glands.

Try to harvest a service disconnect from a Leaf/Zoe/i3 etc, one with an inbuilt fuse anyway. Plenty out there but well worth getting OEM standard one for a piece of mind, so, I would avoid going cheap here as there will be a lot of connecting/disconnecting during your testing!
+1 on the Evcreate blast ports. I have a plan to put a couple in when I build my new packs.

Overall, the aim should be to have as few battery boxes as possible. Every link in that chain between boxes technically should be not only a fuse, but also a contactor. In the event of an accident, the inertia switch will kill the 12v power, open your contactors but if there are any links in the HV chain still live, there will be issues. Yes, you could put a fuse in the run from - to + terminals of the separate packs but the chassis can still become live and not necessarily pop the fuse if the hv and chassis come into contact.

I have three separate packs and not enough safety in there right now. I know that for sure! The knowledge I have gathered on the job where I am now has been an eye opener but have a plan to design something fit for purpose and safe. That includes dropping to just two packs. Also includes a isolation detection unit from Bender. You would have heard them talk about it in The Late Brake Show's vid from last week when Johnny visited the Young brothers at Santa Pod with their drag racing Beetle. Simple and relatively cheap (from a safety point of view! ) solution. https://www.bender-uk.com/products/insu ... ir155-3204

If you go to 11:43, he mentions it in there.
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Re: Battery box safety

Post by rstevens81 »

@cookie6000
Is there any chance you could add what you have learned working in a professional environment, to the wiki so that we have a gold standard of what to aim for. The mid pack fuse/disconnect is something that does stick in my mind, I am always reminded about an old boss I had saying imagine you were designing a spaceship for 1 (yourself or your minion) and what you would do.
If you want me to put together a skeleton on the wiki let me know and I'll give it a go.
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Re: Battery box safety

Post by Alibro »

Cookie6000 wrote: Tue Jul 19, 2022 7:19 am
Alibro wrote: Sat Jul 16, 2022 5:58 pm
I haven't taken the connectors apart yet so don't really know if this is feasible or not but I suspect the cables would need to be cut and joined then probably potted in resin or such.
What do you guys think?
Have any of you tried this?
Do Service Disconnects need to be a certain type of connector?
Is there a cheap source for Service Disconnects?
In the process of tidying up my rear pack, I am reusing the same connectors as you have there in the pics. The panel mount one attached to the battery box and the other I intend using 35 or 50mm sq butt splices to lengthen the HV back to the service disconnect and fuse in the boot via two glands.

Try to harvest a service disconnect from a Leaf/Zoe/i3 etc, one with an inbuilt fuse anyway. Plenty out there but well worth getting OEM standard one for a piece of mind, so, I would avoid going cheap here as there will be a lot of connecting/disconnecting during your testing!
+1 on the Evcreate blast ports. I have a plan to put a couple in when I build my new packs.

Overall, the aim should be to have as few battery boxes as possible. Every link in that chain between boxes technically should be not only a fuse, but also a contactor. In the event of an accident, the inertia switch will kill the 12v power, open your contactors but if there are any links in the HV chain still live, there will be issues. Yes, you could put a fuse in the run from - to + terminals of the separate packs but the chassis can still become live and not necessarily pop the fuse if the hv and chassis come into contact.

I have three separate packs and not enough safety in there right now. I know that for sure! The knowledge I have gathered on the job where I am now has been an eye opener but have a plan to design something fit for purpose and safe. That includes dropping to just two packs. Also includes a isolation detection unit from Bender. You would have heard them talk about it in The Late Brake Show's vid from last week when Johnny visited the Young brothers at Santa Pod with their drag racing Beetle. Simple and relatively cheap (from a safety point of view! ) solution. https://www.bender-uk.com/products/insu ... ir155-3204

Unless someone can warn me not to for reasons I haven't thought of, I will go down the road of a contactor and fuse in every pack.
Also as all these sockets have a safety switch wire, I'll use that to kill the 12V power to everything if any HV lead is disconnected.
My thinking is if someone was to yank a lead off the pack there should be no possibility of the socket or cable being live.
If there is no 12V then there is no HV at any socket or cable apart from the BMS wires which I'm still thinking about.
It may mean a bit of redesigning and more fab work but I feel it will be worth it.
VW was happy to have no safety disconnects anywhere in their battery packs so it should be OK for me although I will still have one under the bonnet.

The Leaf/Zoe service disconnects with fuse are out there but only the plug. I've yet to find a socket for one.
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Re: Battery box safety

Post by rstevens81 »

The reason Vw got away with it was it was built like a tank... well the GTE versions are and you basically have to mangle the car to get to it, it's basically a likely hood of accident that would cause a short Vs consequence equation, in the oem design the likelihood of an accident that cause a short is very low, us on the other hand can't design the car around the battery we just have to make it fit and not in the most ideal places, therefore we oversize on contactors (so they can break a short current or at least stand a chance of) and fuse wherever we can (each battery box).
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Re: Battery box safety

Post by Alibro »

rstevens81 wrote: Fri Jul 22, 2022 8:53 am The reason Vw got away with it was it was built like a tank... well the GTE versions are and you basically have to mangle the car to get to it, it's basically a likely hood of accident that would cause a short Vs consequence equation, in the oem design the likelihood of an accident that cause a short is very low, us on the other hand can't design the car around the battery we just have to make it fit and not in the most ideal places, therefore we oversize on contactors (so they can break a short current or at least stand a chance of) and fuse wherever we can (each battery box).
I've stripped down two eGolf packs and they are not that strong. The base is steel but not very thick, maybe 1.6mm or less and the top is some kind of fibre glass so not particularly strong. It is well away from any crumple zones but is exposed from below.
There is no fuse or disconnect anywhere except in the contactor block and the entire pack is a series loop of 35mm2 bussbar which has very thin insulation.
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