# How do we waterproof an electric car's battery pack and main electrical terminals.



## Ziggythewiz (May 16, 2010)

Just use waterproof boxes and connectors, it's not that complicated, just really expensive.

I would recommend not driving your car into the ocean.


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## JRoque (Mar 9, 2010)

Hi all. I should be thinking about this since we have ponds and canals on every other street down here. A lot of people drive into them as result of accidents.

That said, and while there's always the potential for harm, I can't really see how an EV battery pack would pose an immediate risk to occupants while under water. You typically see a water-electricity scenario when power lines are connected to ground to complete their circuit. In our case, the pack is not grounded so it's most likely to short circuit on itself than to pass a lethal potential to occupants.

Of course, if the pack touches the vehicle's chassis as a result of the accident and then floods, all bets are off. And you can always make up a scenario where some current would pose a risk. But still, you'd have to be really unlucky to offer a path of least resistance to current vs the water around you. I believe OEMs waterproof their packs because they water-cool them and don't want their stuff to flood. If it's easy to seal then, sure, why not.

Perhaps I'm obviating something here but I'd be more concerned with gators as they see us a "drive-thru" snacks that pop in once in a while.

JR


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## Ziggythewiz (May 16, 2010)

Agreed. Also, our cars are 'high voltage', not HIGH VOLTAGE like you find on power lines. When those hit water all kinds of bad stuff happens, but I doubt a car's batteries could do much more than hurt themselves. Fresh water doesn't even conduct.

You also have to look at possible scenarios. If you stick your batteries in regular boxes, it will take some time for them to fill, and any likely shorts would be contained within the box.


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## hrev (Apr 26, 2012)

Thanks everyone for your good answers. It is not as bad as I thought. Originally I thought that submerging an EV into water is as bad as putting a running electric hairdryer into water.

So if we submerge a flooded lead acid battery in water it'll be pass most of the current through the water directly between the battery terminals and then the remaining of it (which is much much less) through curved paths between the terminals.

I'm glad the occupants have a good chance of survival if their EV becomes submerged.

... but like Ziggythewiz said, it is best if we try not to drive into a body of water. 

Thanks for your all your answers helping me clearing my head!


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## ruckus (Apr 15, 2009)

I believe sealed boxes will become the norm. As EV's progress from garage tinker project to mass acceptance, this must happen. "Open" packs will go the same way as "open" brushed motors. Gone.

Imagine an electric jeep or 4-wheeler or side by side utility vehicle. They must perform in mud, cross irrigation ditches, creeks, etc. If they are to be successful they must shrug off this type of abuse for years as "normal" wear and tear.

Full battery sealing, sealed motors, and waterproof connectors will be the norm.

You don't need to worry about lead off-gassing cause lead is just not an effective solution to any problem. It is a high-level toxin.


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## Ziggythewiz (May 16, 2010)

Unfortunately sealing stuff means you also need additional cooling, which has already led to multiple OEM recalls.


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## Caps18 (Jun 8, 2008)

Liquid tight conduit is some great stuff. I haven't looked into a battery box plan yet, but with LiFePO4 batteries, I'm not sure how sealed you can make it. I will worry about the temperature level inside the box in the summer, and will look into some removable insulation that can be added in the winter(20F-35F). Maybe a little heating pad of sorts too.

I am concerned about keeping the rain and puddles from splashing the battery terminals if it was an open box. But, I'm not going to drive through a flooded street or through a river anytime soon.


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## dtbaker (Jan 5, 2008)

Caps18 said:


> Liquid tight conduit is some great stuff. ... I will worry about the temperature level inside the box in the summer, and will look into some removable insulation that can be added in the winter(20F-35F). Maybe a little heating pad of sorts too.
> 
> I am concerned about keeping the rain and puddles from splashing the battery terminals if it was an open box.


liquid-tight conduit is EXPENSIVE and very hard to work with... PVC pipe is pretty effective, light, cheap, and easy to work with.

un-'sealed' belly pan is probably about all you need to protect from random splash and debris.

Sealing battery boxes will present cooling issues in summer, but help with winter warming.... terminals, brushes, etc are likely to be more than 6" off the ground; so unless you are building for off-road or regular submersion more than 6", just go with the pan.


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## bjfreeman (Dec 7, 2011)

I use a Non Corrosive RTV to cover all connection.
it is easy to cut off and peal if the connection needs to worked on.


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## Caps18 (Jun 8, 2008)

dtbaker said:


> liquid-tight conduit is EXPENSIVE and very hard to work with... PVC pipe is pretty effective, light, cheap, and easy to work with.


It is about $35 for 25 ft of 1/2" non-metallic with a few connectors at Lowe's. At McMaster-Carr, they have different sizes, and by the foot, it is expensive. But, I don't expect to need a lot.

I like working with it. The flexible part is nice, as well as the end connectors securely mounting to something. The metal lined stuff is heavy though. You will need a metal fish tape to pull cables through long runs however.


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## Duncan (Dec 8, 2008)

The best answer to waterproofing is - don't -

In wet environments you either need really good waterproofing - good enough to go scuba diving - or big drain holes

almost good enough waterproofing simply fills up with water - and it can't get away!

Big drain holes is the answer - and suitable coatings


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## ruckus (Apr 15, 2009)

I do not agree that open is best. 

Dirt, sand, mud, and water are very persistent and find their way into every nook and cranny. In many areas of the country salts and other chemicals are used on the roads. These are not only corrosive, but can have electrolytic properties when mixed with water. 

Battery heat is an issue when pulling huge currents from tiny batteries. A properly sized pack should have no heat problems. In fact, the batts work better when quite warm. The current crop of hybrids do not have properly sized packs. They are very tiny.

One additional thing to consider is that a sealed box will form condensation from daily thermal swings. This can be helped by using a breather tube formed into a coil or n shape. This forms a bubble when submerged. Many off-roaders use this for axle venting.


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## hrev (Apr 26, 2012)

Hi everyone, thanks very much for all your ideas and information.


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## aeroscott (Jan 5, 2008)

sealed system with heat exchange gas He , etc. Easy no .


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## Frank (Dec 6, 2008)

Total sealing is very, very difficult. My truck (lead-acid) has boxes with loose fitting lids and junk gets on the batteries, especially in winter, but it rinses off very easily (water drains through small holes in the bottom.) To seal the motor from random splashes I use a couple pieces of coroplast. At one point I also had part of a 5-gallon plastic bucket bolted to the end of the motor but decided it was redundant. The conversion has gone through 5 Maine winters so far with no major issues.

I won't use this same chassis for lithium when the PbA gets too tired, but if I did I don't think I'd change a thing. To echo what others have said about immersion, even if salt water surrounded the batteries, you'd only have local conduction (which might cause individual batteries to short-circuit) but I don't think there'd ever be safety issues for occupants (other than getting out of the car that is!)


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