Battery Boxes

[geekygrilli]

Hi guys

Few questions regarding battery boxes and clampss.

1. My front batteries in the motor bay sit on 1"x1" m/s angle which forms a tray. I need to clamp teh batteries down. My idea is to use nylon ratchet straps, which in my opinion will me more than sufficient. The other optin is to make up m/s clamps, which won't take long, but I want to try and keep the weight down.

a) Has anyone else done this and been OK through the DVLA check?

and

b) The fan for the internal blower 'collects' its air from within the motor bay. I don't like teh though of pumping acidic gases into teh passenger compartment. So I think i should run a large hose from under the car to the blower intake...does this make sense?

2. My rear batteries currently sit in a an MDF box (without lid) which I quickly knocked up to cntain them in the boot during development. My plan is to make a galvanised steel box, with a lid, and 2 brushless motor fans blowing through and venting to the outside. The box will be bolted to the boot floor. Since this are in the passenger compantment of the vehicle....

Does this need to be gas and liquid tight? i.e. can the fans suck in from the passenger compartment and out to the exterior. Or does the box need to be completely sealed, with the only air coming from the external atmosphere?

Thanks for your time....

[electricvehicles]

Hi Chris
Give these a try
http://www.strongs.co.uk/battery%2001.htm

[hyve]

How come your interior air now comes from the engine bay ? Fiat wouldn't have done that - what happened to the original system ?

I don't recommend drawing this air from under the car, where dust, heavy gases etc tend to collect on the road and get very disturbed by your car.

I think you'll find just for an ordinary MoT your battery hold downs will be inspected and I doubt they'll accept nylon straps. Think about the weight then multiply that by 8 or so for a panic/crash stop.
A piece of M/S angle along one long top edge of the battery with a 8mm rod at each end, angled down to a point about halfway along the short bottom sides, gives both hold-down and rocking location; a very traditional motor industry arrangement. Obviously the top ends of the rods need to be threaded for nuts.
For a thorough job grind flats across the corner of the angle where you drill through for the rods, so the nut sits on a flat surface.
Corrosion-proofing in the vicinity of lead acid batteries is always a problem; I once tried using stainless but this dissolved also. Perhaps a very thorough powder coat job ? Alternatively, make a few spares and regard them as expendible !

For batteries in the back of the car think even harder about crash stops ..... they can happen.

Good luck,

[geekygrilli]

Cheers for the notes.

The fan and heater is the original, and, ah, it sucked in teh air from teh vents in front of the windscreen. I'll have to have a nose at another cinquecento to see how they stop water getting into the heater.

I folded up my rear box from 18ga m/s this morning before work. I am worried about the 'solidness' of having a boot full of batteries, but for now it appears to be the only option.

For the front batteries its not a problem to make up for fixing bars.

Corrosion isn't a problem. It shan't be a 'project' car, or a travelling science experiment, but it'll be a hobby, so I'll be keeping an eye on things and moving stuff around, changing bits and pieces. And to be honest, the most difficult part of making the battery trays was designing them to fit in, so making repalcements will be dead easy!

Its all coming along nicely now, though.

[hyve]

Base of windscreen is the favourite air intake nowadays because it's a high pressure zone, helping through-flow ventilation when the fan is off. Generally rain water collects in the bottom of the box with a drain going to a simple rubber valve, and the air being taken in a little higher. It's all become "textbook" it's so universal.

Remember when bolting the rear box through the floor that small Fiats are built of really thin steel and you ought to put some big spreaders underneath. As an example though, Type Approval requires seat belt anchorages to hold a load of 500kg and are typically a piece of 1,6mm steel about 30 square cm on the underside of the panel. The reasoning in crash safety is that the human body can cope with only so many G before it suffers fatal injury anyway, so there's no point in restraining it beyond this load. Gruesome, I know, but it's also a reminder of just how vulnerable we all are.
The point is, don't go adding unneccessary weight in your strengthening. Look at how the industry does it and learn from them.

It occurred to me there that you could get away without having fans to ventilate the box. Some holes in the bottom going through the floor lets in high pressure air trapped under the car, and the hydrogen released when charging wants to rise naturally, so a vent leading to the top of the tailgate area, a low pressure zone, will allow more through-flow ventilation. Avoid complication ! Plus save power.

regards

[geekygrilli]

Mr. hyve - you are an ingenious man!

Anchor points:
I was going to fit some 2-3mm plates under the floor, and in the box, about 100mm square.

Venting:
I have made my battery box a 'snug-fit' to the batteries, so I will need to force the air through. The fan will be controlled by a microswitch, so that when the petrol flap is open (where the power for the charger plugs in) it turns on. Or I could do it so it runs when the power lead is plugged in, not decided yet. It will run off the aux battery.

[hyve]

Sounds sensible.
A small detail: round the corners off on the under floor plates. Sharp corners and even edges will help tear through the panel under extreme load.
100mm square is probably too big for 3mm. The thickness needs to increase with area to be useful, otherwise the reinforcement itself simply bends and forms a " tent", the peak of which starts the tear in the panel. Assuming the load is high enough to bend the reinforcement. What weight are you expecting, and how many fastenings ?

I like the automatic fan switching. You could still get by with through flow, using a duct coming in one end at the top and exiting the other.

Regards,