Battery position?

[Davey]

Hi guys and gals. Bearing in mind that I'm building a heavy-ish roadster type car with a dirty great iron block V6 up front my mind has turned to weight distribution. I've weighed the lump and 'box and even without clutch, flywheel, alternator, PAS pump, inlet manifold, ITBs, exhaust manifolds and fluids it still weighs an eye watering 182KGs, by the time all those bits n bobs are added its going to be resembling a rather ugly 1/5 Tonne if I'm not very careful. The motor is positioned as far back in the chassis as is reasonable but to try and counter all this weight up front I've been thinking about positioning some of the other heavy bits. To this end I have been thinking of using two six volt batteries in series and mounting them either side of the fuel tank. It will be easy to create access hatches in the rear deck and dedicated battery fixtures can be easily fabricated. electrically they can be connected via a key operated cutoff switch for safety (and security) which could even be mounted between the seats. So what do you think guys, is this a good idea or am I wasting effort?

D.

[Enoch]

As long as you use heavy enough cable it should be fine. You might want to run a separate cable from each battery to the solonoid to compensate for the increased voltage drop of the longer run required.

[Davey]

As long as you use heavy enough cable it should be fine. You might want to run a separate cable from each battery to the solonoid to compensate for the increased voltage drop of the longer run required.

Cable run shouldn't be a problem, MGBs, Jags and Beemers often had batteries under the rear seats or in the boot floor 25mmsq or bigger cable will do the job. Running a separate cable from each battery is a non starter as they will be 2 No 6 volt batteries so need to be in series, i.e. one battery's negative connected to earth and its positive connected to the negative of the other battery then the positive from that one connected to the starter solenoid. My biggest concern is the proximity of the two batteries to the fuel tank in the case of a rear end shunt. How would it be considered for motor sport scrutineering for example?

D.

[Davey]

No more comments, viewpoints, ideas?

D.

[Tilly819]

depending on what kind of eats you have you could put the batterys behind the seats but infornt of the bulkhead, 1 6V on ither side maybe depends on the seats i think i could just about manage that on mine, i dont think mr IVA man would be too keen on having the battry right next to the fuel tank though.

tilly

[slimtater]

Bearing in mind quite a lot of people put a passenger foot rest in, what about between that and the bulkhead on the floor?

[HandyAndy]

No more comments, viewpoints, ideas?

D.

oh go on then... here,s my thoughts....:)

I,m not keen on the idea of the battery/ s being so close to the tank, i know other cars (production cars ) have had them in the rear, but .......

the back end of the 7 style car has very little protection of the tank area, so this is just IMHO i,d like to keep the 2 items , tank/battery apart from eachother to minimise the risk of the 2 items causing a problem to eachother.

Also, even tho you are using the mighty V6 motor, the position of the engine is quite far back in the chassis, look at how far back it is from the "axle line" of the front wheels, so having the battery mounted centrally in the car won,t adversley affect the weight balance of the car..... IMHO of course

cheers
andy

[twinturbo]

24v BOA's HATE low voltage output and struggle to start if the volts are low, any voltage drop could get annoyingly tedious.

May be worth looking at a decent MEGAMONEYWALLETSTRIPPING gel battery..

TT

[Davey]

Thanks for the input guys. I've had concerns about my idea with it putting the batteries so close to the tank myself (partly why I asked the forum really), the batteries could be placed in secure metal/wooden fixtures to keep them apart from the tank perhaps?

Passenger footwell? Not really much benefit there as it only lowers it not moves it back, it would lower the CofG though.

Volt drop? Really not an issue as long as heavy cables are used, I can easily get 35mmsq cable and would run both pos and neg to the engine bay to minimise points of potential (no pun intended) high resistance/voltage loss.

Behind the seats? I really don't think there is room for two 6 volt batteries there, I'm 6'2" so the driver's seat will be as far back as it goes to accomodate me.

I think TT's point about it not being necessary might be correct though, I've got the lump as far back as I can and it is well behind the front axle line. I'll have to weigh each corner to see what the distribution is like (I have some great portable weighing devices that can measure up to 100KGs per wheel) but I'll have to get the front suspenders done first.

Just kicking ideas around at the moment so I'm happy to hear other people's ideas.

Cheers, D.

[Davey]

Just thinking about it some more and maybe there would be room behind the seats if I made a boxed recess in each side...............

D.

[HandyAndy]

I think TT's point about it not being necessary might be correct though, I've got the lump as far back as I can and it is well behind the front axle line. I'll have to weigh each corner to see what the distribution is like (I have some great portable weighing devices that can measure up to 100KGs per wheel) but I'll have to get the front suspenders done first.

Just kicking ideas around at the moment so I'm happy to hear other people's ideas.

Cheers, D.


TT,s point ??? I,ve not changed my name , :p :D

cheers
andy

[Big Vern]

Surely the all up weight will be more than 400kg's - how will your weighing devices work? :confused:
I have tried using up market bathroom scales before but could not find any that went above 120kg's so was unable to do corner weights :mad:

BV.

[alga]

You could buy two identical 120 kg bathroom scales and balance the weight between them with a plank. Raise the remaining 4 wheels to the same height as the top of the scales, and you should be able to weigh each corner in turn.

[Davey]

Oops sorry Andy, but it was a good point well made mate;) . I made a tryping error, my weighing devices can measure up to 1000KGs per wheel not 100:D .

I blame the beer:D
D.

[HandyAndy]

:D
no prob Davey, :)

cheers
andy

[twinturbo]

I found some 150KG scales.. Cant remember if I put the link on here or LCB.

TT

[twinturbo]

http://home-garden.shop.ebay.co.uk/Bathroom-/20438/i.html?_nkw=scales+150kg&_catref=1&_fln=1&_trksid=p3286.c0.m282

TT

[Big Vern]

Ah ha Alga, thats exactly what I did:D :D

[Davey]

This is the unit I use:

Caravan/Motorhome Weight Control

Avoid getting caught overloaded with this very reasonably priced device, it can weigh up to 1000kg per wheel. Very simple to use device just weigh each wheel individually and this device can give you your total weight. Larger version due out next year weighing up to 1500kg per wheel.

£130.29 inc VAT plus P&P

D.

Duh, the picture hasn't been copied over. you can see the unit on my main website at www.davenewell.co.uk then click on "mail order" from the left hand menu and scroll down to "caravan weigher"

D.

[Bonzo]

If you want a rough idea of your corner weights, here's the lo-cost solution ;)

Basic bathroom scales (http://www.argos.co.uk/static/Product/partNumber/8329271/Trail/searchtext%3EBATHROOM+SCALES.htm)

4 of these would give you individual corner weights of up to 150kg per wheel .... Less than £40 .... Now that's lo-cost :D :D

[Davey]

You're right Ronnie but as I already have the caravan weigher and its warranted as accurate to <3% I'll stick with it:) . i actually use a piar of them and weigh both wheels of the same axle together, keeps the vehicle level so giving a more accurate reading.

D.

[alga]

I wonder, what's the difference in the readings when weighing just one wheel and when weighing both?

[Davey]

Hi Albert, the reason I use two at a time is that it keeps the vehicle level so giving an accurate reading. I've proved this several times by taking a reading then swapping the units over and repeating the readings. You can only use one unit at a time but you need to put a piece of wood of the same thickness under the opposite wheel of that axle to keep the vehicle level or you get inaccurate readings. Front to rear isn't critical but across the axel it needs to be level to get an accurate reading.

D.

[alga]

But in practical terms, what is the extra load the corner gets if you don't lift the opposite side?

[Davey]

Well it will vary from vehicle to vehicle, on a Ford Focus for example it could be anywhere from 30 to 70 KGs approximately depending on vehicle spec.

D.

[AshG]

batteries near the tank is a very bad idea, i wouldn't be surprised if it got you a nice big juicy fat fail at iva. there are now stricter rules about tanks and things that can affect tanks e.g sparks. a 12volt battery arcing out on the side of an ali tank will easily blow a hole in it.

i recall when i was younger accidentally touching a 13mm ring spanner between two battery terminals. the result was that the spanner ended up without the ring :D

my car has a pinto up front and at iva i was still heavier at the rear than the front. tbh with that boat anchor up front the weights wont be that far off 50/50 distribution.

be wise put the battery on the scuttle like it should be and don't kill yourself.

[Davey]

Cheers Ash, I've now given up the idea of them going near the tank (never really liked the idea tbh but I was looking for space for two 6 volters at the rear) but seriously considering building a box into the panel behind each seat to take one six volt unit either side. Once I get the front suspenders done I can weigh each wheel for an approximate front rear split and see if its worth bothering.

D.

[correl]

Hi just lloking at this and cant see why you dont use 2 smaller 12volt batteries run is parralel? only the motor you are using is a lot to be cranking over 6v volt batteries may not have to required punch. also if you incase the in alloy batteries in there own compartments with a small gap between the tank and battery and puts an insulator like a sheet of rubber in the gap the you would have no problems, i would also put a jacket on the battery beteen it and its case as for 6 months other the year that battery is going to be sitting in the cold and unused this will help your battery last longer

(on average a car battery looses 1% of its charge a day, in 100 days battery should be flat. The colder it gets the less days you get)

[correl]

A little addition i am planning on adding some solar pannels on my car somewhere so that when the car is not in use then the car will keep its battery topped up. Wont take much to keep the power up.

[Davey]

I could use two small 12 volt units in parallel instead of two sixes in series. Until I get to check out battery specs I don't know which way I'll go. I'm really not sold on the idea of the batteries going near the tank, I know it was my idea in the first place but I never felt truly comfortable with it. If space can be found/made behind the seats then I think this is a much better proposition. Battery maintenance and storage of the car is not an issue, it will live in my workshop and I already have a small but perfectly formed CTEK 3600 charger ready and waiting to maintain the battery(ies).

D.