Anthony Posted April 30, 2003 Share Posted April 30, 2003 I have an excellent Hawker 15 type battery as suggested by Jue (300A/14aH if I remember correctly ). I have decided to relocate battery from the engine bay and would like to fit it in the boot. This will avoid interior/footwell becoming congested and also avoid battery being near the no doubt v.hot exhaust Given the extra 2M of cable is starting going to be a problem ? Should I go up a size in battery Apologies, not an electrical engineer and last time I looked at this was A-level Physics, so all help appreciated Many thanks Anthony No engine, but 4 wheels, gearbox, diff and now Nitrons... Link to comment Share on other sites More sharing options...
old captain slow Posted April 30, 2003 Share Posted April 30, 2003 It's not so much the size of battery that will be the problem although this is a factor. It's more the voltage drop in the cable when cranking the engine because this will most likely be the more significant factor. If this is too great the engine won't start. I would suggest the quickest and easiest way to find out is connect the battery with the correct length of extended battery leads and try it with the battery just sitting on the floor. the worst that will happen is you will be the proud owner of some spare cable. My intuitive feel is it will ptobably be ok as the starter system has to cope with wide variations. Inevitably longer cables will make the system more susceptible to battery condition too because the volt drop in the battery on cranking will become more significant with age, and an old tired battery will give up the ghost and need replacing a bit earlier. C7 CDW Link to comment Share on other sites More sharing options...
Gary G Posted April 30, 2003 Share Posted April 30, 2003 Seven Nut who posts here had a battery in the boot of his last 7. He may be able to answer your question. He normally goes onto Blatchat late at night, so why not put a post in Chitchat asking for him? Link to comment Share on other sites More sharing options...
Anthony Posted April 30, 2003 Author Share Posted April 30, 2003 Thanks Guys The car is substantially in bits, with engine devorced from car at present. I would like to run cables etc through neatly at this stage rather than try and convert what is a new car now retrospectively. I suspect it will work, but agree on comments over voltage drop, just wondered if there is a calculation that can be use to validate any engineers out there ? Appreciate your help Many thanks Link to comment Share on other sites More sharing options...
Tonycaterham Posted April 30, 2003 Share Posted April 30, 2003 Anthony Even easier is you have some long jump leads connect the battery to the end of these! Tony Link to comment Share on other sites More sharing options...
Chris W Posted April 30, 2003 Share Posted April 30, 2003 Anthony David is absolutely correct in saying that the cable loss will be the critical factor. The formula is simple: volts drop in the cable = (cable resistance) x (starting current) When you consider that the starting current is in the order of 300 amps, it only takes a tiny resistance to drop many volts. The internal resistance of the battery itself is only about 1/100 of an ohm (ie: 0.01 ohms), tiny in anyone's language. But 300A across 0.01 ohms = 3 volts. That's why you'll only measure about 9v at the starter motor when cranking. Therefore your cables need to be even smaller in resistance. Go for the largest diameter cables that you can reasonably fit in the space available. As David correctly pointed out too, the battery itself won't affect the situation, other than as it ages. As its internal resistance rises with age, you are going to get starting problems sooner than a battery on short leads. Also you will need to be more diligent about keeping it in peak condition through trickle charging when not in use and water level in the cells. Many "normal" cars do have batteries of course in the boot. But the key is BIG FAT CABLES. cheers Chris 1.8K SV 140hp see it here Link to comment Share on other sites More sharing options...
lotusandy Posted April 30, 2003 Share Posted April 30, 2003 The origonal minis have thier battery in the boot with no problem, might be worth a visit to a scrap yard to get the cable from one. I would use the chassis as the 0v connection, as all those tubes will have a lower resistance than another length of cable. Andy Link to comment Share on other sites More sharing options...
Anthony Posted April 30, 2003 Author Share Posted April 30, 2003 Hi, thanks for all your help. Have spoken to VWS and recomendation is 40mm2 cable so have ordered 30 gbp's worth and I will let you all know how I get on. Anthony No engine, but 4 wheels, gearbox, diff and now Nitrons... Link to comment Share on other sites More sharing options...
Anthony Posted April 30, 2003 Author Share Posted April 30, 2003 Hi, thanks for all your help. Have spoken to VWS and recomendation is 40mm2 cable so have ordered 30 gbp's worth and I will let you all know how I get on. Anthony No engine, but 4 wheels, gearbox, diff and now Nitrons... Link to comment Share on other sites More sharing options...
Mark H Posted May 1, 2003 Share Posted May 1, 2003 Our Lotus 7 S4 has the battery in the boot , then again the boot is so big you could fit the engine in there too flares n, flames Link to comment Share on other sites More sharing options...
normalbloke.29 Posted May 1, 2003 Share Posted May 1, 2003 Our Caterham (2.0l turbo Cosworth), has the battery in the boot for obvious reasons. we have zero starting problems, and it is nowhere near rated as highly as yours.You will have no problems. I used to have a camper, which must have had 13ft of battery cable between the batt and the starter.no probs. Link to comment Share on other sites More sharing options...
Big Brother Posted May 1, 2003 Share Posted May 1, 2003 Out of interest, where/how is the battery fitted? I guess there is more room in a dedion than a LA. How is the battery secured? Steve Se7en-Up! Less is more! Remember - an amateur built the Ark - It took professionals to build the Titanic! Link to comment Share on other sites More sharing options...
Anthony Posted May 2, 2003 Author Share Posted May 2, 2003 Thanks Guys The battery will be in a modified cradle in the boot area ( it is not fabricated yet but I would like to site battery on N/S if possible to offset driver weight ! ) If the battery can start Cos Turbo, suspect my humble VX should not be an issue, this is very reasuring. I will let you know how I get on. Link to comment Share on other sites More sharing options...
Edward Guest Posted May 2, 2003 Share Posted May 2, 2003 I have the battery in the boot with a cross flow in the front. The cable goes via the cut off switch in the side of the skuttle and not problems The battery is on the near side to off set some of my weight!! Good luck Eddie Link to comment Share on other sites More sharing options...
Bare Posted May 2, 2003 Share Posted May 2, 2003 battery in the rear is V common on cars. A 2 gauge cable is prolly too big :-) Have you thought about 'weight Distribution" ?? there's normally 55% of the vehicle weight onna back wheels.. adding the weight of the battery back there ain't gonna help. Have you considered mounting it up front.. as even in front of the Rad?? Link to comment Share on other sites More sharing options...
Anthony Posted May 2, 2003 Author Share Posted May 2, 2003 Thanks Bare, much appreciated. I have a VX, so any weight I can move a little further back the better Should also tidy up the engine bay a treat ! Not sure about cooling impact if battery placed in front of rad - esp. if undertray is used. 😬 Anthony No engine, but 4 wheels, gearbox, diff and now Nitrons... Link to comment Share on other sites More sharing options...
boughtoneatlast Posted May 2, 2003 Share Posted May 2, 2003 Well mine is in the boot too.. dedion rear, battery is in one of those plastic boxes, goes via the cut off switch and no problems with starting. It just takes up too much space!!!!... and is centrally located! Would love to move it back! Gary Supersport 1.6k Link to comment Share on other sites More sharing options...
Anthony Posted May 2, 2003 Author Share Posted May 2, 2003 Guys, apologies I thought this was going to be a rare exception, given std battery position on dedions is under the bonnet ! Glad to see lots of others have succeeded, makes % success rate higher. Anthony No engine, but 4 wheels, gearbox, diff and now Nitrons... Link to comment Share on other sites More sharing options...
eric Posted May 4, 2003 Share Posted May 4, 2003 Hi Antony What about your picnic basket ? I am sure you didn't think to it. I wish you an engine in next future (in the front), with plenty horse power Just a question if I can What about small batteries (gel or dry) small powerful and light Eric Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted May 4, 2003 Leadership Team Share Posted May 4, 2003 Anthony, my battery's in the front - but by the time the cables been routed via the cut-out switch, there's probably not much short of the cable needed to reach the boot anyway This must be the case with all cars fitted with the cut-out. Stu. Link to comment Share on other sites More sharing options...
paul jacobs Posted May 4, 2003 Share Posted May 4, 2003 I've done this mod on a couple of my past cars with no probs. The first one was a Vx engined Seven, I chopped a bit off the tank and dropped the standard battery down the side, the second one was on my old 21, Vx powered of course. You will only need one long positive cable, because you earth it through the chassis, so I hope you haven't bought a great length of neg. cable because that stuff isn't cheap. I can confirm that with a Vx engine it really does make a discernable difference, better traction off the line and the nose gets in quicker too. I ended up using a little lawn tractor battery last time, with a 245bhp dry sump engine and never had a moments bother with voltage drop. Go for it........ Link to comment Share on other sites More sharing options...
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