Big Brother Posted March 11, 2006 Share Posted March 11, 2006 Can anyone suggest a way of charging two 12V batteries that are connectedd in SERIES, using a single 12V alternator? Preferably one that doesn't need several £000 worth of electronic charging control gear. Also, not sure if its important but one battery is a banner - the other will be around 1/2 the size. Edited by - se7en-up! on 13 Mar 2006 22:03:53 Link to comment Share on other sites More sharing options...
peterg Posted March 11, 2006 Share Posted March 11, 2006 I think you'll have to run two sets of wiring ie. from the alternator to each battery separately as if they were each giving a 12v supply but I'm not sure what the implications for the rest of the car's wiring are from this....is it used on the road or purely a racecar which needs a bit of help starting? 🤔 Link to comment Share on other sites More sharing options...
Big Brother Posted March 11, 2006 Author Share Posted March 11, 2006 Its for a road car, in an effort to give the starter a bit of a kick (it struggles with the high compression) Steve SE7EN-UP! Incorporating the Caterham Links Database Link to comment Share on other sites More sharing options...
Manxseven Posted March 11, 2006 Share Posted March 11, 2006 Steve, Why not just get a bigger battery, I would have throught this would weigh less than 2 batteries plus all extra wiring? Simon Caterham Fireblade here Link to comment Share on other sites More sharing options...
Nifty Posted March 11, 2006 Share Posted March 11, 2006 Surely you'd need a 24V starter to do that *confused* Keep off the straight and narrow 😬 Link to comment Share on other sites More sharing options...
Nifty Posted March 11, 2006 Share Posted March 11, 2006 If my physics is correct you need to have the two batteries in parallel to give a greater current at 12V .. and you'd need the associated wiring to handle the current and starter that will handle it too. Keep off the straight and narrow 😬 Link to comment Share on other sites More sharing options...
Big Brother Posted March 11, 2006 Author Share Posted March 11, 2006 Its not a current problem. The starter I have is small, it was originally designed to turn oner a 1.6 low compression engine. Its now trying to spin a high compression 2 litre engine. When its cold it just about manages it, when its hot - forget it! Space issues mean that I can't fit a bigger starter. Several people here with similar problems have had their starters rewound to 9V in an attempt to give them more of a kick. This works really well but is pretty expensive (£240+ and NO warranty as the starter motor becomes "non standard") The old Escort rally cars used to run 12V starters on 24V to ensure they had enough "oooomph" to spin the engines over - no matter how hot they were. I know its not ideal but its a semi proven solution. And the other advantage is that if my starter motor ever dies, I can get a (cheap) replacement from Halfrauds etc. Steve SE7EN-UP! Incorporating the Caterham Links Database Link to comment Share on other sites More sharing options...
Slipper man Posted March 11, 2006 Share Posted March 11, 2006 I had a BDG Caterham which had that solution - I am told it was quite common for BD's, to get the standard starter to give a decent kick. It didn't seem to kill the starters either. I don't know how the charging worked, but James Whiting did my car so I am sure he can help Link to comment Share on other sites More sharing options...
Nifty Posted March 11, 2006 Share Posted March 11, 2006 I bow to greater knowledge Keep off the straight and narrow 😬 Link to comment Share on other sites More sharing options...
Big Brother Posted March 12, 2006 Author Share Posted March 12, 2006 Thanks Slipper man, I will give James a call next week and see if he can advise. I'm sure there is an easy way of wiring it up...but haven't figured it out yet. Steve SE7EN-UP! Incorporating the Caterham Links Database Link to comment Share on other sites More sharing options...
Stijn LUYCK 1 Posted March 12, 2006 Share Posted March 12, 2006 24V on a 12V starter motor ... and you think that would work under warranty? Twice the voltage is double the current or four times the power. I would be surprised if they survive that for very long *eek* Link to comment Share on other sites More sharing options...
MartinWoodham Posted March 12, 2006 Share Posted March 12, 2006 You can't charge two12v batteries in series off one 12v supply. The combined cell voltage, even discharged, will be pushing current the wrong way into the alternator windings. But if, once started, you break the connection between -ve batt 1 and +ve batt 2, and wire them in parallel for charging, then you could do it. Big high current changeover switch needed though.... Or get a 24v alternator off an ex-MoD FFR landie and use that. In any case, if your second battery is smaller than the standard Banner then it will limit the discharge rate available, reducing available current, so you might not get the kick you're expecting. The easier solution is to uprate the battery (in discharge current terms), or move the battery so it's cooler. Assuming there aren't any faults with wiring, battery, starter or alternator first though. Martin Roadsports B with upgradeitis Link to comment Share on other sites More sharing options...
Nifty Posted March 12, 2006 Share Posted March 12, 2006 Is there room for a FFR alternator in the engine bay? I seem to remember them being somewhat bigger than the standard Marelli job Keep off the straight and narrow 😬 Link to comment Share on other sites More sharing options...
Big Brother Posted March 12, 2006 Author Share Posted March 12, 2006 "Is there room for a FFR alternator in the engine bay?" Yep, if I take the engine out first Steve SE7EN-UP! Incorporating the Caterham Links Database Link to comment Share on other sites More sharing options...
stevefoster Posted March 12, 2006 Share Posted March 12, 2006 Don't boats run on 24V? Just convert the whole car Steve 😬 😬 😬 Hants (north) / Berkshire club here Area meeting pics here My Racing here Link to comment Share on other sites More sharing options...
Big Brother Posted March 12, 2006 Author Share Posted March 12, 2006 If I'd have wanted a canoe I'd have bought a 21 (or a Westfield ) Steve SE7EN-UP! Incorporating the Caterham Links Database Link to comment Share on other sites More sharing options...
Johnty Lyons Posted March 13, 2006 Share Posted March 13, 2006 just use the same system the Escorts did wE used it for years in Rally cars back in the good old days before WRC. Use two relays[6RAs in those days] from starter position on key to open cct the parallel connections and a spare starter solenoid from same contact to supply the series link Works a treat. jj Link to comment Share on other sites More sharing options...
Big Brother Posted March 13, 2006 Author Share Posted March 13, 2006 Johnty, That was just the info I was looking for I knew the Escorts used this system but couldn't get my head around how to wire it up. Looks like I will be buying some bits tomorrow Steve SE7EN-UP! Incorporating the Caterham Links Database Link to comment Share on other sites More sharing options...
andy_h Posted March 13, 2006 Share Posted March 13, 2006 Rahter than adding additional complexity, a second battery and the weight dis-advantage that adds, why not change the stater motor? I take the point of non-standard starters being too expensive, but what about a standard 6v starter. 12v running a 6v starter be enough kick. They're as fitted to Willy's Jeeps and can still be bought form many Jeep parts places. White road legal 2.0 HPC VX race car 😬 Link to comment Share on other sites More sharing options...
Big Brother Posted March 13, 2006 Author Share Posted March 13, 2006 Problem is not really a price one - however I really don't want to give Brise £250 for a starter they can't/won't warranty. The problem is one of space. With the Raceline sump fitted to a Zetec, you are limited to both the diameter and length of the starter. The sump was designed for use with a standard Crossflow starter (0.9kw) This may be fine for a standard Zetec but raise the compression and the starter struggles to turn the engine. (and refuses to do anything when hot!) I've found a small 12V battery that is around 1/2 the size of a banner. I think two of these will just fit into a banner battery holder so as for a weight increase, its pretty minimal. The wiring is pretty straight forward too (thanks Johnty) My only concern is that the old Escorts and BD's used the old inertia type starters. These were a little larger so I guess they would handle the extra voltage a little better. As for damaging the starter motor, I think I'm doing this every time I try to start my car - it stop turning and gets very hot as it struggles with the compression. My theory is that 24V into a 12V starter will spin it faster, and this should start the engine quicker. End result is the motor is used for less time so it should not overheat. (Also I was told today, that several engine tuners run 24V into the tiny K series starters to restart hot engines when they are fitted to a dyno) As for damaging the starter, I think heat would be the biggest killer (Where's Chris W when you need him 😬) Steve SE7EN-UP! Incorporating the Caterham Links Database Link to comment Share on other sites More sharing options...
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