dirtbox Posted May 18, 2009 Share Posted May 18, 2009 Hi all. I'm hoping that this weekend I can finally fit my big oil burner into my 90. My problem still lies with the engine electrics being 24V and my 90 is 12V. I have tested a well known method of tapping into the 'first' positive to get my 12Volt supply and it seems to work on the bench. However, I have my worries about the charge of this system causing damage to the batteries. My plan was to use a 12 Volt 40 amp relay and turn it on from my ignition switch. This in turn would allow the 24V to start the solenoid via this relay. The problem lies with my 24 Volt alternator re-charging. Will the drain on the 12 Volt supply (Lights, heater, window wipers etc), cause the first battery to drop in power and in turn would the second (24V) battery over charge? I also need to know that would the 12 Volt supply still work in the same way (i.e. come on with ignition?), or would it all be a permanent live (Heater would stay on?)? I really appreciate any help on this subject as my brain is in knots with how to get over this problem! Cheers, Paul Quote Link to comment Share on other sites More sharing options...
Old Spot Posted May 20, 2009 Share Posted May 20, 2009 The problem with tapping off the center of the two batteries is that the alternator senses that the overall voltage has dropped and starts charging which will cook the other battery. On the Nissan sd33 conversion I found an ex military land rover wiper motor, heater motor,a 24v flasher unit and fuel gauge and just changed all the bulbs on my truck to 24v. The biggest pain in the ass was towing other peoples trailers as 12v bulbs don,t last long on 24v. When we did the Toyota 6cyl engine into a 110 I did manage to find one of the Mercedes (208/306 vans from the eighties I think) changeover boxes that start the van on 24v but charge from 12v. This proved to be really reliable with no problems. Quote Link to comment Share on other sites More sharing options...
Pacey Posted May 20, 2009 Share Posted May 20, 2009 You could look at fitting a second alternator? Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 20, 2009 Share Posted May 20, 2009 I'd convert everything to 24v or run a split system with a second alternator, the tapping idea is not a great one. Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted May 20, 2009 Share Posted May 20, 2009 A second vote for not using the tapping method. Change all the bulbs to 24v ones. If you can't find replacement 24v wiper/heater motors/gauges, then use a 24-12v converter. There are some on eBay - shouldn't be too expensive... Quote Link to comment Share on other sites More sharing options...
Monster Posted May 20, 2009 Share Posted May 20, 2009 Hi all. I'm hoping that this weekend I can finally fit my big oil burner into my 90. My problem still lies with the engine electrics being 24V and my 90 is 12V. I have tested a well known method of tapping into the 'first' positive to get my 12Volt supply and it seems to work on the bench. However, I have my worries about the charge of this system causing damage to the batteries. My plan was to use a 12 Volt 40 amp relay and turn it on from my ignition switch. This in turn would allow the 24V to start the solenoid via this relay. The problem lies with my 24 Volt alternator re-charging. Will the drain on the 12 Volt supply (Lights, heater, window wipers etc), cause the first battery to drop in power and in turn would the second (24V) battery over charge? I also need to know that would the 12 Volt supply still work in the same way (i.e. come on with ignition?), or would it all be a permanent live (Heater would stay on?)? I really appreciate any help on this subject as my brain is in knots with how to get over this problem! Cheers, Paul Hi, I assume your LR is a petrol! The tapping method is a definite no no in my mind. I did this on my 24 lightweight and caused much greif. You are draining the power out one battery but the batterys are in series so the current drawn needs to go through both of them, so the charge current has to go through a fully charged battery along with a discharged one. I used my stereo across one battery and whenever i started the landrover it would blow the stereos fuse! You can purchase a 24vdc to 12vdc convertor and they are quite common nowadays. Lots of Heavy equipment use them. Depends what you want to use them for as you need sutible current handling. I would have thought it could be quite easy to swap a wiper motor and heater motor for 24v versions or is this not an option? My Exmod 110 had both a FFR 24 alternator and a 12v alternator for 'normal' stuff. Just change starter! What sort of engine do you have? Add as much information on your engine/electrics/spec and i may be able to give a more detailed reply. Hope this gives food for thought. Cheers. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 20, 2009 Share Posted May 20, 2009 I'd imagine you would find someone with an Ex-MOD 24v vehicle who'd be only too happy to swap their 24V bits for your 12v ones - could be worth an ask in the MOD forums. Quote Link to comment Share on other sites More sharing options...
dirtbox Posted May 21, 2009 Author Share Posted May 21, 2009 Thanks for the replies guys. I have found some well priced 24v bits and i think I'm now ready to go. Really didn't know where to go at the time as a parts dealer gave me a shock when he said he couldn't get any 24v bits, and the only thing he ever could was an old lightweight alternator priced at £3000!!!!! Just change starter! What sort of engine do you have? A price to get my starter converted or replaced with 12V equivalent started at £286 plus vat!!!! ( Needed a cuppa tea after that!) The engine is a FD35t Nissan 3.5 four cylinder turbo diesel (direct injection) Quite rare but I'm getting prepared for the worst. I cant find much info on the engine but they are about. A few conversions too (i.e. RRC and 110) I think its worth a try anyway- If it all goes tits up, I'l find a 200 Tdi to put back in. Thats too many people warning me off tapping into the first battery now so thats out the window. 24 volt bits it is! Anyone know what replacement relays I'm going to need? That is apart from the flasher unit. I cant see any spec on the small starter relay and the brake test warning relay? Thanks again everyone. Paul Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 21, 2009 Share Posted May 21, 2009 Why you really don't want to fook about with batteries Quote Link to comment Share on other sites More sharing options...
dirtbox Posted May 23, 2009 Author Share Posted May 23, 2009 Nothing like a confidence boost!!! Anyone know what starter relay I want?? If not to save me time, what relay is in a 12v? I'l just find a 24V version. Thanks all for the help. Paul Quote Link to comment Share on other sites More sharing options...
Bush65 Posted May 24, 2009 Share Posted May 24, 2009 Sorry can't help with the starter relay, and i see you have sourced the other 24V components. For anyone else with similar issues reading this thread, there is another solution which I have mentioned before. Perhaps a moderator can put this in the Technical Archive. The Redarc Charge Equalizer will allow you to take off 12V for the normal electrics/accessories from one battery, of a pair connected in series for 24V. Typically, when an engine that has a 24V starter and alternator is fitted to a vehicle with 12V electrics, you would connect 2 12V batteries in series to supply 24V for the starter (and other 24V equipment such as a winch). The Redarc charge equalizer will allow you to take charge from the 12V battery that is connected to earth for the normal vehicle electrics. The unit will keep the voltage equal in both batteries so the 24V alternator will charge both properly. Alternatively, the Redarc can be connected to operate as a charger for a third 12V battery. There are other ways to use it depending on situation/preference. Quote Link to comment Share on other sites More sharing options...
dirtbox Posted May 24, 2009 Author Share Posted May 24, 2009 Thanks bush. I had seen the equalizer you show when I was trying to research doing this. Couldn't find anything for the UK though? Well, V8 is out with gearbox (Bloomin heavy!!) and my old LT77 is back in on the mounts. Tomorrow I hope to get the engine in and welded and start playing with electrics. I hope to use my old engine loom along with a little modification to wire the engine up. Will post some piccys when i get the engine in. Thanks again for the help. Paul Quote Link to comment Share on other sites More sharing options...
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