bishbosh Posted June 21, 2009 Share Posted June 21, 2009 Right. I have a 12V voltmeter (VDO) that I intend to wire across the terminals of one of my two batteries. These two batteries are normally wired in parallel so I should get an acceptable reading right? However, I will shortly be installing a box of tricks from Mr Bowyer that will switch the batteries from parallel to series to generate 24V for my winch. Rest assured (says Mr Bowyer!) this will not change all the vehicle electrics to 24V, only the winch circuit. So, am I right in saying that when in 24V mode the voltmeter will register the voltage of one of the batteries only? This is what I want so I can be sure it doesn't get dragged down too far by the 24V switch (alternator won't keep up). Ta, Bish. Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted June 21, 2009 Share Posted June 21, 2009 Yes, if the voltmeter is across the first battery's terminals, before all the switch gear, it will measure both batteries when they're in parallel, and just the first battery when they're in series. Quote Link to comment Share on other sites More sharing options...
dr pepper Posted June 21, 2009 Share Posted June 21, 2009 a 24v digital meter would give a reading on 12 or 24 if you can work out the wiring, neg on one battery and pos on the other, you'd have to get the correct neg and pos otherwise you'd show 0 volts when in 24v mode. Quote Link to comment Share on other sites More sharing options...
Turbocharger Posted June 21, 2009 Share Posted June 21, 2009 Charlie - I'd be asking more questions about what's in the 'box of tricks' because, unless it's very clever, you'll be drawing the vehicle loads from just one battery and that's not good for it. Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted June 21, 2009 Share Posted June 21, 2009 Guessing that it's just a series/parallel change over, so the second battery is running without an alternator when it's in 24v configuration, and the first battery is also running the rest of the vehicle. Hardly ideal. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted June 22, 2009 Share Posted June 22, 2009 I'm sure that will work perfectly. Not sure I'd put the batteries under my seat with that setup though. And I might invest in a decent fire extinguisher. Quote Link to comment Share on other sites More sharing options...
BogMonster Posted June 22, 2009 Share Posted June 22, 2009 I'm sure that will work perfectly.Not sure I'd put the batteries under my seat with that setup though. And I might invest in a decent fire extinguisher. PMSL I read Turbochargers reply and was about to post an answer when I read that ^^^ Nicely put Quote Link to comment Share on other sites More sharing options...
Old Spot Posted June 22, 2009 Share Posted June 22, 2009 Mercedes vans were using this box of tricks 20 years ago to power a 24v starter but charge at 12v. Maybe the van breakers might be a cheaper place to look for a well built change over box. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted June 22, 2009 Share Posted June 22, 2009 The changeover box will likely only be a couple of HD relays, it's not rocket science at all, and as has been said quite a few vehicles use 12v/24v setups to start the engine. Quote Link to comment Share on other sites More sharing options...
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