12 Volt / 24 Volt Aux

Subject 12 volt 1975 C10 Truck auxillary circuit

I have a truck with a custom wiring circuit this is an endurance type hotrod. I want to install an auxillary 24 volt circuit for 24 volt headlights and winch. What would you suggest or recommend?

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built not bought

Should I run a 2nd alternator for a 24volt battery?

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built not bought

Initially I was going to suggest buying a 24V truck.

Failing that, a 24V conversion.

But otherwise, yes, a whole new charging & distribution for 24V - eg, 24V alternator of copious capacity; enough 24V battery capacity; and the wiring to the 24V loads.

I doubt there is any advantage using 24V lights (12V should perform the same) and though there are copper advantages with 24V winches, isn't using the same number of (paralleled) batteries and sticking to a 12V winch acceptable? You could still add a 2nd 12V alternator if your main alternator is undersized.

builtbychevy wrote:

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I want to install an axillary 24 volt circuit for 24 volt headlights and winch. What would you suggest or recommend?

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This is an older thread, and you may not come back for the reply, but I'll post it anyway.
You will obviously have 2 12V batteries in series to produce 24 volts. The best way to charge a 24 Volt bank is with 24 Volts, so fit a 24V alternator.
You can "tap" the center of the batteries for 12 Volts for the 12 Volt portion the truck, including the starter. The trick is to equalize the 12V battery to the second "24 Volt" battery.

Surepower used to make a line of these "equalizers" from 30 to 300 amp ratings. They basically maintain the 12 V battery voltage at exactly half of the 24 Volt bank. So both batteries remain balanced, even though the 12 Volt tap is drawing off the "center". The equalizer rating (which is the 12 Volt output rating )should exceed the normal continuous expected maximum 12 volt load. Intermittent over-loads (like cranking) are acceptable, will be covered by the 12V battery, and will not damage the equalizer.

I used "surepower 24 12 battery tap" as my Google search phrase. There are some .pdf's on the first page of hits that show wiring diagrams of the system I described here.

I've installed and maintained several 24 volt systems that were tapped for 12 volt loads on Yachts. As long as the cabling is robust and the equipment is adequately sized, these equalizer systems work quite well, and require no periodic maintenance. 24V charging and motors work so well with the higher voltage. Install a 24V starter, and you can get it cranked even in Antarctica Winters.

Hope you see this.

I read in horror... "You can "tap" the center of the batteries for 12 Volts for the 12 Volt portion the truck... but then I read the equaliser bit. Phew!

However I have always advised against such egualisers for such purposes. IMO it is much better using dc-dc converters to drop a 24V system to 12V, or install a separate 24V system if the vehicle is 12V predominantly (ie starter motors, headlights etc).

IMO the equaliser price of $500 etc (for 100A) alone justifies their non-usage. (Equalisers for series battery in general is a different issue, but they have never been considered economical for systems below ~48V, let alone 24V. Only apps like telcos and UPS etc might consider them and even then they usually rely on traditional monitoring and maintenance and timely battery replacement.)   


And in this case I think any notion of 24V is ridiculous. Why not get a 12V lighting system - especially these days? It will probably be cheaper as well as more reliable.

I know one of the systems I installed in 2002 in a 72' is still functioning as intended, and has required no attention. That boat is used every day for 4 Months a year cruising SE Alaska. That boat's electrical/battery system gets "abused" because the owner does not run a generator 24/7 when off the dock like most 72' operators. He likes "quiet boat" and relies on inverters, holding plate refrigeration, and low-voltage lighting when anchored. But the battery banks has to be replenished during the next day's running...

As far as "why install a 24V system"? Easy: Because the higher voltage works better. Especially for starters and winches. Alternators are also more efficient at 24 volts, and there's less voltage drop in reasonably sized cabling.

I know the latter. For years we've supposedly been cutting over to 48V systems for cars but unfortunately battery technology and then electric vehicles killed that.
And how long have I been critising "stupid" 12V distribution for high-power audio systems? (Which is easily solved without 24V or higher battery & charging systems.)


So you are saying those yachts upgraded to 24V systems for better winching etc?
Or that they were 24V systems to which 12V items were added?

But whatever the case, as I understand it builtbychevy is not installing a bigger startermotor and other electrics, it's merely a case of 24V lighting and that has no advantage wrt modern lighting.

If builtbychevy's loads are high, then convert to 24V and only use 12V for instrumenttion & HUs etc via a dc-dc converter which s cheaper than an equivalent sized current equaliser.
(And of course if 24V, double the power of the starter motor else it will have less torque than the 12V startermotor - unless it's a reduction type.)