12v from a 24v hookup?

[OxMo]

I apologize for my elevator: When it comes to electric stuff, there are times it does not go to the top floor. This is one of those times. I've got two batteries, dedicated to run my 24v trolling motor. They are installed under the console. I want to install a 12v outlet on the console and make use of a short run for the wiring to one of the 12v batteries. Since they are wired in series to provide 24v, can I connect to just one of them to get 12v? In my mind, this would work -- but I'm not always Smarter Than a 5th Grader, so I need some help. Thanks in advance. Gary / Homosassa, FL

 

[tashasdaddy]

Re: 12v from a 24v hookup?

to be honest i don't know the answer. but will watch for it.

 

[slasmith1]

Re: 12v from a 24v hookup?

use a multimeter to verify this it's been a while since i hooked up a stereo in a hummer but i believe if you use the primary neg and secondary pos you will have 12vdc.

 

[Wee Hooker]

Re: 12v from a 24v hookup?

It can be done by tapping off the primary batteries pos & negitive terminal IF ( and only if) the circuit is ungrounded /isolated. i.e. Then you also have to worry about how your system is being charged. Bottom lie is that you need to test your individual system with a Volt meter.
If in doubt, just tap off the 24V and add a step down resistor (from an automotive supply source) to get you down to 12V. It will draw more power but keeps wireing simple.

 

[Silvertip]

Re: 12v from a 24v hookup?

You can tap into EITHER of the two batteries to obtain 12 volts. HOWEVER -- this comes with one very big caviat. If your boat is equipped with a 12/24 switch or a CHARGE/RUN switch at the bow, you are advised not to do this. There are many wiring schemes for those switches and since wiring diagrams are few and far between I can only say don't do it. Now then -- with the caution out of the way, check to see how many wires you have going from the battery bay to the bow of the boat. If you have only two, you have a 24V ONLY setup so this is a good thing. If you connect your power outlet to the battery that has the negative cable for the troller attached to it, you won't have to worry. Here is a diagram. While it doesn't show the actual outlet, the two leads are shown. You could use either battery but it is far safer this way. If you were to use the other battery and inadvertently ran the ground wire to the chassis of the boat, you would have 24 volts on the outlet and fry whatever you plugged into it.

 

[tashasdaddy]

Re: 12v from a 24v hookup?

thanks for clarifying that. that was my thought, but had never tried it.

 

[OxMo]

Re: 12v from a 24v hookup?

Thanks for all the replies. Caution is the word of the day -- will be going with Silvertip on this one -- with meter at hand.

You can tap into EITHER of the two batteries to obtain 12 volts. HOWEVER --

Understand the caviat. Gotta love the picture though -- you know, being worth a thousand words. I've got a multimeter and had some ideas about checking the resultant output of any handiwork I might try. Thanks for "firming up the ground" on this one -- I feel ready to proceed.

Gary / Homosassa, FL

 

[Dunaruna]

Re: 12v from a 24v hookup?

Yes it will work (keeping in mind silvertips caveats) but there is also another potential drawback, how do you charge your batteries? If you use a 24v charger, the 12v tap will drag that battery down more than the other, the 24v charger will not compensate. If you isolate the batts and use a 12v charger - all is good.

 

[Bondo]

Re: 12v from a 24v hookup?

Ayuh,...

Working with 24V heavy equipment,...
I've done as Slivertip states, Many times...
You can even Jump Start a dead horse with 2, 12V sources hooked up like that...
Or, by jumping 1 battery, warming it,+ then the other if only 1, 12V source is available...

 

[Silvertip]

Re: 12v from a 24v hookup?

Duna -- there is no problem charging a 24V system with any of the current multi-output on-board chargers. These units are not a single output that you bridge both batteries with. They have one, two, three or even four 12V outputs for just such systems. Each output is isolated from the others and each output will regulate properly. The ground for each output is also isolated from the others (floating if you will) so there is no need to break the jumper connection between the two batteries. Some newer chargers are capable of "load sharing" which means when one battery is topped off, that output will switch to another to help out. What you say is true however if one does indeed use a single 24V charger and bridge both batteries. In the grand scheme of things though, the draw on that single battery will not likely be much of an issue compared to the draw the troller is placing on it.

 

[Dunaruna]

Re: 12v from a 24v hookup?

Yep, forgot about these fandangled high tech charging gismos :redface:

One of the workshops I subcontract to services a fleet of hino trucks (24v), they pull 12v for radios and such. We are always replacing the batteries that are feeding the 12v, the other batts never seem to fail. But of course, they are being charged by a single 24v alternator.