I found this on google: Trollbridge24 Information

Works with a single alternator, two batteries, and is rated for more than enough current to run the lights. I have no idea how it would work if someone wanted to charge both batteries while using the 24V output...

Just thought it was interesting.

 

Some thing like an 18 wheeler. They have a 12 volt alternator that charges two 12 volt batteries. The Truck has an 12 volt system but the starter is 24 volts and they use a series-parallel solenoid for starting.

 

Neither one of those systems will charge the 24v system while in use.

 

Charging the whole system while in use is one of my main concerns. Has anyone ever used a DC-DC step up like the one I posted above?

I think I might need an alternator with a slightly bigger output so that the power draw of the lights/step-up won't take too much power from charging the battery.

 

How many lights? You also say these lights use a ballast, so I would assume they have a high start-up draw, you need to check that.

It looks like with that PST-SR700-24 it's going to cost you $154 + shipping for a 12 amp ability. Is that enough? or cost effective?

I think the dual battery and alt I proposed is a more capable idea that gives you more options down the line, for the same money.

 

I have 4 of these lights. My wife called KC Lights and was told that each light draws 1.6 amps and 35 watts; I don't have to run all 4 lights, but it would be pretty nice to be able to do so.

I don't think I'll really need the 24V system for anything other than the lights.

Now in order to use the 2 alternator option you said the second alternator has to be isolated and mounted in rubber. Do I just need to insert some rubber bushings in the eyelets of the alternator and then mount it to whatever bracket I can fab up? And since it won't be grounded through the casing, do I need to add a ground wire to go along with the charging wire?

Thanks again for all the help ya'll.

 

Hmmmm......I smell smoke.....

 

My tail light bulbs (1157) draw 2.1 amps each on the brake filament for a total of 4.2 amps when I put on the brakes.
I would think your KC lamps would draw a lot more than 1.6 amps.

I think I smell smoke also.

 

If these are only 35W lights why bother?
35W is not very bright. A set of Halogen headlamps runs at 50W.
I would think that these lights would be at least 100W.

24V is actually 27.6V.

P/V = A 35W/27.6V = 1.268A



I smell smoke because of the whole divorced from ground scheme.

1. This would require a hard insulator...very hard. Rubber will deflect and tear and be useless.

2. Separate ground.....huh? How are you going to do that. Even a ground wire to the 2nd battery would not be separate because it grounds to the first battery. Both batteries would need to be separate from the vehicle ground, which would necessitate a 24V ALT.

The lights would need a separate ground as well.

You'd do better to go with the DC to DC converter if you can find one large enough to handle your current draw.

Better yet, get lights that are designed for your 12V system.

Just my opinion.

Think of any electrical circuit as a big circle. Power flows around the circle. It starts and ends in the same place on the circle. You can draw power off of the circle but it must return to the circle.

You can draw 12V off a 24 dual battery system. To charge that system you will still need 24V.

 

True enough, but a second battery and alt can be used for many other things if no longer needed or not used for the lights, a 12v/24 convertor can't.


Basically the mount isolation needs to be strong, and sure that it won't ground, if it hits ground it would be just like grounding a the battery cable.

The ground for the second alt needs to be 12v, so basically the case needs to be wired to the pos of the first battery, or the charging wire of the first alt.

Look at it as two water pumps pumping water up a hill, the first pump(stock alt) pumping from a lake(ground) to a 12ft high resovoir(first bat) and a second pump(second alt) pumping from the 12ft high resovoir to a 24ft high resovoir(second bat) so the total height from the lake(ground) to the highest resovoir is 24ft(volts).


With modern lighting watts is no longer a good measure of brightness, that comparision only works if you compare the some kind of light source ie halogen vs halogen. I would suspect these lights are HUD or Xenon, they produce ALOT of light with much less power. Like the difference between incandecent bulbs and the compact florecent bulbs everyone likes.



Yes the rubber insulator must be tough.

This is incorrect, the first battery and first alt, are the ground for the 24v step, the stock battery and alt do not need to be effected at all. The 12v system and 24v system share a ground.

Not true, they share a ground, the common ground that is the whole truck still works fine.

Try to look at it this way, put a scale on the ground and place a 12lbs weight on it, scale reads 12lbs. Put a scale on top of the weight, and place a 12lbs weight on it. Now the bottom scale reads 24lbs, and the second 12lbs, but there both on the ground.


That's a fair analogy for AC but not DC, with DC an uninterupted cricle of flow is a short. DC is more like fluid flow, like the fuel system in your truck, without a fuel pressure regulator to stop the flow you wouldn't have any pressure.

 

AC and DC current behaves the same except AC current flows back and forth. Conventional Current Flow tells us DC current flows from Negative to Positive. Break the circle and you have an open. Open = no current flow.

I assumed that anybody reading my post would assume I was talking about having a load in the circuit.

In order to use 2 batteries to make 24V you need to wire them in series. Series means neg to positive. Wired in Parallel would provide 12V with 2X current capability. I haven't really figured out how a common ground would work, and I don't want to hit the books, and I have forgotten so much........

I'll ask some of the experts in one of the electronics forums I frequent.

 

It's simpler then your making it, with the batteries wired in series if you take a votage meter and ckeck voltage from battery 1 positive to ground you get 12.6v right? Then if check from battery 2 positve to ground you get 25.2v right? If you take it one step further and check from battery 2 positive to battery 1 positive you get 12.6v again, good so far right.

This is all your using, in both of the above checks the 12.6v and 25.2v share a common ground, same is true in use throughout the truck.

 

I hope it is OK to post a link to another forum. It is not truck related or vehicle for that matter.

These guys are experts in installing RF equipment (radios that transmit) in cars and trucks. Hell, motorcycles, bicycles, back packs, and you name it. Many are electronics experts. Many are very well versed in electronic theory and build their own radio equipment. I like to build my own station accessories and antennas, but don't know enough to roll my own rig (build a ham radio).

Some don't know a LED from a fuel pump.

Not Radio Related...Could be though - QRZ Forums

 

Cool forum, thanks for the link, ham radio is something I want to get into.

No real answers there though, why don't you go ahead and cut/paste my suggestion and see what they have to say?

 

I posted your idea over there.
There were some real answers there and some smart *** posts as well. Just like any forum I guess.

I think most of them suggested replacing the bulbs with those that would work with 12V or the lights themselves.

Well see what they say about your idea.