Best way to tap 24v trolling batteries?

[photonfanatic]

I know we've talked about this a little bit in another thread, but I'm finally about to go ahead and wire up all these lights so I need to get this ironed out. And I figured it warranted its own thread.

So anyway, I have a 24v trolling motor, which of course uses 2 12v deep cycle batteries. Is there any way, to tap into that system, to run my LED lights? I'm going to have docking lights, side lights along the pontoons, and a couple of different interior lights. Also a couple of USB phone chargers in case anyone needs to charge their phone. The boat was missing a few electrical items that I wanted, and so I'm going to add them.

So that the thread doesn't get hung up on other options, let me first say 2 things that I don't want to do. I don't want to use the ignition battery, and I don't want to buy another battery, aka a "house battery. I'd like to avoid all that. I really just want to be able to tap my trolling motor system for the power, so lets please keep the discussion going in that direction. That out of the way, here is what my buddy thinks we can do. Don't know if it'll work.

He thinks we can just connect a wire from the positive of one battery, and connect another wire to the negative of the other battery. So as to avoid an imbalance in the system. Would that work? It doesn't sound to me like it would, but I thought I'd ask since I'd like to avoid using resistors because they can generate heat which is wasted electricity.

Anyway, I look forward to reading, thanks all!

[teecro]

Ok so you want to eat your cake and have it too? No sorry it don't work that way. You realize that what your friend wants to do will equal 24 volts right? ----(+)----(-)----(+)----(-)---- What's drawn here is 2 batteries wired in series so if you hook to the (+) on one end and the (-) on the other end it will be equal to the sum of both battery if taken from the middle and will equal NOTHING as the batteries are joined via a cable.

The only way you can get 12 volts from a 2 battery 24 volt system is to tap both your (+) and (-) from the same battery this will give you the 12 volts you are looking for. BUT it will come at a cost in battery life as it is an unequal tapping. The battery tapped for 12 volts will become more discharged than the other battery as it is doing more work. The battery that is less discharged still will receive more high amperage charge when recharging via a 24 volt charger as they are hooked up in series. Thus each will have their lives shortened for the same but opposite reasons.

The way this is done on golf carts as they use anywhere from 36 to 72 volts is to use a properly sized power converter in your case a 24DC to 12DC volt converter is needed. How big (AMP) will depend on what your doing with it.....

You can do the unequal power tap if you want too. As it will work but that it MAY shorten your battery life. How much will it shorten your battery life is not something that can be predicted. I am forced to use an unequal power tap on board a ship and those battery never make it TO their 4 year mark as our other battery do.

[photonfanatic]

So to be clear, there is absolutely no possible way to just run some wires off of the 24v system somehow, and reduce it to 12v? Just want to be 100% clear on this.

And if so, it sounds like I have 2 options, correct me if I'm wrong about that.

Option 1. Do what you said, and just run it at an imbalance. Battery life is going to shorten somewhat.

Option 2. Use this. But how much power would be wasted? And how exactly do you wire this up? As you can probably tell, I'm an electricity noob.

http://www.amazon.com/HOSSEN%C2%AE-Conv ... 24v+to+12v

[BobG]

So to be clear, there is absolutely no possible way to just run some wires off of the 24v system somehow, and reduce it to 12v? Just want to be 100% clear on this.

No, it's possible.

Here's the deal:

You have 24 Volts, but your lights are for 12 volts.
IF you connect 2 sets of lights IN SERIES, you can run them on 24 volts.

24V--------Light 1---------Light 2--------Ground

It'll WORK, but it's not ideal.

[photonfanatic]

Why is it not ideal, and what would you consider to be ideal for this?

[illinoid]

Why is it not ideal, and what would you consider to be ideal for this?

If one burns out, both go out.

[Seon]

Why is it not ideal, and what would you consider to be ideal for this?

If one burns out, both go out.

Ahhh...like the old string Christmas lights

[teecro]

.... You have 24 Volts, but your lights are for 12 volts.
IF you connect 2 sets of lights IN SERIES, you can run them on 24 volts.

24V--------Light 1---------Light 2--------Ground

It'll WORK, but it's not ideal.

I don't consider this practical for several reasons as you must be cautious of hooking up LED lighting with correct polarity as well as the above mentioned comment of when one bulb burns out in a series circuit you loose all lights....

[teecro]

So to be clear, there is absolutely no possible way to just run some wires off of the 24v system somehow, and reduce it to 12v? Just want to be 100% clear on this.

And if so, it sounds like I have 2 options, correct me if I'm wrong about that.

Option 1. Do what you said, and just run it at an imbalance. Battery life is going to shorten somewhat.

Option 2. Use this. But how much power would be wasted? And how exactly do you wire this up? As you can probably tell, I'm an electricity noob.

http://www.amazon.com/HOSSEN%C2%AE-Conv ... 24v+to+12v

Not much power is wasted via a quality voltage reducer but 20 bucks does not buy a quality reducer. As I commented most golf cart owners opt for voltage reducers but the "Made in China" units such as the one you linked to rarely last very long at all.

[teecro]

Here is a simple thought that works out; use a switch such as this http://www.mcmaster.com/#8001k13/=ypddhw and use it to switch your 12 volt load every couple of hours between both batteries. This way you can minimize the unequal loading and give yourself a disconnect so that you can work on items downstream of the switch; a 30 amp switch will handle quite the load for a long time without fail.

Also get into the habit of recharging your batteries as frequently as practical; do not wait until the performance becomes sub par as this causes damage to the batteries. Again I'll speak of golf carts where the best battery life is obtained by the simple rule of "if its parked charge it" and keep the water level above your plates.

[illinoid]

When one led light in series burns out it may or may not cause the other to go out.

There are lots of 24V DC lights and accessories for sale on the internet. Many are 12/24v.

[photonfanatic]

Not much power is wasted via a quality voltage reducer but 20 bucks does not buy a quality reducer. As I commented most golf cart owners opt for voltage reducers but the "Made in China" units such as the one you linked to rarely last very long at all.

I'd like to get your recommendation on a quality voltage reducer. This seems to me like the best way to go. Especially if there are ones which hardly waste power.

[teecro]

... I'd like to get your recommendation on a quality voltage reducer. This seems to me like the best way to go. Especially if there are ones which hardly waste power.

Here are a few for you to check out. I've used the 20-Amp unit in my electric cart for over a year with no issues.

http://www.golfcartking.com/20-amp-Volt ... t-2000.htm

http://www.golfcartking.com/Golf-Cart-V ... t-2001.htm

http://www.starmarinedepot.com/mastervo ... v-12a.html

[JBO]

What battery do you have for your starting battery? If it were me, I'd KISS. Get a BIG good quality starting battery and achieve far more CCA and RC for all your needs without any need to step down the voltage and complicate things. With a pair of jumper wires, you can always jumper your starter battery off of a trolling motor battery, if needed.

This may be overkill for your needs, but I bought this battery for us earlier this year and it works well:

http://www.amazon.com/dp/B003FFVI8A/ref ... _pC_nS_ttl

We'll see how long it lasts, but its a beast of a battery.

[photonfanatic]

Here are a few for you to check out. I've used the 20-Amp unit in my electric cart for over a year with no issues

Thanks for the recommendations. I'll probably end up going with one of those.

This may be overkill for your needs, but I bought this battery for us earlier this year and it works well:
http://www.amazon.com/dp/B003FFVI8A/ref ... _pC_nS_ttl
We'll see how long it lasts, but its a beast of a battery.

For me that is actually a lot more complicated. I'd be buying a new battery, running a bunch of wire to an area I don't really have to, moving all my plans away from the console where I want everything to be, etc. If I just buy this one little box it solves all my problems. Plus without buying an expensive new battery, it sounds like a really bad idea to run all these accessories off of your engine starting battery. Then there's the stock battery that I'd have to figure out something to do with. With my luck, I'd get out on the water and forget or something would happen, and I'd be stranded. Definitely not going to run anything off of the current engine battery.