24v Battery Boat System - need 12v

CSkipR · 10-05-2009, 06:26 PM

My boat has 6 batteries. Two are for the engines and wired in series at 24volts. The other four are for the generator/house wired in series at 24v. I ran #6 wire from the flybridge to the battery compartment in the engine room to power a stereo amplifier but I am not sure if I can wire directly to one of the batteries for 12v power since they are wired in series. Also my battery charger is a PT24-40 Newmar and charges at 24v. Any assistance is appreciated.

K1W1 · 10-05-2009, 06:43 PM

Hi,

You should be able to get 6,12,18 and 24V out of a combnation of 4 6V Batteries.

If you start at the positive of the set and follow the lead from the negative terminal of the same battery you will see it goes to the positive of another one.

If you use your test meter between the first positive and the negative of the second battery you should see 12 V.

You can also do this in reverse starting at the negative post.

I am not sure taking a constant draw off one battery ( or 2 in your case) connected in series is a good idea from what I have heard but have not personally experienced any failures that I would attribute to this practice.

CSkipR · 10-05-2009, 06:54 PM

K1W1
All the batteries are 12v Odysses AGM. Are you saying just tap on one battery even if it is hooked in series. What about the 24v battery charger will it create a problem.
Thanks

Pascal · 10-05-2009, 07:26 PM

it's not ideal since some of the batteries will work harder than the other ones and those that are not used for the amplifier maybe a little overcharged... but it will work

If the amp. pulls a lot and/or is used a lot, you're much better off doing it right which is hooking it up to a 24 to 12v converter

Capt J · 10-05-2009, 08:55 PM

Quote:

Originally Posted by Pascal

it's not ideal since some of the batteries will work harder than the other ones and those that are not used for the amplifier maybe a little overcharged... but it will work

If the amp. pulls a lot and/or is used a lot, you're much better off doing it right which is hooking it up to a 24 to 12v converter

I second this. An Amplifyer uses a lot of electricity and If you connect to 1 battery out of a 2 battery bank, the charger is going to charge both batteries in that bank and end up frying one of them. Ideally for a stereo amp, you're going to want a dedicated battery for it, which you could install on the flybridge and then you are going to need a battery charger for it. But that will give you the least amount of interference.

An amplifyer spikes amp draw too much to use a converter and will cause a lot of line noise in the speakers from what I have seen.

It may be ok to hook the AMP to 24 volts, read the specs on it, but a lot of electronics can handle say 8-30 volts but not all.

K1W1 · 10-05-2009, 10:05 PM

Quote:

Originally Posted by CSkipR

My boat has 6 batteries. Two are for the engines and wired in series at 24volts. The other four are for the generator/house wired in series at 24v........

Hi,

The fact that you have four 12V in Series means that there must be two pairs in parallel or you would have 48V at the end of the connections.

When I read you had four batteries I just assumed that they must be 6V Cells as four in series for 24V is not something I have come across before.

captain_jack · 10-05-2009, 10:55 PM

You can't tap one 12 volt battery that is being charged in series with a 24V charger, as mentioned, one battery will be cooked as the regulator tries to charge the dead one.

Best and cheapest solution is to pull a second piece of #6 to the second 12 volt battery wired in series with the first one.
As long as the load is split equally between the two batteries in series there will be no problems.
Parallel the two #6's at the amp with a distribution block, you cant have too much current for an amp, so this should work well. Verify all your voltages before connecting equipment, 24 VDC will fry an amp.

Garry Hartshorn · 10-06-2009, 12:31 AM

Newmar make a DC to DC converter, that would be the best option though others have been mentioned that would work.

K1W1 · 10-06-2009, 03:15 AM

Quote:

Originally Posted by captain_jack

Best and cheapest solution is to pull a second piece of #6 to the second 12 volt battery wired in series with the first one.
As long as the load is split equally between the two batteries in series there will be no problems.
Parallel the two #6's at the amp with a distribution block, you cant have too much current for an amp, so this should work well. Verify all your voltages before connecting equipment, 24 VDC will fry an amp.

Hi,

If he just runs a single cable between two positives and then picks up the negative somewhere else connected to the 24V System he will have 24V on one of the leads.

If you are going to do this run a lead from each positive of two 12V Batteries connected in series and another lead from each negative on the same batteries.

As suggested above join both pairs of the like polarity leads near the amp in a JB or similar and please test the result before connecting your equipment via a fuse protected link to the supply.

Garry Hartshorn · 10-06-2009, 04:25 AM

As I understand what you have and would like to do what I have drawn will work. The positive post on batteries #1 & #3 will have 24VDC at all times not only from the charger but because the batteries are in series. Batteries #2 & #4 will have 12VDC at the post, however it is problematic due to the uneven loads placed on the batteries. You will end up replacing batteries more often !! The best solution is a 24VDC to 12VDC converter.

K1W1 · 10-06-2009, 04:34 AM

Hi,

When I went to school I do not recall being able to get 24V out of two positives without the addition of a negative somewhere. ( normally connecting one positive to one negative)

Where would you have this guy hook his negative to this solution?

Henning · 10-06-2009, 04:44 AM

Quote:

Originally Posted by K1W1

Hi,

When I went to school I do not recall being able to get 24V out of two positives without the addition of a negative somewhere. ( normally connecting one positive to one negative)

Where would you have this guy hook his negative to this solution?

To the negative buss. It's pretty simple really.

Garry Hartshorn · 10-06-2009, 06:17 AM

Thanks Henning, I should have mentioned that.

Henning · 10-06-2009, 06:25 AM

Quote:

Originally Posted by Garry Hartshorn

Thanks Henning, I should have mentioned that.

It was on the schematic..... which is pretty much how I set up all my house banks, one series buss and one parallel buss. The negative buss works both. Several of the better inverters do it all for you as well.

CSkipR · 10-06-2009, 04:38 PM

Quote:

Originally Posted by Garry Hartshorn

As I understand what you have and would like to do what I have drawn will work. The positive post on batteries #1 & #3 will have 24VDC at all times not only from the charger but because the batteries are in series. Batteries #2 & #4 will have 12VDC at the post, however it is problematic due to the uneven loads placed on the batteries. You will end up replacing batteries more often !! The best solution is a 24VDC to 12VDC converter.

Garry,
That is very similar to what it looks like. I'm not at the boat and unfortunately don't have a picture in front of me. Not sure about a converter will it handle the amperage of an amplifier. Typically what do these converters run. After running the two # 6 wires it seems like a waster to have to purchase a converter when I have 4 new house batteries.
Thanks