Switching to a 24V battery bank has gone well so far. The 40A Victron 24V-12V converter seems to handle all my 12V loads without issue. It keeps the V at about 13.2V But a question: there can sometimes be other 12V sources, like the 120VAC-12V converter when on shorepower, or the truck's 12V alternator source when towing, or even the little 10W solar battery tender that came with the trailer. These are all wired into the 12V side and do not now see any batteries. Would you expect any conflict with the Victron 24V-12V converter, or any issues because of no 12V batteries?I know my mppt solar charger goes a little crazy when no batteries are present. It's scan to determine the mpp will send Vs all over the place. But it's now tied into the 24V battery bank and is happy.Also know the 120VAC-12VDC converter doesn't require batteries, but will it interfere with the 24-12VDC converter. Should I turn off the 24-12VDC converter when on shore power?Should I also let the truck's alternator handle the 12V loads by turning off the 24-12VDC when travelling, or just disconnect the alternator's feed to the trailer? I've already disconnected the little solar panel. The truck's alternator feed is harder to get to. Thanks.

In my opinion, you should FINISH the conversion by disabling all the "old" 12 V charging sources. Eventually one of them will cause you pain and confuse any troubleshooting you try to do.I say "disable" because they might come in handy later.....for exactly what I don't know.

Where do you get power for the emergency brakes (break-away switch)? The 24-12 converter or a dedicated 12v battery somewhere?If it were my truck and trailer, I would not want the DC-DC converter and the truck alternator fighting over the 12v rail. The truck is likely to win that argument, since it's higher output voltage would cause the converter to back down, assuming the converter is 12.0 vDC and the truck is 13.x vDC ... but then again, at the end of the "charge line", the voltage drop can be pretty steep (it is on my rig)Regarding what 12v source to use while you're on shore power, use whichever one provides more current. If you have a 24v battery charger (maybe built into the inverter?), there's no problem using the Victron all the time, as long as 40 amps DC is enough for your needs. If your on board AC-DC converter is more powerful, and it's easy to shut the Victron off, go that route. You could even an automatic disconnect solenoid even, when the shore power converter is powered up, it pulls the plug on the 24-12 converter.

I'd use a three position switch--Batt 1, Batt 2, all, off to disconnect the Victron while traveling. Buy a small battery for the break away function and then you can run everything just like a typical 12V system with truck charging and brakes ready to function. When you get to campground, switch to 24V and turn on Victron. When in storage, turn to "off". I like to make life easier without putting a lot of expensive gear into the equation.

IMO yank/turn off the old 12v converter and replace with a 24v converter that will maintain the 24v batts on shore power. The 12v systems will be running from the 24-12 converter.IMO tap into the 24 to get 12 for the emergency breakaway. How would you keep a separate 12v battery charged up/floated? Off the 24-12? IMO just pull the fuse in the truck for the 12v power pin 4 of the 7-pin. It won't charge the 24s. In a Chev that is Stud 1, but there must be something similar in a Dodge? 7-pin charging is really lame, so you won't be missing anything and the 12v stuff will still be on the 24-12 from the 24s on solar (driving in sunshine)The 12v from the 24-12 and the old converter will not fight each other. The 12v things will just run from whichever has the higher voltage at the time. But as above IMO ditch the 12v converter.

Meanwell 500 RSP 24 volt pwer supply. 0perate just like the 12 volt models. About 35 amp charge rate. Set to 27.6 volts.Lose thr connections to existing converter and and truck alt. Or install dedicated ground 2nd alt. On truck.

Other 12V Sources with a 24V-12V converter | Good Sam Community

Sam_Spade
Explorer
May 04, 2017
In my opinion, you should FINISH the conversion by disabling all the "old" 12 V charging sources. Eventually one of them will cause you pain and confuse any troubleshooting you try to do.

I say "disable" because they might come in handy later.....for exactly what I don't know.
GordonThree
Explorer
May 04, 2017
Where do you get power for the emergency brakes (break-away switch)? The 24-12 converter or a dedicated 12v battery somewhere?

If it were my truck and trailer, I would not want the DC-DC converter and the truck alternator fighting over the 12v rail. The truck is likely to win that argument, since it's higher output voltage would cause the converter to back down, assuming the converter is 12.0 vDC and the truck is 13.x vDC ... but then again, at the end of the "charge line", the voltage drop can be pretty steep (it is on my rig)

Regarding what 12v source to use while you're on shore power, use whichever one provides more current. If you have a 24v battery charger (maybe built into the inverter?), there's no problem using the Victron all the time, as long as 40 amps DC is enough for your needs. If your on board AC-DC converter is more powerful, and it's easy to shut the Victron off, go that route. You could even an automatic disconnect solenoid even, when the shore power converter is powered up, it pulls the plug on the 24-12 converter.
westend
Explorer
May 04, 2017
I'd use a three position switch--Batt 1, Batt 2, all, off to disconnect the Victron while traveling. Buy a small battery for the break away function and then you can run everything just like a typical 12V system with truck charging and brakes ready to function.

When you get to campground, switch to 24V and turn on Victron. When in storage, turn to "off". I like to make life easier without putting a lot of expensive gear into the equation.
BFL13
Explorer II
May 04, 2017
IMO yank/turn off the old 12v converter and replace with a 24v converter that will maintain the 24v batts on shore power. The 12v systems will be running from the 24-12 converter.

IMO tap into the 24 to get 12 for the emergency breakaway. How would you keep a separate 12v battery charged up/floated? Off the 24-12?

IMO just pull the fuse in the truck for the 12v power pin 4 of the 7-pin. It won't charge the 24s. In a Chev that is Stud 1, but there must be something similar in a Dodge? 7-pin charging is really lame, so you won't be missing anything and the 12v stuff will still be on the 24-12 from the 24s on solar (driving in sunshine)

The 12v from the 24-12 and the old converter will not fight each other. The 12v things will just run from whichever has the higher voltage at the time. But as above IMO ditch the 12v converter.
MEXICOWANDERER
Explorer
May 04, 2017
Meanwell 500 RSP 24 volt pwer supply. 0perate just like the 12 volt models. About 35 amp charge rate. Set to 27.6 volts.

Lose thr connections to existing converter and and truck alt. Or install dedicated ground 2nd alt. On truck.
brulaz
Explorer
May 04, 2017
As BFL suggests, I've just tapped into the battery bank for the 12V, unfused, emergency braking circuit. That will only be an issue if the switch is ever activated.

The 24-12VDC converter actually gives 13.2V. Not sure what's at the end of my truck's charge circuit. The 120VAC-12VDC converter is a WFCO or Prog. Dyn. depending upon my mood. IIRC both put out 13.4VDC typically.

Any of these converters (but not the truck) can power any of my 12V loads without any problem. Amperage is not an issue. Most of our loads are on 120VAC or (increasingly) 24VDC.

If, as BFL says, the 12V higher voltage source is used by the loads, I'm not sure what the problem would be by leaving all these sources in place. As I understand his comment, if any source is more than 13.2VDC of the 24V-12V converter, then that source will be used primarily until its voltage drops to 13.2V or below. No? I don't see them "fighting over" anything.

I am just trying to keep things as simple as possible, with as few changes as possible. So if something catastrophic happens, I can easily revert to 12V.
brulaz
Explorer
May 04, 2017
MEXICOWANDERER wrote:
Meanwell 500 RSP 24 volt pwer supply. 0perate just like the 12 volt models. About 35 amp charge rate. Set to 27.6 volts.
...

If I get a 120VAC charger for these batts, that's what I'd get to supplement the solar. But so far the solar charger has been doing a great job (and it gets up to 32V).
RoyB
Explorer II
May 04, 2017
I am assuming you will using two 12V batteries in series to get to the 24V you need...

You should be able to tap off of the jumper cable between the two 12V batteries in series to get your 12V needs for the break away switch and probably your jack raise 12VDC etc... These are not permanent drains and are controlled by switch actions...

There may be however a unbalance situation taping in the center and drawing DC current from only one 12VDC battery more than the other battery. These actions always seem to pick on the better battery and draws it down the worse battery in the series loop... In other words using one of the batteries more than the other one probably doesn't get to the state of charge point at the same time which eventually brings it down in performance to equal out the DC current path when using using the 24V system. I have done this on a coupe of those ARMY 24VDC systems for 10KW Power Gen Sets requiring 24VDC Start Motor circuits.

Roy Ken
BFL13
Explorer II
May 04, 2017
http://www.boatandrvaccessories.com/products/powermax-pm3-20-24-converter-charger
mapguy
Explorer
May 04, 2017
IMO -the breakaway circuit is a life/safety device and redundancy to ensure it works when needed.

Probably would maintain a separate 12v battery for breakaway and generator starting. Charge via truck and as needed with the dc-dc source you have.

Another issue to consider is that taping the center cabling of the 24v bank for 12v creates a battery condition/soc monitoring nightmare as the in/out of energy is not so easy to capture.

Battery balance could be affected by a 12v connection to the interior cabling.

Yes, none of this is real simple, but you are already many levels beyond simple by the step up to use of a 24v battery system.