24 volt to 12 volt house bank?

[BAD ORCA]

I was reading another thread in the lithium forum and it has me wondering if this approach makes more sense?

I plan to install a Victron 3000 watt inverter at some point in the future. My thinking was that i would have two 300Ah lithium batteries in parallel for a 600Ah 12 volt system.

Unfortunately, due to space constraints, its seeming more likely that the inverter will eventually end up with a 30 foot (round trip) distance from the house bank. Someone suggested in the other thread to the OP to consider a 24 volt system. It seems like maybe this would end up being more appropriate for my situation as well.

What im thinking now, and am wondering if this is a reasonably efficient way to approach this, is to have my two 300Ah lithium batteries in a 2S1P configuration instead for a 300Ah 24 volt house bank.

This bank would feed the inverter directly and all charge sources would run to this bank. This would allow me to reduce wire sizes accordingly. I would have a third 300Ah 12 volt lithium that would feed my distribution panel. This third 12 volt battery would be charged via a DC to DC charger from the 24 volt bank.

Is this typically (generally) how this is done when moving to 24 volt systems? It seems like it keeps all the 12 volt equipment happy but gives the benefits of reduced wire size and amp draw from devices like inverters. It does add a third battery to the bank so havnt figured out yet if there is a more efficient way to approach this. Need to go back and look at some of Jedi's wiring diagrams.

[s/v Jedi]

Originally Posted by BAD ORCA

I was reading another thread in the lithium forum and it has me wondering if this approach makes more sense?

I plan to install a Victron 3000 watt inverter at some point in the future. My thinking was that i would have two 300Ah lithium batteries in parallel for a 600Ah 12 volt system.

Unfortunately, due to space constraints, its seeming more likely that the inverter will eventually end up with a 30 foot (round trip) distance from the house bank. Someone suggested in the other thread to the OP to consider a 24 volt system. It seems like maybe this would end up being more appropriate for my situation as well.

What im thinking now, and am wondering if this is a reasonably efficient way to approach this, is to have my two 300Ah lithium batteries in a 2S1P configuration instead for a 300Ah 24 volt house bank.

This bank would feed the inverter directly and all charge sources would run to this bank. This would allow me to reduce wire sizes accordingly. I would have a third 300Ah 12 volt lithium that would feed my distribution panel. This third 12 volt battery would be charged via a DC to DC charger from the 24 volt bank.

Is this typically (generally) how this is done when moving to 24 volt systems? It seems like it keeps all the 12 volt equipment happy but gives the benefits of reduced wire size and amp draw from devices like inverters. It does add a third battery to the bank so havnt figured out yet if there is a more efficient way to approach this. Need to go back and look at some of Jedi's wiring diagrams.

Almost good. Instead of the third LFP battery for 12V, use the start battery and upgrade it to an AGM start battery or if budget doesn’t allow, a closed valve maintenance free LA start battery. Now look at your distribution panel loads and decide how much amperage you want it to be capable off, i.e. it’s peak load. I recommend to buy that peak load in 30A steps and probably just 30A is enough but for reasons of redundancy and a mind at rest I recommend to get two Smart Orion non isolated 24-12 30A dc-dc chargers. These will normally be in float phase for servicing your distribution panel.

This leaves the windlass. If you have an electric windlass then it should be fine with the installed 60A capacity from the Orions plus the start battery. That said, changing the motor to a 24V motor would be better.

Also: check LiTime batteries. They have 24V batteries, meaning you can use two in parallel so you create redundancy there as well. I have a couple of those, they are good

[BAD ORCA]

Originally Posted by s/v Jedi

Almost good. Instead of the third LFP battery for 12V, use the start battery and upgrade it to an AGM start battery or if budget doesn’t allow, a closed valve maintenance free LA start battery. Now look at your distribution panel loads and decide how much amperage you want it to be capable off, i.e. it’s peak load. I recommend to buy that peak load in 30A steps and probably just 30A is enough but for reasons of redundancy and a mind at rest I recommend to get two Smart Orion non isolated 24-12 30A dc-dc chargers. These will normally be in float phase for servicing your distribution panel.

This leaves the windlass. If you have an electric windlass then it should be fine with the installed 60A capacity from the Orions plus the start battery. That said, changing the motor to a 24V motor would be better.

Also: check LiTime batteries. They have 24V batteries, meaning you can use two in parallel so you create redundancy there as well. I have a couple of those, they are good

Ok interesting approach. So the 12 volt system bleeds off amps from the start battery as needed and the Orions supply and charge/ top off the 12 volt battery as its used in real time from the 24 volt bank?

After thinking this through more closely, another concern came up after i posted my original question. Let me ask this...if i wanted to have lithium redundancy (ie...a back up battery) would my original question/approach work as well? It seems like it would be the same approach as you suggested but instead passing the amps through the third lithium instead.

Here is why i ask. As i understand it a 24 volt inverter is 24 volts only and can not be hooked up to a single 12 volt battery and be used as a 12 volt inverter?

Lets say im sailing far away from civilization and one of my 12volt lithiums in the 24 volt pack craps out. If i didnt have a backup 12 volt lithium aboard my inverter would be rendered useless, which may be very important if i have an AC watermaker. If i have the third 12 volt lithium i could use that to restore the 24 volt bank and then convert my system to the one you describe running through the start battery instead. This would give me redundancy. Its definitely a much more expensive solution but any reason why this wouldnt work?

I'd love to eventually sail remote Alaska or hopefully even Chile and Argentina so im thinking of trying to make systems as redundant as possible in the event of failures.

No windlass yet but i agree the second Orion makes sense to have just in case.

[Pete7]

Almost worth converting the rest of the boat to 24v if you are doing this major upgrade. You might struggle finding a 24v VHF, but the other electronics will love 24v.

If you are going off piste then taking a couple of smaller cheap LFPs wouldn't be a problem. You might permanently connect them in to do something useful and if it all goes pear shaped one could be used to run any 12v system.

Single points of failure should be eliminated or a work around thought through. We carry a spare single induction hob and inverter even when coastal sailing just in case.

[s/v Jedi]

Originally Posted by BAD ORCA

Ok interesting approach. So the 12 volt system bleeds off amps from the start battery as needed and the Orions supply and charge/ top off the 12 volt battery as its used in real time from the 24 volt bank?

After thinking this through more closely, another concern came up after i posted my original question. Let me ask this...if i wanted to have lithium redundancy (ie...a back up battery) would my original question/approach work as well? It seems like it would be the same approach as you suggested but instead passing the amps through the third lithium instead.

Here is why i ask. As i understand it a 24 volt inverter is 24 volts only and can not be hooked up to a single 12 volt battery and be used as a 12 volt inverter?

Lets say im sailing far away from civilization and one of my 12volt lithiums in the 24 volt pack craps out. If i didnt have a backup 12 volt lithium aboard my inverter would be rendered useless, which may be very important if i have an AC watermaker. If i have the third 12 volt lithium i could use that to restore the 24 volt bank and then convert my system to the one you describe running through the start battery instead. This would give me redundancy. Its definitely a much more expensive solution but any reason why this wouldnt work?

I'd love to eventually sail remote Alaska or hopefully even Chile and Argentina so im thinking of trying to make systems as redundant as possible in the event of failures.

No windlass yet but i agree the second Orion makes sense to have just in case.

Some points:

- no, the 12V consumption does not come from the start battery which is then topped off by the Orions; it comes straight from the Orion to the distribution panel. Remember, the source with highest voltage provides the power. So when you have two of those Orions in parallel and you have a 20A load then each Orion delivers 10A while simultaneously float-charging the start battery.
When demand is more than 60A it is only that difference that comes from the start battery.

- no, your original approach isn’t good. The technical reason is that lithium batteries are not happy being fully charged, so keeping one at float charge is a bad approach leading to severe reduction in lifespan.
AGM on the other hand is very happy at float charge, which is why I recommend an AGM start battery (like Odyssey PC2150). These are very powerful, giving the Orions a perfect buffer capacity.

- to achieve lithium redundancy, instead of two 12V batteries in series, buy two 24V batteries and put them in parallel. This 100% fixes your issue.
Example: 24V 100Ah battery black friday deal for $600: https://www.litime.com/products/liti...ithium-battery
That’s equivalent to two 12V 100Ah batteries so it is a great deal. And it gets better, they will sell two for $594 each plus give you another 5% discount etc.
Two of these give you more than 5.1kWh capacity. They have bigger ones too, I have the 24V 200Ah units. I believe they support up to 4 batteries in parallel so you can create all the redundancy you need.

[SailingHarmonie]

Maybe the best way to do this is to look at how boats that were built from scratch to use 24V were designed and use those as the basis for a design. This is likely to be way better than reinventing the wheel.

I have an Amel that was designed back in 1989 and built in 1996 with a 24V system, back when such a system even on larger yachts was exotic. The basic electrical design has managed to support over 2 decades of upgrades and improvements as technology has marched on. It is a system with higher capacity than yours but the principles should still apply.

The house battery is a bank of eight G31 batteries in series/parallel for a total capacity of 460 Amp-hours at 24V. These are currently AGM batteries, and they will stay as such at least as long as this bank lasts since they meet all of our needs at a reasonable cost.

The engine and generator share a single 12V starting battery that is totally isolated from the house system. It has no charge source other than the two 12V alternators in the system, and has never needed one. The boat moves a lot, and the engine or generator run often enough that the start battery stays charged. In an emergency the starting battery can be simply jumped from one side of the house bank. (A small, but handy, benefit to paralleling 12V batteries for the house bank.)

Main house bank loads are a 3kW 220V Victron Multiplus, a 10kW bow thruster, a 1.6kW Windlass, and a 2kW 110V inverter. All powered by the house bank, and wired from it. The main system fuse is 500 Amp driven by the power draw of the bow thruster, individual branch circuits are, of course, fuse appropriately. Almost all the panel loads are also 24 Volt, but there are a few exceptions.

There are 24V to 12V converters for the VHF radio, the SSB radio, the NMEA2K bus power, and the stereo radio, and one or two other minor loads. All of these converters are original to the boat, but work fine. Much more sophisticated, compact, and modern converters can be had these days, but there is no reason to swap these out. On our boat the stereo and the SSB have been removed because we never use them. As a result, we now have a large overcapacity for 12V supply compared to our usage.

[Fintry]

Sweetwater, Fintry, and Morning Light (see below) all have 24V systems as well as 12V for radios and other things that need 12V.


It's an expensive way to solve your problem. Assuming 300 amps to the inverter (3,000 watts plus an allowance for losses) and a 15 foot one way run, 2/0 wires will have a 3% loss and double 2/0 half that. I suggest double 2/0 rather than 4/0 because the cables are easier to handle and the double 2/0 have 25% more copper.


At around $6/foot, 60 feet of 2/0 will cost you $360 and be a lot simpler system.


BTW, I have a spread sheet that does calculations like the one above by just inserting distance, voltage, and current, and has much more -- PM me for a copy.



Jim
Sweetwater - Swan 57 sloop - circumnavigated 1995-98
Fintry - x Royal Navy Fleet Tender 2003-22 20k miles including x-Atlantic The Fleet Tender Fintry
Morning Light -- Webbers Cove 42 trawler 2021- 23
Going back to sailing now that Morning Light is sold.

[BAD ORCA]

Originally Posted by s/v Jedi

Some points:

- no, the 12V consumption does not come from the start battery which is then topped off by the Orions; it comes straight from the Orion to the distribution panel. Remember, the source with highest voltage provides the power. So when you have two of those Orions in parallel and you have a 20A load then each Orion delivers 10A while simultaneously float-charging the start battery.
When demand is more than 60A it is only that difference that comes from the start battery.

- no, your original approach isn’t good. The technical reason is that lithium batteries are not happy being fully charged, so keeping one at float charge is a bad approach leading to severe reduction in lifespan.
AGM on the other hand is very happy at float charge, which is why I recommend an AGM start battery (like Odyssey PC2150). These are very powerful, giving the Orions a perfect buffer capacity.

- to achieve lithium redundancy, instead of two 12V batteries in series, buy two 24V batteries and put them in parallel. This 100% fixes your issue.
Example: 24V 100Ah battery black friday deal for $600: https://www.litime.com/products/liti...ithium-battery
That’s equivalent to two 12V 100Ah batteries so it is a great deal. And it gets better, they will sell two for $594 each plus give you another 5% discount etc.
Two of these give you more than 5.1kWh capacity. They have bigger ones too, I have the 24V 200Ah units. I believe they support up to 4 batteries in parallel so you can create all the redundancy you need.

Ah got it, now that makes perfect sense. Thanks for taking the time to elaborate. Ok, i missed your earlier point to use two 24volt batteries in parallel for redundency. Was reading it too fast.

I do have a brand spanking new Epoch 12 v 300Ah battery which i really do like a lot. This thing is a beast. Thats one reason why i was asking about using three lithiums. plus the redundency aspect, but also so i could keep this one and have a use for it.

[BAD ORCA]

Originally Posted by Pete7

Almost worth converting the rest of the boat to 24v if you are doing this major upgrade. You might struggle finding a 24v VHF, but the other electronics will love 24v.

If you are going off piste then taking a couple of smaller cheap LFPs wouldn't be a problem. You might permanently connect them in to do something useful and if it all goes pear shaped one could be used to run any 12v system.

Single points of failure should be eliminated or a work around thought through. We carry a spare single induction hob and inverter even when coastal sailing just in case.

Thanks, fortunately i havn't upgraded equipment yet and only have a couple barebones items so this is feasible. i only have a CPT wheel pilot. A cheapo chart plotter and a VHF. I wont give up the CPT at 12 volts so i would have to convert to 12 volt to still be able to use it.

[BAD ORCA]

Originally Posted by SailingHarmonie

Maybe the best way to do this is to look at how boats that were built from scratch to use 24V were designed and use those as the basis for a design. This is likely to be way better than reinventing the wheel.

I have an Amel that was designed back in 1989 and built in 1996 with a 24V system, back when such a system even on larger yachts was exotic. The basic electrical design has managed to support over 2 decades of upgrades and improvements as technology has marched on. It is a system with higher capacity than yours but the principles should still apply.

The house battery is a bank of eight G31 batteries in series/parallel for a total capacity of 460 Amp-hours at 24V. These are currently AGM batteries, and they will stay as such at least as long as this bank lasts since they meet all of our needs at a reasonable cost.

The engine and generator share a single 12V starting battery that is totally isolated from the house system. It has no charge source other than the two 12V alternators in the system, and has never needed one. The boat moves a lot, and the engine or generator run often enough that the start battery stays charged. In an emergency the starting battery can be simply jumped from one side of the house bank. (A small, but handy, benefit to paralleling 12V batteries for the house bank.)

Main house bank loads are a 3kW 220V Victron Multiplus, a 10kW bow thruster, a 1.6kW Windlass, and a 2kW 110V inverter. All powered by the house bank, and wired from it. The main system fuse is 500 Amp driven by the power draw of the bow thruster, individual branch circuits are, of course, fuse appropriately. Almost all the panel loads are also 24 Volt, but there are a few exceptions.

There are 24V to 12V converters for the VHF radio, the SSB radio, the NMEA2K bus power, and the stereo radio, and one or two other minor loads. All of these converters are original to the boat, but work fine. Much more sophisticated, compact, and modern converters can be had these days, but there is no reason to swap these out. On our boat the stereo and the SSB have been removed because we never use them. As a result, we now have a large overcapacity for 12V supply compared to our usage.

Thanks SH. Good stuff. I agree i think my next step is to start exploring wiring diagrams just to learn more details. Jedi lays out a pretty simple route which i really like. Seems really simple and ticks off all the boxes, especially since i already have the AGM start bank although i do already have a brand new 12 volt lithium. I still have a couple of months to make up my mind though...so we will see.

[BAD ORCA]

Originally Posted by Fintry

Sweetwater, Fintry, and Morning Light (see below) all have 24V systems as well as 12V for radios and other things that need 12V.


It's an expensive way to solve your problem. Assuming 300 amps to the inverter (3,000 watts plus an allowance for losses) and a 15 foot one way run, 2/0 wires will have a 3% loss and double 2/0 half that. I suggest double 2/0 rather than 4/0 because the cables are easier to handle and the double 2/0 have 25% more copper.


At around $6/foot, 60 feet of 2/0 will cost you $360 and be a lot simpler system.


BTW, I have a spread sheet that does calculations like the one above by just inserting distance, voltage, and current, and has much more -- PM me for a copy.



Jim
Sweetwater - Swan 57 sloop - circumnavigated 1995-98
Fintry - x Royal Navy Fleet Tender 2003-22 20k miles including x-Atlantic The Fleet Tender Fintry
Morning Light -- Webbers Cove 42 trawler 2021- 23
Going back to sailing now that Morning Light is sold.

Thanks Jim, much appreciated. The other advantage is that i already have most of the 2/0 wire which im using now for my temporary electrical system. I bought extra when i installed it and have some very long lengths i could re-purpose.

I think the deciding factor will be if i can find a close location to put the inverter next to the batteries. If i did, i would probably stay at a 12 volt system. The only location is in the cabinet under the galley sink. It would fit easily but would most likely require disassembling the cabinet to get access and to be able to install a water tight compartment for the inverter. Its a lot of work so im weighing the trade off of doing this -vs- having to buy another charger/batteries. I did buy a brand new Victron 12 volt charger with my new lithium, so $2000 i would like to not have waste if staying 12 volt is possible. what to do...what to do...

I have to sit down and do some maths and see if the tradeoff is worth it or whether i go and get the crowbar and sawzall.

[Jenta]

100 percent in agreeance with Jedi on his thoughts and design ideas.

I did pretty much exactly that on our catamaran. Took out the two engine start batteries as well as the generator start battery and replaced them with a very good 12V AGM that starts all three engines but is normally isolated from all the other 12V stuff on the boat unless I hit a battery relay to connect to my 12V output off my house bank.

Replaced the 12V 800AH (4x8D) house bank with a DIY 1120AH 24V house bank (4 280AH banks giving redundancy) and am driving a 8000va Quattro for 230VAC as well as a 3000va Multiplus for 120VAC. Using some of the existing cables and removing all the extra not needed and replacing with proper gauge new cable, the total weight of the new system including the Victron gear still weighed less than the previous/stock system.

The 12V system for the boat (anything I was not able to run off 24V) includes several electric winches so I have 4 Orion DC-DC converters in parallel (70 amps each) knowing that I have enough output from those to start my engines should I have an issue with my 12V AGM as well as good redundancy if needed.
I leave the Orions set to 13.3V output and when running an engine (both stock alternators only feed the single 12V AGM battery) I interconnect the 12V systems and the 14.4 volts from the alternator(s) feeds the 12V systems on board instead of the Orions.

I did however replace my 12V windlass motor with a 24V one because that was a LONG run and it did tend to sag the voltage a lot with the stock setup. The 24V motor for the windlass was a huge upgrade and now I sometimes worry about ripping apart the bow roller or crossbeam if I'm not careful.

If I were to do this all again, I might even consider doing a 48V house bank and then using DC-DC converters for everything.

[smac999]

taking loads from the start battery is compleatly irresponsible and horrible advice. even if the orion is always on. you need a 12v house battery and a 12v start battery. especially since you will have nothing to parellel that 12v battery to if ever needed.

[s/v Jedi]

Originally Posted by smac999

taking loads from the start battery is compleatly irresponsible and horrible advice. even if the orion is always on. you need a 12v house battery and a 12v start battery. especially since you will have nothing to parellel that 12v battery to if ever needed.

It is completely normal to take 12V loads from a dc-dc converter. This is how it’s been done for all 24V and 48V boats. You do not need a 12V battery at all if the converter has enough capacity but often a battery is added for big tasks like starting an engine etc.

When a battery is added, you need a dc-dc charger instead of just a converter. In Victron speak: a Smart Orion instead of regular Orion. This will end up float charging the battery most of the time, with the Orion supplying all 12V loads except when the load is more than it’s capacity, in which case the battery adds what’s needed.