Victron Multiplus 3000 - 12v vs 24v

[brainbone]

Currently in the planning stages for upgrading the cheap 1000w inverter + 2x200Ah 6v FLA house batteries in my motorhome to a Victron Multiplus 3000 (~2400w?) with LifePo.

I selected the Multiplus because of its "Power Assist" mode, allowing use of marginal shore power. Plan to use it to run AC unit (for short stints) + microwave + coffee maker when boondocking, on marginal grid or on small generator.

In any case, I'm planning to use 12v LifePo batteries (because they seem far more available than 24v ones) of some type (looking to go as cheap as possible, of course), configured in series + parallel or just parallel, depending if I go 24v or 12v for inverter. Also planning on keeping the old FLA house batteries in place since they're up in the engine compartment in space I don't need to reclaim, and connecting them + alternator to the LifePo bank via a DC to DC charger, either 12 > 24, or 12 > 12 depending on what I go with for the LifePo bank configuration, along with a switch to shut it off. The 12v FLA house battery bank would basically only power the radio when in park mode, and possibly charge the LifePo bank if the DC to DC converter is forced on when the ignition is off. I'd probably add a switch to allow the other 12v appliances to be powered off FLA or LifePo (via 24v -> 12v buck if I go with 24v for LifePo.)

So the question is, do I go with the 12v Multiplus 3000 or 24v?

The advantage of 24v seems to be lower cost on any MPPTs I would add in the future for solar, a small saving in the short chunk of wires to connect up the battery bank, and the invert may run more efficiently @ 24v (I'm having trouble fining hard data on this for the Victron.)

The main disadvantage seems to be that adding more 12v batteries in the future from different brands to the LifePo bank would be more complicated because of series configuration of 12v batteries in a 24v bank.

The advantages of 12v seems to be that I could, with careful selection, more easily expand my battery bank in the future by just adding more batteries of the same chemistry/capacity in parallel. (Is this parallel vs series mix & match a thing anyone should really worry about in the real world?) Also wouldn't need to 24v > 12v converter, though that's kinda a non-issue.

Disadvantage of 12v seems to be wiring size and potentially less efficient inverter -- and more expense on MPPTs when I finally add solar.

Anything I'm missing that might help push me one way or the other?

 

[sunshine_eggo]

Currently in the planning stages for upgrading the cheap 1000w inverter + 2x200Ah 6v FLA house batteries in my motorhome to a Victron Multiplus 3000 (~2400w?) with LifePo.

I selected the Multiplus because of its "Power Assist" mode, allowing use of marginal shore power. Plan to use it to run AC unit (for short stints) + microwave + coffee maker when boondocking, on marginal grid or on small generator.

Good luck with that. Typical RV AC is 1500W continuous, 1000W microwave consumes 1600W, and a typical small coffee maker is 900-1000W

That's 4100W. MP can handle it in surge mode, but she won't be happy.

The only time you'll need PowerAssist is if you're running on 15A, a weak generator or truly crap 30A shore.

It is important to properly configure the MP to set the AC input current limit.

So the question is, do I go with the 12v Multiplus 3000 or 24v?

The advantage of 24v seems to be lower cost on any MPPTs I would add in the future for solar, a small saving in the short chunk of wires to connect up the battery bank, and the invert may run more efficiently @ 24v (I'm having trouble fining hard data on this for the Victron.)

Yep. You nailed the two primary reasons.

The main disadvantage seems to be that adding more 12v batteries in the future from different brands to the LifePo bank would be more complicated because of series configuration of 12v batteries in a 24v bank.

Not really that big a deal. Since you're adding 12V+12V each "individual" 24V battery in the bank will have elements of the same type and age.

Something critically important is that you fully charge all 12V batteries individually before connecting them in series. Failure to do so may cause issues due to imbalance between the 12V batteries.

There are 24V balancers that monitor each 12V in the 24V battery and transfer charge from the higher voltage 12V to the lower voltage 12V. This helps keep them in balance.

The advantages of 12v seems to be that I could, with careful selection, more easily expand my battery bank in the future by just adding more batteries of the same chemistry/capacity in parallel. (Is this parallel vs series mix & match a thing anyone should really worry about in the real world?) Also wouldn't need to 24v > 12v converter, though that's kinda a non-issue.

Disadvantage of 12v seems to be wiring size and potentially less efficient inverter -- and more expense on MPPTs when I finally add solar.

Yep.

Anything I'm missing that might help push me one way or the other?

Not really, but DC-AC-DC conversion is about 75% efficient, so 24VDC to inverted 120VAC and 120VAC converted to 12VDC kinda stinks.

 

[Rocketman]

Here is my post on adding lithium’s to my MotorHome.

Batrium Watchmon Install

Hello everyone, I have a 2000 Monaco MotorHome, I will be installing eight 272ah Lishen LiFePo4 cells making a 2p4s 12v 500Ah (useable) battery. My two largest loads are a Victron MultiPlus 12/3000 inverter/charger and the engine "Boost" if my chassis battery gets low. For the BMS I chose a...

diysolarforum.com

A couple of notes: Only one big thing on at a time. Yes if the Microwave is on it is easy to overload the inverter ( it’s usually the toaster or hair dryer). But the Multiplus recovers quickly from the overload - about 1min.

Is your rig a 50amp or a 30amp connection? If 30a go with the Multiplus- if 50a look really close at the Multiplus II - 2* 120v. That would probably be the better fit.

Temperature of batteries- will your lithium batteries ever got to 0C? If they might then, figure out some heat for them. One little note I just discovered- the Victron mppt’s you can set a low voltage no charge temperature. To set that on the Multiplus you need a Bluetooth VE.Bus smart dongle.

Look really close at getting the Cerbo + touch (or any other GX device- or roll your own on a Raspberry Pi). That info all in one place is priceless in a MotorHome.

As far as 24v vs 12v… because you are not removing your current house batteries- if it’s an option I would go with 24v (just batteries- Multiplus and mppt’s and maybe a 12v to 24v transformer- correct?)

As far as watts used if you look on the spec sheet both the 12v and the 24v Multiplus say the zero load is 20watts. If you go with the Multiplus II 2*120v it says it’s zero load is 19 watts.

Good Luck!

 

[brainbone]

Good luck with that. Typical RV AC is 1500W continuous, 1000W microwave consumes 1600W, and a typical small coffee maker is 900-1000W

Sorry for the confusion. I certainly wouldn't be running them at the same time while on inverter. I'd just like to be able to use any of them individually. (Right now I can barely run our small coffee maker on the 1000w inverter.)

May eventually replace our AC with something more efficient, though I'm waiting for more lower cost options to open up. (Right now it seems like installing a mini-split would be the best lowish cost option, but I don't have a good place to put the indoor unit, even if I went ducted. The Houghton ACs from RecPro, while better than my current, don't have even close to the efficiency of the average mini-split.)

Yep. You nailed the two primary reasons.

Not really that big a deal. Since you're adding 12V+12V each "individual" 24V battery in the bank will have elements of the same type and age.

Thanks. I've been leaning towards 24V. Seems like it's probably the best option. However the flexibility of being able to swap out, remove or add single 12V batteries in a 12V setup is probably the largest thing holding me back at this point. It would be nice to be able to put some solid numbers on 12V inverter efficiency losses vs 24V.

There are 24V balancers that monitor each 12V in the 24V battery and transfer charge from the higher voltage 12V to the lower voltage 12V. This helps keep them in balance.

I'll need to look into those. I'm guessing any savings from MPPTs would be quickly eaten by the additional cost of 24V balancers.

Not really, but DC-AC-DC conversion is about 75% efficient, so 24VDC to inverted 120VAC and 120VAC converted to 12VDC kinda stinks.

If I go 24V, I'd probably use a 40A DC to DC buck converter (claim 95% efficiency max) rather than the existing 12v charge converter. (Though I'd keep the charge converter for charging the FLA on shore power -- if I end up keeping them.)

 

[corn18]

I'll second the recommendation for the Multiplus II 12/3000/2x120 50Amp if you have a 50A rig.

If 30A rig with no plans to go 50A, I would definitely go 24V.

 

[brainbone]

Here is my post on adding lithium’s to my MotorHome.

Batrium Watchmon Install

Hello everyone, I have a 2000 Monaco MotorHome, I will be installing eight 272ah Lishen LiFePo4 cells making a 2p4s 12v 500Ah (useable) battery. My two largest loads are a Victron MultiPlus 12/3000 inverter/charger and the engine "Boost" if my chassis battery gets low. For the BMS I chose a...

diysolarforum.com

Thanks! I'll look that over.

Is your rig a 50amp or a 30amp connection? If 30a go with the Multiplus- if 50a look really close at the Multiplus II - 2* 120v. That would probably be the better fit.

Only 30A

Temperature of batteries- will your lithium batteries ever got to 0C? If they might then, figure out some heat for them.

Yes, they will go below 0C, though probably not while in active use.

One little note I just discovered- the Victron mppt’s you can set a low voltage no charge temperature. To set that on the Multiplus you need a Bluetooth VE.Bus smart dongle.

I was trying to decide if I could go with lower cost batteries that lack a BMS with low temp cutoff. Still trying to figure out if all the charge devices (Multiplus, MPPT, DC -> DC converter for alternator) support charge temp monitoring.

Look really close at getting the Cerbo + touch (or any other GX device- or roll your own on a Raspberry Pi). That info all in one place is priceless in a MotorHome.

I was wondering how important/helpful those were. I'd probably go the Raspberry Pi route since I have a few of those laying around

 

[sunshine_eggo]

Sorry for the confusion. I certainly wouldn't be running them at the same time while on inverter. I'd just like to be able to use any of them individually. (Right now I can barely run our small coffee maker on the 1000w inverter.)

Good.

May eventually replace our AC with something more efficient, though I'm waiting for more lower cost options to open up. (Right now it seems like installing a mini-split would be the best lowish cost option, but I don't have a good place to put the indoor unit, even if I went ducted. The Houghton ACs from RecPro, while better than my current, don't have even close to the efficiency of the average mini-split.)

Yeah. Mini-splits are awesome for power/efficiency, but installations can be a challenge.

Thanks. I've been leaning towards 24V. Seems like it's probably the best option. However the flexibility of being able to swap out, remove or add single 12V batteries in a 12V setup is probably the largest thing holding me back at this point. It would be nice to be able to put some solid numbers on 12V inverter efficiency losses vs 24V.

Negligible efficiency difference.

I'll need to look into those. I'm guessing any savings from MPPTs would be quickly eaten by the additional cost of 24V balancers.

$20: https://www.amazon.com/PowMr-Battery-Equalizer-Voltage-Balancer/dp/B07L8XKZ71

If I go 24V, I'd probably use a 40A DC to DC buck converter (claim 95% efficiency max) rather than the existing 12v charge converter. (Though I'd keep the charge converter for charging the FLA on shore power -- if I end up keeping them.)

The only concern with 24-12V converters is any surge current you might get from things like slideout motors. If nothing has surge, you should be fine.

 

[HRTKD]

I'm in the process of installing a Multiplus 12/3000 into my RV trailer with a 30 amp 12 volt system. I've been using a 1000 watt inverter for the coffee maker but it wasn't enough to run the microwave. I don't run the air conditioner much, but I think my new inverter will do it with the PV system kicking in some watts.

I chose the 12 volt inverter/charger because I have so many 12 volt devices in the RV and I don't want to complicate the system with a 24v-12v converter. A 2400 watt inverter is plenty for my needs.

When you go to a 24 volt system you may also need a 12v-24v converter if you want the LiFePO4 battery charged by the motorhome alternator.

 

[Dzl]

I'm late to the party and haven't scanned past the OP, so apologies if I rehash anything that has already been discussed beyond the OP. A couple thoughts:

(I'm having trouble fining hard data on this for the Victron.)

Victron posts basic efficiency data in their datasheets, and every Victron product has a datasheet (easiest place to find this is the Victron Website). The datasheet will give you both the 'peak efficiecny' and the standby/idle power consumption as well as the standby when one of the power save modes is enabled. As a generalization, efficiency between 12 and 24 volt inverters or 24 and 48 volt inverters will be at most a few % in terms of peak efficiency, no-load can sometimes be more significant but no need to go off generalizations when the datasheets are easy to find.

Disadvantage of 12v seems to be wiring size and potentially less efficient inverter -- and more expense on MPPTs when I finally add solar.

The latter is the most important difference I think. But you've gotta account for the various costs, higher voltage saves mony on the MPPT, saves money on the wiring and in many cases can save considerable money on things like circuit breakers, BMS(s), etc, but on the other hand, have added costs associated with buck converters etc. Point being, when analyzing cost, try to look at the big picture.

Anything I'm missing that might help push me one way or the other?

One thing that might push you towards 12V at the moment is you have the option of the Multiplus-II in 12V but not yet in 24V. Its a bit more expensive than the original Multi, but might be worth it if it has features you would appreciate.

 

[HRTKD]

As far as I know, the Multiplus II is designed for a 50 amp system. Could it be used for a 30 amp system? Probably, but it's more expensive than the regular Multiplus.

 

[Dzl]

As far as I know, the Multiplus II is designed for a 50 amp system.

That is my understanding. It was designed specifically with the US RV market in mind, and specifically for 50A service (with the caveat that it is 2 x 120V but no 240 functionality)

Could it be used for a 30 amp system?

Not sure. I am an idiot when it comes to the RV world (never owned a traditional RV) so beyond knowing generally what 30A and 50A hookups mean, I am clueless. Here is some info:

Product Page
Datasheet (PDF)
Video introduction (AM solar), makes it sound like it'll work with any type of hookup, but I think what you are referring to is whether it is well suited for an RV wired for 30A hookups and I dont know.

Probably, but it's more expensive than the regular Multiplus.

It is. By a considerable $ amount ($285) but as a percentage of total cost its not that steep for a new model with added features (and a much better eco mode) if any of that would be valuable, if it wouldn't, than the original multiplus would probably be the better value. I'm not entirely sure what all the new features are, its been something I've been meaning to get around to researching just out of interest.