Time to tackle the electrical system. I have questions on LIFePO4

[PierreR]

Hi All:
Just scraped my three FLA 8d house bank that was dead and bought two 12v 300 amp hour LiFePO4 to replace them. I have determined loads and my usage is docking with power unless I have to anchor out. Anchoring out is not the default mode here. I need to be able to last 6-7 hours overnight with running 12k in AC plus refrigeration.
It is currently my understanding that I need to have a start lead acid battery and charge my Lithium when underway with a DC/DC charger or with my 9KW generator. I currently have an 8d battery or the starboard engine/Generator/Anchor winch being charged off a 75amp large cage alternator. I plan on setting up the Port engine start battery as lead acid charged from a 80 amp large cage alternator. There are separated panels for Port and Starboard DC with bus, switching and fusing. Shore power is 240v 50amp through 15KVA 240v isolation transformer or 120v/30amp through a 5KVA transformer. Panel is 60amp 120v two sides on AC and 100amp DC There is no 240v equipment on board.

I presently have a Multiplus 12/2000/80 I purchased in 2023 that is not large enough to run AC off the house batteries. I also charge a 24v/100amp hour bank with DC/DC 12/24-10 from the house bank
My questions arise because of confusion about all the stuff in the wiring diagrams presented by Victron.
Question one is I would like to purchase a Multiplus 12/3000/120. can this be wired in parallel with the Multiplus 2000?

question 2 I see a number of devices in the diagram that I am unsure of. They are the Orion XS 12v/12v 50a which I assume charges the house bank when underway from the start battery/alternator. Is this correct?

Question 3: I see a note of control comes from the GX devices. I see a Cerbo GX and a GX touch 50. Are they necessary? or very worth while?

Question 4: see a VS Bus BMS NG. I don't know the real purpose of this device. both batteries have built in BMS and are not Victron. Is this device necessary or added complexity?

Diagram https://www.victronenergy.com/uploa...-Distributor-MPPT-100-50-Orion-XS-BMV-712.pdf

 

[Frosty]

I'll grab a couple of easy ones and leave the rest to more experty members:

question 2 I see a number of devices in the diagram that I am unsure of. They are the Orion XS 12v/12v 50a which I assume charges the house bank when underway from the start battery/alternator. Is this correct?

Yes. While this is not the only (or even best, for many setups) way to charge house bank from alternator, that is what it does. They are coming out with a 70-amp version soonish, but it can still be a limitation. One place where it shines is if you have smaller alternator capacity. eg I have a very small alternator and the Orion XS allows me to set an upper limit on how many amps the Orion XS puts out.

Question 4: see a VS Bus BMS NG. I don't know the real purpose of this device. both batteries have built in BMS and are not Victron. Is this device necessary or added complexity?

This is a Victron BMS. You can only (and only need to) to use these with Victron branded external BMS batteries (and in this case specifically their NG batteries). So you have no use for one. Your batteries most likely have the BMS inside each battery case (if you post the info on the batteries you bought, we could confirm).

I'm with you on the Victron diagrams. They always throw in everything but the kitchen sink. Maybe the kitchen sink is even in there too but it's hard to see due to all the detail!

 

[DDW]

You don't need a Cerbo, as you can control the other Victron products in other ways, but if you have a Multiplus and an Orion, you probably should go the distance and put in a Smartshunt and Cerbo. This gives you centralized control, monitoring, and logging of everything. Including remote monitoring if you have a WiFi connection. If you have the space and older eyes, go with the Touch 70, not the 50.

If you have only a 80A spec alternator (which will not do 80A BTW) then an Orion is probably sufficient to charge the LFP. If you go to a larger alternator some day you may want to rethink that. The next step is really a larger alternator and external regulator, and then charging the LFP directly through a relay or FET isolator is a better way to go IMO. Alternatively add another parallel Orion.

I'm not sure you can parallel a 2000VA and a 3000VA Multiplus. Good question for them but I doubt it. You could buy another 2000VA Multiplus and parallel with the one you have, giving 4000VA out.

 

[READY]

Question 3: I see a note of control comes from the GX devices. I see a Cerbo GX and a GX touch 50. Are they necessary? or very worth while?

Required? Perhaps not but very worthwhile..monitoring, configuring, troubleshooting. I would not go without it.
Ken

 

[Frosty]

I glossed over your 80-amp alternator. Given that, and given that your stated goal is NOT to spend a week on the hook, I would think the Orion XS would be just swell. It will also isolate your start battery(s) (which I imagine you will keep some form of lead acid) from the LFP house bank.

You may even want to choke down the Orion a bit from 50 amps (which you can easily do - or undo - in the phone app).

You mention wanting to run your Air-conditioner and refrigeration overnight (sounds like just a night here or there?). If you can find out how many watts or amps those use, then it can easily be calculated.

On the Inverter: If it's just the Air-con startup amp load that's bogging it down, perhaps it's possible to add a "soft start" capacitor? I'm no Air-con expert, but I know people do this on RV's to get over the "locked rotor amps" startup hump (which can be quite a bit more draw than the actual running amps).

 

[psneeld]

There are LiFePO4 start batteries now. I know one that goes over 1000CCA.

 

[Frosty]

There are LiFePO4 start batteries now. I know one that goes over 1000CCA.

That's a point. But if I was reading the OP correctly, he mostly docks while cruising (due to certain limitations) but wants to be able to spend a night or so on the hook from time-to-time, and run the Air-con and the refrigerator. LFP house would be great for that.

That's not to say it all can't be re-done (start batts etc.), but -- wrongly or rightly -- I read it as a setup mostly for a specific use-case.

 

[Serene]

Question one is I would like to purchase a Multiplus 12/3000/120. can this be wired in parallel with the Multiplus 2000?

question 2 I see a number of devices in the diagram that I am unsure of. They are the Orion XS 12v/12v 50a which I assume charges the house bank when underway from the start battery/alternator. Is this correct?

Question 3: I see a note of control comes from the GX devices. I see a Cerbo GX and a GX touch 50. Are they necessary? or very worth while?

Question 4: see a VS Bus BMS NG. I don't know the real purpose of this device. both batteries have built in BMS and are not Victron. Is this device necessary or added complexity?

I just went through this process myself recently. Installed air conditioners, inverter, LiFePO4 batteries, DC-DC charger and solar. So have learned a lot in the process and am very happy with the result.

Here are my answers to your questions above;

1. To parallel inverters they must be exactly the same spec/model.

2. The Orion XS is a DC-DC charger, typically used to charge from AGM start to LiFePO4 house. There is also an Orion Tr with the difference between max current (50A for XS vs 30A for Tr) and Cerbo connectivity via VE.Direct for the XS. If you don't go with a Cerbo and only need 30A then the Tr is an alternate option.

3. The Cerbo GX and Touch 50 are used for monitoring and control. Not strictly necessary as you can enable 'instant readout' with the Victron Connect app and look at everything via bluetooth. But I would not go without the Cerbo. Has other benefits than just monitoring. Allows for lots of other inputs to be consolidated onto the screen and connect to Victron's Remote Management portal if you have internet access on your vessel.

4. The BMS NG is an external BMS for use with Victron NG batteries. It is quite a sophisticated device and ties all Victron gear together and controls all sorts of charge parameters in connected devices. If you don't have Victron NG batteries then this BMS is not relevant.

 

[Frosty]

The Orion XS is a DC-DC charger, typically used to charge from AGM start to LiFePO4 house. There is also an Orion Tr with the difference between max current (50A for XS vs 30A for Tr) and Cerbo connectivity via VE.Direct for the XS. If you don't go with a Cerbo and only need 30A then the Tr is an alternate option.

While there is nothing incorrect in the above, I can't imagine buying an Orion TrSmart instead of an Orion XS now.

-- The TrSmart is heavy, bulky, and prone to overheating and de-rating itself (not just an occasional happening).

-- It's less efficient by almost 12% as compared to the XS (there is the heat).

-- You can't adjust the amps (may not matter though). It's just 30. No more, no less. With the XS you can have anything from 50 amps (future model: 70) right down to 1/2 amp.

-- No Smart Network (Smart Network is nice if you don't have the whole Cerbo system, though may not matter to this poster granted).

-- No bluetooth (if that matters).

I mean, nothing you said is wrong, but unless one is really pinching pennies, I can't imagine going for the TrSmart 30 over the Orion XS50 (future also 70). Just the overheating/de-rating alone would put me off.

I do think right now the XS is only 12v/12v (TrSmart can convert voltages) but I think that will be changing.

@Serene I hope this doesn't sound like I'm piling on, as everything you said was completely accurate. I just don't have fuzzy feelings about the TrSmart compared to the XS for the above reasons which I wanted to articulate.

 

[PierreR]

I do have two perfectly good lead acid start batteries. I am replacing the house bank. I would just as soon keep the 80 amp alternator for now.

I can certainly buy another multiplex with the same specs to parallel them. I am controlling the current one with a Digital Multi Control GX panel. The present Multiplex does not have blue tooth. A parallel situation would give me 4000va and that might be enough to run the two small AC units if I switch off the hot water tank. Figuring out how to parallel them is for later.

I would like to keep costs down as I don't want to sink to much into this boat that I can't get back out. I am not cheeping out though or we would be talking something other than Victron

I probably will go with the Orion XS. Nobody has caught the Elephant in the room though and I don't know how to ask a decent question about it. The Alternator is 80 amp and the Orion XS is 50 amp. The DC 12v to 24v charger is currently wired to the house bank and can draw as much as 20 amps. that battery stays up pretty well as it's only used for 12v start and charging the 24v AGM thruster bank. I have not figured out what to do with the source for the DC/DC 12/24 charger yet.

The reason for not much anchoring out is that my wife is partially disabled and the dinghy is a no go and she gets stiff quickly without walking. She can't walk far but need to walk often.

I am not opposed to topping up the batteries with the generator if I have not caught up by running the engines. The battery house bank will be 600amp hours. A hot night at anchor would depress them pretty good.

I have some time to think this through. There doesn't seem to be much for Black Friday

 

[Serene]

While there is nothing incorrect in the above, I can't imagine buying an Orion TrSmart instead of an Orion XS now.

-- The TrSmart is heavy, bulky, and prone to overheating and de-rating itself (not just an occasional happening).

-- It's less efficient by almost 12% as compared to the XS (there is the heat).

-- You can't adjust the amps (may not matter though). It's just 30. No more, no less. With the XS you can have anything from 50 amps (future model: 70) right down to 1/2 amp.

-- No Smart Network (Smart Network is nice if you don't have the whole Cerbo system, though may not matter to this poster granted).

-- No bluetooth (if that matters).

I mean, nothing you said is wrong, but unless one is really pinching pennies, I can't imagine going for the TrSmart 30 over the Orion XS50 (future also 70). Just the overheating/de-rating alone would put me off.

I do think right now the XS is only 12v/12v (TrSmart can convert voltages) but I think that will be changing.

@Serene I hope this doesn't sound like I'm piling on, as everything you said was completely accurate. I just don't have fuzzy feelings about the TrSmart compared to the XS for the above reasons which I wanted to articulate.

@Frosty all good. No problem with adding to the discussion. That's what this place is all about. And your points are valid. I wouldn't (and didn't) buy the Tr either. I went with the XS for lots of the above reasons, plus I wanted it connected to the Cerbo.

Just pointing out options for the OP to research as the XS is about 40% more expensive in my location.

BTW there is an XS 1400 that converts voltages between 12/24 up to 1400W.

 

[Serene]

I do have two perfectly good lead acid start batteries. I am replacing the house bank. I would just as soon keep the 80 amp alternator for now.

I kept AGM for main engine and generator start batteries, as well as bowthruster and anchor windlass. I also kept my existing 100A alternator. I didn't want to jump too far in one project and was quite happy only changing house to LiFePO4. With the alternator staying on the AGMs and the use of the Orion XS it is pretty simple. Might not be optimised to the nth degree, but should be pretty robust.

I can certainly buy another multiplex with the same specs to parallel them. I am controlling the current one with a Digital Multi Control GX panel. The present Multiplex does not have blue tooth. A parallel situation would give me 4000va and that might be enough to run the two small AC units if I switch off the hot water tank. Figuring out how to parallel them is for later.

Yes just manage your loads. I only have 3,000VA at the moment and have to load shed when inverting. A future project will be to add a second 3,000VA inverter in parallel.

I would like to keep costs down as I don't want to sink to much into this boat that I can't get back out. I am not cheeping out though or we would be talking something other than Victron

Nothing wrong with being sensible about costs and where your dollars are best spent to get the best return with usage, not necessarily resale.

I probably will go with the Orion XS. Nobody has caught the Elephant in the room though and I don't know how to ask a decent question about it. The Alternator is 80 amp and the Orion XS is 50 amp. The DC 12v to 24v charger is currently wired to the house bank and can draw as much as 20 amps. that battery stays up pretty well as it's only used for 12v start and charging the 24v AGM thruster bank. I have not figured out what to do with the source for the DC/DC 12/24 charger yet.

Your 80A alternator will probably not be able to sustain 80A continuously. I am running my 100A at 50A so I don't burn it out. Maybe that's too conservative, but I can add a second 50A XS and parallel them to get more if needed. I've also got a Balmar external regulator with a temperature sensor on the alternator set to 60c. Also pretty conservative.

The XS input and output current can be adjusted so if you can't sustain 50A you can turn them down.

 

[Frosty]

@Frosty all good.

Thanks.

BTW there is an XS 1400 that converts voltages between 12/24 up to 1400W.

Oh that's right. I forgot about that!

 

[Frosty]

I do have two perfectly good lead acid start batteries. I am replacing the house bank. I would just as soon keep the 80 amp alternator for now.

I don't see any reason not to do that, given your use case. Seems like a good plan.

I can certainly buy another multiplex with the same specs to parallel them. I am controlling the current one with a Digital Multi Control GX panel. The present Multiplex does not have blue tooth. A parallel situation would give me 4000va and that might be enough to run the two small AC units if I switch off the hot water tank. Figuring out how to parallel them is for later.

Do you know what your Air-con draws? Could be in watts or amps. Also, if there is a startup current (could be called LRA for locked rotor amps). Then we can calculate what you would need for battery capacity to run for X hours (also, is the typical duty cycle 50%? Or more?)

I probably will go with the Orion XS. Nobody has caught the Elephant in the room though and I don't know how to ask a decent question about it. The Alternator is 80 amp and the Orion XS is 50 amp.

For this part, no problem. Your Orion doesn't need to be able to "handle" 80 amps. In fact, as @Serene mentioned, it's the opposite -- you don't want to suck the life out of your alternator (LFP can charge fast) with TOO MUCH house bank charging. So even 50 amps might be more than you'd want to take (or it may be just right). If it's too much you can dial it back easily on the XS (simple adjustment on bluetooth app) (on the XS, not the older Tr Smart).

The DC 12v to 24v charger is currently wired to the house bank and can draw as much as 20 amps. that battery stays up pretty well as it's only used for 12v start and charging the 24v AGM thruster bank. I have not figured out what to do with the source for the DC/DC 12/24 charger yet.

So wait, is your house bank 12 volts? And also the alternator and start bank. But just the thruster bank is 24 volts?

That's slightly out of my league (at least without pondering) but perhaps that could just stay as-is (presuming you are keeping the thruster bank as is).

The reason for not much anchoring out is that my wife is partially disabled and the dinghy is a no go and she gets stiff quickly without walking. She can't walk far but need to walk often.

I had gathered that from other posts. So your use case is not to try to anchor out for weeks(s), but more a night or two at a time, in comfort, with AC if needed (right?).

I am not opposed to topping up the batteries with the generator if I have not caught up by running the engines. The battery house bank will be 600amp hours. A hot night at anchor would depress them pretty good.

That could be a way to make up for Air-Con depletion. Because you are right to think about not only having enough battery bank, but..... the ability to put the power back after you use it.

I have some time to think this through. There doesn't seem to be much for Black Friday

There IS the LFPexperts.com 25% off Black Friday sale (that's our very own @Barking Sands ). You may not be ready to make a leap, but I could imagine something like a pair of 300ah Essentials or even a pair of 460ah since you have a generator. To my mind those might hit the sweet spot? (Based on what you've said): A known quantity (vs. a mystery battery), but without a lot of bells and whistles (fancy Victron comms, etc.)(you can still use Victron bluetooth for your Victron stuff, and there is also an app for the batteries).

 

[PierreR]

Given that I don't want to run the generator overnight but have no problem during the day and tend to get a lot of overnight dockage. I have come up with the following plan.


I currently have two 8d FLA start batteries. One for the starboard engine, generator and anchor windlass and one for the Port engine and intend to keep them. I charge the starboard engine with a 75 amp alternator both internal voltage regulators.

I currently have a 2023 multiplex 12/2000va/120/80 that I can run refrigeration and light loads with while underway. The automatic switching between shore power and inverter has never worked properly and requires turning nearly everything off before asking it to switch and even then can take a couple of minutes. Then I can switch things back on. (I need more digging into this problem)

I plan on replacing the 12/2000va/120/80 with a multiplex 2-24/5000/120/95. I have purchased two 300 amp hour 12.8 volt LiFePO4 batteries for a house bank that would be charged in series (25.6v) but pull off 12.8V for 100 amp 12v DC panel.

I currently have shore power as 1-50amp 240v split phase through a 15kva isolation transformer and one 30amp 120v through a 5000Kva isolation transformer. There is a switch for 240v or 120v at the panel. There is nothing 240v on the boat and the panel is split phase when the switch is set to 240v and both sides single phase in the 120v setting. I currently cannot run 208v shore power. I understand that I can rewire the 240V transformer and put in another switch to handle 208v. If I run into 208v currently I am on a single 30amp circuit. On 30 amps I can run the two AC units plus refrigeration and lights with 30 amps so the 5000kva should be adequate for my needs. I need to iron this whole mess out and get the new multiplex to switch properly.
For charging underway I plan on getting a Buck Boost 50amp DC-DC charger to go from the port start battery to the house batteries.
I like the idea of monitoring with a Cerbo GX and Victron Energy Touch 50. We have starlink.
I plan on replacing the Orion GX 12/24V DC-DC 10 charger that I am charging the Stern thruster AGM's with and replacing it with a Orion 24/24-10 DC-DC.
I also plan on replacing the Autopilot hydraulic pump. The current pump is a 24V pump wired to three relays to be able to run in on 12V and is leaking. It is sitting right next to the AGM's for the stern thruster.

All total about $5k

 

[Serene]

I currently have a 2023 multiplex 12/2000va/120/80 that I can run refrigeration and light loads with while underway. The automatic switching between shore power and inverter has never worked properly and requires turning nearly everything off before asking it to switch and even then can take a couple of minutes. Then I can switch things back on. (I need more digging into this problem)

My Quattro switches instantly from shore to inverter. I don't even need to think about it, so definitely look into why you are having this problem. There is a setting for 'UPS' mode which is supposed to speed up the switching process, but if your generator output is not stable, the Quattro will keep switching to inverter mode even if the generator is running, so best to not enable it unless you really need it.

I have disabled UPS on my Quattro and can still switch from shore to inverter without interruption.

I like the idea of monitoring with a Cerbo GX and Victron Energy Touch 50. We have starlink.

I have the Cerbox GX and Touch 50 too. Debated whether to get the Touch 70 but to be honest the 50 is perfectly adequate and saves a few dollars. With the VRM app on my iPad I can see the same console screen as the Touch 50 anyway if I want it larger. Mine works through Starlink and has been flawless so far.

All total about $5k

Money well spent in my opinion. I'm very happy with my installation.

 

[PierreR]

Thank You Serene

 

[twistedtree]

I plan on replacing the 12/2000va/120/80 with a multiplex 2-24/5000/120/95. I have purchased two 300 amp hour 12.8 volt LiFePO4 batteries for a house bank that would be charged in series (25.6v) but pull off 12.8V for 100 amp 12v DC panel.

How is 12V being "pulled off" the 24V bank? Under no circumstances should you tap/draw power off the intermediate 12V point in a 24V bank. So if that's what you were thinking, don't do it. If the plan is to use a 24V to 12V converter of some sort, then no problem.

 

[twistedtree]

I agree with others that tme Multi should switch seamlessly between inverting and incoming shore or gen power. If it's not, something is wrong.

If I followed correctly, you have two 120V segments on your boat. On shore power you take 120/240V split phase from the dock and each leg feeds one of the segments. There are no 240V loads. Is that correct? How is the generator set up? Does it output 120/240V split phase, just like the shore power? How are the loads split up between the two 120V segments? It's common to have HVAC on one segment, and everything else on the other segment. Is that how you are set up? If so, will the inverter only power the HVAC segment? Or do you somehow plan to power both segments, and if so, how?

 

[PierreR]

I agree with others that tme Multi should switch seamlessly between inverting and incoming shore or gen power. If it's not, something is wrong.

If I followed correctly, you have two 120V segments on your boat. On shore power you take 120/240V split phase from the dock and each leg feeds one of the segments. There are no 240V loads. Is that correct? How is the generator set up? Does it output 120/240V split phase, just like the shore power? How are the loads split up between the two 120V segments? It's common to have HVAC on one segment, and everything else on the other segment. Is that how you are set up? If so, will the inverter only power the HVAC segment? Or do you somehow plan to power both segments, and if so, how?

The problem you have identified here I think is related to the non switching multiplex.

The boat originally came with two thirty amp shore power. One for the power panel and one for the AC units. The generator was wired for 120V only and feed both sides of the panel. One 30 amp 120v also feed both sides of the panel.
Someone along the way removed one 30 amp service and replaced it with a 50 amp 240/120 split phase circuit through an isolation transformer.
In order to accomplish this they installed a rotary switch that reads 120v -off- 240v. If the rotary switch is in the 120v side it receives power from the single 30 amp circuit and feeds both sides of the panel with single phase 120v. With the switch in this position AC will also run but you can only run the two smaller AC units. Three will overload it. Each AC unit has it's own panel and breaker.
With the switch in the 240v position the power is pulled from the 50 amp service and measures a split phase between each side of the panel. 240V even though I do not have anything on board with 240v.
A bit un nerving to me. With the switch in the 240v position you can run anything on board that you want up to the 60 amps on the panel plus the AC.
To use the Generator the switch must be in the off position and the breaker switch in on each side of the panel to go from shore to generator. The generator is 9kw wired 120v.
To run the invertor the switch must be in the off position isolating the transformers. both sides of the panel work on 120v. When switching back to shore power, either transformer nearly everything must be off the invertor for it to switch to charge mode and recognize shore power. That can take up to a minute.
Nothing wants to work on 208v shore power. I get around 198 volts.
I had planed on fixing the shore power problem separate from the new system but maybe that is not possible. I have zero wiring diagrams and must trace every circuit I work on.

 

[PierreR]

How is 12V being "pulled off" the 24V bank? Under no circumstances should you tap/draw power off the intermediate 12V point in a 24V bank. So if that's what you were thinking, don't do it. If the plan is to use a 24V to 12V converter of some sort, then no problem.

I am not sure I understand what you are saying but I suspect that is what I had planed to do. Not sure why that is not a good idea, so not sure what you mean
Are you saying that if I go that route then I need a second DC/DC convertor to feed the 100 amp 12V panel.
If that is so then I might be much better to say 12V and put in two parallel 3000 watt multiplex at 12v than a 5000 at 24V.

 

[DDW]

If you have two batteries in series to make 24V, and are charging them with a 24V charger, then tapping one to feed some 12V loads is bad. The reason is it will discharge that one, and only that one, to feed the 12V loads. Then when the 24V charger comes on, you have unbalanced cells so one battery will get overcharged and the other undercharged. There is no way for them to rebalance, unless there is a discrete balancer installed, and that is really just a bandaid for poor system design. It is really better to buy 24V batteries for a 24V system because the internal balancers will keep everything good. Even without the 12V load, two drop in 12V in series have an opportunity to get out of balance. But certain, if tapping a 12V load.

I'd pop for the 7" Cerbo screen if mounting space is available. Have both, like the 7" better. Doesn't show anything more, but easier to read from a distance, and easier for fat fingers to manipulate.

 

[PierreR]

If you have two batteries in series to make 24V, and are charging them with a 24V charger, then tapping one to feed some 12V loads is bad. The reason is it will discharge that one, and only that one, to feed the 12V loads. Then when the 24V charger comes on, you have unbalanced cells so one battery will get overcharged and the other undercharged. There is no way for them to rebalance, unless there is a discrete balancer installed, and that is really just a bandaid for poor system design. It is really better to buy 24V batteries for a 24V system because the internal balancers will keep everything good. Even without the 12V load, two drop in 12V in series have an opportunity to get out of balance. But certain, if tapping a 12V load.

I'd pop for the 7" Cerbo screen if mounting space is available. Have both, like the 7" better. Doesn't show anything more, but easier to read from a distance, and easier for fat fingers to manipulate.

Okay, now I see it. Unlike parallel, one battery will not balance the other. I was confused because Sideshift had me use two twelve volt in series for a stern thruster and pulled a small 12 v load off the midpoint to run the controller. I did not disconnect the 12v load when I stored the boat and only disconnected it two months later. I bet one battery is high and the other nearly dead instead of both equal.
That kinda changes the whole plan, sticking with 12v all the way through.

 

[DDW]

On flooded LA batteries you can get away with this for small loads, because they can be balanced by just overcharging them. Harder on AGM or particularly LFP, as overcharging them causes many problems.