Sailboat going all Victron

[Horsefly]

I'm helping someone migrate from AGM house batteries to a couple of DIY 4s 280Ah batteries that I'm building for him. In the process, he is getting rid of lots of very old equipment that is not compatible with LFP. Although I don't have much experience with Victron, I told him I thought it was probably the best choice, so he is going all-in on Victron. So now I need to control this monster I seem to have created. I'm hoping some folks here with Victron experience can weigh in on a couple of questions.

So far his shopping list includes:

• Multiplus II 2000w inverter with 80A charger
• Cerbo GX and GX Touch screen
• 2 x SmartSolar MPPT 100/30 charge controllers
• A bunch of other stuff to manage the connection to his alternator (Balmar stuff, mostly)

I've already purchased 2 Victron SmartShunts, and was planning on putting one on each of the two 280Ah batteries.

Besides the LFP house battery, he will have two other battery banks: a single 100Ah AGM starter battery, and 2 parallel 100Ah AGMs for the bow thruster and windlass. Both of these banks will be charged via DC-to-DC chargers from the LFP battery. The LFP battery will be charged from shore, solar, a 100A Balmar alternator with a Balmar MC-618 regulator (programmed for LFP), and maybe wind in the future.

Questions:

1. I would assume that if I wire all this stuff together on the VE.bus, the Multiplus charger and MPPTs can use the voltage sense from the SmartShunts to know the actual voltage at the batteries, and that I don't need a Smart Battery Sense. True?
2. Will the Cerbo and Touch screen know what to do with two SmartShunts?
3. Alternatively for #1 and #2, he is willing to get a BMV-712 Battery Monitor, which I suppose I would put across the two LFP batteries to give a combined status, like it was one 560Ah battery. If the answer to #1 and #2 is yes (that the two SmartShunt's will suffice), I'll tell him to skip the BMV-712.
4. I assume we will buy Victron DC-to-DC chargers, but I haven't looked at that. Do these also talk to the Cerbo?

 

[mitiempo]

Why 2 house banks? Much better to control with one.

 

[Horsefly]

Why 2 house banks? Much better to control with one.

I had to go re-read what I had said, but I don't think I said there were two house banks. There are three banks:

1. Bow Thruster and Windlass Bank - 2 parallel 100Ah AGM batteries
2. Engine / starter - 1 100Ah AGM battery
3. House - 2 280Ah 4s LFP batteries (4s2p) for everything else

I persuaded him to not go LFP for the bow thruster and windlass because the current draw from the Bow Thruster (480A) would push the limits of whatever BMS I could get.

 

[mitiempo]

......... a couple of DIY 4s 280Ah batteries that I'm building for him.

a BMV-712 Battery Monitor, which I suppose I would put across the two LFP batteries to give a combined status, like it was one 560Ah battery. If the answer to #1 and #2 is yes (that the two SmartShunt's will suffice), I'll tell him to skip the BMV-712.

Sounds like 2 house banks from the above. If it is one bank you should only need one Smart Shunt.

Which BMS are you using?

 

[Horsefly]

No, it's just two parallel batteries, connected into one house bank. I keep reading what I wrote, and I just can't see where you are thinking two house banks. To me, a "bank" is one or more batteries connected together receiving the same charge sources and servicing the same loads. A set of one or more batteries that have different loads is a separate "bank". If that isn't the correct interpretation, I've got to go back to square one.

Each 4S 280Ah battery has a JBD 150A BMS, a Smart Shunt, and probably a Heltec active balancer. My thinking on the two Smart Shunts was so we could see if the two batteries were not splitting the current about equally, but I can probably achieve that with just the BMS via the Bluetooth app.

But it sounds like I could use one Smart Shunt for the bank, save my buddy some money on the BMV, and get the monitoring of the bank on the Cerbo GX and for each individual battery in the house bank from the BMS.

The thing I was trying to figure out is this: I know that the Cerbo GX can take in data from multiple shunts, but can I configure it to know that the two shunts combine for the total current / Ah of the bank?

 

[noenegdod]

I've already purchased 2 Victron SmartShunts, and was planning on putting one on each of the two 280Ah batteries.

I thought you were having 2 as well. This lead me to think you were having 2 separate house batteries

 

[rmaddy]

1. With a shunt you do not need the battery sense
2. You only need one shunt. You have two batteries in parallel. Shunt is for the whole battery bank.
3. The BMV-712 is basically a SmartShunt with a display. But it also adds one additional monitoring point. It can be used to to either monitor the voltage of another bank, monitor the primary bank temperature, or monitor the mid-point voltage of the primary bank with batteries in series.

 

[Horsefly]

I thought you were having 2 as well. This lead me to think you were having 2 separate house batteries

I guess it still is a terminology thing. To me, I do have two house batteries, wired in parallel to one house bank. I guess I needed to be more clear. The fact that I thought I was using 2 smart shunts - which seems to be overkill - is contributing to the confusion. Sorry.

 

[noenegdod]

Just out of curiosity, In the boating world a lot of people go with Balmar. Is there a reason very few use Mechman? They do have a line they sell for marine service but they also have a 400a line as well.

https://www.mechman.com/alternators...te-series-alternator-for-88-95-gm-truck-blue/

 

[Horsefly]

1. With a shunt you do not need the battery sense
2. You only need one shunt. You have two batteries in parallel. Shunt is for the whole battery bank.
3. The BMV-712 is basically a SmartShunt with a display. But it also adds one additional monitoring point. It can be used to to either monitor the voltage of another bank, monitor the primary bank temperature, or monitor the mid-point voltage of the primary bank with batteries in series.

Great data! Thanks!

So the shunt (whether smart shunt or BMV) will provide the voltage sense of the bank so I don't need the separate sense device. Good!

The info on the BMV-712 is really good to know. So I could have the BMV second point be for the Bow Thruster / Windlass bank? That sounds useful! I assume I would need a separate shunt over on the second bank in order for the BMV to monitor it? Could I use one of the Smart Shunts there?

I'll explain all this to him. Sounds like if he decided he wants the BMV-712 I will have two unused Smart Shunts for sale. If he decides to save money and not go with the BMV-712 I'll still have one Smart Shunt to get rid of.

 

[Horsefly]

Just out of curiosity, In the boating world a lot of people go with Balmar. Is there a reason very few use Mechman? They do have a line they sell for marine service but they also have a 400a line as well.

https://www.mechman.com/alternators...te-series-alternator-for-88-95-gm-truck-blue/

Hopefully someone else can answer that question. I only know that he already has a Balmar alternator and regulator, and wants to upgrade to the MC-618 regulator because his existing regulator (from memory, ARS-5?) is too hard to program.

 

[rmaddy]

For details on monitoring the voltage of a second battery with the BMV-712 you can look at its Quick Install Guide:

BMV-712 Smart - Victron Energy

Communicate wirelessly between products and simplify system installation and enhance performance using the BMV-712 Smart. Find a dealer now.

www.victronenergy.com

Of course the manual has more info too. But you do not need an extra shunt to monitor the 2nd bank's voltage.

 

[rmaddy]

I just looked at the SmartShunt. It can also monitor a 2nd bank's voltage and it can be connected to a Cerbo. So there doesn't seem to be a reason to use a BMV-712 since you already have the SmartShunt.

 

[Horsefly]

For details on monitoring the voltage of a second battery with the BMV-712 you can look at its Quick Install Guide:

BMV-712 Smart - Victron Energy

Communicate wirelessly between products and simplify system installation and enhance performance using the BMV-712 Smart. Find a dealer now.

www.victronenergy.com

Of course the manual has more info too. But you do not need an extra shunt to monitor the 2nd bank's voltage.

Thanks for that. I saw the manual, but the quick start gets to the point more quickly. So it really just monitors the voltage of a second bank, not the state of charge. Darn. Ok.

 

[Horsefly]

I just looked at the SmartShunt. It can also monitor a 2nd bank's voltage and it can be connected to a Cerbo. So there doesn't seem to be a reason to use a BMV-712 since you already have the SmartShunt.

Yeah, I think you are right. He doesn't currently have any way to monitor the Bow Thruster bank, and it sounds like he abuses that bank. Maybe I'll suggest using the second Smart Shunt over there, and at least checking it via Bluetooth now and then.

 

[ohthetrees]

I just finished my Victron heavy install this week. Lots of overlap with your system. A few thoughts:

As others have said, just one shunt for your main house bank.

If you haven’t already bought the balmar regulator, have a look at the Nordkyn VRC-200. All it needs is an alternator with remote voltage sensing and it will work. Great little device, programmable, and made from ground up with LiFePo4 in mind, by a guy who knows more about Lithium than anyone else on the Internet.

Strongly recommend you consider the REC BMS. This is the style that controls contactors, so there are no current limitations of the internal FETS. Just wire to appropriate sized contactors and it can control any size load. (Consider the Blue Sea ML RBS 7013 which only takes about 10 mA from the BMS to actuate and hold. This is the contactor I wish I’d got, so do your own research to confirm it is compatible). The REC BMS also speaks victron. In my setup, the BMS sends voltage, current, SOC, temperature, etc, to the Cerbo to display, so no need for a victron shunt at all. You do need a dumb shunt, or you can attach sense wires to the victron shunt, doesn’t effect function of victron shunt. I already had a BMV 700, but it is redundant, and I wouldn’t get one for a fresh install. But the real magic is that the REC BMS can send voltage and current requests to the Cerbo, and then the Cerbo controls the whole suite of victron charging devices to provide the voltage and current requested by the BMS. This is great because at the end of charging, the BMS can taper off charge current and request a specific voltage within its balancing window, so it has plenty of time to balance without over charging. This benefit is fairly theoretical for me now because my pack is new and in balance already.

 

[Horsefly]

If you haven’t already bought the balmar regulator, have a look at the Nordkyn VRC-200. All it needs is an alternator with remote voltage sensing and it will work. Great little device, programmable, and made from ground up with LiFePo4 in mind, by a guy who knows more about Lithium than anyone else on the Internet.

I'll pass that along. I looked at the web page for it, and I do like that it is built for LFP, whereas all the Balmar stuff can be programed for LFP but it is generally not one of the defaults. Looking at the manual, it seems kind of clunky to configure, with set screws and test points. On of the things he doesn't like about the current Balmar regulator is that it is so difficult to program, especially down in the engine compartment.

Strongly recommend you consider the REC BMS. This is the style that controls contactors, so there are no current limitations of the internal FETS. Just wire to appropriate sized contactors and it can control any size load. (Consider the Blue Sea ML RBS 7013 which only takes about 10 mA from the BMS to actuate and hold. This is the contactor I wish I’d got, so do your own research to confirm it is compatible). The REC BMS also speaks victron. In my setup, the BMS sends voltage, current, SOC, temperature, etc, to the Cerbo to display, so no need for a victron shunt at all. You do need a dumb shunt, or you can attach sense wires to the victron shunt, doesn’t effect function of victron shunt. I already had a BMV 700, but it is redundant, and I wouldn’t get one for a fresh install. But the real magic is that the REC BMS can send voltage and current requests to the Cerbo, and then the Cerbo controls the whole suite of victron charging devices to provide the voltage and current requested by the BMS. This is great because at the end of charging, the BMS can taper off charge current and request a specific voltage within its balancing window, so it has plenty of time to balance without over charging. This benefit is fairly theoretical for me now because my pack is new and in balance already.

I haven't looked at REC in a while. It does sound like it integrates well with Victron. I know the JBD BMS well, so had leaned towards that. He originally gave me some numbers for the house loads, and so I bought smaller 80A JBD BMS's for both batteries. Then we went through everything together and realized he needed bigger currents, so I now have two 150A JBD BMS's coming. I'd hate to think I purchased four BMS's that we won't use now. In addition, it sounds like I'll have no use for the Victron shunts I already bought. Ugh. Anyway, I'll take a look at the REC again.

 

[Horsefly]

Wow! So if I went with REC it looks like I would have to have 2 of the master BMS units ($330 ea), 2 contactors ($169 ea from REC, don't know about the one recommended by @ohthetrees), the PC software to configure the BMS's ($104), a couple of REC current shunts ($66 ea), and probably a couple of the Victron CANbus cables ($28 ea). I'm guessing that is over $1000 for the BMS. Am I missing something?

 

[wholybee]

Hopefully someone else can answer that question. I only know that he already has a Balmar alternator and regulator, and wants to upgrade to the MC-618 regulator because his existing regulator (from memory, ARS-5?) is too hard to program.

If he hasn't ordered the MC-618 yet. Look at the Wakespeed ws-500. The MC-618 is just as stupid difficult to program as the ARS-5, unless you go all in with Balmar and go with their battery monitor and bluetooth interfaces as well. If you have the balmar battery monitor, then you can program the 618 through that. It a terrible design, and I can not recommend it. The Wakespeed is the better option.

I hadn't heard of Mechman, but just looked at the site. The Mechman regulator seems to be a very basic dumb type. Just set a voltage with a pot. The Balmar regulator is a multistage smart charger, fully programmable with what voltages each stage should be, temp sensors on both the alternator and battery, and will protect the alternator from overheating if you run it all out for too long. It fully supports Lifepo4 batteries, and can be set to stop charging after the battery is fully charged. Wakespeed makes a regulator that imho is even better, the balmar design being pretty old, even the "new" mc-618 isn't much of an upgrade.

I can't judge the alternators from a photo. But must auto type alternators are only rated for intermittent use at the full current. That is, if you run a 100A auto alternator at 100A for 10 hours straight, you will kill it. Marine alternators are rated to run at these currents for longer periods of time.

 

[Horsefly]

If he hasn't ordered the MC-618 yet. Look at the Wakespeed ws-500. The MC-618 is just as stupid difficult to program as the ARS-5, unless you go all in with Balmar and go with their battery monitor and bluetooth interfaces as well. If you have the balmar battery monitor, then you can program the 618 through that. It a terrible design, and I can not recommend it. The Wakespeed is the better option.

I passed that on. He had already swallowed hard and said he would pay the extra for the battery monitor and bluetooth to avoid the stupid magnetic reed switch programming of the Balmar. I've seen the WS-500 mentioned elsewhere associated with the Cerbo GX, so I'm guessing that is a really good suggestion. Thank you @wholybee !!!