Marine System Upgrade Decisions

[svalvasori]

I'm looking for opinions and pros/cons of different ways to improve my boats energy system. We are away from the dock for 3 nights most weekends in the summer and don't like to micro manage our power usage. The existing system has been working well for the past 7 years, however after adding Starlink, the balance was upset and we end up running the generator more than I would like, but we enjoy the connectivity so that's not going anywhere. We boat in northern Ontario where the sun insolation is 2.5-7.6 (5.1avg).
Some stats from last summer via Victron VRM historical data

• Usage: 5-6 kWh per day
• Solar Production: 1.5-2 kWh per day

Equipment Involved

• Victron Multiplus 12/3000/120
• Victron CerboGX
• Victron SmartShunt
• Victron MPPT 12/45
• 660 W solar (3x 220W hard panels)
• 11 kW diesel generator
• 920 Ah lead acid house bank (8x GC 230Ah)

I see two options

1. Replace lead with 600 Ah lifepo4 and add 120A or so charge capability (closer to .5c). This increases my usable battery capacity and decreases my generator run time (Ideally 1 hr per day, which we would do anyway for hot water and/or to run the oven)
2. Leave the lead acid batteries (they are only 1 season old) and add 500W of solar and controller.

In an ideal world, I'd do both but money doesn't grow on trees, at least not around here. Option 1 is easier since I don't need to have stainless supports welded up to add the panels. I'd be doing all the work myself and while I've never built a lifepo4 battery, it looks like fun.

Let me know your thoughts and any other details you need to make an informed call. Appreciate the input.

Steve.

 

[sunshine_eggo]

Issue with lead acid is the charge rate. I expect you don't want to charge that battery much over 120A.

500W would certainly improve your daily harvest and reduce your generator run need, but likely by less than half.

Starlink probably added about 1.2kWh/day - that's what I see on mine. Have you tried the sleep mode on starlink - where you can define a window where it goes into low power mode? If you have a consistent sleep period, do you need the internet on when you are asleep? The cerbo will store VRM data locally and upload it when starlink wakes back up.

Anything about your current PV arrangement that could be optimized? If shading/partial shading is an issue, losses can be severe. If panels in the same series string are in different orientations, then the lowest performing panel will limit all of them. Rewiring series panels with shading issues in parallel could notably improve performance.

Being that far North, could you hang some lightweight flexible panels vertically off the side of the boat and parallel with your other strings? Winter production with vertical panels is actually pretty good.

In the absence of those tangents, I would go #2 due to the lower cost.

 

[svalvasori]

I agree with charge rate being the largest limiting factor of my lead acid bank. I understood .2c was acceptable, so 180A charge, with solar and my charger I often am at 150A or so. Of course that only lasts until the bank is at 80 or 85%.
I've got the sleep mode on from 1am - 5am, which isn't very long. Some in my family are up late watching shows (teenage kids) and some of us wake up early to work. So not much time when we don't want connectivity.
Current panel setup looks like this - radar is low enough that the sun has to be at a very low angle before it shades the panels. That said, if I add a panel, it would go across the back of the existing ones, exactly where the radar and anchor light are - so I'll need to relocate those. The Starlink dish does shade if the sun is from the port side since it's on the arm that holds the panels up, but at the moment I haven't thought of a better place to put it.

So, yes there is some optimization that can happen here. In full sun, I typically see 435W charge from the 660W of panels - not sure what the average expectation is. I also have a longish wire run from the panels to the MPPT (around 35' or so) so I may be seeing voltage drop over the 10AWG wires.

I could hang panels, but moving panels in and out isn't something I want to get into.

 

[yodamota]

looks like in order to actually charge those batteries adequately you would require at least 3000w of solar to get to .2c. currently looks like you are around 31amps with your 435. so adding 500w will help and bump you up to 60amps.
these amp rating are at 14vdc.
along with the solar panel ratings I am using 80% of the STC rating.

Can you get any charging from the boat motor?

 

[sunshine_eggo]

So, yes there is some optimization that can happen here. In full sun, I typically see 435W charge from the 660W of panels - not sure what the average expectation is. I also have a longish wire run from the panels to the MPPT (around 35' or so) so I may be seeing voltage drop over the 10AWG wires.

Arrangement looks good.

Given:
Panels flat on a roof
Northern latitude
without a lot of spacing behind them for circulation

435W out of 660W sounds pretty good. Would expect winter production to be < 50%.

I could hang panels, but moving panels in and out isn't something I want to get into.

I was thinking something you could hang and quickly secure without the need to attach/detach regularly.

 

[svalvasori]

looks like in order to actually charge those batteries adequately you would require at least 3000w of solar to get to .2c. currently looks like you are around 31amps with your 435. so adding 500w will help and bump you up to 60amps.
these amp rating are at 14vdc.
along with the solar panel ratings I am using 80% of the STC rating.

Can you get any charging from the boat motor?

I might have some issues getting 3kW of solar up there . We are at anchor all weekend, and use the little boats to get around - even if we moved the big boat, the engines run on 32V so it'd be more complex than I'd like.

 

[svalvasori]

435W out of 660W sounds pretty good. Would expect winter production to be < 50%.

Good to know, I always wondered.

I've decided that adding solar (while less expensive) is more difficult (lots to move around and supports to have made) and less predictable with cloudy days, etc. So I'm going to move toward the 600Ah lifepo4 + additional chargers. Some questions about that:

For the small Ah of my bank, I need fairly high charge/discharge. 350A discharge / 300A charge. So I think that's a pair of 12V 4S packs on (2) 200A BMS. We can sometimes get cold in start/end of season say 5-8 degrees Celsius.

1. Many of the BMS I read about sound great, but are designed for 8S+. I'd be interested in suggestions for a BMS that can communicate with Victron Cerbo GX (or be made to), has an option for heating if I need it and has low temp charge cut off. Plus any other cool features I may need. I don't need the cheapest one, but also don't need a $500 BMS. I don't think I want to buy a pre-made battery as I like to be able to fix my own stuff, unless it made a lot more sense cost wise.

2. I understand charging at .5c is harder on the cells - but the reality is I only boat for 5 months per year and that means we are away from shore power for say 70 nights per year. So my cells would likely age out before wear out. Or so I think. does .5c hurt the cells enough to drop their life to less than 1000 cycles? Even 1000 cycles would give me around 14 years of service. I'd likely cycle the cells between 20-90%. It's more important to get them charged as quickly as possible, as long as that doesn't limit them to a REALLY short life. I can add chargers to get me to 300A charge fairly easy.

3. Is there a flaw in this plan that I'm not seeing?

 

[Rocketman]

Here are my thoughts as I was reading - you probably thought of most of these…

The 350ah discharge is something to keep a close eye on.With two batteries you need a bms that can handle 200ah of discharge AND they will be running almost max out - not a good idea.

instead of 2 batteries with four cells of 300ah-ish cells, look at three batteries with 300ah-ish cells. The battery is bigger, the bms’s spread the load even more and my guess is it is much smaller than your current battery bank. (When designing the area consider leaving easy space for a fourth battery- just in case you decide to add it in the future).

What are your plans for winter storage? Off the water - so you can completely disconnect the battery?

Consider adding a Victron PowerIn for a battery bus bar (unless you already have a good battery side bus bar), and plan on equal length battery cables for the lithiums.

Also, because it’s a boat, are you planning on making your own battery box or buying one? Waterproof? Or close enough or not worried about that?

Connecting several bms’s to a Victron GX might be a challenge with the less expensive bms’s. I didn’t connect up my Victron CCGX to my Batrium BMS, even though I originally had that in the plans. I just run my batteries at a more conservative voltages.

Good Luck!

 

[sunshine_eggo]

For the small Ah of my bank, I need fairly high charge/discharge. 350A discharge / 300A charge. So I think that's a pair of 12V 4S packs on (2) 200A BMS. We can sometimes get cold in start/end of season say 5-8 degrees Celsius.

I prefer @Rocketman 's option.

1. Many of the BMS I read about sound great, but are designed for 8S+. I'd be interested in suggestions for a BMS that can communicate with Victron Cerbo GX (or be made to), has an option for heating if I need it and has low temp charge cut off. Plus any other cool features I may need. I don't need the cheapest one, but also don't need a $500 BMS. I don't think I want to buy a pre-made battery as I like to be able to fix my own stuff, unless it made a lot more sense cost wise.

Whelp... First, you don't NEED communication. It can work exactly like you have it setup with the charge parameters tweaked for the new batteries... but...

I've been experimenting with the @Louisvdw dbus-serial driver to interface most BMS with Victron. It does require superuser access to the GX device, and manually installing a driver from the command line. It's very easy. I'm using a simple 4S 120A JBD BMS.

All cells are visible in remote console (or direct console locally):


Some of my recent tinkerings with it:

Pseudo self-discharge exercise

Battery: 4S 25Ah Topband Navitas 3C cells. 120A JBD BMS UART to USB adapter from Overkillsolar Bluetooth module uses the BMS UART connector, so it was not installed. VRM: Raspberry Pi 3 B+ 1GB (RPi) 256G MicroSD Venus OS 3.11 start, 3.12 end @Louisvdw serial battery driver There were NO LOADS...

diysolarforum.com

@Louisvdw original thread (been working for 3 years now):

Victron VenusOS driver for serial connected BMS - JBD / Daly / ANT / JKBMS / Heltec / Renogy / Tian / ECS

I have created a VenusOS driver that can talk to BMS/Batteries that has serial communications (instead of the normal CANbus). RS485/RS232/TTL/UART and Venus 2.80+ have been tested. Currently it works with JBD BMS (LLT Power / Overkill Solar) Daly BMS (Daly Smart BMS / Daly Sinowealth based...

diysolarforum.com

You need a UART to USB module for each BMS, and in most cases, you plug that in where the BT dongle goes, so you lose BT function, BUT all your battery data are logged to VRM.

There is also another driver designed to aggregate multiple connected batteries to the system.

2. I understand charging at .5c is harder on the cells - but the reality is I only boat for 5 months per year and that means we are away from shore power for say 70 nights per year. So my cells would likely age out before wear out. Or so I think. does .5c hurt the cells enough to drop their life to less than 1000 cycles? Even 1000 cycles would give me around 14 years of service. I'd likely cycle the cells between 20-90%. It's more important to get them charged as quickly as possible, as long as that doesn't limit them to a REALLY short life. I can add chargers to get me to 300A charge fairly easy.

Should be fine. Cutting short of 100% helps. Most stress occurs during charging and at higher voltage/soc. Going with 3 batteries per @Rocketman would further help as you'd be below .5C.

3. Is there a flaw in this plan that I'm not seeing?

You won't know until you start.

 

[Rocketman]

Something I touched on but didn’t emphasize…

BMS selection will be a super critical aspect of this project. Be sure and give this section very good thought.

Also, what charging do you have from the boat engine? Are the two systems currently separate for both charging and discharging? Or does the alternator charge the house bank?

Do you have a separate alternator for the house bank with a wakespeed regulator (or equivalent on it)?

 

[svalvasori]

Here are my thoughts as I was reading - you probably thought of most of these…

The 350ah discharge is something to keep a close eye on.With two batteries you need a bms that can handle 200ah of discharge AND they will be running almost max out - not a good idea.

instead of 2 batteries with four cells of 300ah-ish cells, look at three batteries with 300ah-ish cells. The battery is bigger, the bms’s spread the load even more and my guess is it is much smaller than your current battery bank. (When designing the area consider leaving easy space for a fourth battery- just in case you decide to add it in the future).

What are your plans for winter storage? Off the water - so you can completely disconnect the battery?

Consider adding a Victron PowerIn for a battery bus bar (unless you already have a good battery side bus bar), and plan on equal length battery cables for the lithiums.

Also, because it’s a boat, are you planning on making your own battery box or buying one? Waterproof? Or close enough or not worried about that?

Connecting several bms’s to a Victron GX might be a challenge with the less expensive bms’s. I didn’t connect up my Victron CCGX to my Batrium BMS, even though I originally had that in the plans. I just run my batteries at a more conservative voltages.

Good Luck!

I should have been more clear - the 350A was more of a design guideline - it would be for short durations - the max pull I've seen is around 325A and that is through a ClassT 300A fuse. The inverter calls for a 400A fuse but I couldn't find any at the time, still need to fix that. That said, can a pair of 200A BMS take a 300A charge continuous (or say 2 hours)? I can do 3 if needed, but that just ups the cost and I don't need the capacity.

Typically in winter I disconnect all leads from the batteries and leave them in the boat, I would expect lithium is the same, except not to leave it at 100% charge state.

I may do the Victron lynx (is that what it's called), just to get the easy fusing for each battery, but I do already have a pair of 8 post, 600A buss bars that are in use.

What are the impacts of not connecting the BMS to Victron? Is it really anything I need to care about?

 

[svalvasori]

Something I touched on but didn’t emphasize…

BMS selection will be a super critical aspect of this project. Be sure and give this section very good thought.

Also, what charging do you have from the boat engine? Are the two systems currently separate for both charging and discharging? Or does the alternator charge the house bank?

Do you have a separate alternator for the house bank with a wakespeed regulator (or equivalent on it)?

House bank is completely separate. House is 12V, engines are 32V. So no alternator charging to worry about.

Agree with the BMS selection, exactly why I'm looking for some support to point me in the right direction.

 

[svalvasori]

I prefer @Rocketman 's option.



Whelp... First, you don't NEED communication. It can work exactly like you have it setup with the charge parameters tweaked for the new batteries... but...

I've been experimenting with the @Louisvdw dbus-serial driver to interface most BMS with Victron. It does require superuser access to the GX device, and manually installing a driver from the command line. It's very easy. I'm using a simple 4S 120A JBD BMS.

All cells are visible in remote console (or direct console locally):
View attachment 190163

Some of my recent tinkerings with it:

Pseudo self-discharge exercise

Battery: 4S 25Ah Topband Navitas 3C cells. 120A JBD BMS UART to USB adapter from Overkillsolar Bluetooth module uses the BMS UART connector, so it was not installed. VRM: Raspberry Pi 3 B+ 1GB (RPi) 256G MicroSD Venus OS 3.11 start, 3.12 end @Louisvdw serial battery driver There were NO LOADS...

diysolarforum.com

@Louisvdw original thread (been working for 3 years now):

Victron VenusOS driver for serial connected BMS - JBD / Daly / ANT / JKBMS / Heltec / Renogy / Tian / ECS

I have created a VenusOS driver that can talk to BMS/Batteries that has serial communications (instead of the normal CANbus). RS485/RS232/TTL/UART and Venus 2.80+ have been tested. Currently it works with JBD BMS (LLT Power / Overkill Solar) Daly BMS (Daly Smart BMS / Daly Sinowealth based...

diysolarforum.com

You need a UART to USB module for each BMS, and in most cases, you plug that in where the BT dongle goes, so you lose BT function, BUT all your battery data are logged to VRM.

There is also another driver designed to aggregate multiple connected batteries to the system.



Should be fine. Cutting short of 100% helps. Most stress occurs during charging and at higher voltage/soc. Going with 3 batteries per @Rocketman would further help as you'd be below .5C.



You won't know until you start.

I'll have to look into these options in more detail - thank you. I was a unix admin for many years, so no stranger to command line, and can do some basic coding. Most of my boat runs on an open source project called SignalK which is great. Although the older I get, the more I just want stuff to work, so I try to limit my custom integrations to things that simply don't exist in the way I want them.

 

[sunshine_eggo]

I'll have to look into these options in more detail - thank you. I was a unix admin for many years, so no stranger to command line, and can do some basic coding. Most of my boat runs on an open source project called SignalK which is great. Although the older I get, the more I just want stuff to work, so I try to limit my custom integrations to things that simply don't exist in the way I want them.

All I know about SignalK is that VenusOS large has it...

 

[Rocketman]

You asked- What are the impacts of not connecting the BMS to Victron? Is it really anything I need to care about?

Connecting the BMS to Victron GX…

Not connecting it is the same as what you currently have (no bms’s in lead batteries).

If you choose to connect the bms - it uses the DVCC to control the charging and discharging. I decided not to connect it because it really only matters and the very top and very bottom, and I decided to just not push the batteries that hard. Also, the BMS has control of charging and discharging not the Victron chargers. I decided I liked the Victron charging algorithm.

The one really nice thing it can do, (at least with my BMS) is when the battery gets almost full, it will ramp down the charging current so that you get a full perfect balance on the cells every cycle.

I guess there may be another option in connecting the bms to the Victron, that is the bms could report the high cell value and low cell value to display on the Victron screen. But the Victron GX doesn’t give up control and thus doesn’t use the data - report only.

 

[sunshine_eggo]

You asked- What are the impacts of not connecting the BMS to Victron? Is it really anything I need to care about?

Connecting the BMS to Victron GX…

Not connecting it is the same as what you currently have (no bms’s in lead batteries).

If you choose to connect the bms - it uses the DVCC to control the charging and discharging. I decided not to connect it because it really only matters and the very top and very bottom, and I decided to just not push the batteries that hard. Also, the BMS has control of charging and discharging not the Victron chargers. I decided I liked the Victron charging algorithm.

The one really nice thing it can do, (at least with my BMS) is when the battery gets almost full, it will ramp down the charging current so that you get a full perfect balance on the cells every cycle.

I guess there may be another option in connecting the bms to the Victron, that is the bms could report the high cell value and low cell value to display on the Victron screen. But the Victron GX doesn’t give up control and thus doesn’t use the data - report only.

Even without comms, DVCC can be used to limit charge voltage and charge current for any GX connected chargers.