Electrical plans for off-grid boat ....

[noelex]

One concern with the Integral system is the side load on the front of the engine. Depending on the engine, this is sometimes well above the manufacturers’ recommendations. Whether this will lead to long term problems is not clear.

An alternative to the Integral system is a high capacity large frame alternator. This will not produce as much power (around 2-3 kW is typical), but can be tailored to be within the manufacturers’ recommended maximum side loading. It is also a simpler and much cheaper system with no proprietary parts.

Nevertheless, the Integral system is very clever technology and most owners seem happy with their choice.

My other suggestions would be to add multiple controllers for your 1 kW solar array. This is more efficient and adds valuable redundancy, generally for little extra cost. If you do not do this with four panels extra fusing may be required on the solar panel side of the controller (if you plan on parallel wiring). Also the main fuse for the lithium house bank looks like an ANL model. I would use a T class or similar fuse with a high IC.

 

[Buck Turgidson]

Don't plan on using the current smart lithium series of batteries from Victron, they are about to be replaced and are no longer available to order. I'm told the new product launch will be this month. Shame I already bought a BSM before I found out the battery wasn't available

 

[B27]

The Integrel system can produce around 6 kW at idle, but of course it won't do that if the power has nowhere to go. This is why pairing it with Lithium is the game changer .... Lithium batteries with a less than 80% charge will pretty much take anything you can throw at them. They also don't mind being cycled between 20% and 80%,
....

Are you talking of car lithium cells rather than LIFEPO4?

 

[Baggywrinkle]

Are you talking of car lithium cells rather than LIFEPO4?

No, LiFePo4 ... the data sheet for the batteries in the diagram specify a max charge current of 400A which at 51,2V is 20kW ... the recommended is less than or equal to 100A, which is a more sensible 5,1kW which the Integrel will supply with no problem - I might up the capacity to make full use of the Integrel.

 

[Baggywrinkle]

My other suggestions would be to add multiple controllers for your 1 kW solar array. This is more efficient and adds valuable redundancy, generally for little extra cost. If you do not do this with four panels extra fusing may be required on the solar panel side of the controller (if you plan on parallel wiring). Also the main fuse for the lithium house bank looks like an ANL model. I would use a T class or similar fuse with a high IC.

The problem I encountered when trying to do that is that the battery bank is 51,2V ... split the array up into smaller arrays and you can't achieve the start-up voltage for the MPPT when the panels are hot, voltage needs to be higher than the battery voltage of the system it is charging accross the entire temperature range of the panels. Try it in the Victron MPPT configurator, it offers no options if you start splitting a 1000W system with large rigid panels (4 x 250W) into multiple strings at a battery voltage of 48V.

My solution is to carry a spare MPPT.

 

[Baggywrinkle]

I do hope Baggy continues with this thread and is not discouraged by the general scepticism ( including mine) as it's a new development and deserves to be explored by someone with the balls and commitment to invest his hard earned beer tokens in it. Otherwise we will never know how effective, good or bad it is.

Not giving up quite yet

 

[Baggywrinkle]

One concern with the Integral system is the side load on the front of the engine. Depending on the engine, this is sometimes well above the manufacturers’ recommendations. Whether this will lead to long term problems is not clear.

An alternative to the Integral system is a high capacity large frame alternator. This will not produce as much power (around 2-3 kW is typical), but can be tailored to be within the manufacturers’ recommended maximum side loading. It is also a simpler and much cheaper system with no proprietary parts.

Nevertheless, the Integral system is very clever technology and most owners seem happy with their choice.

I did worry a bit about side loading, but realised it is loading in a different direction to the already fitted alternator, I'm just hoping the combination of both side-loading vectors results in a net side loading that is still within spec. I'd be surprised if the integrel team didn't at least think about this aspect as they provide the engine mount kit, and must warranty it all.

 

[noelex]

The problem I encountered when trying to do that is that the battery bank is 51,2V ... split the array up into smaller arrays and you can't achieve the start-up voltage for the MPPT when the panels are hot, voltage needs to be higher than the battery voltage of the system it is charging accross the entire temperature range of the panels. Try it in the Victron MPPT configurator, it offers no options if you start splitting a 1000W system with large rigid panels (4 x 250W) into multiple strings at a battery voltage of 48V.

My solution is to carry a spare MPPT.

This is a good point. Particularly with high voltage battery systems you need to check that the panel’s Vmp is sufficiently above battery voltage.

Some of the larger panels have sufficiently high voltages for individual controllers to work. If the voltages are still too low with four panels (as you are planning), connecting two panels in series to an individual controller (so two controllers are needed) still has advantages over using a single controller.

 

[Baggywrinkle]

This is a good point. Particularly with high voltage battery systems you need to check that the panel’s Vmp is sufficiently above battery voltage.

Some of the larger panels have sufficiently high voltages for individual controllers to work. If the voltages are still too low with four panels (as you are planning), connecting two panels in series to an individual controller (so two controllers are needed) still has advantages over using a single controller.

Even taking 40V Voc panels, the problem is the voltage drops with temperature, taking 2 panels in series under the start threshold for the MPPT, resulting in the Victron calculator failing to find a suitable controller.



If I up it to two 3 panels then it starts to work ... but three 40Voc panels add up to a corrected Vmpp of 20V over the Vmpp run threshold producing 80Vmpp at 70°C



When I use 4 panels with a lower voltage, 1kW fits very nicely into the range catered for by a 150/35 48V MPPT ... so that's what I went with - and to solve the redundancy/failure issues, I'll carry a swap out spare for the MPPT. Problem solved.

 

[noelex]

Agreed, those panels would not be a good choice for your system. Two panels in series do not have enough voltage and four have a voltage that is too high for your controller.

Have you looked at the Sunpower panels? Many models have a Vmp of around 57v. With two in series you will have better shade tolerance than all four panels connected in series and have two independent solar generating systems. Of course the panels have to fit and be available at a reasonable cost so this option may not work.

 

[B27]

There are such things as buck/boost mppt controllers FWIW.

 

[Baggywrinkle]

Agreed, those panels would not be a good choice for your system. Two panels in series do not have enough voltage and four have a voltage that is too high for your controller.

Have you looked at the Sunpower panels? Many models have a Vmp of around 57v. With two in series you will have better shade tolerance than all four panels connected in series and have two independent solar generating systems. Of course the panels have to fit and be available at a reasonable cost so this option may not work.

48V batteries combined with Victron MPPTs are not a great mix, especially on a boat where you are constrained by the space available for the solar panels. Even using 4 x 47V panels in series, if one went t!ts up I'd have no more 48V solar charging, and I'd have to re-route the solar to the 12V system. It also precludes railing mounted single panels etc.

Then there is the issue of the solar arch ... the backstay is very awkward on this boat, and fitting lots of solar around it neatly will be a challenge as I don't want a massive rear overhang.

Will see how it progresses ... this is a plan subject to change without notice.

One of the constraints that I have put on myself is to use Victron components due to the universal availability and their market leading position.

 

[geem]

One concern with the Integral system is the side load on the front of the engine. Depending on the engine, this is sometimes well above the manufacturers’ recommendations. Whether this will lead to long term problems is not clear.

An alternative to the Integral system is a high capacity large frame alternator. This will not produce as much power (around 2-3 kW is typical), but can be tailored to be within the manufacturers’ recommended maximum side loading. It is also a simpler and much cheaper system with no proprietary parts.

Nevertheless, the Integral system is very clever technology and most owners seem happy with their choice.

My other suggestions would be to add multiple controllers for your 1 kW solar array. This is more efficient and adds valuable redundancy, generally for little extra cost. If you do not do this with four panels extra fusing may be required on the solar panel side of the controller (if you plan on parallel wiring). Also the main fuse for the lithium house bank looks like an ANL model. I would use a T class or similar fuse with a high IC.

NH series fuses are a great choice. A fraction of the cost of class T with 20,000A AIC typically

 

[Zing]

48V batteries combined with Victron MPPTs are not a great mix, especially on a boat where you are constrained by the space available for the solar panels. Even using 4 x 47V panels in series, if one went t!ts up I'd have no more 48V solar charging, and I'd have to re-route the solar to the 12V system. It also precludes railing mounted single panels etc.

You can solve this by feeding solar to each individual 24V battery instead of to the two series connected batteries.

 

[Baggywrinkle]

NH series fuses are a great choice. A fraction of the cost of class T with 20,000A AIC typically

The fuse in the diagram is a placeholder, and not the final design ... If I can get the batteries close enough to the distributor then I can use the fuse in that.

 

[Baggywrinkle]

You can solve this by feeding solar to each individual 24V battery instead of to the two series connected batteries.

I like this idea a lot ... but one battery will bypass the Integrel current measurement and screw up it's charge current calculation ... I think.

 

[B27]

Solar panels are less expensive now, so instead of using the physically large panels which are cheapest per watt, you could look at multiple units of 3 x 20V panels in series, That would give you lots of 60V sources resilient to shading.

Also I wonder if once you have the capital spend of a bloody great diesel generator, does it reduce the optimum amount of solar to cram onto the boat? If you analyse the expected use and solar yield and all that, you may find significantly less panel area only costs you a few beans a year in extra diesel?
It's not like a home system where you get paid to export any excess.

 

[geem]

The fuse in the diagram is a placeholder, and not the final design ... If I can get the batteries close enough to the distributor then I can use the fuse in that.

For the cost of the NH fuse I would suggest fusing the batteries individually as close to each battery as you can. NH fuses are about £8 each plus a fuse holder. They may be overkill but with the incredibly high potential current flow of lithium, its a good thing to have. ABYC standard suggests fusing within 7" of the positive battery terminal. Generally this would be unnecessary for a 100Ah 12v lithium batteries but once you get to larger capacity batteries, it's a nice to have

 

[B27]

For the cost of the NH fuse I would suggest fusing the batteries individually as close to each battery as you can. NH fuses are about £8 each plus a fuse holder. They may be overkill but with the incredibly high potential current flow of lithium, its a good thing to have. ABYC standard suggests fusing within 7" of the positive battery terminal. Generally this would be unnecessary for a 100Ah 12v lithium batteries but once you get to larger capacity batteries, it's a nice to have

See the pbo thread for ranting fundamentalists decrying an extra junction in a battery cable....
Best way to join Positive battery cables

 

[Zing]

I like this idea a lot ... but one battery will bypass the Integrel current measurement and screw up it's charge current calculation ... I think.

It shouldn’t make any difference. If the shunt is on the neg 48V wire as usual and solar is wired before it then it will count current the same. If the Integrel looks at volts instead, or maybe together with current it should still not change its data. An issue might occur with balancing batteries from different solar outputs. I expect the BMS can fix that. Alternatively maybe wire the 2 banks of solar to the 2 batteries at 24V in parallel.