Large load off grid Marine System

[IsaakOker]

Hi everyone,

I have a few doubts about a solar powered system I’m going to be installing on a sailboat.

Figured out:

1) 400-600Amph battery Lifepo4
2) 3000w inverter
3) 1000w solar panels
4) Renogy solar charge controller

Not clear yet is if I should go with a 24 or 12vdc system.

On the boat, everything is operated 12v but loads are low as the highest is a fridge & freezer except for an anchor winch which draws 90Amp @ 12v.

What do you think? Is it better to go with 24v system for smaller cables and 1 single solar charge controller but then a 90+ DC-DC step down to power the anchor winch or better keep batteries at 12v and save the DC-DC but have larger cables and another solar charge controller?

Also, I’m going to be running a 2000w induction 120v off the inverter.

Any thoughts?

 

[sunshine_eggo]

Hi everyone,

I have a few doubts about a solar powered system I’m going to be installing on a sailboat.

Figured out:

1) 400-600Amph battery Lifepo4
2) 3000w inverter
3) 1000w solar panels
4) Renogy solar charge controller

Not clear yet is if I should go with a 24 or 12vdc system.

On the boat, everything is operated 12v but loads are low as the highest is a fridge & freezer except for an anchor winch which draws 90Amp @ 12v.

What do you think? Is it better to go with 24v system for smaller cables and 1 single solar charge controller but then a 90+ DC-DC step down to power the anchor winch or better keep batteries at 12v and save the DC-DC but have larger cables and another solar charge controller?

Also, I’m going to be running a 2000w induction 120v off the inverter.

Any thoughts?

3000W is on the line.

3000W/12V/.85 = 294A for peak output with 12V battery

Half that for 24V.

Additionally, Ah yields different capacity for different voltage.

500Ah * 12V = 6kWh
500Ah * 24V = 12kWh

I suspect the anchor winch may spike well above 90A when it first starts. This would make a 24-12V converter expensive and robust.

 

[IsaakOker]

Yep, totally agree & that’s why although the simply and easy way to go would be 12v, I’m more inclined to go 24v.

But, if I go to 24v I need to convert up to 90Ah into 12v for the winch. (The winch will typically draw 30-60Ah actually. It’s only 90Ah if under very large load)

Now, I have one other option but I don’t know if it’s intelligent and that would be to have the system in 24v, have a small 15-20Ah DC-DC converter for the 12v system and have the winch hooked up to the engine starter which is 12v anyways BUT I have to be able to charge this battery without starting the engine.

Could I charge the engine lead acid battery through the same solar charge controller or could I charge it from the LFP battery bank?

 

[sunshine_eggo]

Yep, totally agree & that’s why although the simply and easy way to go would be 12v, I’m more inclined to go 24v.

But, if I go to 24v I need to convert up to 90Ah into 12v for the winch. (The winch will typically draw 30-60Ah actually. It’s only 90Ah if under very large load)

Now, I have one other option but I don’t know if it’s intelligent and that would be to have the system in 24v, have a small 15-20Ah DC-DC converter for the 12v system and have the winch hooked up to the engine starter which is 12v anyways BUT I have to be able to charge this battery without starting the engine.

If I felt compelled to go 24V, and your winch need is a compelling reason to stick with 12V provided the LFP battery can handle the current, I would prefer that except rather than a DC-DC converter, use an actual DC-DC charger that addresses your concern below:

Could I charge the engine lead acid battery through the same solar charge controller or could I charge it from the LFP battery bank?

 

[IsaakOker]

So you

If I felt compelled to go 24V, and your winch need is a compelling reason to stick with 12V provided the LFP battery can handle the current, I would prefer that except rather than a DC-DC converter, use an actual DC-DC charger that addresses your concern below:

believe it’s then best to go for plan C and have the system in 24v but the winch hooked up to the engine battery with a DC-DC charger from the LFP bank to the lead acid?

 

[sunshine_eggo]

So you

believe it’s then best to go for plan C and have the system in 24v but the winch hooked up to the engine battery with a DC-DC charger from the LFP bank to the lead acid?

Not necessarily best given the simplicity of all 12V, BUT probably the best solution for heavy 12V loads on a 24V system.

 

[IsaakOker]

I mean, the thing is that the induction cooktop is rated at 2kw Max so that’s let’s say 170Ah @ 12v.

It’s not scary 250-300Ah running through the cable although obviously if the cooktop is at max and a few other things run, it could have momentaneous peaks of 3kw or during a few minutes but nothing like 3kw running for 30minures at a time.

Not sure, basically I can’t find a big affordable DC-DC step-down converter for the anchor winch but a 24v system would allow me to go with just 1 solar charge controller …

Let's see what I go with..

 

[HarryN]

I would definitely not use a renogy solar charge controller, regardless of the rest of your system.

In theory:

( 1 000 watts of solar ) / ( 12 volts ) ~ 100 amps. That is a pretty large solar charge controller - perhaps only 1 or 2 on the market

( 1 000 watts of solar ) / ( 24 volts ) ~ 50 amps, so that is still pretty robust, but an off the shelf Victron 100 / 50 or similar could work.

If I was personally building it, I would do it in 48 volt but I am not a fan of DIYers doing their first project in 48 volt. Nonetheless,

( 1000 watts of solar ) / (48 volt ) ~ 25 amps - which might result in a dramatically smaller solar charge controller vs the other two.

It is tempting to just use a 12 volt starter battery for the 12 volt loads and keep it charged from a higher voltage pack, either using DC - DC or the inverter. Mostly because that winch is quite a large load.

Perhaps it makes sense to replace the winch with a higher voltage model so that it can run on the higher battery voltage? That path would make life easy.

 

[IsaakOker]

Yep, was thinking of changing the winch motor to a 24v but that would cost more than 4 charge controllers combined hahaha

I mean, 50amps in a Victron or other solar charge controller isn’t really that big of a problem I would say…
100amps is obviously more of an issue as the cable run is fairly long so would have to bring in an as high of a voltage possible to reduce cable size.

That’s the main reason for 24v. Cost of cables and efficiency from panels to batteries.

What’s wrong with the Renogy 40 or 50amp solar charge crontrolelr?

 

[HarryN]

Yep, was thinking of changing the winch motor to a 24v but that would cost more than 4 charge controllers combined hahaha

I mean, 50amps in a Victron or other solar charge controller isn’t really that big of a problem I would say…
100amps is obviously more of an issue as the cable run is fairly long so would have to bring in an as high of a voltage possible to reduce cable size.

That’s the main reason for 24v. Cost of cables and efficiency from panels to batteries.

What’s wrong with the Renogy 40 or 50amp solar charge crontrolelr?

A couple of things.

The manuals indicate that you can fine tune the settings - in real life you cannot, esp for LiFe.

They have very high standby power draw - nearly as much as an inverter. This happens 24 hrs / day, so on an overcast day and all night long, they are burning up power.

They pull their operating power from the battery pack vs from the solar. This seems like a minor point, but what can happen is that constant parasitic load can drain the batteries down below the BMS turn off point. Since it operates off of the battery pack, if the LiFe batteries have gone low, the solar charge controller will not generate any power - even in full sun.

I normally don't use their products in general but a customer had already purchased a rover and asked me to use it in his van in exchange for a discount for not using my normal one. Big mistake. It would have cost me less in time, trouble, (and hiring another guy to help since I was stuck ) with it to just throw that thing in the garbage can and eat the discount.

The SOC info that it broadcast is incorrect and designed for use with AGMs based on voltage - this confused the customer since I also included a real SOC power monitor based on a shunt. Had a heck of a time getting the customer to ignore their SOC info.

If I am ever in the same position, that is what I will do - toss and just move on.

 

[IsaakOker]

Ok

A couple of things.

The manuals indicate that you can fine tune the settings - in real life you cannot, esp for LiFe.

They have very high standby power draw - nearly as much as an inverter. This happens 24 hrs / day, so on an overcast day and all night long, they are burning up power.

They pull their operating power from the battery pack vs from the solar. This seems like a minor point, but what can happen is that constant parasitic load can drain the batteries down below the BMS turn off point. Since it operates off of the battery pack, if the LiFe batteries have gone low, the solar charge controller will not generate any power - even in full sun.

I normally don't use their products in general but a customer had already purchased a rover and asked me to use it in his van in exchange for a discount for not using my normal one. Big mistake. It would have cost me less in time, trouble, (and hiring another guy to help since I was stuck ) with it to just throw that thing in the garbage can and eat the discount.

The SOC info that it broadcast is incorrect and designed for use with AGMs based on voltage - this confused the customer since I also included a real SOC power monitor based on a shunt. Had a heck of a time getting the customer to ignore their SOC info.

If I am ever in the same position, that is what I will do - toss and just move on.

Ok, sounds like a point.

Do you know what the standby draw is of the Renogy vs Victron ?

Also, speaking of standby power consumption, would you go with the giandel 3000w inverter or another budget one?(haven’t found any standby power consumption tests on the giandel)

 

[HarryN]

Ok

Ok, sounds like a point.

Do you know what the standby draw is of the Renogy vs Victron ?

Also, speaking of standby power consumption, would you go with the giandel 3000w inverter or another budget one?(haven’t found any standby power consumption tests on the giandel)

Not off hand but someone probably does.

There is a thread on this forum somewhere that people have posted their own results for various inverter standby power consumption. I remember seeing it in the past few days.

I don't know if a 3000 watt G inverter can power a 2000 watt inductive load or not. That is one of the bigger challenges for budget inverters, they can run resistive loads but often cannot power much of an inductive load.

I am personally not a fan of inductive cook tops because my wife uses cookware that is coated aluminum (so not induction compatible ) but I get it that they are popular with customers. If you could bring yourself to use a coil based cook top, then you could easily use a cheap inverter vs a more expensive one.

 

[HarryN]

For a sail boat power system, it might make sense to look at genasun. Their controllers were specifically designed for that application.

 

[IsaakOker]

Didn’t know about that brand, will look into it!

Most marine systems that don’t have budget issues will actually go with Victron, at least in Europe but I believe all around.

As for the inverter, I couldn’t find that thread but other older threads talk about very low idle consumption by Giandels for the 2kw so I suppose the 3kw is also low at idle but I’ll try to get the spec sheet.

Currently I can afford the Victron SCC but definitely not the Multiplus 3kw ?

 

[Skypower]

I’d be going with a lead acid deep cycle dedicated for the winch located near the winch. That’s a great way to go for thrusters too. That battery can be charged several ways with much smaller wires. Unless your engine or generator’s alternator is 24 volts I’d just stay away from that voltage. 48 is more efficient to invert to 120ac but less efficient to convert to 12 DC however there’s a lot less current for the refrigerator than the induction cooktop. Consider a four battery bank, two voltage system. A lead acid for the winch, a lead acid starting, lithium12v “house” and a 48 volt lithium for the inverter. Also 12v and 48 PV charge controls that you can direct to prioritize the need with PV breakers. I always like to leave the starting battery system isolated so that they are preserved for engine/instrument/navigation. The engine can help with charging the house batteries with relay type isolator and a DC to DC to regulate the output(to save the alternator). If you want to use the engine to charge the 48v system, consider an auxiliary 48 volt alternator. Draw out a system on paper. Use a pencil with an eraser ? Check balance again in the bank account ?

 

[HarryN]

Didn’t know about that brand, will look into it!

Most marine systems that don’t have budget issues will actually go with Victron, at least in Europe but I believe all around.

As for the inverter, I couldn’t find that thread but other older threads talk about very low idle consumption by Giandels for the 2kw so I suppose the 3kw is also low at idle but I’ll try to get the spec sheet.

Currently I can afford the Victron SCC but definitely not the Multiplus 3kw ?

You are not going to save any money using Genasun solar charge controllers.

I have used the Bogart PWM, Victron MPPT, and a midnight solar unit for mobile applications and they are fine. You can make any of those and probably others as well work just fine.

Also have used the genesun units and they work great. Had one on my own van until a pick up ran a red light and took out the van and almost me.

Anyway, they have versions for the solar panel voltage being lower and higher than the battery pack voltage, which can be handy sometimes.

The inventor was an MIT Electrical engineering grad student that likes to sail. What he found is that on a sail boat, there are rapidly moving shadows going all over the place while boating from the sail and rigging, and this happens much faster than most solar controllers can respond, so the controller can be trying to scan for the right settings and never lock in, missing opportunities to charge.

So he made them operate at a higher frequency / fast lock in time - really on a per panel basis, so each solar panel can be locked in quickly and get as much power as possible with the shadows moving around. I believe that they can adjust and lock in something like 15 - 20x / second, vs I have tested them against some other MPPT types and they can take 10 - 15 seconds.

He also hates RF noise, so designed that in as well.

They are the default solar charge controller for my 48 volt / 2 kW inverter class power systems in van applications.

For the 24 volt / 1 kW inverter class systems, I mostly use the bogarts - partly because we have so much overcast weather here in the winter and those are really good for that application.

In case you can't tell, I spend a lot of time thinking about ways to make things work in poor lighting conditions. If you visit San Francisco, you will know why.

Customers bring in all kinds of solar setups that they want to run, so I have tools in the tool kit to make things work.

There are other charge controllers discussed on this forum that are probably good - I just don't have any experience with them.

 

[Skypower]

You are not going to save any money using Genasun solar charge controllers.

I have used the Bogart PWM, Victron MPPT, and a midnight solar unit for mobile applications and they are fine. You can make any of those and probably others as well work just fine.

Also have used the genesun units and they work great. Had one on my own van until a pick up ran a red light and took out the van and almost me.

Anyway, they have versions for the solar panel voltage being lower and higher than the battery pack voltage, which can be handy sometimes.

The inventor was an MIT Electrical engineering grad student that likes to sail. What he found is that on a sail boat, there are rapidly moving shadows going all over the place while boating from the sale and rigging, and this happens much faster than most solar controllers can respond, so the controller can be trying to scan for the right settings and never lock in, missing opportunities to charge.

So he made them operate at a higher frequency / fast lock in time - really on a per panel basis, so each solar panel can be locked in quickly and get as much power as possible with the shadows moving around. I believe that they can adjust and lock in something like 15 - 20x / second, vs I have tested them against some other MPPT types and they can take 10 - 15 seconds.

He also hates RF noise, so designed that in as well.

They are the default solar charge controller for my 48 volt / 2 kW inverter class power systems in van applications.

For the 24 volt / 1 kW inverter class systems, I mostly use the bogarts - partly because we have so much overcast weather here in the winter and those are really good for that application.

In case you can't tell, I spend a lot of time thinking about ways to make things work in poor lighting conditions. If you visit San Francisco, you will know why.

Customers bring in all kinds of solar setups that they want to run, so I have tools in the tool kit to make things work.

There are other charge controllers discussed on this forum that are probably good - I just don't have any experience with them.

One of the few people to bring up this major issue of shadows in marine applications.?