Planned solar setup

[Skeeter]

On my Bristol 42 I have 2 x 8D 1400CCA lead acid batteries designated Port and Starboard Engine and a 6D1100CCA designated Genset.
All batteries have an on/off switch.

The port and stbd start batteries double up as house batteries and I can switch between them or combine them as required for house power.

When away from shorepower I normally keep the Genset battery isolated when not in use to serve as a back up for starting if I run down my Start batteries.


I can run the genset for charging but want to get away from this so I'm looking at installing a 400watt Renology solar system.

The only real power draws I have are the Fridge/ freezer (200W 115AC) which I power using a 1500W invertor (wired to stbd house battery), F/W pump, Sump pump, occasional TV/ laptop, and charging for phones, cordless power tools, etc. I know there are all kinds of calculators out there but wondered if anyone has experience of a similar setup and can offer any good advice.

The current batteries are fairly new so i intend to keep them for now and maybe change them for 6V golf cart batteries as and when they need replacing.

Thanks, Steve

 

[Frosty]

There is some similar info on another thread, but in most cases on a boat you really can't add too much solar. I say that because of the combo of cheap panels (these days) and relatively limited installation options in terms of space/shading/angle-to-sun.

So 400 watts (or more) sounds great. Battery size is not so much of a factor. If you only have solar (but you don't) then you need to be able to put back any power you take out (so a big battery bank can tide you over in bad sun conditions, but you still have to put the power back eventually. But you have a generator and probably alternator to pick up any slack.

You won't overcharge with too many panels, and you won't "die" with too few (since you have alternative power input).

So I'd concentrate on how many panels you can fit while keeping the shading down to a dull roar. Panels get childishly peevish when shaded. Some setups now are using multiple smaller controllers vs. one larger one to keep the winner (sunny) panels from being tainted by the losers (shady). I can only fit 200 watts and have just one good controller.

Also concentrate on good sized wiring to keep voltage drop to a bare minimum. Otherwise you have both a trickle of water (solar) AND a leaky hose (wire with voltage drop).

If you use an MPPT controller you can adjust it so that it will efficiently take in one voltage and output another. That may give you better panel options depending on your space. Series connections may or may not be advantageous (but not to get too complicated I'll leave that out for now).

Once you get it set up and all tweaked, it's wonderful, silent power.

 

[Skeeter]

Split system

Thanks Frosty, would it be of benefit to split the system so that 2 panels are controlled by an MPPT on one battery (Port) and the other 2 panels are controlled by a second MPPT on the second battery (Stbd)?

 

[boathealer]

Thanks Frosty, would it be of benefit to split the system so that 2 panels are controlled by an MPPT on one battery (Port) and the other 2 panels are controlled by a second MPPT on the second battery (Stbd)?

Yes. There are two advantages to this. The incremental cost of another controller and some wiring is minor compared to the panels themselves and the advantages below.

One is shading protection - if one set of panels is shaded or partially shaded, the reduction in power can be considerable, even for a large array. Separate controllers will allow full power output from the other set.

The second is redundancy - if one controller goes down, you still at least have one set continuing to contribute to your batteries.

On our boat, we have four sets of panels/controllers. Your can see the arrangement on the overhead photo. This allows some protection for shading from the dinghy, carried up on top, across various sun angles....

All controllers feed a single battery bank, BTW

 

[Frosty]

Hmm, thinking about that.

On the panel side, I'd say one controller is fine if both panels see similar sun. Supposedly one can "drag the other down" if you have say, one controller on two panels one of which is in full sun while the other is in shade. So it depends on how different (or not) the insolation is on one panel vs. the other(s).

On the battery side.... I only have one house bank so never considered this. My first reaction is to keep it all on one bank because it's simpler and you can combine. If you run one on one day and one on the other you could say sure, one for each bank. But then in a way that wastes the output of whichever panel is on the "non house" bank each day as the start bank (i.e. the fallow house bank) is probably pretty much always fully charged. So you are wasting half your panelage unless you combine, and then you have no safety start bank. But you do have your gen start batt for that, so I guess there are options.

You could consider an ACR or similar between the two main house (start) banks. Basically it is a relay that will combine banks whenever one is charging (voltage over 13.6 or so) and separate them when one is using and none are charging (voltage under 12.6 or so). You can keep your manual switch also.

Frosty

PS: This is slightly different but I did some controlled experiments with two panels in series (i.e. makes one big higher voltage panel). Advantage is fewer and thinner wires, and higher voltage early and late in the day (may help). Disadvantage is they are tied together if one is shaded.

I found that high/thin shading (I used some branches and twigs near the panel and also a blob of tree way up in the sky) didn't change it much. At worst it took away the value of the shaded panel. BUT, blocking off even one cell (I used a small piece of cardboard) pretty much killed both. I would think this could be extrapolated somewhat to multiple parallel panels with individual controllers but have not done that experiment.

 

[kchace]

The only real power draws I have are the Fridge/ freezer (200W 115AC) which I power using a 1500W invertor (wired to stbd house battery), F/W pump, Sump pump, occasional TV/ laptop, and charging for phones, cordless power tools, etc. I know there are all kinds of calculators out there but wondered if anyone has experience of a similar setup and can offer any good advice.

I have a somewhat similar setup and you can expect to use approximately 100ah per day. Though I question the 200w of your fridge. Is that what it says on the data plate? If so, that should be the maximum. Hopefully the average is a lot lower than that.

BTW - FWIW I totally agree with splitting the solar setup as Boathealer suggests.

Ken

 

[Frosty]

Boathealer,

Can you comment on how your multiple controllers "play" together*? I haven't tried it myself, but a friend wasn't entirely sure his two were doing so entirely effectively. As in, one would "back off" and defer to the other.

(Although for example Morningstar says they should play ok if set to same parameters.)

Since his panels were flat and no shading he switched to one bigger controller (had one Victron 75/15 and one 100/30, IIRC and went to one 100/50).

I'm not sure I completely trust his data so wondering what you have observed?

*Side note: Some controllers such as Blue Sky have a way to make multiple controllers combine "as one" once they are in the control stage. I read that Victron was working on a version of this; not sure how that has progressed.

Thanks

 

[sbman]

I recently installed dual Victron SmartSolar controllers on a friends boat. They use wireless to talk to each other and it is stated that they work together just fine, and as observed they did seem to work just fine. This is setup with two panel banks each with their own SmartSolar controller and both connected to the same battery bank.

Boathealer,

Can you comment on how your multiple controllers "play" together*? I haven't tried it myself, but a friend wasn't entirely sure his two were doing so entirely effectively. As in, one would "back off" and defer to the other.

(Although for example Morningstar says they should play ok if set to same parameters.)

Since his panels were flat and no shading he switched to one bigger controller (had one Victron 75/15 and one 100/30, IIRC and went to one 100/50).

I'm not sure I completely trust his data so wondering what you have observed?

*Side note: Some controllers such as Blue Sky have a way to make multiple controllers combine "as one" once they are in the control stage. I read that Victron was working on a version of this; not sure how that has progressed.

Thanks

 

[boathealer]

Boathealer,

Can you comment on how your multiple controllers "play" together*? I haven't tried it myself, but a friend wasn't entirely sure his two were doing so entirely effectively. As in, one would "back off" and defer to the other.

(Although for example Morningstar says they should play ok if set to same parameters.)

Since his panels were flat and no shading he switched to one bigger controller (had one Victron 75/15 and one 100/30, IIRC and went to one 100/50).

I'm not sure I completely trust his data so wondering what you have observed?

*Side note: Some controllers such as Blue Sky have a way to make multiple controllers combine "as one" once they are in the control stage. I read that Victron was working on a version of this; not sure how that has progressed.

Thanks

Hi Frosty,


The previous owner did the install on our boat. All four controllers are set with the same battery parameter profile. They all play happily together, all tied to the same single point on the house bank.

They are all "deciding" on what to do based on the same battery feed point, so they are all seeing the same instantaneous voltage levels, etc.

They each will go into and out of float a every-so-slightly different times due to minute differences in wiring resistance, etc. If one provides the amount of power needed to push the bank into float, they all see that voltage and change over themselves. .....but at that point the differences in voltages is so small that only the theoreticists (?!) would argue that it matters a whole lot. There are so many other variables like sun angle and shading on each bank, it really is a waste of time to try to analyze it.

Below is an example snapshot of the history for all four controllers courtesy of the Bluetooth interface. We have been connected to shore power for the last month, so there is not much contribution from the solar , but you can see the different float voltage times, etc. for each.

Best Regards,
Ray

 

[Skeeter]

Thanks for all the great information, I’m digesting it as I’m not great on electrical systems, Steve

 

[mvweebles]

On average, mounted flat without shading, each 100w of solar panel will produce 30AH of power each day on average - closer to 40AH in summer, closer to 20AH in winter.

Setting up a series of panels is an exercise in Ohms Law (Power (in watts) = Amps x Volts). Or Amps = Watts/Volts. Each set of combined panels is called a "String." Why not just combine all panels together into a single String? For two reasons: First, the voltage and/or the amperage can get pretty high - Ohms Law tells us that panels in series double the voltage and panels in parallel double the amperage (if you've ever used 6V golf cart batteries in a 12V system, you've used the same principle). By creating "Strings," you can more easily adjust the combination of Amps and Voltage to a level that matches the design spec of a Controller.

Second, strings help compensate for differences in solar exposure (e.g. shading of some panels). Turns out that if a panel experiences shading, it has an out-sized effect on the entire string. If you have shading concerns, isolating them into a separate String will help minimize loss due to shading.

Yes, you could just use a separate MPPT Controller for each string (or panel). In residential applications, the same concept is accomplished using what are called micro-inverters - a small module mounted on the back of each panel versus all let to a central big inverter. A previous post has a picture of a super nice install of four MPPT Controllers, however I personally prefer the single controller even though many folks have told me there is a small efficiency penalty. For redundancy, I'd rather carry a spare. I'm just not a fan of networking on boats, especially wireless networking. It's not that I'm a tech-Luddite, much the opposite: I've worked on the business side of funding network upgrades for over 20-years. Networks have occasional stability issues and are prone to obsolescence and inter-operability issues. As long as nothing ever, ever changes, and nothing ever, ever breaks, there is no problem, But eventually, something gets added or upgraded and things go wonky. But it's a personal decision - what's right for me may not be right for others.

I hope the attached diagram helps - it shows flow of Amps/Voltages in a series/parallel configuration right into the String Converter (switches at the bottom row). Each panel is rated at 200W and 14V, so around 14A each.