Mixing Technology.

[pads]

Hi people.

 

I've got a boat with a Mastervolt Combi unit fitted. (12/2500-10).
OK, very nice (in a technologically frightening way) with two other boxes in the digtal line i.e. a mastershunt 500 and a thingy called a digital DC 10x 10A.

All I can say about them is the green LED's flash occasionally and it all looks very "butch".

 

It scares the heck out of me does all that technology.

 

Load wise, the only thing running 24/7 is my fridge which pulls 6.3 amps occasionally when the fan is turning. The rest of the boat is now all low power LED.

 

What I want to do is to equip for constant cruising and thus am thinking I've got a nice big roof, and there is enough space for 4 x 100w 12v solar panels running through a MPPT controller.

 

Not a problem except can you combine (parallel) the two?
That's the free solar power and the all singing grey box with the Master Volt label?

 

So far emails to MasterVolt are going unanswered thus this question.
Which either means they don't want me to or I've been spammed into the WPB.

 

And across to you.

 

 

 

[phill]

Yes. Go for larger rated panels (less of them) if you can, you'll get more benefit from the MPPT.

Edited September 13, 2014 by phill

[by'eck]

Yes just connect the output of the pv panel mppt controller to the same points as service bank alternator, Combi etc., particularly with regard to Mastershunt which will be in the negative battery feed. You will then be able to see what current the panels are putting into your batteries after taking account of other loads.

[Arthur Brown]

Solar. Yes you can fit, connect and forget it. As it will by-pass the master switch it needs appropriate fusing and wiring to comply with BSS.

 

Some people find that 250w of solar gives them three months of free electricity, and more cells will extend the period of self sufficiency -a LOT will depend on your style of life and electricity usage. It's hard to be self sufficient in the depths of winter with short dull days.

Don't be too concerned though as you will need to run the engine to move in accordance with CC rules, and maybe to make hot water -according to the rest of your equipment.

 

Monitor you battery charge state frequently until you get used to the new system, then you can keep your batteries charged continuously for free with little monitoring. If the SOC goes down then generating by engine in the early morning (after 0800!) will bulk charge them and leave the solar to do the absorption and float stages. during the day. Remember that batteries need to be fully charged regularly (weekly) or they lose capacity

 

It's a good plan to have a separate means of keeping the starter battery fully charged, and when CCing it's a good plan to have a second source of electricity -either visit a shoreline sometimes of have a generator.

[nicknorman]

Yes as said, no issues with the technology but just make sure you connect the solar to the non-battery side of the Mastershunt so that the solar current will register on it. Out of interest, do you have a Masterview Easycontrol panel or similar? I ask because you need some means to communicate with the Mastershunt so you can see the State of Charge figure.

Edited September 13, 2014 by nicknorman

[smileypete]

A typical medium size install would be based on 400W of solar panels and a 30A Tracer MPPT solar controller from the likes of Bimble solar.

 

The trickest bit may be getting some bracketry to securely mount the panels to the roof, someone called Matty on here might be able to do it if nearby, some build the panels into a kind of top box.

 

If it's mainly for summer use then there's also stick on panels that just stick straight to the roof, the panels work out more expensive but don't need brackets and so are easier to fit.

 

cheers, Pete.

~smpt~

Edited September 13, 2014 by smileypete

[pads]

Thank you all for your replies.
I'm actually glad I can because too much electronics (MasterVolt) scares me.

Yes nicknorman I've got the remote battery meter thingy to monitor the batteries although showing what is going through the shunt seems to be a bit weird as I've never seen it read ZERO!

 

Jacking into the non battery side of the shunt will have to be done by the main alternator fuses I guess so I'm looking for putting a fuse holder onto the main distribution board. Should be easy enough.

30 amp controller was suggested, so I'm guessing that I need something round a 25 amp fuse.

 

I can definitely see the advantage of running the engine as the bulk charge then let the solar do it's thing as the absorption / float supply.

 

Them curvy panels look good and gluing them down to the roof will save a lot of work with boards / bracketry.

Besides it's better security in my mind. Expensive suckers though aren't they?

I sketched a friends DIY angle iron job which enabled her to angle the flat panels she has fitted yet although "elegant" as it was, the roof is curved so I'm thinking why not use the flexible ones.

 

How essential is it to point the boards though? After all the roof is curved a bit.

 

One thing though. Sun shines, roof gets hot and it creaks well. Toasty as the wife calls it.
I'm thinking the roof will flex, stretch, shrink, or whatever, that won't damage those stick on types will it?

Looking at the adverts, I've actually got room for 6 x 100 watt panels.

It seemed a lot yet I was reading that in winter you can lose up to 75% charge from some makes of panels.
On the other side, in summer, if I had an array like that, would I need to black out say half the panels to prevent over driving the MPPT box?

 

Then, If I did that, would I be endangering the blacked out panels from reverse charging (I suppose you'd call it that).

 

So many questions, so little time but as said, thanks for all your answers.

[phill]

Italics in order;

 

50A

Yes

Impossible with flexible ones

(30A controller @ 12V = 500W)

No. It will reduce the output a bit though.

No. Match the array to the controller.

No (irrelevant)

[smileypete]

Any decent MPPT should 'self limit' OK with oversize arrays, the classic Tracers do, as do the Midnights.

 

What is important is the solar array voltage must not exceed the controller max input voltage under any conditions. So realistically the max solar array voltage (Voc) should be less than 85% of the controller max input voltage.

 

cheers, Pete.

~smpt~

Edited September 14, 2014 by smileypete

[pads]

I thank you both.

 

Voc? Come to think about it I've not seen that included in many adverts but understand what it means now.

 

I'm thinking of using 24 volt panels in parallel 'cause I need more voltage then 12 volts when using an MPPT charger and that produces more current (Or so it is written).

Then I made a mistake and looked up what it was all about on the http://pveducation.org site.

 

Anyone else scratching their heads at that one like I did?

Thus I feel a series of phone calls coming on to a few suppliers to find out the VOC.
The Keep it stupidly simple (KISS) non mathematical approach .

 

[phill]

VOC is generally a given in any specs - the most important one - the two choices are ( very broadly) 22v ish for 12v systems with PWM doubled for 24v and 36-40v ish used with large arrays and MPPT controllers .

[oarfish]

After putting solar through our mastervolt via a tracer MPPT the amp counter seems to be even more inaccurate than usual. I assume this is something to do with the sampling rate being too low for the noisy solar. Other than that it all seems to work fine.

[smileypete]

Voc = solar panel open circuit voltage, ie it's voltage when no current is being drawn.

 

With MPPT, as long as the total Voc for the array of panels is above batt voltage and below 85% of the controllers max input voltage, you're good to go.

 

Can make things easier if running a set of identical panels into a single controller.

 

cheers, Pete.

~smpt~

Edited September 16, 2014 by smileypete