Solar Panel

[Shoalwaters]

I am seriously considering installing a solar panel to keep my batteries charged when shore power is not available.

My boat has twin engines each with two start and two house batteries.
All four batteries charge via a ProMariner smart charger or the engine alternators (with Newmar battery isolators).
How (in general terms) would the solar panel be connected so that one system does not conflict with another?

 

[Per]

the panels should be installed with a special solar charge controller.
this controller will apply the current from the panels, so if another source is charging then it would probably only trickle charge.
this controller will also protect the panels so that a charge from the alternator or from the charger will not go into the panels.

what i generally do is to shut off the shorepower and just let the panels keep the batts topped off (also runs the fridge).

 

[Larry M]

Per wrote:
i used two panels of each 85W and a sunsaver MPPT CC.

this weekend i did some experimenting and unplugged the shoreline.
solar did fine, ran the fridge and radio etc. i used also the waterheater but that really takes some amps out of the battery banks.
according to the meter the solar supplied between 65 and 70 AH per day to the battery bank.
i am very happy with those numbers...

*Per:* Be Careful with the hot water heater.* I'm surprised that you can heat hot water through your inverter.* You can inadvertently drain/hurt your batteries.

 

[Per]

Larry, true enough..
I have learned to use the waterheater sparingly.. when not on shore power or running the genny.
same goes for the electric stove and the icemaker..

 

[Bendit]

Our two 80W panels run our 24V freezer year round and keep the batteries fully charged. In summer, they will run the two 24V fridges as well. It's*definitely like getting something for nothing. Controller is a German Steca.

Hardly ever use the genset in summer - only for the vacuum cleaner every few days, but we don't run the inverter for hot water. The 75 litre tank*stays hot for about 24* hours if used sparingly.

 

[Shoalwaters]

Per wrote:
the panels should be installed with a special solar charge controller.
this controller will apply the current from the panels, so if another source is charging then it would probably only trickle charge.
this controller will also protect the panels so that a charge from the alternator or from the charger will not go into the panels.

what i generally do is to shut off the shorepower and just let the panels keep the batts topped off (also runs the fridge).

*Per,

Thanks for the outline.

An HQRP charge controller / regulator is included in the Amazon advert you reference.

1. What made you choose the Sunsaver one over HQRP?

2. I assume the charge controllers have separate outlets for each battery. How many batteries can yours handle?

BTW: I Googled without success for a downloadable manual and/or circuit diagram which would have answered most of my questions.

 

[Per]

I decided that I wanted to add a second panel and for that purpose the basic HQRP controller just doesnt do the job.

Once I decided on a second panel (and perhaps another to be added later), I started researching controllers.

MPPT is a technology which extracts the most optimal volt/amp point on the power curve and convert that into charging current on a 3 stage level (similar to a/c smart chargers).

It turns out that to get effective charging current, it is better to have incoming volt well above the charging level.

Therefore it is recommended to wire the panels in serial, this will produce a solar voltage of apprx 17 PV x 2 = 34 photovolts (based on 2 panels with a nominal voltage of 12 volt).

Regarding you question related to hown many batteries.. Most boat batteries are connected in a "bank" so you need not worry about connecting the controller to every battery, just one connection to the bank, and you could not connect it to two banks though the sunsaver mppt does have another load output where you could charge perhaps a smaller battery or run a small load.

here is the link to the sunsaver mppt including technical data:

http://www.morningstarcorp.com/en/sunsavermppt

 

[FF]

"Our two 80W panels run our 24V freezer year round and keep the batteries fully charged. In summer, they will run the two 24V fridges as well."

3 fridges on 160W total !!!

Almost a miracle , how large are these?

Usually ONE fridge needs 60A-80A of 12V or 30A - 40A of 24v in 24 hours .

 

[FlyWright]

In speaking with a buddy who has solar on his blowboat, I learned that his 400W system in Mexican waters provides him with a reliable 120A (@12V) per day. I suppose about 100A from a 400W panel would be realistic in the mid-latitudes like CA or NC.

 

[Per]

absolutely, i get up to 80 Amp hours on only 2 x 85 watt.
the MPPT controller makes a difference, and especially if you are located in a cloudy or not always sunny location.

 

[Shoalwaters]

Thanks for the input Per; I think I have enough info to go shopping now.

 

[Singleprop]

MPPT explained

This link describes very well what the MPPT does:

http://www.windsun.com/ChargeControls/MPPT.htm

 

[Singleprop]

I thought I had it all sorted out and emailed my electrician to confirm that it would be best to connect 2 x 24V solar panels in series to the MPPT controller and 24V battery bank (this was discussed earlier on in this thread- and which was my understanding as well).

He replied that parallel connection of the panels would be the correct way - even after questioning him. I must admit that I did not go that deep into the questioning since I neeeded to verify my information - hence this reply.

So what is the best way to do it - parallel or series - with the MPPT controllers?

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