Matching solar panels to batteries to consumption

[thomm225]

Originally Posted by Sauntress

Yes, I have found one but need to email it rather than attach it here.

Thanks. PM sent with email.

I just wanted to see the whole boat. It looks like a fine boat.......well proportioned also.

[TeddyDiver]

Originally Posted by ramblinrod

I actually try to dissuade customers from this. If one battery shorts, the DC system is left inoperative, until the battery is replaced.

Whereas with 2 x 12 Vdc batteries, if one shorts, the DC system can be run on the other (albeit with less charge capacity) until the defective battery is replaced. In my opinion, it always good to replace all batteries at once, but few do, especially if the batteries are "not that old".

Actually in paralled bank one shorted can melt down the whole lot..

[socaldmax]

Originally Posted by ramblinrod

I actually try to dissuade customers from this. If one battery shorts, the DC system is left inoperative, until the battery is replaced.

Whereas with 2 x 12 Vdc batteries, if one shorts, the DC system can be run on the other (albeit with less charge capacity) until the defective battery is replaced. In my opinion, it always good to replace all batteries at once, but few do, especially if the batteries are "not that old".

I've installed probably 200 GC2 batteries (or more), mostly in RVs in sets of 4 or 6. I've only had 1 short out, and it did so almost immediately. While your concern is technically valid, it's a very, very small probability.

I have a Chevy diesel truck that uses 2 large car batteries. Every time one of the batteries shorts out, it discharges the other battery before I'm aware of it, every single time. By the time the average sailor who has to ask for advice like this on a website figures out that he has 1 battery with a shorted cell, he's actually got 2 dead batteries.

At that point, when the solar controller is connected to batteries below 10v, it won't operate or charge them. So you're literally in the same boat: a dead battery bank and no way to charge it even if you isolate the dead battery. Remember, all he's planning on using for a charge source is a 50 watt solar panel.

I can't imagine myself living/sailing like that, but more power to him!

[Littlechay]

Originally Posted by mitiempo

Yes, the acceptance rate does fall off but that doesn't mean that the batteries cannot reach full charge on a sunny day. Makes no sense with diesel charging but does with solar.

No sense thinking there is an 80% limit if the sun cooperates.

It's not a limit!

However; Doesn't matter how much sun there is the batteries will still take charge more slowly at the end of the day. What I am getting at is that the panels can't deliver the same current into the batteries all day - the batteries will accept most current in the morning the panels produce most at midday and then later in the day as the insolation decreases the batteries acceptance also decreases.

[socaldmax]

Originally Posted by Littlechay

It's not a limit!

However; Doesn't matter how much sun there is the batteries will still take charge more slowly at the end of the day. What I am getting at is that the panels can't deliver the same current into the batteries all day - the batteries will accept most current in the morning the panels produce most at midday and then later in the day as the insolation decreases the batteries acceptance also decreases.

That is true, but given that the solar panels produce power as long as the sun is up, after a while, the battery bank is going to eventually be very close to fully charged, as opposed to someone running their diesel engine or generator. Most, if not all people won't be willing to run it all day for the small amount of extra charge they will gain.

What is great about solar is that IMHO, there is no such thing as too much. During the day, in addition to charging the batteries, solar power is powering all other 12v loads, thus the batteries are no longer being drained day and night, they only need to power the overnight loads.

While this doesn't apply to this gentleman, others have installed enough solar panels that they can install and use watermakers, a washer/dryer, more refrigeration, radar, AIS, HF/SSB, ice maker, etc. etc. Safety and comfort are vastly improved with the additional power.

[donradcliffe]

I just went through the led tricolor replacement process. I agree that the mainstream LED tricolors are ridiculously overpriced, and several of them have received poor reviews. I so I went with Marinebeam's replacement tricolor bulb for $35

https://store.marinebeam.com/indexed...nal-series-40/

While it is not a certified light, Marinebeam says "This LED replacement bulb easily satisfies the output and visibility requirement for boats up to 20M (65 feet)'. Based on past experience with Marinebeam, that's good enough for me. It draws 0.25 amps, which will make a huge difference in your power requirements.

Marinebeam was also selling a combined tricolor, photocell operated anchor light, and strobe for $99, which only requires one pair of wires. It may be good, but I'll let someone else try this one first.

[Littlechay]

Originally Posted by socaldmax

That is true, but given that the solar panels produce power as long as the sun is up, after a while, the battery bank is going to eventually be very close to fully charged, as opposed to someone running their diesel engine or generator. Most, if not all people won't be willing to run it all day for the small amount of extra charge they will gain.

What is great about solar is that IMHO, there is no such thing as too much. During the day, in addition to charging the batteries, solar power is powering all other 12v loads, thus the batteries are no longer being drained day and night, they only need to power the overnight loads.

While this doesn't apply to this gentleman, others have installed enough solar panels that they can install and use watermakers, a washer/dryer, more refrigeration, radar, AIS, HF/SSB, ice maker, etc. etc. Safety and comfort are vastly improved with the additional power.

Yea. I love solar; just trying to keep things on the straight... and point out that a, for example, 500W panel will not put 35A into the battery all day just because the sun has come out to play.

You have to go large to really pump the battery during the middle four hours of the day.

[mitiempo]

Originally Posted by Littlechay

Yea. I love solar; just trying to keep things on the straight... and point out that a, for example, 500W panel will not put 35A into the battery all day just because the sun has come out to play.

You have to go large to really pump the battery during the middle four hours of the day.

It all depends on the amps you are down and the amount of solar. In many sunny areas reasonable charging starts early in the morning. With the right number of panels you could be at 80% or so before noon. Yes the batteries will accept less after that but you can still have 6 or more hours of charging. Enough time to reach 100%.

[newhaul]

Side note today with heavy clouds and.rain I still reached my 100 percent charge ( but did just use about 15 ah last night. ) 100 watt monocrysteline panel with pwm controller . Float set to 14.6 4Dd dyno battery.

[ramblinrod]

Originally Posted by socaldmax

I have a Chevy diesel truck that uses 2 large car batteries. Every time one of the batteries shorts out, it discharges the other battery before I'm aware of it, every single time. By the time the average sailor who has to ask for advice like this on a website figures out that he has 1 battery with a shorted cell, he's actually got 2 dead batteries.

At that point, when the solar controller is connected to batteries below 10v, it won't operate or charge them. So you're literally in the same boat: a dead battery bank and no way to charge it even if you isolate the dead battery. Remember, all he's planning on using for a charge source is a 50 watt solar panel.

I can't imagine myself living/sailing like that, but more power to him!

If batteries are monitored properly, one will rarely experience a shorted cell as they would have already replaced the batteries due to reduced capacity.

Unfortunately, some don't monitor capacity closely enough to catch this.

If a cell shorts when one is away from the boat for an extended period, a shorted battery could very well discharge the other and hurt it. (All batteries should be changed together, so it doesn't really matter.)

But when cruising (possibly away from civilization) and relying on batteries, most monitor their batteries closely enough that if a cell shorts, they'll get that battery isolated from the house bank in short order. ;-) In doing so, they now have the remaining capacity of the other battery.

How frequently do batteries short (rarely if one is monitoring properly and changes them before their toast), but unfortunately this does not always happen.

I agree with you final statement.

Calculate daily A-hrs consumed, multiply that value by 4 for battery capacity in A-hrs and for solar array in Watts. This is the minimum. That simple.

e.g. If 100 A-hrs / day consumption, then 400 A-hrs of FLA battery capacity and 400W of solar.

More battery capacity and solar is better, to the limits that additional real estate consumption can be tolerated.

[Sauntress]

Who wrote this?

"We first chose to use flexible solar panels because they were les bulky and could be stored away quickly. The absence of a metal frame means less chance of damaging the boat or ourselves whilst we worked around the panels. Then the late Bernard Moitessier showed us another benefit that doubled their usefulness. He added an extension cord to his panels so he could move them up to the foredeck when he was headed west through the tradewinds in the afternoon. This kept the panels out of the shadow of the mainsail. In the morning they could go aft, again in the full rays of the sun. Because of their flexibility and movability we find that two panels, though rated at 1.1 amps each, provide us with sufficient power to cover all of our relatively low usage".

Answer Lin and Larry Pardey.

[Paul Elliott]

Originally Posted by Sauntress

Who wrote this?

"We first chose to use flexible solar panels because they were les bulky and could be stored away quickly.

[......]

Because of their flexibility and movability we find that two panels, though rated at 1.1 amps each, provide us with sufficient power to cover all of our relatively low usage".

Answer Lin and Larry Pardey.

Note that their flexible panels had *very* low power output. Back in those days, flexible panels were extremely inefficient. This was OK for the Pardeys but most of us would have chosen the higher output rigid panels.

These days, there are flexible (or at least semi-flexible) panels that have output similar to the rigid ones.

[Sauntress]

I was puzzled by the 1.1 thought it might have been a misprint. But it gives you an idea of what is posssible.

[newhaul]

Originally Posted by Sauntress

I was puzzled by the 1.1 thought it might have been a misprint. But it gives you an idea of what is posssible.

The 1.1 was amps which is about 15 watts and with two panels that means about 30 watts of solar . I recomended just a bit more at 50watts due to the lack of diference in cost for the panels.

[Sauntress]

Originally Posted by newhaul

The 1.1 was amps which is about 15 watts and with two panels that means about 30 watts of solar . I recomended just a bit more at 50watts due to the lack of diference in cost for the panels.

That was what I worked out with one of those on line calculators, which as you say is less than your recommended 50. Whilst I am here, the controller which is a component of the setup not only prevents overcharging and leakage back when not charging, but will shut down the lights if the batteries run too low, which could be inconvenient. Is that right and can it be overriden if need be?