Understanding my solar power and batteries

[admiralslater]

Originally Posted by john61ct

actually it's a very common size

I have two

[dbraymer]

If that is your biggest boat problem, my hat is off to you!

1. If it isn't broke, do not fix it.

2. Reduction to absurdity argument: If you were operating on a single motorcycle battery, you would run out of 12 VDC daily. If you were operating on 100 deep cycles, they would never wear out, you could live on your boat until 105 years old.

Somewhere in between is your correct answer on the house battery bank. You need to consider the greatest possible use for the longest voyage you wish to out fit the boat to engage in, and the typical weather (sunlight) that could be expected.

If you just wished to stay at the dock, you would just get a really good 110 cord, unless they are charging way too much for the 110

As to the typical live aboard but sail sometimes situation, it would be best to have enough solar cells to get to the float state regularly, just to show that you had reached full charge.

My advice would be to get on a battery replacement schedule, so that you could keep the big bank of house batteries, but you would not be looking at some kind of a complete collapse when you finally venture forth from the dock. This might be tricky if you are upgrading, different battery types, etc... You might have to run one day on 1/2 the house....the next day the other half.

[john61ct]

Yes to the schedule where reliability is critical, travelling to primitive shores.

But whole House bank replaced at once is best, and rarely should it be split.

And remember just because a charge source goes to Float doesn't mean the bank is Full, that needs to be verified and adjusted until it becomes true, and often tweaked with changing conditions

[tanglewood]

Originally Posted by john61ct

False. In fact SG to be very accurate requires isolated resting time, 24-72 hours.

That's really not right. SG will always correctly reflect the SOC of the battery regardless of charge/discharge current. It won't change with resting time. The only exception I can think of is if you have very poor mixing of the elecrolyte. But if you are charging at a reasonable rate, it will mix up just fine.

[motion30]

Originally Posted by JohnT

Just a quick question to the OP. How many panels do you have and how are they wired? Are they all wired in parallel or do you have them wired in series and parallel? And what is the VOC of each panel?

2 in series with 2 parallel strings. My controller has a maximum of 150 volt input. Two panels in series has a max full of 80v.

[john61ct]

I was unable to find my reference for accurate SG reading requiring some resting period.

But I don't use SG much myself, for SoH check / testing only, not day to day management,

since only endAmps is really accurate for 100% SoC, and the AH counting meter is close enough to avoid going "too low" DoD.

Bottom line is, SG reading cannot be used to show the state of charge.

Other than*completely*flat at 1.0.

A 100% fully charged batt's SG reading will drop lower and lower as SoH declines.

If endAmps 100% is known, that fact can actually help judge SoH, but the curve varies a lot from one model / make to the next.

[john61ct]

Originally Posted by motion30

2 in series with 2 parallel strings. My controller has a maximum of 150 volt input. Two panels in series has a max full of 80v.

With many controllers that would be very risky, unlike watt ratings, actual Volts can spike higher than Voc ratings and fry the SC electronics.

With a 150V rated Victron, I would keep the panels' Voc rating to 130-135V max.