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post #1 of Old 08-15-2013 Thread Starter
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yet another battery charging question

Sorry this is one of those things that comes up again and again. I have read many threads on this forum about this topic, and think I now have a fairly clear idea about how to proceed, so this is really a request that someone more expert about these matters than I am can confirm that I'm right - or not!

Also, apologies that this is rather a long post, but I want to be as accurate as possible.

I'm on a swinging mooring, so no mains power. The boat is located in Cornwall, England, so weather not bad by UK standards, but sunshine levels not up to those in places like Florida either. There is also the problem that energy needs tend to be greater in winter when the days are shortest. The boat is an old (1930s) gaffer and this restricts my options because the boom overhangs the stern, making almost all wind generator options impossible. The only thing I can think of that would work would be a vertical axis generator mounted on the mast, but there is no way I could afford that at present. My energy needs are quite modest as I do not have any big power consumers like a fridge, powered anchor winch, etc. Main uses are lighting, some entertainment, and instruments when sailing, and as far as possible all are low energy.

My current setup is:

- I have a single cranking battery - a straightforward car battery of about 70AH, which is about 2 years old and works fine. I have 2 brand new 110AH lead acid leisure batteries (these replace the defunct single 110AH battery that died, so I have doubled capacity there). I have a single 25W solar panel with a built-in PWM controller, and a new 70A alternator with internal regulator. That doesn't sound a lot, but the solar panel has not done a bad job of keeping things going over the last couple of years with relatively little use of the engine.

- the alternator (fitted last year as part of new engine installation) is connected to the cranking battery; the solar panel is connected to the house batteries. The house batteries are wired together in parallel and the bank has an isolation switch. The cranking battery also has an isolator. There is a manual combiner switch, and a paralleling relay. Overall, probably a pretty common basic setup.

Reading the forums, and Calder, I have concluded that not only do I not have enough charging capacity (well, I already knew that much), but what I do have is probably not being used very efficiently. What I propose to do is this:

- wire the alternator to the house bank instead of the cranking battery and replace the the current paralleling relay with a Xantrex echo charger to keep the crank battery topped up

- add a new solar panel; the largest I can fit would be a 90W on the coach roof which would obviously suffer from shading but is about the best I can manage given the constraints of the boat

- use a MPPT charger with this new panel to maximise its charging capability.

This would be about the most that I could afford right now. Longer term, I would be considering replacing the standard alternator controller with a smart controller, and maybe doing the same for the existing 25W solar panel.

My main question is, then: does this seem about right?

The other thing is that, although I really cannot afford to spend more than this, it does occur to me that overall this means having 3 charge regulators plus the echo device, and that seems rather a lot of components all doing the same basic job. Is it possible to have a single controller that could take the inputs of all the different charging sources and provide both the smart output for the house bank and the top-up output for the crank battery, or is it simpler (essential?) to have a controller per charging device.

Many thanks!
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