Solar panel or additional battery capacity - best value for money?

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Ammonite

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I'm planning a West Country cruise this summer and I'm worried that I don't have enough battery capacity particularly as we're hoping to steer clear of marina's (hence power) and make the most of any visitors buoys / anchoring as we can. I can't really afford an additional battery as well as a solar panel and I'm trying to figure out which is the best value (I've discounted wind generators due to the cost for the moment).

My current setup comprises a 20A mains charger, 60Ah starter and 102Ah domestic. We have a fridge (which we rarely use), pumped freshwater, a small autopilot and an 10" flat screen August TV/DVD (CBeebies is a must for any trip with a 3 year old) but that's about it other than lighting. We plan to sail every other day on average with 1 - 2 nights a week in a marina with power. I anticipate using the engine about 1 -2 hours per day on the days that we sail, so around 4 - 6 hours per week. Engine is a 20hp Beta with standard alternator

I know there are precise formulas for working these things out but would be interested in peoples experiences of what works for them - particularly as it's difficult to estimate how much power a solar panel will generate in the UK.
 
Your TV is quite a big consumer. I have one in my motorhome, and a domestic battery the same size as yours. From fully charged the TV will flatten the battery in about 2 hours.

A solar panel to cope with the TV usage in UK will need to be big and probably cost at least £300. Don't think that a small one, i.e. less than 40 watts, will give you anything worthwhile for this type of use.

My advice would be to increase the size of your battery bank. Your engine, with an alternator controller, will charge both in an hour or less and the two will run your TV until your 3-year old nods off!
 
Extra battery capacity will only be useful if you have the means to charge it, the best option probably being mains, which you are ruling out.
My guess, given your scenario, is that the domestic battery will get progressively run down. A solar panel will need to be fairly large, and pricey/inconvenient to give useful contribution on a day by day basis.
If you want to maximise the aH's from your engine running time, I'd suggest fitting an alternator boost regulator, costing ~£110 plus fitting.
 
chaktoura said:
My current setup comprises a 20A mains charger, 60Ah starter and 102Ah domestic. <snip>We plan to sail every other day on average with 1 - 2 nights a week in a marina with power. I anticipate using the engine about 1 -2 hours per day on the days that we sail, so around 4 - 6 hours per week. </snip>
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We have 2 140Ah domestic batteries and struggle to keep them charged with a 30w solar panel - granted the batteries are on their last legs, but we are pretty careful with elec and have some LEDs for lighting and don't bother with TV - we do run a fridge though - but normally on low power when the engine is off and it is turned off at night (don't like the noise!). Our panel is mainly to keep the batteries topped up whilst she is on the mooring (no shore power on a swinger!)
I can see the dilemma you're in - you could really do with an additional battery AND a solar panel...

You can get 110Ah leisure batteries for ~ £70 and one of those would probably be my first suggestion. 20 or 30w semi flexible solar panels are ~£200 - one of these would be ideal to slow down the drain - but TBH, it is cheaper just to run the engine for an hour or so ...
 
Thanks Vyv - I take it you have an industrial spec TV! :-) Ours is only rated at 22W, which according to Google is 2amps with a constant 12 v voltage (no idea if that's the right calculation btw).

Assuming I go down the alternator controller route any idea how easy / expensive are they to fit and is it a DIY job? I've recently wired in a NASA BM1 and a GPS to VHF but that's about the extent of my abilities. Thanks
 
chaktoura said:
Assuming I go down the alternator controller route any idea how easy / expensive are they to fit and is it a DIY job? I've recently wired in a NASA BM1 and a GPS to VHF but that's about the extent of my abilities. Thanks
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The trickiest bit is modifying the alternator, though an auto-electrician can do that if you want, or even the regulator supplier AFAIK. Sterling do one for unmodified alternators but its more expensive.
The rest is fairly straightforward wiring.
 
chaktoura said:
Thanks Vyv - I take it you have an industrial spec TV! :-) Ours is only rated at 22W, which according to Google is 2amps with a constant 12 v voltage (no idea if that's the right calculation btw).

Assuming I go down the alternator controller route any idea how easy / expensive are they to fit and is it a DIY job? I've recently wired in a NASA BM1 and a GPS to VHF but that's about the extent of my abilities. Thanks
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Ours is the 12" MEOS, rated at 25 watts.

Adding a Sterling controller is definitely DIY but you need a bit more than basic skills. Can you find someone to give you a hand?
 
If you are happy with the present arrangement and you are only doing this to sort out a problem whilst you are holiday then Fireball is right; just use the engine a little more!

IMHO there is no point in getting more batteries unless you have the ability to keep them properly charged. In the long run they'll only deteriorate.

The standard Beta alternator is not very large so it may be worth fixing a larger alternator. However, I'm not sure which is better; small alternator with a controller or bigger alternator with no controller. A bigger alternator is probably the easiest solution in terms of ease of installation. Others may have a view
 
Adding a Sterling controller is definitely DIY but you need a bit more than basic skills. Can you find someone to give you a hand?
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One of Sterling's "Alternator to Battery" chargers may be a route to better battery charging.
A truly add-on device requiring no modification of the alternator but giving enhanced charging of the domestic battery and bog-standard charging of the starter battery.
 
If you want to get your alternator modified to fit a Stirling controller, the best way is to take the alternator off the boat (easy job) and get the extra connections put in by an auto electrician at his works. That way you will not pay for a visit to your boat. Once the alternator is modified the installation is straightforward.
 
to answer your question, i would say that adding more capacity is the "better value" option, that will of course require more engine hours to charge it up, but you can buy a lot of hours of running for the price of a decent solar panel.
 
My suggestion is not to compromise. We tried all sorts of half hearted bodges and were never happy with the outcome.

Get 2 110Ah batteries for about £150,

Get a diode splitter [£60??] to manage the charge from the alternator to the 3 separate banks.

Bank 1 your 2 new batteries to drive all the necessary on the boat
Bank 2 your engine starter battery
Bank 3 the existing battery to drive the TV

Use the largest size cable you can afford!
Have them wired separately - that way the TV will never kill your starter etc.
Have a jump lead, just in case the unexpected does happen and you need to 'hot wire' things to get going.

Treat yourself to a Sterling unit next season

Expect to run the engine a little bit longer when you are moving the boat.
For the £400 for decent solar panel you can buy this lot and still a few gallons of diesel!

Loads of people will be along to tell you not to use the engine on no load for any length of time.
 
I reckon fit an extra domestic battery, make sure it is impossible to flatten your engine battery, with a switch or seperate wiring. Alternator regulator would be excellent addition no matter what. The other posters are correct, best way to get the alternator modified, take it to an auto electrician. Then easy peasy.
From your scenario, you are not going to be short of power, running your engine 1-2 hours a day (probably more if I know the vagaries of UK weather) and in a marina 1-2 nights a week, again taking into consideration weather. The marina overnights will fully charge your batteries and I reckon you will have no worries. Forget the solar, just not going to be viable. IMHO
 
Thanks for the tips guys. I'm pretty sure I'm going to go for a Sterling AR12V Alternator Regulator (cheapest I've found so far is £85 inc VAT) and add another battery to the domestic bank. Having read the manual on the Sterling site I think I under estimated my abilities - remove the alternator, solder a couple of wires and follow a manual full of typos - you'd think someone would proof read these wouldn't you :-) Joking aside it looks pretty straight forward.
 
chaktoura said:
Thanks for the tips guys. I'm pretty sure I'm going to go for a Sterling AR12V Alternator Regulator (cheapest I've found so far is £85 inc VAT) and add another battery to the domestic bank. Having read the manual on the Sterling site I think I under estimated my abilities - remove the alternator, solder a couple of wires and follow a manual full of typos - you'd think someone would proof read these wouldn't you :-) Joking aside it looks pretty straight forward.
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Good decision! £85 is about the cheapest you'll probably find (JGTech, etc). As for the manuals, Mr Sterling is big on words, small on accuracy!
 
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