SHTP Electrical Seminar

[BobJ]

You need to do a load chart/budget to estimate it, but solar alone probably won't do it. Take a look at Ragtime!'s energy budget worksheet (linked on the 2008 SH TransPac page) and you'll have an idea what my two 43-watt panels contributed to the overall budget.

Andy got by with solar only in 2006 and I think I could have, but the batteries got pretty low at times. We had even more overcast in the 2008 race.

[Culebra]

For the seminar, or now if anyone is so inspired...

I haven't yet explored installing solar panels for augmenting the battery charging (primary is engine). But if I do tackle this, I would want the solar to also provide an emergency source of electrical power in the event the batteries or engine charging system totally die. Do I need to include a method of isolating the batteries from the solar-powered instruments circuit, on the assumption that (if they are really dead) the batteries could draw too much current? I'm thinking the panels would have limited wattage, and not enough to supply both battery charging and instrument usage at the same time.

Thanks, Paul
Culebra

[BobJ]

I don't have a complete answer to your question Paul, but I recall that Greg Nelsen (Outsider/Starbuck) had a solar panel that was dedicated to his tillerpilot if "all else failed."

Maybe Greg will stop in here and explain how that worked.

[Alchera]

For the seminar, or now if anyone is so inspired...

I haven't yet explored installing solar panels for augmenting the battery charging (primary is engine). But if I do tackle this, I would want the solar to also provide an emergency source of electrical power in the event the batteries or engine charging system totally die. Do I need to include a method of isolating the batteries from the solar-powered instruments circuit, on the assumption that (if they are really dead) the batteries could draw too much current? I'm thinking the panels would have limited wattage, and not enough to supply both battery charging and instrument usage at the same time.

Thanks, Paul
Culebra

Solar panels typically put out 18-20+ volts when not connected to a battery, so controlling the voltage to the instruments without a battery connected to keep the voltage in the proper range would be a big problem I would think. You could get a solar regulator, but how well that would work just running instruments is anyone's guess, and they work on the principle of 'wasting' excess power which could have been used to charge your batteries! Plus your instruments are going to fail everytime the sun goes behind a cloud.

I would keep the panels hooked up to the batteries. If your batteries are truly discharged, isolate the one with the smallests AHs, and hook the panel to that so that it will get some charge in it quicker than having to charge the entire bank.
- Mark

[blighbaum]

My engine (and alternator) croaked the day before the start of the SHTP. I sailed with 2 40-watt Kyocera panels on the pushpit, and two 20-watt Flex Pro flexible panels on the dodger, connected to a 10-amp Morningstar regulator and two 105 amp batteries. As far as I could tell from the battery monitor, the panels generated something even when the weather was overcast, and the batteries were well-charged all the way over. I kept my radio, GPS and AIS on at all times, and my strobe and lights on all night. My lights had LED bulbs, and I used a Monitor windvane (not an autopilot) for steering. One man's experience, for what it's worth; it made me a big believer in solar power.

- Tom Kirschbaum, Feral

[jakmang]

For the seminar, or now if anyone is so inspired...

I haven't yet explored installing solar panels for augmenting the battery charging (primary is engine). But if I do tackle this, I would want the solar to also provide an emergency source of electrical power in the event the batteries or engine charging system totally die. Do I need to include a method of isolating the batteries from the solar-powered instruments circuit, on the assumption that (if they are really dead) the batteries could draw too much current? I'm thinking the panels would have limited wattage, and not enough to supply both battery charging and instrument usage at the same time.

Thanks, Paul
Culebra

I agree with what Mark said. Unless there is a catastrophic short in the system, the batteries should not "compete" with the devices that use power, they should just conduct it. In most cases, you need a solar charge regulator so that you don't overcharge the batteries or put too much voltage into the system. All regulator/panel circuts should have a fuse between the regulator and the rest of the system, so that voltage spikes don't reach the panels or the regulator.

A battery monitor is a really good idea. These can be simple volt meters or fancy monitors that will show you how much is going in and out of the batteries as well as the current state. I have found that this is the only way to truely understand your electrical system. It can show you how much a particular device draws.

You also need to think of the ways the primary system might fail and how to handle these in the simplest manner. I am always nervous about extra circuits/pathways that are not well tested by a lot of use (I'm a software guy).

One thing to watch out for when adding panels to a system is that the panel may raise the voltage of the system slightly, so that the alternator charge regulator will turn off with the engine running. This may mean that you will not be charging via the alternator at a time when you really want to. There are ways to wire the system so it does not happen. A simpler way is to be aware of the possibility, monitor the regulator and voltage and disconnect the panels with the engine running, if need be. Another way would be to run the engine at night.

[brianb]

Hi Paul,

Solar panels, in an open circuit configuration, IE not connected to any load, can develop a lot more than 12 volts. 20 volts is not uncommon. If you were to run your instruments only, say a set of Raymarine instruments, they draw very little current and hence would not load the solar panels enough to pull them down to less than 13 volts. Without a battery in the circuit to absorb the additional current, or a voltage regulator, you run the risk of cooking the instrument set. I notice that some newer instruments are rated for operation from 10 to 30 volts, so they are very tolerant.

A battery that has dropped below 11 volts is very dead. I don't think in a no load situation they would be much lower than 10.5 volts. This means that if your solar charger came on line and the battery was that dead the current upon reasonable sunshine would pull the battery up near 12 volts so you could run the instrument pack easily. Auto pilot current draw could alter all this tremendously as at peak load you could easily consume the total capability of the solar panel when struggling with heavy seas. Of course you would need many hours of sunshine to bring the battery up to charge, or a large solar array.

What I am saying is:

1. You need the battery in teh circuit to help regulate a solar panel output.
2. A dead battery will come up to about 11 volts pretty fast under charge.
3. Your instruments are little load (new chart plotters are pretty high load), your AP is a relative large load. If it is just the instruments, you could run them.
4. To run the AP with dead batteries present you likely have to get them charged up for some time to be able to handle the peak current loads.

Hope this helps some.
Brian

For the seminar, or now if anyone is so inspired...

I haven't yet explored installing solar panels for augmenting the battery charging (primary is engine). But if I do tackle this, I would want the solar to also provide an emergency source of electrical power in the event the batteries or engine charging system totally die. Do I need to include a method of isolating the batteries from the solar-powered instruments circuit, on the assumption that (if they are really dead) the batteries could draw too much current? I'm thinking the panels would have limited wattage, and not enough to supply both battery charging and instrument usage at the same time.

Thanks, Paul
Culebra

[Ergo]

I think Tom's experience is highly relevant and brings up a big consideration for folks who are equipping for their first long passage. He notes that solar panels were adequate for his basic needs BUT he used a wind vane; not an autopilot (AP).

If you are planning on using a robust, below deck AP, you need a robust charging system. An AP is much more forgiving of bad sail trim than a wind vane but the cost is paid in amps. This fact is very apparent in light conditions and on a run with a spinnaker up. When working in those conditions, my AP eats 4+ amps an hour. A wind vane uses 0 amps but the cost is paid in time - time spent learning how to use it and becoming very proficient at sail trim. Again, think light conditions and running down wind.

The critical systems: steering, electrical, communications and the skipper's skill level are closely interrelated. In deciding to go "Green" skippers would be well advised to take a very realistic look at how good they really are at balancing their boats.

Bill Merrick

[Eric Thomas]

On Polar Bear 2008 SHTP I had 130 watts of solar on the pushpit, fixed not gimbaled, I had an additional 65 watt panel in cockpit under the tiller that I would toss and around and prop up to catch sun as possible. I had two 100 ah agm batteries and a morningstar 10 amp regulator. In the overcast skies of the first 10 days I lost 3% of the bank that I could not get back the next day. After ten days I was at 70% then the sun came out and I was fully charged. I ran 5 raymarine ST60 displays, a VHF, LED running light, mac laptop, satphone, S1G GP Pilot and the SSB for all call ins and some chatting. A link battery monitor is really great to have to fully understand your usage and charging ability.

[Lucie Mewes]

Did you sell this stuff? We MIGHT be wanting a balmar...have to check with the guru!
Lucie