Gary King wrote:I'm wondering if the JRA brains trust can answer a question about solar controllers. 

I'm planning on a 12V system, 100W solar panels, 2 x 100Ah batteries and the total lighting load would be around 10A (all LED's) - make it 15A when the laptop is charging. So I figure a 20A controller would be fine.

However, if I add a 500W inverter to the circuit (for intermittent use), which could draw 40+ Amps, it would overwhelm the output of the controller.
Is it such a big deal for the inverter to bypass the controller and wire directly to the battery (with fuse)? Or do I need to pony up for a larger capacity controller?

I think you have got good answers...including size the solar controller to your solar panels, not your loads. But one more note applies to that:

Some solar controllers (Mine is one; a Morningstar SunSaver 15MPPT) have a load output. This is designed to power something that you want to turn off if your batteries get too low. (irrigation pumps, for example) I can't think of any reason to use THAT output aboard a boat.

I picked the model I did for several reasons, one being that it appeared to be less dependent on fans than larger models, although it does let (salty) air flow through the unit passively to cool it.

My whole system is two 140W solar panels (Kyocera), that controller, and a smart battery monitor (Xantrex LinkLITE) which watches the full state of charge of my house bank plus the starting bank voltage.

This sounds pretty similar to the other recommendations you have already got.

The system works well for me, and I actually have more generating capacity than I've needed (so far). While at anchor my batteries got topped up almost every day.

                                                                     Stavanger, Thursday

Peter

I don’t recall which PBO issue, but I think that galvanic isolator was made by soldering together discrete diodes. However, after having pondered Brian’s bridge rectifier, I have come to that he is right, provided that the rectifier bridge is of the 3-phase type. Here you can see how to hook up such a bridge to work as a galvanic isolator. Only diodes 1 – 4 are active and the DC output terminals must me shorted with a link. A rectifier bridge for a 12/24V AC generator would do fine.

Arne

PS: Now, having slept on it, I see that the simple 1-phase rectifier bridge will also work perfectly well as a galvanic isolator on the ground wire. All one has to do is to link the DC output terminals together and then use the two input AC terminals as shown in this diagram. Still, it could be that a 3-phase rectifier with a high-current rating is easier to get at. Any auto-electric shop would have it.

A galvanic isolator is described as a 'simple bridge rectifier' here. Any help?

Peter Manning wrote:Arne, do you know if the use of diodes as described in the PBO article you referred to do the same job as a glavanic isolator. I have fitted a galvanic isolator to the ground wire on the mains cable coming into the boat. To check it is working correctly there are two warning lights, one for AC the other for DC current.

That galvanic isolator is most probably th same thing as the diodes I described. I can't see what else it could be.

Arne

Gary Pick wrote:Gary I don't know about West Oz but 95 watt PVs are selling for around $250 here. Chinese no doubt but still with a 20-25 year warranty. I have an 80 watt PV bolted on.

Well, the advantage of using several smaller panels is that they can be connected in series to get 38V or 50V or more, because I plan to buy one of those super duper MPPT controllers. They get very efficient on higher voltages. Like on a cloudy day, a single panel might deliver just 12V, which makes the controller turn off charging. i.e., no juice to the battery. But if 2 panels in series, they might be delivering 20 or 24V on that marginal day, which the MPPT controller will convert to 14 or 15V and still charge your battery - a little @#%# miracle.