Multipule Power Sources

[Don Squier]

A charge controller maintains the battery's charge when supplied by solar cells.  What complications are introduced when an alternate power source, such as an alternator's rectified output, is added to the charging system?  Is this output simply connected in parallel with the solar cells, should the charge controller have provisions for an alternate power source or is some other arrangement required?

[Robert Sheridan]

You can get smart controllers that handle multiple sources of power.  I am not an electrics wiz but from what I have gleaned the key thing is to check the amount of current the regulator can take.

We have a wind generator as a secondary power source but it does not produce a lot of amps so I wired it in to the same controller inputs as the solar panel.  If you wired a alternator in in the same way the output from the alternator may be more than a regulator designed for a solar panel can handle.

I am assuming that if you you had 2 simple regulators, one for each power source, that they would work in the same way as a combined regulator in terms of stopping the battery getting overcharged; however, I believe that the newer regulators have a battery conditioning capability (MPPT?) which may cause problems if multiple regulators are attached to a single battery.

[Rusty Gesner]

There was recently a lot of discussion of this topic in the Yahoo Groups Leopard Forum, including detailed how-to information.

 - Rusty

[Dave Vinnicombe]

Hi Don

I am not electrically competent so for my system of 2 banks (2 pairs of 80 watt panels), of solar panels and a standby Honda generator I have separate circuits of each. This means that if a regulator fails on one, it doesnt affect the others. As I understand it (and this is how it has worked in practise over the last 10 years), if I activate both banks of solar panels at the same time, each regulator is independently reading the batteries capacity and admitting as much amperage as the batteries need and can take.

If I need to top up the batteries because the panels have not been sufficient, I switch the panels off and only use the generator's circuit until the shortfall has been made up, then cut the generator and switch back to the solar panels. On our sail to NZ for that year I think I used the generator twice. Usually when we had caught a lot of fish and had to cool down our second fridge!

Dave

[Don Squier]

Rusty Gesner said:

There was recently a lot of discussion of this topic in the Yahoo Groups Leopard Forum, including detailed how-to information.

 - Rusty

Thanks for the source Rusty.  I'm awaiting permission to view the Yahoo Group's postings to research this matter.

Don

[Don Squier]

Dave Vinnicombe said:

Hi Don

I am not electrically competent so for my system of 2 banks (2 pairs of 80 watt panels), of solar panels and a standby Honda generator I have separate circuits of each. This means that if a regulator fails on one, it doesnt affect the others. As I understand it (and this is how it has worked in practise over the last 10 years), if I activate both banks of solar panels at the same time, each regulator is independently reading the batteries capacity and admitting as much amperage as the batteries need and can take.

If I need to top up the batteries because the panels have not been sufficient, I switch the panels off and only use the generator's circuit until the shortfall has been made up, then cut the generator and switch back to the solar panels. On our sail to NZ for that year I think I used the generator twice. Usually when we had caught a lot of fish and had to cool down our second fridge!

Dave

Dave,

Apparently it is necessary to isolate the various power sources to the battery regulator(?).  I had wondered if there might be issues with generator current exceeding the capacity of diodes in some solar panels or with solar current flowing through the generator windings.  I have more to learn in order to assemble a human proof and reliable power system.

Thanks Don  

[Budget Boater]

Each power source should have independent charge controllers, and each should have its own source power wires that are connected to the batteries or battery switch independently. Modern charge controllers already have the necessary means to isolate themselves from other charging sources/back flow.

Can it be done differently? Yes, but why? On a cruising boat, redundancy is key. Don't allow your entire system to rely upon a single controller, because when it goes out (and it will go out) your entire charging system will be down until it is replaced.

Further, different charging sources can require different types of controllers. Where it is normal to use a PWM controller for solar panels, some wind generators can be destroyed by PWM controllers. Just make it easy on yourself and have a separate charge controller for each charging source, and keep a spare for the most important.

[Don Squier]

Thanks Budget Boater, I'm beginning to feel more confident on how these systems are arranged.

Don