Multiple simulaneous charging sources?

[Pete O Static]

I have a basic question that so far, I have not been able to find the answer to on the forum.

My battery banks are currently being recharged by either an AC charger, or the engine driven alternator. I always disconnect the AC charger before starting the engine and wait until the engine is shutdown before reinstating the AC charger. So there is only one given charging source at any one time.

If I introduce a solar array and controller to the equation, the batteries will be receiving a charge anytime the sun is shining. What should be done, if anything, while the engine is running or the AC charger is in use and the solar array is also charging? Many boats have multiple simultaneous charging sources like wind and solar but do they need to be isolated? Or can you simply add multiple sources to your battery bank and expect them to play well with each other?

[DavidLGCrawford]

Here is my setup.
We have shore power when in a marina that feeds into our inverter/charger.
We have twin engines with 60 amp alternators.
We have 1310 watts of solar.
We have 500 watts wind.
We have a 2kw generator for when we need it.

The solar and wind chargers don't output when the batteries are full.
The engines will not output when the batteries are full.
The generator is off of course if we don't need it.

When we arrive at a marina we connect shore power and the inverter goes into charge mode automatically. We also shut down our engines after a few minutes.

As the batteries top up the wind generator will automatically brake, and the solar charger trickles down to nothing.

Our inverter/charger has a battery temperature sensor, and so does our solar charger and our wind charger. All of these make sure the batteries are not overheating and will reduce charging when the temperatures rise.

If you have a seperate inverter and charger, and not a combined unit like ours, then you switch on the charger once you are on shore power and once your engines are off. You **SHOULDN'T** have to do anything with your wind and solar chargers, but check when you are buying them as your unit may be different.

Our solar charger with 1040 watts is an Outback Power Flexmax 80.
Our wind charger with a Rutland 1200 plus 250 watts of solar is a Marlec unit that came with the Rutland.

[captain58sailin]

I have multiple charging sources, engine alt, 110v when the gen set is running, and the solar array. One thing we have discovered, if I have the 110v charger on at the same time as engine alt, and the batteries come to full charge, something in my system causes it to interfere with my tachometer. So when I go to fire up the main engine, I turn off the breaker to the charger. I no longer plug into shore power, don't need it.

[DavidLGCrawford]

Ps. We sometimes disconnect shore power before starting the engines, sometimes it is after we start the engines. So we are still in charge mode sometimes when the engines are started. The alternators on the engines just top up the start batteries then trickle down to nothing. If the house batteries are low (don't know why they would be, but if...) then once shore power is disconnected the alternators power up again.

Oh, and we have 3 battery banks. There is 9.5KwH in the house bank, and a group 31 on each engine. The engine batteries are only charged by the engines, while the house gets all the other power. If we ever killed a start battery we can boost it from the other banks, but the circuit normally only opens when the engine is running.

[Pete O Static]

Thanks guys. to narrow down the query, lets say that you are motoring on a windless but sunny day. Now you have a situation where the engine is charging both battery banks, or at least the house after the start has been topped up, as well as the solar array charging the same bank. Assuming you have a draw on the house for the fridge, autopilot and various other things, the bank my not be topped up.

So, do the voltage regulator on the alternator and the solar controller get along in this situation or is there a potential for interference? I wouldn't want to damage either.

[smac999]

Charge all at once

[captain58sailin]

I haven't had any problems with interference from the solar array, it is equipped with a charge controller.

[ramblinrod]

Originally Posted by Pete O Static

Thanks guys. to narrow down the query, lets say that you are motoring on a windless but sunny day. Now you have a situation where the engine is charging both battery banks, or at least the house after the start has been topped up, as well as the solar array charging the same bank. Assuming you have a draw on the house for the fridge, autopilot and various other things, the bank my not be topped up.

So, do the voltage regulator on the alternator and the solar controller get along in this situation or is there a potential for interference? I wouldn't want to damage either.

Yes. The battery bank draws from the charge source(s) whatever it can accept, depending on SOC (state of charge). The charge controllers will control their outputs based on what the battery bank is accepting and their charge algorithms. It doesn't matter how many charge controllers are connected. They may have different charge algorithms and settings, so one may shift gears before another, but they will all do their own things regardless of what else is connected.

[sailinglegend]

In my experience there can be a problem with wind and solar interacting.

With both solar panels and a wind generator it is often better to use a single regulator with separate wind and solar inputs. If two different regulators are feeding the same battery bank one can get confused by the other and may switch off too early. This is a particular problem in the initial “Boost” stage of charging where batteries will take all the charge they can get from any controller. Regulators all work in slightly different ways, but in principle they are programmed to reach a maximum voltage for a set time and then drop down to a float voltage. With wind generators there is not a constant source of power to allow the regulator to stabilise itself. Often there is a huge surge in available voltage from wind gusts, and then their charge may drop. The wind controller will then still see the high voltage coming from the solar panel controller so it will switch to float. When the wind rises there may be a built-in delay of maybe an hour before the wind controller attempts to charge again and so the cycle continues. The wind generator could potentially be providing the highest charging capability, but much of the time it has switched itself off so its energy is being wasted.

The simplest KISS principle, which is recommended by several wind generator manufacturers, is not to have a regulator for the wind generator but control it manually with a switch or a safe method of tying back the blades when the batteries are known to be 100% charged. This will rarely be needed when cruising with a large service bank, but a high voltage alarm could be programmed into the battery monitor to warn of overcharging. My alarm has come on once in 10 years as a liveaboard. An unregulated wind generator should not be left running when leaving the boat for an extended period without the risk of overcharging.

[jkindredpdx]

I have a controller between the solar panels and an isolator. controller and diesel engine alternator go to separate input legs of the isolator and one output leg to battery bank.

...get the 12 volt bible...https://www.amazon.com/12-Volt-Bible.../dp/0071392335

[the_alpine]

Send all charge sources to house bank. Automatic Charge Relay from house bank to "reserve" or "start" bank.

[Pete O Static]

Originally Posted by the_alpine

Send all charge sources to house bank. Automatic Charge Relay from house bank to "reserve" or "start" bank.

No, I don't need an automatic charging relay. That simply takes the use of the battery paralleling switch out of the equation.

In an transport category aicraft we have at least four sources of electrical power capable of charging batteries. However, there are logic relays in place which NEVER allow more than one power source at a time to power any given bus.

A boat with a properly installed generator should have the same logic relay in place, inhibiting the engine driven alternator from the battery bank anytime both the engine and generator are running at the same time. One should have priority over the other.

I see all these DIY solar, wind and AC installations and am wondering how are people isolating the sources? I cannot see how a solar charger can determine battery voltage and SOC of a bank ( regardless of house or start ) if for instance, there are possibly two or more other sources trying to determine the same thing and charge accordingly.

[jkindredpdx]

Originally Posted by Pete O Static

...
I see all these DIY solar, wind and AC installations and am wondering how are people isolating the sources? I cannot see how a solar charger can determine battery voltage and SOC of a bank ( regardless of house or start ) if for instance, there are possibly two or more other sources trying to determine the same thing and charge accordingly.

You may know more about this than I do, but I think the Isolator something like Guest Battery Isolator 120a 1 Alternator 2 Batteries - Star Marine Depot keeps your sources separated. The controller between the panels and the isolator prevents the battery from draining or over charge.

[boatbod]

If all the charge sources are independently and properly regulated, it won't matter how many sources are active at any given time since they will "sort it out amongst themselves". In practice this means the source with the highest voltage set point will do most of the work.

Occasionally some bad interactions can happen when regulators have similar set points and start hunting (pulsing) and never manage to settle down.

Best advice I can give is try it and see if it works....

[Steven UK]

It is normal for large machines to have two alternators fitted, nothing special about each both internal regulators and they play well with each other. One will switch off before the other (slightly) when the battery's are charged. The key here is that the system voltage is being held low by the battery until it is charged then each regulated source will switch off when it's preset level is reached. The empty battery will accept current until it fills and resists the current and the line pressure (voltage) will increase, as the pressure (voltage) rises the regulators will shut down the pumps (alternators, solar, wind, nuclear, treadmill...) electric is simpler to explain when thought of as a fluid.

I think that's how it works anyway...