Should I have a selector switch between charge sources?

[CapPugwash]

Hello boaty-peeps.

Currently rewiring my boat and have got to the charger connections. I currently have a battery charger and solar charge controller but may add back in the wind generator i took off. So my question is, should I have a selector switch to select the charge source? Or is it acceptable to have them all wired in together as it was?

Cheers.

 

[Graham376]

Mine were all wired together and never any problems.

 

[VicS]

Hello boaty-peeps.

Currently rewiring my boat and have got to the charger connections. I currently have a battery charger and solar charge controller but may add back in the wind generator i took off. So my question is, should I have a selector switch to select the charge source? Or is it acceptable to have them all wired in together as it was?

Cheers.

Acceptable and normal provided the battery charger is one designed / suitable for permanent connection. A portable / bench / workshop charger intended to be connected with crocodile clips when needed may have a small but significant drain from the battery when not in use if permanently wired in. Easy enough to check.

 

[noelex]

It is generally fine to leave multiple charging inputs connected, but some devices benefit from an on/off switch to eliminate the parasitic draw from the batteries when there is no input for long periods (such as a battery charger when away from shore power, or a wind generator that has been tied up). This is also an aid to service/troubleshooting.

An alternative to the switch is to mount the fuse so that it can be easily removed, or combine the two functions with a circuit breaker.

 

[SimonKNZ]

I've sometimes wondered whether the voltage from one charging source will affect the current supplied from another. Eg, if my solar controller is charging at 14.4 volts and say 4 amps (not the actual figures but go with me) and the alternator charger sees this as a fully-charged battery, will the latter reduce its charging current? So the battery gets charged at a lower rate than the engine could provide?
I could be overthinking it!

 

[noelex]

In your example if 14.4v is the correct absorption battery voltage (as set on the alternator and the solar controller), then the battery will be happy and will not accept more than 4A (using your example), otherwise the battery voltage would climb too high.

If the engine is started, the total current will not rise higher, but it may be that the 4A will be supplied by the alternator or just the solar or a combination of both.

It is not that the regulators see the battery as full, rather they are programmed to limit the voltage to 14.4v to charge the battery optimally.

If the correct absorption voltage is higher say 14.6V when the engine is started the voltage will rise to 14.6v (providing the alternator and solar can provide enough current). Say this takes 15A. The solar might provide 4A and the alternator 11A, or the alternator might provide the 15A and the solar zero or some other combination that produces 15A. The battery does not care where the current is coming from.

 

[Supertramp]

As an aside, I have added isolation switches downstream of my battery charger so I can select whether to charge house batteries or engine battery from shore power. Previously my engine battery charged with the house batteries when on shore power which given the different ages and capacities never felt right. But in reality it never needs that sort of charging except during the winter.

As post #4, I like the idea of simple isolation switches to take items in and out of service, aid troubleshooting and keep control of what bits are live. Might be influenced by location and space.

 

[Graham_Wright]

I have a Sterling charger with three outputs. I have often wondered how it determines which of the three batters need the charge. As far as I can establish, the three outputs are just commoned.

 

[Poecheng]

I have a Sterling charger with three outputs. I have often wondered how it determines which of the three batters need the charge. As far as I can establish, the three outputs are just commoned.

I think the answer is that 'it' doesn't work it out, the batteries determine the outcome.

 

[PaulRainbow]

Hello boaty-peeps.

Currently rewiring my boat and have got to the charger connections. I currently have a battery charger and solar charge controller but may add back in the wind generator i took off. So my question is, should I have a selector switch to select the charge source? Or is it acceptable to have them all wired in together as it was?

Cheers.

Leave them all together.