Two power sources, one instrument

[Yellow Ballad]

I'm going to ask a silly question and I think I know the answer but I have a slight doubt.

Can I hook up two 12v power sources (parallel) to my AIS transponder/transceiver (for those that argue which one it is)? What I'm thinking is have it powered as usual through the master switch but also power it through my solar controller load socket. I can program it to power up an hour after sunset so I can check online the boat us still there/not sunk... living 100 miles away.

I would have thought it would be fine being from the same source but then I thought would there be a possibility of voltage spikes(?) of something else if I had the main power on and then the solar controller kicked in, being radio equipment.

It quite possibly a but of a pointless task, the boat hasn't gone for a sail by itself that I know of since I've owned it and if it didn't ping up on one of the AIS websites it would put me in a panic but the question still stands, I'm curious.

 

[pmagowan]

If your solar is powering the batteries then surely this is the power that the instrument will see anyway

 

[johnalison]

My AIS is powered direct from the battery, as is my Webasto. I don't deliberately leave it on when off the boat but often do so inadvertently.

 

[mersey]

Victron battery combining diode, failure of any one of the two sources will not interrupt the supply.

https://www.ebay.co.uk/itm/223054235584

 

[BelleSerene]

Victron battery combining diode, failure of any one of the two sources will not interrupt the supply.

https://www.ebay.co.uk/itm/223054235584

That will work brilliantly. I’m told sledgehammers crack nuts pretty effectively too!

Those power diodes will feed 70 amps, enough to run your starter motor, fridge, radar and everything else combined. The OP is only trying to power his AIS transceiver! A pair of small power diodes will do. Rather than spending £36 on that monstrously over-rated and space-consuming device for the purpose, how’s about using two of the ten diodes in this pack for £1.40 and keeping the other eight? They are each rated at up to 2A, twice as much as your AIS transceiver will draw.

 

[William_H]

As said 2 preferably schotky diodes (lower volt drop) with the cathodes together at the AIS power input and one anode to the "street light" output of the solar controller the other anode to normal supply. Diodes need to be rated much more than the current used by the AIS. No I can't see any problem with power spikes. Something like this would do nicely. Note 2 diodes in one package which are connected as you need them. https://www.ebay.com/itm/2pcs-ESAC8...tke+diodes&_from=R40&rt=nc&_trksid=m570.l1313 ol'will

 

[[70521]]

Can I hook up two 12v power sources (parallel) to my AIS transponder/transceiver (for those that argue which one it is)? What I'm thinking is have it powered as usual through the master switch but also power it through my solar controller load socket. I can program it to power up an hour after sunset so I can check online the boat us still there/not sunk... living 100 miles away.

Why over complicate things?

Look at the power consumption of you AIS it should be tiny.

 

[PaulRainbow]

So, you leave the boat and turn the main isolator off, the AIS goes off. When it gets dark the solar controller turns to load output on and the AIS comes on and you can see where the boat is, that's how i understand the question.

With the isolator off and the load circuit on, there is no need for a diode, where's the power going to go ?

When onboard with the isolator on and the load circuit becomes live, so what, it's just two parallel supplies from the same battery, no need for diodes here either.

No chance of a power spike.

Well done Pete, post #2 :encouragement:

 

[halcyon]

So, you leave the boat and turn the main isolator off, the AIS goes off. When it gets dark the solar controller turns to load output on and the AIS comes on and you can see where the boat is, that's how i understand the question.

With the isolator off and the load circuit on, there is no need for a diode, where's the power going to go ?

When onboard with the isolator on and the load circuit becomes live, so what, it's just two parallel supplies from the same battery, no need for diodes here either.

No chance of a power spike.

Well done Pete, post #2 :encouragement:

Read post #3

We supplied Sealine with a similar setup, powered nav equipment from both battery banks, so no spikes during engine start.

In your case it would draw power from which source had the higher voltage if both powered on, solar if battery off.

Bridge rectifier makes install easier, positive to each AC input, common positive to AIS from the positive out, see ebay https://www.ebay.co.uk/itm/KBPC2502-Bridge-Rectifier-Diode-25A-200V/282555840523?epid=10004560592&hash=item41c9a3f80b:g:y~AAAOSw8d5ZWsIu

Brian

 

[prv]

With the isolator off and the load circuit on, there is no need for a diode, where's the power going to go ?

Back down the "normal" supply and try to power everything else on the service bus?

If the OP has the typical arrangment of circuits and switches, and turns them all off when leaving, then it will only be trying to power other things on the same circuit instead of the whole bus - in my case that includes the VHF, some others it would probably include the plotter. The OP presumably doesn't want those randomly powering up on his unattended boat.

Pete

 

[PaulRainbow]

Read post #3

Why ?

We supplied Sealine with a similar setup, powered nav equipment from both battery banks, so no spikes during engine start.

In your case it would draw power from which source had the higher voltage if both powered on, solar if battery off.

In my case ?

Methinks you might be mis-quoting Brian ?

 

[PaulRainbow]

Back down the "normal" supply and try to power everything else on the service bus?

Of course it is, can i plead temporary insanity

If the OP has the typical arrangment of circuits and switches, and turns them all off when leaving, then it will only be trying to power other things on the same circuit instead of the whole bus - in my case that includes the VHF, some others it would probably include the plotter. The OP presumably doesn't want those randomly powering up on his unattended boat.

Pete

I agree, a Schotky diode in the supply from the isolator switch would be a simple enough solution.

 

[Yellow Ballad]

Back down the "normal" supply and try to power everything else on the service bus?

I hadn't thought of this, good shout.

The more I think about it the more it goes against my KISS outlook but good to know it's possible.