One charge controller, two battery banks

[SV Kittiwake]

Our new boat has multiple battery banks. We're running off one solar panel, a 420AH house battery and a standard starter battery.

The panel will route via a Victron 75/15 charge controller. Is there a way this can charge both battery banks? Maybe a simple toggle switch so that once the house batteries are charged, I can flip it over to the starter battery. Or is there a device to do this automatically?

 

[matthewriches]

You could rig a VSR (voltage sensing relay) that'll combine the domestic and engine battery until such time as 1 or the other goes below a certain parameter, and will then disconnect.

There are multiple output controllers that have been mentioned before, I posted a link a long time ago but cannot find it easily at the moment.

 

[VicS]

Our new boat has multiple battery banks. We're running off one solar panel, a 420AH house battery and a standard starter battery.

The panel will route via a Victron 75/15 charge controller. Is there a way this can charge both battery banks? Maybe a simple toggle switch so that once the house batteries are charged, I can flip it over to the starter battery. Or is there a device to do this automatically?

A VSR or a low loss diode splitter such as a Victron Argofet will charge both simultaneously

But how are you splitting the charge from the alternator at the moment. The above devices can 2 split the output from the alternator automatically between the batteries too

 

[Kelpie]

You can get comparatively inexpensive charge controllers that will handle two banks. Mine is rated to 20A and cost about £30 off eBay. It's still going strong after five years.
What size solar panel do you have?

P.S. love your videos. Looking forward to seeing the new boat.

 

[SV Kittiwake]

Thanks everybody, you've given me some things to google.

Matthew - Would something like this do? https://sterling-power.com/products/split-charge-diodes-70-200a-2-3-outputs?variant=884773159

It's designed for alternators, but our solar installation is much lower amperage (max 15A).

Vic - there are two alternators, one of which goes into an adverc smart charger, something I need to find out more about but I don't think it'll solve my problem.

Kelpie - thanks a lot! We're enjoying living on the new boat, there's a couple of videos left on Kittiwake then we'll be moving over. I've used Victron charge controllers before and like them, so wanted to stick with that brand. The Marlec one that was on the boat had two outputs, but it was max 5A input.

 

[PaulRainbow]

Thanks everybody, you've given me some things to google.

Matthew - Would something like this do? https://sterling-power.com/products/split-charge-diodes-70-200a-2-3-outputs?variant=884773159

No, that's an old tech diode splitter, steer clear of it.

A simple VSR should fit the bill : https://www.batterymegastore.co.uk/victron-energy-cyr010120011r.html

This will allow the solar controller to charge both banks, it will also allow the alternators to charge all batteries. This might be useful if you have a small alternator for engine charging and the adverc charging the domestics, as you'd get charge from the small alternator going to the domestic bank.

If you wanted to keep everything to do with the alternators separate, you could fit one of these https://www.batterymegastore.co.uk/victron-energy-arg100201020r.html This will charge both banks from the solar controller, whilst keeping them isolated from one another at all times.

It would be useful to know how the existing alternator and charging are wired.

 

[Pete7]

Thanks everybody, you've given me some things to google.

Kelpie - thanks a lot! We're enjoying living on the new boat, there's a couple of videos left on Kittiwake then we'll be moving over. I've used Victron charge controllers before and like them, so wanted to stick with that brand. The Marlec one that was on the boat had two outputs, but it was max 5A input.

No, No, you have let the cat out of the bag now, you will have to spill the beans :encouragement:

Keep up the good work, I enjoyed your travels on Kittiwake.

 

[noelex]

A VSR or a low loss diode splitter such as a Victron Argofet will charge both simultaneously

But how are you splitting the charge from the alternator at the moment. The above devices can 2 split the output from the alternator automatically between the batteries too

A VSR is good solution.

I have never tried the low loss diode splitters for solar, but they have the problem that there is 0v on the input pin when idle. This causes an issue with many solar controllers. Controllers generally require, or at least expect to see, a battery voltage at start up.

Those that have tried, tell me they don’t work, at least in some cases.

So low loss diode splitters fine for alternators. Although you might logically expect these devices to also work for solar that is not correct.

As the low loss diode splitters are costly it could be an expensive mistake, hence the warning, although I have never verified this myself.

 

[SV Kittiwake]

Thanks for the clarification Noelex. I'll admit that the electronics terminology is all a bit beyond me. It looks like the Victron Cyrix-ct is the winner, I've written to Victron themselves to double check, as even that doesn't explicitly state that it's for solar charge controllers.

 

[noelex]

Thanks. Also enjoy your videos, although the bandwidth of the internet connection on the boat sadly means I seldom have the opportunity to do so.

The Cyrix-ct is a VSR if I understand correctly, so it should work fine, but checking with the manufacturer is always a good idea. The issue I was referring to above only applies to the low loss diode splitters. These use a very different switching mechanism to a VSR.

 

[VicS]

A VSR is good solution.

I have never tried the low loss diode splitters for solar, but they have the problem that there is 0v on the input pin when idle. This causes an issue with many solar controllers. Controllers generally require, or at least expect to see, a battery voltage at start up.

Those that have tried, tell me they don’t work, at least in some cases.

So low loss diode splitters fine for alternators. Although you might logically expect these devices to also work for solar that is not correct.

As the low loss diode splitters are costly it could be an expensive mistake, hence the warning, although I have never verified this myself.

Good point... I wonder if there is a "work around" using the alternator "energise" connection on an ArgoFET ?

 

[PaulRainbow]

Thanks for the clarification Noelex. I'll admit that the electronics terminology is all a bit beyond me. It looks like the Victron Cyrix-ct is the winner, I've written to Victron themselves to double check, as even that doesn't explicitly state that it's for solar charge controllers.

The Cyrix is absolutely 100% fit for solar charging, i've fitted loads of them and have one on my own boat, with 260w of solar.

 

[SV Kittiwake]

The Cyrix is absolutely 100% fit for solar charging, i've fitted loads of them and have one on my own boat, with 260w of solar.

Ah, good stuff - I'll grab one. Thanks for your help!

 

[PaulRainbow]

I have never tried the low loss diode splitters for solar, but they have the problem that there is 0v on the input pin when idle. This causes an issue with many solar controllers. Controllers generally require, or at least expect to see, a battery voltage at start up.

Those that have tried, tell me they don’t work, at least in some cases.

That's a good point, i hadn't considered that.

If i get a few minutes spare one day i might try it with my own installation.

 

[Piddy]

Sorry to drag up an old post

I'm just fitting a 400W solar panel and have a Victron mppt and wanted to use a Victron ArgoFet splitter. Now I see there are doubts about the splitter being energised.
Does anyone know if this works?

Thanks,

Piddy