Battery switch advice

[Stemar]

Ideally I’d like solar and engine charging to all batteries in the background, regardless of switch position - sounds like that may or may not be the case…

The solar bit can be done with something like this. I had one on my previous boat. I set it to charge the engine battery until it burps, then turn its attention to the domestic system, on the basis that the engine battery's rarely going to need much, but I really want it not to be flat, while the domestic one was likely to take most of my solar for a good while. It's cheap and cheerful, but worked well. For a more efficient setup, there are dual battery MPPT controllers, like this one.

Engine charging to all batteries just needs a VSR that will put the batteries in parallel when the alternator's doing its thing. I used a cheap headlamp relay excited by the field terminal of the alternator because my budget was tiny and VSRs were a lot more expensive than they are today.

One final thought - a question for the experts - would a VSR sensing the engine battery's voltage mean a single battery solar controller could charge the engine battery, and the VSR would pass current on to the domestic bank?

 

[lustyd]

One final thought - a question for the experts - would a VSR sensing the engine battery's voltage mean a single battery solar controller could charge the engine battery, and the VSR would pass current on to the domestic bank?

Yes, and I was gearing up to point that out while reading your first bit what a VSR can’t do is let a charge profile work properly on two banks so most with lithium ditch the VSR and separate charging.

 

[PaulRainbow]

Ok , but whatkind of engine electrics does the "engine" switch actually control ? Like said previously there are even separate EDC switches for both engines ...

The switches above the 1-2-B switch will isolate the batteries from the engines. The EDC switches isolate the EDCs, these are additional, non-factory switches. I i remember correctly, with some installations the EDCs drained the batteries, but can't remember the specifics, hence the extra switches, try askingthat question on the mobo forum.

 

[PaulRainbow]

One final thought - a question for the experts - would a VSR sensing the engine battery's voltage mean a single battery solar controller could charge the engine battery, and the VSR would pass current on to the domestic bank?

Yes. But most VSRs are dual sensing, so it doesn't matter much where you connect the solar panel, but the domestic bank is common.

 

[Refueler]

The solar bit can be done with something like this. I had one on my previous boat. I set it to charge the engine battery until it burps, then turn its attention to the domestic system, on the basis that the engine battery's rarely going to need much, but I really want it not to be flat, while the domestic one was likely to take most of my solar for a good while. It's cheap and cheerful, but worked well. For a more efficient setup, there are dual battery MPPT controllers, like this one.

Engine charging to all batteries just needs a VSR that will put the batteries in parallel when the alternator's doing its thing. I used a cheap headlamp relay excited by the field terminal of the alternator because my budget was tiny and VSRs were a lot more expensive than they are today.

One final thought - a question for the experts - would a VSR sensing the engine battery's voltage mean a single battery solar controller could charge the engine battery, and the VSR would pass current on to the domestic bank?

I use a headlight relay to switch on my coolbox when alternator starts outputting .. like you its a cheap easy way to do it. As I see it - VSR's are still not cheap ...

With regard to VSR with solar - local electrics guy here told me its not a good way as some will - some won't ... better is to get a dual Solar Controller and forget about it ... which I did.

 

[PaulRainbow]

I use a headlight relay to switch on my coolbox when alternator starts outputting .. like you its a cheap easy way to do it. As I see it - VSR's are still not cheap ...

With regard to VSR with solar - local electrics guy here told me its not a good way as some will - some won't ... better is to get a dual Solar Controller and forget about it ... which I did.

Your local "electrics guy" is wrong, i've fitted dozens of VSRs on boats with solar. The VSR doesn't know or care where the electricity is coming from.

 

[Refueler]

Your local "electrics guy" is wrong, i've fitted dozens of VSRs on boats with solar. The VSR doesn't know or care where the electricity is coming from.

His comments were that using a VSR for controlling Solar charge direction ... that some VSR's can and some cannot.

TBH - I don't see why spend price of a VSR when a dual controller can be significantly cheaper ...... then the question never arises ...

 

[lustyd]

TBH - I don't see why spend price of a VSR when a dual controller can be significantly cheaper ...... then the question never arises ...

The VSR works with the alternator and any other input too.

 

[PaulRainbow]

His comments were that using a VSR for controlling Solar charge direction ... that some VSR's can and some cannot.

Don't see why, it closes at specific voltages and opens at other voltages. Electricity is electricity, doesn't matter how it's generated.

TBH - I don't see why spend price of a VSR when a dual controller can be significantly cheaper ...... then the question never arises ...

It's not always about money. If you want decent MPPT charging dual controllers are generally not the best, most just offer tiny trickle charging for the second battery. A VSR will also let all charging sources charge two banks. Not the be all and end all solution, but works well for many small/simple boat systems.

 

[PaulRainbow]

The solar bit can be done with something like this. I had one on my previous boat. I set it to charge the engine battery until it burps, then turn its attention to the domestic system, on the basis that the engine battery's rarely going to need much, but I really want it not to be flat, while the domestic one was likely to take most of my solar for a good while. It's cheap and cheerful, but worked well. For a more efficient setup, there are dual battery MPPT controllers, like this one.

Engine charging to all batteries just needs a VSR that will put the batteries in parallel when the alternator's doing its thing. I used a cheap headlamp relay excited by the field terminal of the alternator because my budget was tiny and VSRs were a lot more expensive than they are today.

One final thought - a question for the experts - would a VSR sensing the engine battery's voltage mean a single battery solar controller could charge the engine battery, and the VSR would pass current on to the domestic bank?

Steve, if there is a VSR for the engine to charge the domestics, that will allow the domestics to charge the engine. Fitting a VSR and a dual output solar controller is a bad idea, because the VSR will close when the solar starts charging and parallel all of the batteries, both outputs of the solar controller will then be connected to the same bank, which can damage/destroy some controllers.