Solar Charging. VSR?

[DownWest]

Bit of advice on this. At the moment, the two batteries are charged off the engine alternator via a diode splitter. The next project is to fit an arch with a 100w solar panel.
So bearing in mind the voltage drop over the diodes, would a VSR be better for the solar circuit, while leaving the diode set for the alternator? Or just get rid of the diodes? Or?

TIA
DW

 

[VicS]

Bit of advice on this. At the moment, the two batteries are charged off the engine alternator via a diode splitter. The next project is to fit an arch with a 100w solar panel.
So bearing in mind the voltage drop over the diodes, would a VSR be better for the solar circuit, while leaving the diode set for the alternator? Or just get rid of the diodes? Or?

TIA
DW

Unless the alternator is "battery sensing" or you have an "advanced regulator" which is battery sensing you would do better by changing the alternator charging to a VSR system and using that for your solar charging. If you use a dual sensing VSR the alternator charge the starter battery as its first priority while the solar system can charge the house battery bank as its first priority

 

[DownWest]

Thanks Vic
The alt is the basic unit on the 1GM10 and from the 90s So I will have a look for a dual sensing VSR.
DW

 

[Malish]

Slightly more elaborate than your current system - I would pair the batteries up and make them the house batteries, linked directly to the solar via a regulator, and invest in a stand-alone small engine start battery AGM Red Flash or similar. Add in a VSR cluster with battery switches (BEP do plenty of variations) and that gives you the ability to start the engine from the house battery if the engine battery fails (never happened to me) and allows you to link the solar in to the start battery through the winter and keep it topped up - works for me

 

[PaulRainbow]

Thanks Vic
The alt is the basic unit on the 1GM10 and from the 90s So I will have a look for a dual sensing VSR.
DW

A Victron Cyrix battery combiner will do what you want, it's a dual sensing VSR.

 

[DownWest]

RR
The current set up has the batteries charged direct via the diodes. One is a designated engine battery, but there is one of Paul's bete noire 1-2- Both- 0ff switches that allows the use of either for starting. But domestic power goes direct from the domestic battery to the panel, not through the switch, which only affects the starter. The boat is only 27ft, so two 100amp batteries are prob enough with the LED lights and simple instruments.

Paul, thanks the Victron link.

 

[PaulRainbow]

RR
The current set up has the batteries charged direct via the diodes. One is a designated engine battery, but there is one of Paul's bete noire 1-2- Both- 0ff switches that allows the use of either for starting. But domestic power goes direct from the domestic battery to the panel, not through the switch, which only affects the starter. The boat is only 27ft, so two 100amp batteries are prob enough with the LED lights and simple instruments.

Paul, thanks the Victron link.

You're welcome.

So you don't have an isolator switch for the domestic circuits ? Is it fused close to the battery ? If not, i'd suggest you fit a breaker close to the battery, rated for the size of cable that goes to the domestic panel. This gives you an isolator, should you need it, and protects the wiring from short circuit or overload.

Something like one of these, https://www.asap-supplies.com/elect...akers/100-amp-electric-circuit-breaker-711584

 

[DownWest]

You're welcome.

So you don't have an isolator switch for the domestic circuits ? Is it fused close to the battery ? If not, i'd suggest you fit a breaker close to the battery, rated for the size of cable that goes to the domestic panel. This gives you an isolator, should you need it, and protects the wiring from short circuit or overload.

Something like one of these, https://www.asap-supplies.com/elect...akers/100-amp-electric-circuit-breaker-711584

The breaker panel is about a meter from the battery. So not too worried about the short run being fused. There is very little current draw, prob the biggest is the bilge pump, which apart from coming off a breaker, has it's own Man/Auto/Off fused panel. New DSC radio coming, not sure what the draw on that will be. The Log/Speed is a Nasa combined unit with low power draw.

 

[ghostlymoron]

The disadvantage of a vsr against diodes is that when the vsr is energised, the batteries are no longer isolated from each other so that, if there's a fault on either battery bank, they are connected together which could be a problem. So you might be better with low loss diodes.

 

[ghostlymoron]

You're advocating a very expensive solution.
He doesn't need a red flash battery unless space is a problem: almost any car type battery will do as a starter.

Slightly more elaborate than your current system - I would pair the batteries up and make them the house batteries, linked directly to the solar via a regulator, and invest in a stand-alone small engine start battery AGM Red Flash or similar. Add in a VSR cluster with battery switches (BEP do plenty of variations) and that gives you the ability to start the engine from the house battery if the engine battery fails (never happened to me) and allows you to link the solar in to the start battery through the winter and keep it topped up - works for me

 

[PaulRainbow]

The disadvantage of a vsr against diodes is that when the vsr is energised, the batteries are no longer isolated from each other so that, if there's a fault on either battery bank, they are connected together which could be a problem. So you might be better with low loss diodes.

Diodes impose too much voltage loss, particularly with solar power. A low loss splitter could be fitted for alternator charging and either leave the engine battery to fend for itself or fit an additional 10w solar panel to keep it topped up. There are some other expensive options too. But, the VSR would, in most circumstances, open if there was a problem with a battery that would likely flatten them all.

 

[DownWest]

Diodes impose too much voltage loss, particularly with solar power. A low loss splitter could be fitted for alternator charging and either leave the engine battery to fend for itself or fit an additional 10w solar panel to keep it topped up. There are some other expensive options too. But, the VSR would, in most circumstances, open if there was a problem with a battery that would likely flatten them all.

Interesting. There is room on the arch for another panel, so that might be the way to go. One of the problems is that while the boat is in a marina, a mains based charger is not viable, since the power is tripped in the early morning and has to be reset manually. (Both our local marinas do this)
I wasn't aware that the VSR linked the batteries, with the possible risk of discharging both.

 

[ghostlymoron]

Diodes impose too much voltage loss, particularly with solar power. A low loss splitter could be fitted for alternator charging and either leave the engine battery to fend for itself or fit an additional 10w solar panel to keep it topped up. There are some other expensive options too. But, the VSR would, in most circumstances, open if there was a problem with a battery that would likely flatten them all.

That's why I suggested low loss such as Shottky diodes which have much lower than the typical 0.7v for ordinary cheap diodes.

 

[VicS]

Interesting. There is room on the arch for another panel, so that might be the way to go. One of the problems is that while the boat is in a marina, a mains based charger is not viable, since the power is tripped in the early morning and has to be reset manually. (Both our local marinas do this)
I wasn't aware that the VSR linked the batteries, with the possible risk of discharging both.

That should not happen because the VSR will open again as the voltage falls. The manufacturers data sheet will tell you the voltage at which it initially closes and at which it will open again

The Victron Cyrix suggested by PR has quite a sophisticated operating program. Details on the data sheets

 

[PaulRainbow]

Interesting. There is room on the arch for another panel, so that might be the way to go. One of the problems is that while the boat is in a marina, a mains based charger is not viable, since the power is tripped in the early morning and has to be reset manually. (Both our local marinas do this)
I wasn't aware that the VSR linked the batteries, with the possible risk of discharging both.

I would fit as much solar as you have room for. Fit two panels of the same wattage, wired in series to a MPPT controller. Connect the controller to the domestic battery. You can then fit a VSR if you want them to keep the engine battery topped up, or leave it as it is if you are happy that the engine battery can look after itself.

IMO, a VSR is the better solution, as it not only keeps the engine battery topped up with solar power, it removes the voltage losses you currently get with alternator charging. Yes, the VSR links the batteries, but it only closes when the voltage at either battery reaches a per-determined level, so if your solar controller is charging the domestic bank and the voltage is high enough it will close (for example). If the starter battery failed in such a way that it tried to drain the domestic battery the voltage at the domestic battery would fall and the VSR would open. I have never heard of a VSR staying closed and allowing all batteries to be flattened, it goes against how they work.

 

[DownWest]

I would fit as much solar as you have room for. Fit two panels of the same wattage, wired in series to a MPPT controller. Connect the controller to the domestic battery. You can then fit a VSR if you want them to keep the engine battery topped up, or leave it as it is if you are happy that the engine battery can look after itself.

IMO, a VSR is the better solution, as it not only keeps the engine battery topped up with solar power, it removes the voltage losses you currently get with alternator charging. Yes, the VSR links the batteries, but it only closes when the voltage at either battery reaches a per-determined level, so if your solar controller is charging the domestic bank and the voltage is high enough it will close (for example). If the starter battery failed in such a way that it tried to drain the domestic battery the voltage at the domestic battery would fall and the VSR would open. I have never heard of a VSR staying closed and allowing all batteries to be flattened, it goes against how they work.

Thanks again. That is enough info to go with.
DW