Adding a 3rd battery or, a higher amp alternator? Which is best? Both isn’t the answer! CPAP

[lw395]

You are correct. The question was about increasing ampH or not, so increasing his battery total is the correct answer.
...

The OP's actual question was a spurious binary choice between changing the alternator and adding another battery.
As usual, the forum has mostly responded by instructing him to spend about a grand on refitting the whole electrics.

 

[PaulRainbow]

Solar power 24/7 - that's a neat trick unless you are above the Arctic circle in summer!

Far be it from me to defend Paul’s statement but many of us run off solar power 24/7. That’s what battery banks are for and I don’t know any other way of using solar.

Beat me to it, thanks

 

[PaulRainbow]

Why the emergency combine switch? why not use a Victron Cyrix-CT? it has a "power-assist" function that you can wire in. 30 quid and Bob's your uncle. The domestic and engine switch are then only used to switch off the batteries when not in use.

The Cyrix "power assist" has very limited usefulness, there is a limit to the power you can draw through the relatively small cables used for connecting the VSR, and a limit to how long you can use it. A 3rd switch, connected to the load terminals of the two main isolators allows more current to flow, for a longer time. It also has other advantages, if (for instance) the engine battery is totally knackered it can be isolated by turning its switch to "off" and turning the emergency switch to "on", thus running everything from the domestic bank, same applies in the event of a failed domestic battery/bank.

 

[prv]

The OP's actual question was a spurious binary choice between changing the alternator and adding another battery.

...when probably neither was necessary since his device only uses a couple of amp-hours anyway.

Or perhaps it might use more - maybe his is the type with a humidifier and has to run a small heater? - but he never bothered to tell us how much despite being asked.

As usual, the forum has mostly responded by instructing him to spend about a grand on refitting the whole electrics.

Be fair, some people just took the opportunity to make non-sequiteur statements about their own electrics without giving any instruction or advice

Pete

 

[PaulRainbow]

Your advise is fine for those who wish to accept it. Me and many others who have a life time of sailing experience and tens of thousands of miles under their keel don't find the need for a device that doesn't do what they want. I will decide when to join my batteries together for charging not a piece of electronics. When you have multiple charging systems such as a diesel genset, large solar array, towed generator and wind generator you are not reliant on the alternator to charge the batteries. I have never forgotten to take the batteries off the both position on the switch. The large led voltage displays for each battery bank clearly show voltage on each bank 24/7. If they are the same readings then hay, maybe the switch is still on both! So in my case and many others the both position is not for emergency use. It doesnt matter how many times you say it on this forum I will keep correcting you. All boats are not the same. There is more than one way to skin a cat.

In this thread alone, i have said ;

"Here's a basic schematic, if you don't want to fit the VSR simply leave it out."

"Feel free to use your switch however you see fit,"

I'm perfectly well aware that "not all boats are the same", i work on them all day, every day and that includes designing commercial systems that have to undergo coding inspections.

It's perfectly possible to design a system with multiple charging systems and multiple battery banks, that don't have unnecessary risks or user intervention and feature maximum safety and redundancy. How about ;

Charging ;
Port engine
Stb engine
Genset
Solar
Shore power

Batteries ;
Port engine
Stb engine
Domestic bank
Bow thruster
Stern thruster
Genset

Throw in an inverter for good measure. All batteries to be charged by any one charging device, or multiples thereof, whilst keeping each bank isolated from the others. There also has to be maximum redundancy, every bank must have the ability to be fully isolated from the systems and it's own systems to be powered by an alternative source.

A 1-2-B switch didn't feature here.

 

[geem]

In this thread alone, i have said ;

"Here's a basic schematic, if you don't want to fit the VSR simply leave it out."

"Feel free to use your switch however you see fit,"

I'm perfectly well aware that "not all boats are the same", i work on them all day, every day and that includes designing commercial systems that have to undergo coding inspections.

It's perfectly possible to design a system with multiple charging systems and multiple battery banks, that don't have unnecessary risks or user intervention and feature maximum safety and redundancy. How about ;

Charging ;
Port engine
Stb engine
Genset
Solar
Shore power

Batteries ;
Port engine
Stb engine
Domestic bank
Bow thruster
Stern thruster
Genset

Throw in an inverter for good measure. All batteries to be charged by any one charging device, or multiples thereof, whilst keeping each bank isolated from the others. There also has to be maximum redundancy, every bank must have the ability to be fully isolated from the systems and it's own systems to be powered by an alternative source.

A 1-2-B switch didn't feature here.

And your point is? Or are you just spouting off about how clever you are?

 

[RichardS]

As usual, the forum has mostly responded by instructing him to spend about a grand on refitting the whole electrics.

Although not PVB or me.

Richard

 

[PaulRainbow]

And your point is? Or are you just spouting off about how clever you are?

My point is, your setup, that you constantly tell us about, isn't actually that complicated. Some of us are capable of planning complex installations, as well as the more simple ones. Just because you want to stick with your 1-2-B switch, it doesn't mean that for many readers of these forums, and indeed the World at large, simple split charging systems work very well.

As usual, you're ranting about 1-2-B switches and VSRs. when my advice to the OP makes no mention of removing the switch, but simply suggests a VSR might be useful, whilst making it clear it's not an absolute must.

 

[PaulRainbow]

Although not PVB or me.

Richard

My advise consisted of a battery and some cable, hard to get that to come to a grand.

 

[RichardS]

My advise consisted of a battery and some cable, hard to get that to come to a grand.

My listing wasn't intended to be exclusive.

Richard

 

[Graham376]

I currently have a 2 x 100 amp leisure batteries on my Moody 30 with 28hp Beta Marine engine and 65 amp alternator.
1 leisure battery is used for starting, 1 for ‘house’ and a 1 / both / 2 switch for starting, alternator charging, battery use, etc....... and that’s my set-up.
I’m thinking of adding a standard 65amp (roughly) starter battery and then have the 2 leisure batteries as house batteries.
Would forumites recommend this or, would I be better served by a 100 amp alternator instead?

As others have said, a larger alternator won't solve your problem. My advice is to parallel the two leisure batteries, fit a dedicated engine battery and keep the 1,2,both isolator unless you sail with several different crew members who may cock things up, a VSR then makes sense. I have the 1,2,both switch and haven't managed to flatten the engine battery in 27 years of sailing.

 

[geem]

My point is, your setup, that you constantly tell us about, isn't actually that complicated. Some of us are capable of planning complex installations, as well as the more simple ones. Just because you want to stick with your 1-2-B switch, it doesn't mean that for many readers of these forums, and indeed the World at large, simple split charging systems work very well.

As usual, you're ranting about 1-2-B switches and VSRs. when my advice to the OP makes no mention of removing the switch, but simply suggests a VSR might be useful, whilst making it clear it's not an absolute must.

The OPs setup isnt complicated but you suggest his only solution is a VSR. You state 1-2-both switches are inferior by suggesting that Both should only be used in an emergency. I know my set up isn't complicated. Thats the way I designed it. If I wanted complicated I am qualified and capable of making it complicated but why would I wanted complicated? My last design project before I took early retirement was Project Director for £35M data centre. My responsibility was for £33M of the total build cost. We designed the whole mechanical and electrical installation on an N+1 basis. Computer controlled motorised breakers on main electrical distribution panels to automatically select alternative power supplies should a supply fail. We had three £1M pound diesel generators as back up, two supplies from different parts of the grid, full UPS back up for the IT load. We had the most efficient chillers in the world with rotors floating on computer controlled magnetic bearings. 3000m2 of IT space. We spent three months testing the cause and effect failure scenarios on project completion. A total of 3000 tests for all kinds of power and cooling failures. So yes you may be capable of wiring a boat with two engines and a VSR but dont assume you are the only person on the forum that knows a little.

 

[PaulRainbow]

The OPs setup isnt complicated but you suggest his only solution is a VSR. You state 1-2-both switches are inferior by suggesting that Both should only be used in an emergency.

The OP asked if adding a second battery was preferable to a bigger alternator, in his setup. He then asked for a schematic.

My reply, in post #11, which included the schematic he asked for, was ;

"It's a simple job to wire the additional battery in parallel. If you added a VSR you wouldn't have to fiddle around with the 1-2-B switch to keep the batteries all charged. They would all get charged whether the switch was on 1 or 2 (don't use it on both).

Here's a basic schematic, if you don't want to fit the VSR simply leave it out. "

Where does it say his only solution is a VSR ? ("if you don't want to fit the VSR simply leave it out.")

Where does it say his switch is inferior ?

I know my set up isn't complicated. Thats the way I designed it. If I wanted complicated I am qualified and capable of making it complicated but why would I wanted complicated?

I meant, your battery and charging arrangement would is not complicated to design and install a system for. You've decided to have and use it as it is, and that's absolutely fine, as i keep telling you. It would, of course, be an extremely simple task to remove the risks associated with using the switch on both (without removing the switch or adding a VSR) and still not have a complicated system. But, it's your choice to stick with what you have.

But, just because your system isn't suitable for a VSR it doesn't mean that a VSR might suit millions of other installations, which it does. A VSR isn't the only solution for any installation and is unsuitable for some. This thread isn't about every installation though and it most certainly isn't about your installation, it's about the OPs installation. I've offered some suggestions to the OP, regarding his installation, he's free to accept whatever advice he chooses,.

So yes you may be capable of wiring a boat with two engines and a VSR but dont assume you are the only person on the forum that knows a little.

A VSR isn't likely suitable for twin engine installations.

 

[PaulRainbow]

As others have said, a larger alternator won't solve your problem. My advice is to parallel the two leisure batteries, fit a dedicated engine battery and keep the 1,2,both isolator unless you sail with several different crew members who may cock things up, a VSR then makes sense. I have the 1,2,both switch and haven't managed to flatten the engine battery in 27 years of sailing.

Interesting to see this reply get a thumbs up from geem and RupertW, it's exactly what i suggested way back in post #11

 

[Graham376]

Interesting to see this reply get a thumbs up from geem and RupertW, it's exactly what i suggested way back in post #11

Maybe it's not what you say but the way you say it Whilst you often give very good advice, you regularly infer that using a 1,2,both switch is a stupid idea, which many of us who use one disagree with.

 

[pvb]

Maybe it's not what you say but the way you say it Whilst you often give very good advice, you regularly infer that using a 1,2,both switch is a stupid idea, which many of us who use one disagree with.

I don't think I've ever seen PaulRainbow describe the 1-2-Both switch as "a stupid idea". What he has said, and I've said the same countless times, is that there are easier solutions which are less prone to user error. With a 1-2-Both switch, user error can lead to flat batteries and engine starting difficulties, something which SeaStart and the RNLI have lots of experience of.

 

[Graham376]

With a 1-2-Both switch, user error can lead to flat batteries and engine starting difficulties, something which SeaStart and the RNLI have lots of experience of.

So you add a VSR which is an additional point for potential failure. If people can't even remember to switch batteries, God help us if they ever take up flying.

 

[pvb]

So you add a VSR which is an additional point for potential failure. If people can't even remember to switch batteries, God help us if they ever take up flying.

A VSR isn't going to flatten batteries if it fails. And a VSR is only one alternative, I favour the low-loss splitter, especially as this solution lends itself to those of us who have engine, domestic and bowthruster batteries to charge separately.

 

[PaulRainbow]

So you add a VSR which is an additional point for potential failure. If people can't even remember to switch batteries, God help us if they ever take up flying.

Adding a VSR to a simple installation that uses a 1-2-B switch removes the risk of user error. It also saves having to run up and down companionway steps changing switch positions (depending on where the engine panel and the switch are located, of course).

It doesn't add any failure points. If the VSR fails, you're just back to where you were before you fitted it.

 

[saab96]

I have similar 2+1 battery arrangement. You should fit a charge splitter/diode battery isolator to keep house and starter batteries apart unless the alternator is feeding in current.

Some time ago YM suggested a Voltage Sensitive Relay (VSR) rather than a diode isolator because the resistance of a diode isolator causes a big voltage drop when charging. VSR isolates batteries until it senses voltage rise.