12v circuit refit - ideas/refinements?

[PaulRainbow]

Getting there now, no doubt more tweaks.
So easy to operate, left switch controls where the boat gets its power from, 1-main bank, 2-emergency bank or both. Right switch controls where the solar goes, same.

Both charger feeds switched as well so at anchor the boat can be run from one bank with solar while the charger/genny does an equalizing cycle on the other. Might have missed something basic though,,,,, where you lot come in
(Edit, just spotted one, feed to windlass is after the domestic breaker..)

Which leaves trickle charging the emergency battery now and again, need to test a buck/boost voltage/current limited device, can't see why it wouldn't be fine though.

And commoning the big fat leads vaguely tidy, piled up on the same stud just always looks a mess.

The trip just after the left switch needs to be rated for the windlass, which makes it useless for protecting the wiring to the busbar etc. My previous suggestion of moving the windlass connection to the main bank should have been to move it to the isolator. That way you can have a lower rated breaker for the domestic wiring.

Edit, must type faster

 

[lpdsn]

Already spotted, edit above.

I don't seem to be able to pick up the edited diag. What I've got is Battery -> Breaker -> 1-2-Both Switch (spits on floor ) -> 2nd Breaker -> Bus Bar -> 3rd Breaker -> Windlass.

 

[GHA]

I don't seem to be able to pick up the edited diag. What I've got is Battery -> Breaker -> 1-2-Both Switch (spits on floor ) -> 2nd Breaker -> Bus Bar -> 3rd Breaker -> Windlass.

In the text -

Might have missed something basic though,,,,, where you lot come inimage: http://www.ybw.com/forums/images/smilies/cool.png

(Edit, just spotted one, feed to windlass is after the domestic breaker, which would be better above the bus bar anyway probably..)

 

[PaulRainbow]

In the text -

You're creating a bit of a fusing nightmare.

The breakers between each battery and its switch need to be rated for the windlass. The cables to the switches and the interconnecting cables also need to be rated for the windlass.

So, you need to connect the windlass wiring to the isolator or you cannot protect the wiring to the busbar. You can connect the busbar wiring to the isolator too, as it is in the diagram. You can now fit a breaker suitably rated to protect the domestic wiring to the busbar.

However, your starter cable may not be fully protected, unless it is rated the same as the windlass cable.

 

[lw395]

It is a dog's breakfast.

Are you intending to use comedy chinese breakers from ebay, or to spend hundreds of pounds?
If the breaker nearest the battery pops, e.g. due to the windlass jamming, while the engine is running, what do you think will happen to the alternator?

 

[GHA]

You're creating a bit of a fusing nightmare.

The breakers between each battery and its switch need to be rated for the windlass. The cables to the switches and the interconnecting cables also need to be rated for the windlass.

So, you need to connect the windlass wiring to the isolator or you cannot protect the wiring to the busbar. You can connect the busbar wiring to the isolator too, as it is in the diagram. You can now fit a breaker suitably rated to protect the domestic wiring to the busbar.

However, your starter cable may not be fully protected, unless it is rated the same as the windlass cable.

Yep, getting a bit messy down that neck of the woods. Windlass might just end up where it is now, straight on the battery post. Then again after yonks on the hook there's always this nag that the boat needs to be able to move at a moments notice and if the main bank is out of action for some reason - no windlass.... Hmmmmm.. Sleep on that for a few nights I think.

 

[GHA]

Are you intending to use comedy chinese breakers from ebay,

Thinking kit kat paper actually.

 

[zoidberg]

'My brain hurts' just reading this. Stress-test? You betcha.... But this interplay is impressive - and so it should be!

Now, I have a similar set of problems, with different difficulties/questions. Would anyone mind greatly If I presented/posed them on another thread, over the next day or two? Unless outlandish, I WILL implement the consensus.

I'll detail what I have and what I want....er, need. I'll detail the constraints, and what is there already.

Then there are the practical real-world issues, such as that I can live without 'fridge-cooled beer' because I can always go to the pub while musing on a Lecky QikFix. Waterside pubs manage, I've noticed along the way, to produce cool beer quite well, as salve for distressed sailors. As for 'upping the anchor', if it comes on to blow, I have another, traditional, solution which involves no 'lecky but rather more chain.

 

[GHA]

'As for 'upping the anchor', if it comes on to blow, I have another, traditional, solution which involves no 'lecky but rather more chain.

Been there! Solo, with a bust engine and bust manual anchor windlass as well. Quite challenging the first time..but the novelty wears off trying to get back somewhere that actually has boaty bits

I suspect most cruisers get very obsessed with self sufficiency after a while, so maybe not everyone understands to emphasis put on a setup which probably seems just plain odd to many.

It ain't!!! , solid reasons for going this direction.

 

[PaulRainbow]

I suspect most cruisers get very obsessed with self sufficiency after a while, so maybe not everyone understands to emphasis put on a setup which probably seems just plain odd to many.

It ain't!!! , solid reasons for going this direction.

It is odd

It's also clunky and you have some issues with fusing and the issues with the windlass connection. Be careful of bodging patches over a flawed arrangement.

Looking back at my original suggestions a little....... Buy a simple on/off isolator and connect that in place of the proposed main bank isolator. Fit the fused cable from the battery to the supply terminal, unless the cable is located where it cannot possibly short, such as a wooden/grp locker. If it isn't fused you don't have the issue with the windlass possibly being able to trip the domestics.Connect the windlass cable and the cable to the domestic busbar to the load terminal. Both with appropriate breakers. You now have a simple, isolated domestic circuit.

Connect one of your 1-2-both switches to the 2nd battery and the engine as i previously said, with a link wire to the load terminal of the domestic isolator switch. You now have two isolated circuits, but can run the engine from either or both banks as well as being able to run the domestics from either or both banks.

The second 1-2-both switch can be used for the solar controller, although i see little value in this.

Connect the alternator output cable directly to the 2nd battery and fit a VSR between the two banks. This means that no matter which breaker trips the alternator will still be charging and both batteries get charged. You could fit a Sterling A2B charger rather than the VSR and have the alternator connect to the standard output with a boosted output for the domestic bank.

This should resolve all of the outstanding issues, albeit it you would need to spend a few quid.

I should add, this would not be a system i would normally design for someone.

 

[GHA]

Looking back at my original suggestions a little....... Buy a simple on/off isolator and connect that in place of the proposed main bank isolator. Fit the fused cable from the battery to the supply terminal, unless the cable is located where it cannot possibly short, such as a wooden/grp locker. If it isn't fused you don't have the issue with the windlass possibly being able to trip the domestics.Connect the windlass cable and the cable to the domestic busbar to the load terminal. Both with appropriate breakers. You now have a simple, isolated domestic circuit.

Connect one of your 1-2-both switches to the 2nd battery and the engine as i previously said, with a link wire to the load terminal of the domestic isolator switch. You now have two isolated circuits, but can run the engine from either or both banks as well as being able to run the domestics from either or both banks.

Which is almost the same as the very first offering except with domestic coming off bank 1 instead of switch 1 common. Flaws is that starter/alternator come from the same wire so if using the 2nd bank to start (which I don't want to do, it will be treated like royalty) then only it gets the alternator.

The second 1-2-both switch can be used for the solar controller, although i see little value in this.

How do you load test a bank using solar to keep the other one happy? How do you use solar to equalize a bank?
Not sure you get the whole self sufficient away from everything thing That's the main reason for doing any of this.

Connect the alternator output cable directly to the 2nd battery and fit a VSR between the two banks. This means that no matter which breaker trips the alternator will still be charging and both batteries get charged. You could fit a Sterling A2B charger rather than the VSR and have the alternator connect to the standard output with a boosted output for the domestic bank.

Why bother? , nothing really to be gained really apart from lightening the wallet. The engine rarely if ever needs to get used for charging, maybe a handful of aH per year just from motoring. Not what should happen, not what could happen - what *does* happen. After lots solar was added anyway, if anything else is needed the genny runs the mains charger. Been living aboard for more than a decade, it works.

I should add, this would not be a system i would normally design for someone.

You don't normally design for cruising boats then.

Schematic without the breakers etc which was getting the grumps jumping up and down and will get sorted out along the way.

Looks same as yours except windlass/domestic doesn't go to bank 1. Might be some merit in that though, combined alt/starter circuit diminishes the usefulness a bit though and makes it more difficult to load test/equalize the main bank so maybe not worth it.
Everything fine starting the engine apart from the VHF reboots.

 

[lw395]

Fundamentally, if you rely on a 1b2 switch to share the solar between the batteries, one day you will find both batteries flat.

I'm not as anti them as Paul is, but they need to be used with discipline, never on 'both' unless the engine is running. (or a last ditch attempt at starting!)

Also there is a theoretical objection to charging the second battery at the same voltage as the first, if they are not seeing the same load regime.
You could be overcharging the 2nd battery, it might be useless the day you want it. I appreciate that you spend a lot of time monitoring and might not fall down this trap, but in general it's far from ideal.

 

[GHA]

Fundamentally, if you rely on a 1b2 switch to share the solar between the batteries, one day you will find both batteries flat.

I'm not as anti them as Paul is, but they need to be used with discipline, never on 'both' unless the engine is running. (or a last ditch attempt at starting!)

Also there is a theoretical objection to charging the second battery at the same voltage as the first, if they are not seeing the same load regime.
You could be overcharging the 2nd battery, it might be useless the day you want it. I appreciate that you spend a lot of time monitoring and might not fall down this trap, but in general it's far from ideal.

Thought long and hard about this - really can't see realistically how that will happen plus it's never happened in over a decade, it's conceivable but as the 2nd bank will hardly ever be touched and with the voltage alarm / monitoring in place as unlikely as it gets.
An example maybe - how could it happen? Given bank 2 will be isolated almost permanently.


Back up the thread - there'll be a dc buck boost to trickle a bit into 2nd bank if it needs it. This has been tested on a smaller lead acid, works great with set points for current/voltage cut off.

Maybe there's a significant chance of discharging both on weekend boats with people onboard who don't have experience & instinct with being completely 100% reliant on batteries all the time.

 

[lw395]

I've seen a few people who thought 'only other people could flatten both batteries' come unstuck.

 

[GHA]

I've seen a few people who thought 'only other people could flatten both batteries' come unstuck.

Maybe an example of how it could happen, how do other people get caught out?
I genuinely can't see how it's a risk significant enough to worry about. A 1/2/B switch relocated to under the chart table closer to the batteries permanently set to '1' with big label - 'SET TO 1 ONLY'.



How many full time on the hook boats do you get in the solent?

Must be an easier way to plot databases... a few weeks in August before fitting a victron MPPT regulator-never below 12.4v. Will prob set the alarm to 12.4v for main bank and see the datasheet for 2nd bank, but up near 12.7v.

 

[<152587>]

Maybe an example of how it could happen, how do other people get caught out?
I genuinely can't see how it's a risk significant enough to worry about. A 1/2/B switch relocated to under the chart table closer to the batteries permanently set to '1' with big label - 'SET TO 1


How many full time on the hook boats do you get in the solent?

Must be an easier way to plot databases... a few weeks in August before fitting a victron MPPT regulator-never below 12.4v. Will prob set the alarm to 12.4v for main bank and see the datasheet for 2nd bank, but up near 12.7v.

Or a single throw battery switch

 

[lpdsn]

Even if you want to keep the 1-2-Both switches to select which battery you're running off ( I wouldn't because I strongly believe in spec'ing the banks for their main purpose, but that's by the by) I still can't understand why you want to charge through them these switches. It just makes things an awful lot simpler if charging and usage are separate circuits.

 

[<152587>]

Life threatening abilities of DC are thought to be around 60v 500mA, this is not definitive. I have felt tickles at 24 volts whilst working on systems in hot climates due to being sweatier than a glass blowers armpit.

If you research the market the OCV is rising as panels strive for efficiency. They are commonly producing voltages nearly double that understood to be a life threat.

This progress is also introduced to the MPPT where it auto-senses system voltage and auto-sets 12 or 24. This needs a connection protocol that will cause the installer to work with the feed from the PV's live unless a breaker is fitted into the feed.

Note that I did not specify a circuit breaker, which would be quite incorrect, read breaker as in switch or any other isolation device you may specify .

 

[GHA]

Even if you want to keep the 1-2-Both switches to select which battery you're running off ( I wouldn't because I strongly believe in spec'ing the banks for their main purpose, but that's by the by) I still can't understand why you want to charge through them these switches. It just makes things an awful lot simpler if charging and usage are separate circuits.

??

Alternator & starter are combined anyway so no option there really without major surgery.

Solar is separated through a switch to choose the destination(s) - main reason for this in the first place. Just happen to join the batteries at the left switch on the schematic, could go straight to the terminals but that might result in more messy wiring in the battery box.

Mains charger is a separate circuit.

So lots of "this is a bad idea", anyone care to go indo details of why it's so awful specific to this setup where the criteria is all loads switchable to either or both banks, solar switchable independently to either / both banks, mains switchable independently to either/both banks. Solo full time liveaboard nearly always on the hook.

Difficult to see what would be gained by just going with on/off switches rather than 1/2/both. Apart from wallet lightening and more wiring.

 

[pvb]

Difficult to see what would be gained by just going with on/off switches rather than 1/2/both. Apart from wallet lightening and more wiring.

The gain - and it's a significant and valuable gain - is simplicity and a fail-safe solution. It's all very well having those antique 1-2-Both switches if you're absolutely sure you know what you're doing, but there's always a chance that, even if you don't set it wrongly, someone else might. Then you could find yourself with engine starting difficulties, as the RNLI frequently find. Designing the system with simple on-off switches makes it impossible to get it wrong, which is why the vast majority of modern boats use simple on-off switches.

I think if there's one thing this thread reveals, it's that you didn't really want ideas or refinements in the first place.