Jump to content

Battery/alternator/solar wiring schematic


swift1894

Featured Posts

Each isolator introduces resistance and additional failure possibilities. Personally I think it is better to install safely and keep the wiring in good condition. There are millions of cars without battery Isolators to the alternator, how many go on fire due to a short in the alternator circuit?

 

Better to have a fuse or two (which of course is mandatory anyway) so that wiring shorts to bilge pumps etc are protected against. We do in fact have a 500A fuse through which everything including the non-isolatable alternator passes, to give me peace of mind with no risk of trashing the alternator by opening an isolator accidentally.

Edited by nicknorman
Link to comment
Share on other sites

Each isolator introduces resistance and additional failure possibilities. Personally I think it is better to install safely and keep the wiring in good condition. There are millions of cars without battery Isolators to the alternator, how many go on fire due to a short in the alternator circuit?

Better to have a fuse or two (which of course is mandatory anyway) so that wiring shorts to bilge pumps etc are protected against. We do in fact have a 500A fuse through which everything including the non-isolatable alternator passes, to give me peace of mind with no risk of trashing the alternator by opening an isolator accidentally.

Thanks Nick, still getting used to 12 volt systems. In the power systems I am used to working on resilience is everything, but the isolators and switches on them very rarely fail, unlike the cheap 12 volt ones!

 

Must check to see if DQ hasca mega fuse, and fit one if there isn't one already fitted.

Link to comment
Share on other sites

These maxi midi fuseboxes may make thing a little easier.

 

20150330_25.JPG

 

As said, some like to have the solar and mains charger on a feed that bypasses the idolator. One way to do this with the above would be cut the midi link strip say in the middle and have another feed coming in from the side or bottom (can mark up pic if it helps).

 

Also as said, sometimes it's good to have some overcurrent protection for the alt feed if a bit vulnerable, (seems to be a BSS requirement anyway?) in which case it might be best to have a separate fuse so it doesn't get disturbed accidentally.

 

cheers, Pete.

~smpt~

Link to comment
Share on other sites

Dammit! just started the battery changeover ( very early stage) and discovered that the shunt is after the isolator switch on the negative cable about 60cm away from the batteries and can't be moved any nearer to the batteries as the cables have been cut to the existing layout. So I'll have to send a cable from the shunt back to the negative busbar which will be next to the batteries, and the send a cable from the bus bar back to where the original cable left the shunt going to the charger.

Any problem with that?

Edited by swift1894
Link to comment
Share on other sites

You have isolators in the negative cables? Now is the time to swap this to having them in the positives. Obviously an amount of new cabling might be needed.

But I read elsewhere that the isolator should be in the neg cable.?

I feel a debate is imminent!?

Edited by swift1894
Link to comment
Share on other sites

But I read elsewhere that the isolator should be in the neg cable.

I feel a debate is imminent!

 

Putting it the negative facilitates the use of one switch for both the engine and domestic battery bank. However it is considered poor practice although a few on here differ in that view. If you have any of the items that are allowed to bypass the master switch then if it is in the negative trying to operate any circuit, especially high current ones could result in a fire if the switch is turned off. Its your choice but I would not do it.

 

Ideally you need to keep all battery, charging and starting cables to the minimum length so I would move the shunt. The two thin wires on the shunt only carry milliamps so using a crimp splice to lengthen they is unlikely to cause a problem, especially if you use the adhesive heat shrink type. The larger cables can keep their existing terminals but connect them together on an insulated power distribution post. This is a bit of a bodge but should not cause any problems that I can see.

 

 

 

 

 

Link to comment
Share on other sites

Do you have a link to the thread?

 

Isolator switch - strongly advised to be in the positive

Shunt - strongly advised to be in the negative

 

http://www.smartgauge.co.uk/whereiso.html

Found this

 

 

It is not uncommon for the isolation switch to be in the negative, indeed it used to be the standard practice. The main reason was that if you have only a single alternator, then just one isolator switch will disconnect both domestic and starter batteries which as well as being cheaper is also a very good safety feature. It also has other advantages including the fact that when it is switched off the accidental dropping of either one of the positive or negative battery cables on to the hull while connecting or disconnecting a battery will not cause a big bang. Gibbo - a once highly respected electrical expert on this Forum - years ago published on his website a list of reasons why the switch should be on the positive side; the only one of those reasons which I (a retired electrical expert) agree with is the one which states that the positive side is where nowadays people expect to find it. Personally by choice I have my switches (both of them now that I have a two-alternator setup) in the negatives and megafuses in the positive.

Link to comment
Share on other sites

Edit: http://www.canalworld.net/forums/index.php?showtopic=78244

 

Note that post #9 on that thread presents a coherent argument against installing the isolators in the negative.

Looks like I'll be swapping the isolator over to the positive cable then.

Yep, and I entirely disagree with his conclusions for the majority of boaters.

Tony

Link to comment
Share on other sites

  • 3 weeks later...

 

Ideally you need to keep all battery, charging and starting cables to the minimum length so I would move the shunt. The two thin wires on the shunt only carry milliamps so using a crimp splice to lengthen they is unlikely to cause a problem, especially if you use the adhesive heat shrink type.

 

Took your advice and moved the shunt.

Thanks

Link to comment
Share on other sites

I'm a bit puzzled by the suggestion that it's OK to connect chargers directly to battery positives, bypassing the isolator switch. I thought that the idea of an isolator switch was to isolate the battery bank so that any wiring fault, no matter where, could be disconnected from the bank, or could be used whilst working on the system to ensure that no inadvertent shorts were created.

Link to comment
Share on other sites

I'm a bit puzzled by the suggestion that it's OK to connect chargers directly to battery positives, bypassing the isolator switch. I thought that the idea of an isolator switch was to isolate the battery bank so that any wiring fault, no matter where, could be disconnected from the bank, or could be used whilst working on the system to ensure that no inadvertent shorts were created.

It's specifically allowed by the BSS provided there is adequate fusing. You want to be able to turn off the master when you leave the boat, whilst leaving the charger charging the batteries. If you put the charger input on the boat side of the isolator it means that (if the charger is on) all the boat's services are live when the battery isolator is off.

Link to comment
Share on other sites

It's specifically allowed by the BSS provided there is adequate fusing. You want to be able to turn off the master when you leave the boat, whilst leaving the charger charging the batteries. If you put the charger input on the boat side of the isolator it means that (if the charger is on) all the boat's services are live when the battery isolator is off.

 

If you can turn off the isolator when leaving the boat, but have the batteries still charging, then really what you've got is a load isolator rather than a battery isolator.

Link to comment
Share on other sites

All positives go to one end of the battery bank and all negatives go to the other end.

 

As you have bus-bars use those instead of the battery terminals, then it will just need one cable from each bus-bar to the batteries.

 

The shunt assuming it for for reading of amperes(gauge), should go in the negative from the bus-bar to the battery bank

 

Ha ha! That reminded me of 'All dinosaurs are thin at one end, thicker in the middle, then thin again at the other end'!

 

(Monty Python's Flying Circus)

Link to comment
Share on other sites

 

If you can turn off the isolator when leaving the boat, but have the batteries still charging, then really what you've got is a load isolator rather than a battery isolator.

 

The BSS allows for this, and it seems many boaters want the facility to do this - ie isolate only certain items instead of truly isolating the batteries.

 

It gets even more complicated when you appreciate that certain loads don't need (according to BSS) to go through the battery isolator - for example inverters. I'd say it were common sense for this to be isolatable, possibly with its own switch. And of course there is the dilemma of where to wire a combi.

Link to comment
Share on other sites

If you can turn off the isolator when leaving the boat, but have the batteries still charging, then really what you've got is a load isolator rather than a battery isolator.

Depends on whether you want to consider any isolator to be a load isolator or a battery isolator! One side is isolated from the other side.

Just add to the confusion we leave the boat with the isolator on but the empirbus master switch off. Just leaves the combi, mikuni, GSM remote control and bilge pump powered.

Link to comment
Share on other sites

Surely the answer is to have two battery isolators. One to isolate batteries from chargers, alternators, bilge pump etc., and rarely used. Then a second to isolate all switch panel distribution loads, with both fed directly from batteries. You then have the option to leave charger and bilge pump on when boat unattended, as well as completely isolating the bank if necessary.

Link to comment
Share on other sites

Snip

 

a split relay (for the starter battery when the domestics are fully charged),

 

Snip

 

Is this not the wrong way around? My Smartbank system only connects in the domestics when the engine battery is fully charged.

 

N

Link to comment
Share on other sites

Is this not the wrong way around? My Smartbank system only connects in the domestics when the engine battery is fully charged.

 

N

Debatable. Your way, if the starter battery is nearly fully charged when the engine starts, and the domestics are low, you may end up with the starter battery discharging a bit into the domestics before it finally recharges. If you charge the domestics first and bearing in mind starting an engine uses only 1 or 2 AH, it seems a better way. The starter battery can wait! Of course the relay / Smartbank doesn't connect when the batteries are fully charged does it? Surely it is when the terminal voltage reaches some value around the regulated alternator voltage at which point the batteries will still be a long way from fully charged.

 

It is also better to connect the alternator to the domestic batteries, that way not much current has to flow though the relay for not very long, as opposed to all the domestic charging current having to go through the relay for hours.

Edited by nicknorman
Link to comment
Share on other sites

I'd say for a system to favour one or the other banks upon initial charging, it should be able to accurately monitor both of those banks, to determine which one "needs" it most. For example, if your engine/start battery was almost completely depleted and your domestic bank wasn't far behind, I'd want a single alternator to charge the engine/start battery first, then when there's enough in it, to switch over to charging the domestics.

 

However if the engine/start battery is nearly fully charged and the domestics flattish, do them first then worry about the engine/start later.

 

Given the smartbank isn't actually that smart (it links to a smartgauge...which is only monitoring one bank, the domestics; and it can't send charge to only one battery - it either joins them, or not) then the strategy of charging the engine/start battery first, then linking to charge both, seems a reasonable compromise.

 

In fact, simpler systems such as a split charge relay will link the two banks merely based on the engine running (or alternator charging) irrespective of the state of charge, and there's no massive disadvantage here. An advantage is that the alternator can be connected to the domestic bank, knowing that the two banks will be linked within a few seconds of engine start, so the engine/start battery won't be left out or forgotten. A smartbank could conceivably be charging just one bank for a while, the more cautious may choose that bank to be the engine/start battery so they are denied the opportunity to make a more direct connection from the alternator to the domestic bank.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.