What size/type of relay for charging system and where to buy it

[Westerly Jetstream]

With due respect this is 2013, Vsr and split charge relays have been around for at least 20yrs, there are much better control systems for boats, a trip to Sterlings site is an eye opener.
Remember the difference between a fully charged battery and a flat one is measured not in Volts, but in decimal points of a Volt. Any device in a marine environment that has mechanical switching and contacts is going to deteriorate very quickly putting Voltage Drop into the system. We rely more and more on electronics on board some vey sophisticated, why would we use 20 yr old technology to keep those high tech systems running, I am now retired, but made my living working at boat electrics, I never ever fitted a Vsr or a a Split charge relay. There are zero drop diode systems now and battery to battery charging systems. Lots of toys.it has amazed me over the yrs with our reliance on electronics just how unimportant boat electrics, inc wiring, switching, and charging systems are to most owners. Whilst cruising I have had to go on board many boats with problems, the horror stories would fill a book.

 

[Phoenix of Hamble]

With due respect this is 2013, Vsr and split charge relays have been around for at least 20yrs, there are much better control systems for boats, a trip to Sterlings site is an eye opener.
Remember the difference between a fully charged battery and a flat one is measured not in Volts, but in decimal points of a Volt. Any device in a marine environment that has mechanical switching and contacts is going to deteriorate very quickly putting Voltage Drop into the system. We rely more and more on electronics on board some vey sophisticated, why would we use 20 yr old technology to keep those high tech systems running, I am now retired, but made my living working at boat electrics, I never ever fitted a Vsr or a a Split charge relay. There are zero drop diode systems now and battery to battery charging systems. Lots of toys.it has amazed me over the yrs with our reliance on electronics just how unimportant boat electrics, inc wiring, switching, and charging systems are to most owners. Whilst cruising I have had to go on board many boats with problems, the horror stories would fill a book.

+1

A smart regulator is not a huge outlay, and makes the management of charge very simple.

Combine with a sensible switch arrangement and you can make maximising the charging regime, and avoiding discharging the wrong battery, very straightforward.

 

[pvb]

Combine with a sensible switch arrangement and you can make maximising the charging regime, and avoiding discharging the wrong battery, very straightforward.

But, even better, you can make it automatic!

 

[pvb]

Any device in a marine environment that has mechanical switching and contacts is going to deteriorate very quickly putting Voltage Drop into the system.

VSRs don't introduce a voltage drop.

 

[sailorman]

So Victron are less reliable than the Hallowed Mr Chas Sterling, i very much doubt it



UOTE=Westerly Jetstream;4035138]With due respect this is 2013, Vsr and split charge relays have been around for at least 20yrs, there are much better control systems for boats, a trip to Sterlings site is an eye opener.
Remember the difference between a fully charged battery and a flat one is measured not in Volts, but in decimal points of a Volt. Any device in a marine environment that has mechanical switching and contacts is going to deteriorate very quickly putting Voltage Drop into the system. We rely more and more on electronics on board some vey sophisticated, why would we use 20 yr old technology to keep those high tech systems running, I am now retired, but made my living working at boat electrics, I never ever fitted a Vsr or a a Split charge relay. There are zero drop diode systems now and battery to battery charging systems. Lots of toys.it has amazed me over the yrs with our reliance on electronics just how unimportant boat electrics, inc wiring, switching, and charging systems are to most owners. Whilst cruising I have had to go on board many boats with problems, the horror stories would fill a book.[/QUOTE]

 

[Westerly Jetstream]

With due respect you are right BUT only when new. If you read my post fully I stated that after time when exposed in a marine environment any mechanical ( and were not talking digital here,) will in time with arcing and corrosion, create VD across its contacts.
Oh and i made no comment about any other supplier of expensive kit just mentioned one that the man on the pontoon might have heard off. There are lots of quality digital charging solutions out there. Just don't limit yourself to old world mechanical relay systems.
I'll go crawl back under my rock now.

 

[William_H]

I have some Hella sealed high current relays floating around here. I would still choose one of them over electronic switches. Yes the electronics are reliable but not necessarily the PC boards they are built on.
A relay that connects domestic batteries for charging with ignition switch turned on will of course also parallel all the batteries for starting. This may expose the relay to high currents and could also mask a bad engine start battery. So the relay should be connected to oil pressure switch, alternator aux output or simplest set up to detect charge voltage (a VSR relay)
To the OP I would say get the highest current relay available for reliability and so that it can be used as emergency engine start connection and get one that is sealed. good luck olewill

 

[Gerry]

Hi folks

Thanks to all for the superb input. Let me tell you more.

First, the boat is a twenty year old Bowman 40 whose wiring is an unbelievable rats nest, incompletely documented and with a variety of problems:

1) When running, voltage at the alternator is 14.2v but 13.65v at the service batteries and only 13.4v at the cranking battery.
2) The engine warning light is glowing dull read all the time when running
3) Voltages are down to about 10v on the engine control panel and the engine stop solenoid doesn’t work (though does with 12v applied to it)
4) The Perkins M50 engine wiring harness (automotive grade, that is no tinning of course) is coroded in places.
5) The wiring diagram shows a TWC Adverc installed and the alternator B+ vanishes into a glued-together white plastic box with a non-functioning ampmeter on one side. I hesitate to break it open. I don’t see a sensing lead from the regulator so I doubt it has been working properly for many years.
6) There is a KISS windgenerator that works well and seems to be wired through a splitter diode.
7) The 1-2-both switch merely connects up fore and aft service batteries.
8) The volt and ammeter on the services panel is blown.
9) The Victron Ah meter is unreliable; its buttons no longer work.

Having been hit by lightning twice, I take very much to heart John Payne’s advice in the introduction of his Marine Electrical and Electronics Bible: “Successful and trouble free cruising depends on simplicity”.

So my plan is to rebuild the wiring from the batteries up, crimping not soldering the terminals. And I was wondering what is the next step up from a 1-2-both switch. The Sterling solution at £330+ VAT is more than I want to pay, and is hardly simple..

I am a little confused here. Would someone help me out on VSR (what does this stand for?) versus split charge relay (SCR?) and the mechanical versus electronic pros and cons (would the electronics be more vulnerable to lightning?). Also where can I learn more about the “zero drop diode systems”. My criteria are: 1) simplicity (I need to fully understand what is going on), 2) reliability, 3) low cost.

Kind regards

Gerry

 

[oldfatgit]

Hi folks

Having been hit by lightning twice.

Lucky it was you and not your boat otherwise it might have played merry hell with your boat electronics! Seriously though, I look forward to any further posts on this subject but the reality is that there are so many ways to skin this particular cat that your overriding principle of KISS seems sound to me. Like you I am groping around with a similar problem, albeit on a narrow boat. If I were inclined to pay Sterling anything it would be for a battery maintainer which will top up the starter battery from the domestic ones. This is because the engine is a really good starter and hardly drains the engine start battery, and, of course, in a narrow boat there are no sails to use leading to short engine runs. On the proper boat (the narrowboat is a project (don't ask)), moored really close to the harbour entrance, I routinely sail with engine running for a while just to top up the start battery. Again, blessed with a really good starting engine so no problems so far. The proper boat has an elderly Adverc intelligent charge system and a Paris Rhone alternator which has a built in split charge diode. So the Adverc detects the voltage on the domestic bank and bumps up the voltage to compensate for the losses across the diode. Thing is it is all solid sate and works fine. On the Narrowboat I have a sterling intelligent charger which does much the same. I will use this in combination with some form of simple battery to battery charging circuit to top up engine start and am thinking of something very simple; probably as described in the link posted by alahol2 above. As far as I can see, the only draw back of a electro-mechanical system are as described by Westerly Jetstream but there is no voltage drop in the relay which is a definite plus. If something goes wrong then I'd be able to start on domestic batteries by closing the 3rd switch. The snag is how to get charge when plugged into the national grid into the start battery, that is where a VSR or similar instead of the relay connected into the ignition comes into its own. The point is, and somewhat counter intuitively, I see advantages in charging the more heavily used domestic batteries as the first priority relying on the good engine starting and long running to ensure that the engine start is kept in good condition.

If anybody has managed to read my rather turgid post, one final question; where does one buy a good quality VSR? I have used the Google thing but cannot decide.

 

[nigelmercier]

I was wondering what is the next step up from a 1-2-both switch...

A relay to parallel the batteries with the ignition circuit, as you suggest. However, it needs to have a time delay or it would be like switching to "both" before starting. You can get time delay relays for about £5 on eBay, or search for a circuit. You want one that will hold off the main relay for a few minutes.

 

[Westerly Jetstream]

Any decent Marine mains charger will have outputs for up to three different battery banks all isolated from each other. That will look after Starting, Thruster, and Domestics independently without any other fancy pieces of expensive kit. Failing that a multiple output zero drop diode pack will do same thing for a single output charger. Just remember to use heavy enough cable and quality HD crimps not those cheap and nasty red, blue, yellow automotive ****. To the OP you've got a severe case of VD mucker do not add any more kit to mask the problem get rid of it first.

 

[pvb]

So my plan is to rebuild the wiring from the batteries up, crimping not soldering the terminals. And I was wondering what is the next step up from a 1-2-both switch. The Sterling solution at £330+ VAT is more than I want to pay, and is hardly simple..

I am a little confused here. Would someone help me out on VSR (what does this stand for?) versus split charge relay (SCR?) and the mechanical versus electronic pros and cons (would the electronics be more vulnerable to lightning?). Also where can I learn more about the “zero drop diode systems”. My criteria are: 1) simplicity (I need to fully understand what is going on), 2) reliability, 3) low cost.

Your plan to start from scratch is a good one. You'll end up knowing exactly how things are wired, and knowing that it's been done properly.

VSR stands for Voltage Sensitive Relay. This is a relay which connects 2 batteries, or banks of batteries. It monitors the battery voltage and closes when the voltage reaches a certain level, connecting the batteries. Most often, it's used to connect the engine start battery to the domestic batteries. When the engine is off, the relay is open - this means that the start battery is isolated and that domestic loads can't run it down. When the engine starts, the alternator starts to charge the engine battery, which rises in voltage. When it reaches about 13.5v, the relay operates, closing the contacts and linking the domestic batteries into the charging circuit. When the engine is turned off, the battery voltage will drop back to its normal level and the relay switches off, again isolating the start battery.

The advantage of the VSR over most split charge relays is that it allows the start battery to be substantially recharged before it connects the domestic batteries in to the circuit. And, being fully automatic, there's nothing you need to do or remember.

Another way of separating the start and domestic batteries is to use a diode splitter. These let the current flow in to the batteries, but not backwards from a charged battery into a discharged battery. Most of them result in a drop in charging voltage, usually proportional to the charging current, but potentially as high as 0.7v which is enough to seriously reduce the charging efficiency. So-called "smart" regulators (your Adverc is one) compensate for this voltage drop by increasing the output voltage of the alternator. As an alternative, more sophisticated "zero drop" diodes have been developed which don't introduce a voltage drop, needless to say they're more expensive.

Some people believe that diodes are more reliable than relays. I'd say both can fail; indeed I've had a diode splitter fail, but not a VSR. Modern VSRs are ruggedly built to withstand the damp atmosphere of boat use and are very reliable.

In terms of simplicity, I favour a system with a VSR and 2 simple on/off switches, one for the engine, one for the domestic batteries. When you arrive at the boat, switch both on, use the boat and, when you leave it switch both off. There's no need to fiddle with 1-2-Both switches. There's nothing you can set wrongly. There's no chance of inadvertently running the start battery flat and finding yourself with a problem, because the VSR will take care of charging automatically and will protect the integrity of your start battery.

As for lightning, it can damage any electrics on a boat. However, if you have been struck twice, I'd reckon the chances of a repeat performance are pretty slim!

Here's a quick diagram showing how to wire a simple system. You'll see there's a third on/off switch which can be used to start the engine from the domestic batteries in the rare event of a start battery failure. This is optional, but many people like to fit one. You'll note that fuses are included, as close to the battery terminals as possible, to protect the wiring from accidental shorts leading to a fire.

 

[Westerly Jetstream]

When the engine starts, the alternator starts to charge the engine battery, which rises in voltage. When it reaches about 13.5v, the relay operates, closing the contacts and linking the domestic batteries into the charging circuit. When the engine is turned off, the battery voltage will drop back to its normal level and the relay switches off, again isolating the start battery.

The advantage of the VSR over most split charge relays is that it allows the start battery to be substantially recharged before it connects the domestic batteries in to the circuit. And, being fully automatic, there's nothing you need to do or remember.

With due respect as soon as alternator starts charging the output voltage will be well above 13.5 and the VSR will close there is no advantage to the start battery in terms of longer recovery time before domestics are connected. Not withstanding that for simplicity and automatic control a quality digital VSR can make things very simple I' still prefer a battery to battery charger. But each to his own. Certainly the OP needs to go back to first principles get his battery interconnects and charging sorted then run two quality cables to a busbar system, and use some decent switch kit like Blue Sea. I've rewired dozens of boats most common problems wrong size wire, bad connections,**** switch gear.

 

[ghostlymoron]

With due respect as soon as alternator starts charging the output voltage will be well above 13.5 and the VSR will close there is no advantage to the start battery in terms of longer recovery time before domestics are connected. Not withstanding that for simplicity and automatic control a quality digital VSR can make things very simple I' still prefer a battery to battery charger. But each to his own. Certainly the OP needs to go back to first principles get his battery interconnects and charging sorted then run two quality cables to a busbar system, and use some decent switch kit like Blue Sea. I've rewired dozens of boats most common problems wrong size wire, bad connections,**** switch gear.

I've used a VSR and it doesn't switch over immediately the engine starts. About 5mins usually.

 

[Westerly Jetstream]

I've used a VSR and it doesn't switch over immediately the engine starts. About 5mins usually.

And you seriously think 5 mins is going to recover your engine battery most boats nowadays have advanced regulator controllers which can raise the output of the alternator to nearly 15 volts. Also batteries will not charge properly unless they ate seeing about 14.3 V at their terminals. Certainly any boat I wire will see at least 14.3 at batteries as soon as alternator springs to life. If they don't theres serious VD somewhere, and connections need remade or wire sizes increased. If a jobs worth doing it's worth doing well. I've turned away owners who just wanted a cheap fix,boats are expensive and cash scrimped on electrics is plain stupid, when your out in open sea in a six or a seven and the electrics start to go wrong that is not the time to be having second thoughts. I know I come on strong BUT now well into retirement, and having been sailing since I was seven, i've seen too many horror stories to catalogue. Boat electrics are ever bit as important as standing and running rigging, or sails. Most owners ignore it or want to spend nothing on it. RANT over

 

[pvb]

And you seriously think 5 mins is going to recover your engine battery ...

Starting most engines uses very little power, around 1Ah or less typically. 5 minutes charging should certainly top up the starter battery.

Certainly any boat I wire will see at least 14.3 at batteries as soon as alternator springs to life. If they don't theres serious VD somewhere, and connections need remade or wire sizes increased.

That surely depends on how discharged the batteries are? With heavily discharged batteries, it can take some time for the charge voltage at the batteries to reach 14+.

 

[nigelmercier]

Starting most engines uses very little power, around 1Ah or less typically. 5 minutes charging should certainly top up the starter battery... With heavily discharged batteries, it can take some time for the charge voltage at the batteries to reach 14+.

Beat me to it.

And because the starter battery is always near full, I have my VSR connected so the starter battery is switched.

 

[wotayottie]

So, let's assume the domestic batteries have been run flat. Go to try to start the engine, as soon as key is turned the engine battery is parallelled to the flat domestics, voltage collapses, engine won't start. What next?

You would have to be a complete idiot to allow the domestics to go completely flat, and if you were that idiot as likely as not you would have left the rotary switch on both and flattened the engine starter battery too. So you would in fact have been worse off.

If you were the said idiot you might think about disconnecting the domestics whilst you started up. It doesnt affect the starting of the engine unless you stop and stand after switching on and let the domestics flatten the engine start battery. If the domestics are half charged at say 12.2 volts, the starter circuit will drop to maybe 10v when the starter is going anyway and the engine will start

I had the relay system on my boat for 7 years without an issue.

 

[halcyon]

With due respect as soon as alternator starts charging the output voltage will be well above 13.5 and the VSR will close there is no advantage to the start battery in terms of longer recovery time before domestics are connected. .

Depends on VSR settings, I only set 13.5 - 13.6 volt switching originally as alternator regulation was only 13.6 volt back in 1980.

Today I would go with 13.8 - 14.0 volt, still switches quickly as engine battery should normally be up at that capacity, plus the engine battery charges up at the same time as the service bank anyway.

VSR's has the advantage of bi directional operation, be it charging or start from service bank, that solid state or switch mode do not.

Brian

 

[ghostlymoron]

And you seriously think 5 mins is going to recover your engine battery most boats nowadays have advanced regulator controllers which can raise the output of the alternator to nearly 15 volts. RANT over

Yes I agree with pvb and nigel, the power taken to start the engine is very small (high current but short duration) assuming the engine doesn't require prolonged cranking.
I don't agree that most boats have advanced regulator controllers. It may be true of new boats (but I suspect it isn't) but I have yet to sail on one. The reason is that most boats alternator/regulator cope perfectly well with the power demands on them, even though the system was originally designed for automobiles. It's only when owners overload their boats with electric hungry gadgets that they need to squeeze the last joule of power from their system that the simple system isn't adequate.