Regarding Split Charge Diodes

[The Gravy Boater]

My boat has a three way Split Charge Diode to service my Starter, Domestic and Bowthruster batteries. Apparently the output that was going to my starter battery is now dead, so as a temporary measure this has been switched to the bowthruster while I source a replacement.  I've checked and the other batteries are still getting good charge.  My domestics are also serviced by a large solar array and I also have a genny so I have no immediate power concerns.

 

The alternator is an original 90 or 95 amp (depending on who you talk to) Vetus brand.  The diode is unmarked but RCR think it is a 100 amp Stirling.  There is also a Stirling Alternator Regulator.  The alternator is fused at 150 amps, which seemed odd to me... but maybe someone can explain if this is usual.      

 

RCR have suggested I replace the three way Split Charge Diode with a 150 or 200amp version and mount it directly to the steel for better heat transfer (the original was on wood).

 

This setup ran without issue for 2.5 years, so what are the most likely causes of the burnout?  Throughout that time I have used my 2.1kw Stirling Inverter/Charger while the engine has been on with varying loads... certainly much higher loads in the past than I have done lately.  So I can't think of a specific event that might have put stress on the setup.

 

Regarding a replacement... everyone says Victron or Mastervolt but what is adequate and above all safe in this instance?

 

I know there is a voltage drop associated with diodes.  Are the type that claim to overcome this legit?

 

https://sterling-power.com/collections/relays/products/volt-drop-alternator-splitting-system-pro-split-r?variant=882764291

 

Thanks for reading and all advice welcome.

[Tracy D'arth]

I would dump the diodes and use a VSR or two.

[The Gravy Boater]

29 minutes ago, Tracy D'arth said:

I would dump the diodes and use a VSR or two.

I'll goggle it.  Not yet seen that is an option for a three way battery setup with one alternator.  Sounds like witchcraft.  Burn the witch 🤨.  Still trying to read up on this stuff but I just need a simple, affordable and safe bulletproof replacement.

Edited November 3, 2022 by The Gravy Boater

[Jen-in-Wellies]

Two voltage sensitive relays. Problem solved. Simple, affordable and bullet resistant. None of the voltage drop you got over split charge diodes.

 

11 minutes ago, The Gravy Boater said:

Burn the witch

Has possibly the best music video of all time.

 

 

[The Gravy Boater]

2 minutes ago, Jen-in-Wellies said:

Two voltage sensitive relays. Problem solved. Simple, affordable and bullet resistant. None of the voltage drop you got over split charge diodes.

 

Well, that's two votes for that I guess... also, that's some messed up Camberwick Green 🙂

 

 

[Jen-in-Wellies]

1 minute ago, The Gravy Boater said:

Well, that's two votes for that I guess... also, that's some messed up Camberwick Green 🙂

Gordon Murray, the creator of Camberwick Green etc was not happy about the video at all.

[Tony Brooks]

And another vote but a degree of rewiring will be needed. Make sure the alternator feeds the domestic bank the VSRs takes the feed from the domestic battery to feed the other banks.

[The Gravy Boater]

16 minutes ago, Tony Brooks said:

And another vote but a degree of rewiring will be needed. Make sure the alternator feeds the domestic bank the VSRs takes the feed from the domestic battery to feed the other banks.

A-ha... now I get it.  The alternator just feeds the domestics... when they are full the domestics feed the Starter... when the Starter is full it feeds the Bowthruster?  That's also a solar dump, right?  Because the solar (connected to the domestics) wouldn't normally feed anything to the other batteries.

Edited November 3, 2022 by The Gravy Boater

[Jen-in-Wellies]

12 minutes ago, The Gravy Boater said:

A-ha... now I get it.  The alternator just feeds the domestics... when that's full it the domestics feed the Starter... when that's full it feeds the Bowthruster? That's also a solar dump, right?

Not quite. When the voltage to the domestic bank exceeds a certain value, they will connect to the engine and bow thruster batts too. This voltage is greater than that on a fully charged lead acid, so they only connect the batteries together when there is a charging voltage going in from the alternator, or the solar controller. All will be charged at the same time, even if the domestics are low. When there is no input from the alternator, or solar, then the engine and bow thruster batts are disconnected and protected from being discharged by domestic use.

Edited November 3, 2022 by Jen-in-Wellies

[The Gravy Boater]

1 minute ago, Jen-in-Wellies said:

Not quite. When the voltage to the domestic bank exceeds a certain value, they will connect to the engine and bow thruster batts too. This voltage is greater than that on a fully charged lead acid, so they only connect the batteries together when there is a charging voltage going in from the alternator. All will be charged at the same time, even if the domestics are low.

Thanks.  How does that work with the domestics also having input from a solar array?  And also voltage drop from draw on the domestics?

[GUMPY]

With VSR solar will charge all three banks.

When the voltage on the domestics drops it Will disconnect the other banks thus leaving them charged

[Jen-in-Wellies]

For example, https://www.12voltplanet.co.uk/voltage-sensitive-relay-12v-140a.html

I've installed a couple of these for friends. Connects the batteries together when the voltage on one of the batteries reaches, or exceeds 13.7V. Disconnects them when the voltage drops below 12.8V (fully charged batt with no load, or input). That way, the batteries are only connected when there is a charging source, like an alternator, or solar. This particular example is bidirectional. Others may not be. Not that that matters, if all the charging sources are going to the house batteries.

[The Gravy Boater]

15 minutes ago, Jen-in-Wellies said:

For example, https://www.12voltplanet.co.uk/voltage-sensitive-relay-12v-140a.html

I've installed a couple of these for friends. Connects the batteries together when the voltage on one of the batteries reaches, or exceeds 13.7V. Disconnects them when the voltage drops below 12.8V (fully charged batt with no load, or input). That way, the batteries are only connected when there is a charging source, like an alternator, or solar. This particular example is bidirectional. Others may not be. Not that that matters, if all the charging sources are going to the house batteries.

I've read a couple of things in passing about 'battery feedback' when using relays and that this is potentially hazardous? Is this the bullshit?

For reference... my domestic battery bank is 3x180ah sealed lead acid... starter is 90ah... bowthruster was 110ah as far as I can remember.

[Jen-in-Wellies]

2 minutes ago, The Gravy Boater said:

I've read a couple of things in passing about 'battery feedback' when using relays and that this is potentially hazardous? Is this the bullshit?

Dunno. Have you got links to examples?

[The Gravy Boater]

1 minute ago, Jen-in-Wellies said:

Dunno. Have you got links to examples?

Will do upon the morrow but got to shoot off for now.  Thanks for the replies.

[Tony Brooks]

13 minutes ago, The Gravy Boater said:

I've read a couple of things in passing about 'battery feedback' when using relays and that this is potentially hazardous? Is this the bullshit?

For reference... my domestic battery bank is 3x180ah sealed lead acid... starter is 90ah... bowthruster was 110ah as far as I can remember.

 

What will happen with a relay (or a solenoid) is when the operating COIL is turned off the near instant breakdown of the magnetic field will induce a high voltage in the coil windings. If you happen to be in contact with the negative and the relevant coil terminal you will get a minor electric shock. On a straight electrical system this really is not relevant, but as soon as electronics come into it that voltage can do damage so steps have to be taken to quench the voltage surge. This is usually done by a diode in parallel with the coil. It is almost certain any VSR will be so protected.

 

Ordinary car type four or five terminal relays come with or without diodes to suit the application. If you connected the coil circuit on one with a diode you burn the diode out but the relay normally still operates.

 

This has nothing to do with the relay contacts which is a different circuit to the relay coil.

 

I think that whatever source told you that does not understand the subject very well, I would say it is a load of bull.

 

 

[Tracy D'arth]

5 minutes ago, Tony Brooks said:

 

What will happen with a relay (or a solenoid) is when the operating COIL is turned off the near instant breakdown of the magnetic field will induce a high voltage in the coil windings. If you happen to be in contact with the negative and the relevant coil terminal you will get a minor electric shock. On a straight electrical system this really is not relevant, but as soon as electronics come into it that voltage can do damage so steps have to be taken to quench the voltage surge. This is usually done by a diode in parallel with the coil. It is almost certain any VSR will be so protected.

 

Ordinary car type four or five terminal relays come with or without diodes to suit the application. If you connected the coil circuit on one with a diode you burn the diode out but the relay normally still operates.

 

This has nothing to do with the relay contacts which is a different circuit to the relay coil.

 

I think that whatever source told you that does not understand the subject very well, I would say it is a load of bull.

 

 

There is a slim chance of a shock caused by the back emf of the collapsing magnetic field in the coil but not worth worrying about. He may be referring to the relay connecting a fully charged battery to a really flat one causing a heavy current to flow through the relay contacts exceeding the rating.

In all my years with boats with simple spit charge relays it has never been a problem providing the relay is up to the job and not some toy designed to switch a light load. 

[Tony Brooks]

Just now, Tracy D'arth said:

There is a slim chance of a shock caused by the back emf of the collapsing magnetic field in the coil but not worth worrying about. He may be referring to the relay connecting a fully charged battery to a really flat one causing a heavy current to flow through the relay contacts exceeding the rating.

In all my years with boats with simple spit charge relays it has never been a problem providing the relay is up to the job and not some toy designed to switch a light load. 

 

And what Tracy is describing is why I said the alternator output should be connected direct to the domestic bank. The engine battery is always all but fully charged until it goes faulty. It is the bow thruster load that gives me a little concern in case it exceeds the relay rating. When operating it will draw current from the alternator AND the domestic battery if the demand is high enough I think I might think about finding a way to open the relay contact when the bow thruster is operating if the load is close to or above the relay contact rating. It could be done by open circuiting the VSR thin negative wire using another relay.

[The Gravy Boater]

Found a moment to look for it... I was reading the blurb at the bottom of this page about the various charging options from alternator:

 

https://sterling-power.com/products/split-charge-diodes-70-200a-2-3-outputs

 

Probably unrelated to what you are discussing or sales blurb... I've just been injesting this stuff all day. 

 

"2) Split charge relay. This system is both dated and extremely dangerous, unless understood and the correct relay used for the correct job, ie current limiting relays may be required for safety reasons. The good side is, that it is easy to fit and requires no alterations to the standard engine system, but, it merely connects the domestic battery bank to the engine battery via a relay, which is energised when the engine starts.
 The bad side (and the very dangerous side) is that a relay is prone to over loading. Say, for example, you have a 70A relay on your system and a 55A alternator, all seems great, but if you fit a 1500W inverter which can draw 150A and one morning the domestic battery is flat. So, you start the engine to charge the domestic batteries, the 70A split charger relay will come online to enable the alternator to charge the domestic battery bank. Then you load your inverter to 150A, the 150A will not be drawn from the domestic battery because it is flat but can be drawn from the engine battery (which is full). That means you will draw 150A up the split charge cable and through the 70A relay. If you are lucky you will destroy the relay, if you are not so lucky then you will set fire to the cross over cables, hence the dangerous aspect, A Sterling Currint limiting relay prevents this problem. (see later) The system must be suitable for the purpose for which it is installed and this is clearly not. "

[GUMPY]

54 minutes ago, The Gravy Boater said:

I've read a couple of things in passing about 'battery feedback' when using relays and that this is potentially hazardous? Is this the bullshit?

Possibly refering to back EMF which is generated across the coil when the relay opens. Not something to worry about.

[Tony Brooks]

So basically marketing bull shine and half-truths.

 

Yes, the engine battery will be fully charged at about 12.7 volts. The domestic bank will drop voltage when the inverter load is applied but with the alternator running at say 13.8 volts (because the inverter load provided for by the alternator will drop the alternator output voltage) there is no way the engine battery will "back feed" into the domestic bank through the relay.

 

140 amp VRS  (Cargo) about £50, Sterling zero volt drop diode how much?

Edited November 3, 2022 by Tony Brooks

[The Gravy Boater]

23 minutes ago, Tracy D'arth said:

There is a slim chance of a shock caused by the back emf of the collapsing magnetic field in the coil but not worth worrying about. He may be referring to the relay connecting a fully charged battery to a really flat one causing a heavy current to flow through the relay contacts exceeding the rating.

In all my years with boats with simple spit charge relays it has never been a problem providing the relay is up to the job and not some toy designed to switch a light load. 

Ha!  Yes no relays out of a Christmas Cracker please... sounds like they were bigging up risk for sales purposes.

[GUMPY]

11 minutes ago, The Gravy Boater said:

Found a moment to look for it... I was reading the blurb at the bottom of this page about the various charging options from alternator:

 

https://sterling-power.com/products/split-charge-diodes-70-200a-2-3-outputs

 

Probably unrelated to what you are discussing or sales blurb... I've just been injesting this stuff all day. 

 

"2) Split charge relay. This system is both dated and extremely dangerous, unless understood and the correct relay used for the correct job, ie current limiting relays may be required for safety reasons. The good side is, that it is easy to fit and requires no alterations to the standard engine system, but, it merely connects the domestic battery bank to the engine battery via a relay, which is energised when the engine starts.
 The bad side (and the very dangerous side) is that a relay is prone to over loading. Say, for example, you have a 70A relay on your system and a 55A alternator, all seems great, but if you fit a 1500W inverter which can draw 150A and one morning the domestic battery is flat. So, you start the engine to charge the domestic batteries, the 70A split charger relay will come online to enable the alternator to charge the domestic battery bank. Then you load your inverter to 150A, the 150A will not be drawn from the domestic battery because it is flat but can be drawn from the engine battery (which is full). That means you will draw 150A up the split charge cable and through the 70A relay. If you are lucky you will destroy the relay, if you are not so lucky then you will set fire to the cross over cables, hence the dangerous aspect, A Sterling Currint limiting relay prevents this problem. (see later) The system must be suitable for the purpose for which it is installed and this is clearly not. "

Sterling sales pitch🥱

Nothing to worry about if the alternator is connected to the domestic batteries as it can never happen.

[Tony Brooks]

If the described consequences worry you then use an Albright contactor controlled by a VSR.

[The Gravy Boater]

6 minutes ago, Tony Brooks said:

140 amp VRS  (Cargo) about £50, Sterling zero volt drop diode how much?

£160 odd for a three way 120 amp.