VSR or Split Charge Diode?

[adwuk]

Some advice from the collective please.

I am replacing the alternator on our boat and will also take the opportunity to install an alternator regulator. At the moment I have two isolator switches for engine and services as well as an emergency join switch, and realise that I can simply use these to achieve charging of both banks, but... I would like it to be automatic. I know I need a VSR or split charge diode, but which one?

The alternator is 70A, and there are 1 x 90Ah engine and 2 x 115Ah service batteries.

Thanks in advance.

 

[PaulRainbow]

Some advice from the collective please.

I am replacing the alternator on our boat and will also take the opportunity to install an alternator regulator. At the moment I have two isolator switches for engine and services as well as an emergency join switch, and realise that I can simply use these to achieve charging of both banks, but... I would like it to be automatic. I know I need a VSR or split charge diode, but which one?

The alternator is 70A, and there are 1 x 90Ah engine and 2 x 115Ah service batteries.

Thanks in advance.

I would fit a Victron Cyrix, in your case.

For instance (double check for best price) https://www.batterymegastore.co.uk/...s-combiners/victron-energy-cyr010120011r.html

 

[ghostlymoron]

I'd go for the relay as no soldering required. I've heard that alternator regulators are no longer necessary with a modern alternator but stand by to be corrected.

 

[pvb]

I am replacing the alternator on our boat and will also take the opportunity to install an alternator regulator.

If you are fitting a modern alternator, you should find that it is already outputting around 14.4v so you would have a limited benefit from an add-on regulator.

 

[peteK]

If you are fitting a modern alternator, you should find that it is already outputting around 14.4v so you would have a limited benefit from an add-on regulator.

+1

 

[Keith-i]

MOSFET splitter wins over VSR or diodes in my opinion. No voltage loss, 'intelligent' and easy to wire in. Can handle up to 3 battery banks with right model. Most of the major manufacturers make one e.g. Victron Argo FET.

 

[halcyon]

MOSFET splitter wins over VSR or diodes in my opinion. No voltage loss, 'intelligent' and easy to wire in. Can handle up to 3 battery banks with right model. Most of the major manufacturers make one e.g. Victron Argo FET.

Check small print, MOSET's have a resistance, larger the current, larger the volt drop, can be twice that of a VSR, Intelligent ? easy to wire ? means changing alternator cable and 3 cables, VSR only only needs 2.

They cannot be used for emergency battery linking, failure of split charge module can mean no charge to engine battery, or service battery.

Also for ref you can get a VSR for battery banks.

Just for information.

Brian

 

[adwuk]

If you are fitting a modern alternator, you should find that it is already outputting around 14.4v so you would have a limited benefit from an add-on regulator.

Ah - didn't realise that! The one I have ordered is a Prestolite 70A alternator (https://www.parts4engines.com/perkins-4-108-alternator-12v-70-amp/). I can't find any details that specify the output voltage, so wondering if I should cancel the order for the alternator regulator until the alternator has arrived?

 

[PaulRainbow]

Ah - didn't realise that! The one I have ordered is a Prestolite 70A alternator (https://www.parts4engines.com/perkins-4-108-alternator-12v-70-amp/). I can't find any details that specify the output voltage, so wondering if I should cancel the order for the alternator regulator until the alternator has arrived?

I doubt an external regulator will be any benefit, i'd cancel it.

 

[adwuk]

I doubt an external regulator will be any benefit, i'd cancel it.

Ta - will call them in the morning.

It seems that most support is for a VSR. Which surprised me given Mr Sterlings view of them, but I do recognise that he is trying to sell his wares.

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.

 

[rszemeti]

If you are fitting a modern alternator, you should find that it is already outputting around 14.4v so you would have a limited benefit from an add-on regulator.

That depends entirely on the regulator you are fitting ... some are better than others. Most will monitor battery temperature, the better ones will also monitor alternator temperature. They will also provide a "balancing charge", "bulk acceptance", "charge completion" and "float" stages, adjust their trigger voltages and target voltages depending on battery temperature, have selectable charge profiles for AGM, standard, gel, EFB and possibly LiFePO4 etc ... not all are created equal.

 

[halcyon]

That depends entirely on the regulator you are fitting ... some are better than others. Most will monitor battery temperature, the better ones will also monitor alternator temperature. They will also provide a "balancing charge", "bulk acceptance", "charge completion" and "float" stages, adjust their trigger voltages and target voltages depending on battery temperature, have selectable charge profiles for AGM, standard, gel, EFB and possibly LiFePO4 etc ... not all are created equal.

One consideration is how long do you run your engine/engines for? long enough to gain benefit from all that control options ?

Brian

 

[adwuk]

One consideration is how long do you run your engine/engines for? long enough to gain benefit from all that control options ?

Most of the time we run the engine to get out of the harbour and hoist the sails. I'm guessing that there is no value in advanced functions for this case where the engine is on for around 30 minutes max. However, last year we did motor round the MoK - no wind - which was around 16 hours. We had instruments/autopilot/nav lights/USB phones chargers etc on while we did that. Would an advanced alternator regulator pay for these longer runs?

 

[pvb]

That depends entirely on the regulator you are fitting ... some are better than others. Most will monitor battery temperature, the better ones will also monitor alternator temperature. They will also provide a "balancing charge", "bulk acceptance", "charge completion" and "float" stages, adjust their trigger voltages and target voltages depending on battery temperature, have selectable charge profiles for AGM, standard, gel, EFB and possibly LiFePO4 etc ... not all are created equal.

The commonly fitted Sterling add-on regulator will only achieve multi-stage charging if the internal regulator is completely disabled, which few people do. The better quality regulators (Balmar etc) only work as pure external regulators and are expensive - starting at around £300 - so it's unlikely the OP will be considering one of those for his 70A alternator.

 

[adwuk]

The better quality regulators (Balmar etc) only work as pure external regulators and are expensive - starting at around £300 - so it's unlikely the OP will be considering one of those for his 70A alternator.

Nope - you are right - I wasn't considering one of those

 

[xeitosaphil]

To the OP
I did what you are in the process of doing some time ago, with a 90amp Prestolight and 310a domestic bank and separate Red Flash engine start battery. Isolators to both banks and a combiner for domestic start if needed.

I fitted a Sterling Bi directional VSR to charge both banks automatically and also linked the solar panel to the domestic bank as a additional means of charging.
I also have two mains intelligent charges one being a M300 and a smaller one for the engine, both if needed but rarely used as the solar keeps both battery banks at 100% even May to Sept with the Danfos F/F working 24/7.

VSR definitely for me. IMHO - next to nearly no significant voltage loss.

 

[neil1967]

I've been very happy with the sterling pro-splitter: https://sterling-power.com/products/volt-drop-alternator-splitting-system-pro-split-r . Yes it is expensive, but it is fit and forget and seems to do what it says on the label.

 

[lw395]

Perhaps the most technically correct solution is a B2B charger to float charge the engine battery.
This avoids overcharging the engine battery, which has much less drain on it than the house battery.
An emergency starting link covers the possibility of the engine battery failing. But kept isolated and properly float charged, it's likely to last over ten years.

 

[GHA]

. We had instruments/autopilot/nav lights/USB phones chargers etc on while we did that. Would an advanced alternator regulator pay for these longer runs?

Probably not, maybe a little detrimental to the batts sitting at a higher voltage for that length of time but maybe so slight as to be impossible to measure. If anyone here would know it would be plevier.

 

[halcyon]

Most of the time we run the engine to get out of the harbour and hoist the sails. I'm guessing that there is no value in advanced functions for this case where the engine is on for around 30 minutes max. However, last year we did motor round the MoK - no wind - which was around 16 hours. We had instruments/autopilot/nav lights/USB phones chargers etc on while we did that. Would an advanced alternator regulator pay for these longer runs?

If you had to drive your car for a long distance with a standard alternator would you worry ? For any years boaters have done long engine runs with standard alternators without a thought, but i you have the budget for one it will do no damage, just another thing to go wrong.

Brian