Replacing VP Split Diode with Sterlings Pro Splitter or Smart Bank

[KevinT1]

I need to replace the fitted Volvo Penta Split Diode and I'm looking at the Sterling Pro Splitter or Smart Bank / Smart Gauge - so would appreciate the forums view on which way to go

The advantage of the Sterling Pro Splitter at £235 is that it manages all 3 battery banks and looks like it is the more capable, but I will need to buy an additional Battery meter.
http://sterling-power.com/products/...plitting-system-pro-split-r?variant=882765499

The advantage of the Smart Bank / Smart Gauge at £240 is that it gives me both Splitter and Battery Gauge / Meter for the same price, but is it's functionality as good as the Sterling ?
http://www.smartgauge.co.uk/products.html


I need to replace the Split Diode as we are loosing 0.5 volt across them and thus the house batteries are not getting fully charged, plus the fitting of a bowthruster + battery means I have a mixed system now with a cheap VSR and I need to sort it out

I want to replace the standard Battery meter as the analogue VDO fitted as standard is inaccurate, not because it's analogue but because of all the losses involved - we did some voltage tests and found that when everything was switched on ( all filament bulb nav lights + fridge ) and with the batteries on charge then 13.6 volts at the batteries / charger was 13.06 at the Battery Meter and 12.44 at the Fridge

thoughts and experiences please

Kevin

 

[lw395]

Spending £20 on cable to reduce the volt drop to the fridge might be a better priority?

 

[KevinT1]

Spending £20 on cable to reduce the volt drop to the fridge might be a better priority?

Good point - had investigated that - but the problem is multiple points of contact and cables,
56mV Battery to Main Breaker
170mV Across the Main Breaker
70mV from the breaker through to the Main Fuses
180 mV across the fuse
etc

and then the same on the negative side

Short of replacing all of the Cabling and Master switches - but that will not remove the volt drop ( that is inherent in 12v systems ) but the problem is that the Battery VoltMeter is buried in all of this - it's just looking at the wrong voltage !

added onto that the batteries are not seeing the full alternator voltage and thus not getting fully charged even when we have motored for 12 hours - which is why I want to replace the Split Diode
Kevin

 

[ghostlymoron]

I'd make sure all cables are adequately sized for voltage drop first as above then fit a vsr dual sensing (BEP or similar). A NASA BM1 would let you monitor the state of your batteries but don't get obsessed by it like some people do.
There's probably other bits of kit available now as I haven't done this kind of mod for a few years but the VSR transformed the charging on Anemone for 50 quid. I just checked battery voltage from time to time with a multimeter and it was always fine. (This involved lifting seat cushions and rummaging below so wasn't done too often). If doing now I'd fit a remote meter). Once you've got a reliable charge splitter, it'll take care of itself.

 

[john_morris_uk]

Add a wire to get the alternator to sense the actual battery voltage. Your batteries will then be charged properly as the diode loss is taken out of the equation. It solves a lot of your problems.

 

[pvb]

Converting the alternator to voltage sensing would be a quick and easy fix which will overcome the voltage drop in your diode splitter.

If you're still tempted to replace the diode splitter, I'd suggest that you spend a few more quid on a Sterling Alternator-to-Battery charger. This will give you a boosted charge voltage, to charge more quickly, plus it will drop to a float voltage when the batteries are charged, to prevent overcharging. It incorporates diodes so effectively replaces the splitter diode.

But you really need to do something about the voltage drops in your system, perhaps by replacing the main switch and using different bolt-on fuses. You've listed the voltage drops and say "and then the same on the negative side", but surely you haven't also got switches and fuses on the negative wires?

 

[neil1967]

I fitted the sterling splitter, which has virtually no loss. It is a fit and forget device, which prioritises the start battery. Yes it is more money than a VSR, but I'm happy with it.

 

[KevinT1]

But you really need to do something about the voltage drops in your system, perhaps by replacing the main switch and using different bolt-on fuses. You've listed the voltage drops and say "and then the same on the negative side", but surely you haven't also got switches and fuses on the negative wires?

They are all Bolt on Fuses - you would be surprised at the voltage drop across them - in this case when I had everything turned on then 25 amps caused a 35mV drop across the 50 amp Fuse

the Negative side had 3 separate cables, which had :
17mv from the Battery terminal to the Main Negative clamp ( where all the Negatives go to )
98mv from the Main Negative Clamp to the Ancillary Busbar on the switch panel
150mV from the Busbar to the Fridge Terminal
so 260mv in total on the negative side in total and they are all small drops , but add up to the 1 volt across the system
I was deliberately trying to see where the voltage drops were occurring so had everything turned on and the fridge turned up high.

 

[john_morris_uk]

There has to be some voltage drop across the fuses - otherwise they wouldn't work!

 

[KevinT1]

Add a wire to get the alternator to sense the actual battery voltage. Your batteries will then be charged properly as the diode loss is taken out of the equation. It solves a lot of your problems.

Thanks John, but which battery bank do I connect it to and as I have a mix of a Split diode on the House battery and a VSR on the Bow Battery ( for the Windlass and Thruster ) then that surely that would lead to overcharging of one or more of the battery banks ?

 

[pvb]

Thanks John, but which battery bank do I connect it to and as I have a mix of a Split diode on the House battery and a VSR on the Bow Battery ( for the Windlass and Thruster ) then that surely that would lead to overcharging of one or more of the battery banks ?

You'd connect it to the domestic bank, which will usually be the most depleted. With the voltage of an ordinary alternator, you won't overcharge batteries - think of car batteries, which are constantly charged and last for years.

 

[prv]

For what it's worth, I replaced the factory-fit diode splitter in Ariam with a Smartgauge / Smartbank and a Merlin AMS alternator booster. The resulting system works really well, I never have to worry about power or charging, it's just there. Our typical motoring patterns (which are by no means excessive, usually just in and out of harbour) seem to keep everything topped up - the booster means that even a short run packs a lot of power into the batteries. We don't have permanent power at our home berth, and I don't generally bother plugging into mains when I visit a marina unless we'll be staying for more than one night - and then it's only to run the water heater, not the charger

Some other good suggestions in this thread though - if the volt drop is the only problem and your alternator has the relevant terminal, John's suggestion of a sense wire is beautifully simple and cheap.

Pete

 

[john_morris_uk]

You'd connect it to the domestic bank, which will usually be the most depleted. With the voltage of an ordinary alternator, you won't overcharge batteries - think of car batteries, which are constantly charged and last for years.

I used to worry about this very problem as well.

However it's the system I've been running on our boats for at least the last 12 years and the batteries are fine. Sense wire is to the domestics and the engine start battery voltage rises quickly but it just sits there and isn't over charged (whatever that means, as in simple terms, lead acid batteries either accept charge or gas. )

Keep an eye on the electrolyte is a good rule, but we rarely need to top our batteries up, even using a sterling alternator booster. 125 Ah starter and 405 Ah domestics.

 

[KevinT1]

Thanks for all the suggestions, 1 will look into the sense wire as per pvb and John, the engine is a MD22 from 1998 so does anybody know if the standard VP alternator has this sense wire ?

I still need to replace the Battery Voltmeter - and whilst I can see the benefit of using the Smart Gauge or a NASA BM, will probably end up with a simple £2 4 character voltmeter off ebay

 

[ghostlymoron]

You usually have to solder the sensing wire into the alternator which is tricky. You can no doubt find a YouTube video of how to do it but, unless you're confident, I would get an auto electrician to do it.

 

[john_morris_uk]

It would also help you no end to fit a modern alternator charge controller at the same time. . Not sure it matters which one so long as it's got a 'battery voltage sense' connection. You'll probably still have to solder a connection inside the alternator but you'll end up with a much better system. Adverc and Sterling are two common makes.

 

[prv]

You usually have to solder the sensing wire into the alternator which is tricky.

The factory alternator on my Volvo D1-30 has a sense terminal on the back. By default it's connected to the output by a short jumper lead, but converting to battery sense is as simple as swapping over a spade terminal.

What did require soldering onto the brushes was the smart booster - which was definitely worth it as described above.

Pete

 

[BabaYaga]

You'd connect it to the domestic bank, which will usually be the most depleted. With the voltage of an ordinary alternator, you won't overcharge batteries - think of car batteries, which are constantly charged and last for years.

Unless there are similar voltage drops in the wiring between the alternator diode pole and the starter battery, compared to those in the house battery wiring, I do think there is a certain risk of overcharging the starter battery.
At least you need to check carefully: What is the voltage at the starter battery when it is 14,4V at the house battery.
As already said, priority should be to reduce voltage drops, for instance is a breaker in the charge circuit necessary? I do without.

 

[john_morris_uk]

Unless there are similar voltage drops in the wiring between the alternator diode pole and the starter battery, compared to those in the house battery wiring, I do think there is a certain risk of overcharging the starter battery.
At least you need to check carefully: What is the voltage at the starter battery when it is 14,4V at the house battery.
As already said, priority should be to reduce voltage drops, for instance is a breaker in the charge circuit necessary? I do without.

The question behind that is, "What do you mean by 'overcharging'?"

As I said before, Lead Acid batteries either accept charge or they don't. Simplifying things slightly, as they reach maximum charge, the voltage rises. If you raise the charge voltage then you might get some gassing, but 'overcharging' is a bit of a misnomer. The engine start battery voltage rises very quickly and it stops accepting very much charge (even when the alternator boost is in operation because of the domestics demanding charge.)

My practical experience of the last twelve years plus of using a split diode and sensing the domestic bank (on two different boats) is that the engine start battery just doesn't care. Furthermore we rarely have to top up the electrolyte.

 

[VicS]

Unless there are similar voltage drops in the wiring between the alternator diode pole and the starter battery, compared to those in the house battery wiring, I do think there is a certain risk of overcharging the starter battery.
At least you need to check carefully: What is the voltage at the starter battery when it is 14,4V at the house battery.
As already said, priority should be to reduce voltage drops, for instance is a breaker in the charge circuit necessary? I do without.

If the sensing wire is connected to the battery side of the diode splitter, rather than to the battery itself, it will ensure that the alternator compensates for the volt drop across the splitter.
Any volts drop in the wiring between there and the battery should be minimised by adequately sized good quality wiring and other components, something which the OP needs to address if his quoted figures are anything to go by