sailorman
Well-Known Member
If my VSR goes kaput i have a change-over switch. in-built redundancy
What's are these?
- Thread starter Hadenough
- Start date
westhinder
Well-Known Member
I was hoping to find clarification of what to me is a black art, but so far I have only got more confusion.
My service batteries (2x155Ah semi deep cycle) never seem to get a good charge from the alternator.
The setup is alternator (80A) - Sterling booster - split diode - battery sensed. I never see much more than 13.5V going into the batteries. I suspect a steep voltage drop.
Would I get a better result with a VSR?
When on mains, the Mastervolt charger puts 14.4 volts into the batteries, so there the split diodes do not seem to have a detrimental effect.
My service batteries (2x155Ah semi deep cycle) never seem to get a good charge from the alternator.
The setup is alternator (80A) - Sterling booster - split diode - battery sensed. I never see much more than 13.5V going into the batteries. I suspect a steep voltage drop.
Would I get a better result with a VSR?
When on mains, the Mastervolt charger puts 14.4 volts into the batteries, so there the split diodes do not seem to have a detrimental effect.
pvb
Well-Known Member
No, there's a fault somewhere. Possibly the Sterling regulator isn't working properly.
westhinder
Well-Known Member
Is there a way of checking the Sterling? The LEDs on it work alright.
VicS
Well-Known Member
But is the Mastervolt charger one with just a single a output and using the same diode splitter as alternator and Sterling controller. Or is it in fact a dual output charger which supplies the battery banks directly. As far as i know only the smallest Mastervolt (10amps) has just a single output.
A larger one ( at least 25amps) would be recommended for the battery capacity you have and all the larger ones have 2 or 3 outputs.
Check on the Mastervolt installation first, just to be sure about it, but then check the Sterling controller installation .
Which Sterling unit do you have ?
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westhinder
Well-Known Member
I do not know the exact types, will check tomorrow
john_morris_uk
Well-Known Member
I don't know what you mean by 'normal split diodes'. If I guess that you mean splitter diodes fitted with no thought to checking charging voltage at the batteries then VSR's are certainly better. However my point all along us that splitter diodes shouldn't be wired in such a simplistic way.
. I've got various battery switches and a spare splitter diode which came with the boat. I am not sure why I bother to carry it around as the current set up (pardon the pun) has worked faultlessly for the last ten years. I had the same system on our previous boat which also worked faultlessly. But I am the first to admit such statements prove nothing.
The only point I want people to understand is that they shouldn't be suckered into condemning split charge systems using diodes just because some of them aren't wired very sensibly.
john_morris_uk
Well-Known Member
Agree 100%. Either the Sterling isn't wired correctly or it isn't working properly. If you've got the instructions for the Sterling, it should tell you which LED's should light (and they are normally labelled on the unit itself). The instructions will also say what colour the voltage sense wire is and you can then follow it to see where it's connected (and check its continuity). Ours goes straight to the +Ve post of the domestic bank through a small in line fuse that's there to protect the wire.
sailinglegend420
Well-Known Member
This highlights major problems with these kind of forums. It needs a book to properly answer most questions posted here, so you are not going to get a full answer which can relate to your installation on your boat. I'm afraid the "confusion" is added by people posting their opinions and often ignoring the facts. Electrickery is basically very logical - Ohms Law is very simple. When the voltage goes down the current goes down if the resistance in the circuit stays the same. If the resistance, or corrosion, goes up and the voltage stays the same then the current in the circuit goes down. The voltage at the batteries can therefore be very different from the voltage at the charge source output because of "resistance" in the circuit. There can be a dozen or more connections, bus bars, or joints, in the positive and negative cables supplying a load. Each can cause a small voltage drop with old corroded connections. A small 0.1v drop on a cable carrying a small current can become 5.0v when carrying a large current. This is where it comes a "Black Art" understanding a fixing problems.
If the voltage sense wire is on the starter battery that will not produce the right voltage at the service battery.
sailinglegend420
Well-Known Member
Normal/old Split Diodes have a volt drop of 0.7 volts or more. This is what causes the problems.
Low loss Split Diodes may have half the voltage drop of normal diodes, and intelligent Ultra Low Loss Split Diodes have nearly ZERO volt drop - according to Mr Sterling's marketing which I have only just found? His "intelligent" Pro Split R looks very interesting and highlights, with diagrams, the problem of too high a voltage at the starter battery. These should work fine and don't need the potential problems of having a voltage sense on the batteries.
I'm not sure many people will understand what you are saying here. It's difficult to wire them incorrectly.
sailinglegend420
Well-Known Member
I would suggest that 25 Amps is not a "large one".
Most FLA batteries need to be charged with a current that is the Battery Capacity/5 - always follow the battery manufacturers recommendations. So the OP's 310Ah bank may need to be charged at 62 amps. So to be able to supply boat loads as well then the charger/alternator needs to be about C/5, which would be 70-75 Amps, not 25 Amps.
geem
Well-Known Member
So if I have 480 amp/hr battery bank at 24v what size charger do I need? your calculation suggests 96 amp at 24v. I only have a 15amp/hr at 24v mains battery charger for use in the winter whilst we are on shore power. The main engine alternator is only 60 amp output at 24v but we do have 320w of solar and a Duogen. if I don't put a bigger mains charger on there am I really at a disadvantage? If I ran my engine, generator and duogen in towed mode I could probably muster 85 amps output at 24v in an emergency but I would have to be underway
pvb
Well-Known Member
No, you're not at a disadvantage. Smaller chargers work fine, they just take longer.
Rivers & creeks
Well-Known Member
I have a VSR from the alternator to three outputs - house - starter - bowthruster. Can I connect the shore power charger to the alternator stud on the VSR so it also sends its charge off those three ways?
VicS
Well-Known Member
Ys you are right 25 amps would still be smaller than recommended ... I misread the OP's post ...... The 35 amp one would be the smallest recommended if you look at the specs on the Mastervolt website.
HOWEVER,the point i was making was that the 10amp one is the only one with a single output. One expects a larger one and all the larger ones have multiple outputs. therefore the fact that charging via the Mastervolt charger is Ok does not , or at least, should not, be taken as confirmation that the diode splitter is OK .
VicS
Well-Known Member
yes or to the priority batttery terminal but you might be better off with a multiple output charger connnected directly to all three batteries.
sailinglegend420
Well-Known Member
You will never get to 100% charged running an engine - unless you go for 24 hrs! You can get to 85% fairly quickly but after that the current into the batteries falls away rapidly so it is not worth running the engine much more.
A properly sized charger and multi-stage regulator means faster charging overnight when you go into a marina. Go in at 2000 hrs and leave at 0800 hrs and your batteries may not be back to 100% - even though the charger says you are in Float mode.
When you run your genset with a larger shorepower charger the runtime will be much less to get to the 85% charged state.
geem
Well-Known Member
Thanks, I was hoping you would say that!
john_morris_uk
Well-Known Member
What I thought I had made clear was that incorrect wiring is 'without voltage sensing at the battery terminal' in this context.
PS I like the high power Schottky diodes that are available with very low forward resistance, but I would still be arguing to put the voltage sense connection at the battery. It means you ensure any voltage drop in the main power cable from the alternator to the battery is also taken into account (ideally with a temperature sensor as well) and the battery charging regime is then guaranteed to be optimal.
Even with a VSR you ought to have an over voltage protection circuit as part of your 'smart' alternator regulator. Its all too easy to motor along with a fault while cooking the batteries...
When we have had alternator belt failure etc, the main clue in the cockpit is the tacho stops working.
sailinglegend420
Well-Known Member
The problem is you can't monitor both batteries, and they may both be at different voltages. You should monitor the service battery.
I agree. The simplest solution is a Battery Monitor with alarms. My BEP alarms can be set for High/Low voltage for three batteries and low Ahs. An external alarm can be fed to the cockpit.