oakleyb
Well-Known Member
Which is best ? I have 2 banks, starter and 2 x 115 domestic and a 125amp alt. I'm leaning towards the VSR
Split diode or VSR
- Thread starter oakleyb
- Start date
Tranona
Well-Known Member
VSR has lower voltage loss meaning more goes into your battery. Fit it!
NickRobinson
Well-Known Member
VSR is the modern way to go. However, if the alternator volts sense wire goes to the batteries, ie not 'machine sensed', it will boost correctly, overcoming the diode losses. (I have this setup)
john_morris_uk
Well-Known Member
Only if you don't wire the battery sense of the charging system to the battery!
Diodes - no working parts, but you get a loss if you don't wire it all up correctly.
VSR - mechanical relay with physical contacts that will need replacing eventually.
Both are excellent but need to be used and wired with a bit of knowledge.
FWIW I've used a diode splitter on my last two boats and for over twenty years, but I've always wired it that my smart alternator charger senses the battery voltage at the domestic bank itself and therefore compensates for any voltage loss in the diodes.
ghostlymoron
Well-Known Member
VSR is much easier to fit as it doesn't involve soldering wires into your alternator.
boatingdave
Well-Known Member
VSR much more versatile and almost zero insertion loss as they don't have to overcome the 0.6V bias drop. I understand what Nick is saying but that will only work with a specific alternator/battery/sensing wire configuration which you may not have. Also has a reasonably high cut out so will prevent the 'donor' batteries discharging (unlike a diode block).
prv
Well-Known Member
Some alternators come with battery sensing already provided via a terminal on the back. Sometimes there's a short link between this terminal and the positive, to make it machine-sensed by default but with the option of battery-sensed if you replace the link with a wire to the battery.
Can you elaborate on this? I don't have any experience with diode splitters but I don't understand why they wouldn't "prevent the 'donor' batteries discharging" - surely that's the whole point of them?
Pete
john_morris_uk
Well-Known Member
But many decent alternator charge controllers are fitted by this method. Your argument isn't against diodes but against many of the smart alternator regulators that are available.
And its not hard to modify the alternator. I've done several.
I would suggest that whatever method of battery splitting you use, if you've got a decent alternator charge regulator/booster, make sure you sense the battery voltage from the battery. (And put a small fuse in the sense wire!)
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sailorman
Well-Known Member
And i would make sure it a "dual sensing" type, so it works when charging the domestic bank via a mains charger
john_morris_uk
Well-Known Member
Some Mains Chargers come with blocking already built in. Our Sterling charger is permanently connected to the battery banks and doesn't need to go through any split charging system. Its got several outputs and for a two bank system you tie the majority together and connect to the domestic batteries. The engine start battery gets a nominal single charge outlet as its never really discharged to any great extent.
sailorman
Well-Known Member
we also have a Wind gen wired into the domestic bank, others may have a PV panel, hence the dual sensing
john_morris_uk
Well-Known Member
I've got a wind generator in as well. It goes through its own blocking/sensing circuit straight to the batteries. The wind generator regulator is also wired ready for PV panels.
Paul_R
New Member
I'm not convinced that the complexity of arranging the chargers so that PV and Wind gen can re-charge the starter battery is justified. It's simpler to just use them for the domestic bank. Most pleasure craft users run the engine long enough to recharge the starter battery without need for additional charging.
Also there are choices other than VSRs and diode splitters. VETUS produce a MOSFET based device misleadingly described as a diode splitter and there's a Sterling device that may be solid state too. These have almost negligible voltage drops in normal use.
sailorman
Well-Known Member
My Aerogen is direst to the batteries with a control circuit & dump resistor again direct to the dom batts
boatingdave
Well-Known Member
Pete, sorry misquoted, didn't finish the sentence 'if not fitted correctly'. I've see split charging diodes fitted in many ways, if correct and the alternator supply is taken directly to the input and each output goes to each bank it is correct that both banks are isolated. The main problem with ALL of the solid state splitters is heat dissipation and the voltage drop varies depending on the current draw (internal resistance is reasonably fixed) so the power has to dissipate somehow., the 0.6 is approx the minimum it would be, depending on the current the drop could in excess of one volt. The VSR, particularly the dual sensing relays, give you the flexibility that 'any' charging through engines, mains chargers etc are balanced so if any one of the methods are being used the charge can get to any of the banks serviced by the VSR. I've used them for years and never had any battery problems. Ironically, I've just realised, not on the current boat. Need to do something about that.
nigelmercier
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Where I would say the opposite it the case, you need to inhibit it when using a dual or multiple mains chargers.
BabaYaga
Well-Known Member
One other option well worth considering is a simple, heavy duty relay controlled by alternator D+.
Zero voltage drop and none of the complexities and potential drawbacks of the VSR, e.g. *chatter*.
Using D+ means that battery banks are paralleled ONLY when the engine is running, at all other times they are separated.
prv
Well-Known Member
Mm - I have quite a fancy charger that can be programmed separately for starter and service banks with different chemistry and capacities. Which facility is completely pointless in my installation since as soon as it fires up the SmartBank parallels the two banks anyway
Ariam doesn't spend much time plugged into the mains, so I haven't bothered doing anything about it. Definitely sub-optimal, though.
Pete
john_morris_uk
Well-Known Member
Mm - I have quite a fancy charger that can be programmed separately for starter and service banks with different chemistry and capacities. Which facility is completely pointless in my installation since as soon as it fires up the SmartBank parallels the two banks anyway
Ariam doesn't spend much time plugged into the mains, so I haven't bothered doing anything about it. Definitely sub-optimal, though.
Pete
That's where a diode splitter (with battery sensing to compensate for any losses) and the mains fancy charger wired straight to the batteries would solve the problem.
john_morris_uk
Well-Known Member
I have wired ours the same. The engine starter battery is always near 100% and it's only the domestics that I worry about.
