Replacing diode pack with VSR

Porthandbuoy

Porthandbuoy

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I'm thinking of replacing the split charge diode pack with a VSR. My charging sources are 60W solar (via a charge controller), a 15A smart mains charger and an 80A Hitachi alternator. All three are wired to sense the house batteries (2 x 100Ah SLA) so the 0.7 volt drop across the diode pack is not an issue and the batteries float happily at 13.8V, measured at the battery posts.
VSRs seem to be the preferred option these days, but surely replacing a solid state device with an electro-mechanical device subject to 'chatter' and/or burnt contacts is a step backwards when it comes to reliability.
 
Or you could replace it with a Sterling A2B for better charging.

Baggywrinkle of this parish has a spare one that I'm sure he'll do a deal on for you.
 
Porthandbuoy said:
I'm thinking of replacing the split charge diode pack with a VSR. My charging sources are 60W solar (via a charge controller), a 15A smart mains charger and an 80A Hitachi alternator. All three are wired to sense the house batteries (2 x 100Ah SLA) so the 0.7 volt drop across the diode pack is not an issue and the batteries float happily at 13.8V, measured at the battery posts.
VSRs seem to be the preferred option these days, but surely replacing a solid state device with an electro-mechanical device subject to 'chatter' and/or burnt contacts is a step backwards when it comes to reliability.
Click to expand...
Worth checking but you may find that the VSR is a Solid State Relay (SSR) I believe some are and some are hybrid or electro- mechanical.
Expect PR will be around with a definitive ;)
 
Porthandbuoy said:
I'm thinking of replacing the split charge diode pack with a VSR. My charging sources are 60W solar (via a charge controller), a 15A smart mains charger and an 80A Hitachi alternator. All three are wired to sense the house batteries (2 x 100Ah SLA) so the 0.7 volt drop across the diode pack is not an issue and the batteries float happily at 13.8V, measured at the battery posts.
Click to expand...
So why change ?
Porthandbuoy said:
VSRs seem to be the preferred option these days, but surely replacing a solid state device with an electro-mechanical device subject to 'chatter' and/or burnt contacts is a step backwards when it comes to reliability.
Click to expand...
My preferred VSR is the Victron Cyrix, which is a microprocessor controlled heavy duty relay which does not suffer from chatter. I've known these to last many years without issues.

If you diode pack is connected to all 3 charging sources and they all work OK you could also consider the Victron Argofet.
 
The point is that standard silicon diodes do drop .7 volt and this was tolerated in older style diode isolators. Some diode types have a much lower volt drop like schotky at about .2 volt and more complex arrangements of filed effect (FET ) transistors can have zero volt drop.
VSR can be a electro mechanical relay and are quite reliable. Or as said they can have FET used as switch in lieu of relay contacts.
The wiring arrangements for VSR will be somewhat different o isolation diodes. Esentially you charge directly you first battery. Often the engine battery from alternator. (original wiring fro engine) Then connect the VSR to sense and activate to connect house battery to engine battery and alternator when engine is running. I would suggest that system.
However OP uses solar charging and mains charger. I would suggest connect the solar system directly to house battery. Add another small panel for engine battery. A VSR wiil usually take some operating current which might be significant for a small solar charge. So VSR off when leaving the boat. Likewise a mains charger will normally be used mainly for house battery. Just move it to engine battery if you think it is needed. or connect to engine battery and rely on VSR to connect to charge house battery.

However given that wiring is already in place it might be easier to replace the old diode pack with low or 0 volt drop diodes. ol'will
 
William_H said:
The point is that standard silicon diodes do drop .7 volt and this was tolerated in older style diode isolators. Some diode types have a much lower volt drop like schotky at about .2 volt and more complex arrangements of filed effect (FET ) transistors can have zero volt drop.
VSR can be a electro mechanical relay and are quite reliable. Or as said they can have FET used as switch in lieu of relay contacts.
The wiring arrangements for VSR will be somewhat different o isolation diodes. Esentially you charge directly you first battery. Often the engine battery from alternator. (original wiring fro engine) Then connect the VSR to sense and activate to connect house battery to engine battery and alternator when engine is running. I would suggest that system.
However OP uses solar charging and mains charger. I would suggest connect the solar system directly to house battery. Add another small panel for engine battery. A VSR wiil usually take some operating current which might be significant for a small solar charge. So VSR off when leaving the boat. Likewise a mains charger will normally be used mainly for house battery. Just move it to engine battery if you think it is needed. or connect to engine battery and rely on VSR to connect to charge house battery.

However given that wiring is already in place it might be easier to replace the old diode pack with low or 0 volt drop diodes. ol'will
Click to expand...
What would be the benefit of all of those changes, given, in post #1 the OP says:

"All three are wired to sense the house batteries (2 x 100Ah SLA) so the 0.7 volt drop across the diode pack is not an issue and the batteries float happily at 13.8V, measured at the battery posts."
 
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