VSR rewiring

[lustyd]

My charger just died and new one en route but the necessity of mucking about with wires got me thinking again about VSR and charging/discharging. Currently the VSR is set up to dual sense which means that when the MPPT charges the engine battery gets connected and drains alongside the house bank, which I think we can all agree is a bad thing. The reality is that with the various charge sources on board, while cruising the VSR is almost never disconnected.
So, current thinking (and I probably have not thought it all the way through!) is to change to single sensing and have the VSR sense wire on the engine side of the engine battery switch so that when the alternator is on it will activate and allow house bank charging. This also means that when the engine switch is off, the VSR can't join the batteries and the engine battery is safe.
I'm then thinking I can connect the trickle charge wires of the Phoenix IP43 1+1 to the battery side of this switch, and it'll trickle charge the engine battery while all switches are off.
On the house side, the MPPT is on the battery side of the switch, along with the VSR sense wire and I think the main charge cable. I think all of these need to stay battery side to ensure the battery gets charged regardless of the state of the switch, as well as to ensure the VSR doesn't activate in a scenario where the engine switch is on and house off, allowing engine battery to power house loads.
Obviously also have an emergency connect switch.

Does all that make sense? This would also seem to offer a better solution to allowing the charger to charge with an appropriate charge profile just for the house bank.

 

[PaulRainbow]

My charger just died and new one en route but the necessity of mucking about with wires got me thinking again about VSR and charging/discharging. Currently the VSR is set up to dual sense which means that when the MPPT charges the engine battery gets connected and drains alongside the house bank, which I think we can all agree is a bad thing. The reality is that with the various charge sources on board, while cruising the VSR is almost never disconnected.

Firstly, i don't see that, in most installations, this is an issue.

So, current thinking (and I probably have not thought it all the way through!) is to change to single sensing and have the VSR sense wire on the engine side of the engine battery switch so that when the alternator is on it will activate and allow house bank charging. This also means that when the engine switch is off, the VSR can't join the batteries and the engine battery is safe.
I'm then thinking I can connect the trickle charge wires of the Phoenix IP43 1+1 to the battery side of this switch, and it'll trickle charge the engine battery while all switches are off.
On the house side, the MPPT is on the battery side of the switch, along with the VSR sense wire and I think the main charge cable. I think all of these need to stay battery side to ensure the battery gets charged regardless of the state of the switch, as well as to ensure the VSR doesn't activate in a scenario where the engine switch is on and house off, allowing engine battery to power house loads.
Obviously also have an emergency connect switch.

Does all that make sense? This would also seem to offer a better solution to allowing the charger to charge with an appropriate charge profile just for the house bank.

If you wanted to change the current arrangement i would not swap the VSR for a single sensing one, for one thing, you'll struggle to find a decent one.

You're obviously correct that the MPPT controller needs to go to the battery side of the isolator, so stick with that.
Connecting the Phoenix trickle output to the engine battery side of the engine isolator make sense.
Don't fit a single sense VSR, fit a Victron Argofet, this will charge all batteries and keep them always separate.

 

[lustyd]

Firstly, i don't see that, in most installations, this is an issue.

If you wanted to change the current arrangement i would not swap the VSR for a single sensing one, for one thing, you'll struggle to find a decent one.

You're obviously correct that the MPPT controller needs to go to the battery side of the isolator, so stick with that.
Connecting the Phoenix trickle output to the engine battery side of the engine isolator make sense.
Don't fit a single sense VSR, fit a Victron Argofet, this will charge all batteries and keep them always separate.

Thanks Paul, we saw these issues last year while cruising. As set up there's no way to prevent the engine battery being part of the house bank.
It's not a different VSR it's how it gets wired. This is covered in the BEP manual.

I did consider the Argofet and can't remember what the issue was but there certainly was a scenario where it wouldn't do what I wanted. Will see if I can remember

 

[pmagowan]

 

[pmagowan]

BEP Switch Cluster and VSR​

Operation	Switch Positions	Effect
Normal On	House and Start On, EP Off	House and Start systems connected to their respective batteries independently. VSR will activate to parallel batteries for charging when engine running
Emergency Parallel	All switches on	Both batteries are joined in 1 bank
Start from House	Start Off, House On, EP On	Start battery will be isolated. House battery will power all systems
Power from Start	Start On, House Off, EP On	House battery will be isolated. Start battery will power all systems
All Off	All Off	Engine and all switched loads will be isolated. Charger and unswitched loads will remain powered

 

[lustyd]

That's the dual sensing setup, and will join the house and start banks any time any charge is present anywhere on the system. It leads to gradual draining of the start battery over time

 

[pmagowan]

Sorry for 3 replies as was trying to cut and paste on a phone. This is how I do it with a BEP switch cluster but you don’t need to use their kit. It is wired differently to their recommendations.

Why would a battery that is connected to a charge source be draining?

 

[lustyd]

Sorry for 3 replies as was trying to cut and paste on a phone. This is how I do it with a BEP switch cluster but you don’t need to use their kit. It is wired differently to their recommendations.

Why would a battery that is connected to a charge source be draining?

because if the overall consumption is higher than the charger provides it drains the battery. The charge source will raise the voltage to charge, closing the VSR

 

[Alex_Blackwood]

because if the overall consumption is higher than the charger provides it drains the battery. The charge source will raise the voltage to charge, closing the VSR

I did think of suggesting that you rearrange the charge sources, possibly with a switch for "Harbour/ Cruising" But, If your out is greater than your in. Then whatever battery is connected will drain. Appreciate you want to keep engine topped up and ready.

 

[lustyd]

I did think of suggesting that you rearrange the charge sources, possibly with a switch for "Harbour/ Cruising" But, If your out is greater than your in. Then whatever battery is connected will drain. Appreciate you want to keep engine topped up and ready.

Yes that's the main worry that eventually the engine will fail to start with the current setup. It's not happened yet but it seems like something that should be fixable. VSR configuration was designed before most of the gubbins we now have, so worth thinking about especially with potential high loads like laptops, projectors, portable speakers and of course the fridge.

I think Paul may be right with the Argofet. I have a feeling my issue was not being able to charge from house side to engine side, but I'm disabling that anyway so probably not a concern

 

[Alex_Blackwood]

Yes that's the main worry that eventually the engine will fail to start with the current setup. It's not happened yet but it seems like something that should be fixable. VSR configuration was designed before most of the gubbins we now have, so worth thinking about especially with potential high loads like laptops, projectors, portable speakers and of course the fridge.

I think Paul may be right with the Argofet. I have a feeling my issue was not being able to charge from house side to engine side, but I'm disabling that anyway so probably not a concern

Whatever happened to good old fashioned sailing with a wet finger in the air!

 

[geem]

I love the simplicity of a small folding solar panel and small mppt dedicated to the engine battery. With adaptive absorbtion setting. Its plugged in when we arrive in a new anchorage, it keeps the battery perfectly charged and ready to go. If we are anchored for a few days, I will unplug the solar and plug it back in after a few days rest

 

[lustyd]

Whatever happened to good old fashioned sailing with a wet finger in the air!

Oh we do that while watching a movie with a coffee

I love the simplicity of a small folding solar panel and small mppt dedicated to the engine battery. With adaptive absorbtion setting. Its plugged in when we arrive in a new anchorage, it keeps the battery perfectly charged and ready to go. If we are anchored for a few days, I will unplug the solar and plug it back in after a few days rest

The trouble is, if you have a dual sensing VSR it doesn't matter where that's connected, it'll charge everything as one bank, or drain everything as one bank. if set up as single sensing I think your mppt connected inside the switch as my trickle charge would be would make sense, and you could still have the main mppt on the house bank as long as the VSR can't close and connect the engine bank in (hence sense outside the switch)

 

[pmagowan]

Interesting. I assumed that if the load was great enough to drain the battery then the voltage would drop and turn off the VSR even if you had a small supply. Perhaps you need some resistance to the sensor in the VSR. Do B2B chargers avoid this issue. The lithium people love them

 

[lustyd]

Interesting. I assumed that if the load was great enough to drain the battery then the voltage would drop and turn off the VSR even if you had a small supply. Perhaps you need some resistance to the sensor in the VSR. Do B2B chargers avoid this issue. The lithium people love them

No because most modern chargers compensate in order to maintain charge profiles so the voltage is pretty much always above the threshold. Perhaps my systems are set up badly but the VSR is almost always closed.

 

[geem]

No because most modern chargers compensate in order to maintain charge profiles so the voltage is pretty much always above the threshold. Perhaps my systems are set up badly but the VSR is almost always closed.

We tried a VSR a few years ago. We had similar problems that the thing was always closed. The engine battery was often on an aggressive charge even though it didn't need. All the solar went into the domestic batteries. Over night the domestic batteries would discharge then spend the morning on charge. Being deep cycle FLA batteries they have quite a absorbtion voltage. This was also going to the fully charged engine batteries via the VSR for no good reason. In addition, the engine start batteries were better at a lower charge voltage than the deep cycle domestic bank. Obviously, this doesn't happen.
With a dedicated MPPT and small solar panel we have full control of the engine charging with adaptive absorbtion and temperature compensation.
Maybe not so important for UK coastal cruising but living aboard in the Tropics on anchor full-time, an isolated, fully charged, ready to go engine battery is essential

 

[lustyd]

So did you remove the VSR or just rewire it?

I definitely want to keep the VSR so I don't have to proactively get the alternator to charge the house bank

 

[andsarkit]

You don't say which VSR you have but here are the specs for the Cyrix one:

In theory the batteries could remain connected down to 12.4V which seems a bit low but is still 70% SOC. It should still leave enough in the engine start battery for several starts.

 

[lustyd]

You don't say which VSR you have but here are the specs for the Cyrix one:
View attachment 158818
In theory the batteries could remain connected down to 12.4V which seems a bit low but is still 70% SOC. It should still leave enough in the engine start battery for several starts.

But you're ignoring the important point, the various chargers push the voltage to 14.something Volts regardless of state of charge, so the battery can be completely flat and the VSR won't disengage. They were designed for a world where alternator comes on and goes off, not a world where an MPPT can generate 14V and only input 0.5A and do so all day every day for weeks on end.

 

[geem]

So did you remove the VSR or just rewire it?

I definitely want to keep the VSR so I don't have to proactively get the alternator to charge the house bank

We removed the VSR. We really didnt need the alternator to charge the house bank. It now does it through a B2B, but only at 17A at 24v with a lithium house bank. We can charge at 100A with the generator and chargers if we need to but, we don't need to