VSR rewiring

[lustyd]

The image wasn't meant to be proof of anything, other than the fact that i monitor my electrics.

As usual, you want to just argue until the cows come home, so i'll leave you to that.

I’m not sure where you’re going with this. I was trying to work out how your post was relevant and you seem to be saying it wasn’t I’m not trying to argue with you, I genuinely don’t know why you’re posting if it’s not to contribute to the thread

 

[lustyd]

Otherwise, it will open when it reaches it's opening (disconnecting) voltage (12.7v or whatever) and the engine start battery will not discharge further (other than actual engine stating and long-term self-discharge).

That’s the point though it never reaches that voltage. As shown on the other thread the battery (which in this case is both banks, since VSR is closed) can be discharging while maintaining a voltage above VSR cut off due to input from chargers or solar. I’m not misreading anything, I spent months watching it happening last year using the Victron kit to monitor the voltage and charge/discharge.

 

[andsarkit]

We all agree that a small proportion of the capacity of a fully charged engine battery can discharge through the VSR and support the house batteries. I really don't think this is a problem unless your engine battery is marginal in capacity.

If you fully charged the engine battery and let it stand it will settle at about 12.7V. If you then connect it to a house battery also at 12.7V nothing will happen and no current will flow. If the house batteries discharge further the VSR will disconnect. If the house batteries are being charged and the voltage rises above 12.7V then current will flow into the engine battery.
There will be a temporary effect if the engine has been running and the engine battery is at 14V and it will just revert to it's normal resting voltage a bit quicker as a little charge flows to the house bank.

As long as you occasionally run the engine to bring the engine battery up to full charge then I don't think you will notice any loss of battery life if they sit for a while at 90% SOC.
Obviously temperature and exact battery type will have a small effect on these values but not enough to cause any problems.
There is a different potential problem if you have a multi stage charging system which may be confused by the VSR cutting in half way through a cycle.

 

[lustyd]

Did you read the thread? What you posted is pure theory and in a real life scenario on board with solar that's not what happens through the season. You're quoting resting battery voltages, we're talking about charging battery voltages while load is applied. It's much messier than the theory in real life, especially when you add in VSR delays, cloudy days and light loads.

 

[pmagowan]

I just don’t know how a charger can maintain 14V at the battery terminals and the battery being in a net discharge situation. That doesn’t make sense to me. If the charger is putting out enough amps to maintain 14V then any 12V battery connected should be charging. If it is not putting out enough amps to counteract the discharge then it can’t maintain 14V surely. This is irrespective of the VSR with the only additional factors with the VSR being a potential to confuse the timer through frequent but insufficient bursts of charge.

 

[geem]

I just don’t know how a charger can maintain 14V at the battery terminals and the battery being in a net discharge situation. That doesn’t make sense to me. If the charger is putting out enough amps to maintain 14V then any 12V battery connected should be charging. If it is not putting out enough amps to counteract the discharge then it can’t maintain 14V surely. This is irrespective of the VSR with the only additional factors with the VSR being a potential to confuse the timer through frequent but insufficient bursts of charge.

I have been liveaboard for the best part of 8 years and live off solar. I am a bit of an anorak when it comes to batteries and charging. I monitor everything and have several voltmeter and ammeters installed. I don't think it is possible to have a discharge on the battery such that it will deplete if the voltage is high enough. The only issue is the stupid low disconnect voltage of most VSRs. Its one of the reasons why we don't use one. I tried it and didn't like the results.
If the solar output is inadequate to meet the load on the combined engine and house bank whilst the VSR is engaged, the voltage will drop until the VSR disengages. I suspect the OP simply does not have sufficient solar to meet his needs and the batteries are not hitting float by lunchtime and simply staying on float all afternoon as our would do before we changed over to lithium 2 months ago

 

[lustyd]

The system only needs to maintain 12.8 for most VSRs to remain closed, and that 12.8 is the system voltage, not the battery voltage so can be much higher than the expected for a discharged battery, especially with two banks connected. More solar will mask the problem and make it worse as it will keep the voltage up through the discharge cycle

 

[geem]

The system only needs to maintain 12.8 for most VSRs to remain closed, and that 12.8 is the system voltage, not the battery voltage so can be much higher than the expected for a discharged battery, especially with two banks connected. More solar will mask the problem and make it worse as it will keep the voltage up through the discharge cycle

The system voltage is the battery voltage, less volt drop

 

[geem]

The system voltage is the battery voltage, less volt drop

Does your solar connect direct to the batteries?

 

[Andrew_Trayfoot]

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

Do you have a wiring diagram by any chance.

 

[Andrew_Trayfoot]

Do you have a wiring diagram by any chance.

Ignore me just found one further up

 

[B27]

One thing to consider is that things like VSRs and chargers often have a delayed response to voltage.

The 'voltage' is not just some thing you can see on a meter, it varies by the microsecond.

If a VSR and charger are cycling from absorption to float and back, and there's a background load dragging the volts down in the float phase, all kinds of strange things might happen, because the VSR does not see low volts for long enough to disconnect.

I don't doubt LustyD's observations, but I question his explanation of them.

To understand what's going on, we need to look at the volts and current much quicker than the various devices are reacting.


I think it's quite likely that engine batteries will get destroyed by overcharging with many VSR systems.

 

[PaulRainbow]

One thing to consider is that things like VSRs and chargers often have a delayed response to voltage.

The 'voltage' is not just some thing you can see on a meter, it varies by the microsecond.

If a VSR and charger are cycling from absorption to float and back, and there's a background load dragging the volts down in the float phase, all kinds of strange things might happen, because the VSR does not see low volts for long enough to disconnect.

I don't doubt LustyD's observations, but I question his explanation of them.

To understand what's going on, we need to look at the volts and current much quicker than the various devices are reacting.


I think it's quite likely that engine batteries will get destroyed by overcharging with many VSR systems.

That's just nonsense.

 

[lustyd]

Probably worth closing this one off now. My house bank died (probably due to dodgy charger) and as a result was replaced with a LiFePo4 and the VSR removed completely, getting replaced with a B2B so all kind of moot now. There's no longer a route for the house side to affect the engine side, although as discussed in other threads there are new and interesting charger choices to be made now.
All seems to be a better setup now so not entirely upset about being forced into making the changes