Solar MTTP Regulator and a Split Charge Relay

[Andrew_Trayfoot]

Am struggling to find much on the internet to confirm the best setup for a system with a Split Charge Relay and a Solar MTTP Regulator...
I have a cheep regulator with 2 outputs (one for starter and 1 for domestic bank) my feeling is that this may get confused by the split charge relay.
I could get a one if these (which would give me capacity to increase the PV in the future), but which battery is it best to connect it to and how will it effect the split charge relay?

 

[PaulRainbow]

I think you will find you shouldn't use dual output controllers with a VSR, check the specs of the controller. You can fit an MPPT controller (your link doesn't work) and a VSR, i'd connect the controller to the domestic bank.

 

[Andrew_Trayfoot]

Thanks Paul.

New link:


Victron Energy SmartSolar MPPT 75V 10 amp 12/24-Volt Solar Charge Controller (Bluetooth) Amazon.co.uk

 

[William_H]

I would suggest that OP fit a small panel connected directly to engine battery. (with or without a controller. The MPPT and larger panel connected to domestic battery. VSR would normally be disconnected when batteries are turned off when you leave the boat.
If you want to connect one panel using VSR you need to wonder if and when the panel will get voltage up to VSR switch on voltage. About 13.5 volts or so. Pluys if it does it will use some current to operate the relay which may negate some of the small charge available in winter. Obviously a large panel array in lots of sun is going to work the VSR fine just like an alternator. But in winter? ol'will

 

[rogerthebodger]

I would suggest that OP fit a small panel connected directly to engine battery. (with or without a controller. The MPPT and larger panel connected to domestic battery.
ol'will

That is exactly how my solar panels commented, 50 watt charging 120Ah engine start battery and 600 watt solar charging 1200 Ah domestic battery

 

[Buck Turgidson]

I'm re-thinking my setup after leaving the master switch on with the boat unplugged. My 50W solar did enough to connect the two batteries each day around noon for 35days until both batteries were dead! I'm thinking about binning the VSR which effectively connected both batteries all day even during engine starts which negates the idea of having a big house and small start battery as the house was effectively starting the engine.
I'll know next month if the house battery has any life left and if not I may even go lithium as all my gear except the VSR is victron with Li settings so I will only need a dc-dc for alternator to house charging. If I was to start again I would just use two of the same size batteries with a low voltage cut out on one to save it for that emergency engine start that never happens in reality.

 

[PaulRainbow]

I'm re-thinking my setup after leaving the master switch on with the boat unplugged. My 50W solar did enough to connect the two batteries each day around noon for 35days until both batteries were dead! I'm thinking about binning the VSR which effectively connected both batteries all day even during engine starts which negates the idea of having a big house and small start battery as the house was effectively starting the engine.
I'll know next month if the house battery has any life left and if not I may even go lithium as all my gear except the VSR is victron with Li settings so I will only need a dc-dc for alternator to house charging. If I was to start again I would just use two of the same size batteries with a low voltage cut out on one to save it for that emergency engine start that never happens in reality.

For this to happen, there is something wrong with your setup, or batteries.

 

[Buck Turgidson]

For this to happen, there is something wrong with your setup, or batteries.

This is my setup. Please tell me what is wrong?
As soon as the solar raises the voltage the Cyrix connects. The two batteries equalise and disconnect when the solar can't make charge.

 

[onesea]

for over a decade I had a 30watt panel connected to my domestic battery’s with a cheap PWM charge regulator.
When the battery hits the required voltage the VCR kicks in and charges both engine and domestic battery.
When the engine is running it charges the Engine battery and again the VCR kicks in and charges both.

I have never had a flat battery. We now have 230watt of charging and can run a fridge from the load output on charge controller. Still no flat battery however when we leave the boat the ONLY discharge is through the charge controller.

If any one has a 30watt solar panel and flat batteries I would look to parasitic draws.

I should say I use PWM as the gains through having MPPT just don’t seem worth the cost. At our latitudes with lead acid batteries the gains are minimal IMHO.

 

[Buck Turgidson]

for over a decade I had a 30watt panel connected to my domestic battery’s with a cheap PWM charge regulator.
When the battery hits the required voltage the VCR kicks in and charges both engine and domestic battery.
When the engine is running it charges the Engine battery and again the VCR kicks in and charges both.

I have never had a flat battery. We now have 230watt of charging and can run a fridge from the load output on charge controller. Still no flat battery however when we leave the boat the ONLY discharge is through the charge controller.

If any one has a 30watt solar panel and flat batteries I would look to parasitic draws.

I should say I use PWM as the gains through having MPPT just don’t seem worth the cost. At our latitudes with lead acid batteries the gains are minimal IMHO.

If you are referring ti my case, I left everything ON by mistake.
What it demonstrated to my cost was that this will deplete BOTH batteries if you use a dual sensing VSR with not enough solar. In the summer months When I'm sailing I connect a second panel in series. Total 100W and this is enough to provide autonomy in the MED so the behaviour only showed itself in the winter when I had removed half the solar but forgot to switch off the boat.

 

[VicS]

This is my setup. Please tell me what is wrong?
As soon as the solar raises the voltage the Cyrix connects. The two batteries equalise and disconnect when the solar can't make charge.

The most obvious thing I can see that is wrong with your diagram is that there is no connection between the domestic system negative and the engine system negative

As you show it the alternator will not not charge the house battery and the solar system will not charge the start battery. In fact the VSR will not even respond to the to the solar system.

A connection should exist as shown below.

Rather surprised that you seem to have a second monitor or smart shunt on the start battery. That is overkill. The house battery smart shunt will monitor the start battery voltage. That is adequate.
The second battery voltage sensing wiring is linking the two battery positives through thin wiring. That is wrong but the fuses will soon blow. If you must have two battery monitors disconnect the second battery monitoring wiring . It will not be needed.

What I assume is a fuse in the Cyrix negative is not needed but a switch can be useful as it can be used to disable the cyrix

However I cannot see anything that would explain your complete discharge of both batteries. The Cyrix will only close when it senses 13 to 13.8 volts on one or other of its terminals and will open again when that falls below 11 to 12.8 volts, In each case the exact voltage will depend its "intelligent trend detection" ability. Even if the Cyrix ix faulty and remained closed it should not cause the complete discharge of both batteries.

 

[PaulRainbow]

The most obvious thing I can see that is wrong with your diagram is that there is no connection between the domestic system negative and the engine system negative

As you show it the alternator will not not charge the house battery and the solar system will not charge the start battery. In fact the VSR will not even respond to the to the solar system.

The VSR has a negative connection to the engine battery, so the alternator should charge the domestic battery, but as you say, the solar won't charge the engine battery, neither will the shore charger.

However I cannot see anything that would explain your complete discharge of both batteries. The Cyrix will only close when it senses 13 to 13.8 volts on one or other of its terminals and will open again when that falls below 11 to 12.8 volts, In each case the exact voltage will depend its "intelligent trend detection" ability. Even if the Cyrix ix faulty and remained closed it should not cause the complete discharge of both batteries.

I agree. Both batteries should be able to sit there for the 35 days that Buck mentions, without going flat, if there are no loads. He also mentions that the the problem occurred because the isolator switch was left on, this has no relevance to the VSR or solar panel, (even if there was a negative cable between the two batteries) because the VSR and solar controller are both connected to the battery side of the isolator switch.

It's possible that there was a load on the domestic battery, which flattened it, but it doesn't explain how the engine battery was flattened, although Buck says "effectively connected both batteries all day even during engine starts" so perhaps regular engine starts with no charging from solar might have caused it.

 

[VicS]

It's possible that there was a load on the domestic battery, which flattened it, but it doesn't explain how the engine battery was flattened, although Buck says "effectively connected both batteries all day even during engine starts" so perhaps regular engine starts with no charging from solar might have caused it.

The isolator switch is obviously a dual circuit switch. Maybe it is the version with a battery combining position and was left in that position. Or perhaps the consequence of the batteries being linked by the second battery monitoring wiring.

 

[Buck Turgidson]

To clarify, there is a common neg between the two batteries, (the schematic is a work in progress). There was a continuous load of 1.5amps on the house( both) batts. No engine starts during the 35 days I was away from the boat. Both batteries very dead when I arrived.i charged the engine bat for an hour then connected both and shore power and could start the engine. I ran the engine for 4 hours (35amp alternator) with shore power connected (17 amp charger) and monitored both battery temperatures by touch. As neither got hot I left the charger on overnight. In the morning under parasitic loads the batteries both showed the same voltage (12.9) but the engine batt fed the house at 3.1amps with the voltage very slowly dropping. The cyrix disconnected after about 10 minutes with both batteries reading 12.7. I reconnected shore power and have left it like that with the charger (victron ip 67) in storage mode at 13.2v .
The first thing I will check when I get back is how quickly the house battery discharges under my normal 1.5A load . As it was sitting at very low voltage ( between 5 and 8v) for days I don't hold out much hope then I will see if the engine bat can start the engine without help from shore power or the house battery before deciding whether to change either or both. My assumption is both.

 

[Buck Turgidson]

The isolator switch is obviously a dual circuit switch. Maybe it is the version with a battery combining position and was left in that position. Or perhaps the consequence of the batteries being linked by the second battery monitoring wiring.

It is a dual switch and was not in combine position.

 

[Buck Turgidson]

 

[PaulRainbow]

Those battery voltages will not cause the VSR to close, but it could be possible that the solar controller voltage might close it, although i can't say that i've heard of it happening in these circumstances.

Solar yield was typically around 5ah each day, whilst the load was 1.5a x 24 hours = 36ah each day, easy to see why the domestic bank was discharged.

 

[Buck Turgidson]

Those battery voltages will not cause the VSR to close, but it could be possible that the solar controller voltage might close it, although i can't say that i've heard of it happening in these circumstances.

Solar yield was typically around 5ah each day, whilst the load was 1.5a x 24 hours = 36ah each day, easy to see why the domestic bank was discharged.

Yes, what it did show was that my AIS transmitter could get a position out once a day even down at 8 ish volts when the sun shone! That was how I realised something was up.

 

[PaulRainbow]

Yes, what it did show was that my AIS transmitter could get a position out once a day even down at 8 ish volts when the sun shone! That was how I realised something was up.

Certainly sounds like the AIS was being powered by the solar, so perhaps it was closing the VSR.

You could take the VSR out (as you suggested earlier) and fit a small panel to maintain the engine battery. Or you could fit a switch in the VSR negative (as eluded to by Vics earlier) and turn the VSR off when the boat is unattended/Winter etc.

 

[VicS]

You could take the VSR out (as you suggested earlier) and fit a small panel to maintain the engine battery. Or you could fit a switch in the VSR negative (as eluded to by Vics earlier) and turn the VSR off when the boat is unattended/Winter etc.

If the VSR is removed some alternative would be needed to charge the house battery from the alternator. Argofet perhaps or manually via the combine battery position on the isolator.