Fitting a Victron MTTP question

[Gixer]

I’ve just bought a Victron MTTP controller and have a few questions.

I’ve managed to get the 75/15 version which is overkill for now as I’m only going to get a small 30w panel and add more later, does this matter?
Can I wire it directly to one battery in the same way as my mains charger and use the Cyrix to charge the second battery?
If I have the solar connected and switch on the mains charger will this damage anything?

Thanks in advance.

 

[noelex]

I’ve managed to get the 75/15 version which is overkill for now as I’m only going to get a small 30w panel and add more later, does this matter?

No.

Can I wire it directly to one battery in the same way as my mains charger and use the Cyrix to charge the second battery?

Yes, but make sure you have a fuse between the battery and controller (preferably close to the battery) to protect the wire.

If I have the solar connected and switch on the mains charger will this damage anything?

No, but if you are leaving this combination connected for long periods with no load on the batteries it is better to reduce the voltage set points for the best battery life especially if you add more solar.

 

[Gixer]

That’s amazing, thank you for the quick reply.

 

[PaulRainbow]

That’s amazing, thank you for the quick reply.

Post 2 is correct, but, if you turn the mains charger on it will almost certainly override the solar. If you leave it on all night, the batteries will be fully charged in the morning, leaving nothing for the solar to do.

 

[Gixer]

Post 2 is correct, but, if you turn the mains charger on it will almost certainly override the solar. If you leave it on all night, the batteries will be fully charged in the morning, leaving nothing for the solar to do.

Thanks Paul, I’m not planning to run them side by side. This was more about, if I wanted to use the mains charger for some reason, would I need to disconnect the solar?

 

[PaulRainbow]

Thanks Paul, I’m not planning to run them side by side. This was more about, if I wanted to use the mains charger for some reason, would I need to disconnect the solar?

No need to disconnect.

 

[peteK]

Be aware that the Victron controller has a self consumption of 20ma so on a cloudy day in winter with a 30w panel its likely to take out more than it puts in.

 

[Gixer]

Argh, didn't know that! Thanks for bringing it to my attention. I guess that's a case for mains in the winter and solar in the summer, or a bigger panel.

Be aware that the Victron controller has a self consumption of 20ma so on a cloudy day in winter with a 30w panel its likely to take out more than it puts in.

 

[Aja]

I’ve just bought a Victron MTTP controller and have a few questions.

I’ve managed to get the 75/15 version which is overkill for now as I’m only going to get a small 30w panel and add more later, does this matter?
Can I wire it directly to one battery in the same way as my mains charger and use the Cyrix to charge the second battery?
If I have the solar connected and switch on the mains charger will this damage anything?

Thanks in advance.

Exactly the set up I have. Just works.

 

[Alex_Blackwood]

Be aware that the Victron controller has a self consumption of 20ma so on a cloudy day in winter with a 30w panel its likely to take out more than it puts in.

Does that draw from the panel? are there not diodes to prevent battery discharge?
Edit. Got my thick head on today Obviously from the battery

 

[Sandy]

All Victron kit draws power. In fact all power monitoring systems draw power.

 

[Gixer]

Sorry to bump this thread but I have another quick question.

I’m putting a switch in the + from the mttp to the battery (as well as a fuse). If I turn this switch off and leave the panel connected will it do any harm? I’m guessing with the mttp’s power disconnected the circuit is broken so the power just stops. Can someone confirm please?
Thsnks

 

[noelex]

It is safer to have a means of disconnecting the panels and turning this off first. Turning off just the battery usually does not cause damage, but it can.

On some boats it is also possible for the solar controller to continue to power the systems, even though the battery is disconnected. This depends on how the boat is wired. If this can occur, without a battery to act as a buffer, the voltage can reach dangerous levels. This can damage other electronics.

 

[peteK]

Safer to put the switch between the solar panel and controller,that way your not powering the controller without a load.

 

[Sandy]

Sorry to bump this thread but I have another quick question.

I’m putting a switch in the + from the mttp to the battery (as well as a fuse). If I turn this switch off and leave the panel connected will it do any harm? I’m guessing with the mttp’s power disconnected the circuit is broken so the power just stops. Can someone confirm please?
Thsnks

Why?

 

[Gixer]

Why?

Thanks for responding. Sorry, what’s the ‘why’ referring to?

Why should I add a switch or why would I want to disconnect the solar?

I hope you can elaborate.

Thanks

 

[wonkywinch]

I bought the same item but as I have 3 sets of batteries (eng, thruster, domestic), a battery charge splitter (Cristec RCE 150-1E-3IG) and a NASA BM2 battery monitor, I connected the MPPT output to the alternator connection on the splitter so the charge is fed through the shunt and surplus energy diverted by the splitter.

Early days but it seems to work with the £200 200W portable panel from Renogy.

 

[Sandy]

Thanks for responding. Sorry, what’s the ‘why’ referring to?

Why should I add a switch or why would I want to disconnect the solar?

I hope you can elaborate.

Thanks

Simply, why would you want to switch off a free supply of power?

 

[Baggywrinkle]

I’ve just bought a Victron MTTP controller and have a few questions.

I’ve managed to get the 75/15 version which is overkill for now as I’m only going to get a small 30w panel and add more later, does this matter?
Can I wire it directly to one battery in the same way as my mains charger and use the Cyrix to charge the second battery?
If I have the solar connected and switch on the mains charger will this damage anything?

Thanks in advance.

Ensure the 30W panel delivers more than the start voltage for the MPPT which is 19.5v

Your 30W Panel will deliver approx ....


MPPT Calculator - Victron Energy

You can enter the exact values for your panel, wiring and location to get a better estimate, but even in the depths of winter in Cardiff you can expect a daily yield from the panel of 0.02 kWh which is 20 Wh - @ 12V that equates to (20/12) = 1.66Ah - probably closer 1.2Ah after losses.

The self consumption of the MPPT @ 12V is 19mA (load on), 10mA (load Off).

https://www.victronenergy.com/uploa...-MPPT-75-10,-75-15,-100-15,-100-20_48V-EN.pdf

Over 24hrs, the MPPT 75/15 will consume (24x0.019) = 0.456 Ah (load on)

Which means you can leave it connected to the batteries permanently without killing your batteries.

 

[Gixer]

Simply, why would you want to switch off a free supply of power?

I was wondering if I switch the power off from the battery to the MPPT, what would it do with the power coming in from the solar? I was guessing as there’s no power to the MPPT the circuit is broken a therefor nothing is happening. Just wanted to be sure.

That you @Baggywrinkle for the detailed response. I’m sorry you had to spell it out for me but this is all pretty new to me. It’s fascinating stuff!