Solar panel wiring etc

[Steve_C]

I will shortly be fitting a 250w panel & MPPT controller. Firstly what rating of fuse would be required? Secondly what order of connecting? I was going to connect to diagonal corners of my 4 battery bank working back from the batteries to the controller and finally connecting the push in adaptors to the back of the panel. Is the plan flawed or does all sound good?

[Pete & Helen]

Documentation with your controller should tell you what fuse to fit. If not then it needs to be lower than the rating of your cable but higher than the max output from your controller with a bias towards the controller value. The fuse protects the wire not the controller.

 

Connect to batteries to where your alternator/ charger is (or should be) connected.

 

Its normal to connect the controller to the batteries then connect the solar to the controller (cover your panel's when doing this).

Edited March 21, 2015 by Pete & Helen

[Phil.]

Depending on your controller you may need to put circuit breakers in. I have an outback and to maintain the warranty it requires circuit breakers to be fitted on the positive from the panel and from the batteries.

[valrene9600]

Documentation with your controller should tell you what fuse to fit. If not then it needs to be lower than the rating of your cable but higher than the max output from your controller with a bias towards the controller value. The fuse protects the wire not the controller.

 

Connect to batteries to where your alternator/ charger is (or should be) connected.

 

Its normal to connect the controller to the batteries then connect the solar to the controller (cover your panel's when doing this).

 

 

 

Where on the battery bank would you suggest the solar controller cables connect, in case the alternator cables are wrongly connected.

[Pete & Helen]

Where on the battery bank would you suggest the solar controller cables connect, in case the alternator cables are wrongly connected.

 

I would suggest that the batteries are re-cabled as per the forums favourite web page http://www.smartgauge.co.uk/batt_con.htmland the solar and charge cables connected in the correct place

[valrene9600]

I would suggest that the batteries are re-cabled as per the forums favourite web page http://www.smartgauge.co.uk/batt_con.htmland the solar and charge cables connected in the correct place

 

I can see in the link method 2 is opposite ends of bank.

Method 3 baffles me. Each battery goes to one cable of + -. So which is the load or do you connect to the single cable either + - and not directly to the battery's.

Everything is easy if you have the knowledge.

Talking charge cables.

[Pete & Helen]

I can see in the link method 2 is opposite ends of bank.

Method 3 baffles me. Each battery goes to one cable of + -. So which is the load or do you connect to the single cable either + - and not directly to the battery's.

Everything is easy if you have the knowledge.

Talking charge cables.

Method 3 is using a "bus bar" (something like this http://www.mobilecentre.co.uk/images/products/Aux_Power/4307006.gif) ineach line like a junction box, so the electrical length of wires from the installation (the appliances, The charger/inverter and solar controller) are identical and so each battery works equally.

[valrene9600]

Thanks

[by'eck]

I will shortly be fitting a 250w panel & MPPT controller. Firstly what rating of fuse would be required? Secondly what order of connecting? I was going to connect to diagonal corners of my 4 battery bank working back from the batteries to the controller and finally connecting the push in adaptors to the back of the panel. Is the plan flawed or does all sound good?

 

Suggest 30 amp fuse on the mppt output with cable run rated for same, since you will be luck to see 18 amps going into batteries. Connection plan sounds fine also.

[Steve_C]

Suggest 30 amp fuse on the mppt output with cable run rated for same, since you will be luck to see 18 amps going into batteries. Connection plan sounds fine also.

 

Thanks.

[BargeeSpud]

OK, I find this conFUSING!

 

My Victron BlueSolar MPPT 75/50 makes no mention of fuses anywhere in the installation instructions, so before I continue with the installation of 4 x 100w panels hooked up with 10mm2 cable, I think I need a little clarity on this. So to fuse or not to fuse, that is the question.

[nicknorman]

OK, I find this conFUSING!

 

My Victron BlueSolar MPPT 75/50 makes no mention of fuses anywhere in the installation instructions, so before I continue with the installation of 4 x 100w panels hooked up with 10mm2 cable, I think I need a little clarity on this. So to fuse or not to fuse, that is the question.

You will connect the MPPT to the batteries by means of cables. This means that these cables can, under short circuit or other unexpected conditions, pass pretty much as much current as the batteries can muster, probably 1000s of amps. That would turn the cable into a white hot firestarter (and if there is any twist in the cable then... Oh never mind). So to protect against this, a fuse should be installed in the +ve close to the batteries (but not actually inside any battery box). The same applies to wiring anything direct to the batteries, a fuse must be fitted to protect against excessive current passing through that wire.

 

I would say there is far less need to put a fuse between the panels and the controller, because the max current is much much less, and I wouldn't bother unless the manual requires it.

[mrsmelly]

You will connect the MPPT to the batteries by means of cables. This means that these cables can, under short circuit or other unexpected conditions, pass pretty much as much current as the batteries can muster, probably 1000s of amps. That would turn the cable into a white hot firestarter (and if there is any twist in the cable then... Oh never mind). So to protect against this, a fuse should be installed in the +ve close to the batteries (but not actually inside any battery box). The same applies to wiring anything direct to the batteries, a fuse must be fitted to protect against excessive current passing through that wire.

 

I would say there is far less need to put a fuse between the panels and the controller, because the max current is much much less, and I wouldn't bother unless the manual requires it.

 

Hi Nick

 

Could you save me a bit of time looking please and answer me one thing?

I have 2 panels they are about 200 watts combined if I remember correctly, they were on my last boat and I am going to wire them into this one when I get chance. Question is what size mppt thingymibob do I need? Will a 10 amp one do the job? Just I dont want to pay for bigger than needed as I doubt I will buy any more solar at least for another year or three.

Taa

 

Tim

[nicknorman]

Hi Nick

 

Could you save me a bit of time looking please and answer me one thing?

I have 2 panels they are about 200 watts combined if I remember correctly, they were on my last boat and I am going to wire them into this one when I get chance. Question is what size mppt thingymibob do I need? Will a 10 amp one do the job? Just I dont want to pay for bigger than needed as I doubt I will buy any more solar at least for another year or three.

Taa

 

Tim

Presuming you have a 12v system, 200w at 12v = 16.6A. In reality it is likely to be less than that due to

1/ the voltage under charge is likely to be nearer 13 than 12, or even more, so at 13v it would be 15.3A, at 14v 14.2A and

2/ it will be a rare day when you actually get 200W from the panels.

 

Therefore a 15A would be adequate most of the time, get a 20A if you want to eek every bit of current out of the panels or to allow for more panel in future. If you do go for a 15A one, check it handles too much panel power gracefully, for that rare day when the panels could put out more than 15A. I think MPPTs do in general, but best to check.

[matty40s]

OK, I find this conFUSING!

 

My Victron BlueSolar MPPT 75/50 makes no mention of fuses anywhere in the installation instructions, so before I continue with the installation of 4 x 100w panels hooked up with 10mm2 cable, I think I need a little clarity on this. So to fuse or not to fuse, that is the question.

The Victron Bluesolar is usually wired directly into the Victron Combi unit which will be connected through a shunt ( posh fuse) to your battery bank.

If you haven't got any other Victron kit bar the MPPT, then yes, you will need in line fuses.

[BargeeSpud]

The Victron Bluesolar is usually wired directly into the Victron Combi unit which will be connected through a shunt ( posh fuse) to your battery bank.

If you haven't got any other Victron kit bar the MPPT, then yes, you will need in line fuses.

You may well be right, but the installation instructions connect the panel to the controller & the controller direct to the batteries. No mention of shunts, fuses or combi units. I think I will get the definitive answer from Victron & post it on here.

[aread2]

The Victron Bluesolar is usually wired directly into the Victron Combi unit which will be connected through a shunt ( posh fuse) to your battery bank.

If you haven't got any other Victron kit bar the MPPT, then yes, you will need in line fuses.

I think if you were using the shunt as a fuse you'd be in trouble. Surely the shunt should also be protected by a fuse in the circuit.

[nicknorman]

The Victron Bluesolar is usually wired directly into the Victron Combi unit which will be connected through a shunt ( posh fuse) to your battery bank.

If you haven't got any other Victron kit bar the MPPT, then yes, you will need in line fuses.

Ahem! a shunt is not a posh fuse!

[mrsmelly]

Presuming you have a 12v system, 200w at 12v = 16.6A. In reality it is likely to be less than that due to

1/ the voltage under charge is likely to be nearer 13 than 12, or even more, so at 13v it would be 15.3A, at 14v 14.2A and

2/ it will be a rare day when you actually get 200W from the panels.

 

Therefore a 15A would be adequate most of the time, get a 20A if you want to eek every bit of current out of the panels or to allow for more panel in future. If you do go for a 15A one, check it handles too much panel power gracefully, for that rare day when the panels could put out more than 15A. I think MPPTs do in general, but best to check.

 

Hi Nick

 

Cheers for that. I will get a 20 then to make sure its on the game.

 

Tim

[Theo]

Where on the battery bank would you suggest the solar controller cables connect, in case the alternator cables are wrongly connected.

In what sense do you mean that the alternator cables could be wrongly connected?

 

N

[LankyStreak]

OK, I find this conFUSING!

 

My Victron BlueSolar MPPT 75/50 makes no mention of fuses anywhere in the installation instructions, so before I continue with the installation of 4 x 100w panels hooked up with 10mm2 cable, I think I need a little clarity on this. So to fuse or not to fuse, that is the question.

I've recently installed a pair of Victron BlueSolar 75/50 MPPTs (one to a 20W panel for the 12v engine starter battery, the other for a pair of 100W panels wired in series for my 24v cabin batteries).

 

The Victron MPPT instruction manual does mention fuses (here) and it comes with a replaceable 20A blade-type car fuse in the bottom beside the connectors. I used 4mm² cable which was excessive for the current of my installation.

 

Although you can of course wire the solar charge controller directly to the battery terminals I wired the -ve cable from the MPPT to my battery monitor shunt so that my Victron battery monitor (BMV-501) displays the charge/discharge current taking the solar panels into account, and saddo that I am I also wired these Chinese volt and ammeters into the circuit so that I can see at a glance when the panels are charging my batteries. They arrived very quickly by post from China and the instructions were in clear English. My mooring is under trees but even though it's only March my batteries have been receiving between 2 and 3 amps at 24v which keeps them charged despite a 24v fridge, water pump, LED lights, and an inverter for TV, phone charger, my wife's hair dryer (yeah I know), and occasional use of the microwave.

 

It's probably unnecessary with the Victron 75/50s but I added a fuse holder between the MPPT and the batteries and put in a 10A fuse, purely on the basis that it's unlikely ever to blow and if it does I'll stop and think about why.

[BargeeSpud]

OK, as promised, the answer to the fusing of the Victron 100/30 BlueSolar MPPT controller as obtained from Victron is:

 

"Fuses are installation requirements, so its always better to fuse your cable."

 

That was it, no ratings or where to place within the circuit. So why the chuffin' heck isn't that in the installation manual then!?

[valrene9600]

In what sense do you mean that the alternator cables could be wrongly connected?

 

N

Well the charge from alternator to battery should it seems be to a specific point on a battery bank. Someone might have wired it to a different point.

I guess like the way batts are connected the charge cables be they solar or alternator will be more efficient connected to a specific point on the bank.