Adding solar to an old 99 motorhome.... (1 Viewer)

[GaryGavlaar]

Just going down the path of adding a victron solar panel and controller to my 99 Bessacarr E695

The solar panel will be at the back of the motorhome and the leisure battery is right at the front under the passenger seat. I remember from my small van buld year ago the idea was to just introduce the solar power from the controller to the 12v system, not necessarily needing to be connected at the battery itself (wire size and fuses permitting).

The cables I think will be coming down into the cupboard where the battery charger and consumer unit is housed. Would i be able to tap into the cables that are running from the battery charger or distro panel to the leisure battery, or am i best running a fresh cable to the battery along side the ones already running the same route?

Just conscious of how some of the relays work and if i will effect that in any way?

See wiring diagram below (ignore the red circle, that was for a previous post)

 

[GeoffnDee]

That diagram shows a plug-in-systems KT12 charger/PSU and I believe you have a Zig charger at the moment so the charger may have been changed , is it possible that the wiring has also been altered ?

 

[GaryGavlaar]

That diagram shows a plug-in-systems KT12 charger/PSU and I believe you have a Zig charger at the moment so the charger may have been changed , is it possible that the wiring has also been altered ?

From my investigation the wiring seems to be the same..... Is there a major difference between a KT12 and a zig x80? I certainly haven't changed anything but previous owners may have replaced a faulty charger I guess. I've not seen any extra wiring that differs (colour wise) from what's in the diagram so far.

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[GeoffnDee]

I do not know what the difference is between the Zig unit you have and the original Plug-in-systems unit but they have different listings in the apuljack catalogue. The diagram seems to show the charger being linked to the EMC relay so I think it may be better to connect your solar to your leisure battery.

 

[paddymcc]

If you connect it to the output from the charger there's a risk that the wire size won't be adequate. It has a 20A fuse so the combined current from the charger and the solar controller would have to be less than this. So that will depend what size solar controller and panel you go for. It's probably best to run new wires. Then at least you will know that you are using the right size wire. If doing so you may want to oversize in case you get a second panel at a later date

 

[GaryGavlaar]

If you connect it to the output from the charger there's a risk that the wire size won't be adequate. It has a 20A fuse so the combined current from the charger and the solar controller would have to be less than this. So that will depend what size solar controller and panel you go for. It's probably best to run new wires. Then at least you will know that you are using the right size wire. If doing so you may want to oversize in case you get a second panel at a later date

I've always wondered about this, as in, if you were plugged into leccy hookup during the day and it was nice and sunny, do the two literally both power to charge the battery or is there not some intelligence? Same while driving on a sunny day too, alternator and solar powering the 12v circuit.

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[Itsmcb]

I've always wondered about this, as in, if you were plugged into leccy hookup during the day and it was nice and sunny, do the two literally both power to charge the battery or is there not some intelligence? Same while driving on a sunny day too, alternator and solar powering the 12v circuit.

I would imagine that depends on the state of charge of your battery and its ability to absorb charge. If its low on charge and can accept for example 30amps per hour and your charger can only output 20 amps then the solar would supply the other 10amps giving 30 amps flowing along the cable which may only be rated at 20 amps. If that makes sense.

 

[GaryGavlaar]

I would imagine that depends on the state of charge of your battery and its ability to absorb charge. If its low on charge and can accept for example 30amps per hour and your charger can only output 20 amps then the solar would supply the other 10amps giving 30 amps flowing along the cable which may only be rated at 20 amps. If that makes sense.

Interesting. How do we know how many amps a battery will accept? Is that in the spec somewhere?

 

[paddymcc]

Interesting. How do we know how many amps a battery will accept? Is that in the spec somewhere?

Different types of batteries can cope with different charge rates. Lead acid is I think generally quoted as about 20% of its capacity, so if a 100Ah battery it can safely take 20A. A lithium battery can cope with much more, hence it's versatility as you can charge at a much faster rate without damaging it.

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[The Wino]

I'm no expert but would have thought that the amount of solar that you're thinking of adding would have an effect on what cabling to run. If your talking about say a 100w panel it will be different to 450. You can then do a voltage drop calculation and look at the existing wiring size. On the panel size it depends why you're fitting it. If like us you seldom get close to a flat leisure battery and travel most days the panel could be relatively small as a top up. If you're thinking of using an Inverter off grid in winter you might need a huge one and more batteries.

 

[GaryGavlaar]

I'm no expert but would have thought that the amount of solar that you're thinking of adding would have an effect on what cabling to run. If your talking about say a 100w panel it will be different to 450. You can then do a voltage drop calculation and look at the existing wiring size. On the panel size it depends why you're fitting it. If like us you seldom get close to a flat leisure battery and travel most days the panel could be relatively small as a top up. If you're thinking of using an Inverter off grid in winter you might need a huge one and more batteries.

I think it's more the solar controller isn't it? So if my solar controller is rated at 15 amps then thats the max it's gonna pump out to the battery? Or is that wrong?

 

[The Wino]

I think it's more the solar controller isn't it? So if my solar controller is rated at 15 amps then thats the max it's gonna pump out to the battery? Or is that wrong?

It can only put out to the battery what the solar puts in. Generally you size the controller so it can cope with the maximum the panels can put out plus a bit for comfort. The voltage between the panel and controllers is higher than the 13v between the controller and battery so you usually have the long cable run from the panel to the controller and put the controller as near as possible to the battery. In our case we only wanted a top up from the solar as we drive almost every day and never had a flat leisure battery with no solar so I just put on a 100 w panel with the controller near it and fed into the pre installed solar wiring. If I had wanted a large amount of solar for say an inverter with a hairdryer microwave etc I would have had a big amount of solar with thick cables to a controller next to the battery. The bigger the amount of solar the more sense it makes to feed nearer to the battery as the voltage in the solar to controller circuit is higher

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[headlight]

GaryGavlaar Yes if your solar controller is rated at max 15amps then that is the most it will supply the battery with.
In UK summer you would need over 200 watts of solar to provide 15 amps.
I would wire up your solar, panel to MPPT to battery avoiding your present wiring.
12 volt planet have a cable sizing guide showing voltage drop dependant on length of run and cable diameter.
General rule of thumb is to aim for no more than a 3% drop.
What wattage panel are you adding ?

 

[GaryGavlaar]

GaryGavlaar Yes if your solar controller is rated at max 15amps then that is the most it will supply the battery with.
In UK summer you would need over 200 watts of solar to provide 15 amps.
I would wire up your solar, panel to MPPT to battery avoiding your present wiring.
12 volt planet have a cable sizing guide showing voltage drop dependant on length of run and cable diameter.
General rule of thumb is to aim for no more than a 3% drop.
What wattage panel are you adding ?

Thanks for ths info. Its a Victron 175w panel

 

[headlight]

Thanks for ths info. Its a Victron 175w panel

On a good UK summer's day that should provide up to about a max of 11 amps per hour and between about 50-70amps total in a day depending on how clear the sky is and that it is sunny all day.

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[autorouter]

If you need to locate the solar controller some distance from the batteries, some solar controllers have a method of sensing the battery voltage, and will push up the output voltage to compensate for any voltage drop, so the battery always gets the correct voltage. Some have a pair of thin sense wires that run alongside the thicker power wires. The Victron BlueSmart ones can pair with a Victron SmartSense device that sticks on the battery, and transmits the voltage and temperature data over Bluetooth. So no need for any sense wires. If you already have a Victron SmartShunt, that will do the same.

 

[GaryGavlaar]

If you need to locate the solar controller some distance from the batteries, some solar controllers have a method of sensing the battery voltage, and will push up the output voltage to compensate for any voltage drop, so the battery always gets the correct voltage. Some have a pair of thin sense wires that run alongside the thicker power wires. The Victron BlueSmart ones can pair with a Victron SmartSense device that sticks on the battery, and transmits the voltage and temperature data over Bluetooth. So no need for any sense wires. If you already have a Victron SmartShunt, that will do the same.

Victron.... They've got everything covered haven't they! I can see this getting expensive

I've gone for the Bluetooth victron 75/15 mppt controller. Now you're gonna have me looking at more gadgets. :⁠-⁠)

 

[headlight]

Victron.... They've got everything covered haven't they! I can see this getting expensive

I've gone for the Bluetooth victron 75/15 mppt controller. Now you're gonna have me looking at more gadgets. :⁠-⁠)

Same controller I use with 2x100 watt panels
I also have a Victron Smart Shunt but my B2B is a Sterling unit.

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[headlight]

GaryGavlaar These are my Smart Solar and Smart Shunt status pages as of now.
I'm parked on a site, it's very gloomy and drizzling and I'm not powering anything electrical at the moment.

 

[GaryGavlaar]

What is the main purpose of a shunt? I've seen them mentioned but never fully looked into them?

 

[headlight]

What is the main purpose of a shunt? I've seen them mentioned but never fully looked into them?

Shows you battery state of charge, voltage, what is going in to your leisure batteries, what is coming out of them and amount of time you have left power wise at that particular amount of drain.

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[GaryGavlaar]

Shows you battery state of charge, voltage, what is going in to your leisure batteries, what is coming out of them and amount of time you have left power wise at that particular amount of drain.

Doesn't the mppt controller tell me most of that though?

 

[headlight]

What is the main purpose of a shunt? I've seen them mentioned but never fully looked into them?

I've just plugged my phone in to charge and this is what my Shunt is now showing.

 

[headlight]

Doesn't the mppt controller tell me most of that though?

Most but not all.
The shunt shows everything going in to the batteries not just solar but alternator charging ( split charge or B2B) and mains charging if you're on hook up.
It also shows you the amount of time you have remaining at whatever drain is on the batteries at the time.
It's just more information if you're that way inclined.

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[GaryGavlaar]

Most but not all.
The shunt shows everything going in to the batteries not just solar but alternator charging ( split charge or B2B) and mains charging if you're on hook up.
It also shows you the amount of time you have remaining at whatever drain is on the batteries at the time.
It's just more information if you're that way inclined.

We all love a good but of info!

 

[autorouter]

A shunt fits on a battery terminal, usually the negative one, and measures amps. It also has a clock and microchip, and keeps a count of the amp-hours going into and out of the battery. To do this, all the amps into and out of the battery must be channelled through the shunt. It is a much better way of showing the state of charge (SOC) of the battery than just measuring the voltage. The shunt can also measure voltage and temperature. There are various models. Victron do them with a wired display module (BMV types) or Bluetooth the data to a phone app (SmartShunt).

The difference between the Smart Battery Sense and the SmartShunt is that the Smart Battery Sense doesn't measure amps, but is a lot less expensive.

 

[headlight]

Yes Smart Sense is about £35-£40, Smart Shunt just over £100.
With a Smart Shunt, or I assume a Smart Sense does the same, by turning individual items on you can see exactly how much that item uses rather than what the maker claims it uses, which are often very different.
For example my TV, run from an inverter, uses less than what the maker states but my portable hi-fi uses more.

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[headlight]

GaryGavlaar I've now got my 24' mains TV on run from a 300 watt (continuous) inverter plus a signal booster. As you can see total draw is only 2.5 amps per hour.
I have 2 days 11 hours at this drain with no charging before I use 50% of my batteries.
It's pouring with rain, very dark and solar is doing nothing