Solar Panel and the 50/75 amp Fuse.

[WelshGas]

This really only applies to the SE/Ocean that have 2 x Leisure Batteries.

The 2 Leisure Batteries are connected in Parallel with a 50/75amp Cube fuse between the rear battery and the +tve lead from the front battery. All the power take off for the Leisure circuits [ fridge, water, parking heater and lights/sockets ] come from the Front Battery.
If the 50/75amp cube fuse blows [ it is very fragile ] then the rear battery is disconnected and you reduce your onboard battery capacity by 50%. You will only know this has happened when your time off-grid plummets.

If you have a Solar Panel then it is normally wired onto the rear battery connector with the +tve lead from the front battery so it is then connected to the rear battery via the 50/75amp cube fuse.

If you use a voltmeter in a 12v Leisure Socket or even the Control Panel you will see the voltage rise when the Solar Panel is active. Unfortunately you will see the same voltage rise if the 50/75 amp cube fuse has failed.

However, if you wire the Solar Panel +tve lead underneath the 50/75 amp cube fuse or directly to the +tve pole of the rear battery you will Only see this voltage rise if the 50/75 amp cube fuse is fully functional, thus getting advanced warning.

There are a number of reasons the cube fuse can fail. It is a fragile ceramic block that is easily damaged by movement or over tightening . If it fails once it could be due to damage but 2 x in quick succession then it could be an electrical problem that needs sorting.

 

[Loz]

Good idea, but if you connect directly to the battery terminal, make sure there is a suitably rated fuse on your solar feed wire close to the battery terminal.

 

[WelshGas]

Good idea, but if you connect directly to the battery terminal, make sure there is a suitably rated fuse on your solar feed wire close to the battery terminal.

Yes there is a fuse close to the battery connection, as supplied in the kit from Roger Donahugh.

 

[Roger Donoghue]

The fused ring terminal we supply is designed to go on top of the cube fuse, but it can go below too.

I have suggested on top in the instructions as the plastic red nut has a guiding inner ring which pushes the spade connector (and the actual battery live cable connector) into the central position, not touching the central live "bolt". This is necessary for the cube fuse to function as it should (the battery live travels through the base of the cube fuse, up through the thin fuse element, and out through the top of the cube fuse. Anything touching the top of the cube fuse's outer ring now goes through the fuse before it reaches the battery, as intended)

If you place our ring connector under the cube fuse you will get the benefit of being able to see if it's blown, as per WelshGas's tip above - a very useful thing to know.

However, if you do this, make sure our ring terminal is fairly central and not touching the central inner main bolt. If it touches the cube fuse base (which it will), and also the central bolt (which it will if you are not careful), it will make a connection that negates the presence of the blade fuse entirely , which you don't want (or maybe you do! stupid things seem to blow for a past time).

Most of this won't make much sense unless you've seen the cube fuse. I might make a drawing.....

 

[Roger Donoghue]

Bit of a picasso.....

 

[WelshGas]

The fused ring terminal we supply is designed to go on top of the cube fuse, but it can go below too.

I have suggested on top in the instructions as the plastic red nut has a guiding inner ring which pushes the spade connector (and the actual battery live cable connector) into the central position, not touching the central live "bolt". This is necessary for the cube fuse to function as it should (the battery live travels through the base of the cube fuse, up through the thin fuse element, and out through the top of the cube fuse. Anything touching the top of the cube fuse's outer ring now goes through the fuse before it reaches the battery, as intended)

If you place our ring connector under the cube fuse you will get the benefit of being able to see if it's blown, as per WelshGas's tip above - a very useful thing to know.

However, if you do this, make sure our ring terminal is fairly central and not touching the central inner main bolt. If it touches the cube fuse base (which it will), and also the central bolt (which it will if you are not careful), it will make a connection that negates the presence of the blade fuse entirely , which you don't want (or maybe you do! stupid things seem to blow for a past time).

Most of this won't make much sense unless you've seen the cube fuse. I might make a drawing.....

In case that happened, as the bolt on the Pole Clamp snapped and I had to replace it, I’ve put the fused Solar Panel ring connector on that bolt to avoid that possibility.

 

[Azteccamper]

Anybody know where I can pick up one of those red nuts on the +ve terminal of the rear leisure battery?

 

[Loz]

Isolation Nut for Fused Battery Terminal Clamp

Isolation nut for fused battery terminal clamps. Prevents the ring terminal from making contact with the stud and ensures all current flows through the fuse.

www.12voltplanet.co.uk

Here is a better clamp that goes to the rear of the battery where there is more room, this makes it easier to remove the battery. It also uses a better nut that does shatter.

Ceramic Cube Fuse & Battery Terminal Holder - Heavy Duty Main Fuse 50-300A | eBay

Product Information. Excellent Service. Width (mm): 30. The item is your responsibility until it reaches us. Credit Card Security. We do not issue any extra hidden costs.

www.ebay.co.uk

 

[Azteccamper]

Isolation Nut for Fused Battery Terminal Clamp

Isolation nut for fused battery terminal clamps. Prevents the ring terminal from making contact with the stud and ensures all current flows through the fuse.

www.12voltplanet.co.uk

Here is a better clamp that goes to the rear of the battery where there is more room, this makes it easier to remove the battery. It also uses a better nut that does shatter.

Ceramic Cube Fuse & Battery Terminal Holder - Heavy Duty Main Fuse 50-300A | eBay

Product Information. Excellent Service. Width (mm): 30. The item is your responsibility until it reaches us. Credit Card Security. We do not issue any extra hidden costs.

www.ebay.co.uk

Many thanks. Really appreciate that. Just bought the cube fuse from 12voltplanet and then cracked nut putting it on terminal! It’s the postage that adds up.
I have also got a solar panel connection to the +ve terminal.
Can I ask @Loz @WelshGas what would happen if the +ve cable connections made contact with the central bolt bypassing the cube fuse?

 

[Loz]

Nothing would happen until you had a fault on either cable that required the fuse to blow and your cable tried to behave like a bigger fuse.
If your thin wire is not fused and it shorted to the chassis some distance away from the battery, it could heat up red hot with hundreds of amps and cause a fire, that’s what fuses are there to protect.

 

[Azteccamper]

Nothing would happen until you had a fault on either cable that required the fuse to blow and your cable tried to behave like a bigger fuse.
If your thin wire is not fused and it shorted to the chassis some distance away from the battery, it could heat up red hot with hundreds of amps and cause a fire, that’s what fuses are there to protect.

Again, many thanks. Solar wired is fused about 6” from battery so hopefully all good to go.

 

[Roger Donoghue]

Many many a van I work on has a faulty ceramic nut meaning the fuse has been bypassed for a long time. It's usually the thin bottom ring on the cermic nut that breaks - the bit the keeps the connector and bolt electrically seperated. One would hope that the fuse at the other end (under the pass seat) would blow in the event of a short. Fusing at both ends of a high current wire is usually preferable to minimise cable melting risk.

 

[WelshGas]

Many many a van I work on has a faulty ceramic nut meaning the fuse has been bypassed for a long time. It's usually the thin bottom ring on the cermic nut that breaks - the bit the keeps the connector and bolt electrically seperated. One would hope that the fuse at the other end (under the pass seat) would blow in the event of a short. Fusing at both ends of a high current wire is usually preferable to minimise cable melting risk.

On the California there is only the 1 fuse on the rear battery.

 

[Loz]

@WelshGas is correct that there is only one fuse, and the small cable is not protected if not fused as the other end of the large cable feeding the second battery directly connects to the first battery (at the battery side of the 80A fuse).
(FYI, that drawing is incorrect in the earthing arrangement, as the shunt is in the earth cable, not the return from the consumers)

 

[marchugo]

FYI: in our Cali T5.1 it looks like this in the plus pole region of the rear battery, with solar cables:


The plus cable labelled 'Solar' (going North-East) comes from a 120 Wp solar panel on the roof of the van. It is fused with 15A (in the little grey box).
As you can see, it's directly connected to the plus pole, so bypassing the 70A block fuse with the red nut on top.

(The cables going South are for connecting a second foldable mobile solar panel of 120 Wp outside the van, both fused with 15A. One has an Anderson connector, the second an SAE connector. Both can be used to feed in (solar) and feed out (e-bike loading) of the battery.)

Regards from Amsterdam,

Marc.