Help needed please, new member.

[Faggy]

Hi, I am new to solar. I have a Victron 175w panel connected to a Victron MPPT 75/15 controller by 5m of Solar Panel PV cable 4mm & 6mm.
I have 2 questions, what cable should I use between the MPPT and the EXV110AGM Enduroline AGM 95Ah Leisure Battery and should I include and if so what size fused circuit breaker. Totally confused by all the reading I've done.

 

[Samsonite801]

So the Victron 75/15, means, 75v is maximum PV volts allowed on the PV side, and the 15 means, 15a battery charger output is possible on the battery cable side. So 15a requires at minimum a 14 AWG cable, but 12 AWG would be better, and longer lengths should be even larger for less loss. How long of a cable run is it? Cable gauge calculator website exist where you can figure in length, and the fuse or breaker should be sized to protect the gauge of the battery wire so it can't meltdown if over-current is reached...

 

[Faggy]

Thanks Samsonite801, distance is no more than 30cm, 12awg with a 15a fuse/breaker?

 

[Samsonite801]

Sure no prob at all.. Cool, so if you used a 12 AWG cable, you could use a 20a fuse to protect it...

 

[Faggy]

Thanks again, brilliant

 

[12VoltInstalls]

Sure no prob at all.. Cool, so if you used a 12 AWG cable, you could use a 20a fuse to protect it...

Except I might still use 8ga for the charging cable. Upgrade headroom and it will never get warm. Ever?

 

[Faggy]

Except I might still use 8ga for the charging cable. Upgrade headroom and it will never get warm. Ever?

Sure no prob at all.. Cool, so if you used a 12 AWG cable, you could use a 20a fuse to protect it...

How does this look please

 

[12VoltInstalls]

Looks functional. Novel way to perform circuit protection on the charging wire, but I think a properly sized fuse at the battery itself is still needed. It would protect everything if “something bad” happens and the battery winds up crash-bleeding to a grounded item.

I might not want an agm but if your battery is going to be in a residence that could be a good compromise.

 

[Faggy]

Looks functional. Novel way to perform circuit protection on the charging wire, but I think a properly sized fuse at the battery itself is still needed. It would protect everything if “something bad” happens and the battery winds up crash-bleeding to a grounded item.

I might not want an agm but if your battery is going to be in a residence that could be a good compromise.

I am open to suggestions to make this better/safer please. The battery is in situ and grounded. where and what size fuses would you use please?

 

[Faggy]

I am open to suggestions to make this better/safer please. The battery is in situ and grounded. where and what size fuses would you use please?

 

[Just John]

Thanks Samsonite801, distance is no more than 30cm, 12awg with a 15a fuse/breaker?

10 AWG is easy and cheap to find, as well as having lots of crimp connectors readily available. 20 amp breaker, the breaker is to protect the wire. 10 gauge is rated for more than 15 amps, and you don't want the breaker tripping just because you actually got 15 amps for an extended time. 10 AWG because why just do the bare minimum when for 30 cents more you can do better.

The primary question about wire is "will it be exposed to the elements like sunlight and rain".

 

[camelCase]

Your solar may only provide 15 amps of current for charging, but you will likely want to pull a lot more than 15 amps of current from the battery based on your loads. You need to size the wires from the battery to your fuse block based on that. There should be a fuse between the battery and the load that should be sized so that the wire between the battery and the load cannot be damaged.

Edit: if the load will be 37 amps or less, you can run 6mm wire on the battery side. I would prefer a fuse or circuit breaker on that wire close to the battery. You can use 4mm wire to connect the charge controller to the battery.

 

[Just John]

Your solar may only provide 15 amps of current for charging, but you will likely want to pull a lot more than 15 amps of current from the battery based on your loads. You need to size the wires from the battery to your fuse block based on that. There should be a fuse between the battery and the load that should be sized so that the wire between the battery and the load cannot be damaged.

Edit: if the load will be 37 amps or less, you can run 6mm wire on the battery side. I would prefer a fuse or circuit breaker on that wire close to the battery. You can use 4mm wire to connect the charge controller to the battery.

I was wondering the same thing myself. The wire from the battery to the fuse box should obviously be sized and fused for the total load, not based on how many amps the charge controller can supply. It is best to think of them as two separate circuits. For the solar panel, he should select photovoltaic rated wire, and again, I would recommend paying the extra for 10 gauge copper wire rather than saving money and getting 12 gauge aluminum wire. If he hasn't already bought it, there are lots of decent 100 amp hour LFP batteries on Amazon for around $350 to $400. This would actually give him nearly twice the usable capacity and longer life. But for really basic solar setup that he seems to be building, AGM is also a good choice.

 

[Faggy]

Hi all, thanks for your help. I have all the equipment in the diagram. I was sold 5m of 4mm PV cable or 12AWG. This will run from the panel for 5m to the charge controller. Total load is small I believe, 4 LED lights, radio and various USB for phone charging. The main reason for installing the panel is to be able to run a 12v coolbox throughout the day or with a 12v timer on and off during the day, this uses about 3.75 Ah. So I think the if everything was on it is still a small load, correct me if wrong.
I also understand 10AWG might not fit into what look like very small conections on the 75/15 MPPT.

 

[camelCase]

Hi Faggy, 4mm wire should be fine for that small load and for a 15A charge controller.

 

[12VoltInstalls]

also understand 10AWG might not fit into what look like very small conections on the 75/15 MPPT.

Im not certain- don’t have any victron- but I think that will handle to 8ga; 10 will be good.

 

[Faggy]

If at first you don't succeed, then try again. With help from the comments above and a little overnight research I am hoping this is better? Thanks.

 

[Just John]

If at first you don't succeed, then try again. With help from the comments above and a little overnight research I am hoping this is better? Thanks.

You have a 12 gauge wire going from the battery to the fuse box with a 40 amp fuse. The fuse should be sized to protect the wire, and I'm pretty certain that 40 amps is too high for 12 gauge. 8 gauge would be a better choice going from the battery to the fuse box, or at least 10 gauge.

 

[12VoltInstalls]

You have a 12 gauge wire going from the battery to the fuse box with a 40 amp fuse. The fuse should be sized to protect the wire, and I'm pretty certain that 40 amps is too high for 12 gauge. 8 gauge would be a better choice going from the battery to the fuse box, or at least 10 gauge.

Ya, 10 gage is generally 30A, 8 ga would work for 40.

I overcable these typically short runs a LOT and would probably use 6ga. Actually now that I wrote that I realized my panel disconnects/breakers feed the current AIO with 6ga and I think I limited at 40A max.

 

[Faggy]

You have a 12 gauge wire going from the battery to the fuse box with a 40 amp fuse. The fuse should be sized to protect the wire, and I'm pretty certain that 40 amps is too high for 12 gauge. 8 gauge would be a better choice going from the battery to the fuse box, or at least 10 gauge.

It will be UK 4mm which is rated 33amps I believe