12V Transformer

Londonboii said:
So on the battery link cable I would place 2 100a fuses. A fuse before each battery positive terminal?

The cable is about 200mm long. I'm not sure there's space.

I will look for a midi fuse block. I'll have to work out what size fuses to get for each connection. I see in that image he has 100a on a 120a vsr, and 40a on a 30a solar controller. Yet the cables look to be the same size.

The krieger cables are really thick. The fuse is large also and I think it is 150a but I will check.


Fusing is confusing.
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Ref battery to battery cable, I did say "SHOULD BE FUSED AT BOTH ENDS, unless they are right next to each other, in which case there should still be a fuse, but just one central one is ok. "

There is a minimum cable size, but not a maximum. I probably use 16mm2 cable on all the connections for convenience in that fusebox. You fuse to below the maximum current carrying ability of the cable and above the maximum continuous rating of the device. There are two aspects to the right cable. One is that it can carry the current and the other that you minimize the voltage drop.
For fuses, in the case of the VSR, we do not expect that Victron device to ever deliver close to the maximum 120A rating (that would mean around 3,000 Watts out the Alternator) so a cable that is rated at 110A was fine, but it meant we fused below that rating for safety.

Sounds like the Krieger cables may be decent then. That is good.
 
Thanks.

I will get one of the midi fuse panels. I'll look into the fuse ratings a bit more and see if I can work out what fuses I'll need.

As well as being safer it will also help neaten it all up. Currently having the connections all attached to the battery terminal does look untidy and at the time I wasnt sure it was the best way to go.
 
Londonboii said:
I see in that image he has 100a on a 120a vsr, and 40a on a 30a solar controller.
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The rule of 50% more than the maximum current applies. A 30A solar controller is probably fitted to 250 watts of solar panels, so the maximum current that will flow is about 20amps. Maybe 300 watts, 25amps.
The VSR is a bit different. The rating of the relay is pretty unimportant. What matters is the likely peak current.
When driving, it'll be no more than 20a, dropping to 10a after a while, but the initial inrush current when you've started the engine with a well-charged starter battery and a low hab battery could be considerable, limited by the resistance of the circuit.
That's why makers use fairly thin cables: it's not being cheapskate, it's protecting the batteries from damage.
Personally, I'd fit a 70a fuse there, but 100a is not unreasonable.[/QUOTE]
 
in h said:
The rule of 50% more than the maximum current applies. A 30A solar controller is probably fitted to 250 watts of solar panels, so the maximum current that will flow is about 20amps. Maybe 300 watts, 25amps.
The VSR is a bit different. The rating of the relay is pretty unimportant. What matters is the likely peak current.
When driving, it'll be no more than 20a, dropping to 10a after a while, but the initial inrush current when you've started the engine with a well-charged starter battery and a low hab battery could be considerable, limited by the resistance of the circuit.
That's why makers use fairly thin cables: it's not being cheapskate, it's protecting the batteries from damage.
Personally, I'd fit a 70a fuse there, but 100a is not unreasonable.
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Actually, there are a pair of BiFacial Panels with a native capacity of 620W and a potential maximum of 800W connected to that 30A Solar Controller ;)
 
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in h said:
Just goes to show that the panels aren't giving of their best set up like that. Should be enough to blow the fuse.
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Really? not at all :p

I will let you ponder the reason why ;) (the clue IS in the photo)
 
PS. with the 30A controller, the controller would blow up before the fuse went if the rated current was exceeded.
 
A 12volt transformer will only transform the 230volt mains to 12volt AC. You system needs 12volts DC, so a 12volts DC power supply is what you need this will change the 230volts AC mains supply to 12volts DC.
 
David Tester said:
A 12volt transformer will only transform the 230volt mains to 12volt AC. You system needs 12volts DC, so a 12volts DC power supply is what you need this will change the 230volts AC mains supply to 12volts DC.
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In common use terms, when someone talks about a 12V transformer, they are talking about a device that converts an AC input into a 12V DC output. The same is true of people selling "12V Transformers".
If you needed a new lamp because the one you had failed, what do you think would happen when you go to the shop and ask for a lamp? chances are you would be asked if you want a table lamp? or a floor lamp? I doubt you would be asked what wattage of lamp you needed unless you asked for a bulb. Bulb is not the right term, lamp is, but everyone used the incorrect term "bulb" when they really mean the lamp that goes onto/into the fitting.
No need for be overly pedantic.
 
wildebus said:
PS. with the 30A controller, the controller would blow up before the fuse went if the rated current was exceeded.
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Allied question. If you had a panel that exceeded the capacity of the controller, wouldn't the controller simply limit the current to what it could handle, rather than blow up through passing too much?
After all, the primary function of the controller is to set a limit on what passes through it.
 
in h said:
Allied question. If you had a panel that exceeded the capacity of the controller, wouldn't the controller simply limit the current to what it could handle, rather than blow up through passing too much?
After all, the primary function of the controller is to set a limit on what passes through it.
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Depends on the controllers generally.
Excess Voltage can often be Terminal (some controllers have protection and shut down, but it is an aspect I don't care to test generally!)
Excess Current on the INPUT can still often be terminal (the Victron 100/30 must not exceed 35A for example).
Excess Current on the OUTPUT is usually limited/capped at the rated value without any damage

So to take the aformentioned controller ... Input Voltage is rated at 100V; Input Current is rated at 30A - so you could, in theory with those numbers, fit 3000W of PV Panels to the controller - but there would be little point as it is also rated at either 440W or 880W so as not to exceed the Output Voltage and Current combination. But if you DID fit more wattage, it would not cause any damage, you would just waste the excess.
(my comment on "Blowing up" should not be taken literally, but at the same time, taking the aforementioned one again in 'my' installation, it is supporting the full potential 800W without any capping on the output).
 
wildebus said:
Depends on the controllers generally.
Excess Voltage can often be Terminal (some controllers have protection and shut down, but it is an aspect I don't care to test generally!)
Excess Current on the INPUT can still often be terminal (the Victron 100/30 must not exceed 35A for example).
Excess Current on the OUTPUT is usually limited/capped at the rated value without any damage

So to take the aformentioned controller ... Input Voltage is rated at 100V; Input Current is rated at 30A - so you could, in theory with those numbers, fit 3000W of PV Panels to the controller - but there would be little point as it is also rated at either 440W or 880W so as not to exceed the Output Voltage and Current combination. But if you DID fit more wattage, it would not cause any damage, you would just waste the excess.
(my comment on "Blowing up" should not be taken literally, but at the same time, taking the aforementioned one again in 'my' installation, it is supporting the full potential 800W without any capping on the output).
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The problem with solar is that if you size for winter, you have too much in summer.
 
in h said:
The problem with solar is that if you size for winter, you have too much in summer.
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That is very true. (is that in relation to 'my' 800W setup on the 30A controller? still not worked out how it harvests the full 800W?)
 
wildebus said:
That is very true. (is that in relation to 'my' 800W setup on the 30A controller? still not worked out how it harvests the full 800W?)
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Never even given it a moment's thought. 800 watts at 30A is about 26 volts, which is what you'd expect to be charging 24v batteries.
 
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