What size cable,I have 2 currently at 115ah,and am thinking I need a third or, have I got too thin a cable,solar controller panel to first one is 7’ then to second is 9’,if I add a third it will sit next to second. Currently using 2mm od,across insulation,tiny,but then it doesn’t even get warm.thanks.
- Thread starter nickk
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That wire does sound too thin.
Even if it's modern thin wall automotive wiring, at that OD it'll be 1mm2, and although technically good for 18A, voltage drop over that length is likely to be an issue.
If it's conventional thickness wiring, then it's probably 0.75mm2 or less and only good for less than 8A.
You really need to look at how much current your solar panels/controller are outputting.
Even if it's modern thin wall automotive wiring, at that OD it'll be 1mm2, and although technically good for 18A, voltage drop over that length is likely to be an issue.
If it's conventional thickness wiring, then it's probably 0.75mm2 or less and only good for less than 8A.
You really need to look at how much current your solar panels/controller are outputting.
Barking Mat
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35mm2 can't go wrong, we use it everywhere on boats, starter motors, charging systems, etc, etc, etc.
No voltage drop.
25mm2 would probably be overkill for your van, how bigs the alternator ?
No voltage drop.
25mm2 would probably be overkill for your van, how bigs the alternator ?
Barking Mat
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How much do you need ? What lengths ? We've loads in a bin.
Measure all the runs of cabling, add some more, just to be sure, let me know.
Measure all the runs of cabling, add some more, just to be sure, let me know.
Thanks for the replies,it maybe beyond my abilities,the panel is 170w at max,the cables feeding the controller are about 4.5mm od,I’ve since moved some cables so that the fridge is supplied from the nearest battery,2’ away,I assume the cables are carrying max 14amp.
@Barking Mat no alternator they’re only fed from solar.
@Barking Mat no alternator they’re only fed from solar.
I'm guessing the batteries are not installed near each other?
As long as you're not powering anything major from the batteries and never charging them from an alternator, you could probably get away with linking the batteries together using 6mm2 wire which is good for over 40A.
For the rest of the wiring, I'd probably go for 2 or 2.5mm2. That's good for over 20A, and will avoid any voltage drop issues.
However, I get the feeling that you've not really designed this system as such, just added bits to try and get something that will achieve what you'd like it to?
If that is the case, I'd probably suggest starting again, and design a system that will manage what you want it to do, instead of throwing parts at the existing system.
As long as you're not powering anything major from the batteries and never charging them from an alternator, you could probably get away with linking the batteries together using 6mm2 wire which is good for over 40A.
For the rest of the wiring, I'd probably go for 2 or 2.5mm2. That's good for over 20A, and will avoid any voltage drop issues.
However, I get the feeling that you've not really designed this system as such, just added bits to try and get something that will achieve what you'd like it to?
If that is the case, I'd probably suggest starting again, and design a system that will manage what you want it to do, instead of throwing parts at the existing system.
What's the power rating of the fridge?
Barking Mat
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6mm cables to fridge and batteries will suffice, I've loads of spare cabling if you need it.
Misterg
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One of the CRX ones?
I'd look to your solar, as well as the batteries. 160W will keep our 40W CRX50 running 24/7 from March to October with minimal battery drain, even in the UK.
Even assuming the fridge is running 24hrs, that's 960Whr (40W x 24hr) per day.
Given you're using this in the height of summer, even if the panels are only running at 50% efficiency for 12hrs of the day, they should still be outputting 1020Whr (85W x 12hr), but I'd expect them to be outputting a lot more than that, so even allowing for inefficiencies, they should be more than capable of keeping the fridge running.
I'd upgrade the wiring between the batteries to at least 6mm2, and at least 2.5mm2 from the solar controller.
I'd then check what current the solar panels are outputting, and what the voltage is at the batteries. Also check the solar controller is set for the correct type of battery.
I'd also suggest getting the batteries tested with a good modern battery tester, however leisure batteries often don't have a cranking amp rating, which means you can't reliably test them with most modern capacitive discharge tester (you do get more basic ones that'll estimate the Ah rating of the battery, but good quality testers rely on the battery cranking amp rating being entered).
If your batteries do have a CCA/EN/SAE/DIN current rating written on them, then find a local garage or motor factor who have a digital tester, and get them tested.
Given you're using this in the height of summer, even if the panels are only running at 50% efficiency for 12hrs of the day, they should still be outputting 1020Whr (85W x 12hr), but I'd expect them to be outputting a lot more than that, so even allowing for inefficiencies, they should be more than capable of keeping the fridge running.
I'd upgrade the wiring between the batteries to at least 6mm2, and at least 2.5mm2 from the solar controller.
I'd then check what current the solar panels are outputting, and what the voltage is at the batteries. Also check the solar controller is set for the correct type of battery.
I'd also suggest getting the batteries tested with a good modern battery tester, however leisure batteries often don't have a cranking amp rating, which means you can't reliably test them with most modern capacitive discharge tester (you do get more basic ones that'll estimate the Ah rating of the battery, but good quality testers rely on the battery cranking amp rating being entered).
If your batteries do have a CCA/EN/SAE/DIN current rating written on them, then find a local garage or motor factor who have a digital tester, and get them tested.
Barking Mat
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Leisure batteries are difficult to properly test, we have a 700 quid box which puts a variable resistance load on them over hours, to give a true result.
Even then, it says some batteries are good, who promptly die, so I have my doubts, but we are plagued with two pallets of rubbish batteries, over the last two years, thousands of euros worth which have lasted months, not years....
MetalMonkey
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Do you mean panel voltage? Current is measured in Amps, not Volts...
I think it is worth clarifying the terminology here. Voltage is volts, Current is Amps. Voltage current is not a thing, although volt-amps are but not, I suspect, what you are referring too.
Farside
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He's not done it yet, so doesn't know what he's talking about.
Not stated in the handbook sorry.
MetalMonkey
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I comprendez, my question was, do you?
Charge may flow into a battery at a potential difference of 14.4V. Current won't be at 14.4V because current is in Amperes, not Volts.
Your solar controller might output 14.4 volts.
The current which it supplies to the charge circuit at that voltage will be dependant on its input - which is dependant on the operating voltage and current output of the solar panels, which in turn is dependant on the light input.
That takes us back to:
The solar controller won't "drop panel current to voltage". It is a DC-DC convertor and what it will do (assuming it has MPPT capability) is optimise the load presented to the panel to develop the maximum power from the panel as its voltage and current alters depending on the conditions. The output from the panels should be operating at a higher voltage than the controller supplies to the charging circuit. This should produce more current on the charge output, not less. Capisce?
