Dont know if this will help anyone my sister has two panels that go through a controler and 10 mths of cable. The cable which is supplied by the company is 6mm I tested the output of the controller on low batteries and the output will vary with condition of charge in the batteries it was 12.5 volts at the controller and 11.4 at the end of the cable to batteries which is too low.The problem is the 6mm cable at that length has massive voltage drop I doubled the wires both + and - which makes it 12 mm each then rechecked the voltage to the batteries and it increased to 12.4v and increases as the batteries start to charge by the end of the day it was charaging 13.4 which is acceptable so the people selling these set ups really don't know how important it is to use the correct size cabling hopefully not all these companies make the same mistake.
Thanks for pointing that out. I guess it is a pair of folding panels with the controller mounted on the panels.
It has been said before and should be said again, that the controller(regulator) should be mounted close to the batteries. It will work 'twice' as good even with the same poor skinny wire. Even better with good heavier wire.
Finishing the day with the batteries at 13.4V will not be enough to keep her batteries going for long ! They should get to fully charged or will fail quickly.
I do believe most of these portable sets suffer the same problem crap design.
Fully agree with Jaahn on this one. Use 6 B&S cable between the controller and battery will give you the best results for a controller up to around 40 amps, after that you need even bigger cable. Nothing to do with voltage drop as such, it's to do with cable resistance and the controller sensing a higher voltage than the actual battery voltage when the system is charging. The aim is to see 14.4v before mid day if you are recharging lead acid batteries, that gives about 2 to 3hrs absorption charging tie and will get the battery closer to fully charged. Despite what many think, 14.4v charging is not fully charged, it is just the end of the bulk charge phase where constant current changes to constant voltage charging to get the last 20% or more into the battery
T1 Terry
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This is unfortunately a common problem with portable panels - putting the regulator on the back of the panels.
This is a bad idea, for 2 reasons:
First, the regulator's job is to look after the battery, not the panels - as the others have pointed out, it can't do that job properly when it's far away - there is the volt-drop that you measured yourself, and it's too far away to sense the battery voltage properly.
Second, it gets really hot on the back of the panels, and the electronics inside the regulator starts backing off to protect itself from over-heating - so you get less charge than you would if the regulator was in the shade. (some of the cheap regulators just overheat and burn out).
Both these reasons point in the same direction - we need to get the regulator close to the batteries, within a metre or so. If the regulator is stuck on, then we have 2 choices: either get a new one and just bypass the old one; or alternately increase the cable size, to bring the volt-drop between regulator and battery down to 0.1 or 0.2 Volts. There's a volt-drop calculator here http://12voltblog.com.au/volt-drop-calculator/ that you could use. You have 10 metres of cable, so for 10 Amps of charge you will need a really heavy cable around 14mm Auto or more (6B&S).
AJC
-- Edited by AJC on Thursday 9th of March 2017 03:35:49 PM
-- Edited by AJC on Friday 10th of March 2017 03:04:47 PM
Wiring is the problem with most things in caravans. (To a price)
Most panels need twice the thickness they supplied with.
and all the advice you need above.
With every van I've had a fridge in. That I didn't wire in myself.
I've Always doubled up another run of thick cable.
Usually under the van.
From an Anderson at drawbar to coupling under fridge where 12v comes into it
with other end of Anderson going to tug wing battery.
You'll be surprised the difference it makes in most cases.
The numbers MAY look ok . But over the distance ?? Not up to scratch .. I wired our panels in parallel and only 3m down through fridge vent in roof, where regulator is on top of fridge. . I had to fit links as max size to reg was around 6mm sq.. Plus 18v or so voltage is better than reg at solar panel with lower controlled voltage.. More efficient the closer to battery the better..
Hi
8mm/8b&s is absolute minimum size cable for solar
If the amps or the cable length go up so should the cable size .
Voltage drop murders recharge ability
There were some folding solar panels (do not remember the name), advertised as having extra long leads, to ensure you could put them further away from the vehicle, and away from the shade The leads appeared to my untrained eye, to be the same outer thickness as the normal length leads, on the other same size normal panels
I asked the salesman, would it not be better to have the regulator closer to the battery, instead of on the panels His answer was that they would not have made them like this, if they did not work
This tells me that the manufacturer had obviously made them to a price, and that the salesman believed his own sales pitch
The best method of testing the wiring between the solar panel and the battery when using a PWM controller is measure the voltage at the panel when the controller is in boost/bulk mode. It should be connecting the solar directly to the battery, perfect would be battery voltage at the solar panel but I doubt you would ever see that, but it needs to be less than 1v higher than the battery terminal voltage. Those with an MPPT controller, you are on your own I'm afraid as the MPPT controller sets the input voltage to match a preprogramed drop down chart where it thinks it can harvest the best ratio between input and output, this does not always match up with the max power point voltage of the panel at the time but that is another subject entirely :lol:
T1 Terry
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You can lead a head to knowledge but you can't make it think. One day I'll know it all, but till then, I'll keep learning.
Any links to any sites or products is not an endorsement by me or do I gain any financial reward for such links
The cable which is supplied by the company is 6mm . . Snip . .The problem is the 6mm cable at that length has massive voltage drop I doubled the wires both + and - which makes it 12 mm
No it probably does not. If your cable is 6 mm diameter over the insulation then you will probably only have 4 - 4.8 square mm of coper in the cable. When you double the wires that only makes it 8 - 9.6 square mm of copper conductor. You would be much better off getting the 6 gauge cable (13.2 mm2) that T1 recommended. Then also mount the controller near the battery. That will increase the battery charging performance much more than using larger cables than the 6 gauge cable.
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PeterD Nissan Navara D23 diesel auto, Spaceland pop-top Retired radio and electronics technician. NSW Central Coast.
