Hi all, at present I'm running 2 batteries in van and have just purchased a 120 watt set of portable panels. The reg is on the panels and 15 mitres of cable from there to one battery .when I bought the van it had one battery so I added another, is it better for reg to be close to batteries not on panels ?
It is better for the reg to be closer to the battery, this means that the voltage moving from the panels to the batteries is a higher voltage which results in less loss, and the voltage only gets lowered closer to the batteries.
(Same reason for electricity to get moved between cities at very high voltage then only get reduced to 220v close to the homes they feed)
However.... I have the ability to move my regulator easily from the panels to the battery side of the cable, and there is no noticeable difference from what i have seen, so my suggestion, put it close to the batteries if you can easily, if not don't stress too much, I really dont think under normal setups the couple of Meters of cable between your panels and batteries are going to make much of a difference.
Russell, you did not state what size cable you are using. The 120 W panel is likely to put out 7 A of current. A common size of cable used is 6 mm auto cable, this only has 4.8 mm2 of copper in it.
The formula for voltage drop is:
V drop = (cable length x current x 0.0i7)/ cable cross section.
In your case this will equal (30 x 7 x 0.017)/4.8 = approx 0.75 V - you have a return cable length of 30 m and I am assuming you have 6 mm auto cable.
You will get the full 7 A of current from your panel into a well discharged battery. If the regulator output is set at 14.3 V you will only get the full potential output of your panel up until your batteries terminal voltage rises to 13.55 V (14.3 - 0.75.) That is not much charge in your battery. From there on the charge current will start to drop. Even though the current drop will reduce the voltage drop along your cable your charge current will reduce considerable. Your battery will take a lot longer to charge. This may not be much of a problem if you are not drawing much from your battery but when you get down south where the solar radiation is lower or you have a few days of cloudy weather then you could be in strife keeping power up to your van.
If you relocate your regulator to the battery you will overcome that vast voltage drop and charge your battery much faster.
__________________
PeterD Nissan Navara D23 diesel auto, Spaceland pop-top Retired radio and electronics technician. NSW Central Coast.
Thanks for the maths there, i only have 5m of cable so that would explain me not seeing the drop, must admit that running the numbers on a few different lengths it does add up fast, if i extend the cable moving the regulator does then make sense
-- Edited by Nomad_Nev on Thursday 31st of December 2015 07:40:58 PM
Depends on the panel, the kickass panels have 4 screws and are then plugged into the panel using an anderson plug, so it takes all of a minute to move em, not sure about your panels though, check the follow the wires on the back of the panel and see how it all connects together (or take a few photo's and put em up here for us to look at
