Voltage drop from solar controller

[Canadian_Rainbi]

or: Here we Go Again.

Still trying to get my 420 Watts of solar to fully charge my 484 AH of battery. (Currently in southern Mexico.)

Layout:

2 80 Watt panels and 2 130 Watt panels in parallel, 420 Watts (Went parallel rather than series because where I park one or more panels are soon shaded.)


4 6 volt GCs rated at 242 AH each, total 484AH

Controller: Bluesky Solar Boost 2000E MPPT Controller. Bluesky is a two stage charger. Bulk charge voltage was set at 14.4 volts, op from default of 14.0 RECENTLY increased to 14.67V

Also charge via Xantrex Prosine 2.0 PSW inverter charger. Bulk Charge set to max at 14.4 volts.

The output voltage from the controller would always read higher than the battery voltage as reported on the Xantrex remote. (Accurate)

From Controller output about 8 feet of #10 fused with 30A fuse
THEN approximately 20 feet of I think #6 to batteries.

At the junction of the fuse the wire connects to what was originally the connection point for the converter DC Output and also feeds the 12V breakers for the 12V systems. This connection point is 20 feet or more from the batteries. It is impossible for me (physically) to follow this cable end to end. (The converter is no longer there.)

Before I increased the controller output voltage from 14.4, when the controller read 14.4 as the battery voltage then begin reducing current. The battery voltage as displayed by the Xantrex remote would only be 13.7, the same as measured by DVM at the batteries. 0.7 volts drop.

Of course the batteries never reached 14.4V. As the day progressed and the panels became shaded the charge current eventually dropped enough that the controller would pass all available current to the batteries, whose voltage might reach 13.8V.

A couple of days ago I increased the Controller output voltage to 14.67 (the control is touchy). Batteries still have not reached more than 13.7 Volts when the controller was passing maximum current (19.0 Amps) before noon. Controller at 14.67, batteries at 13.7! a full volt drop! Increasing the Controller voltage gained nothing apparently.

NOW: 6:20PM Sun gone, no solar input, minimal 12V draw, Controller reading batteries as 12.76V, the Xantrex says 12.8

Enabled Xantrex charger (max charge set at 96Amps) Starts charging at 62 A, 14.2 Volts, charge rate decreasing as I watch, within a minute or so it settles down at 28 Amps, batts still at 14.2V. I expect both will slowly decrease.

CONCERN: I checked the fuse holder temperature with my ir gun: 108F. Quite warm to the touch. The plastic body of the fuse itself and wires registered 83F, ambient on the floor was 81 or 82. This is the same (rather replacement) fuse holder that melted last year.

QUESTION: I have a spare fuse holder, what appears to be a higher quality one, from AutoZone. Should I replace it?

Question: How fully are my batteries getting charged from the solar? I have been in the habit of enabling the charger on cloudy days or at least once a week.

MY CONCLUSION

I really need to beef up the cables from the output of the controller to the batteries. Will I be wasting my time going up one size to #4 or should I bite the bullet and see if #2 or even 1/0 will fit?

OR third QUESTION: Do I need to replace the controller with one that I can put in the elec. compartment near the inverter, about three or 4 feet from the batteries?

NOTE to the curious: Yes I could run the charger 24/7 but here in Mexico electric power is VERY expensive. I have the panels, so why not try to save the CG owner, a friend, a few pesos here and there.

[pianotuna]

Hi,

Thanks for sharing the results with us!

[Canadian_Rainbi]

So the controller output voltage has been set at 14.9V for 5 days now. The battery voltage as measured by the Xantrex remote now reaches 14.5 in the early afternoon and even now, at 4:00 PM it is reading 14.2, the charge current is down to 6A because of shading.

I'm going to call this close enough and put the mounting screws back into the panel before I drop them down the sink. :E

Muchisimas Gracias to all for their valued input.

[Canadian_Rainbi]

I just added a couple more photos. (connection point for controller output/battery/breakers.) I think you have missed the fact that the #6 wires from the battery to the terminals under the fridge feed the 12V breakers for all the coach 12V systems. A connection here to uncontrolled solar voltage would be risky at best.

To leave the controller where it is? I would hazard a guess that I would need at least 2/0 if not 3/0 to keep the voltage drop reasonable.

I think that for best results I need to run new input wires, maybe #6? (open to suggestions) from the roof to the electric compartment, and install there a new controller that has remote panel for battery voltage, charge current, etc and temp compensation. Then I could cover the hole with the remote panel.

Then, just because I could, I'd add a panel mount dvm to read the voltage across the 12V breakers! It's only money!

Then I could add more panels!

[BFL13]

Looks like you can go from a junction box on the edge of the roof with a wire pair down the front of the rear slide opening, tucking the wire pair behind the wiper, then over under the slide to go in the top of the compartment door you can slam the wire pair on, or else put a "cable hatch" in the door.

When the slide is closed it will hold the wire pair in place so you don't even need the white plastic water pipe I mentioned before!

Meanwhile, you could move the controller to the compartment- not nailed down yet- and use jumper cables end to end down from the roof to the array side of the controller and another set of jumpers controller to battery.

[time2roll]

The hardest part is covering the hole it will leave in the kitchen.
Leaves 3 options IMO.


#1 move controller: If there is any slack in the wire you just remove controller and wire nut ++ & -- at the controller location.
Then cut the wire in the battery compartment and insert controller. Just toss it in somewhere.

Make it nice when you get home. Still optional the pull big wire and re-install into the kitchen or remount properly in the electric compartment.

#2 Ground the negative output from the controller and repurpose the negative connection as positive. This assumes you have two wires from controller all the way to the battery.

Pull a proper single wire upon return.

#3 Live with it.

[Canadian_Rainbi]

Here are some photos that will give you some idea of the work involved in "move the controller closer to the batteries".

http://1.bp.blogspot.com/-TwSnFaR4nuY/UtxLVnAlf6I/AAAAAAAAHZE/_7p1M72BPQ8/s1600/DSCN4107.JPG

There is one more 130W panel (identical to the one to the right) that is lying flat just to the left of the 2 80 watt panels. The wires join near the holding tank vent (edge of roof near centre) and go down alongside the vent.



The BlueSky Solar Controller is the black panel with the red light on, to the left. The Xantrex remote is next to it.

The vent stack is in the wall behind the controller. The battery and electric compartments are located roughly below the white plastic box on the floor in the bedroom (right).



The output from the controller continues down the wall then forward a few feet to under the drawer below the fridge.



12V breakers above microwave/convection oven



Under the drawer below the stove.
Connection to bolt terminals from battery, location of original converter. Cables also go up to 12V breakers from this point. Not to point out the obvious, but the white and red wires and 30A fuse are from the controller output.




These are the battery and electrical compartments. The stuff on the ground belongs in there too, except for the large white bottle of distilled water. I'm not sure where we can mount the controller.



This photo shows where the front solar panels are (top left) and where the battery and electrical compartments are. By rights the controller should be in there. Somewhere.

[Canadian_Rainbi]

Yes, it seems that the good deals at Rallies aren't always! Of course it seemed like a good idea at the time, experience has proved otherwise--always learning.

Almot: I certainly agree that the remote voltage and temp sensing is critical down here. Running a parallel wire is good in theory but it isn't going to happen here. I'll come back and post a picture here to show why.

Pianotuna: Don, input voltage measured at the controller was 15.3 It would seem that there is more voltage drop on the input side than there should be. All 4 panels are wired in parallel with lengths of #10 wire maximum length about 8 feet at a guess, from the most distant panel to the junction point on the roof. From the junction point to the controller is another 8 feet max of #10.

The sky is quite clear today but there is a lot of varying high thin cloud. Most I have been getting out is 18Amps. I went up on the roof and checked current out of the 130 Watt panels: measured 8A once from one, measurements a few minutes apart ranged from a low of 4.8, most common was about 6.5A. The 80 Watt panels have parallel conductors right into the junction box so I wasn't able to use the clamp-on ammeter.

I had increased the output voltage limit a bit, when it got up to 15.45 I turned it down a little, now reading 14.90V. Good news, the Xantrex remote battery voltage continued rise, finally went up to 14.5V. That was when then BlueSky was showing 15.45V. That was pretty close to the best sun angle on the panels and a bit past solar noon.

Now, 14:20 local time, about an hour later, the Xantex is reporting 14.3V at the batteries, the BlueSky reading 14.9V, 11.5A, the light flashing "Charged", or according to the manual, battery is 90% charged or better and is now at a Constant Voltage Rate.

More good news, I have not had any Hi Bat or Hi Bat Temp warnings from the Xantrex. But I'll check electrolyte levels later. That's just a matter of sticking the tube in a bottle of distilled water and giving the bulb a squeeze or two. I used to have to retract the slide and disconnect and remove two of the batteries to do that!

Over the next few days I'll watch the BlueSky output voltage.

[Almot]

The importance of having the right setup.
Remote voltage sense and remote temp sensor is a must. It might sound that your current problem is the voltage drop, but in Mexico in winter the temp sensor is at least same important. When there is 70F in shade in daytime and 35F at dawn - what else can I say...

Don't rip anything out yet. Just run a length of #8 TNN wire from local Ferreteria, in parallel to existing wiring and see if it helps. Decent electrical supplies are a problem there, but when you are not moving anywhere you can use whatever you have.

[BFL13]

Use white plastic water pipe as a conduit down the outside of the rig. Maybe strapped to the ladder at the back or to whatever works clear of awnings and slides.

[Canadian_Rainbi]

One of the routing problems that I didn't mention is that the battery and electric compartments are under the bedroom slide, on the left side of the rig, behind the rear axle. The the best (only feasible I think) route down from the roof is almost midway lengthwise via the sewer vent, on the right side of the rig where it enters now. It comes down behind the galley cabinets. The fridge is also in a slide and doesn't have a roof vent.

It may be possible via the rear cap but that would mean a much longer run for the input cables as the panels are roughly mid way along the roof and would then have to run back, down and forward to the batts.

Keepin' thinkin'! :h

[CA_Traveler]

Your Vmp is close enough on the panels. You will lose a few watts, perhaps less than 5.

The fuse might be a fire hazard and I would solve that problem in Mexico. And if not I would disconnect the solar and burn the CG power.

Think about better placement of the panel wiring and controller to minimize wire loss. Consider along the roof for the panels. There are usually multiple locations like cabinets, etc where wires can drop from the roof. Wires under the rig might be a option.

Example: I have a rear closet, good for wiring and controller and close to the batteries. Midships I could drop the wiring into a storage area where the controller could connect to existing wiring on the inverter. It's a long run back to the batteries but the cables are 4/0. Remote voltage sense would compensate for the wiring loss including when the inverter is on in which case all solar amps would be used by the inverter.

Just suggesting you think outside the box and consider other options when you return home.

[westend]

Canadian Rainbird wrote:
You must have missed me saying in earlier posts, that that is what I will do, when we get home. Meanwhile, down here in Mexico, I am trying to see how I can improve things without tearing everything out. This will NOT be an easy job:

I will have to remove the 4 GC batteries and their cables, remove the inverter (a MAJOR chore) then run new cable down alongside the sewer vent pipe, somehow through the floor, across to the other side of the rig, through and around the frame with attendant chafe resistant covers etc. I think. I may be able to go through the floor in the galley. I'll have to pull a cabinet or two to see just where I can go with what. There may be room for a controller in the same compartment as the Xantrex.

And being less than fit, I'll have to pay someone to do 90% or more of the work. (Unless I can con one or another of my nephews to help!)


You must have a much larger rig than we do, or carry a lot less stuff! Or both! You have more vacant space in that compartment than mine does when empty, and it contains the 50A cable, the Xantrex Inverter and the transfer switch. Oh, and the 30A extension cord and TV coax!

Yup, missed the wire upgrade at home, my bad.

I would think about the situation a bit. It may be easier to run wire on the roof from your modules and make a straighter drop to the new controller location. If you use a roof-top junction box, you can position the through-roof entry point anywhere.

My rig is on the small side, 22'. The compartment that is pictured is in the inside of the trailer under the kitchen counter. I use the compartment like a standard kitchen cupboard while under way. The wiring from the switches/controller/inverter are all behind the panel and lead down to bus boxes and then a few inches to a bank of AGM batteries. My second bank of batteries is directly across the floor from the AGM's, two GC2 6V in their own vented box. The 6V bank is wired through an ABS pipe below the floor and connects to the bus boxes underneath the mounting panel, about 6'--two runs of 1/0 welding cable. Engineering and installing all of this is rather complicated but I had weight distribution considerations in mind, the 250lbs. of batteries are right in front of the wheel wells. I didn't want to add that much weight directly on the tongue.

[Canadian_Rainbi]

smkettner wrote:
I would go 15.0 max and just get what you can.

I'll drink to that. Hmm I have a nice single malt somewhere.

Do you have two wires to the battery?
Could use the frame for negative and double up on the positive.

A possibility, but that will have to wait for spring. Now, where is that bottle of Jura Superstition? :h

[Canadian_Rainbi]

I'll try to post some photos tomorrow.