or use a DROK voltage buck booster as an intermediate stepwhat i need is a charge controller that controls the V+ outputthe majority of controllers use common connection for all the Plus connections and control the output via the negative sidethis works as long as you can isolate panel negative and battery negativewhich is Easy to do on a new installbut i have situation where i can't find and separate the negative line from an OEM solar panel wiring, old panel has been replacedthe original was 5w~10w trickle maintenance for the chassis battery, using only a blocking diode in the positive feed and the panel negative wire is tied into chassis wiring someplace, and only the positive wire was run up front to the fuse panels for connectionusing a normal controller ties all the positives together, i have to use jumper wires to the negative BUS for both sides in and out and they are common, batteries in back panel hot wire up front, negative unknownsince using an isolated negative is not possible need a controller with control in the positive side of the circuitor maybe a voltage buck booster between the panel positive and the power connections terminal block a DROK between the solar controller and the panel might provide isolation and voltage boostpanel into DROK (which would only function when the panel was producing power ) booster output connected to input of solar controllerwe are talking a max of 90w power, my memory from our previous discussions , says these are common neg, with the positive out put floating and controlledwhich should work for this projectcomments please

I don't understand the OP situation at all, but if it is any help (not a clue) I do know there are some solar controllers that are "positive ground" which may or may not also mean they control from the other side like Mr Wiz wants. Eg the EP Solar, "Landstar" I had was positive ground.In the RV no grounds are used for the solar, so it made no difference, but even with no actual grounds in effect, maybe it controls from the other side? Not a clue, sorry.

In the Outback FM60 and FM80 the controlling is done in the positive lead. The PV- and battery - are tied together in the controller. It only needs a negative connection to the battery -. You can just connect PV+, Batt +, and negative.

Positive Ground means positive commonCheck it out with the wiring disconnectedAll the positive terminals are connected to together panel battery and loadThe negative side is controlledOn this instance I need to control the positive side, or rewire the whole "fan dango" ..

The obvious solution is to run a new pair of wires so that you know exactly what you have. As I recall you've run wires before so...Have you checked the Sunsaver controllers? Not sure what it controls and the manual does show isolated array input. My MPPT 60 has common negative and hence grounded connections if that is a option for you. Maybe check the higher powered MS PMW controllers.Let us know if the DC-DC converter works OK.

I went with a Phocos controller and remote status panel, they can be positive or negative ground.http://www.phocos.com/product_charge_controller.html

need a positive circuit solar controller | Good Sam Community

36 Replies

MrWizard
Moderator
Jul 20, 2015
At 7:15 am... chassis/starting batteries resting voltage 12.84v

at 9:30 am cloudy skies..9.04v 1 amp input
output battery side reads 13.04v
MrWizard
Moderator
Jul 20, 2015
the last measurement i made at 6pm

output battery side 13.06v
input solar side 6.60v
i did not check for an amps charge, i don't believe i would have found any
i think charging for today was over
but i know there is no back feed drain, because the solar powered fan behind the fridge vent is not running, i have input/output positive circuit isolation and NO excess drain on chassis batteries beyond the normal parasitic stuff , which the daily solar should be able to handle, even this meager charge rate

i think the booster is a success

there was no back feed night time drain with the diode, but there was voltage drop across the diode, hence the reason to use a controller or boost circuit to increase the applied voltage
MrWizard
Moderator
Jul 19, 2015
Xantrex PWM test video thread http://forums.woodalls.com/index.cfm/fuseaction/thread/tid/28474183/gotomsg/28474183/p/1.cfm#28474183
MrWizard
Moderator
Jul 19, 2015
here is the voltage booster

here is the booster and the cheap 10amp $12 controller next to a ruler
MrWizard
Moderator
Jul 19, 2015
There is no mystery about the panel voltage on the xantrex
That circuit is totally isolated, except for the house batteries being grounded to the chassis
That was all new wire from the panels to the controller to the house batteries

As for the chassis side, if the diode inline with the positive from those panels had not burned out, I never would have bought the new cheap controller or the voltage booster
What started this thread was the fact that the cheap controller was electrically different in connections and operation from the Xantrex controller
I can disconnect the chassis panels, but it won't change what is going on at the Xantrex, I could wire them to house circuit, but it would reduce voltage going to the controller, they are 15v Siemens panels that are about 18 yrs old
BFL13
Explorer II
Jul 19, 2015
With the amps not as expected with the new set of panels in that old location where the neg panel wires go to a mystery place on the Rv frame or wherever, and since with that you also get the mystery 17v at the array terminals,

-- it would be interesting (if possible) to disconnect the positive to the controller just from that set, and have just the rest of the panel positives to the controller from the other locations, and then see what the input voltage is.

If it is close to battery voltage as with other PWM controllers, then that mystery goes away and all that is left is sorting out what is going on with that one location's voltage, which might help solve the OP issue in this thread too.
MrWizard
Moderator
Jul 19, 2015
The positive common of the cheap 10 amp controller, would have been fine as it is in most RV solar installs, but the fact the negative wire for these two panels (using original OEM wire) has the negative grounded aka tied to the chassis negative not isolated..It's why I bought the voltage booster
Which is now installed and working, charge current is less than expected less than two amps, the input voltage is registering 9.16v @ 1.7 amps
Battery side output is reading 12.72...at 1.1 amps charge
It was at 12.41 before connecting and charging

We have intermittent clouds, I'm going to get on the roof and clean the panels, we had thunderstorms yesterday, nothing to match other parts of the country but a big deal around here, July is our dry month and we are in a record drought, so a half inch of rain is a big deal and possibly a record

Panels were fairly clean, I didn't need to climb up there
BFL13
Explorer II
Jul 19, 2015
The C40 manual explains some of what the OP is about.

http://www.wsetech.com/pdfs/C_series_manual.pdf

I can't follow what Mr Wiz's installation is, but night time feed back was mentioned. The manual says the controller has an automatic night time switch instead of a diode for that. It says if there are dump loads attached you do need diodes for night time. No idea if that is what Mr Wiz is getting into here.

It says the shunt for the display panel is in the positive side because the negative side is common to panel and battery in this controller. No idea, but would the Mex Gizmo proposed to go on the positive side screw up the display because of that shunt?

--------------

As an aside, note that the controller rating of 40 amps includes the "derating" required by the NEC, which was a topic in another thread recently. It also says if the amps exceed that rating, the controller will not clip the amps.

Instead, it allows the higher amps through until the heat sink limit is reached, and then it will reduce the amps. So it will not fry, which is good!
BFL13
Explorer II
Jul 19, 2015
Mr Wiz, I certainly do believe you. I did say I have more to learn about this, and will use a different thread when I do.

"BTW if PWM doesn't control voltage how is it the batteries never seen full panel voltage ?"

On that (to be continued in another thread eventually), my puzzle is that I thought it was the other way around, that the panel would be at battery voltage plus line loss, at least until the battery reaches the controller's high set point, and I thought after that too.

Anyway, more later and in a different thread.
MrWizard
Moderator
Jul 19, 2015
the xantrex does NOT have auto system sense ,
you set the voltage system 12, 24, 48 with jumpers
as long as you do not exceed the input voltage limit, it will output the charge and float you you set from the internal dial switches
i'm telling you how it works and you refuse to believe me
when i find time, i guess i will just have to make a little video, showing the Fluke plugged directly into the panel drop wires and the read outs on the Turngy meter and the face of the xantrex
a device doesn't have to have an inductor coil to reduce DC voltage
it can be done that way, but it doesn't have to have one
you only MUST have an inductor/transformer to increase/boost voltage

this is ALL Off Topic to this thread, which is about isolating and boosting the panel voltage for the chassis battery
and the voltage Booster i will be installing

BTW if PWM doesn't control voltage how is it the batteries never seen full panel voltage ?