Charger and Solar controller not meshing well?

[wopachop]

I have a WFCO charger and Go Power charge controller. I can get model numbers later and also check my manual.

This morning with the charger and solar both connected, I had 2 amps of juice running backwards from the batteries to the controller. Using a clamp meter to measure i can tell the direction the power is flowing.

Here is the sequence.
1. Solar connected. Charger disconnect switch is Open. Trailer on shore power.
2. The solar display is showing 14.7v. Power is running from the solar controller to the batteries with enough amps to maintain 14.7v.
3. I close the disconnect which now means the charger and the solar are connected to the batteries.
4. Immediately I notice the solar display voltage drop to 13.5v. The WFCO charge wire is now giving amps to the battery. While the power on the solar charge wire is now going backwards. 2 amps are being pushed back from the battery to the solar controller.
5. I open the disconnect switch on the charger and voltage goes back to 14.7v with power going from solar to batteries.

[wopachop]

ndrorder wrote:
Since the GP stepped back, the WFCO provided the higher voltage to the circuit (14.4 for a standard WFCO) and dominated the charge. The GP saw this reduction in electron flow and switched down to float mode (13.5 V).

I learned yesterday my WFCO and many others do not go into 14.4v mode at say 75% discharge. (I realize my batts were fully charged)

I have a separate voltage display coming off the converter, and I'm positive the WFCO was at 13.5v and stayed at 13.5v the entire time I was messing around. I was comparing both the solar and converter voltage displays and then going outside and using the clamp meter to view amps.

I was curious how the wfco would act. I'm trying to learn that stupid thing. I didn't expect to see the flow of power go backwards on the solar. From the replies it seems this is not a melting danger. Would hate to damage anything.

[pianotuna]

I find my solar sends power to the chassis. Fortunately I don't mind. I can, if I so desire turn off the isolation solenoids.

[ndrorder]

The batteries will be charged by the charger with the higher voltage potential at the connection to the circuit, respectively. Even though the GP was showing 14.7V, that isn't necessarily the voltage at the connection to the circuit. Since the GP stepped back, the WFCO provided the higher voltage to the circuit (14.4 for a standard WFCO) and dominated the charge. The GP saw this reduction in electron flow and switched down to float mode (13.5 V).

Now that the WFCO has an even higher differential to the GP and if a circuit is complete, electrons will flow backwards to the GP. It seems that GP has expected this reverse polarity situation and rather than providing just a diode which can burn out if the back flow is too great, they have also provided a resistive circuit to convert those 2 amps of electrons to heat thus providing reverse polarity protection.

The random GP manual I looked at state the maximum wire size is 14 AWG. Depending on the amperage the panels were charging at, it wouldn't take very many feet of wire between the controller and the charging circuit to loose 0.4VDC and assuming no losses in the connection itself.

5A - 0.4V lost in 16 feet of wire
10A - 0.4V lost in 8 feet of wire
20A - 0.4V lost in 4 feet of wire
etc.

[Boon_Docker]

BFL13 wrote:

Boon Docker wrote:

BFL13 wrote:
You should have the controller's pos and neg to the battery independent of the WFCO charger's pos and neg to the battery. (WFCO neg might include some frame which is ok)

I'm curious, why would that make a difference?
Is it because of voltage loss between WFCO and battery?

I was not very clear. The two need to be in parallel to the battery, which could allow them to share their output wires. what is not allowed is for one's output wires or even one wire to go to the input of the other.

Thanks for the clarification.

[BFL13]

Boon Docker wrote:

BFL13 wrote:
You should have the controller's pos and neg to the battery independent of the WFCO charger's pos and neg to the battery. (WFCO neg might include some frame which is ok)

I'm curious, why would that make a difference?
Is it because of voltage loss between WFCO and battery?

I was not very clear. The two need to be in parallel to the battery, which could allow them to share their output wires. what is not allowed is for one's output wires or even one wire to go to the input of the other.

[Boon_Docker]

Double post deleted

[BFL13]

The battery accepts most of the amps from the higher voltage charger.

EDIT--as mentioned by Boon Docker--the voltages as seen by the battery at its end of the wires

The solar at 14.7 will supply all the amps once the battery's voltage is higher than the WFCO's output voltage.

If the batteries are near full, then their voltage will be above WFCO's 14.4 (if it does 14.4) because of the solar's voltage, so turning on the WFCO will not show anywhere for amps or battery voltage.

When the controller gets the batts to 14.7, it will do whatever its profile says to do, such as hold it there for two hours and drop to 13.6.

I have seen on my Trimetric monitor that it can show neg amps flow when you turn off a charger keeping the batts at 14.8 and now they will go to 13.6. for the brief time it takes the voltage to fall, it shows as neg amps. Not real, perhaps a monitor thing?

so if your case is like that, if the batts are full and the solar was on the point of dropping to float and then the WFCO coming on triggered that somehow? Really stretching here!

You need to run the batts down a ways and then use both WFCO and solar to observe what happens for real. Not when the batts are full.

[Boon_Docker]

BFL13 wrote:
You should have the controller's pos and neg to the battery independent of the WFCO charger's pos and neg to the battery. (WFCO neg might include some frame which is ok)

I'm curious, why would that make a difference?
Is it because of voltage loss between WFCO and battery?

[wopachop]

I'm wondering if the WFCO sends out a high amp charge when I first flip the switch. I should place the meter on the wire before flipping the switch. Then check max amps. Pretty sure my meter will display max.

[wopachop]

The solar was performing a 14.7v charge. The WFCO was in 13.5v mode. When I closed the disconnect switch, shouldnt the charger supply a very small float charge, as the solar continues its 14.7v charge?

Would expect the solar charge amps to reduce some. Didnt expect the solar to run backwards.

My controller is small and cheap. It only has 4 terminals. 2 for the panel and 2 for the battery.

[jdc1]

BFL13 wrote:
You should have the controller's pos and neg to the battery independent of the WFCO charger's pos and neg to the battery. (WFCO neg might include some frame which is ok)

You have a wiring issue.

Correct. The solar thinks the battery is charged.
BFL13 is also correct with his second answer.

[BFL13]

Do not use the controller's load terminals. Use the Batt terminals only for output.

[time2roll]

Seems like GP is going to float. Very odd for a solar controller to absorb 2 amps unless it has a secondary charge circuit that is connected.

Or just leave the WFCO off.

[BFL13]

You should have the controller's pos and neg to the battery independent of the WFCO charger's pos and neg to the battery. (WFCO neg might include some frame which is ok)

You have a wiring issue.