45 replies to this topic

[rando]

Do you know if your solar panel has one or two wires from the roof?  If it only has one wire, then the issue is mostly likely that the solar controller isn't working correctly as the ground path between the panel and the battery bypasses the solar controller.   Many solar controllers switch the negative side to PWM and disconnect the battery from the panel when the battery is the full.   If there is another ground path, then the controller cannot disconnect the panel from the battery and it will way over charge, leading to what you are seeing.   

 

The other option is a bad charge controller - which one do you have and was it installed by ATC?

 

Either way, it sounds like ATC either owes you a new battery and rewiring your solar correctly, or a new charge controller and battery. 

[5outta6]

Thanks for your reply.

I believe there are two wires from the panel to the controller. On the roof the solar panel plugs into a two pin connector into the roof. 

I have measured the voltage at this point and it is the same as going into the controller. 

A pair of wires come out of the wall and into the controller which is a  CMTP02 controller:

http://diyprojects.e...user-manual.pdf

 

I have said to ATC, a good panel with a ten dollar controller.....go figure.

 

When I first noticed this problems, ATC sent me another controller.  

I think the controller they sent me was defective so I took the truck down to them and they installed another controller.

It seemed ok at their shop but not under real 'solar conditions',  as the truck was not in the sun.

 

As I mentioned now Im back to the same problem. 

 

At night the voltage drops down to 12.7  (with the frig plugged in and using some lighting).

 

{I should have mentioned the system has a battery isolator between the truck battery and the camper battery .  It seems to get warm so Im wondering if the battery is back feeding into the isolator when parked and no engine on.  }

 

I think it is the controller causing the problem. 

 

so to recap:  voltage in full sun off the battery :   16-17 v

                                               at night                   12.7v

 

This is read with a voltage meter off the battery....

 

When I pulled the fuse on the solar to the battery, I still had battery reading on the controller . when I disconnected the ground from the controller to the battery the controller went blank. 

 

could this be back feeding to the controller through the battery ground?

 

With the solar disconnected from the battery it shows  the same voltage going in and coming out of the controller. about 16+ volts....in low sunlight.

 

No solar battery now reads  12.7 v   

 

 

 

 

 

tnx

Edited by 5outta6, 01 September 2019 - 02:14 PM.

[rando]

I overlooked that you said which charge controller you have.   That is definitely a el cheapo unit,  but if you are seeing the same issue with two different controllers, then it seems unlikely that it is directly the problem.   

 

A quick search shows that this controller does switch the negative wire to disconnect the battery when full:

http://www.cashin.ne...ler_circuit.htm

 

So I would still suspect the issue is the wiring and that there is another path for the negative current to flow besides through the controller.   One way to test this would be to disconnect the negative wire solar panel wire at the controller (leave the positive connected).  If the battery voltage stays high, then the negative has another way to make it to the battery besides through the controller. 

 

From the discussion above, this is at least used to be a known problem with ATC campers, and it seems like they will need to rewire the camper. 

 

The power to run the controller comes from the battery, so if you disconnect the negative on the battery side, I would expect the controller to shutdown.  

[5outta6]

Rando: 

I have disconnected the ground from the panel to the controller and the 'solar indicator light' on the controller has gone off, so I don't think that the ground wire is the problem. (but what do I know).

 

the controller is still hooked up to the battery and the voltage on the controller battery terminals read 12.7, the same as my other volt meter.

 

I am going to leave off the ground wire of the controller until the sun gets higher to see what happens.

 

You mention the controller and trying 2 different ones; could they have produced a bad batch of controller, where all are bad?

 

thanks again.

[rando]

The light won't tell you the whole story, as it is probably just connected between the two solar inputs to the controller, one of which you disconnected.  If there is another path you will see once the sun gets high - if the battery voltage goes up, then there is another path.  

 

Given how crappy this controller appears to be, I guess they could have had a bad batch.   If it were me, I would ditch that thing all together, ask ATC to buy you a new battery and go buy a high quality controller like the Victron MPPT 75/15.

[5outta6]

Waiting for sun to rise.

 

ATC didn't supply my battery.     Do you think it is toast?

 

seems ok w/ solar disconnected. 

 

thanks

[5outta6]

Didn't see any rise in voltage with the ground wire off the controller for most of the morning so I reconnected it

 

meter read 14.20 volts  at solar and  13.94 v  from controller to the battery.   so reconnected the ground wire.

 

voltage read 13.6 v @  10:40am

 

11;15am  still read 13.6

 

at about 12:25pm , outside temp 90 F,    voltage read  16.5 v....................

 

 

I pulled the fuse to save the battery.....

 

I think the controller is bad 

 

?????

[rando]

Didn't see any rise in voltage with the ground wire off the controller for most of the morning so I reconnected it

 

meter read 14.20 volts  at solar and  13.94 v  from controller to the battery.   so reconnected the ground wire.

 

voltage read 13.6 v @  10:40am

 

11;15am  still read 13.6

 

at about 12:25pm , outside temp 90 F,    voltage read  16.5 v....................

 

 

I pulled the fuse to save the battery.....

 

I think the controller is bad 

 

?????

 

 

Was the battery showing 13.94V before you reconnected the negative wire, or after you connected it?  Is is not super clear from the description.  

[5outta6]

battery read 13.6   disconnected from the solar controller.

 

 

(I'm looking at my notes now so I'm pretty sure)  these were the voltage reading with the ground wire disconnected from to the battery from the solar controller.  These readings were taken at 10:40 AM

 

14.20 v       solar  from panel to controller

 

13.94       solar controller  terminals  to battery  with ground  wire disconnected

 

battery read 13.6      with ground wire from solar to battery disconnected.

 

 

At 12:15pm  in 90F  temp, voltage was 16.5 on the battery with the solar connected.   so I pulled the fuse from controller to the battery...

 

Tnx.

 

 

{BTW:    If I change the controller , I'm probably going with the Victron MPPT 75/15}

Edited by 5outta6, 03 September 2019 - 12:00 PM.

[rando]

If the battery is reading 13.6V or 13.94V after is has sat overnight, then it is being charged.   The resting voltage without being charged should be something like 12.6 -12.8V.     Unless you have another charge source connected, it had to have been charged by the solar panel - even with the negative wire disconnected.  

 

Given that, I am still not convinced that you don't have a wiring issue, in which case replacing the charge controller won't help.     Another way to test this would be to disconnect both the positive and negative solar panel wires from the charge controller and measure the resistance between the negative wire and the negative terminal of the battery.  It should be an open circuit.

 

It is also weird that you appear to be getting different measurements at the charge controller (13.94V) and battery (13.6V).  These should be the same - so check your wiring between the charge controller and battery.