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Topic: [closed] solar charge controller... (Read 1 time) previous topic - next topic

wothke

Jun 03, 2017, 01:40 pm Last Edit: Jun 09, 2017, 03:52 am by wothke
I am powering my Arduino based device (outdoors) using a 12V lead battery and a small solar panel. One of these serves to control the recharging of the battery: https://www.aliexpress.com/item/10A-Solar-Charge-Controller-10-AMP-Solar-Regulator-Free-shipping-worldwide/516730765.html

I had connected my Arduino to the output of the above "PWM charge controller" (as specified in the manual) and configured the "charge controller" mode for premanent output. This was some month ago and the devices worked nicely since.... until 2 nights ago: then I noticed that the "charge controller" suddenly has some kind of malfunction: while the Arduino is disconnected the controller reports "full battery" & "output turned on".. but as soon as the Arduino is plugged in (*at night*) it oscillates between "output turned off/on" modes. As soon as the sun is up the problem disappears.. (given that the other modes of the "controller" all revolve around some day/night distinction I would guess that something within that "output enabling" logic is just fubar - but since I am not really interested in  that "output" feature I would like to just bypass it completely..)

Question: Would it be safe to connect the Arduino directly to the 12V battery (instead of to the  malfunctioning 12V output of the "charge controller") or would the attached PWM charge controller have any side effects that might be dangerous to the Arduino based device (whatever the "charge controller" feeds to the battery to "recharge it" would obviously also be input into the Arduino..)?



MarkDerbyshire

You can connect it directly but there is the danger of the Arduino draining the battery beyond recovery if the solar cannot keep up which is the problem I had here in the UK over the winter.  I have now upgraded to an MPPT controller and a 40W panel which just about keeps the output on over the winter - driving a Nano and an MKR1000

wothke

#2
Jun 03, 2017, 03:23 pm Last Edit: Jun 03, 2017, 03:55 pm by wothke
PS: I am using a small 20w solar panel but if the reading on the "controller" is any good, my battery is always fully charged, i.e. it seems to provide more power than my Arduino & solenoid valves consume.. and we have about 300 sunny days per year..

I guess I'll give it a try then and just connect my device directly to the battery.. and have a look at the charge level from time to time..

TomGeorge

Hi,
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
Include you power supplies and panels.

A picture is worth a thousand words.

Thankes.. Tom.... :)
Everything runs on smoke, let the smoke out, it stops running....

wothke

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
Include you power supplies and panels.
This here is the exact "charge controller" product that I am using (https://www.aliexpress.com/item-img/Upgrade-version-20A-Solar-Charge-Controller-Regulator-12V-24V-auto-switch-480W-APJ/32692432405.html), here is a link to the solar panel: https://www.aliexpress.com/item/Hot-Sale-20W-18V-Polycrystalline-silicon-Solar-Panel-used-for-12V-photovoltaic-power-home-system-20Watt/32287159443.html and finally this is the battery: http://www.all-batteries.fr/batterie-plomb-agm-s-12v-7ah-fr-12v-7ah-t1-amp9037-35732.html

As can be seen on the photo of the "charge controller" there is not much to be done in terms of wiring: There are 3 +/- terminals to be connected. Left to right: Solar panel, battery and then the consumer (i.e. my device).

I only documented parts of my circuit but frankly I do not see how the design of my circuit might of any relevance here: The "charge controller" would probably malfunction at night whether I connect my device or some simple light bulb.

Still here some background info to give an idea:

1) My device is an "irrigartion controller" that controls 9V/12V DC selenoid valves and collects&reports irrigation  related data to my PC.

2) I am using this prefabricated part (lets call it RelaisPCB) as a building block to switch the power to the valves: https://www.aliexpress.com/item-img/With-optocoupler-4-channel-4-channel-relay-modules-relay-control-panel-PLC-relay-5V-four-way/1723049399.html

3) Based on the 12V power supply (see battery/solarpanel) I am using this type of buck converter to get the additional 3.3V, 5V and 9V that my circuit depends on in various stages: https://www.aliexpress.com/item/5-pcs-Ultra-Small-Size-DC-DC-Step-Down-Power-Supply-Module-3A-Adjustable-Step-Down/32261885063.html

4) I am using an ATmega128 (5V) that I wired up using the minimal setup shown here: https://camo.githubusercontent.com/214abda83d8529c2be1b8483bb424b4bafdbd375/687474703a2f2f692e696d6775722e636f6d2f6c597a64554c692e706e67

5) Here the part where I control the 9V/12V voltage that I use to trigger/sustain the selenoid valves: (you probably need to open the image in a new window in order to read anything..)

6) Here is the part that I add between the above "RelaisPCB" and the microccontroller: it adds 1amp resettable fuses to the 9V/12V selenoid wires and a signal line that allows the uP to sense if the fuse has blown (I am using at most 1 valve at a time):

7) I am using various I2C based add-ons: 2 EEPROMs, 1 RTC, 1 LCD

8) For communication the device uses a Si4432 (3v3) via SPI (see http://www.electrodragon.com/w/Si4432) and a 433 MHz RF receiver module (like this: http://fluuux.de/wp-content/uploads/2013/12/Arduino_433MHzEmpfaengerFritzing.png)

MarkDerbyshire

Hi,
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
Include you power supplies and panels.

A picture is worth a thousand words.

Thankes.. Tom.... :)
No real need in this case is there.  It's a standard solar charge controller with standard connections - Solar, Battery and Load - nothing difficult or special

MarkDerbyshire

This is the live output from my system using an MPPT controller and 40W panel with a 12Ah SLA battery.  I have found that if the solar output goes above 16 volts it reports that the battery is full even though it may not be and is still pushing current into the battery (trickle)

Hive Monitor

This is the controller I have used

EPSolar MPPT Controller

TomGeorge

#7
Jun 04, 2017, 02:16 pm Last Edit: Jun 04, 2017, 02:19 pm by TomGeorge
Hi,
Quote
No real need in this case is there.  It's a standard solar charge controller with standard connections - Solar, Battery and Load - nothing difficult or special
If thats the case then we definitly need to see a circuit diagram of the OPs setup.
Sorry but your circuit is just about unreadable.
Where is the PV, where is the Solar Controller, where is the battery?

Quote
Question: Would it be safe to connect the Arduino directly to the 12V battery (instead of to the  malfunctioning 12V output of the "charge controller") or would the attached PWM charge controller have any side effects that might be dangerous to the Arduino based device (whatever the "charge controller" feeds to the battery to "recharge it" would obviously also be input into the Arduino..)?
Isn't the 12V Output of the charge controller already connected  directly to the 12V battery?

Please hand draw a diagram showing PV, Solar Controller, Batteries and Arduino controller, with pins labeled.
A picture of your project would help.

Do you have fuses on your battery?
It sounds like your battery is not connected to the Solar Controller output.

Do you have a DMM to measure some voltages?

Thanks.. Tom.. :)
Everything runs on smoke, let the smoke out, it stops running....

MarkDerbyshire

Sorry but your circuit is just about unreadable.
Not my drawing :)

wothke

Isn't the 12V Output of the charge controller already connected  directly to the 12V battery?

Please hand draw a diagram showing PV, Solar Controller, Batteries and Arduino controller, with pins labeled.
A picture of your project would help.

Do you have fuses on your battery?
It sounds like your battery is not connected to the Solar Controller output.

Do you have a DMM to measure some voltages?

Thanks.. Tom.. :)
You must be bloody joking.. you need a diagram to understand this? :


Well, obviously the charge controller has 2 different "outputs" one for the battery and a 2nd one where -
according to the manual - the "load" - i.e. my device - is supposed to be connected. As I already said earlier it is this 2nd output for the "load" where the "charge controller" malfunctions. And for anybody that has actually read my initial post it should be clear that this problem was not present initially but it has sprung up recently (after some weeks/months of successful use).

And as I already explained earlier, the setup still works flawlessly at daytime, the battery is fully charged (at least that's what the "charge controller" says - which of course it is connected to the battery!) - and according to my multimeter the battery supplies 12.71V. btw there are no fuses on the battery.

wothke

This is the live output from my system using an MPPT controller and 40W panel with a 12Ah SLA battery.  I have found that if the solar output goes above 16 volts it reports that the battery is full even though it may not be and is still pushing current into the battery (trickle)
I am getting a 12.71V reading on my battery *AT NIGHT* so I guess it is actually full - and not the controller playing tricks on me..

TomGeorge

Hi,
What voltage do you measure on the LOAD terminals.

It sounds like you have lost the load to battery connection inside the charge controller.

That controller has a few timer functions, check that one of them is not involved in disconnecting the load terminals from the battery.

Tom.. :)
Everything runs on smoke, let the smoke out, it stops running....

wothke

Hi,
What voltage do you measure on the LOAD terminals.

It sounds like you have lost the load to battery connection inside the charge controller.

That controller has a few timer functions, check that one of them is not involved in disconnecting the load terminals from the battery.

Tom.. :)
Interestingly I measure the same 12.71V in the LOAD terminals - even at night - as long as my device is plugged out (i.e. as long as no current is actually drawn..). As soon as plug in my device (in this same *nighttime scenario*) the "charge controller" immediately powers down the LOAD terminals - just to turn them back on after a second, to again turn them off, etc

Of the 16 timer functions built into the "charge controller" *ALL* but *ONE" (the one I am using) are supposed to turn on the LOAD termional's power at dawn and then to turn it back off after some time. I am using the one "mode" were - according to the manual - the LOAD terminals should *ALWAYS* be powered.

As I stated before I have no interest at all in that timer shit and I could not care less if it is broken (which it probably is) - that is *IF* I can safely bypass that crap and just connect my device directly to the battery. The question (which I will repeat here for a very last time) is: Might there be any problem with that approach (other than the problem that MarkDerbyshire mentioned above, i.e. that the battery might be drained completely)? I want to know if there is any risk of damaging my device.. which I obviously want to avoid.


MarkDerbyshire

If you haven't already place a regulator before the Arduino - I use a 9V switched from Pololu to power my Arduinos - as the charge voltage to a 12V SLA can reach up to over 15V in good Solar conditions

wothke

connected my device directly to the battery bypassing the defective output of the bloody charge controller.. now it works fine..

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