Instructions for setting up the MPPT-V08A Lithium Solar Charge Controller with CN3722
The information in the listings for these modules is virtually incomprehensible so after a bit of trial and error I’ve worked out how to set the maximum output current for your solar panel and the cut off voltage for your batteries. The instructions below are using the following items.
12 V 10 W Solar Panel from AliExpress
MPPT Solar Charge Controller from eBay or AliExpress
Two 18650 batteries and holder
Step 1
First turn the voltage pot fully anti-clockwise and turn the MPPT pot fully clockwise. You will be able to hear them click when they are fully turned.
Step 2
Connect the solar panel but don’t connect the batteries.
Connect a voltmeter across the battery terminals.
Turn the MPPT pot anticlockwise until a voltage reading appears and the LED flashes blue
Step 3
Connect batteries that aren’t fully charged via an ammeter.
Turn the voltage pot clockwise until a reading appears and the LED turns red.
Step 4
Adjust the MPPT pot to reach the highest value on the ammeter. This is the maximum charging current your solar panel can provide.
Step 5
Charge the batteries in a quality charger until they are full.
Connect the charged batteries.
Slowly turn the voltage pot anti-clockwise until the current shown on the ammeter is 0. This is the cut off for charging when the batteries are full IE the maximum charging voltage.
Advice
Note that the above is just a tutorial for setting up these devices. Your finished system must include battery balancing so your batteries are evenly charged. Without a balancing system your maximum charging voltage could be unevenly distributed. For example if your maximum is set at 16.8 for 4 batteries you might expect them all to be topped up to 4.2v but without the BMS they are could have any value that adds up to 16.8v. Some of them could be overcharging.
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I purchased one of these very small controllers on Ebay, to keep a Sealed Lead Acid battery charged. But no instructions… a Google search lead me to your post on the subject.
Thank you, for what seems to be the ONLY instructions on how to set this MPPT charger up!
Much appreciated.
Cheers!
Thank you VERY much for this good Instruction !!! I found nowhere a instruction for this controller.
Thanks for making sense out of the Chinglish coming with the Banggood product description – very helpful to configure this nice PCB.
Additional info: According to the CN3722 documentation, pin 6 provides the option to connect an NTC for temperature control of the battery for extra safety. Since there is no soldering point prepared connecting it requires good soldering skills.
Will this charge controller work with a renogy 100w solar panel running at 5.72A?
Looks like 5A is the limit so if you have bright sunshine it will probably be too much for the device.
An Youtuber tester it under load, at lower voltage, 3A seems to be the limit, otherwise you’ll need to add a little fan or more heatsinking
My voltage and MPPT pots turn forever with no clicking, I wonder if mine are broken.
it’s a surprising amount of turning before they click. Unlikely they are both broken but possible.
It does take quite a few turns
Thanks for the instructions! I have some maybe dumb questions:
What is the default setup for this charger out of the box? All of these setup directions are great, but it would be nice to know if we need to do all of these steps for every charger.
Is there a way to do a check to see what the max charge voltage and the max charge current is?
For steps 2 and 4, do you need to have the solar panel exposed to maximum sunlight, or does it matter if it is exposed to any sunlight?
It’s been a while since I used it. I think the specs are in the advert but it’s only really designed for smaller panels. Maximum sunlight I think. It’s setting up to maximise for the available current at that point and then it should keep that as the voltage changes.