MPPT charge controller over-charging 12V battery

Forums › Home Workshop DIY › MPPT charge controller over-charging 12V battery - help

snowkiwi

160 posts

Master Geek

#299506 14-Sep-2022 09:28

Hi guys

I think my “MPPT” controller is mistakenly sensing my full 12V AGM as a discharged 24V battery and over-voltage charging it - has anyone seen this happen and know a solution?

I bought a new Kings 160W folding solar panel which included an MPPT controller (a 12/24V model AKSR-MPPT_20A_01 pic below). The controller has no data connection or setup adjustment I can see

On initial connection and testing with my brand new 105AH AGM battery under no load it seemed to charge OK (14.6V) . Then the controller charge/battery voltage jumped up to about 16 to 17VDC and stay there! Disconnect, retest, same thing.

More detail:
When it’s working correctly

1. Only the “solar” LED is on.

2. I’ll connect the battery,

3. then the MPPT seems to sense the battery voltage, decide it’s a 12av system then indicate 3 green “Battery” LEDs as per the manual.

4. Then the load light comes on and it starts sending current (6A full sunshine).

notes: Panel is putting out about 18V into MPPT. Battery was full before connection (open cct 13.1V) after just coming off a bench charge. No load connected to battery (MPPT “load” terminals never used)

5. Then after a few minutes it starts to ramp up voltage a few points then back down again.

6. Finally the 3 green “Battery” LEDs drop to one flashing (manual states this is low battery voltage)

7. Then voltage ramps up quickly to 16 to 17VDC and stays there

8. Hydrogen smell within a few seconds! - so I quickly disconnect.

9. Battery open cct voltage slowly drops back to 13ish V over next 10 mins or so.

With a load on my battery (my fridge attached via inverter ) it doesn’t over-voltage as quick, maybe taking a few hours in full sunshine or all day overcast

trig42

5604 posts

Uber Geek

ID Verified

#2967977 14-Sep-2022 10:01

Normally you have to let the controllers know what sort of battery they are charging (AGM will require different charging profiles to SLA etc.).

It's weird that its 12/24V and you have no way of telling it (It must work it ourt from the battery voltage).

When the battery is nearly full (and every battery chemistry can have a different 'nearly full' open circuit voltage) the MPPT should just be trickling charge in. It sounds like yours is boosting because maybe it thinks that the 'Full' voltage of a 12V battery is something like 14.4, not your 13.1

According to the specs I've found for your controller, it won't stop charging until the battery is at 14.7V (and it should shut off at 16V).

What model is your battery? Have you checked the charging specs for that? It looks a little like your MPPT is not compatible with your battery (and since you have no way of changing the charging specs of the MPPT, you're stuck and continuing to use it will kill your battery).

Can you go back to the seller and ask them what's going on? Have they got another MPPT they can supply you with and credit the value of this one?

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richms

26384 posts

Uber Geek

Trusted

Subscriber

#2967981 14-Sep-2022 10:27

This happened to me with an aliexpress charge controller that would do both. Seems it was just dumping the panel voltage straight onto the battery without bucking it down as it was failing. Had to remove all power from it to have it recover.

Cooked up a couple of SLA's because of it. Changed to series and 24v system and a newer better controller. So far so good and not had 30ish volts go straight across the battery, but at 24v it should be less disastorous.

Richard rich.ms

snowkiwi

160 posts

Master Geek

#2967997 14-Sep-2022 11:09

Thanks for the replies guys.

i went back and checked my test figures.

when it’s behaving it charges at about 13.4V more or less. - I think this is a standby type charging voltage for my agm deep cycle when it’s full.

the 14 odd volts i mentioned is when it’s hunting up and down and about to fail over-volt to 16 or 17V.

Trig - I’ve been back and forth emailing with supplier (Aussie crowd so I can’t pop in to talk).

it’s reached the “we’ll give you a refund if you smash up the panel and send us the photo” stage or pay more money to drop it at the tip. They don’t want it back and I’m against just throwing stuff away that may still have use - the panels look to be fine, it’s just the controller.

Rich - Man your systems sounds disastrous 30V into 12V, ouch! hope you got some compensation.
But I think mine still may be bucking down the solar voltage fairly OK most of the time anyway.

I maybe wouldn’t mind if the overvoltage protection kicked in correctly at 16V but nothing, no alarm or cutoff after several minutes.

My gut feeling is it suddenly thinks that the voltage is too high for a 12v so it must be a very flat 24v battery and increases voltage.

I need to disable the automatic 24V sensing cct somehow

tripper1000

1539 posts

Uber Geek

#2968087 14-Sep-2022 13:05

Sounds like the controller has gone bad or had a fault from the factory.

With any dual voltage solar controller, it is important to connect the battery first, so that it senses and configures correctly before trying to charge.

BTW that controller doesn't look to be MPPT (only removing to cover will prove it). I have found the manual for that controller and while a few of the sub headings say "MPPT", the title doesn't, and the spec's hint that it is not. One of the critical specs for and MPPT controller is the PV input voltage range, and this is conspicuously absent. (Too low of a voltage from the panels and it doesn't work, too high and the smoke comes out. Better controllers accept higher PV voltages).

It is very common for PWM controllers to be advertised as MPPT on Aliexpress/Wish etc. The external photos look like it isn't MPPT - I could be wrong, but it just doesn't look fat enough for a 20 amp MPPT.

trig42

5604 posts

Uber Geek

ID Verified

#2968088 14-Sep-2022 13:16

^ I agree, the controller looks like a PWM one. However, Dick Smith are selling them as MPPT. The price suggest MPPT (but really cheap MPPT).

https://www.dicksmith.co.nz/dn/buy/sunyee-atem-power-20a-mppt-solar-charge-controller-solar-panel-battery-regulator-12v24v-usb-output-cy1220mt-ap-vor/?utm_source=google&utm_medium=product_listing_ads&gclid=CjwKCAjw1ICZBhAzEiwAFfvFhFMsM1dF67Htj_QY9WY8xs_nuRp-M5o1BpaGNryYefHNLTV0h2TWYhoC8noQAvD_BwE

I reckon you're better off getting another controller.

tripper1000

1539 posts

Uber Geek

#2968090 14-Sep-2022 13:25

Looks like it could actually be MPPT:

https://www.youtube.com/watch?v=53RnB2iZAx4

It is crazy cheap for MPPT if it is.

trig42

5604 posts

Uber Geek

ID Verified

#2968091 14-Sep-2022 13:25

Found a guy that pulled these apart and checked them out, apparently they are MPPT, but not good:

https://bkhome.org/news/201905/mppt-regulator-is-genuine-mppt.html

and his follow up, using it on a camping trip, did the same as the OPs:

https://bkhome.org/news/202002/first-camping-trip-in-2020.html

snowkiwi

160 posts

Master Geek

#2968114 14-Sep-2022 15:35

Thanks for all your comments guys.

MPPT or PWM? - It did seem too cheap for an MPPT. (But too expensive for Chinese PMW)? But it was included with the panels so hey.

Trig - thanks for the link to Barry’s news site - I hadn’t seen that in my own google foo and it is an MPPT albeit a basic one. I’ll look over his site in detail.

Tripper - That was my initial concern to connect battery first to “teach” it 12 or 24V. But the controller is already connected to the panel on the back of the panel. And the LED illumination order ( solar LED first, 3 battery-level next, then load last) seems to indicate it waits a time for a battery voltage before switching 12 or 24V then turning on the “load” LED which may in fact be an “Im now charging “ LED because the load terminals are not connected.

I may try unscrewing the controller panel wires and reconnect after the battery instead. I first need it to fail again - after 3 weeks of testing and it failing every time, today, it’s making me a liar and not failing. It’s stuck at about 13.4V

i really want to test if it’s multi stage charging too. I suspect it’s at least 2 stage (14. 5 ish charge and 13.5ish standby)

trig42

5604 posts

Uber Geek

ID Verified

#2968119 14-Sep-2022 15:40

Oh, definitely remove the PV and then remove the battery then connect it up by connecting battery first, then PV.

I've had a couple of MPPT controllers (EPever ones) and they make it quite clear that the battery must be connected before the panels.

snowkiwi

160 posts

Master Geek

#2968125 14-Sep-2022 16:23

trig42:

Oh, definitely remove the PV and then remove the battery then connect it up by connecting battery first, then PV.

I've had a couple of MPPT controllers (EPever ones) and they make it quite clear that the battery must be connected before the panels.

will do - makes me wonder why on earth kings hard wired it that way. Too expensive to put a switch or connectors in the PV line apparently.

im going to remove it from the panel and reposition it on the battery box with Anderson or XT60 connectors everywhere anyway

tripper1000

1539 posts

Uber Geek

#2968615 15-Sep-2022 13:12

Sorry, some of our "connect panels last" commentary could be ambiguous/subject to caveat in a portable situation.

Just to clarify, the controllers usually need to see voltage from the battery before seeing voltage from the solar panel. In a fixed installation this usually means connecting the battery first and panels last, but if you have portable/folding panels, darkening the panels (by covering them or folding them up) before connecting the battery should be just as good as disconnecting the panels, electrically speaking. If they are in the dark they produce near to 0 volts, which is as good as being disconnected.

I didn't think about that until you asked why they would be supplied without a switch. This procedure for starting up the controller could explain why many people seem to have the same problem or why you can get inconsistent results.

snowkiwi

160 posts

Master Geek

#2969061 16-Sep-2022 11:14

tripper1000:

Sorry, some of our "connect panels last" commentary could be ambiguous/subject to caveat in a portable situation.

Just to clarify, the controllers usually need to see voltage from the battery before seeing voltage from the solar panel. In a fixed installation this usually means connecting the battery first and panels last, but if you have portable/folding panels, darkening the panels (by covering them or folding them up) before connecting the battery should be just as good as disconnecting the panels, electrically speaking. If they are in the dark they produce near to 0 volts, which is as good as being disconnected.

I didn't think about that until you asked why they would be supplied without a switch. This procedure for starting up the controller could explain why many people seem to have the same problem or why you can get inconsistent results.

thanks for the clarification.

snowkiwi

160 posts

Master Geek

#2991694 4-Nov-2022 04:24

Update

After much back and forth with Adventure kings - Me mainly refusing to smash up a whole solar panel and controller for a full refund - they finally agreed on my suggestion of half refund of just the dud controller, so I drill holes through it, photoed it and 3 months later got a partial refund.

I now have a slightly more pricy but hopefully better dick smith (Kogan) dual input, 12V only, mppt.

I will connect to car and solar panels and test at a later date this year.