Victron Energy MPPT 75/15 Auto on/off.

[DMH]

Sorry for the long post but all the following information is pertinent.

Having taken advice from forum members I am now in possesion of the above controller but have a question with regards to installation.

I planned to continue using my existing wiring and switching ect. My present install disconnects the controller via a relay when the ignition is switched on and the engine running, and of course reconnects the controller when switched off, this system has worked fine with the PWM for a number of years. I switch off, slide the solar panel out from under the roof rack, plug it into the roof socket job done, now it seems this system may not work with the MPPT controller?

I have read having the MPPT solar supply AND the alternator running at the same time is not an issue, apparently one or the other will just back off the charge rate? Seems logical enough although I have never tried it however, somebody with a MPPT controller has problems.

If I understand the issue correctly it is as follows:

The battery/s had been receiving a lengthy charge from the MPPT which had reduced charge voltage to 'float', then the engine was started and the alternator raised the voltage over and above the float charge. It then seems that later after some period of 'alternator time' the engine was switched off, from then onwards the controller would not return to bulk charge regardless of how low the batteries were, the owner found by disconnecting the controller from the batteries and then reconnecting the controller returned to normal operation, start the engine at a later date when the controller is in float mode and the problem repeats itself.

So, will it do any harm switching the Victron 75/15 MPPT type of controller as per my old install? Assume diode protected relays throughout this install and any other accessory I have installed.

Many thanks.

[Mike90250]

I have 2 MPPT controllers of different brands, and my AC charger is a third brand. Never had any issues with one affecting the others, and I'm not sure what's happening, except maybe the vehicle alternator is exceeding the safety disconnect voltage of the MPPT controller and it shuts off. Perhaps the fella who suggested the model can assist you in assessing the settings

[DMH]

In the absence of any answers I have simply fitted to existing wiring however I used a manual switch instead of a relay for initial testing.

The directions say wire to battery power before connecting the panel input, that makes sense. I tried leaving the controller on and running the engine, when switching off I found the controller appeared to be confused? It would show a steady yellow (float), and nothing changed even if disconnecting power from battery, to get the controller to behave normally I had to disconnect the panel and reconnect power first and panel second.

I also note the manual states that the controller resets each day, this may clear the problem, who knows?

Fortunately my normal mode is switch off on site, this would then power up the controller, I then connect the panels. If there is to be a problem, then it may show up if I restart the engine for example to reposition the car, this would mean the controller would lose power but would still be getting supply from the panels, when I switch off the engine the controller would have now been connected in the wrong order, I am guessing this is what causes the confusion?

Many thanks.

[DMH]

Hi Mike and thanks for the reply.

Unsure how your message dropped inbetween my two anyway, if you have three different systems supplying to the same battery, can I assume you have had to alter the various voltages for exampIe, to prevent one controller going into float mode too early? I have been out with the car 'fiddling', a couple of things of note, the green LED is sometimes on steady, and sometimes flashes fast. This would indicate the 'batterylife' setting is in action one moment and not the next, regardless where the jumper is put on the pins?

The sun has gone down now so testing is on hold, I did note after around 45 minutes bulk charge mode was changed to absorption and my on board battery monitors reflected this. So all in all the controller appears to be working ok, I have some stop/start useage tomorrow, so will see what happens.

Many thanks.

[Mike90250]

nearly all controllers work by voltage sensing. BULK till one voltage (say for example 14.4v), ABSORB holds that voltage (14.4v) for xx minutes, float drops back to a lower voltage ( 13.3v)

Better controllers have adjustable voltages. They can be harmonized to be close to each other. One of mine exits Absorb about 30 minutes before the other, because it's timer started first.

Just like Confucius Say: Man with one watch, knows time. Man with 2 watches, never sure.

[DMH]

Just checked the controller, the yellow light is off (night time), the green light is flashing fast, unsure whether that's right or not?

Manual states controller is in 'batterylife' mode, I cannot seem to stop this regardless of jumper position?

I have zero connections on the output terminals and probably never will.

Many thanks.

[DMH]

Today I recreated the starting engine, run a few minutes and shut down. Controller went to float? I know that it is possible that both batteries are full, and the Victron unit registers this.

Will check again tomorrow as car has not been started all day, and panel has at least 8 solid hours of sun.

Many thanks