Smartsolarmppt100/20

[Melissa Agar]

Hi there I'm a new member,
So, I decided to upgrade my old 12 volt ss. I've got a 48 volt panel that creates 450 watts. The mppt 100/20 control box and 4 80 amp gel batteries connected in series. I've taken from one of the batteries 12 volts to my inverter which has a safety mechanism whereby if the voltage goes below 12 volts it turns off. The mppt won't charge unless my battery voltage is 5 volts below the panel which never happens.
I've come up with an idea if I connect my batteries in series to 36 volts and then get the control box to charge at 42 volts will the mppt handle this while still using the 48 volt panel. It has to disapate 6 volts.
Is it gonna show or is it gonna blow ?
Anyone know !?

 

[cdsolar]

Welcome.

I am uncertain what you wish to accomplish, perhaps you can provide a diagram. If you are trying to update your system to a 48V system, some points:

You must have a 48V rated inverter on a 48V system.

It is not recommended to have batteries in series (4x12V is what it appears from your message). This leads to imbalance pretty quickly. Not impossible but not recommended. 48V batteries in parallel is recommended.

The 100/20, mppt, (Victron, I assume), will only start charging when the panel voltage is 5V higher than the battery bank. So for a 48V battery, which is often a bit higher at say 53V, you'll need 58V from the the panel, or similar voltage panels in series to raise the voltage to the the mppt. So your single 48V panel won't do. But if you go above 100V (100 in the 100/20) with multiple similar voltage panels in series, you will fry the controller.
(Is the 48V panel Vmp or VoC). Either way you are very close with 2 of those panels.

Note that a 48V system refers to battery nominal voltage, not the panel voltage. This 48V panel is just a coincidence and has nothing to do with the system voltage, other than not meeting the minimum voltage to charge.

You may be able to use three batteries in series and the mppt with the 48V panel to charge them, yes, but then by definition you are imbalanced with the fourth and themselves. I seem to remember that 36V requires a manual adjustment to the mppt settings (screwdriver) None of this is a good idea.

 

[Q-Dog]

If you have a 12 volt inverter, you must use 12 volt batteries. Just wire your batteries in parallel for 12 volts.

The Victron 100/20 only outputs up to 290 watts at 12 volts.

 

[Brucey]

Hi there I'm a new member,
So, I decided to upgrade my old 12 volt ss. I've got a 48 volt panel that creates 450 watts. The mppt 100/20 control box and 4 80 amp gel batteries connected in series. I've taken from one of the batteries 12 volts to my inverter which has a safety mechanism whereby if the voltage goes below 12 volts it turns off. The mppt won't charge unless my battery voltage is 5 volts below the panel which never happens.
I've come up with an idea if I connect my batteries in series to 36 volts and then get the control box to charge at 42 volts will the mppt handle this while still using the 48 volt panel. It has to disapate 6 volts.
Is it gonna show or is it gonna blow ?
Anyone know !?

That single 49V panel simply won't work with a 48V battery system. Two choices, get different panel with VOC of 37-40V so you can run two panels in series. That will give you the +5V over battery voltage needed to start charging.

Pulling 12V off a series of four in 48V is a bad idea. There will be a very large imbalance assuming any kind of load, even with balancer installed.

 

[seneysolar]

Hi there I'm a new member,
So, I decided to upgrade my old 12 volt ss. I've got a 48 volt panel that creates 450 watts. The mppt 100/20 control box and 4 80 amp gel batteries connected in series. I've taken from one of the batteries 12 volts to my inverter which has a safety mechanism whereby if the voltage goes below 12 volts it turns off. The mppt won't charge unless my battery voltage is 5 volts below the panel which never happens.
I've come up with an idea if I connect my batteries in series to 36 volts and then get the control box to charge at 42 volts will the mppt handle this while still using the 48 volt panel. It has to disapate 6 volts.
Is it gonna show or is it gonna blow ?
Anyone know !?

Stay 12v and get a larger controller if you want to upgrade. A 150/60 leaves you headroom for another panel later.

Switching to 48v wont do anything for you. Its a matter of watts coming in vs watts used. With a 20A controller and a 450w panel, the mppt is your shortcoming.

 

[Melissa Agar]

If you have a 12 volt inverter, you must use 12 volt batteries. Just wire your batteries in parallel for 12 volts.

The Victron 100/20 only outputs up to 290 watts at 12 volts.

Hi, but can I still charge with the 48V panel ?

 

[Melissa Agar]

If you have a 12 volt inverter, you must use 12 volt batteries. Just wire your batteries in parallel for 12 volts.

The Victron 100/20 only outputs up to 290 watts at 12 volts.

Ok,thanks.but I I still use my 48v panel ?

 

[yabert]

Sure MPPT 100/20 can be connect to 48V panel.
His job is to take 40-48V from the panel and transform it to charge the 12V

 

[Melissa Agar]

Hi, yes but that's creating a lot of heat as it has to disperse 36 v

 

[yabert]

No, it simply convert energy.
Let say it charge the 12V at 13V and 20A, so 260W, the panel will give around 48V and 5.5A.

 

[seneysolar]

Hi, yes but that's creating a lot of heat as it has to disperse 36 v

All MPPT's get warm. The harder you run them the warmer they get. I'm guessing yours is maxed out at 20A all the time. A larger controller wont get hot, as it is made to carry much more current and has larger heatsink capability.

Make sure yours gets plenty of airflow for best performance. You can even attach it to a larger aluminum plate or something to help disperse heat. They will de-rate as they get hotter.