Best panel setup to charge 48v batteries?

[freemanson]

Greetings to all,
I am on the planning stage for a setup on a boat. Now I am planning to use 48V batteries and 4-5 solar panels. But from what I have read the voltage from panels needs to be higher than 48v to be able to charge? Is this correct statement or not?

If the panel is 24v, do I need to connect them in series to double the voltage?

 

[Solarcabin Channel]

Your controller takes what ever voltage the panels produce and converts it to the correct voltage for the battery.

 

[MichaelK]

Your controller takes what ever voltage the panels produce and converts it to the correct voltage for the battery.

Umm, well no, that is not correct. What a MPPT controller can do is transform the incoming voltage DOWN to what the battery wants to charge at. A controller can NOT increase voltage. So, a single 12V panel can never charge a 24V battery. But, two solar panels wired in series could, with an MPPT controller.

But, to answer FM's question, MPPT controllers (not PWM controllers) will take the incoming voltage and transform it down to make the voltage the battery wants. Keep in mind though that 12V solar panels do NOT put out 12V, and 24V panels do NOT put out 24V.

A standard 36-cell 12V solar panel has a Vmp of ~18V. A standard 60-cell panel puts out ~30V, and 72-cell 37.5V. A MPPT controller needs some overhead voltage above what the battery needs. Midnight Solar says +30%. A 48V battery bank will want to charge at anywhere between 50-59 volts, and for lead-acid that needs equalization, up to 64V. So, you need a panel string that is ~ 58V X 1.3X = 75.5V.

So, wire your panels to put out at least 75-78V, and you should be fine. That means five 36-cell panels in series, or three 60-cell panels, or maybe just two 72-cell panels.

 

[Solarcabin Channel]

Umm, well no, that is not correct.

What I said is correct in response to the OP's question.

OP "If the panel is 24v, do I need to connect them in series to double the voltage?"

 

[Crowz]

What I said is correct in response to the OP's question.

OP "If the panel is 24v, do I need to connect them in series to double the voltage?"

You said :

Your controller takes what ever voltage the panels produce and converts it to the correct voltage for the battery.

This would imply that the controller will magically upconvert his 24v panels to 48 volts which it will not do.

The op asked :

But from what I have read the voltage from panels needs to be higher than 48v to be able to charge? Is this correct statement or not?

The correct answer is yes to his question with the detailed part being 48v and higher. So in series is the way to go like MichaelK said.

Linking a video is not answering the persons questions.

 

[Solarcabin Channel]

Linking a video is not answering the persons questions.

The video is a good explanation.

 

[Crowz]

You argued with me and Supervstech and a few other members about diesel even after you were corrected and seem to be following my posts trying to start a fight.

I am not going to engage and will let the mods deal with it if it continues.

Vern I wasn't corrected and I'm not dragging that thread in here by pointing out what I mean by that.

I'm not following your post what so ever either.

What I pointed out was it would be nice to answer the op's question and if needed add a video. Just linking videos is not answering a person question. They might as well surf youtube if that is what they wanted.

 

[SamDeleted]

Not to take sides, but I thought the video answered the question well

 

[Crowz]

Not to take sides, but I thought the video answered the question well

No doubt it did. But so would a simple text response too and even having the video after it would rock in my opinion.

 

[SamDeleted]

No doubt it did. But so would a simple text response too and even having the video after it would rock in my opinion.

Yea I think you're right but @MichaelK got there with a good explanation anyways

 

[Supervstech]

Greetings to all,
I am on the planning stage for a setup on a boat. Now I am planning to use 48V batteries and 4-5 solar panels. But from what I have read the voltage from panels needs to be higher than 48v to be able to charge? Is this correct statement or not?

If the panel is 24v, do I need to connect them in series to double the voltage?

It depends on what controller you have. Some will require you wire the panels in series to get the voltage significantly above the battery voltage. These are most versatile because you would need smaller wire to handle the watts. But there are boost controllers that will take the panel voltage and boost it to the battery voltage. Best only if you are trickle charging… depending on the size of the battery and the needs of the loads… I would think mppt and an array large enough fo handle your loads with the panels in series make the best sense to me.

 

[freemanson]

I have nothing yet =) Still in the planning stage to avoid doing purchase mistakes that in the end will cost more and at the same time I am trying to wrap things around my head - new area of interest and much to take in.

Will try keeping things efficient, and simple as possible.

So to wrap things up -
You can use 12 v solar panels to charge a 48V battery but ONLY if you connect the 12v in series to get more than 48V. If more then there is this magic box called MPPT controller that downgrades the output voltage from the solar panels to fit the voltage of the battery?

What happens when a mppt controller fails?

If I connect one 12v panel and one 24v panel in series - will it be 36v-isch?

I will when weather permits drive the electric motor only on solar panel and not draw current from the batteries. Does the MPPT controller handle this also or do I need something else?

 

[freemanson]

Your controller takes what ever voltage the panels produce and converts it to the correct voltage for the battery.

Thanks will watch it now.

 

[freemanson]

Umm, well no, that is not correct. What a MPPT controller can do is transform the incoming voltage DOWN to what the battery wants to charge at. A controller can NOT increase voltage. So, a single 12V panel can never charge a 24V battery. But, two solar panels wired in series could, with an MPPT controller.

But, to answer FM's question, MPPT controllers (not PWM controllers) will take the incoming voltage and transform it down to make the voltage the battery wants. Keep in mind though that 12V solar panels do NOT put out 12V, and 24V panels do NOT put out 24V.

A standard 36-cell 12V solar panel has a Vmp of ~18V. A standard 60-cell panel puts out ~30V, and 72-cell 37.5V. A MPPT controller needs some overhead voltage above what the battery needs. Midnight Solar says +30%. A 48V battery bank will want to charge at anywhere between 50-59 volts, and for lead-acid that needs equalization, up to 64V. So, you need a panel string that is ~ 58V X 1.3X = 75.5V.

So, wire your panels to put out at least 75-78V, and you should be fine. That means five 36-cell panels in series, or three 60-cell panels, or maybe just two 72-cell panels.

Thank you very much for reply. So in an essence I was on the right track with the voltage. Need to do some reading onte the MPPT and PWM controllers.
Actually I came here after that google Bard AI said I could charge 48v with a ONE 12v solar panel but with the use of MPPT controller. Thought is was wrong so here I came.

 

[Supervstech]

Thank you very much for reply. So in an essence I was on the right track with the voltage. Need to do some reading onte the MPPT and PWM controllers.
Actually I came here after that google Bard AI said I could charge 48v with a 12v solar panel but with the use of MPPT controller. Thought is was wrong so here I came.

Like the video and others have said...

SOME mppt controllers can boost the voltage, but it is not a wise choice.

 

[Crowz]

I have nothing yet =) Still in the planning stage to avoid doing purchase mistakes that in the end will cost more and at the same time I am trying to wrap things around my head - new area of interest and much to take in.

Will try keeping things efficient, and simple as possible.

So to wrap things up -
You can use 12 v solar panels to charge a 48V battery but ONLY if you connect the 12v in series to get more than 48V. If more then there is this magic box called MPPT controller that downgrades the output voltage from the solar panels to fit the voltage of the battery?

What happens when a mppt controller fails?

If I connect one 12v panel and one 24v panel in series - will it be 36v-isch?

I will when weather permits drive the electric motor only on solar panel and not draw current from the batteries. Does the MPPT controller handle this also or do I need something else?

Yep it all adds up. 12v + 24v = 36

12v + 12v + 24v = 48v etc.

If the controller fails it just quits charging the batteries.

 

[MisterSandals]

If I connect one 12v panel and one 24v panel in series - will it be 36v-isch?

Yes but the panel with the higher amps (Imp) will clipped to that of the lower amp panel.

So where watts = amps x volts, the extent of the amp clipping will result in the extent of potential panel output. If you provide actual example of panels, the math can be shown.

 

[Crowz]

Yes but the panel with the higher amps (Imp) will clipped to that of the lower amp panel.

So where watts = amps x volts, the extent of the amp clipping will result in the extent of potential panel output. If you provide actual example of panels, the math can be shown.

Completely correct !

Use the calculator in my signature to see what you will get when combining panels of different capacity.