12 volt /24 volt

vortac55

New Member
Joined
Sep 6, 2022
Messages
10
I have 2 -175 watt panels on my boat Wired in parallel. Wired from panel #8 wire to an MPPT controller
Load side direct to charge 4-4d lead acid. Charging 12 volt system

Parallel /series always the question of which way to wire High voltage less amps /low voltage high amps

If I re-wired to 24 volts does the MPPT controller recognize and output and adjust to my 12-volt system? Does not seem likely

2nd
There is an existing invertor in place
Not sure if the internal digital readout of the charge state ( voltage ) of the battery is accurate.
Do you think this is because I am going right to the batteries?
I did not trace it out but the existing wires go off the batteries somehow connected to the existing charging system and invertor and the house electric panel

My battery connections
I have the ground to the last battery and the positive to the first battery parallel
I saw another parallel connection connecting from the middle out

Thanks in advance for any advice you can share
 

pollenface

Solar Addict
Joined
Nov 14, 2020
Messages
1,059
Location
Perth, Australia
YES if you are talking about wiring your panels in series to charge your 12v system (provided you stay within the PV input voltage specs of the controller). This is useful for long wire runs where you want to minimize voltage drop, if it's less than 30ft the benefit of doing so would be negligible.

I didn't follow your 2nd question but I suggest using a multimeter for voltage readings.
 

chrisski

Solar Boondocker
Joined
Aug 14, 2020
Messages
4,036
There is an existing invertor in place
Not sure if the internal digital readout of the charge state ( voltage ) of the battery is accurate.
Do you think this is because I am going right to the batteries?
Having a shunt is an accurate way to measure battery state. Voltage is not an accurate way due to voltage sag under load. Voltage also needs to sit with no load for a bit to be accurate. That voltage battery reader you have is a guide and can be a bit off.

Specific gravity with a hydrometer for flooded lead acid is the most accurate.
 

vortac55

New Member
Joined
Sep 6, 2022
Messages
10
Thanks

From my solar panels, it is approx 30 feet of wire give or take

I am not sure what the PV value is I am attaching the sticker from the back of the panel

I attached the MT50 readout do not fully understand the readout more on the battery side. does not seem to match up with the NAv station readout
 

Attachments

  • solar panel sticker.jpg
    solar panel sticker.jpg
    824.8 KB · Views: 13
  • mt 5o read out.jpg
    mt 5o read out.jpg
    626.1 KB · Views: 12
  • mt 50 read out 1.jpg
    mt 50 read out 1.jpg
    291.7 KB · Views: 12

mikefitz

Photon Sorcerer
Joined
May 28, 2020
Messages
1,783
The panels are producing current at a voltage determined by the controller, after power conversion by the controller sending current into the battery at battery volts.
What is the difference between controller reading of volts and current and your other instrumentation?
 

PVorBust

Solar Enthusiast
Joined
Jul 25, 2021
Messages
93
If I re-wired to 24 volts does the MPPT controller recognize and output and adjust to my 12-volt system? Does not seem likely
Yes, that is one of the benefits of an MPPT controller.

For small systems, series connections are better as it will give you lower losses and more hours of charging per day.
 

Vigo

Solar Addict
Joined
May 26, 2022
Messages
818
Location
San Antonio Texas
For small systems, series connections are better as it will give you lower losses and more hours of charging per day.
That really depends!

I agree that losses tend to be more critical in small systems where there is no 'excess capacity' to make you not care about losing some percentage points.

But more hours of charging per day totally depends on how those panels are oriented and what the solar conditions are. For example, if you have 1 panel in sun and 1 panel in shade, it would be better if they were parallel. If you have one facing the morning sun and one facing the afternoon sun, it would be better if they were in parallel. In those cases parallel would result in more 'hours of charging per day'.

In my opinion the benefit of series wiring is limited to having either a large number of panels, or long distances of wire. If you have neither, it would be better to be in parallel most of the time, in my opinion.
 

PVorBust

Solar Enthusiast
Joined
Jul 25, 2021
Messages
93
Ok, yep, both situations that would suit parallel connections.
Unless otherwise specified, it's reasonable to assume the panels are pointing north (or south depending where you live). Boats of course are a whole bag of trouble.
The OP has two panels, so that's the sort of scale I was thinking.
 
Top