question

thijs-vh avatar image
thijs-vh asked

MPPT 75/15 charging low voltage

img-1721.pngimg-1720.pngimg-1722.pngI have a new installed MPPT smart charger with a 60W panel. I have used in on my boat last week. It seems to be charging enough (have seen 51W charging). The panel gives about 20V but the output to the battery is too low and doesn't reach the voltage settings for bulk mode. I tried to increase this voltage in setting but there's no difference.

The MPPT is connected to the same wires as the battery charger (which charges with higher voltages)

Questions:

1) can I do harm to the batteries charging at low voltages?

2) What could be wrong en how should i get the correct charging voltage?

MPPT SmartSolar
img-1720.png (241.0 KiB)
img-1721.png (207.5 KiB)
img-1722.png (210.4 KiB)
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

2 Answers
klim8skeptic avatar image
klim8skeptic answered ·

You are using more power than your puny 60w solar panel can provide,

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

thijs-vh avatar image
thijs-vh answered ·

unfortunately there is little power consumption, only 0,3A from consumers. The mppt gives max ca 13,3v and measured directly on the battery it is even lower. I need a bit higher voltage to charge correctly

3 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

klim8skeptic avatar image klim8skeptic ♦ commented ·

"unfortunately there is little power consumption"

That is not what your history is showing..

Your panel managed to harvest 290wh, but that was not enough to get the battery charged.

0 Likes 0 ·
thijs-vh avatar image thijs-vh klim8skeptic ♦ commented ·

That is probably true (although my BMV700 told me it was fully charged). My main concern is that my battery should be charged somewhere between 13.8 and 14.4 volts but the MPPT doesn't seem to charge at these voltages. The panel had a VOC of 24V and VMP of 20V so it should be enough to generate 13.8 at least. I tried to raise the "Absorbtie spanning" to 14.9 but there's no difference. The MPPT keeps charging around 13.3V.

0 Likes 0 ·
Matthias Lange - DE avatar image Matthias Lange - DE ♦ thijs-vh commented ·
As long as your load is bigger, equal or just a little bit smaller then the PV power the voltage will not rise.

To charge your batteries the charging current has to be bigger as the load current.

You have to turn off/disconnect all loads or you need more PV power.

0 Likes 0 ·