Hi,
My 2 mppts go to absorption instead of bulk. 250 Ah Lithium Battery is half charged at 13.2 v and both my mppt are in absorption.
My stats are 14.2V for abs , 13.3v for float. I dont get it. Is it a problem on the mppt ?
I have seen couple of times they also stop charging , they are off.
One Mppt is linked with a 100w panel . The other mppt has 4 x 30 w panels on the roof
Going to absorption early is a sign of a high resistance between the mppt and battery such as a poor or loose connection, corrosion, failing isolator. As with any issue you need to check both the battery terminal voltage and the mppt terminal voltage with a multimeter to see if this is the case.
thanks, I just checked the voltages.
lithium battery terminals > 13.15v
100w panel mppt > PV 19.45V and Battery 14.14V
4 x 30 w panels array mppts > PV 40v and Battery 13.68V
Both MPPT are blinkin green (battery life) and yellow slow blink (absorption)
I also checked all the cables and connections , everything seems ok, bolts are tight.
Something is not right as you have a voltage drop of 1V from MPPT to battery. Use your multimeter on each connection to find where the voltage drop is.
No, I have small fuse like this in my setup. Now, I did measure again, there is less sun now.
I have Mppt with 4 x 30 W > 13.3V . Bulk
Mppt with 100 W > 13.25V . Float
Battery with 13.10 V
I have disabled and re enabled the mppts in victron app. One mppt went from absorption to Bulk. The other goes to Bulk for a few second then comes back to float.
But Sunlight is weak now.
There is more sun today, and I checked the cable and 10 A fuse between MPPT and battery as you said . Its a bit abnormaly hot. The head of the fuse is hot too.
Maybe thats why voltage is goin to 14.2v very quickly as the Sun is shining.
10A is realistically too low for 120W, the fuse needs to be rated around 30% higher than the maximum continuous current. The automotive type fuse you have can suffer from poor contact in the spring clips causing heat and voltage drop.
yep. both 10A fuses were melted and one of the terminals was black.. I think I will change thoses automotive type fuse for MIDI fuse, and maybe put 15 A , cable is 4mm2 , I think its fine.
Will try again tomorrow.
