epever absorbtion time

[glamsland]

hi.

i have a epever up-hi 3000 hm10022 hybrid inverter/charger.

Li-ion 3.7v/cell 7s 24v/270A battery
1000w solar

recomended settings from dealer:

Boost 28,7v
Absorbtion 120min

float 28.5v
Boost reconnect 28v

today, its sunny all day, charging in boost from 27.5v .. . all good..

then when it starting to get close to boost voltage (28.7v) i wanted to pay attention to learn some about the behavior of the CC .. at 28.65 the amp started to be lower and lower until about 10 Amp. Then it hit 28.7v, and then BAM, the amp went to zero and CC goes to Float ! ? ... Interesting... still lots of sun.. The Boost/float setting works, battery is ok , but where is the Absobtion time??? I was expecting to see the amp slowly decrease until almost Zero amp, AFTER the 28.7v . then go in fixed voltage mode at 28.7v and ABSORBE! ,- and then go to float mode... The amp went from like 15amp to 10 to suddenly zero in like 10 min.

Am I missing something here?

Runar

 

[sunshine_eggo]

then when it starting to get close to boost voltage (28.7v) i wanted to pay attention to learn some about the behavior of the CC .. at 28.65 the amp started to be lower and lower until about 10 Amp. Then it hit 28.7v, and then BAM, the amp went to zero and CC goes to Float ! ? ... Interesting... still lots of sun.. The Boost/float setting works, battery is ok , but where is the Absobtion time???

You were looking right at it. When you saw the current tapering, that's absorption. The unit likely gave itself a little wiggle room at 28.65 instead of going to 28.70V..

I was expecting to see the amp slowly decrease until almost Zero amp, AFTER the 28.7v . then go in fixed voltage mode at 28.7v and ABSORBE! ,- and then go to float mode... The amp went from like 15amp to 10 to suddenly zero in like 10 min.

Am I missing something here?

Runar

Yes. You are mistaking normal behavior for abnormal behavior. Absorption time on lithium is generally pretty short. Lithium chemistry fills and current tapers very quickly in the upper leg. 4.1V on 3.7V chemistry is definitely in the upper leg. Your MPPT may have an unpublished tail current specification of 10A causing the cut off.

3.7V Lithium is generally fully charged at 0.05C and 4.2V/cell. 0.05C in your case is 13.5A. 10A is lower than 0.05C, so you're at a higher SoC than you would be at 0.05C.

 

[glamsland]

You were looking right at it. When you saw the current tapering, that's absorption. The unit likely gave itself a little wiggle room at 28.65 instead of going to 28.70V..



Yes. You are mistaking normal behavior for abnormal behavior. Absorption time on lithium is generally pretty short. Lithium chemistry fills and current tapers very quickly in the upper leg. 4.1V on 3.7V chemistry is definitely in the upper leg. Your MPPT may have an unpublished tail current specification of 10A causing the cut off.

3.7V Lithium is generally fully charged at 0.05C and 4.2V/cell. 0.05C in your case is 13.5A. 10A is lower than 0.05C, so you're at a higher SoC than you would be at 0.05C.

Thanks for explaning. Allways good to learn something new about my solar! Thank you!