question

spitzer avatar image
spitzer asked

SmartSolar MPPT 100/20-48 Voltage Drop on Load Output

I'm unsing a SmartSolar MPPT 100/20-48 with a 48V LiFePo4 Battery (5.2kWh) and a 1200W Inverter. This evening (no PV Input for 2 hours), i noticed the SmartSolar was quite warm. At that point the inverter was drawing 18A @ 50V (~800W Output Load). The MPPT-App showed a significant higher Battery-Voltage as the Inverter.

So i took my 5-digit multimeter and measured the voltage drop on the SmartSolar MPPT directly at the screw-terminals of the MPPT. Batt- to Load- 40,5mV and Batt+ to Load+ 1,665V (!). So a total of over 1,7V @ 18A => a Power loss of over 30W in the SmartSolar.

This seems far too much. Anybody with similar values?

SmartSolar PID: 0xA060 FIRMWARE: 1.59 SERIAL_NUMBER: HQ2138MRG9H

regards

Bernhard


MPPT Controllers
1 comment
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.

Alexandra avatar image Alexandra ♦ commented ·

@Spitzer

How is it wired up?

Are you pulling the inverter load through the load output of the mppt?

1 Like 1 ·
2 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

At 48V the max. load output current is only 1A!
If you want to run higher loads you need to use the load output to switch a relay.

1672164974331.png


1672164974331.png (155.5 KiB)
1 comment
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.

spitzer avatar image spitzer commented ·

d-oh! Missed that one in the datasheet.
Yes, i am currently running the full load current through the MPPT (not for much longer...)
Too bad, it would have been a perfect fit with my inverter, not to use an external relay (and 80V 60A MOSFETs are not hard to get...)

thanks all!

0 Likes 0 ·
chrichri avatar image
chrichri answered ·

Can one please explain this limit to 1A. For me it doesn't make any sense. Why if operating with 24V, 20A is no problem and operating in 48V the maximum is 1A? The MOSFET resistance is the same, so Powerloss is the same...

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.