question

mjs88 avatar image
mjs88 asked

Novice need battery shunt advice

Hello :)

Total novice looking for advice on battery shunt settings.

We have a Smart Shunt (500a), 95ah 12v 1140wh AGM class A leisure battery fed by a 130w solar panel and MPPT 75/15 controller.


I’ve read the smart shunt manual and gone with what I thinks best. Waited for a float charge status with no draw and synchronised to 100%, consumed about 14ah (evening / overnight) but woke up this morning with the battery at 100% even though the controller is still in bulk charge so don’t think this is right?

Any advice greatly appreciated.

Screenshots of battery shunt and solar controller settings in app

914bbf82-8b73-4bf0-a76f-08d5ada2f6dd.png

cd395b6b-aefb-4e1e-b091-224a0db73562.png

battery chargingSmartShuntSolar PanelAGM Battery
176dc3c5-f228-45fe-b229-9035175cd7a4.png (344.7 KiB)
cd395b6b-aefb-4e1e-b091-224a0db73562.png (353.3 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
seb71 avatar image
seb71 answered ·

Set the "Charged voltage" in the Shunt settings to 0.1V lower than the Absorption voltage in the MPPT settings.


Also you might want to increase the "Charged detection time" in the shunt settings.

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.

JohnC avatar image
JohnC answered ·

Hi @MJS88

Personal opinion, but you can still choose to sync in Float to pick up that last 1-2% SOC with Pb batts. . I use 13.4 Charged V for a Float of 13.6V, the 0.2 difference to avoid a lower temp-compensated V in hot weather. So if you stick with the 13.8V Float, at the very least raise your CV to 13.6V.

But at this V the 4% Tail is way too high. I use 0.7% in winter, so try maybe 1%. Depends on the characteristics of your batts, but if they're a little sluggish reacting, passing cloud can drop the Amps, but the V doesn't come down so fast, causing premature sync. You can actually watch this happen on the trends graph. So yes, I raised the Detection Time to 5 min to dodge this.

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.