question

nesswill avatar image
nesswill asked

Sorry to ask.. Tail Current

I have an MPPT 450/100 & a Smart Shunt 500ah with 1040ah @48v of AGM Batteries (increasing to 1560ah by the end of the year), i use about 17kwh per day, is it OK to leave the Tail Current set to 4%?

Everything has been left on recommended setting for AGM, sorry to ask this when i am sure it's been covered before i just can't find it.

This is an off-grid setup.

Dave.

SmartShunt
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7 Answers
pwfarnell avatar image
pwfarnell answered ·

I would reduce this down to 1%-1.5% for AGM to make sure that they really are full before going to float. Some AGM manufacturers specify as low as 0.5% tail current. My boats AGM bank is set at 1%. The first time you do this make sure that the tail current will go this low, if the batteries are aged then they may settle at a higher tail current.

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kevgermany avatar image
kevgermany answered ·

I think these values are from shunt/battery monitor, not charger.

Charge efficiency is probably a bit high. Maybe knock it down to 90%

If you're getting enough prolonged cloud to reduce charge current to below the tail current, you may want to increase charge detection time to prevent false positives.


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nesswill avatar image
nesswill answered ·

Thank you i will do that.

The batteries are all new.

Cheers

Dave.

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kevgermany avatar image kevgermany ♦♦ commented ·
Fact of life. AGM charge efficiency isn't that high, sadly.
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nesswill avatar image
nesswill answered ·

Hi just checking does this looks ok to you?

tail.jpg


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nesswill avatar image
nesswill answered ·

Thank you - done.

Dave.

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nesswill avatar image
nesswill answered ·

Just to confirm that the Smart Shunt has priority over the MPPT 450/100 and controls the charging?

Or do i need to match this too? sorry to be a pain just want to ensure its all set-up correctly.

mppt.jpg

Dave.


mppt.jpg (91.8 KiB)
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kevgermany avatar image kevgermany ♦♦ commented ·

The shunt does not exert any direct control.

In systems with a GX device, DVCC enabled, current measurements from the shunt will be used to limit MPPT output.

The settings in previous posts are aimed at getting the monitoring side to give accurate battery state of charge readings.


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nesswill avatar image
nesswill answered ·

Ok thanks for all your help, i have a GX Cerbo with DVCC enabled so i think all is good.

Thanks again for your help.

Dave.

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