question

tony-c avatar image
tony-c asked

Quattro BMS Assistant

Just set up the Quattro Lithium BMS assistant with the following selections:

=The BMS has one contact that switches only on a high cell condition

= The battery is full when the Temperature sense input = CLOSE

=Force to FLOAT and Set SOC to 100% when battery Full

Closing the contact did set the charger to Float and the SOC to 100%. However when the contact was opened the charger did not revert to bulk/absorption it stayed in FLOAT

Change the action to "Disable Charger" and it worked as expected, toggling between charging and disabled in sync with the BMS relay contact.

My preference is to force the charger to Float rather that to disable it.

Any advice will be appreciated

BMSAssistants
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
wkirby avatar image
wkirby answered ·

Once in Float (with you BMS contact open), the battery Voltage must drop below a certain level to switch back to bulk.
When configured for Lithium batteries, the battery Voltage must drop by 0.2V below the configured Float Voltage for a 12V battery, (0.4V for 24V battery or 0.8V for 48V battery).

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.

tony-c avatar image
tony-c answered ·

Thanks for that explanation. In the Victron article "Connecting other lithium systems to Multis and Quattros" it says When using Switch to Float option, configure the float voltage no a level where the batteries are no longer being charged.

in a 12v system what would that be?

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.

wkirby avatar image wkirby ♦♦ commented ·

That's difficult to answer without being there. You need to tweak this to suit your exact batery bank.
You need to set this so that no current (or very little, maybe 100mA or so depending upon the size of the battery bank) flows into the battery when it has settled in its Float state.
Maybe start at around 13V and work your way down if necessary.

0 Likes 0 ·