question

qt12070 avatar image
qt12070 asked

At what voltage does a Muliti-plus move from float to absorption charge?

Hi - we have a pair of 2019 Multi plus 24V/3000VA/70A-16/230V charging an AGM battery bank of 765AH capacity. The devices work fine but seem very reluctant to switch into absorption mode when charging, I've seen this post explaining that bulk mode kicks in 2.6v below the float level that is set for 24v AGMs: https://community.victronenergy.com/questions/175/how-do-quattro-and-multiplus-decide-to-switch-from.html Does anyone know what logic is used to switch from charging in float to absorption? Is it a voltage below float again? I'm finding that they will start charging at around 120 amps but they stay in float mode and will not go into absorption at all, even when we have used around 25% of the bank capacity and the bank voltage has dropped by nearly 2v. Thanks, Richard

MultiPlus Quattro Inverter Chargerbattery charging
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
Alexandra avatar image
Alexandra answered ·

@qt12070

Absorption happens after bulk as it is similar to bulk where it is keeping the voltage to the target set, but is using less amperage and spending time reversing the chemistry in the liquid, then it drops onto float. So it has to drop into bulk to begin the charge cycle again.

If you are not switching into bulk again then possibly some settings need to to be tweaked.

https://community.victronenergy.com/questions/63640/charging-bulk-absorption-and-float.html

1619240548230.png


1619240548230.png (20.8 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.

qt12070 avatar image
qt12070 answered ·

Thanks Alexandra - that makes sense now. Our earlier model Victron inverters would switch directly into absorption mode from float when AC was reconnected and the bank had a partial discharge, They didn't need to go to bulk first of all. It looks like the newer devices work differently (or my old ones were misbehaving!) The voltages are set as per the Lifeline AGM specs (26.6v float, 28.6v absorption) with temperature compensation enabled. Appreciate your help, looks like they are working properly, Richard

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.