I’ve used a Midnite Classic for years, just got a Victron 150v 35a controller. The transitions from Bulk, Absorb, Float, are let’s say, strange, different.
First off, Absorb was reached today, 56.4v, the 1hr timer started. Some clouds moved in, Absorb voltage couldn’t be maintained, a full volt drop on the bank , yet the controller stayed in Absorb, and the timer carried on, why?
If it can’t hold Absorb voltage, it should stop the timer, go back to Bulk, until Absorb is reached, rinse and repeat. This isn’t a rebulk issue, Float hasn’t been reached yet.
The Absorb timer is set for 1hr. It’s not even at the Absorb voltage first off, but the timer continues on, and the system goes to Float after 28 mins of some false timed Absorb cycle. What’s with that. The system shouldn’t be going to Float until a full Absorb time period has been reached, 1 hour of true Absorb. Tail current is disabled.
There is a little wriggle room regarding the absorp charge state and battery voltage, and the absorp timer.
Should loads or lack of sun allow the battery voltage to drop a bit, the absorp timer continues to run.
Should loads or lack of sun drop the battery voltage by a bit more, the absorp timer is paused, and the timer will increment once the battery voltage reaches the bulk/absorp voltage setting.
This prevents nearly fully charged batteries from being held at a high voltage for undesirable times.
IIRC the voltage can drop by 0.15 - 0.2v (for a 12v battery) before the absorp timer is paused.
Are you worried about Absorption time because of balancing?
Victron doesn’t rebulk when clouds drop the voltage. It stays in Absorption based on its previous state. This avoids constant cycling and long charge sessions on cloudy days, and it’s normal behaviour for their controllers.
Absorption was set for 56.4v. When it reached that voltage in Bulk it switched to Absorption, and the timer started, as it should. I had Absorption set for 1hr. Tail current is disabled. Clouds moved in shortly after. The bank voltage dropped to 55.2v. The controller stayed in Absorption mode, and the timer continued to run. It should switch back to Bulk with that much of a voltage drop, and the Absorption timer should have paused. Neither of those things happened. Then it transitioned to Float, still not even back to the Absorption voltage, after 28 mins total time from initially hitting Absorption. So the batteries received basically very little of the Absorption cycle I had set. That’s not acceptable, and not the way it was programmed. It should have been in Bulk until reaching 56.4v, then switched to Absorption, the 1hr timer starts. If loads are too great, or no sun, and the voltage drops enough, it should switch back to Bulk, pause the Absorption timer. I programmed the controller to give my battery bank 1hr of Absorption at 56.4v, and the batteries didn’t get anything close to that. I’ve been off grid for 20 yrs now using Morningstar, Midnite, controllers, I know how to program them, and how they “should work”. This is simply ignoring what it was programmed to do. The only thing it did properly as programmed, was switch from Bulk to Absorption at 56.4v, that’s it.
Do check that you have selected Li battery preset before making any changes to voltage presets. LA battery starting point will have temp compensation and adaptive absorption enabled.
