Charge controller settings - going to float too soon

jdobush · March 2021

I'm having some trouble with setting up my charge controller to my new batteries - specs below. I can set the bulk and float voltages but not the absorb time (which happens so fast i haven't even caught it in the act). The last two sunny days it's charged great in bulk until about 90% then does something in absorb then hits float soon after. Then the controller proceeds to try to charge the batteries in float for the rest of the day.

I've read this is a common issue with daily cycling batteries and solar - but I don't know if upping all of my voltages to compensate is the right move? I did already up the voltage settings by 0.2v to make up for 0.2v offset in the charge controller. Otherwise voltage at the batteries right now is spot on to the specs from the manufacturer. I know buying a better charge controller would help but.. not into another 500 expenditure for something that isn't broken..

24v 606ah bank - Northstar Blue+ agm batteries
Aimscorp 60amp MPPT charger - set to 28.2v bulk, 27.2v float (at battery - settings at 28.4, 27.4 on controller)

Any suggestions? Is float voltage charging long term detrimental to a battery? Or just inefficient?

mcgivor · March 2021

By description of the symptoms being experienced there may be underlying issues related to the setup oasis a whole, but lost battery capacity would be my first guess.

Providing additional information would be helpful, average overnight loads, PV array capacity, geographic location, battery format and topography......as much information as possible.

Float should only occur after the battery is fully charged in the absorption stage, the float value is to maintain a voltage that is neither charging nor dischargeing, so as long as it is set correctly it is neither detrimental nor inefficient,

jdobush · March 2021

These are new batteries. Brand new in fact, 4 days worth of usage now. I'm trying to dial everything in so I Don't lose capacity.

I have 1,650 watts of solar panels. We are just starting to get some decent sun - but the charge controller is regularly bringing in 30-40 amps in Bulk when mostly full sun. I've been limiting my usage to minimal (less than 20% of capacity) while I sort this out.

For whatever reason - my charge controller doesn't like to hold in Absorption. (I'm working to determine why, but don't get me started on Aimscorp) I have had this controller for a few years. So what I have happening is I get to absorption voltage (roughly at 90%SOC), and within a matter of minutes I'm kicking into float, which is still trying to pull in a ton of amperage because I didn't get a proper absorption cycle. I have to blame the controller for now - unless someone tells me otherwise? I'm looking for options to make due before I go buy a new controller with better adjustments available.

My question about float charging was because I am being left with 60+ahs to charge when it kicks into Float. (trying to correct this)

mike_s · March 2021

jdobush said:
Aimscorp 60amp MPPT charger - set to 28.2v bulk, 27.2v float (at battery - settings at 28.4, 27.4 on controller)

The manual for that controller doesn't say anything about there being a setting for absorption time. Not sure what's up with that, or how the controller determines how long to stay in absorption. And, the manual is just plain confusing. In one place, it talks about voltages for "Bulk, Absorption (equalize), and Float", next to a diagram showing settings for Bulk, Float, and Equalize. Elsewhere, it shows settings for Bulk, Absorption, and Float. And the charging description never refers to the Bulk voltage, it just says it does bulk charging until it gets to the Absorption voltage, then switches to CV mode (no mention of for how long). Then it says it switches to Float "at the end of the Absorb Charging time", which is the only place that's mentioned in the manual.

I suspect what they're doing is when they get to the bulk voltage, they do nothing but change the display to indicate absorption, and when they reach the absorption voltage, they immediately switch to float. They're doing it wrong.

I'm going to say it's just a really poorly implemented controller, from people who don't know what they're doing. Sorry.

jdobush · March 2021

mike_s said:

jdobush said:
Aimscorp 60amp MPPT charger - set to 28.2v bulk, 27.2v float (at battery - settings at 28.4, 27.4 on controller)

The manual for that controller doesn't say anything about there being a setting for absorption time. Not sure what's up with that, or how the controller determines how long to stay in absorption. And, the manual is just plain confusing. In one place, it talks about voltages for "Bulk, Absorption (equalize), and Float", next to a diagram showing settings for Bulk, Float, and Equalize. Elsewhere, it shows settings for Bulk, Absorption, and Float. And the charging description never refers to the Bulk voltage, it just says it does bulk charging until it gets to the Absorption voltage, then switches to CV mode (no mention of for how long). Then it says it switches to Float "at the end of the Absorb Charging time", which is the only place that's mentioned in the manual.

I suspect what they're doing is when they get to the bulk voltage, they do nothing but change the display to indicate absorption, and when they reach the absorption voltage, they immediately switch to float. They're doing it wrong.

I'm going to say it's just a really poorly implemented controller, from people who don't know what they're doing. Sorry.

No apologies needed, because that's exactly the conclusion I came to. I appreciate you taking the time to look through the manual (or lack thereof) I've told myself that the manual must just be a bad translation from chinese to be so bad.

I'll try their customer service one last time next week, but I don't want to waste my new batteries with an incomplete charge every day. I wish I had known enough to avoid them years ago but such is life.

Charge controller settings - going to float too soon

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