Still confused by varied vendors using different terminology and levels for the same settings

[DixieMtCR]

My SCC's are EpEver clones sold under the rebranded name of "ACOPOWER MY40 Midas Y Series, MPPT Solar Charge Controller." They are 40amp 12v/24v auto detect. I am using them for a 24vdc battery bank, see below for configuration.

The SCC's have various settings for charge rates at various levels of discharge. The manual for the SCC has parameters for each of these levels. See Attachment.

They use the terms BOOST, FLOAT. and EQUALIZE. When looking on the web, there are other terms such at BULK.

Questions:
** In the attached chart there are values for each of the settings.
**** Are the numbers correct?
**** Do the numbers represent the level where the settings kicks in, or where it shuts down to lesser current?
**** What is meant by BOOST, FLOAT, and EQUALIZE, and how do they relate to BULK?
**** Should I set the charging parameters using the "USER" section to change parameters to custom levels?

The batteries in the battery bank are Sealed Lead Acid Maintenance Free 100Ah batteries. There are 8 of them wired 2s4p for 24volts.

The reason for asking is that on full sunny days at SOLAR NOON I expect the solar charge current to be running full throttle when the battery voltage is 25.0v. The most I have ever seen for charge current at each SCC at the same time is about 22amps each... which is 1650watts. But at ~27V one or more of the SCC's will drop to between 200ma to 5amps and stay there. The Victron Smart Shunt then shows pretty much a trickle charge (0.85-1.50amps) even though it shows that the batteries are only at 93%. Something is amiss.

Thanks ahead of time for whoever can shed a little light on this stuff. I pretty much understand the electronics part but I do not know/understand the language of battery charging.

Ken

Solar Electricity Investment.
** 1840 watts of Solar panels = (2 sets) of 6 panels/100w each, wired 3s2p. (1 set) of 2 panels/320w each, wired 2p.
** (3) 100/40 MPPT charge controllers
** (8) 100Ah Sealed Lead acid batteries, wired together as 2s4p, 24volt system
** (1) 4000 Watt Pure Sinewave Inverter
** (1) Victron SmartShunt for monitoring Battery status
** (1) 10-circuit manual transfer switch. Connects the solar through an RV 30amp inlet box to the load center. 120v only with solar.
Most of the day the items in the house consume between 500-800 watts. Microwave and coffee pot add another 1500-1800 each for the time that they are used. Oregon is NOT known for its sunshine, so, solar energy must be monitored.

 

[E. Cho]

Not trying to put you off but there is a resource section and categories and lots of info there, such as:

Victron's Energy Unlimited

which does a pretty good job at explaining things. As well, as this stuff has been explained before, search these forums for lead acid charging, as well as the web and for YouTube videos.

You are in a behind already if you don't know the difference between terms. Bulk and Boost are interchangeable. These are then held for an Absorption period of time which you/battery mfg sets or suggests to achieve 90-100% state of charge (SOC), after which, the charge controller settings drop the charging voltage lower to Float, where 0-minor current is drawn to hold, or float, the battery charged voltage at or near full and or until a load / appliance draws it down below the float and or then below the bulk/boost charge controller settings, then the cycle repeats itself, often many times in the same day depending on charging and current drawn / power used and battery capacity as per the charging or loads.

Equalize is a special cycle for lead acid batteries used approximately 1 x every 30 days to further increase the battery voltage higher than bulk charging, so as to cause the lead acid battery water to "boil" or move, so as to try to remove sulphation from the lead acid plates, which occurs at lower battery voltage and time. Sulphation of plates occurs faster when lead acid batteries are under charged and over used or drawn down below 50% capacity. Mfg usually recommend an equalize cycle of 31-32 volts for a 24 volt battery held at this high voltage for 2-5 hours.

Equalizing charge cycles are best done with a fossil fuel generator as solar may not hold the high constant voltage due to clouds, sun moving, panel shading, etc..

Also look at tutorials at Solar Retailers which you can find using Google.

 

[sunshine_eggo]

3 phases of lead acid charging:

1) bulk = constant current until the absorption voltage is hit
2) absorption = constant voltage where the voltage is held constant and current tapers as needed.
3) float = the voltage at which you hold the battery to maintain it at 100% SoC.

This diagram shows the 3 phases. I've circled the two voltages:



Please focus on the concepts, not the actual values as they are generic.

There are only TWO voltages: absorption and float.

BELOW the absorption voltage is the bulk phase.
AT the absorption voltage is the absorption phase.

BULK/ABSORPTION voltage is often referred to as BOOST in the Chinese made products. They don't distinguish between phases and call the whole thing BOOST referring to the single voltage.

EQUALIZE is a deliberate over charge to help flooded cell batteries eliminate sulfation and recover capacity. It is generally not needed for SLA/Sealed/AGM/GEL batteries, but some manufacturer's specify one. Sometimes, one might use equalize to periodically drive the battery to the peak recommended voltage while using the lower one routinely, e.g., let's say the battery specifies an absorption voltage of 14.4-14.8V. You would set absorption to 14.4V and set equalization to 14.8V once a month.

With the charge controller defaults for SEALED, you should be fine.

Your panels produce a total potential charging current of 75A. Your 400Ah battery should likely be charged in the 40-80A range depending on battery specification.

 

[DixieMtCR]

3 phases of lead acid charging:

1) bulk = constant current until the absorption voltage is hit
2) absorption = constant voltage where the voltage is held constant and current tapers as needed.
3) float = the voltage at which you hold the battery to maintain it at 100% SoC.

This diagram shows the 3 phases. I've circled the two voltages:

View attachment 102362

Please focus on the concepts, not the actual values as they are generic.

There are only TWO voltages: absorption and float.

BELOW the absorption voltage is the bulk phase.
AT the absorption voltage is the absorption phase.

BULK/ABSORPTION voltage is often referred to as BOOST in the Chinese made products. They don't distinguish between phases and call the whole thing BOOST referring to the single voltage.

EQUALIZE is a deliberate over charge to help flooded cell batteries eliminate sulfation and recover capacity. It is generally not needed for SLA/Sealed/AGM/GEL batteries, but some manufacturer's specify one. Sometimes, one might use equalize to periodically drive the battery to the peak recommended voltage while using the lower one routinely, e.g., let's say the battery specifies an absorption voltage of 14.4-14.8V. You would set absorption to 14.4V and set equalization to 14.8V once a month.

With the charge controller defaults for SEALED, you should be fine.

Your panels produce a total potential charging current of 75A. Your 400Ah battery should likely be charged in the 40-80A range depending on battery specification.

Hey Sunshine! HaHa

Thanks for the information and the graphic as well. They have been most helpful. Sometimes it is difficult to find the answer you are searching for because you do not know the specific keywords or the jargon that goes along with the topic. In this case, it was both. I do have a degree in electronics engineering R&D and software engineering. But never messed with sealed lead acid batteries!

Thanks again! Ken

 

[mikefitz]

Points to add.
It's possible your batteries in series parallel are getting out of balance, consider mid point balance circuits, https://www.victronenergy.com/batteries/battery-balancer

The reading on the Victron shunt will possible become more accurete if optimum peramerers are set. When charging from solar the 'charged voltage' should be slightly lower than the absorbtion voltage, boost volts , say 28.4 for a boost volts of 28.8.
The 'tail current' to a lower value, try 2%.
Other perameters such as charge efficiency may also need modification. With experience you should be able to identify perameters that need adjustment.

Sealed lead acid batteries are perhaps not the best choice ( depending on quality) for a daily cycled application and may result in a shorter service life than expected.

With lead acid batteries a useful indication of full charge is when the charge current falls to less than 1 amp per 100 Ah of capacity or where there is no further fall in current , this being in the absorbtion stage .

It's possible, depending on the state of charge when daily charging begins, the the default absorbtion duration, boost duration, of 2 hours, is too short, and a longer duration is needed to fully charge.

Mike