Charge Controller End Amps Setting?

verdigo · April 2015

I have been using end amps as a way to terminate the charge controller's absorb stage, and have been using 1% of the amp hour rating. Just wondering if perhaps that is running the absorb stage a bit long.

For those of you that use end amps, what settings do you use?

BB. · April 2015

How much do you discharge the battery bank during a typical day (over night).

If to 75% SoC (or less discharging), and you get to float every day--That may be excessive charging (summer vs winter may be different answer--less sun in winter).

How is battery water usage? Do you have to add water every ~2 months? If cells are "low after a few weeks or a month".

Have you been monitoring your specific gravity?

If shallow discharging, does not the current Midnite Classic software have the ability to do delayed absorb stage by a day or so for shallow discharging?

-Bill

Vic · April 2015

Dennis (hope that that is your name),

For the Flooded battery banks here, 0.9-ish % of nominal 20 hour Capacity, with relatively low Vabs of about 58 volts is perfect (with 1.265 SG electrolyte). The right range of EA setting will depend upon the Vabs. This setting seems to work fine, at least for DODs down to about 75% SOC.

As BB Bill noted the later versions of the Classic Firmware (which you are probably using), allow a certain number of days to be skipped, which is also in use here.

FWIW, Good Luck, Vic

SandyP · April 2015

verdigo wrote: »

I have been using end amps as a way to terminate the charge controller's absorb stage, and have been using 1% of the amp hour rating. Just wondering if perhaps that is running the absorb stage a bit long.

For those of you that use end amps, what settings do you use?

I also use the 1% end amps value for when we are away however, when using the system it become difficult to separate the charge amps from that being used and as a result the absorb stage can extend up to the max allowed by the controller (I have that currently set at 2 hours).
As I only have one shunt this is the best my system can do.

BB. · April 2015

2 hours of Absorb many a bit short of time -- Especially if you are cycling the battery bank more deeply (by 25 to 50%)... Then 4-6 hours of absorb as your limit may be more appropriate (if your absorb is being terminated by time instead of 1% rate of charge).

-Bill

SandyP · April 2015

BB. wrote: »

2 hours of Absorb many a bit short of time -- Especially if you are cycling the battery bank more deeply (by 25 to 50%)... Then 4-6 hours of absorb as your limit may be more appropriate (if your absorb is being terminated by time instead of 1% rate of charge).

-Bill

Thanks Bill,
I will look into this however, currently our daily use is quite small hence the max DoD each day is ~10 to 15% and this drops to ~7% when we are away.
Strangely, even with the 2 hour absorb max time I see the FM60 shows days where absorb has gone to 3, 2.4, 3.2 & 3.3 hrs.

Here is a graph of some days in January this year showing the battery charging when were were at the cabin:
Attachment not found.

verdigo · April 2015

BB. wrote: »

How much do you discharge the battery bank during a typical day (over night).

If to 75% SoC (or less discharging), and you get to float every day--That may be excessive charging (summer vs winter may be different answer--less sun in winter).

How is battery water usage? Do you have to add water every ~2 months? If cells are "low after a few weeks or a month".

Have you been monitoring your specific gravity?

If shallow discharging, does not the current Midnite Classic software have the ability to do delayed absorb stage by a day or so for shallow discharging?

-Bill

I am actually a grid interactive guy so most of the time I let the inverter handle battery charging. I had the absorb timer on the inverter set at one hour and float for four hours. About the time the sun comes up the inverter is set to sell at two volts below the float voltage.

Recently I have reduced the inverter absorb time to .5 hours because I was thinking that a one hour per day absorb was two much, and water usage indicated as much. While the sun is up the inverter sells everything above the inverter's sell setting and the charge controller stays in perpetual bulk.

Yesterday I shut the inverter's grid power down and allowed the charge controller to complete a charge cycle. With end amps set at 5 amps absorb lasted approx 3.5 hours. I am using Interstates's specified charge voltages which are pretty high as compared to most GC2 batteries. (61.2 Absorb) (53.6 Float)

My specific gravity readings are 1.265 - 1.275 on some cells. I believe some of the varience is due to some of the batteries/cells having too much water. Correcting water levels is a pretty long process. I have recently discovered that by giving the batteries a pretty good thump to shake bubbles loose from the plates before checking water levels can make a pretty significant difference in water levels and I assume specific gravity.

verdigo · April 2015

Vic wrote: »

Dennis (hope that that is your name),

For the Flooded battery banks here, 0.9-ish % of nominal 20 hour Capacity, with relatively low Vabs of about 58 volts is perfect (with 1.265 SG electrolyte). The right range of EA setting will depend upon the Vabs. This setting seems to work fine, at least for DODs down to about 75% SOC.

As BB Bill noted the later versions of the Classic Firmware (which you are probably using), allow a certain number of days to be skipped, which is also in use here.

FWIW, Good Luck, Vic

Yep Dennis. I remember reading that Interstate uses a 1.280 initial electrolyte charge but I have never been able to get my cells that high even after an EQ. When I first got my batteries I was using much lower voltages than what Interstate recommended. Using their recommendations I have been able to maintain 1.265-1.270. (61.2 Vabs)

I am grid interactive so I don't get to 75% soc unless I discharge to even up the SGs on purpose.

Thanks
Dennnis

Surfpath · April 2015

verdigo wrote: »

For those of you that use end amps, what settings do you use?

I use a 1% end amp setting and an absorb of ~4.30 hours to 5 hours (depending on the time of year).

I discharge daily from 95/100% to 60-75% (~25% - 40% DOD: Average 30%).

I top up the cells every 6 weeks with 1.25 liters of water across eight L-16 batteries (24 cells).

I realize that this might be on the high side when it comes to absorb charge, I am slightly underpanneled (8.5%) and this is one way to ensure almost 100% SOC every day.
-SP

inetdog · April 2015

verdigo wrote: »

My specific gravity readings are 1.265 - 1.275 on some cells. I believe some of the varience is due to some of the batteries/cells having too much water. Correcting water levels is a pretty long process. I have recently discovered that by giving the batteries a pretty good thump to shake bubbles loose from the plates before checking water levels can make a pretty significant difference in water levels and I assume specific gravity.

Air bubbles will make a difference in the specific gravity calculated by weighing the electrolyte in the battery and looking at the volume (not a practical technique!!) but it should not affect the reading of a hydrometer as long as the electrolyte is well mixed and there are no bubbles in the hydrometer.
If that many bubbles are forming it is a good bet that the electrolyte is in fact well mixed, even though some bubbles are trapped on the plates.
So your hydrometer reading should be just fine once you get the electrolyte level correct.
The increased volume caused by bubbles is a good reason not to ever fill the battery above the manufacturer's recommended fill line. Otherwise you may force liquid electrolyte out the vent through heavy bubbling.

Alaska Man · April 2015

I use 1 Amp (1% would be 17Amps) and 3.5 hours Absorb, I usually time out, but on good sunny days I'm at 100% -101% on the Tri-Metric when I do. Like others I make sure to Float at least once a week. With AGM's I don't deal with adding water.

Charge Controller End Amps Setting?

Comments

Categories