AGM battery charging and discharging conditions

[Jarda]

Hi, I like to ask few questions about charging AGM battery(120Ah Deka) because I noticed couple of problems using different charge regulators.

1. whats the maximum voltage in charging cycle? (some regulators vary in max voltage 14.1V - 14.7 and saying that are suitable for AGm batt.)
2. whats the "secure" minimum voltage? ( some regulators disconnect load when reached 11.5 but some goes as low as 11.1 in standard setting, also AGM friendly)
3. its ok to run AGM on regulator where flooded type of battery is hard set?

I have problems to properly load 130Ah eka AGM battery on 1x 175W panel(industrial one open voltage 28V) and various types of regulators(IVT 20A MPPT, IVT 20A 18124, Steca Solarix delta 20A)

The syptoms are that after charging looks like that battery is charged only to the half. (battery checked recently on different set of regulator and panels and is ok and I can notice big diference in performance of the battery after charging.

any suggestions?

[PNjunction]

This should help get you started, but basically with a lead-calcium East Penn agm, you want 14.1 to 14.4 volts temperature compensated. See the "Renewable Energy Charging Parameters" which is 1913.pdf file link at the bottom.

http://www.dekabatteries.com/?pageid=443

This guide is quite good at showing voltages, time limits, temperature compensation, and so forth. Note that what East-Penn considers an "equalization" is just an elevated absorb voltage, ie 14.4 to 14.6, and NOT anything over 15 volts. You have been warned.

Note that for longest life, they recommend getting as close to .3C current, but with voltage regulated and temperature compensated. In your case, that maximum would be about 36A.

With limited solar-insolation hours, my bet is that you are not getting enough absorb time in. Also, how are you determining that they are charged only to half? With an agm, unfortunately the only tool you can use to ballpark it is with a quality voltmeter, typically 12.2v with at least a 4 hour rest indicates 50% SOC.

[Sunking]

14.4 is the highest and where you want to be with solar. Don't sweat the details. If it is a DEKA AGM set Bulk = Absord = 14.4 volts, Float = 13.6 and call it done.

Info Here AGM

[Jarda]

This should help get you started, but basically with a lead-calcium East Penn agm, you want 14.1 to 14.4 volts temperature compensated. See the "Renewable Energy Charging Parameters" which is 1913.pdf file link at the bottom.

http://www.dekabatteries.com/?pageid=443

This guide is quite good at showing voltages, time limits, temperature compensation, and so forth. Note that what East-Penn considers an "equalization" is just an elevated absorb voltage, ie 14.4 to 14.6, and NOT anything over 15 volts. You have been warned.

Note that for longest life, they recommend getting as close to .3C current, but with voltage regulated and temperature compensated. In your case, that maximum would be about 36A.

With limited solar-insolation hours, my bet is that you are not getting enough absorb time in. Also, how are you determining that they are charged only to half? With an agm, unfortunately the only tool you can use to ballpark it is with a quality voltmeter, typically 12.2v with at least a 4 hour rest indicates 50% SOC.

thank you for your reply
Why I think that is charget to the half? its just my impression, after charging (evening) I turn on computer and battery shows around 12.2-12.3. when I used different set of reg+panels battery went smoothly down 12.6, 12.5 ....
I am in southern Spain and we have quite a lot of sun here.
So regulator even if not set to AGM( its not programmable) type of battery is ok if max. voltage 14.4-14.6?

[Sunking]

So regulator even if not set to AGM( its not programmable) type of battery is ok if max. voltage 14.4-14.6?

Maximum is 14.4 volts. You are in a warm climate and you do not want to exceed 14.4. Batteries have reverse temperature coefficient. The higher the voltage, the lower the voltage. The minimum for DEKA AGM is 14.2 and max 14.4. With Solar you want to run max because in reality unless the system is lightly loaded, you will never reach saturation charge which is exactly what you are describing with the voltage always being low. Run it at max and call it done. Use the generator and/or AC charger top off.

[daz]

Batteries have reverse temperature coefficient. The higher the voltage, the lower the voltage.

Hi Dereck...I'm not sure if it is a typo or not, but do you mean "the higher the temperature, the lower the voltage" instead? Or did I read post incorrectly?!

[Sunking]

Hi Dereck...I'm not sure if it is a typo or not, but do you mean "the higher the temperature, the lower the voltage" instead? Or did I read post incorrectly?!

Yeah my bad, good catch. Higher Temp > Lower Voltage

[PNjunction]

So regulator even if not set to AGM( its not programmable) type of battery is ok if max. voltage 14.4-14.6?

Always go by the voltage, and not necessarily the label on the silkscreen. For example, Morningstar Sunsaver pwm controllers come with a jumper attached for "sealed". The voltage here is in fact about 14.1 - 14.2 volts, more applicable to gel than agm. By removing the jumper for the "flooded" setting, the absorb voltage is 14.5 or so, which is better for agm.

Many manufacturers make assumptions in their labeling, and have no idea if you are using a gel, a lead-calcium agm, or a pure-lead agm, so it is best to check the manual (and measuring it is even better) and use the proper voltage for your battery - it may not always agree with the labeling.

[Jarda]

Thank everybody for replies

to add more details
my battery http://www.soligent.net/uploads/products/23975_6.pdf (strangely my battery has same product number but not have this solar label on it)
max cycle 14.4 - 14.58V
saying that max float 13.5 - 13.8 V

my regulator http://www.ivt-hirschau.de/product_i...roducts_id=150 (note the written "AGM Version with higher cut-off voltage
available upon request.")
Final charging voltage, main charging phase 14.1
Charge maintenance 13.7V
Load disconnection 10.5V
in manual is written that the charger supports all types of batteries AGM included(but manufacturer says that they have different different model for AGM batteries

my questions:
1. is this regulator suitable for AGM (in meaning of max gain from solar cells) or not ( and I will send it back claiming that there is typo in manual)?
2. is the Load disconnection voltage ( set in regulator) 10.5V realistic for good battery life or better manually disconnect on 11.9V?
3. if the regulator has the option to select type of battery which one is more suitable for charging AGM battery: lead or Gel ?
thank again for your replies

[Jarda]

This should help get you started, but basically with a lead-calcium East Penn agm, you want 14.1 to 14.4 volts temperature compensated. See the "Renewable Energy Charging Parameters" which is 1913.pdf file link at the bottom.

http://www.dekabatteries.com/?pageid=443

This guide is quite good at showing voltages, time limits, temperature compensation, and so forth. Note that what East-Penn considers an "equalization" is just an elevated absorb voltage, ie 14.4 to 14.6, and NOT anything over 15 volts. You have been warned.

Note that for longest life, they recommend getting as close to .3C current, but with voltage regulated and temperature compensated. In your case, that maximum would be about 36A.

With limited solar-insolation hours, my bet is that you are not getting enough absorb time in. Also, how are you determining that they are charged only to half? With an agm, unfortunately the only tool you can use to ballpark it is with a quality voltmeter, typically 12.2v with at least a 4 hour rest indicates 50% SOC.

why I think its charging only to half? it just go quickly after charging process to 12.3V on other regulator and other panels I have more smooth dropping of voltage

[PNjunction]

That cheap IVT controller looks to be on the very low acceptable end for a Deka at about 14.1v for absorb. This is a generic work-around for both gel and agm. In a solar cyclic application, I'd boost that up to the higher end that Deka recommends at about 14.4v. I'll bet your Steca is set for 14.4v.

I'm not exactly fond of the IVT's 13.7v float with the Deka's, but you are probably not spending much time there in solar anyway.

Here's the quickie determination:

Use your load/application. When done, leave the batteries alone for 4 hours minimum - no charge, no discharge. Disconnect any vampire loads like idling inverters. Measure the voltage with a quality voltmeter.

Generic AGM voltages - see your manufacturer's spec for the real numbers.
12.50 v = 75% SOC
12.20 v = 50% SOC
12.10 v = 25% SOC

Best bet is to keep an eye on the voltages during discharge - although when you draw larger currents, the voltages drop faster. Manufacturers may include a handy chart to ballpark the SOC during discharge.

[Jarda]

That cheap IVT controller looks to be on the very low acceptable end for a Deka at about 14.1v for absorb. This is a generic work-around for both gel and agm. In a solar cyclic application, I'd boost that up to the higher end that Deka recommends at about 14.4v. I'll bet your Steca is set for 14.4v.

I'm not exactly fond of the IVT's 13.7v float with the Deka's, but you are probably not spending much time there in solar anyway.

Here's the quickie determination:

Use your load/application. When done, leave the batteries alone for 4 hours minimum - no charge, no discharge. Disconnect any vampire loads like idling inverters. Measure the voltage with a quality voltmeter.

Generic AGM voltages - see your manufacturer's spec for the real numbers.
12.50 v = 75% SOC
12.20 v = 50% SOC
12.10 v = 25% SOC

Best bet is to keep an eye on the voltages during discharge - although when you draw larger currents, the voltages drop faster. Manufacturers may include a handy chart to ballpark the SOC during discharge.

thank you all for your explanations ant time. May God shine on your panels.