Epever Tracer / MT50 Charge Controller Settings for AGM battery?

[rhythmstick]

Hiya everyone,

I'm relatively new to solar. This is my system (on a boat with no other means of charging):

• Epever Tracer 4210AN (with an MT50)
• 3 x 200w panels
• 1 x 260 Ah AGM battery (specs here)

Am trying to set up the MT50 with the best settings for my battery.

I've read this thread, which is what prompted me to sign up. I've also done other looking around and got in touch with the suppliers of the battery, but I'm not confident that my settings are right, so I'm hoping someone on here will be able to advise me if any of these values need tweaking.

So, these are my current settings:

Batt. Type:
User

Batt. AH:
260AH

Temp Comp. Coeff / Temperature Compensation Coefficient:
-3mv/degC/2V
...should this be -3mV (ie, the float charging voltage temp. coefficient) or should it be -4mv (ie, the cycle use voltage temp. coefficient) ?

Rated Voltage:
Auto

Over Volt. Disc. / Over Voltage Disconnect Voltage:
15.1 V
...was advised to keep this down, as close to 15.0v as I could.

Charge Limit:
15.0 V

Over Volt. Rec. / Over Voltage Reconnect Voltage:
15.0 V

Equal. Charge / Equalize Charging Voltage:
14.8 V

Boost Charge:
14.8 V
...this is the upper limit of the battery spec's 14.6v to 14.8v range.

Float Charge:
13.8 V
...this is the upper limit of the battery spec's 13.6v to 13.8v range.

Boost Rec. / Boost Reconnect Charging Voltage:
13.2 V

Low Volt. Rect. / Low Voltage Reconnect Voltage:
12.6 V

Under Volt. Rect / Under Voltage Warning Reconnect Voltage:
12.2 V

Under Volt. Warn / Under Voltage Warning Voltage:
12.1 V

Low Voltage. Disc. / Low Voltage Disconnect Voltage:
12.1 V

Discharge Limit:
12.1 V
...apparently, for AGM batteries, 12.1v corresponds to a discharge level of 50%.

Equalize Time:
0min

Boost Time:
120min

Can anyone confirm if these settings are correct? Or are there any tweaks I can make?

Big thank you in advance!

Cheers,
James

 

[sunshine_eggo]

Boost 14.6-14.8V (prefer 14.6V)
temp comp -4mV/°C/cell
Float 13.6-13.8V (prefer 13.8V)

Over Volt. Disc. / Over Voltage Disconnect Voltage:
15.1 V
...was advised to keep this down, as close to 15.0v as I could.

Boost Rec. / Boost Reconnect Charging Voltage:
13.2 V

12.6V

Low Voltage. Disc. / Low Voltage Disconnect Voltage:
12.1 V

Discharge Limit:
12.1 V
...apparently, for AGM batteries, 12.1v corresponds to a discharge level of 50%.

Huge misconception. that's the RESTING voltage, i.e., you cut all current to and from the battery, let it sit for 24 unused for hours and then measure 12.1V - that's about 50%.



You can approximate voltage and state of charge based on the above curves. Example:

260Ah battery
0.1C = 26A
Following the 0.1C curve, the battery should last about 10 hours, thus at 5 hours you'll be at 50%.
At the 5 hour mark, it would read about 12.0V (2.00V * 6).

For a heavy load, you could be under 12.1V in just a few minutes.

Unaddressed settings are either correct or don't matter.

 

[mikefitz]

Low Volt. Rect. / Low Voltage Reconnect Voltage:
12.6 V

Under Volt. Rect / Under Voltage Warning Reconnect Voltage:
12.2 V

Under Volt. Warn / Under Voltage Warning Voltage:
12.1 V

Low Voltage. Disc. / Low Voltage Disconnect Voltage:
12.1 V

Discharge Limit:
12.1 V

There settings relate to the load output of the charger, thus have no effect on the charge and discharge of the battery unless the load output is used in the system.

Equalize Time:
0min

Boost Time:
120min

Equalise time may need to have a value other than zero to avoid Epever confusion, if issues try 10 mins.
Boost time may need increasing to allow full absorbtion.

Mike

 

[rhythmstick]

View attachment 175383

Boost 14.6-14.8V (prefer 14.6V)
temp comp -4mV/°C/cell
Float 13.6-13.8V (prefer 13.8V)





12.6V



Huge misconception. that's the RESTING voltage, i.e., you cut all current to and from the battery, let it sit for 24 unused for hours and then measure 12.1V - that's about 50%.

View attachment 175384

You can approximate voltage and state of charge based on the above curves. Example:

260Ah battery
0.1C = 26A
Following the 0.1C curve, the battery should last about 10 hours, thus at 5 hours you'll be at 50%.
At the 5 hour mark, it would read about 12.0V (2.00V * 6).

For a heavy load, you could be under 12.1V in just a few minutes.

Unaddressed settings are either correct or don't matter.

Thank you for your very helpful reply.

Did you intend to comment on my Over Voltage Disconnect Voltage setting or does my 15.1v for that look OK?

I understand your comments re the Low Voltage Disconnect Voltage and the Discharge Limit, but not sure what value(s) I should replace my 12.1v values with. Do you have any suggestions for that one?

 

[rhythmstick]

There settings relate to the load output of the charger, thus have no effect on the charge and discharge of the battery unless the load output is used in the system.



Equalise time may need to have a value other than zero to avoid Epever confusion, if issues try 10 mins.
Boost time may need increasing to allow full absorbtion.

Mike

Hiya Mike,

Yes, my load is attached to the output of the Epever Tracer rather than directly to the battery, if that's what you mean?

The MT50 seems to accept the zero Equalize Time fine, but how do I work out the best Boost Time?

 

[mikefitz]

The MT50 seems to accept the zero Equalize Time fine, but how do I work out the best Boost Time?

Can be difficult with solar as there may not be enough hours of daylight. The default is 2 hours. A rough calculation assuming a constant available charge current, suggested by some battery manufacturers, is,

T = 0.38 x C/ L

For your battery C at the 20h rate is 230 Ah, if the available charge current 40 amps, then T = 0.38 x 230 /40 = 2.2 hours.

However the available solar, and thus current, is variable, as the depth of discharge before the days charge cycle begins, so I would regard the 2 hours as a minium. The battery manufactures suggested voltages assume AC charging where the charger is active continuously, any under charge is compensated for by the long period of float voltage that 'tops up' the battery.

One suggested technique to determine end of charge is to monitor charge current and terminate at 1% C, approximately 2 amps for your battery. ( during the absorbtion period the battery accepts progressively lower and lower current).

Having a shunt based battery monitor, programmable for lead acid batteries, ( Victron Smart Shunt/ Victron BMV712), is useful for battery management.

I have some feedback from users of the AGM batteries , ( Explorer from Alpha Batteries, UK) in RV and marine applications, the batteries tend to give lower service life than you would expect, where solar is the primary method of charging. My guess is not enough sun hours or high enough current in the UK, where RV/ boat panels have much reduced output, especially in winter.

Mike

 

[rhythmstick]

Thanks, Mike. I've gone with 132 mins (2.2 hours) for the Boost Time.

So, if I've got everything right, my final values should be?...

Batt. Type:
User

Batt. AH:
260AH

Temp Comp. Coeff:
-4mv/degC/2V

Rated Voltage:
Auto

Over Volt. Disc.:
15.1 V

Charge Limit:
15.0 V

Over Volt. Rec.:
15.0 V

Equal. Charge:
14.8 V

Boost Charge:
14.6 V

Float Charge:
13.8 V

Boost Rec:
12.6 V

Low Volt. Rect.:
12.5 V

Under Volt. Rect:
12.2 V

Under Volt. Warn:
12.0 V

Low Voltage. Disc:
11.9 V

Discharge Limit:
10.6 V

Equalize Time:
0min

Boost Time:
132min

I'm going to get a mains AGM battery charger as well so I can give the battery a good top-up every month or so during the winter months with new petrol generator. Does anyone know if I'll need to disconnect my charge controller beforehand?