Help with new system

System

Hi. Please help me with my system to tweak it so it will be better balanced. Where should I make changes? Thanks.

I currently have a RE system with the following: 12 8A8D Deka Batteries configured @ 48V, Outback VFX 3648 with remote temp sensor, Mate, Hub 10, #1 MX60 connected to 4 Sharp 123w Panels, #2 MX60 connected to 8 Evergreen (EV102) 110w panels. (FN-DC soon to be connected when Mate is swapped out to newer version)

Charging set up as follows for the inverter - Absorb 57.6v @3hrs, Float 54.4v @3hrs, refloat 50v, Low Battery cut out @ 47.2v, Low battery cut in @50v .

I am currently using HBX mode with the inverter settings are - Drop Grid @55.6v After 1.5 hr, Use grid @49.2v after 1 hr.

MX60 Settings Absorb 57.6v for 3 hrs float 54.4 end amps 0

- What do you think of the current settings for inverter and charge controllers?
- Do I need to change any of the settings?

- My current Hydro use for solar is 5-8 KWH/day
- I live near London, Ontario, Canada
- Is the battery bank big enough?
- the winter time coldest temp around -20C
- I use the grid for inverter pass through (HBX) and extra charging (when the sun goes into hiding)

- How many Sharp 123w solar panels do I need to add to this system?
- I am considering to change to a 60v = 5 panels in series
- Can the total panels for one MX60 be 25? (Sharp solar Panel ratings 21.3voc and 8.1a isc 123w)

- Battery 8A8D Deka 244ah @ 20hr rate and 257ah @ 100ah rate (Deka) Charging rates Absorb = 55.2v - 56.4v , Float 54v - 55.2v
- Do I use the 20ah rate to size the battery bank eg 244ahX3 strings = 733ah is this correct?
- These batteries are fairly new as the system has only been running for around 4 weeks
- Should I be adding to batteries?

crewzer

Re: Help with new system

John,

Thanks for providing so much technical information about your system. Unfortunately, I don’t understand this statement: “My current Hydro use for solar is 5-8 KWH/day”

-How many Sharp 123w solar panels do I need to add to this system?
- I am considering to change to a 60v = 5 panels in series
- Can the total panels for one MX60 be 25? (Sharp solar Panel ratings 21.3voc and 8.1a isc 123w)

Configured for a 48 V battery system, your MX60 can handle up to 25 Sharp 123 W modules wired as a 5 X 5 array. In fact, such an array (3,075 W STC, 60 V nominal, etc., etc.) is probably just about “perfect” for the MX60. The Voc won’t be too high in the winter, the Vmp won’t be too low in the summer, the Isc well within the controller spec limits, and the array size is within the "official" OutBAck spec. :cool:

#1 MX60 connected to 4 Sharp 123w Panels, #2 MX60 connected to 8 Evergreen (EV102) 110w panels.

This present arrangement (48 V nominal array voltage) may give you some problems:

1) The summer array voltage from the Evergreen array (68 Vmp STC, <60 V operating Vmp in the summer) may not be high enough to push the “48 V” battery bank to its target absorption voltage.
2) The MX60 does not operate in its semi-active MPPT mode when the bulk (MPPT) stage output current is <5A. You’ll likely see this condition fairly often from a Sharp array (~492 W STC) charging a 48 V battery bank. Instead, it’ll operate in its “U-Pick” fixed % mode.

- Do I use the 20ah rate to size the battery bank eg 244ahX3 strings = 733ah is this correct?
- These batteries are fairly new as the system has only been running for around 4 weeks
- Should I be adding to batteries?

A useful “rule-of-thumb” for 48 V systems is for the array STC power spec to be ~4X the bank’s AH capacity. For your 244 Ah x 3 = 732 Ah battery bank, an appropriate sized array would be ~3,000 W STC, or, conveniently, 25 Sharp 123 W modules configured 5 x 5. :cool:

The actual battery bank size requirement depends on you average daily energy requirement. With grid back up, a bank that’s sized for ~5X your daily energy load should be about right (~20% discharge per day). Don’t forget to include inverter losses in your energy calculation.

Charging set up as follows for the inverter - Absorb 57.6v @3hrs, Float 54.4v @3hrs, refloat 50v, Low Battery cut out @ 47.2v, Low battery cut in @50v .

I am currently using HBX mode with the inverter settings are - Drop Grid @55.6v After 1.5 hr, Use grid @49.2v after 1 hr.

MX60 Settings Absorb 57.6v for 3 hrs float 54.4 end amps 0

- What do you think of the current settings for inverter and charge controllers?
- Do I need to change any of the settings?

I’d suggest using East Penn’s recommendations for charger settings for their Deka and MK AGM batteries. For my 24 V system, I use 28.7 V for 2-1/2 hours for the absorb setting, and 26.7 V for float (both ref 77 F / 25 C battery temp).

See: http://www.mkbattery.com/techref.php

The OutBack’s HBX mode can be useful. An alternative is to consider using the “Grid Use” mode, and having the grid top off the batteries on a nightly schedule. This is especially effective if you have “time-of-use” cheap-energy available.

HTH,
Jim / crewzer

BB.

Re: Help with new system

I think "Hydro" is slang "up there" for Hydro-Québec -- or his electrical utility company.

-Bill

System2

Re: Help with new system

crewzer wrote: »

John,

Jim Thanks for the great info

“My current Hydro use for solar is 5-8 KWH/day”

With Hydro i was referring to the Solar produced energy from PV 5-8KWH/Day, separate from the Grid we use here.








The actual battery bank size requirement depends on you average daily energy requirement. With grid back up, a bank that’s sized for ~5X your daily energy load should be about right (~20% discharge per day). Don’t forget to include inverter losses in your energy calculation.

Daily energy requirement = at 5kwh X 1000 = 5000w / 48v = 104.16 ah +10% inverter losses 10.42ah = 114.58ah X 5 = 572.9ah
Have i calculated this correctly?

then am i correct to assume that at a 5kwh usage per day a 732ah battery bank is ok?

crewzer

Re: Help with new system

Based on the info provided, the battery bank size looks good to me.

Regards,
Jim / crewzer

System2

Re: Help with new system

I’d suggest using East Penn’s recommendations for charger settings for their Deka and MK AGM batteries. For my 24 V system, I use 28.7 V for 2-1/2 hours for the absorb setting, and 26.7 V for float (both ref 77 F / 25 C battery temp).

See: [ http://www.mkbattery.com/techref.php ]http://www.mkbattery.com/techref.php

My Curent MX settings are below i have read the East Penn's Recomendations for settings But am still confused as to where to set how long Absorb time should be and the end amps to prevent overcharging and under charging the batteries.

MX60 Settings Absorb 57v for 3 hrs float 53.4 end amps 0


I currently have a RE system with the following: 12 8A8D Deka Batteries configured @ 48V, Outback VFX 3648 with remote temp sensor, Mate, Hub 10, #1 MX60 connected to 4 Sharp 123w Panels, #2 MX60 connected to 8 Evergreen (EV102) 110w panels.

crewzer

Re: Help with new system

John,

I'm going to prepare a detailed assessment for you, and I'll also provide some recommendations for you to consider. I need a bit more information, so I have a couple of questions for you:

1) Why are you using two MX60 charge controllers?
2) Are you planning to expand your system (i.e., larger array)?
3) How are your PV modules mounted? (on a roof, on a rack?)
4) Can you provide the exact model number and/or electrical specs (Voc, Vmp, Isc, Imp) for your Evergreen 102 modules?

More later...
Jim / crewzer

System2

Re: Help with new system

crewzer wrote: »

John,

I'm going to prepare a detailed assessment for you, and I'll also provide some recommendations for you to consider. I need a bit more information, so I have a couple of questions for you:

1) Why are you using two MX60 charge controllers?

The first setup was 12v when i upgraded to the 48v i had the two controllers so i ran a test the Evergreen Panels on the one MX60 and the Sharp panels on the other MX60 power production from the Sharp panels on average was more. i have since combined all the panels on one MX60

2) Are you planning to expand your system (i.e., larger array)?

Yes 3 panels one for each string to make a total of 5/ string, then another 10 panels over time.

3) How are your PV modules mounted? (on a roof, on a rack?)

Mounted on a roof on a rack tilted to a fixed 45 Degree south.

4) Can you provide the exact model number and/or electrical specs (Voc, Vmp, Isc, Imp) for your Evergreen 102 modules?

EV102
PP(W) 110
VP(A) 17.0
IP(A) 6.47
VOC(V) 21.3
ISC(A) 7.48

crewzer

Re: Help with new system

John,

Thanks for the additional info.

My take on the MK instructions for East Penn 8A AGM batteries is that the absorption voltage target should be between 57.0 V and 57.7 V, ref 77 F / 25 C. 57.4 V is probably a good mid-point (FWIW, I use 28.7 V for my 24 V battery bank). 53.4 V looks good for the float setting.

I use 2.5 hours for the absorption timer. I’ve had very good results with this setting. I don’t find the “End Amp” feature to be useful, so I leave it set at “zero”.

You may need to check the MX60’s calibration. I recommend that the battery bank voltage be measured at the battery terminals near the need of the absorption stage, and then the MX60 calibration adjusted accordingly. See “Vbatt Calibration” in the ADVANCED menu.

I’ve recently started experimenting with a very mild equalization charge every couple of months. For one absorption cycle, I increase the absorption voltage from 28.7 V for 2.5 hours to 28.9 V for 4 hours. We’ll see if it makes a difference.

I’m concerned about your system’s present “48 V / 48 V” configuration. Once the summer temperatures set in, the array voltage will likely drop by ~15% below the STC Vmp spec. Assuming a 68 Vmp (STC) spec for the array, mid-day summer array voltage may well drop to ~58 V. Allowing for additional voltage drop in the wiring from the array to the controller, plus the controller’s requirement that its input voltage be ~2 V above the battery voltage, the combination of a “low” array voltage and a “high” battery voltage may cause the controller to enter its “snooze” mode in mid-day and stop charging for a while.

I’d look to increase the array voltage to “60 V” nominal as soon as you can. This will solve the array's low-voltage problem in the summer.

HTH,
Jim / crewzer