Recomended MPPT input voltage for a 48 volt system

Typical recommended MPPT nominal voltage input for a given system is double the battery bank voltage. I am contemplating switching my system over to 48 volts from 24 volts. I have 72 cell panels series wired 3s x 3p, Midnite classic 200. I am curious as to how the approx. 130 voc. , 105 vmp. will work into a 48 volt bank, this being 1 1/2 times the nominal voltage, not double. At the present time this 3s x 3p configuration is charging my 24 volt bank and being 3 times nominal it creates more heat than I am comfortable with, especially in the warm Baja climate.
2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.
Comments
With 72 cell panels in a 48 volt system, if you put them 2 in series the voltage is barely high enough in hot weather and you may have to put the Classic in 'legacy' mode. Three in series is perfect for a 48 volt system and is a good reason to have a classic 200 rather than a classic 150.
--vtMaps
2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.
I still have that 4024 and 4548 in the shed? Are you in Mexico now? I am asking for a friend.
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2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.
Agree with vtmaps ...
With 72 Cell PVs, on a 48 volt system, you really have little choice. Strings of three PVs on a 48 V system is sufficiently high to allow EQing almost any Flooded battery with hot PVs and a relatively cool battery.
MidNite Solar has added a Footnote to their String Sizer Results, regarding minimum Input voltage for MPPT CCs, like the Classic:
"With MPPT controllers the higher the input voltage the less efficient they are. This is not a large value but it will add up to a little more heat in the controller and a point or two less in efficiency. BUT you also have to be careful not to have the input voltage to low. Most all MPPT controllers will want to see a minimum of 130% of the actual high battery voltage. So if we have a 48v battery and it has an Equalize voltage if 62.3 volts than we would multiply that by 130% and we would need a minimum of 81 volts on the input on the hottest day of the year in order to have enough headroom for the MPPT to work".
So with 72 Cell PVs, and a 48 V Flooded battery, strings of three PVs is the minimum, and with 60 Cell PVs strings of three is even better, as it easily meets minimum Vin required at a lower Vin to the CC.
On the 48 V systems here, one runs strings of three 72 cell PVs (106 STC Vmp strings), and another runs strings of three 60 cell PVs (92 STC Vmp strings), on Classic CCs. Both systems could run lower Vin to the CCs, but we need to run what the available PVs.
Vic
Looks like you have more SW's than you need. Getting any tuna off Catalina?
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Can you really have too many SW's
They are pulling in nice Bluefin daily on the backside if the Island
2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.
No Prob on the Baja express. I think Downwind Marine got it done on the HF a few hours ago.
http://members.sti.net/offgridsolar/
E-mail [email protected]