Hi gang!
This is my first time posting.
I've been designing solar electric systems since 1978, so this isn't my first time around the block. I did somewhat retire in this field about 18 years ago.
After 22 years, I decided to upgrade my old 48 V system using one of the new Midnight Classic 150.
I took out my old Solar MSX-64 modules and replaced them with 4kWp of new (actually these are from a decommissioned plant) 250 W 60 cell modules.
The old Heliotrope General CC120 charge controller has been retired. It was (is) a PWM constant voltage controller. A real brute of a controller. It's wiring lugs will accept 4/0 cables!
There are 4 panels in series at 120V dc. Panels are rated at a hair over 8 A.
Now for the question of the day.
I purchased 16 brand new US battery L16HC. I want to set the classic 150 so don't roach the new batteries. At almost $5k, they're expensive to screw up.
so I looked a the US Battery spec/guide lines and you know, I'm a more than a bit confused. With the old Heliotrope, you set it for the voltage you wanted and that was it.
here are the specs from US battery:
For bulk charge the voltage should be 2.40 V per cell or 57.6V for my nominal 48 V system. That SEEMS a bit low to me.
However, the finish voltage is specified at 2.55 V per cell or 61.2 V. That's too high.
Then, for equalization, they specify the same 2.55 V
here's the US battery charge instructions link:
https://usbattery.com/wp-content/uploads/2014/05/usb-charging-recommendations.pdf
so anyone using these batteries?
Any input will be more than important to me.
thanks... Mike aka qrper
Morning QRP er,
Just to get this discussion going:
First, running strings of four 60-Cell PVs creates an EXCESSIVE input voltage for a Classic 150.
For 60 cell PVs, strings of three PVs is ideal.
Use the MidNite Classic String Sizer, to confirm:
http://midnitesolar.com/sizingTool/index.php
More later, Vic
Hi Mike,
The US Battery Charging recommendations are for Grid charging (as are those from most other battery manufacturers).
Using Solar chargers, it is difficult to do a Constant Current Bulk charge, in any reasonable length of time.
Perhaps, USB has recommendations for Solar charging, please contact them to see.
Lightly-cycled batteries, probably could regain a full charge at the 2.40-ish volt setting for Absorb. But, often for our off-grid, solar charged systems, the Solar Day is just too short for reliable recharge at this low-ish Absorb voltage (Vabs), particularly for more heavily cycled battery banks.
Also, most solar chargers will not do the Finishing charge, at the 2.55 V/cell.
So, just use your good Hydrometer, to see how well this Absorb voltage, at a reasonable charge time (or EA setting), does for your situation.
As you know, often we must increase the Vabs, somewhat in Winter to get the recharge done, in the typical amount of solar input.
FWIW, 73 GL, Vic