Ramsond SunRay 1500 and 3000 Inverters
Instruction Manual (v. 34411)
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Ramsond Corporation. All right reserved. Ramsond and Sunray are trademarks of Ramsond Corp.
Page 16.
Age and condition of the batteries (older batteries lose Ah
capacity).
Compliance with turning off unnecessary AC loads.
Use of DC appliances and compliance with turning off
unnecessary DC loads.
Derating the Battery Bank
Most lead-acid batteries have a rating expressed in amp-hours (Ah). The most common rating of
Ah is “at the 20 hour rate”.
NOTE:
There is no relationship between Cold Cranking Amps (CCA) and Ampere Hours (Ah).
For example: if a 20 Ah battery is discharged at a 1 amp rate, will take 20 hours to discharge
that battery. The terms “charged” and “discharged” relate to actual battery voltage. This means
that the output voltage of a nominal 12 volt battery starts at 13.2 volts (fully charged) then drops
to 10.5 volts (discharged-Inverter low voltage limit). If the load on the battery causes the battery
to discharge faster than the 20 hour rate, the capacity (Ah) of the battery is measurably reduced
(derated). Derating is a major run time factor.
Example: The user needs a one hour run time. The battery is 220Ah (20 hour rate), and the
load is 220 amps; that is 100% of the Ah (20 hour rate). But in fact, a higher battery capacity is
required to get the desired run time of one hour. In most cases you will need to multiply the
actually battery Ah by three 3. So, if you need to run 220 amp at 1 hour, you should have at the
minimum 660 Ah batteries.
The installer must carefully plan the capacity of battery bank or the run time may be seriously
affected. To the inexperienced installer, several trial battery capacities may be required to make
sure a large enough battery capacity is available to achieve the desired run time. It is always a
safe bet to oversize the battery bank as the battery capacity is likely to reduce with time.