SunSynk SUN-25K-SG01HP3-EU-BM2, Installer Manual

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Page | 46 Hybrid Inverter | Installer Manual
Since the batteries are 48V the figure on the left is x4:
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Fully Charged 50.54V (Discharge Mode)
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Fully Charged 58.50V (Charge Mode)
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75% Charged 49.60V (Discharge Mode)
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75% Charged 54.80V (Charge Mode)
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25% Charged 48.00V (Discharge Mode)
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25% Charged 50.80V (Charge Mode)
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Completely Discharged 47.50V
Setting the cut-off higher is better for the batteries.
The batteries recommended for use with the Sunsynk systems are AGM Lead Acid or Lithium
Battery Banks. (‘AGM’ means Absorbed Glass Matt construction that allows the electrolyte to
be suspended new the plate’s active material. In theory, this enhances both the discharge and
recharging efficiency. AGM batteries are very heavy as a result).
State of Charge
Bulk:
Bulk charge is the first stage of a battery’s charging process where the charger identi-
fies the battery and its needs and then applies a high voltage to do the bulk of the charging. It
involves about 80% of the recharge. The properly sized charger will give the battery as much
current as it will accept up to charger capacity (25% of battery capacity in Amp hours).
Absorption: To fully charge a battery a period of charging at a relatively high voltage is needed.
This period of the charging process is called absorption. This occurs when the charging of a
battery has reached reached 80% of its capacity. The remaining charge equals 20% approxi-
mately. It makes the charger to hold the voltage at the charger’s absorption voltage (between
14.1 VDC and 14.8 VDC, depending on charger set points) and decreasing the current until the
battery is fully charged.
Float:
The charging voltage is reduced to between 13.0 VDC and 13.8 VDC and held constant,
while the current is reduced to less than 1% of battery capacity. This mode can be used to
maintain a fully charged battery indefinitely.
Equalisation: This is essentially a controlled overcharge that occurs at the end of the Bulk
mode and the absorption phase and is called the ‘equalisation voltage’. However, this techni-
cally this phase has another function. Higher capacity wet (flooded) batteries sometimes benefit
from this procedure, particularly the physically tall batteries. The electrolyte in a wet battery can
stratify over time, if not cycled occasionally. In equalisation, the voltage is brought up above
typical peak charging voltage well into the gassing stage and maintained for a fixed (but limited)
period. This stirs up the chemistry in the entire battery, ‘equalising’ the strength of the electro-
lyte, and knocking off any loose sulphating that may be on the battery plates.