9.3. Batteries are undercharged
This chapter deals with possible reasons why the solar charger is not sufficiently charging the batteries and the steps you can
take to check or remedy the situation.
Some signs of undercharged batteries:
• The batteries take too long to charge.
• The batteries are not fully charged at the end of the day.
• The charge current from the solar charger is less than expected.
9.3.1. Too much DC load
The solar charger does not only charge the batteries, it also provides power for the system’s loads.
The battery will only be charged when the power available from the PV panels exceeds the power being drawn by the loads in the
system, like lights, fridge, inverter, and so on.
If the solar charger has a dedicated load output (10, 15 or 20A model), then it can easily be checked how much power the PV
array has generated and how much power is used by the loads. This is providing that all loads are connected to the load output
and are not connected directly to the battery.
If the solar does not have a load output, it might have a battery monitor installed.Then you can see how much current is going in
(or out) of the battery and the solar charger will tell you how much current the solar array is generating.
In both above cases, a positive sign alongside the current reading means that current is flowing in to the battery, while a negative
sign means that current is being drawn from the battery.
9.3.2. Battery charge voltages are too low
If the battery voltages have been set too low the batteries will not receive a full charge.
Check if the battery charge voltages (absorption and float) are set correctly. Consult the battery manufacturers information for the
correct charge voltages.
9.3.3. The battery is almost full
The solar charger will reduce its charge current when the battery is almost full.
If the state of charge of the battery is unknown, and the current is reducing while the sun is still shining, it can mistakenly be
interpreted as the solar charger being faulty.
Th first current reduction takes place at the end of the absorption stage, when the battery is approximately 80% charged.
The current will continue to reduce during the float stage, when the battery is approximately 80 and 100% charged.
The float stage starts when the batteries are 100% full. During the float stage the charge current is very low.
To find out what the state of charge (SoC) of the battery is, check the battery monitor (if present), or alternatively check the charge
stage the solar charger is in.
• Bulk: 0-80% SoC
• Absorption 80-100% SoC
• Float or storage: 100% SoC
9.3.4. Battery cable voltage drop
If there is a voltage drop over the battery cables, the solar charger will output the correct voltage, but the batteries will receive a
lower voltage. Battery charging will take longer, and this can potentially lead to undercharged batteries.
A VE.Smart network can help in case of a cable voltage drop. A
or battery monitor measures the battery
terminal voltage and sends this via the VE.Smart network to the solar charger. If the battery voltage is less than the solar charge
voltage, the solar charger will increase its charge voltage to compensate for the voltage losses. But be aware that in case there is
a large voltage drop, the battery cables and cable connection will need to be checked and if there are issue they will needs to be
rectified first.
A voltage difference has the effect that the battery will be charged with voltages that are too low to. It will take longer to charge the
batteries because the charge voltage is too low and there is a loss of charge power. The lost power is caused by heat dissipated
over the battery cables.
The voltage drop is caused by the following:
• Battery cables with insufficient cross-sectional area
• Badly crimped cable lugs or terminals
MPPT solar charger manual
Page 47
Troubleshooting and Support
