I have tried different MPPT solar chargers, and they all seem to have the same defect in relation to Lithium-ion batteries. The algorithms seem to wait until the battery reaches its low voltage charge point, typically 13.2 Volts before the solar panels kick in. When the sun is directly overhead and solar panels have a 15 Amp capacity, the solar chargers do not supply the boat load, the load is supplied from the Lithium-ion batteries until such time as the low voltage charge point is reached. Does Victron have a MPPT charger that senses the available solar power and uses this to supply the load, rather than discharging the Lithium-ion batteries. By the time the batteries reach the low voltage charge point the sun is way over near the horizon, and the midday power available from the solar panels is not being utilized.
If you have set the float voltage at 13.2v this will happen.
Perhaps a screenshot of your mppt settings?
Victron MPPT chargers have a setting called rebulk voltage offset as explained below which can avoid this problem. The default float voltage is 13.5V and can be configured so once charged, this holds the battery at around 99% full and supplies loads.
Copied from the manual.
Re-bulk voltage offset
This setting sets the re-bulk voltage offset. This offset voltage is used to determine when a charge stage stops and the bulk stage starts again, i.e. the charge cycle resets and starts at the first charge stage again.
The re-bulk voltage is calculated by subtracting the re-bulk voltage offset from the lowest voltage setting (normally this is the float stage).
An example: If the re-bulk offset is set at 0.1V and the float voltage at 13.5V, the charge cycle will restart once the battery voltage drops below 13.4V (13.5 minus 0.1) for one minute.
What voltage are your panels?
Victron MPPT only starts charging when the panels are at Vbatt + 5V.
Thank you all for your replies. Unfortunately, the issue has nothing to do with Re-bulk settings, Vbatt +5v or the setting of the float voltage. Let’s assume the battery has reached full charge at 14.4 volts. Between 14.4 volts and the low voltage recharge point (let’s assume 13.4 volts) the battery supplies the base load (let’s assume 5 amps) even if the sun is directly overhead. This is a waste of available solar power. I believe MPPT solar chargers need a current shunt input so as it senses that there is a base load, looks at the current battery voltage, and then maintains that battery voltage using the solar array, and adjusts the solar output so as to maintain a zero-shunt current ie The solar array is putting out enough current to compensate for the discharge current. Example…battery is at 13.7v, base load is 5 amps and sun is directly overhead. Adjust solar array such that it’s 13.7 volts and supplies 5 amps of charge current, resulting in no discharge of the battery. All MPPT chargers exhibit the same basic problem.