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--- drafts:mppt_faq [2016-12-02 11:26] – [I want to over dimension the PV array, how can I calculate the maximum?] mvader
+++ drafts:mppt_faq [2021-09-30 07:18] (current) – guystewart
@@ Line 1: / Line 1: @@
 ====== MPPT FAQ ======
-==== 75/15 and 100/15 cannot be controlled by a BMS, what now? ====
+==== Q1: I want to size or oversize my PV array, how can I do this? ====
-The reason is that the RX pin is already used to the battery life on/off selection with the jumper. So therefore it is unfortunately not possible to control these two models with the VE.Direct .. remote on/off cable [link]. The solutions is buy the next model in line: the MPPT 100/30.
+See the blogpost [[https://www.victronenergy.com/blog/2014/03/28/matching-victron-energy-solar-modules-to-the-new-mppt-charge-regulators/ | Matching solar modules to MPPT charge controllers]].
-==== Can the output of the MPPT be used as a power supply, thus without batteries? ====
+==== Q2: 75/10, 75/15 and 100/15 cannot be controlled by a BMS, what now? ====
+By default the RX pin is already used to control the battery life on/off selection with the jumper. Use VictronConnect to change the function of the RX pin to remote on/off to enable BMS control. See
+[[https://www.victronenergy.com/media/pg/Manual_SmartSolar_MPPT_100-30__100-50/en/configuration-and-settings.html#UUID-b6cabb55-8d14-4fc9-190f-c0856aab60d3]] for details.
+==== Q3: My MPPT is only showing voltage readings, not currents and also no Watts? ====
+Make sure to *not* connect PV minus to the battery. See the manual.
+==== Q4: Can the output of the MPPT be used as a power supply, thus without batteries? ====
 The answer is; it depends on the type of load.
@@ Line 13: / Line 21: @@
 Loads where under voltage does not apply, like light globes, can be operated without any problems.
-==== I want to over dimension the PV array, how can I calculate the maximum? ====
+==== Q5: What about grounding one of the PV array poles? ====
+The MPPT is non isolated, meaning that the minus of the PV input is at the same potential as the minus of the battery output.
+Grounding is always done at one point only, to avoid ground currents. For a battery system, grounding must be done at the battery.
-Over-dimensioning a PV array is installing more Watt peak than the maximum charge power of the chosen MPPT charge controller. A common reason to over dimension is winter time.
+==== Q6: The Solar Charger is not working ====
-How to determine how far you can over dimension the PV array?
+. Check that the PV voltage is high enough compared to the battery voltage. Either read it with a remote panel or VictronConnect.
-There are only two limits, when determining the maximum array size that can be connected to an MPPT:
+Or measure the voltage with a Volt meter. Make sure to measure the voltage on the terminals on the charger. Not elsewhere, to rule out any faulty wires or fuses. The panel voltage needs to be at least 5V above the battery voltage for the charger to start power conversion; [[https://www.victronenergy.com/support-and-downloads/manuals|see the manual for more information]].
-  - The Maximum PV open circuit voltage
+. For models with a Remote on/off switch (a green two pole connector, labelled Remote L H), check that the jumper is in. L and H need to be shorted for the unit to switch on. Only the large models have this connector, see datasheet for details.
-  - The Maximum PV short circuit current
-Both values are specified in the datasheets of all our MPPT Solar Chargers. The ratings of the array must not exceed these two maximum limits of the MPPT.
+. Check that the battery voltage is set properly in the settings (12/24/48).
-The maximum PV power listed in the datasheet is **not** the maximum installable PV power. Instead it is the maximum charge current.
+. Check for [[:mppt-error-codes|error codes]].
-**Long explanation:**
+If all above is fine, and still the unit does not operate, contact a dealer to have the unit tested.
-Note that you cannot multiply these values to determine the install-able maximum Wp. Instead, look on the datasheets of the solar panels, to see what their max PV short circuit current is.
+==== Q7: Can I use the MPPT Solar Charger as DC-DC charger? ====
-And same for the Maximum PV open circuit voltage, and then do not forget to take the coldest expected temperature into account. Because the colder it is, the higher the max voltage.
+For example to charge a 12 Volt battery from a 24V battery bank?
-As an example, the maximum charge current of a 75/10 is 10 Ampere. When connected to a 24 Volt battery, it charges at 28.8 Volt. So the max charge power is 288 Watt. When installing a 300 Watt panel, it will reach its maximum charge current and power in summer. But not in winter.
+No.
-To get less difference between summer and winter, you can install two panels, i.e. 600 Watt peak of PV. In summer the charge controller will limit its charge power to 288 Watt. But in winter it can now also do more. Same for the curve during a (summer or winter-) day: it will earlier on the day reach its max charge current. Note that the exact differences between winter and summer obviously depend on the geographic location of the installation.
+==== Q8: Can I connect different panels to the same charge controller? ====
+No. Under no circumstances.
-===== DISQUS Comments =====
+==== Q9: Can I use panels with optimisers? ====
+No.
+===== DISQUS =====
 ~~DISQUS~~