Load Output Conventional algorithm 1 in BlueSolar MPPT 75 ¦ 15 Charge Controller

DIY
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1

Hi,

I’m aiming to test the worst case scenario of how much energy can be harvested in a shaded location in Northern Europe in winter. A BlueSolar MPPT 75 ¦ 15 Charge Controller is used with the VE.Direct Bluetooth device and the Victron android app. Battery charging is working perfectly as expected with MPPT correctly optimising the current and voltage drawn from the photovoltaic panel in low light levels to optimise efficiency. Battery charging seems to be working correctly as well with float, abs. and bulk charging being used automatically.

I set Load Output to “Conv. algorithm 1” to automatically drain the battery into a 12 V, 50 W light bulb as a test load without taking the battery charge level too low and this correctly displayed “off < 11.1V, on > 13.1V.”

I’d planned to use this to test the worst case scenario of how much energy could be harvested in shade when the battery is repeatedly drained to 11.1 V. After a few tries this worked on the first day but the next day (today) the battery voltage came up to 14.6 V but the test load stayed off with no power at all being sent to the load.

I’d expected Load Output “Conv. algorithm 1” to automatically switch the load on whenever the battery voltage goes above 13.1 V and automatically switch it off whenever the battery voltage goes under 11.1 V but this doesn’t seem to have happened today.

Perhaps my c. 50 W test load is too large?

“Always on” sometimes works as expected and sometimes doesn’t - with the load sometimes switching on and sometimes remaining off. I don’t want to use “always on” because of the risk of damaging the lead acid battery by discharging it too much.

This is the documentation I followed:

https://www.victronenergy.com/media/pg/Manual_BlueSolar_MPPT_75-10_up_to_100-20/en/configuration-and-settings.html

12V system: OFF when Vbatt < 11.1V, ON when Vbatt > 13.1V.

The battery voltage in settings is set to 12 V, Max charge current set to 5 A (less than the default 15 A) and Battery preset is left at Factory Default “Gel Victron Deep Discharge(2)”

I’m using a new BlueSolar MPPT 75 ¦ 15 Charge Controller with firmware updated connected to a new photovoltaic panel (445 W nominal, 39 V open circuit) and new 12 V 7 Ah lead acid battery. Connection to the Victron app. on an Android mobile is via a VE.Direct Bluetooth device. The test load is a 50W 12 V lamp. The maximum charge current for the battery is set to 5 A. I understand that this is a very large solar panel for this size of battery - I’m only testing the worst case scenario of a solar panel working in shade in a European winter - not the full output of the solar panel in direct sun in the summer - which would be much higher.

The VE.Direct Bluetooth device was left connected to the BlueSolar MPPT 75 ¦ 15 Charge Controller all the time but my mobile was only in Bluetooth range occasionally.

Will

2

I think the cause was simply that the 50 W test load combined with what I’m guessing would be a relatively high internal resistance of the 7 Ah lead acid battery would have caused a fairly large drop in the battery voltage with the load connected. With a larger 70 Ah battery and a smaller 20 Watt test load everything seems to be working as expected.

Are there any log files, etc. where details of device operation or fault conditions like this are recorded?

3

I have a smartsolar 75/15 with 240W panels and 70Ah lead acid battery, and am planning to use the load output this summer in the south of Ireland for a “solar dump” to a 100W immersion water heater (offgrid camping trip).
My primary concern is managing the output so that the battery doesn’t discharge too much. I can’t justify the cost of a shunt for a setup I use only 3 weeks in the year. I’m therefore relying on the smartsolar voltage readings to guess the battery SOC. I think there will be some trial and error to find the right output settings for my conditions - drawing 100W for about 4 hours during the peak solar generation (fingers crossed for sunshine). I’ve been advised in this community to start with 11.5V as the low voltage threshold.
Have you done any more testing of your 70Ah battery set up? I’m curious if you are content with the Conv. algorithm 1 or if you have tailored your own settings. I appreciate your priority is different, but perhaps you have learned something that would inform my set up.
Also, regarding anticipating solar output, have you looked at Globalsoliraltas? It gives average hourly outputs for all locations, azimuths etc. I’ve found it reasonably accurate - if conservative - for my home solar setup.

4

Hello WillRobertson,

i assume you noticed the changed jumper link placement in the documentation/manual? That’s important, but it’s easy to overlook it.

You didn’t explicitly mention it, but did you set (remove) the jumper differently?

The manual for my 75/10 has the following sentence:

5.1.2. Settings via the jumper link
If the load output algorithm is configured via VictronConnect or the MPPT Control display the jumper link is not used and it needs to be removed. Configuration via the jumper link is only needed in case the load output algorithm cannot be configured by any other means.

greetings