SmartSolar MPPT in combination with a charger like the Blue Smart IP65

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frankhe asked Apr 10, '24

SmartSolar MPPT in combination with a charger like the Blue Smart IP65

Hi, I have searched the forum but was not able to find a clear answer yet.

I am looking to create a stationary solar setup on the African continent using a string of solar panels and a Victron SmartSolar MPPT to run some 24 Vcd equipment and charge an AGM battery bank. To assist the solar charger I had a look at the Blue Smart IP65 series to top up the batteries on days when sunlight is not bringing enough energy. 230 Vac is available on-site but there are regular power outages due to load-shedding, this is why I like the solar installation to be the primary system that delivers power. The total continuous power the system needs to produce is around 150 Watt or 3.6 kWh per 24 h.

For a proper setup I might need the following:

A SmartSolar MPPT
A charger like the Blue Smart IP65 or comparable
A SmartShunt
A Smart Battery Sense

Solar panels and batteries will be sourced locally.

Now is the question, can I put these four devices in a BlueTooth network using VictronConnect and have them work together? The important thing is that the batteries don't get overcharged, I would like to stick to the recommended 0.1 C, putting two chargers in parallel without monitoring the total current is not an option for me. Is there maybe one product that can do all of this in one single device?

I won't be needing a 230 Vac inverter because all equipment capable of using 24 Volt. Any insights are welcome, thank you in advance.

MPPT SmartSolar VictronConnect AGM Battery

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Modifications Space

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Answer 1 · 2024-04-10T10:57:17Z

Sarah answered · Apr 10 at 10:57 AM

Hi @Frankhe A solution utilising a cerbo GX or similar and a dvcc charger (that supports STS, SVS and STS) would likely meet you requirements. Unfortunately the Skyla does not have full DVCC support. See the GX manual on DVCC. https://www.victronenergy.com/media/pg/Cerbo_GX/en/dvcc---distributed-voltage-and-current-control.html#UUID-31297d55-7904-84cc-b74e-4c5ae2ed1512

I would recommend an equivalent sized Multiplus and mppt controllers which fully support the DVCC feature set. Sarah.

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Answer 2 · 2024-04-10T14:43:05Z

regman54 answered · Apr 10 at 02:43 PM

If it helps at all I can answer part of your question. I have each of the four devices on your list. The only device that cannot communicate with one another over VE. Smart networking is the Blue Smart Charger.

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Answer 3 · 2024-04-11T08:51:07Z

frankhe answered · Apr 11 at 08:51 AM

Thank you @Sarah and @regman54 for your answers. I was thinking, the MPPT charge controllers have built in current measurement. Would the following setup be an option?

I take two MPPT controllers, connect the PV string to the first one and connect the auxiliary charger to the second one. Have both charge controllers work together in a VictronConnect Bluetooth network. See drawing below.

This should guarantee proper charge voltage limit (CVL) and charge current limit (CCL) without the need of a shared current sense (SCS), is this correct? I am less interested in shared temperature sense (STS) because I don't expect any problems when I keeping the charge current to 5 A on a 50 Ah battery bank.

With two MPPT controllers I could even program both load outputs to cut out at different points and disconnect low priority loads earlier so I can keep powering high(er) priority loads for a longer period of time.

Would all of this work? Any tips?

pv-charger-concept.png (202.3 KiB)

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Answer 4 · 2024-04-11T09:38:01Z

kevgermany answered · Apr 11 at 09:38 AM

Just looking at this, the main problem is lack of integrated control over the chargers. The second MPPT is a bit of an expensive hack.

It also looks as if a full GX device is overkill on cost for a small system.

Suggestion.

Consider a Raspberry Pi running Venus OS. This is your GX and control.

Use the RPi to switch the IP65 through a relay.

You'll need to investigate (look in/ask in the modifications space). And invest some time in building/maintaining.

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Answer 5 · 2024-04-11T11:12:28Z

frankhe answered · Apr 11 at 11:12 AM

@kevgermany thank you for your reply. I have not worked with VictronConnect before and maybe I did not understand it correctly that several MPPT chargers can work together in a Bluetooth network and manage the same battery bank and coordinate charge stages? I thought this was possible?

I am happy to get two (relatively) affordable MPPT charge controllers if this means I can have a simple and robust setup without any auxiliary components. I might even keep a third MPPT on-site as spare.

The idea is to create a concept that I can replicate in many different places using high quality Victron controllers and locally sourced solar panels and AGM batteries. The Chinese made charge controllers you can buy locally in African countries are just not up to my standard.

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kevgermany ♦♦ commented · Apr 11 at 11:58 AM

@Frankhe

Understand your concerns about what's available in Africa. Load shedding is a SA term.

CCL, CVL, SVS are really only part of DVCC in Venus OS.

Yes the MPPTs can connect with Bluetooth and coordinate charging. Victron call it smart networking.

But you wanted to stop the charge from AC when there was solar available. That requires an automated control function. And in the Victron world that comes from Venus OS, either running on a GX device, or on a Raspberry Pi. Without this the AC charger is running continuously, burning power you don't want to use.

Thinking more about it, a simpler way would be to simply measure battery voltage with an Arduino, and use that to switch a solid state relay which controls the AC input to the mains charger. Switch on when voltage drops to 24V, switch off at 28.8V. I did something similar, but used temperature sensors and switched cooling fans on and off for my van batteries. Arduino nano, cheap DC:DC buck converter to drop battery voltage to 5V, relay.

With a simple system like this, using AGM batteries you don't really need a balancer. The batteries will self balance, as long as you don't hammer them.

So the system becomes

Panels feeding the MPPT which connects to the batteries.

Arduino nano plus resistor bridge to measure battery voltage. Program.

Buck converter to drop battery voltage to nano requirements.

DC:AC relay driven by the Arduino to switch AC feed to the charger

AC fed 24V battery charger.

2 busbars to consolidate the battery connections.

Weatherproof and tamper proof box. With suitable shading and ventilation.

I'm moving this to modifications, we're way off scope for Q&A.

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frankhe kevgermany ♦♦ commented · Apr 11 at 08:36 PM

@kevgermany, thank you for your input. Meanwhile other countries in Southern Africa have become custom to the term load-shedding for all (somewhat) planned outages.

The goal is to keep the power consumption from the 230 Vac grid relatively low, not necessarily zero. Fact is, the grid will probably be unavailable half of the time anyway. It is all very low power, a maximum peek of 300 W continuous and about 150 W or even less throughout the night. The goal is to enable people to be able to charge their phones and to run a WiFi internet solution.

I would like to stay away from Raspberry Pi's, Arduino's and the like because of difficult serviceability in the field. I'd rather standardise on one unit, like for instance the SmartSolar MPPT 75/15, have these do all the work and keep a couple of spares in the area. A single unit that can be swapped out by basically anybody and is easy to setup using a smartphone app. Although I do not expect these MPPT units to break anywhere soon.

The concept is simple. Think of it of having two PV strings and two MPPT controllers, each having one string. Both controllers connected to the same battery bank. My idea is that the two MPPT units communicate with each other using VictronConnect Bluetooth and keep the collective charge current limit (CCL) to let's say 5 A. Both using their own built in (decentralised) current sense without the need of a shared current sense (SCS) at the battery. I this how a VictronConnect Bluetooth network is suppost to work?

My modification would be to have one PV sting on the first MTTP controller and connect the heavier (low priority) load of about 250 W to that unit. It will therefore direct more power to that load and utilise more of the solar power.

A CV/CC power supply like a LED driver (not a PWM driver) will be connected to the second MPPT for the auxiliary supply. A 230 Vac power supply that tops at 150 Watt or so. The second MPPT will take as much as it can from the grid and has the low power (high priority) load of about 50 W connected on the load side.

In this way I only need two MPPT controllers and can standardise on components. I use the current sense of both units and create a 'virtual' shared current sense (SCS) without the need of an (actual) external current sense.

This is at least the concept I have thought up when reading the information about a VictronConnect Bluetooth network.

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Answer 6 · 2024-04-12T05:18:01Z

Charge current is set individually on each MPPT. Without a BMV 712 or GX, there's no current coordination between the MPPTs. You can set different current limits on each MPPT. Sorry if I misled you here.

Load output is direct from battery and is controlled by battery voltage not current. It simply disconnects the load when battery voltage drops to a preset level. With multiple MPPTs on the same battery, each will deliver max current to its loads until voltage drops. So no control there, although you can set different cut off voltage levels on each MPPT. Net result is you gain nothing with a second MPPT.

Smart networks coordinate voltage and temperature only.

Smart battery sense does not help, also voltage and temperature only.

MPPT is designed to work from and control panels, while they're often used for other purposes, it's not optimal and may invalidate your warranty. It must also have a battery on the output side.

Remote maintenance and configuration may be an issue with different settings on two identical MPPTs with non-expert technicians.

Victron Connect and Victron Smart networking are not the same thing. Victron connect is an app that uses the Bluetooth communications protocol to retrieve data from devices, program them and update firmware. Victron Smart networking is a simple network that allows Victron units to communicate, coordinate. It also uses the Bluetooth communications protocol. Not all Victron units can use it.

As I understand it, simplicity and ease of support are key here.

To fully achieve what you need a GX is necessary. The generator autostart could be used to switch AC charger based on battery voltage. But avoiding that:

Suggestion

1 MPPT per installation

1 AC charger per installation.

Limit concurrent phone charging.

Size batteries so that there is enough capacity to service all loads for 12 or more hours without dropping below 50% SOC. Increase this by at least 50% due to working in hot conditions, and to extend battery life.

Size panels to cover load for 48 or more hours in one day to allow quick recovery after a poor day.

Connect all loads to the MPPT load connections.

Set up AC charger with a very low float level, say 24V if possible. This will minimise grid consumption while not allowing batteries to be damaged by over discharge.

But my knowledge is lacking about other alternatives, and we're not supposed to discuss detailed design here.

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