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dgmar-ni avatar image
dgmar-ni asked

Powering a telecom with smart solar MPPT and rectifiers

Good day,

In a telecom system configured in -48VDC, the radio base has a lithium battery bank for backup and rectifier for supplying power to the radio base, and at the same time to recharge the battery bank in case they have been discharged in the event of a blackout.

The owner of the system wants to know if its possible to have a solar system with a smart solar MPPT to supply solar in -48VDC to power the radio base with the purpose of reduce the power coming from the rectifier (grid connected) and only in the case of low solar or at night the rectifiers will supply the radio base. Besides if its possible to monitor how much power is coming from solar and how much from the rectifier.

Any advice will be indebted.

MPPT SmartSolarmonitoring
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3 Answers
hardy-tuner avatar image
hardy-tuner answered ·

Theoretically you don't need a control unit, when u use some voltage Ranges from all three sources. For example when mppt brings 49-50v in the System, the current flow goes to Equipment and battery, and rectifier goes Close to idle (what is idle voltage from this device without load? )

Mppt use is anyway only possible with battery as Buffer, otherwise hole System would switching very often between inputs in scenarios with low pv and Maybe not stable as needed, addionally maybe to use daily overproduction till SoC goes Close to Backup Power Limits.

In my opinion System Control Unit(SCU) and cerbo should and could co exist, without direct or little compound them. Because you need some messured Parameters (battery,solar) to control the current flow with the SCU and how you want to do that? Battery charging is controlled also by SCU?

if the SCU cant do that, you need something with that data like a cerbo (which gets it from battery shunt, mppt). Cerbo can simple give a relais off/on which is used by SCU to make the algorithm possible.

Is there really a switch at battery like in your drawing?

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hardy-tuner avatar image
hardy-tuner answered ·

It’s possible to have a solar system with a smart solar MPPT to supply solar in -48VDC to power the radio base? Yes

Besides if it’s possible to monitor how much power is coming from solar and how much from the rectifier? If you using a victron smart solar mppt, then u see solar power local via Bluetooth. In combination with cerbo (or raspberry with Venus os) u can watch and monitor remote, optional lift up the data to VRM portal to share and having history.

The rectifier is already there, u need a energy meter on dc (smart shunt) for calculating battery SoC optional ac (depends from grid and your device https://www.victronenergy.com/meters-and-sensors/energy-meter

But now comes the bit difficult part, to optimize everything to solar/battery powered with less grid. Easiest would be to change the rectifier to go all victron setup, where is already everything in you need to configure your wishes.

Otherwise to switch off/on or lower usage from rectifier when needed, it’s not impossible but for that more information needed from your installation

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dgmar-ni avatar image dgmar-ni commented ·

Thank you @hardy tuner for your response. I understand is quite challenging as we are not in the scenario where we can use a complete dc coupling system with Victron inverters and the idea is to integrate solar with the existent devices on the telecom system as follows:

schematic.png

And moreover, for this System Control Unit to figure out if will be compounded with the GX device, a smart shunt or BMV. The idea of working principle is according with this algorithm:

algorithm.png

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algorithm.png (73.1 KiB)
dgmar-ni avatar image dgmar-ni commented ·

Hello @hardy tuner,

We have installed the MPPT solar charger on the DC bus bar in the radio base where the load and rectifiers are connected in parallel. I have installed also a smartshunt but I haven't set it up yet as an energy meter to measure the load consumption it only monitors the battery SOC. The battery bank in the radio base is not cycled everyday it they run only as backup.

See the outcome for solar on VRM:

1715357319060.png

Everyday early morning the solar charger runs normally as the solar incidence goes up but from 10:00 a.m. it drops to a minimum value as if the solar enters to a competition with the rectifiers to power the load. I will configure the smart shunt as DC counter to measure the power coming from rectifiers but if that is the case, that solar and rectifiers are competing, I don't have any clue how to control rectifiers. Maybe as you mentioned with Cerbo GX through its relays.

Any suggestion will be appreciated.

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1715357319060.png (31.7 KiB)
dgmar-ni avatar image
dgmar-ni answered ·

Thank you @hardy tuner for your assistance. I believe as you said cerbo GX and RBS SCU could coexist and I think solar charger and rectifiers will enter in some "competition" to support the load under certain voltage conditions. I think components can be installed as follows:

telecom-solar-dc.png


telecom-solar-dc.png (2.3 MiB)
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