Shoul I add another Lithium-Ion Battery

DIY
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1

I live in Granada, Spain.

I am trying to determine whether or not to invest into a 4th Pylontech L1 3.55 Kwh , 74 Ah Lithium Ion battery ?

20 months ago, I invested into a Solar P.V. System through AutoSolar, Spain.

Total cost to date = 15,800 Euros. The initial Autosolar cost was around 11,000 Euros.

The initial installation proved to be woefully inadequate, primarily due to bad planning and too many assumptions on my part, assumed that Autosolar knew what was the best setup for my house ( they did not visit my property in advance ) & the Installation Techs knew what they were doing. Massive errors all around.

Over the past 16 months, I have modified the existing setup by adding 2 additional panels, changing the Inverter to a Multiplus II 48 5000 | 70A and installing adjustable frames for 5 out of the 8 Panels ( 25 Deg to 58 Deg - summer to winter - adjusted manually ). All south facing. Estimate about 120% charging efficiency improvement since the initial Autosolar installation in May 2023.

Endesa, the Grid supplier, charges me on average around 25 euros a month, every month, for the past 17 months, despite an excess of circa 850 kwh over the 17 month period ( 1st April 2024 to 1st Sept 2025 ) ; from the Endesa monthly invoices, there appears to be zero compensation for the excess Kwh but I am charged for periods where the SOC drops to the 30% set point where the Grid supply kicks-in.

The existing setup involves 8 x 460 Watt panels, 2 x Victron Smart Solar MPPT 150 | 45A Controllers, 1 x Gerbo GX Comms Module and a Victron Multiplus 48 5000 + 70A Inverter. The Battery Array is a Pylontech L1 48v, 10,65 Kwh with 222 amp hours capacity. ( 74 Amp Hours per 3.55 Kwh Lithium-Ion Battery. )

The panels are setup with 2 sets of 4 panels, with 4 panels with 2 in Series with 2 in parallel combination.

VRM Data from 1st April 2024 to 1st Sept 2025

To Grid 1699 kWh

From Grid 847 kWh

Consumption 5003 kWh

Solar 6880 kWh

I am partially convinced it will be cost effective in the long term to install a 4th PylonTech L1 3.55Kwh Battery, raising the capacity to 14.2 Kwh / 296Ah.

Cost of a Pylontech L1 3.55 Kwh Battery is around 1065,00 euros through Autosolar, Spain.

2

Hi Keni,

I run the same inverter as you and I have 4 x pylon batteries. I think it is a good match to have 1 pylon per kW of inverter. So, I think it is a good idea for you to increase to 4 batteries anyway, regardless of the kWh capacity of your battery bank.

It is a shame that your energy supplier does not pay you for the energy you are exporting. In the UK we have a good market for that energy.

As well as storing more energy for your own use in the house, is there any chance you could increase your consumption - for example by installing a charge point for EVs ? It could make you popular with your friends and neighbours :slight_smile:

The Victron EVCS works very well with the MP2 and can limit itself to only charging the EV with excess energy.

3

David

Appreciate the feedback. Exactly what I wanted to know.

I have more or less committed to purchasing another L1 3.55Kwh battery. Still trying to find an acceptable price - too many suppliers are ripping off the masses. I do like the idea of 1 PylonTech per KW Inverter.

I am in consultation with Energy Nordic & Evergreen Electrica to see if they have a superior grid excess return rate compared to Endesa.

4

For comparison, here’s my local supplier’s UK price list.

https://www.bimblesolar.com/pylontech-house-batteries

5

I don’t know the market in Spain at all, but you might also look at https://octopusenergy.es/en/precios/tarifa-solar

Octopus have introduced very innovative tariffs in the UK, including some for consumers who have solar and who want to get the maximum from their battery installations.

6

…. I did see Octpusenergy. This sounds promising. Will chase up tomorrow.
Saludos y gracias :folded_hands:
Kc