Hello community,
Just played around with the VRM and downloaded the production reports for the last 6 months.
Looking at the Battery section - Charge kWh vs. Discharge kWh and I was surprised that the ration between charge and discharge is around 70%.
The info is consistent and around this value for all months…
Am I missing something or the Pylontechs efficiency is so low?
How is yours, the ones with Pylontechs?
Thank you,
Alex
For example, below, the July report.
I am thinking that the difference between charge and discharge is also subject of MPPT and charger efficiency.
But let’s say 5% on MPPT and 10% on charger and still will be only 85% battery efficiency.
15% loss is battery LiFePO4 chemistry and electronics is BIG…
Inefficiencies compound. Wiring, chargers, battery etc.
At higher temperatures this is worse. At peak power efficiency is also less.
The BMS will also be consuming power, as well as the other devices.
It all adds up.
I will check my pylons and compare to the other manufacturers as a control.
Interesting question.
My pylons 71%
Another brand 86%
Well known brand 67-70% across a few sites.
To add. None of these charge from grid either.
So it’s consistent…
BMS consumption when the batteries are idle is about 50mA per battery so about 10kW per month all batteries on my configuration.
On average 50W are consumed by the inverter as idle consumption. So about 12kW per month loss on that 1/3 of the time when only on battery.
Ripple is no more than 80mV on a 50A consumption (2.5kW). Therefore no more than about 35 degr.C on cables.
Indeed, it adds up…
Which brand is 86% ?
Thats my own system. Single large battery (not modular): Freedom Won. Uses Orion BMS.
Possibly there are additional losses in stackable systems? (Multiple BMS’s, stacking cables etc)
Did you consider the SoC of the battery at beginning and end of the interval?
With a large battery, ie. 30kWh, and SoC 10% at start, 90% at end, you still have a charge of 30kWh x 0.8 = 24kWh left for discharge / unaccounted for.
Every day the system will top up the battery from a previous day’s cycle. So energy in vs energy out over an extended period is a reasonable gauge,
Well, I collect the various Power values in an influxDB and let grafana calculate the Energy based on the integral unter the Power graph.
This is from my last 90 days:
And if you compare vrm values for solar (to battery) and consumption (from battery), does it agree?
Last 6 months view.
Efficiency being a percentage of consumed vs charged:
Its fairly close to big bank i keep an eye on. I just use energy in and out of the bank figures.
Can say it is around 78%. This figure can be influenced by not daisy chaining the bank (as in it improves) as many are in the habit of doing.
But pylons being 15s lower voltage batteries are definitely more inefficient than the 16s counterparts. Or at least that is what i have seen in my experience.
How to generate such report in VRM? I have only economic and genset report
On VRM go “BACK” on the left menu to “All Installations” (My installations) page and in upper right you have a download button.
You’ll find the first option to be Download production report.
Interesting over six months my system’s (AGM’s) are at about 84% on my 48v setup & about 85% on the 12v setup.
Did persons monitor it for a long time and expand there battery package during the monitoring period. I expanded with 19,2 kWh and it seems that the efficiency increased by 4%.
I can partly explain this due to the lower C factor applied (decreased from 0.5 C to 0.25C).
In case this effect is that large it does not make sense to compare numbers without knowing the number of batteries installed.
Interesting question and I’m up for data collection and analysis (in case sufficient data is available).
Please provide the following information:
Battery model : (US2000 / US3000 / US5000, etc…)
Battery capacity installed : (kWh)
Connection method : daisy chained / parallel
Charged energy (last 6 months) : kWh*^
Discharged energy (last 6 months) : kWh*^
*Reporting period in case period is < 6 months : months
^report efficiency incase you do not want to report energy: %
Charge rate : C
Discharge rate : C
Operation mode : ESS / DESS (trading mode) / DESS (green mode) / off grid
Number of phases : 1 / 2 / 3
Inverter / Charger : MPII -3000 / MPII-5000 MPII- 8000 / MPII-10000, etc…
Let’s say here that we are talking about a total off-grid solution. The grid is / stays disconnected by the input relay.
So, here’s the data for me and thanks for wanting to make an analysis for us…
Battery model: US2000C (6 pcs)
Battery capacity: 14.4kWh
Connection method: parallel
Charged energy (last 6 months): 738 kWh
Discharged energy (last 6 months): 526 kWh
Charge rate: C100 - C5 (variable)
Discharge rate: C100 - C5 (variable)
Operation mode: No ESS (off-grid)
Number of phases: 1
Inverter / Charger: Multi RS Solar
Battery avg. temp: 25 deg.C (22-29)
I would add average temperature to that data. I would guess it makes a big difference.
F
My System, with Pylontechs also has around 75% total round-trip efficency.
I’m currently trying different settings and compare results, so far it seems that lowering the maximum charge voltage improves efficency.
When set “high” (i.e. values recommended by pylontech and even the lower recommendation of victron) I can see that a lot of energy is still being burned while the SoC already shows 100%.
The pylontechs have passive cellbalancing, so it only balances when reaching 100%, by literally “burning” power send to cells that already reached their voltage.
It seems that the higher charge voltage causes a way longer balancing phase, until the “weakest” cell reaches that high voltage, causing an overall higher waste of energy.
Currently i’m down to 52V as maximum charge voltage, still reaching 100%, but noted significant shorter “balancing phases” when soc reaches 100%.
In about 4 weeks i will evaluate if this feeling is also backed by data 
But beside that, 70-80% is a quite common number for Energy storage systems, nothing to worry about.
