Hi, i have a lot of consumers in my home i can schedule on or off on demand to allow to be close to 0 consumption during the day with my 6.8kWp solar array on my roof. During the night i consume between 2-3 kWh only. When i ran 10kWh, 5kWh and 2kWh battery simulation the 2kWh already provides enough capacity most of the days. From my boat i have a 50 Ah 48V Lifepo4 Battery and i wonder if it would work to use it with a multiplus in my home. I know many of you are proud owners of larger batteries. But is going below the 100Ah recommended for the 3000 Multiplus an issue? I know staying between 10 and 90% gives me even less capacity.Regards, Marcus from Heidelberg
Read the documentation of your battery. It probably says that the battery should only be charged or discharged at a maximum of 0.5C. In your case, that’s a maximum of 25A, or approximately 1280W. However, your MPII-3000 already draws 2400W from the battery at full load. That’s too much for such a small battery. And the 6800 Wp from your solar modules are far too much!
2.4kw battery is way below recommended minimum of 4kw, starting the multiplus can already be an issue with such a small battery depending on Max discharge rate it can do (as suggested already)
the pv you already have will only be too big if its on ac out of multiplus, if its on ac in side its no problem
My max discharge and charge rate is 50A. I plan to configure the Multiplus to not charge or discharge faster then 50A ahead of adding the battery. My PV will be on th AC in and the bulk of the surplus will go into my electric car or into the grid.
I will use multiplus only as a small ac coupled storage.
As suggested check your battery specs its unlikely it can be charged or discharged with 50A
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Not only you, but the majority of people are unwilling to pay more and tend to reassure themselves that minimal capacity is sufficient and their consumption is low.
In addition to what has already been stated, I would like to highlight another critical consideration.
Manufacturer recommendations are based not solely on the technical specifications of components, but, more importantly, on SAFETY. Safety is the fundamental principle upon which all energy systems are built.
Operating close to the maximum allowable charge/discharge current results in accelerated degradation of battery cells and a significant reduction in their service life.
Charging/discharging with over current introduce the same effects, but with significantly increased risks of structural failure cells, which may ultimately lead to catastrophic consequences.
That is roughly how things stand in the Kingdom of Batteries.
Good luck.
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I checked the battery specs from powerqueen. These are 2x24v in series (with a balancer) that can each do 50A continous charge or discharge. As they are in series this is still 50A at 48V. From what i hear i should probably run them at 40A max both for charge and discharge which i assume can be set in the multiplus as maximum rates.
Lets assume the batteries are ok (40A, only using 2kWh) - what else is in the way otherwise when using a battery that is not 100Ah but 50 Ah?
Greed and short-sightedness.
UPD: By the way, are you even aware that connecting two LFP batteries in series isn’t allowed?
Just so you know, it’s one of the sacred tenets of the Battery of Kingdom.
… i was thinking more of real technical boundaries. I understood that 50A is too much so i go below the manufacturer spec to 40A. Can the Multiplus not be configured to do less then its maximum? Is this now not safer? Who does not allow 2 lifepo4 batteries in series? The manufacturer of the battery or Victron?
I just want to use the existing batteries i have anyway and buy a multiplus gx to have a small temporary buffer for electricity. I know bigger systems is what other people do. But for example the hoymiles ms-a2 is the only other ac coupled battery that i found and also only offers 2kWh. Internally its 48V as well and can charge and discharge with 1,8kW each which is about 37A at 48V. I understand also having a smaller battery will put more stress on those batteries and the number of cycles will be reduced.
Is there any other real technical limitation that forces me to upgrade to 100Ah?
Read the update above
I have seen the specs too, they are allowed in series parallel , 4p2s is the max
however recommended charge is 0,2C (10A), so charging always with 50A will drastically reduce their life
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In the meantime i learned 2 things in the community that are real technical limitations:
a) there is an in-rush current when the batteries are connected to fill capacitors in the multiplus 2 and this is not limited - it must be in the range of the 125A fuse recommmend for a 3000/48 system and this more then what my 50Ah batteries can deliver.
b) under certain conditions (short, grid failure) the multiplus 2 does not limit the curent pulled from the battery and inverts 3000W or even peak 5000W from the batteries. This is 104A at 48V and again way above the 50A.
So the ability to control the discharge current and the charge current in an ESS is not sufficient to protect the batteries in the above extreme cases, right?
I‘m now considering a multiplus 1600VA to match my battery. What i need to check there is how to add NA protection and how to control the charge or discharge rate in an ESS.
Sorry to butt in like this. You’ve already been given a lot of advice. I understand frugality, but what you want will be more expensive in the long run. Of course, battery manufacturers specify high charge and discharge rates. Personally, I think 50A and 0.5C are too high. You’ll drastically shorten your battery’s lifespan. The manufacturer claims it’s safe until the warranty expires, but no longer. I also think buying a smaller inverter now is extremely short-sighted; power consumption will increase in the long run, not stagnate or fall. I would always try to install a truly appropriate system without compromises. If it’s not financially feasible at the moment, then maybe save up a bit and wait. Everything you’re planning will be expensive in the long run. These are all just nice suggestions.
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That’s correct. Of course, there are systems with sequential connections of large numbers of arrays, but that’s a different story from the HV league, where each segment is managed by specialised BMS that aren’t available for LV.
I run a 12V 1200VA with about 380AH or 4kwh of battery connected ATM. Its a good fit. I charge and discharge it everyday using ESS and DVCC to limit the charge current and time of day it charges to soak excess solar and maximise the small array. It is only small but I can scale it depending on what I am using the batterys for and how much energy the house is using. I sometimes have up to 10kwh of 12V batteries connected.
