I have a single Multiplus II (15K) which I am planning to setup to offset daily and nightly power usage.
I have 2 x 15kwh lithium power walls being configured for the Multiplus II (15K). The goal is to eliminate grid power draw completely.
My plan was to have one 15kw battery charging while the other is servicing loads. This way power draw would be serviced by the batteries, until 80% DOD rather than draw any power from the grid.
Is this a standard configuration that can be programmed through the default interface? OR would this be achievable or practical to do with an automatic transfer switch type setup.
The multis, like the quattros, can either charge or invert they can’t do both simultaneously.
It has one AC input, and it requires a DC battery, it cannot be used AC only.
I would encourage you to do the basic, online, free training, which should clear things up.
What you appear to be trying is neither standard nor supported.
Thankyou Nick, while i have done lots of research in preparation there are still plenty of gaps in my knowledge. I was not aware of that fact that a multi is limited to charging OR inverting. I clearly need a second inverter as that is a fundamental limitation.
Aside from that major oversight I hope it is still possible to charge and use batteries separately so while one is charging, one is cycling. Would this be possible if the inverters are in parallel.
No, parallel inverters are one logical system they behave the same under the control of the master.
You can have separate dedicated chargers - mppt’s, Skyla etc.
Hello LX. I have 2 x 250V mppts from 10kw solar (outputting 8.2kw). The plan was to charge 15kw battery 1, then 15kw battery 2.
I also have a lynx, a cerbo and distribution box as well. Nothing constructed as yet but I have mapped a basic topology. So solar is my charge source, but grid never will be.
Also the plan was to cycle each 15kw at least twice per day to service a 40kw daily draw.
Thankyou Nick. That is good to hear because the inverter was not cheap. I probably should have mentioned in the post that I have 2 x 250V mppts for the >8kw solar input (4 strings@250v), a cerbo, a lynx and a distrib box.
While I have done basic topology I have not started the build, nor have i received the batteries yet. I will then engage a local electrician to assist the setup.
Just reading your last post that too is a fundamental issue. I thought VE Can 1 vs 2 may enable separate communication, but obviously not the way I thought it may. I thought at some point the 2nd battery would have to switch on, in the 10ms or so that it has, and then match the delivery load of the inverter at that time so probably a big ask of the system.
Something else to consider, the system only understands the concept of one battery. Batteries are typically connected together and the BMS presents one large pack to the system (assuming it is a supported or compatible one).
It has no way of treating individual packs differently.
I would have a chat to a skilled supplier to help guide you, it is easy to end up wasting money and not being able to achieve what you have in mind.
Either you have a very specific reason for that plan to charge the batteries separately and switch them in some way, or there’s a misunderstanding about the way the system works.
Because if you just hook up all the components you mentioned to your Lynx, what’ll happen is this (simplified): your MPPTs will send power to the bus, and your Multi will draw whatever it needs to feed the AC loads. If that is less than the power provided by the MPPTs, the difference will go into the batteries. Otherwise, they will be discharged.
If your batteries are healthy, they’ll both charge or discharge with about 50% of the total power.
If there is excess power and the batteries are full, you can either export to the grid or the MPPTs will be throttled to not overcharge the batteries.
Hello Christian, thankyou for the response. The very specific reason was to be using battery power 100% of the time as grid power is costly. The primary objective was to have a simple system where one battery charges while one discharges, and at night utilise battery until both are 80% dod, then and only then use grid power, as it is flat rate with no controlled load 2 or time of use benefits. The TOU meter would push daily connection to $5 per day which offsets any savings made by using power at cheaper times.
Any power given to the grid is wasted and I would need 20kwh of wasted power to offset the daily connection of ~$1.50. Similarly any solar given away at 7c is brought back at 35c that same day. These are the reasons for my investment.
There are many automatic transfer switches that may be integrated, but need to at least be 100A rated and consistently switch in less than 10ms to not disrupt power.
As for excess power once batteries are full, if there is any, hopefully that would offset daily connection costs pushing my bill closer to zero.
Consider yourself lucky, because you’re not alone with those requirements, so they are covered by the standard ESS mode of a Victron system, without switching anything around.
E.g. my grid meter reports that today, I imported 0 Wh and exported 190 Wh, and my 8.2 kWh of PV production was either consumed or stored in my batteries, so I’m ending the day with 10% more SOC in the batteries than at the start.
Your stated system is also less efficient, due to charging & discharging losses.
If solar PV power is being produced and AC power is required, it is pointless and wasteful to charge one battery with solar pv while discharging the other battery. It is much more efficient to simply cut out the charge/discharge process and use pv power directly to provide AC ,with any excess charging battery.
As stated simply connect both batteries and let ess do its thing - using all available power in the most efficient way.