Batteries in float, lots of solar, how much can I power?

[SoakedUp]

Current setup:

6- 320w panels. Wired in 3s2p. 120voc 20a

1- 206ah SOK 12v battery. Max 50a charge rate

1- Victron lynx distributor

1- 150v/100a Victron charge controller

1- 12/1200 Victron inverter



My question:

I have the MPPT limited to 50a charge due to the battery charge rate limits. My battery is full and in float by 10am. When my load exceeds 50a and I have the solar to cover up 100a will the power still be directed through the MPPT to the inverter? Or will the max load from solar still be limited to 50a? Say I turn on a small portable AC unit that pulls 80-100amps. Will the power be drawn from the battery and the solar will just charge the battery at a 50a rate eventually draining the battery?

 

[Supervstech]

Why is the battery limited to 50A?
That is horrible for 200Ah
Anyway, if the mppt is limited to 50A, that is all it will output.
It will clip any excess production.

 

[Supervstech]

Now, if you have an all in one inverter, you can set charging to 50, and excess will go to thw inverter loads if present.

 

[SamDeleted]

So youve got 2kw~ of solar

But your mppt, 50amp @ 15v?? That's only 750w at most

Looks like you're missing out on most of your solar production. Get another battery?( I'm not sure if the bms's will play well together?)

Two in parallel , that would give you 1500w even then you'd still suffer losses

 

[SoakedUp]

Why is the battery limited to 50A?
That is horrible for 200Ah
Anyway, if the mppt is limited to 50A, that is all it will output.
It will clip any excess production.

Yeah. I think it’s been discussed on this forum about the low charge rate for the 12v SOK batteries. I believe people have reported being able to get up to 70a before the BMS cuts it off but the manufacturer recommends 40a with a max of 50a which may be an under rating.

The plan is to get 1-2 more batteries which should give me 150a of charging capacity.

 

[SoakedUp]

So youve got 2kw~ of solar

But your mppt, 50amp @ 15v?? That's only 750w at most

Looks like you're missing out on most of your solar production. Get another battery?( I'm not sure if the bms's will play well together?)

Two in parallel , that would give you 1500w even then you'd still suffer losses

Panels are flat mounted on a shipping container at an off grid location in San Diego, CA. I’m usually only at this property during the fall, winter, spring when the sun is fairly low. Summers are 100-120 degrees so I’m typically not there but until I get further along with the build and I can automate more stuff with a small AC this is my situation. I wanted to make sure I had enough solar to keep things running and charge the batteries quickly so a little excess is ok for now.

The plan is to get 1-2 more 206ah batteries which should help use all the solar.

I just wasn’t sure if the MPPT could divert the extra solar to the inverter with out exceeding the 50a charge rate of the single battery at this time.

 

[SoakedUp]

Now, if you have an all in one inverter, you can set charging to 50, and excess will go to thw inverter loads if present.

Are you talking about charging from grid or generator in this scenario? Or charging from MPPT. I don’t see why it would be different in an all in one unit if you limit the mppt to 50a in the AIO but not in a component system.

 

[pollenface]

Float pulls the power needed from the panels to maintain float voltage. If you exceed the available PV charging power for a sustained period of time the battery voltage will drop and may trigger a "rebulk" event.

What you can power will depend on the discharge capability of those batteries and the surge capacity of your inverter.

 

[SoakedUp]

Float pulls the power needed from the panels to maintain float voltage. If you exceed the available PV charging power for a sustained period of time the battery voltage will drop and may trigger a "rebulk" event.

What you can power will depend on the discharge capability of those batteries and the surge capacity of your inverter.

So I’m limited to a 50a current if I don’t want to start draining my battery even with enough solar production up to 100amps and a charge controller “capable” of 100a. The mppt isn’t smart enough to divert the excess power directly to the inverter I guess.

 

[Mattb4]

So I’m limited to a 50a current if I don’t want to start draining my battery even with enough solar production up to 100amps and a charge controller “capable” of 100a. The mppt isn’t smart enough to divert the excess power directly to the inverter I guess.

You have to understand that the DC bus, that the battery, inverter and SCC are in parallel on, has no idea of how much potential solar power you have. If a load is placed on the DC bus either the SCC or the battery provides it based on who can pump out the higher voltage. Your battery is either acting as a load or as a supply to the DC bus. When it is a load the SCC follows its charging rules to bring the battery voltage up to set charged level. Any load placed onto the DC bus from the inverter takes away current going to the battery. So if you have a load requiring 30a the battery will only see 20a charge.

It is called a charge controller because its purpose is to charge a battery. Once the battery is charged it shut downs to a float level or nothing.

 

[pollenface]

It's not a bad thing if you trigger a rebulk event as the battery is already "mostly" charged and will flip back into absorption/float again quickly

 

[Supervstech]

Are you talking about charging from grid or generator in this scenario? Or charging from MPPT. I don’t see why it would be different in an all in one unit if you limit the mppt to 50a in the AIO but not in a component system.

Because all a charge controller can do is set output amps.

An all in one inverter is an inverter AND a charge controller.
So it has the ability to set a limit on what goes to the battery circuit, and can divert the rest directly to the inverter.

 

[Mattb4]

Because all a charge controller can do is set output amps.

An all in one inverter is an inverter AND a charge controller.
So it has the ability to set a limit on what goes to the battery circuit, and can divert the rest directly to the inverter.

You lost me on this. The battery circuit and the inverter circuit is the same DC circuit.

Setting max charge amps sets max amps unless you somehow can remove the battery from the circuit. Even if you did there is no setting for max PV charging current with battery disconnected and max with battery connected.

 

[Supervstech]

You lost me on this. The battery circuit and the inverter circuit is the same DC circuit.

Setting max charge amps sets max amps unless you somehow can remove the battery from the circuit. Even if you did there is no setting for max PV charging current with battery disconnected and max with battery connected.

An all on one inverter has the ability to operate via solar input only, battery only, ac input transfer, or a combination of all.
The inverter can allocate output between battery charging and inverter output.
So, if the mppt is set to output a max charge to thw battery of 50A, but solar is outputting more current, it can switch away from the charging to the inverting.

 

[Mattb4]

An all on one inverter has the ability to operate via solar input only, battery only, ac input transfer, or a combination of all.
The inverter can allocate output between battery charging and inverter output.
So, if the mppt is set to output a max charge to thw battery of 50A, but solar is outputting more current, it can switch away from the charging to the inverting.

Sorry but your answer is not an answer. There has to be a path for allocation between components and a means to isolate them from all being connected together to do what you say it can do. Show me in any operation manual a charge limit setting for PV when not wanting to charge battery.

These things have a common DC bus. If the bus voltage is drawn down by a load the SCC acts to bring it back up by increasing PV production. If the battery internal voltage is higher than the PV is capable of supplying, at any given moment, it begins adding current to the circuit. This is how PV and battery work together. Without this common DC bus the load would overpower PV production (clouds, lack of sun) and the battery would not add in.

So unless you can provide a mechanism to isolate the battery, while also not isolating it, it will not work that way.

 

[Mattb4]

To explain a bit better how the common DC bus works I am linking to a older Thread that covers it a bit more thoroughly. https://diysolarforum.com/threads/loads-and-battery-on-common-dc-bus-from-scc.51157/