How to Delay PV Charging??

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question

paulmetcalfe asked Mar 8, '24

How to Delay PV Charging??

Hi,

I have an export enabled ESS system but due to our location, our export-power is capped 50% below my PV generating capability. By default, the Colour Control GX ESS software priorities surplus PV to battery charging so by midday the batteries often full, with little or no energy being exported. Then, from midday, when generally higher PV output is available, the PV is often throttled due to the export cap and full batteries.

Is there a way to delay or limit PV battery charging until midday, so all PV power can be exported in the morning, regardless of battery SOC? From midday, when there's more PV energy than I can export, I’d like to charge the batteries too, thereby making maximum use of the available energy.

I know this is probably an unusual problem but I’m grateful for any ideas.

Thanks

Paul.

[20KW PV, 30KW Battery Colour GX, 2x SmartSolar MPPT RS, Dual MultiPlus]

ESS

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Modifications Space

Node Red Space

Answer 1 · 2024-03-08T17:19:26Z

Alexandra answered · Mar 08 at 05:19 PM

@paul.metcalfe

Do you have battery life on or off? Min SOC in case of grid faliure? Maybe share some of your other settings.

With node red it is possible to do all kinds of things, but with a CCGX you would need to add something to run it or swap out the GX to a Cerbo.

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paulmetcalfe commented · Mar 09 at 01:20 PM

Thanks Alexandra. Battery-life is off as we use LiFePO4's.

Happy to share my settings just let me know what's pertinent
Don't know anything about Cerbo yet but will do some homework, thanks for the pointer

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Alexandra ♦ paulmetcalfe commented · Mar 09 at 06:08 PM

You could add a raspberry pi and do something with mqtt as well. But the Cerbo has it all in one.

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Answer 2 · 2024-03-08T21:44:56Z

sharpener answered · Mar 08 at 09:44 PM

You could limit the charging current in the DVCC settings, would that work?

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paulmetcalfe commented · Mar 09 at 01:22 PM

I have experimented with charging current-limit but it only seemed to effect grid charing, not PV.

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nickdb ♦♦ paulmetcalfe commented · Mar 09 at 01:34 PM

Charging current setting is ignored when feed-in is enabled.

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sharpener nickdb ♦♦ commented · Mar 09 at 02:25 PM

Under what conditions? I have feed-in enabled and am still able to use Node Red to turn down the charging current at night to reduce fan noise, so didn't see why it couldn't be done manually.

I thought the actual limit applied was the lower of the setting in DVCC and the CCL set by the (Pylontech) BMS.

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Alexandra ♦ sharpener commented · Mar 09 at 05:50 PM

It set in DVCC by the battery, but if allowed to govern the system would then throttle the PV.

So the limit has to be ignored for feedback to grid to happen. This is mentioned in the manual (and also why it is important to dimension the battery correctly in a system.)

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nickdb ♦♦ sharpener commented · Mar 09 at 07:08 PM

It honours ccl, but as documented, won’t limit the solar chargers.

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Answer 3 · 2024-03-08T23:30:54Z

matt1309 answered · Mar 08 at 11:30 PM

Hi @paul.metcalfe@pobox.com

If Sharpener's suggestion doesnt work, then i think Alexandra is right in saying node red.

I tried drafting a function a few ago for someone to do similar. As Alexandra noted it was using node red, so would need a device that supports venus os large. It works by dynamically adjusting the grid setpoint during specific time frames.

Here's the thread. Theirs also checked voltage but you could remove that element and adjust the times to suit your timeframes

https://community.victronenergy.com/questions/267539/nodered-script.html

It is untested code and I'm no a pro dev (or a dev at all for that matter) but will hopefully be a decent jumping off point if you go that route.

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paulmetcalfe commented · Mar 09 at 01:25 PM

Thanks Matt. Coding is little beyond my skillset but I understand your suggestion and will try to explore. Thanks for the reply.

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matt1309 paulmetcalfe commented · Mar 09 at 01:44 PM

No worries. Happy to help with node red scripts if go that route and need a hand.

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Answer 4 · 2024-03-09T13:38:22Z

nickdb answered · Mar 09 at 01:38 PM

As long as your battery SOC is above the ESS minimum, it won't force all PV into the batteries, between that, and forcing a negative grid setpoint you could get close to what you want, but it would require dev work, node red is easiest.

I can't see another way of achieving this, as it isn't designed for this scenario out the box.

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Answer 5 · 2024-03-09T14:37:02Z

duivert answered · Mar 09 at 02:37 PM

can't you just use scheduled charging for this?

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nickdb ♦♦ commented · Mar 09 at 03:28 PM

Fair point. It has been enhanced a lot. You can set your setpoint, you can set it to only use PV for loads once at a charge level, and you can set schedules with lower SOC limits which would enable controlled discharge of the battery.

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matt1309 nickdb ♦♦ commented · Mar 09 at 05:23 PM

I didnt realise it worked like that. Pretty cool if it does.

So if i set soc in ESS schedule charging to 10% and self consumption above limit to PV.

If im at 20% soc this will use PV for loads and the excess is exported?

If so that's cool, didnt realise that was a feature, i thought it would just send pv -loads to battery still rather than to grid

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sharpener nickdb ♦♦ commented · Mar 09 at 05:46 PM

The new improved Scheduled Charging was my first thought, but I am not convinced it will do what @paulmetcalfe wants. Maybe @nickdb you can post a worked example of the settings you envisage?

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nickdb ♦♦ sharpener commented · Mar 09 at 07:07 PM

I’m not convinced either, it may do 90% of it, and doesn’t require dev work..

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Answer 6 · 2024-03-09T18:05:22Z

Alexandra answered · Mar 09 at 06:05 PM

@paul.metcalfe

Came up with a different idea in my musings.

I have not personally tried this for this particular application but it is worth a try for you. If I get some free moments I will give it a go. It won't stop the DC PV charging the battery but definitely the AC PV.

You need to use the CCGX relay and the generator start stop finction (not sure if you are already using it.) set the times you want the charger to start/stop charging on AC.

Use the charge current control assistant. Connect the GX relay to the aux 1 input (you will see it come up in the assistant needs 1.00 to 4.00v input) and then the two should interact. It may be able to see the charger to zero but at the least will see the charge amps right down.

Easy way to play with the assistant is run ve config in demo mode and see how it is set up. And go from there.

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Answer 7 · 2024-03-09T18:57:37Z

paulmetcalfe answered · Mar 09 at 06:57 PM

Thanks.

Unfortunately, all my PV is DC.

I want to prevent the PV's DC being consumed by the batteries in the morning, even though they may not be fully charged. If the batteries were at 100%, the GX would automatically export any surpless, so I know it can do it. I wondered about simply taking the batteries off-line. I tried manually swicthing them off but then the MPPTs simply shut down too.

Looks like, unless I can fool the GX into thinking SOC is 100%, it's probably a problem that can only be resolved in software, so your Cerbo suggestion makes most sense to me. I need to read up Cerbo's though, it's all new to me.

Cheers for the help though

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