Idiot's guide to a self build battery

[MrPablo]

I’ve been giving this some thought…

If you’re ditching the 15s Pylontechs, why go 16s and not 17s?

I believe your inverter’s charge voltage can be set to 42-60V, given that Victron recommend charging 15s Pylontechs at 52.4V then this extrapolates to c. 59.4V for a 17s setup.

This is an intriguing idea, it would unlock a lot more discharge power for those of us with inverters that do a max discharge of 65a or so.
I might have to look into this further, especially as selling my Pylontechs will be quite easy I think.

[marshman]

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[Countrypaul]

Check your cooker, some do mange the total load used by the elements to kee the peak down, obviously doesn't apply if you have separate ovens, hob and microwave.

[Oldgreybeard]

OGB, you clearly have your housemate (s) well trained !! can't see any massive sustained peak loads. My wife refuses to stagger loads - so brews a pot of tea, boils an egg, makes toast and uses the microwave all at the same time and sometimes goes for the washing machine whilst waiting for that lot ! Just seen nearly 7kW on the power meter (conveniently placed in the kitchen - but totally ignored) - I had a panic attack so checked where it was all coming from and was relieved that only 250W was coming from the grid - most was from the 6kW Solis inverter and battery with a few hundred watts from the other PV system, lucky it is a "bright" day. The peaks are short lived - except when the same person decides to tumble dry the washing at the same time as dinner is being cooked in the evening , but it explains the "leakage" of the odd peak rate unit or two into the house.

Tempted to fit some intelligent "power management" to the high power kitchen appliances - so that they can't all come on at once. Must be possible to fit/wire the cooker so that only one (maybe two) elements can come on at a time, despite my "man splaining" everything gets switched on at once - a simple bit of logic and a few relays could solve that. I might also reduce the peak power of the toaster by rewiring the elements or powering it via a transformer to reduce the voltage - I am sure she would never know

We're pretty good at only having high loads on overnight, or when there is a lot of PV generation. This is our power consumption for the same period (the past week) and shows that the big loads are only on during the off-peak period, and that we always stay under the inverter max power plus the PV power during the day. Biggest single difference over the past few weeks has been changing from using the full size oven to using the small combination oven/grill/air fryer. The high overnight peaks are a couple of times when we've charged the car overnight.

House power.jpg (71.96 KiB) Viewed 1205 times

[nowty]

I had a panic attack so checked where it was all coming from and was relieved that only 250W was coming from the grid - most was from the 6kW Solis inverter and battery with a few hundred watts from the other PV system, lucky it is a "bright" day. The peaks are short lived - except when the same person decides to tumble dry the washing at the same time as dinner is being cooked in the evening

Nowty Towers and others on here seem to experience this similar "panic attack" syndrome caused by their other half's obsession with simultaneous domestic appliances.

The problem is, to us the logic is inherent, positive and negative power calculations are computed automatically depending on time of year, weather compensated, house loads and battery SOC.

Example,

In Winter,
You can't put everything on together so don't run the microwave to heat your milk whilst the kettle and toaster is on and try and run the toaster after the kettle's boiled.

"OK, got that"

In Summer
Don't worry stick it all on its sunny.

"But you said......!", yes but that was in winter.

"OK, got that everything on if sunny."

But then there is the time in Summer when its a bit overcast and you've got the EV charging in the background and SWMBO is running the washing machine. Suddenly, the kettle, toaster and microwave all go on together.

Nooooooooooo.

[Oldgreybeard]

My fix was to put together a pretty simple Home Assistant dashboard, with coloured segments on the dials. When the dials are green then it's generally OK to turn high power stuff on. My wife's getting to be very good at this, just checks the dashboard before deciding to turn on anything, other than when cooking. Even then she's very good at not turning lots of things on at once, so we don't go over the max the inverter plus PV can deliver.

[Tinbum]

Thankfully we have 3 phase and my wife is getting much better at doing things when the sun is shining. We have the odd blip every now and then but we are getting there.

[marshman]

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[MrPablo]

Excess load above the inverter capacity is something I've been wrestling with.
Most of the time my wife and I are pretty good, pausing the dishwasher to boil the kettle, etc, but I will admit I am a lazy efficient person.
I very recently set up some automation with Node Red and Home Assistant to turn off certain loads if grid import goes above 50w for 10s. After it drops back below 50w for 10s, the load comes back on.

Here's the kettle causing the dehumidifier to turn off automatically.


Not for everyone, but I'm a fan of making things as hands off as possible.

[Caesium]

Here's the kettle causing the dehumidifier to turn off automatically.


Not for everyone, but I'm a fan of making things as hands off as possible.

I like ideas like this but the more modern an appliance is, I find, the more likely it has its own "smarts" and simply doesn't come back on after being turned off/on at the plug with a smart plug. You need to physically go press an "on" button on my dehumidifier for example to get it going again

Do you have any workarounds for this (opening it up and bypassing the on switch probably not what I'm looking for ) or stick to more dumb dehumidifiers?