We're Gonna Need a Bigger Solar Battery...

A look at the AERL battery storage and other solar inverter stuff in the last week.

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#ElectronicsCreators #Solar #Battery

[pcfreak]

Have you checked out DCS batteries? They have some great stuff that always achieves the promised capacity! 😅

[mikesradiorepair]

Another thing to consider is those bad charging days (cloudy). Even if your battery system is marginally big enough now, when you have a bad solar day the next day you run out of stored power. If you add 2 more batteries you will have energy stored from a previous day that can be used on the cloudy / rainy days.

[csongor]

"Barely lasts all night" might be worth it to check how to reduce your idle power. Maybe only use your heat pump water heater during the day? Seems like you have got a 500w-1000w idle power draw which is crazy. Im sure you can get it down if its not all because of heating. Maybe reduce temperature setpoint during the night? Just sharing some of my experiences.

[leokimvideo]

Be careful, my neighbour has gone through 2 batteries since 2019. One failure was related to the battery going off line and became a warranty replacement, the next battery just went wonky after a few years. Stopped holding a respectable charge. The worst aspect is considering the absolute crap buyback price of electricity now your investment in a battery is never going to pay off. Thats the simple math your up against.

[ekolekol]

Use voltage, not SOC on lfp...charge to ~3.45v per cell, discharge to ~3.0v - that should give you >90% without degradation. Andy (Offgrid garage) has a video on this.

[eliotmansfield]

what you are paying for 5kw batteries i was paying for 3kw batteries a couple of years ago.
Definitely another two without doubt. Would be tempted to fill the rack because it’s less heat and load across the pack.

[iamblaineful]

I've built 4 DIY 48v server rack battery modules. They use a JK BMS and talk to my inverter and each other just fine. They are 15Kwh each for $2200 USD, 60Kwh for the house. I was following Andy Off-grid garage and thought that made the most sense when looking into battery systems that provided the most density for the $$.

[kensmith]

I think more batteries makes the most sense in the winter. That is when you pull your existing ones down a fair way over night. In the summer the nights are shorter.

[sarahjrandomnumbers]

Pretty much exactly what happened when I installed mine. Started off with a 5kWh battery, but found it didn't cover me. Ended up upgrading to 15kWh.

But don't underestimate how much shifting your power usage can help. But once you've shifted and lowered your idle usage, keep upgrading the battery until the 80% thing isn't an issue anymore. Like my battery gets to 40%~.

Also, I wouldn't worry too much about the 80% DoD thing, it's mostly comes from misunderstanding the cell specs and how they're used in a home battery setup. Like Peter said, these cells are used in the automotive world, which is where the 80% DoD is important because they're charged and discharged very close to their maximum specs.

So unless you're pulling 100A out of every cell every day and charging it at 100A, the thing that will kill these cells in a home environment is shelf life. But if you get enough battery where you're never hitting 80% DoD, it's a moot point.

By all means, follow Peter's advice about 80%, because he isn't wrong, that is what the battery spec says, but it's a little important to understand the context and reasoning behind it, and how that relates to these cells in a home environment. As the spec most likely says 80% DoD at 1C, which you'll never do.

Personally my minimum SoC setting is 0%, but my cell voltages stay between 3v and 3.5v, and that's my 0-100%SoC, but the spec calls for 2.5v to 3.65v, so there's already a margin accounted for. So my battery is probably around the 90%DoD level, if fully charge/discharged.

[oznimm]

Thx for sharing ur journey Dave. You might want to hold off getting more batteries until you have a better idea over a 12mo period just how much electricity you're buying in order to work out if there will be a payback at all. Winter with lots of rain/clouds and shorter days probably is going to be the worst of it.

I'm in WA and live on the outskirts of Perth and we do a ton of driving and I wanted to be able to power everything (including our driving) from solar if we could. After lots of calcs based on what we used for the house and estimates for the cars I was surprised the best thing was just to provision as much solar as possible and use it while generating and go with a smaller battery. FYI I've had various solar on the house since 2009 and to handle the above we upgraded to 16kw of panels, 10kw inverters, and 10kWh of battery. That pretty much works for us the whole year round and even in winter can cover 100% of our usage with the exception of extended days of rain/clounds. But even with bad weather i'm impressed with so many panels you still get generation enough for our house usage - maybe not enough to really cover EV usage though. I keep wanting to max out my batteries too btw, up to 30kWh but I don't think there's a financial justification :) Well unless WA adopts something where I can sell the excess... I do allow my batteries to 100% discharge though, yes happens a bit in winter but for a lot of the year it never happens since long days etc...

[freibuis]

each battery pack has a bms.. I swear the installer said you where using `can bus` so you can read each pack individually

[ausnorman]

I've got 10kwh with 2x LYNX Goodwe batteries... thought the same with my house hold lol. Adding another 10kwh soon and looking at heat pump hot water also to lessen the overnight power draw.

[RayJohnson]

what you need to look at is not just how much is used but how much can be stored long term from summer and autumn for the winter usage. so 30kwh+ is needed

[WizardTim]

I think you should investigate what "20%" actually is with a multimeter. A lot of applications that use LFP hide the top few and the bottom few percent from the user to force a shallower depth of discharge. You might find the modules report 0% between 3.0 and 3.2 V instead of 2.5 V. So you 20% might actually be 25%.

[rfekztjpkrpd]

Did you look at the financia side of it? AFAIK the break even point is moving to the future with more batteries.
Also there are two potential optimisation points:
* time optimisation (use excess power instead of storing it)
* increase depth of discharge to 90 or 95%
(Huawei LUNA200 S0 comes with 100-5% default and is actually advertised for 100% depth of discharge.

If you have 15kwh, moving from 80 to 90% depth of discharge will give you an additional 1.5kwh for "free".

[christopherguy]

Go for the full 6 battery bank. You'll be able to keep the batteries longer as they won't be used as hard.

[jspanga]

I wouldn't.. we've got 10kw of solar + 13kWh of batteries + EV as well, and seeing similar graphs. Battery is only really meant to supplement when you're not able to use solar - 70% self sufficiency and 70% self consumption is perfectly fine and more batteries will take longer to pay for themselves

[toleranz]

More Betteries 😂🤣 yeah I would nerd the crap out of the system, monitor the power usage of the house (after each breaker) to find usage patterns that I could optimize. More storage capacity is always better so you can offset those cloudy days or usage peeks.
A friend of mine had renovated his house up to nearly passive standard in 2020/21 and installed solar + modern heat pump for heating/aircon + hot water. His initial system was 30kW solar + 40kW/h capacity battery which he is doubling in the fall. This is in Northern Germany for a 350m2 house + 150m2 office space. Because of the mixed usage and location the installed solar wasn’t enough to cover the power needed over the day (especially in the time between october and march and the installed battery capacity couldn’t offset the days of low pv production. The local municipality and a farming cooperative had recently built 3 wind turbines which people in the community could buy shares of and have locally produced grid power for roughly 1/3 of the normal price - which he does too.

[calholli]

I think it would also give you longer battery life across the board... Since you wouldn't be discharging down to 29% everyday. Less cycling swings should likely give you more cycles. I doubt you would ever get below 60% again with 2 more packs.

[MLeoDaalder]

Is the current clamp for the essential load inverted? Aside from that, it might be a fun little project to convert a cheap current clamp meter without data logging to something you can plug into a RaspberryPI or other microcontroller with storage/connectivity.