Solar PV battery options

I sent an email to Solis and explained the 15 mins issue with the battery at 100a and then 70a and they basically confirmed that is the case:

Maybe newer FW has the improved values it seems.

I suppose when it comes to night charging it won't really matter since I will charge slowly anyway.

Seems to me this is a pretty big limitation that needs to be mentioned in the spec sheet of the inverter.

Can you "cheat it"? Set the max-discharge rate to say 90A and does it avoid going into that reduction loop? You might want a constant 90A over a 100A and then that reduced rate.

Just a thought.....

Yes @Jonathan that's how I have read it, it will stay at 70a indefinitely if it runs at 100a for over 15 mins. If it the load is then under 60a for at least 25 mins, then after that 25 mins it is allowed to go to 100a again and repeat.

Funny how I haven't noticed that in over a year with the system but also shows I am not pushing 100a on a regular basis.

I wonder if the same applies when you're charging from the sun (or at night even - which I haven't done once), batteries are rated 50a so the 100a would only need 25a from the four which is 0.5C I guess.

I will have to go back and look at my data from the last year curious if it always happened.

Jaysus, don't be wishing for updated firmware. I'm on 3D0032 which apparently is the latest version. It's back to dumping 300W~ constantly from the battery. I've also got an issue where it flips from import to export constantly once generation dies down. That may be unrelated but it's worse on this firmware than A10032 which I was on. I asked them to roll it back.

I wouldn't be too impressed with them changing it without telling me. If it's a security/safety issue they need to let people know.

@SD_DRACULA I can send commands to it on the latest version.

That rightly puts me off buying a Solis hybrid inverter I have to say :-(

The new 6G (125A) version can not be ordered by wholesalers until January, meaning we can't physically get one until May / June, or so I am told.

I highly doubt they will have anything open for us on the automation side of things on the 6G and yeah it would be worth getting clarity on that 125A is it only for 15 mins?

Seems like a real 125A might only be possible with 2x sofars

Yes same here, 3.2kW in or out, so 63A out of my ME3000SP

Well if there's one thing I realized is that unless I charge my car from the battery the 100a thing is not really an issue.

Even for charging the batteries from PV, as the generation starts slowly in the morning, it charges the batteries slowly too, by the time the gen is at 5kwh or more, the batteries are at 80% which lowers the charging to 80a anyway

I think no one here will put on dish washer/washing machine/dryer/oven & hob all at the same time and it wouldn't matter as that will push past 100a easily.

I can see the night charging being a problem for people who have that stupid smart rate time of 2 hours where you would want to charge as much as possible in those 2 hours. But with d/n I don't care, will charge at 50a or less over several hours during the night which is better for batteries anyway

100% I feel shafted with the inverter as that's just false advertising and legally speaking probably something there too.

But in practice I'm not seeing a huge draw from grid because of this, certainly not during cooking but then again induction is quite efficient and I don't see it a constant draw from hob/oven, it seems to go up and down so maybe that's why? Certainly cook for more than 15mins

A joke that it detects the correct 200a charge/discharge values

I think it rarely happened that I drained the whole battery (20kwh dyness) during the good weather, not even when we had a dull day in between it didn't drain to empty (15%) - not for lack of trying

Most days batteries would be around 50% after the night so maybe when I will be charging from grid I won't even get to use the night charge. Will take some getting used to with my automation since no point charging to 100% and then immediately send to grid once PV picks up in the morning, probably charge to 80% or similar

That's very true now in August but come November December and January I think we will need every bit of our 20kw batteries. Granted some days will be 4/5kwh generated but there will be many 1kw days too

how much load shifting can I forecast with a 5 or 10kw battery per annum?

Thanks graememk that is essentially where i arrived at also. What sort of self consumption are people who do not have battery?

I am of the same mind as yourself when you look at cold hard sums wrt to not getting a battery. Can you also save on the inverter if you don't need a hybrid one if you don't go for a battery?

My thinking is to get the hybrid inverter regardless. That way if batteries settle down in price in due course I can buy, or DIY, and capitalise on any technology advancement. I am curious to have my numbers challenged though. Perhaps there is a usage behaviour, a hack, or calculation I have not considered.

You need to factor in that you're only.sllowed 200e pa tax free from fit and must treat anything above that as income. This might make your non battery payback period a bit worse.

Yeah, like SD mentions above, it's a hard one to call.

The battery math isn't as compelling as it was 12 months ago. However, the rates you use when doing the calculations flavors the outcome a lot depending on what you are getting in FIT and day/night rates etc. Forgetting the solar/FIT aspect for a while and looking at my own "grid to battery" figures for the year, this is basically the number of units I "load shifted" from night -> day rate. I have a ~9kwhr battery

Like most things in solar, it generally follows a sine wave during the year. Assuming sept, Oct, Nov, Dec map to Apr, March, Feb, Jan (which is a reasonable guess). So, I'll probably import from grid -> battery approx. 1920 units for the year.

Using Energia's current €0.08 night and €0.29 day....and applying losses of 10% (my GivEnery battery historically does 9%) that puts it as.

Cost to charge battery = €0.08 x 1920 = €153.52

Value of electricity at day rate = €0.29 * (1920 * 0.90) = €501

Ergo savings from the battery ~ €350/year by using it to store night rate leccie and use it at day rate. This is ignoring the storing of solar generated energy which you can get FIT for also. I import from the grid in summer as I have an algorithm which looks at met.ie and decides if tomorrow will be bad weather wise and sets the charging levels.

One massive thing that I think the battery does for you though (esp. if you're a heavy user), is that it softens the blow of the bills in winter when solar is pants and the bills are high. The battery saves ~€50/month in the dark months. So yeah, while FIT will give you money in Jun/July that you would get by not having a battery, that money is long spent out of my wallet when Jan comes about. Battery means that those Christmas bills are about €100 lower at that time of year. That's useful to me - but appreciate others may not value it as much

Overall, it's a question of what you value more. I think you will get a quicker payback without a battery, but overall I think you have (slightly) more flexibility and will generate more over the long run with one....

Aside: I should say, your consumption profile too is super important. I'm sort of unique as with the mining and the fact that my automation turns on/off miners when I have spare solar, I can use all the space in the batteries or create space as needed if I know it's sunny.

I'm was in the same boat and torn on adding a battery. But I'm gonna get one. Biggest non-cost reason (and I'm cost focussed generally) is solar is supposed to help our house, IE convenience to use what we want when we want it. But without a battery I will obsesssssss about self-consumption % and drive my family bonkers. No one in our house (bar me) is gonna only turn on 1 heavy electrical device at a time - meaning we're importing. And can I expect them to?? I'd like them too - but do we want to double the time needed to cook dinner :)

Just looking at making grub, all our kitchens are energy hunger. And only the dishwasher can easily load shift.

Another bigger for me is I feel energy prices are gonna be nuts for years (just IMO). So battery and night rate helps dampen that.

@bullit_dodger did suggest even a small battery to me months ago when getting our quotes and that I wouldn't be ar3ed running around the house turning stuff on and off. I dismissed that. But have come around since :) Just need to find one that won't break the bank now!!