On-grid domestic battery storage

Solarchaser

I decided to mix my batteries up a couple of days ago.
With the 2 lux, not acting in parallel(😐), i was having 4 sitting at 100% and 4 at around 50%.

I have 3 x2017, 4x 2018 and 1x2019 batteries, so i decided to mix them in.

I used the 2x 2018 batteries i bought new (240 cycles now) as the controlling batteries (and positive) as they were known quantities.
The other 2x 2018 as the end batteries (and negative)
Put the brand new 2019 battery in with the likely most damaged 2017 battery, which was the one i got with my sofar, a year old (sofar was set quite badly when i bought it)
So each bank had 2 @ 50% and 2 @ 100%
Ive always balanced for an hour or so, but this time did it for 5 mins, and got bored and thought,... i wonder what will happen.

Within a day they were as balanced as ever.
Thats watching purely the flashing or constant lights right enough, so i guess they could still be 10% out, but the idea they would remain 50% adrift  is simply disproven.

mickyduck55

The sun is out and batteries fully charged by lunchtime l, still exported 7kW to the grid yesterday...

EVandPV

Starting to see the full benefit of PV + batteries + good weather.

 If only the shower didn't use a crazy 9kw !

majhaar

chamelion said:

EVandPV said:

Just scored a 3rd Pylon on fleabay for a fairly decent price. 
Still one left if anyone's interested ........ https
I've confirmed with the seller that the date stamp is 2017.

Installed! Pain free, all new and boxed, original - all working. 
He could only give 2 batteries for now - he'll deliver the 3rd tomorrow. 
Charged me 1800 all in - 400 inverter, 600 for each battery, 200 install. 3rd battery slightly more due to supply issues, but will still be 700 brand new. YMMV. contact me if you want contact details - they're happy to get more customers!

Sent you a PM for the details.
MJ

Exiled_Tyke

I've raised some of these issues before and someone else  (can't remember who) queried sudden power surges recently.  The graph is from this morning. The two things I don't understand are: 

1.  Why the sudden power drain just before the battery started charging this morning. And why did this not result in a sudden drop in battery capacity?
2. Why the sudden drop in battery capacity (around 10%) around 7am when there is no comparably power dip?

The BMS also seems to have some other quirks including: 

1. Occasionally allowing capacity to drop to 5% and then immediately recharging from the grid back to 10% 
2. Most of the time charging to 95% before stopping but occasionally going to 99% and then immediately draining. Strangely, yesterday it stopped charging at 88% for a while and then suddenly stepped up again. 
3. I've noticed with heavy appliances which switch in and out a lot (e.g. an iron),  when the appliance switches off repeatedly the battery stops recharging  from the PV.  It allows the appliance to drain the battery but when it stops it just sits dormant until the next power drain. 

I've a few theories that could explain these, although I'd be interested in others' views. But I'm most interested in: 

1. What similar experiences do others have, particularly with Solax? 
2. Why can't I find any published information about these quirks? If these are intended behaviours of the BMS which they may be, can't the information be made public? 

Coastalwatch

Progress claimed for a stable Potassium ion Battery storage with a new cathode material!

Scientists in China claim to have identified a special cathode material that could be utilized in more stable potassium-ion storage systems. According to the group, this new material could enable the development of storage systems able to retain 94% of their capacity after 2000 cycles, with 0.003% capacity fade per cycle.

https://www.pv-magazine.com/2020/03/24/a-stable-potassium-ion-storage-with-new-cathode-material/

joefizz

EVandPV said:

I'm finding that the new battery is about 4-5% behind the other, even after balancing, but apparently this is normal when introducing an additional battery and they should even out in time. 

IIRC it took mine about 10 days or so to come fully in to line. Some charging from the mains for the lower batteries (automatically done as it was again IIRC > 20% difference) and then just evened out organically when it got to <20% difference.

joefizz

EVandPV said:

Starting to see the full benefit of PV + batteries + good weather.

 If only the shower didn't use a crazy 9kw !

Any way you can run it just pumped and use the immersion for the water?

mickyduck55

joefizz said:

EVandPV said:

Starting to see the full benefit of PV + batteries + good weather.

 If only the shower didn't use a crazy 9kw !

Any way you can run it just pumped and use the immersion for the water?

I have the same issue with my 10kW shower.. so I installed a power shower and as suggested heat water using the immersion and try to only use the electric shower when I don't have hot water

EVandPV

joefizz said:

EVandPV said:

I'm finding that the new battery is about 4-5% behind the other, even after balancing, but apparently this is normal when introducing an additional battery and they should even out in time. 

IIRC it took mine about 10 days or so to come fully in to line. Some charging from the mains for the lower batteries (automatically done as it was again IIRC > 20% difference) and then just evened out organically when it got to <20% difference.

I've actually been having other issues with the new battery.

I've been monitoring them with the Batterview app and one morning I got up to find it was down to 0% SOC while the other 2 were still at 50%(ish).

The voltage was indicating that it should've been about the same SOC as the other 2.

So I contacted Pylontech and have been trying to correct the issue but I can't now get it to charge to more than 87% SOC or 51v even though the SOH is at 100% according to the Lux web portal.

I'm giving it one more grid charge tonight before sending it back.