Batteries

[Joeboy]

Excellent we have the old lead vs li-on debate, seems like the old days.

I've had both forklift LA, pylontechs LIFEPO4 and re-used growatt LMCO with my own BMS.

There are no right or wrong answers, both have their pros and cons and it comes down to your system, where you store your batteries and how much maintenance your willing to put up with.

But I would steer clear of those ebay UPS type ones (same reasons as has been posted) unless they are exceptionally cheap which they are not. If you want LA for whatever reason then forklift cells are the recommended ones for regular cycling. But you need to be happy with sulphuric acid, explosive corrosive gasses, taking SG readings, regular distilled watering, doing EQ charges, ensuring no deep discharges or lingering at low SOC, long absorption charging times for the last 15%.

I don't miss any of that.

My personal faves in storage are hot water tanks and storage heaters. They can hoover up huge amounts of spare pv power. Also very impressed with the simplicity of a insulated/isolated concrete floor pour with heating pipes thru it for thermal mass storage. Always wondered just how many MWh's of solar generation can be stored in this fashion. Anyone fortunate enough to have such a system care to share figures?

For the faster reaction storage I am a fan of the lifepo4 Pylontechs for the fit and forget nature. I would like to grow my storage system with prismatic cells but when I looked into it there wasn't really much of a price advantage over the factory built Ptechs. I'd be open to any suggestions of how to diy more storage for less cost? My current pylontech stack oldest unit is 5 years old, now in year six, the whole stack registers as 94% soh so I am losing the traditional 1% pa as expected. I discharge the full 90% and they live in a cold garage with lots of airflow.

[billi]

There was a time when that was true. And people installed lead despite understanding the drawbacks purely on a £/kWh basis. But now the prices are much closer…

2022, My independent and non-commercial connected research across the World, still shows that simple good quality Lead Acid is still way better than the modern battery tech, especially with cost effectiveness in Price and Quality.

My friends that have experimented with Off Grid modern batteries, mostly LIFE PO4, have had serious issues with BMS. And these are systems that have been running/limping for over 9 years now, so i value their honest opinions.

Again, there was a time when this was true. 10 years ago there were LiFePO4 batteries sold with failure-prone BMSs. In fact you could buy good quality LiFePO4 batteries for cheap because they were hobbled by a failed BMS. But this no-longer the case. LiFePO4 batteries come with decade-long warranties and they are expected to still be working at full efficiency (but slightly reduced capacity) long after that.

Again , i want a battery as simple as possible and if something goes wrong , i would like to be able to handle it and secure the battery bamk and work on a recovery , and that is with 2 volt lead acid cells pretty easy , as they are just connected without any electonic things involved

To form a small 2.4 kWh one needs "The Pylontech battery has 15 cells in series, so 53.2V equates to 3.55V per cell" so what do you do if one cell fails ? How do you get the one, that failed cell out and is access easy without soldering around electronics ? Or can you just make an easy equalization charge ? Or just bring the the whole lot to the dump ?

[Joeboy]

Fair point, warranty is 7 years. So return to sender type thing in the first 7 years. Personally I intend in the fullness of time to break open my units ID the u/s prismatic cell packs and replace. Not a big deal. Slowly slowly catchy monkey.

Very little will go to the recycling. We are at the beginning of lifepo4 architecture whereas LA has deep history, I am looking forward to being a part of building the history of lifepo4, maintenance and ingenuity.

[nowty]

When you do your own BMS, you know how it all works and hangs together for easy maintenance, but never had a failure yet, some of the batteries must be 8 years old now and still no sign of any loss of capacity. I am in the process of writing up my reused growatt LMCO batteries to resurrect a redundant thread from St Elsewhere.

Re-used (mostly faulty growatt packs), BMS died but cells live on.


Bit ironic my battery balancers are sitting on my redundant gas boiler.

[Joeboy]

Nowty, the cabling running to your balancers looks just like upgrade hifi wire I brought in from Germany back in the day. Serious thick multistrand. I sometimes contemplate the worthiness of the pilot.light.

That's a hell of an impressive and neat set up youve got there. Interested for a guesstimate. If it all went tits up and you had to fall back on your off grid pv plus your offgrid battery set up how long could you run the house for? How longs a piece of string question.i know...

I am fascinated by the idea that system expansion plus efficiency measures that we all do have a symbiotic outcome for us as end users and our runtime once we exit the grid. A very small part of my personality appears to be a Prepper. Quite surprised at that!

[nowty]

Nowty, the cabling running to your balancers looks just like upgrade hifi wire I brought in from Germany back in the day. Serious thick multistrand. I sometimes contemplate the worthiness of the pilot.light.

Your right its 4mm² HiFi cable from ebay, cheapest stuff I could find, but I had to cut the end down a bit to get them into the holes in the balancing circuit boards.

No pilot light in the gas boiler and its still switched off.

How long to run the house for Off Grid ?, at this time of year, probably until about October if I'm careful.
Saying that this weekend could be a struggle, 3 crappy consecutive days coming up here in the south.
But 2 good days first so everything will be full before the famine.

[Joeboy]

Nowty, the cabling running to your balancers looks just like upgrade hifi wire I brought in from Germany back in the day. Serious thick multistrand. I sometimes contemplate the worthiness of the pilot.light.

Your right its 4mm² HiFi cable from ebay, cheapest stuff I could find, but I had to cut the end down a bit to get them into the holes in the balancing circuit boards.

No pilot light in the gas boiler and its still switched off.

How long to run the house for Off Grid ?, at this time of year, probably until about October if I'm careful.
Saying that this weekend could be a struggle, 3 crappy consecutive days coming up here in the south.
But 2 good days first so everything will be full before the famine.

Pretty sure we also have no pilot light either as the thousandths of cubic mtr on the meter have not moved in quite a while.
I reckon outside of the Feb to Oct window we could probably eke it out to four/five days on the batteries with low end of year irradiation incoming from the Victron. If we had a full EV at point of grid failure we could likely to go to a month with that stored power and the WS running. I think its a part of aging but this has become important to me.

[Joeboy]

OP, Apologies for the seeming hijack, battery related though!

Ah = kWh ÷ V × 1,000.
My current stack is 14.4kWh @ 48v so 300Ah before any degradation or operational parameters set on it. Each unit of 6 cost me around £700 so £4,200/300Ah is £14 per Ah.
Today prices are around £800 per unit so £4,800/300Ah is £16 per Ah.
These sealed units on Ebay come in at £490 for a set of 8 at 102Ah. The fast charge rate is limited to 40A and DOD is 80% but other than that they look as if they could slip into my system.
https://www.ebay.co.uk/itm/265662358313 ... SwHUdiZycF
£490/102Ah is £4.80 per Ah
That’s one heck of a price difference. There are cabling and isolator costs along with support frame build costs yet it appears to me that the BMS is already installed in the Pylontechs and that these batteries could be slipped in to one side. Essentially inline between the Pylontech stack and the off grid inverter, thoughts?

[nowty]

That’s one heck of a price difference. There are cabling and isolator costs along with support frame build costs yet it appears to me that the BMS is already installed in the Pylontechs and that these batteries could be slipped in to one side. Essentially inline between the Pylontech stack and the off grid inverter, thoughts?

You've used the 8 pack price but you need 15 cells to make up a Pylontech equivalent in terms of voltage, so I make it about £900 for a 5kWh pack (similar to two of your Pylontech US2000).

Cheaper but not as cheap as you think and once you add the cell balancers, and all the faff, your probably better off with more Pylontechs.

[Joeboy]

That’s one heck of a price difference. There are cabling and isolator costs along with support frame build costs yet it appears to me that the BMS is already installed in the Pylontechs and that these batteries could be slipped in to one side. Essentially inline between the Pylontech stack and the off grid inverter, thoughts?

You've used the 8 pack price but you need 15 cells to make up a Pylontech equivalent in terms of voltage, so I make it about £900 for a 5kWh pack (similar to two of your Pylontech US2000).

Cheaper but not as cheap as you think and once you add the cell balancers, and all the faff, your probably better off with more Pylontechs.

Doh, and that space was just looking so inviting too!