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Solar PV battery options

DrPhilG

I figured it might be an idea to have a specific thread for this topic. Lots of us have home solar with batteries attached, usually GivEnergy, Pylontech etc usually in 2.4/4.8kWh levels.

Given the cost of batteries and the pending feed in tariff, its debatable whether these batteries will continue to make financial sense, (or if they ever did).

However there is essentially a separate market for the enthusiasts, to have large scale battery storage, 10kWh and beyond.

I thought it would be useful to have a thread for this area specifically, as it is essentially a different topic from the general Solar quotes thread.

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unkel

DrPhilG wrote: »

But you didn't just criticise my plans, you misunderstood them, jumped to conclusions

Yeah your digs there about me having to get with the program didn't help. It was you who talked about a 9kWh setup and then all of a sudden 30kWh. As if you can just change your battery or add to it. You can't. I had to force myself not to use a rolleyes there but instead use a more civil answer

For someone using this forum as a vehicle for learning and for extracting help and advice from others, you should really tone down your attitude or there won't be many people left willing to help you...

DrPhilG

For God sake man will you reel in the aggression for a second and realise that you're wrong here?

unkel wrote: »

Yeah your digs there about me having to get with the program didn't help.

If you're referring to the "pay attention" comment, that was clearly meant in humour. I thought the "tut tut young man" would have made that clear. However if that's what has kicked this off, I do apologise. The comment was meant in jest as I thought you had skimmed and misunderstood what I was talking about.

unkel wrote: »

It was you who talked about a 9kWh setup and then all of a sudden 30kWh.

No, I didn't. I made it crystal clear that I was looking at 9kWh initially, then adding another battery for about 15kWh usable, and later increasing to "20 to 30kWh". It is perfectly possible to add more Leaf cells to an existing DIY battery provided that they are the same chemistry and added in the correct numbers. I never at any point mentioned adding a 30kWh pack or mixing different types of battery.

unkel wrote: »

you should really tone down your attitude or there won't be many people left willing to help you...

What attitude? I have not been aggressive at all in this exchange. You have, and I have no idea why you're flying off the handle so much. The only attitude I've shown is in response to your belligerent attacks.

1 - You snidely accused my friend of overcharging me by ignoring the inclusion of the BMS in the price, and also (falsely imo) claiming that you can get a 24kWh pack for €1500.

2 - you then mocked me for wanting to add a 30kWh pack and mixing batteries, (which I had never suggested doing) and told me to "stop kidding myself".

I've tried repeatedly to steer this back on topic, but you've taken offence over something and are determined to be aggressive and put me in my place.

If so, consider me suitably berated. Now can we get back on topic?

DrPhilG

@samdeluxjones - how long did you wait for a response from China?

I've dropped them an email looking for some prices and some more info on compatability with my current system.

Their website says 24 hours so I'll report back once I hear.

samdeluxjones

DrPhilG wrote: »

@samdeluxjones - how long did you wait for a response from China?

I've dropped them an email looking for some prices and some more info on compatability with my current system.

Their website says 24 hours so I'll report back once I hear.

Almost instant on WhatsApp, they ask for your number on the inquiry page.

Scarlett's number is on the invoice you can WhatsApp her directly.Attachment not found.

samdeluxjones

Attachment not found.

No idea how legit this is with EU standards.

They can't give me a straight answer on import duty or getting caught for VAT on customs clearance.

championc

DrPhilG wrote: »

I know it might be a bit cheaper going the Leaf cell route, but it's also a lot more hands on and potentially a fire risk if its not done right.

For starters, LiFePO4's are one of the safest compositions of battery. If a case ruptured in any way, you don't have the corrosive acid or Lead-Acid's nor the explosive possibilities of 18650's

But you have to understand where the danger comes from - which is either short circuits, inadequately sized wires and busbars or heat due to loose joints.

Therefore, I would trust my DIY POWERWALL every day of the week over a packaged up cell, where you have no knowledge of how well any connections were made, how adequate the cables used are for the charge and discharge, and how well the pack has been assembled.

With a DIY POWERWALL, you can overspec components to your hearts content. I bought a 100A BMS and I use 10m² DC cable. Both may well be overkill, but I felt worth the extra to be well within the limits of what I used.

I have also been very specific to recommend the CALB Cells rather than any of the Littokala cells which have inadequate (IMO) positive and negative terminals on each cell

graememk

samdeluxjones wrote: »

Attachment not found.

No idea how legit this is with EU standards.

They can't give me a straight answer on import duty or getting caught for VAT on customs clearance.

It will be liable for 23% vat, not sure about import duties.

A 100kg box doesn't just slip past.

DrPhilG

graememk wrote: »

It will be liable for 23% vat, not sure about import duties.

A 100kg box doesn't just slip past.

Did you get the same cells as championc? Am I right in thinking that the prices you paid included import duties?

DrPhilG

championc wrote: »

For starters, LiFePO4's are one of the safest compositions of battery. If a case ruptured in any way, you don't have the corrosive acid or Lead-Acid's nor the explosive possibilities of 18650's

Thanks. This is the main thing turning me off the idea of a Leaf cell battery. With the best will in the world and a good BMS etc, there still remains the possibility of something going belly up and worst case scenario would be a serious fire/explosion.

LiFePo4 worse case scenario is presumably that it just stops working and you have a very expensive paperweight that you can't exactly take back to the shop. But that risk exists with any of these options.

championc wrote: »

I have also been very specific to recommend the CALB Cells rather than any of the Littokala cells which have inadequate (IMO) positive and negative terminals on each cell

Thanks again, I'll have another look at the stuff you have linked.

The BSL-battery site looked promising as a nicely packaged plug and play option, but the reality is that it's still a cheap Chinese battery shipped from the other side of the world with realistically no warranty or comeback.

Plus as samdeluxjones is now finding out, they are very vague on import duty, which means that the €2k estimate for a 10kWh battery would very quickly become €2.5k, compared to the €1.4k that you've paid including import.

graememk

DrPhilG wrote: »

Did you get the same cells as championc? Am I right in thinking that the prices you paid included import duties?

Yep they come via poland, and cleared there,

DrPhilG

graememk wrote: »

Yep they come via poland, and cleared there,

It's funny, being a mile from the border I'm used to getting stuff shipped to NI and collecting it there as its cheaper for postage.

Likely the complete opposite now due to Brexit.

graememk

For the Solis hybrid inverters, in the manual, look around pages 38-40, it gives all the custom settings for batteries on it.

The float is for lead acids, - ie you dont want to be doing that with the LiFePo4 - so current + time would be set to 0.

My experience is with the sofar, but that has a lot of similar settings, Mx charging voltage, minimum voltage, etc.

The last 2 "full and empty voltage" in the sofar is what is uses to calculate the SOC from the resting voltage, after an hour of sitting idle.
The calculation inbetween is sort of a dead reckoning. ie you tell it you have a 10kwh battery, it takes out 5kw, so it must be at 50%

If then you discharge to your minimum SOC... or hit a voltage limit. It goes into standby, after an hour it will read the voltage and then recalculate the SOC. The Me3000 calculates that more or less on a line from the empty voltage to the full voltage.

The curve for lifepo4 is very flat with 2 "flicks" at each end. So I've ignored them and with a lot of trial and error have a few different settings.
I can have the high % accurate, or the lower range accurate.

High comes at a cost of accuracy in the mid range(40-60%)- it tends to recalculate high

low end accuracy in the 30-50% which pushes the top end to be inaccurate - recalculates low

DrPhilG

Great details, thanks.

The Sofar is 3kw isn't it?

I'm planning to eventually increase to 12.5kWp across 2 inverters. Was looking at another Solis partly as its what I'm familiar with and partly to ensure that the 2 of them talk to each other for the purpose of export limitation.

championc

DrPhilG wrote: »

Thanks. This is the main thing turning me off the idea of a Leaf cell battery. With the best will in the world and a good BMS etc, there still remains the possibility of something going belly up and worst case scenario would be a serious fire/explosion.

LiFePo4 worse case scenario is presumably that it just stops working and you have a very expensive paperweight that you can't exactly take back to the shop. But that risk exists with any of these options.

I expect the leaf cells to de safe enough, but while voltages may look ok, the capacity might be degraded (and which is well documented for Leaf Gen 1's).

I assume that the Leaf setup needs a special BMS since the cells are 7.6v in 7s configuration. With the AliExpress cells, you simply buy a standard off the shelf 15s or 16s LiFePO4 BMS. The only thing I had to configure was the Capacity and the Low Temp Cutoff level. I bought the HEYO, but most buy the DALY.

Once the BMS is correctly configured and working, that will stop damage to the cells. The only thing, imo, that will leave you with a paperweight is simply a dud cell.

Just to clarify, I knew nothing about Solar this time 2 years ago. I know how to use a multimeter, spanners and a drill. Remember, the voltage is still only 48v DC, so it's all quite safe. Sometimes being inexperienced makes you pay more attention to what you are doing.

championc

For those seeing this thread for the first time, here are the AliExpress "CALB 200A LiFePO4" Cells -

This is how they would be connected to a Solis (or any other) inverter, and here is how the BMS is wired. This diagram is made up from a photograph of my ACTUAL Batteries, in place (you can see the tops of the row of Lead-Acid's below them). I made a frams for the Lead-Acids with Unistrut

[/QUOTE]

€ 1.389,00 30%OFF | NEW 16PCS CALB 3.2v 200Ah LiFePO4 Rechargeable Battery brand new 200AH 24V 48V 200AH Lithium iron Phosphate Packs Solar Battery
https://a.aliexpress.com/_mtLHTeb

sebdavis

championc wrote: »

For those seeing this thread for the first time, here are the AliExpress "CALB 200A LiFePO4" Cells -

This is how they would be connected to a Solis (or any other) inverter, and here is how the BMS is wired. This diagram is made up from a photograph of my ACTUAL Batteries, in place (you can see the tops of the row of Lead-Acid's below them). I made a frams for the Lead-Acids with Unistrut

€ 1.389,00 30%OFF | NEW 16PCS CALB 3.2v 200Ah LiFePO4 Rechargeable Battery brand new 200AH 24V 48V 200AH Lithium iron Phosphate Packs Solar Battery
https://a.aliexpress.com/_mtLHTeb

Which provides 10kWh?

DrPhilG

championc wrote: »

With the AliExpress cells, you simply buy a standard off the shelf 15s or 16s LiFePO4 BMS. The only thing I had to configure was the Capacity and the Low Temp Cutoff level. I bought the HEYO, but most buy the DALY.

So the inbuilt BMS of the inverter isn't sufficient?
The HEYO isn't that much more pricey than the DALY anyway.

Ps I notice there's a discount voucher for €17 off a single pack, and €51 off if buying 2.

Think I'd stay at 1 for now though. Would be different if I stood to save a lot on shipping but the shipping cost is inclusive anyway.

championc

sebdavis wrote: »

Which provides 10kWh?

3.2v x 16 x 200A = 10240w

championc

DrPhilG wrote: »

So the inbuilt BMS of the inverter isn't sufficient?

There is NO inbuilt BMS in any inverter. The Pylontech sends the details to the Inverter over the comms cable link. If this cable is disconnected or miswired, it simply will not work

graememk

DrPhilG wrote: »

So the inbuilt BMS of the inverter isn't sufficient?
The HEYO isn't that much more pricey than the DALY anyway.

Ps I notice there's a discount voucher for €17 off a single pack, and €51 off if buying 2.

Think I'd stay at 1 for now though. Would be different if I stood to save a lot on shipping but the shipping cost is inclusive anyway.

Inverter cant keep the pack balanced.

Advantage of the Heyo is the low temp cutoff and individual cell monitoring.

I'm currently using just a passive balancer https://www.aliexpress.com/item/1005001356613723.html?spm=a2g0s.9042311.0.0.65fe4c4dretD5X

I check each cell with a multimeter every so often too just to be sure,

With all BMS's make sure you have it wired up correctly, 1 wrong wire can fry it.

Running the math, and knowing pylontech is a 15S (15 cells in series)

a 2.4kwh battery uses 50ah cells.

The above cells are 200ah.

A charge/discharge rate of 1C on a 50 ah battery is 50Amps
so the pylon tech is limited at 0.5 c on the charge/discharge.

I think on the 5kw inverters they can pull 5kw from the batteries.
with a 16S, 5kw, is 97 amps from the battery, 16mm2 cable will be the minimum.

so on a 200ah pack, that is still only 0.5 c.

a Plus with the bare cells, you could drop in another pack in parallel without any complications, just a change in settings.

DrPhilG

Is there a spec/model for the Heyo, to remain future proof in the event of adding more batteries?

I'm leaning towards a single pack for now but if all goes well I'll definitely go for 2 packs and perhaps 3.

DrPhilG

championc wrote: »

There is NO inbuilt BMS in any inverter. The Pylontech sends the details to the Inverter over the comms cable link. If this cable is disconnected or miswired, it simply will not work

Ah, OK. Solis advertise it as having an inbuilt BMS but I think they're taking a bit of artistic license with the term...

unkel

championc wrote: »

There is NO inbuilt BMS in any inverter.

I wouldn't say that now. An inverter should cover every single aspect that a BMS covers except just the one thing: cell balancing

championc

DrPhilG wrote: »

Is there a spec/model for the Heyo, to remain future proof in the event of adding more batteries?

I'm leaning towards a single pack for now but if all goes well I'll definitely go for 2 packs and perhaps 3.

You should be looking for a "16s LiFePO4 BMS 100A". You would need one per string of 16, although you could wire 2 cells in parallel, staying all in one string, (so making each cell 3.2v x 400A), but the BMS would have no control over the two individual cells since it would see them as one cell.

I would hope, over time, that certainly Sofar will bring out firmware specifically targeted at LiFePO4's, and most specifically to prevent charging once it's sensor sees the temperature at 0°, in addition to the charging and discharging curve of LiFePO4 being so different to Lead-Acid.

sebdavis

SO have we all agreed that we buy in the batteries and then pay @championc to install them for us? :-)

championc

sebdavis wrote: »

SO have we all agreed that we buy in the batteries and then pay @championc to install them for us? :-)

I'm more than happy to advise you all, right through your installation process.

Before you do anything, make sure you have a multimeter. It's the most important tool that you will use, as you validate everything as you go along.

The most time consuming part was to extend the cables of the BMS. Watch out for the shrink tubing in Lidl. You can twist join a core of Cat5 onto the BMS lead and then use a heat gun or similar to shrink the tube on the joint.

DrPhilG

championc wrote: »

I'm more than happy to advise you all, right through your installation process.

You may live to regret that lol.

A question regarding the inverter. If going to a 2 inverter setup, is it better that they're the same type? With regards to export limitation etc.

Second question, with an inverter like the Solis hybrid that I have, will the batteries always be on the DC side of the conversion? Even if I change to the LiFePo4 ones that you use?

championc

DrPhilG wrote: »

A question regarding the inverter. If going to a 2 inverter setup, is it better that they're the same type? With regards to export limitation etc.

What is your maximum simultaneous load, both now and in the future ? That should dictate or match your planned strategy. Suppose you wanted to charge the car at 6kw at night, then that should be your target model. That would then rule out the ME3000. Mind you, if you had two sets of batteries, you could have two ME3000's. We already had the discussion on the other thread how PV inverters might / would work side by side

DrPhilG wrote: »

Second question, with an inverter like the Solis hybrid that I have, will the batteries always be on the DC side of the conversion? Even if I change to the LiFePo4 ones that you use?

The batteries ALWAYS connect to a specific DC port on an Inverter. Battery power is always DC. The main difference with a Hybrid vs standalone is that the Hybrid keeps the generated DC from the panels and puts it straight into the batteries. But as we we'll know, that is not measurable.

I have both a Sofar PV inverter and the ME3000. The menus and displays are very clear.

Deagol

championc wrote: »

Remember, the voltage is still only 48v DC, so it's all quite safe. Sometimes being inexperienced makes you pay more attention to what you are doing.

Just would like to clarify your point on this in case some DIY people don't get it:

Voltage doesn't kill, current does. 48vdc can be extremely hazardous, especially at the currents the solar batteries are at. If you get unlucky and contact both - and + someone will find you flat on your back and ready for a box.

Plus, if you shorted out the +/- terminals with something metal, say a screwdriver, you will turn a piece of solid metal into a gas that takes up 1000x the volume in a few milliseconds. This will have the end effect of possibly throwing you into the nearest solid object - be that a wall where you might get away with a few bruises or something sharp that will end your worries about energy forever!

Sorry to be a downer but always worry me when I see people assuming lower voltage equipment is safer than higher.

championc

You are spot on Deagol.

The other thing which is important is DC Disconnects MUST be part of the setup. Before working on then, they should ALWAYS be isolated.

The one thing about the AliExpress cells is that the positive and negative poles are well spaced, so there is no real reason for error, so long as you take your time.