Idiot's guide to a self build battery

[Joeboy]

Thanks guys,
There is a huge amount of info already in this thread. Need a bit of fusing and cables etc. I will do my idiot sheet when I get back home and take some photos of the proposed location and go from there.
£1,687- 15 of LF280K (A) batteries incl del, bus bars n bolts
£60.72 - 1 of 15s 5A balance board.
£60 framework and bolts
£20 DC-DC variable 20A buckboard (battery charger)
£38 Amp clamp (AC AND DC capable)
£60 Frankenstein breaker & 2 125A fuses
£26 2 of 2mtr lengths 25mm2 DC cable
£1,954 total

[Stinsy]

That's all great to read Nowty, looking forward to seeing it next week on our return. I'll be buying myself an ampclamp too as going this far it would me mad not to have that flow info readily to hand. If its OK I will ask you about the benefits if any of fusing each of the three banks of 5 batteries even though they are in series. Seems logical as fault within one battery will hopefully blow the fuses on each end of the 5 bank and not melt any other assets (cables)?

It seems strange to me that the max load the LF280's will see in normal operation is during charging. The discharge side is relatively low due to inverter restrictions. Again, I may be stating the obvious but it's all new to me as was the thought of the figure C yesterday as a handle on discharge.

It is generally external factors you are insuring against with a fuse. Your Pylontechs have inbuilt overcurrent/short-circuit protection but your new batteries don’t. Therefore a metal tool used negligently, or other mishap, could cause a short drawing thousands of amps. This would damage the batteries and could be unpleasant for nearby humans. A cheap fuse close to the battery pack would be a good precaution.

Sounds good to me, I will be seeking help on the fuse spec and positioning. I would like to be able to tag a fuse onto each end of each bank of 5 batteries, preferably straight onto the incoming and outgoing terminal then link all in series? I can't though can I? As the new bank is all in series. Do I instead fuse both ends of the entire15 bank and forget about protecting each bank of 5 as well? I don't want to install blocks to flow unless they serve a good purpose?

I thought this wee unit would be enough for my simple DIY needs?
https://www.ebay.co.uk/itm/393983757199 ... %7Ciid%3A1

You can do whatever you like!

However I’d put a fuse at each end of the pack.

[Joeboy]

It is generally external factors you are insuring against with a fuse. Your Pylontechs have inbuilt overcurrent/short-circuit protection but your new batteries don’t. Therefore a metal tool used negligently, or other mishap, could cause a short drawing thousands of amps. This would damage the batteries and could be unpleasant for nearby humans. A cheap fuse close to the battery pack would be a good precaution.

Sounds good to me, I will be seeking help on the fuse spec and positioning. I would like to be able to tag a fuse onto each end of each bank of 5 batteries, preferably straight onto the incoming and outgoing terminal then link all in series? I can't though can I? As the new bank is all in series. Do I instead fuse both ends of the entire15 bank and forget about protecting each bank of 5 as well? I don't want to install blocks to flow unless they serve a good purpose?

I thought this wee unit would be enough for my simple DIY needs?
https://www.ebay.co.uk/itm/393983757199 ... %7Ciid%3A1

You can do whatever you like!

Aye but it will end badly...

Just to add for posterity.
My current setup is 6 of Pylontech.us2000 2.4kWh batteries with a storage capacity of 50Ah each so 300Ah total. At the prices currently bandied about online (£1,500 per unit), I would need £9,000 to buy them again.

The set up I am installing as an add on will cost me around about £2,800 once I've paid landing duties and bought tools to do it properly. It's a 280Ah battery set. So that's £10 per Ah vs's the £30 per Ah demanded today.for the Pylontechs. Wow!

[Joeboy]

Message in from Royal Mail saying my package from Bimble will be delivered today (Frankenstein switch & fuses). Let excitement at a new project commence!

[Caesium]

Just to add for posterity.
My current setup is 6 of Pylontech.us2000 2.4kWh batteries with a storage capacity of 50Ah each so 300Ah total. At the prices currently bandied about online (£1,500 per unit), I would need £9,000 to buy them again.

The set up I am installing as an add on will cost me around about £2,800 once I've paid landing duties and bought tools to do it properly. It's a 280Ah battery set. So that's £10 per Ah vs's the £30 per Ah demanded today.for the Pylontechs. Wow!

If this build goes well I am considering selling off a few of my Pylontechs. They're at about 275 cycles so I wouldn't get anywhere £1500 for them, but considering I bought them for £800 apiece, I'd probably be happy to sell them on at around that. 3 at £800 would pay for this new build and leave me with more capacity than I started with! (and then inevitably order another 15 LF280Ks)

Would probably want to keep at least 2 or 3 though to benefit from its BMS doing the heavy lifting on charge/discharge currents for me. And you need at least 2 to get up to reasonable charge currents if I remember rightly.

A few of my parts have turned up as well. 3m of 25mm (incorrectly said 20mm before) of red/black interconnecting wire, a chunky DC isolator, and hopefully a MEGA FUSE!!!11 turns up today or tomorrow.

[Joeboy]

Just to add for posterity.
My current setup is 6 of Pylontech.us2000 2.4kWh batteries with a storage capacity of 50Ah each so 300Ah total. At the prices currently bandied about online (£1,500 per unit), I would need £9,000 to buy them again.

The set up I am installing as an add on will cost me around about £2,800 once I've paid landing duties and bought tools to do it properly. It's a 280Ah battery set. So that's £10 per Ah vs's the £30 per Ah demanded today.for the Pylontechs. Wow!

If this build goes well I am considering selling off a few of my Pylontechs. They're at about 275 cycles so I wouldn't get anywhere £1500 for them, but considering I bought them for £800 apiece, I'd probably be happy to sell them on at around that. 3 at £800 would pay for this new build and leave me with more capacity than I started with! (and then inevitably order another 15 LF280Ks)

Would probably want to keep at least 2 or 3 though to benefit from its BMS doing the heavy lifting on charge/discharge currents for me. And you need at least 2 to get up to reasonable charge currents if I remember rightly.

A few of my parts have turned up as well. 3m of 25mm (incorrectly said 20mm before) of red/black interconnecting wire, a chunky DC isolator, and hopefully a MEGA FUSE!!!11 turns up today or tomorrow.

Sounds like a plan, I'll keep the thread updated with arrival dates etc. Will likely start some small works on the project next week as I have a backboard to fit on the wall to flatten out the system mounting frame. Also the aluminium channel is on s/by at screwfix for collection next Monday. I look forward to seeing your progress Caesium.

This build will give me just under 28kWh battery storage. I will likely stop there as it puts me well into no Winter worrying territory for the charge running out. Free's up SWMBO from any timing windows to run white goods and also leaves a decent amount to put miles onto the EV. That's not to say that I don't find the idea of a further bank appealing!

The next stumbling block is the 3.8kWh charge limit to the batteries. In Winter on the 5 hour Octopus window that limits me to 19kWh into the stack. Will be interesting to see how it benefits us day to day.

[Caesium]

Oh wow, just in case I was ever interested in removing all the Pylons and going completely DIY, just discovered this: https://github.com/juamiso/PYLON_EMU

So basically pretend to be a Pylontech from a Python script so you can tell the inverter how much amps to charge/discharge at etc. Quite interesting just to see what information the BMS sends back to the inverter looking at that. Although there's a proviso in the README that it isn't tested with real hardware

Yes I've also considered the charge limit. My Luxpower will push about 3.6kW in maximum, and I'm also on a 5h Go Faster window. I think it's not a completely lost cause as it basically just gives me a buffer to use more on some days, then it could take a couple of nights to charge back up fully so long as I don't use quite so much the next day. Replacing the inverter sounds expensive, but probably something to bear in mind next time I move house, upgrade to a 5kW or better hybrid.

[Oldgreybeard]

Yes I've also considered the charge limit. My Luxpower will push about 3.6kW in maximum, and I'm also on a 5h Go Faster window. I think it's not a completely lost cause as it basically just gives me a buffer to use more on some days, then it could take a couple of nights to charge back up fully so long as I don't use quite so much the next day. Replacing the inverter sounds expensive, but probably something to bear in mind next time I move house, upgrade to a 5kW or better hybrid.

My problem is that there is a risk I could overload the mains supply. We have the biggest grid supply available, without going to 3 phase, but I can easily get very close to that maximum rating overnight in winter, with the heating running, the hot water charging, the car charging and the battery charging. Luckily we're still on Economy 7, so have a seven hour off-peak window, and this means I can offset the times for things like the hot water and battery charging so they don't overlap too much. I think we'd struggle with a 4 or 5 hour window, mainly because everything would need to be on at the same time.

[Joeboy]

Oh wow, just in case I was ever interested in removing all the Pylons and going completely DIY, just discovered this: https://github.com/juamiso/PYLON_EMU

So basically pretend to be a Pylontech from a Python script so you can tell the inverter how much amps to charge/discharge at etc. Quite interesting just to see what information the BMS sends back to the inverter looking at that. Although there's a proviso in the README that it isn't tested with real hardware

Yes I've also considered the charge limit. My Luxpower will push about 3.6kW in maximum, and I'm also on a 5h Go Faster window. I think it's not a completely lost cause as it basically just gives me a buffer to use more on some days, then it could take a couple of nights to charge back up fully so long as I don't use quite so much the next day. Replacing the inverter sounds expensive, but probably something to bear in mind next time I move house, upgrade to a 5kW or better hybrid.

I plan to go up to a 5kW when the current hybrid unit fails. Hopefully at least 5 years from now (10 year mark). I'll be having a look at that link, thanks.

[Joeboy]

Yes I've also considered the charge limit. My Luxpower will push about 3.6kW in maximum, and I'm also on a 5h Go Faster window. I think it's not a completely lost cause as it basically just gives me a buffer to use more on some days, then it could take a couple of nights to charge back up fully so long as I don't use quite so much the next day. Replacing the inverter sounds expensive, but probably something to bear in mind next time I move house, upgrade to a 5kW or better hybrid.

My problem is that there is a risk I could overload the mains supply. We have the biggest grid supply available, without going to 3 phase, but I can easily get very close to that maximum rating overnight in winter, with the heating running, the hot water charging, the car charging and the battery charging. Luckily we're still on Economy 7, so have a seven hour off-peak window, and this means I can offset the times for things like the hot water and battery charging so they don't overlap too much. I think we'd struggle with a 4 or 5 hour window, mainly because everything would need to be on at the same time.

What are you limited to OGB? I went up to 100A grid fuse last year and TBH, I was regularly at 90A in the 5 hour window but not really hot on the tails. I plan to continue my zero gas approach to the best of my abilities and this pack extension will give me head room to have the storage heaters kick in a bit through the day too and continue that hope. Will also try and cutback a little on WBS too once we have mastered gas and maximise my use of the Ripple WT generation. Thank god for timers!