David Penfold Jan 2, 2025
We've had a power cut for 12 hours now and it's not funny any more. Ironically, it's stopped me continuing to build my 32kWh of battery storage that would have been great had I got my finger out a bit earlier.
Show threadDavid Penfold 

Current status of the battery boxes below.

Next steps: use dowels and screws to fix the walls on, insulate the interior, add the circuit breaker and terminals to the front panel (with 95mm2 wires), add the heating pad, charge the batteries a bit, put them in (tapping 3mm holes to the busbars first for active balancing and BMS monitoring), connect them to the circuit breaker then set up the central DC stuff with the shunt etc and connect to the inverters*.

* Will also require doing the new earth, finishing some cabling, getting the ATS working and fixing some wonky consumer units.

Jan 2, 2025 at 4:15pmWeb
Show threadDavid Penfold Jan 2, 2025
Getting some 304Ah LiFePO4 cells up to about 90% charge.
Show threadDavid Penfold Jan 3, 2025

Those 4 cells took 2.44kWh for a top up.

First battery box is slowly taking shape...

Show threadDavid Penfold Jan 7, 2025

Slowly making progress on my two 16kWh LiFePO4 batteries.

Any advice for better fixing the mahoosive circuit breaker would be gratefully received.

Show threadDavid Penfold Jan 8, 2025

Got the cell compartment sorted with compression rods and a DIN rail to strengthen the compression and add connectivity for the BMS and active balancer. Also added the 20W heating element.

Next up is to tap M3 threads on each busbar for the BMS wires, and further compressing the battery compartment before torquing down the busbars and adding the massive 95mm2 cabling and adding the front panel. Also need to add the active balancer and set it up.

Show threadDavid Penfold Jan 9, 2025

Started doing the M3 thread tapping.

First one worked fine, second one broke the drill bit. Piece of bloody junk.

I'll just use M6 ring lugs instead on the cell terminals.

Edit: No, I'll do it properly. Just bought a couple of 2.5mm drill bits and two M3 thread tappers instead of the useless all in one jobbie. I guess it'll give me time to assemble the other battery box.

Show threadDavid Penfold Jan 9, 2025
Just nearly spent €50 on a tapping kit but decided to get the nuts and a decent 3mm drill bit instead.
Show threadDavid Penfold Jan 9, 2025
It was a lot simpler just drilling. But I'm going to have to be really careful now attaching the ring lugs, somehow tightening the tiny M3 nuts, and bringing all 17 back to the distribution rail (crimping that end too) for all 17 in the right order to avoid magic smoke coming out of the active balancer or BMS (and not shorting any cells, which could be terminal).
Show threadDavid Penfold Jan 9, 2025
Fucksticks. I've put 5mm insulation foam between each cell and the sodding busbars are a mm or two too short. I'm going to try to compress them some more or it's all coming out and I'll replace all but the end ones with epoxy sheets. This is a pain as it involves taking out the compression plate and the heat pad and stuff. Arse.
Show threadDavid Penfold Jan 9, 2025

Well that was a right royal pain in the bum, but all the busbars are in place with the monitoring/balancing cables all correctly connected to the distribution doodahs.

Can't find my velcro to tidy up the cabling for now.

Show threadDavid Penfold Jan 10, 2025
No hot battery news today as I took my wife to the hospital at 3am and we got home at 3pm (she's ok, by the way).
Show threadDavid Penfold Jan 11, 2025
Great. My 95mm2 cabling lugs are too big. Have had to buy some 50mm2 cabling and M6/M8 lugs for that. Ho hum.
Show threadDavid Penfold Jan 12, 2025
It's amazing what you can do with a rusty old file and a bit of elbow grease (and suggestions from people on here). This just saved me over €200.
Show threadDavid Penfold Jan 12, 2025
I'm feeling lazy today, so possibly no gripping battery progress updates. Although I'll possibly decide to do something at about 11pm because it's gnawing away in the back of my mind.
Show threadDavid Penfold Jan 12, 2025

Bugger. Just watched a video on the REC BMS (the one I bought to control the batteries) and apparently any circuit breaker at the battery must be +ve only. There's a shunt for measuring current after where the -ve cables meet and there has to be nothing between it and the battery -ve. I don't mind redoing the front panel but I'm wondering if one of these would suffice as I've got a few of them https://www.amazon.fr/gp/aw/d/B09GG7XRGH

Or do I need to actually have something that would trip? The BMS should switch off if things get abnormal anyway. Ideas?

Show threadDavid Penfold Jan 13, 2025

I've gone for two of these 125A unipolar MCCB circuit breakers. They're a bit undersized if I want to switch one battery off, but I'll just be careful not to pull more than 6kW while performing maintenance.

https://www.amazon.fr/gp/aw/d/B09Q2F32ZB

Show threadDavid Penfold Jan 14, 2025

Ok, so couldn't carry on with the front panel so thought I'd test the NEEY active balancer. It's got that weird thing going on where two cables need to connect to the 8 +ve (on 16s) but the writing was too tiny to see properly. Anyway, a couple are showing 0V and I think I need to strip back the wires a bit more. That can wait for tomorrow... I'll need to check the connections to the busbars are ok too.

Edit: just noticed that the extra wire needs to go to the main positive, which should fix it.

Set the chemistry to LFP and to start balancing at 3.42V. I'll only be charging to 3.55V rather than 3.65 as one of the paralleled batteries will only have an active balancer and no BMS, so I want to minimise the risk of a runaway cell getting damaged.

Show threadDavid Penfold Jan 14, 2025
Yup, it was the main positive that needed the extra wire. Also stripped back the wires. Couldn't leave that once I'd noticed the wiring error.
Show threadDavid Penfold Feb 21, 2025

Actually finished one of the two 16kWh batteries and somehow managed to lug the 100+kg into the garage. Just need to torque everything down when it's in place.

Photos to come when my back recovers...

Show threadDavid Penfold Feb 21, 2025

My 3D awareness let me down a couple of times when attaching lugs to the cable so wasted some cable and lugs, and I initially had the one coming out of the bottom of the circuit breaker straight, but the cable wouldn't bend enough when I attached the front plate (meaning it was below floor level) so I had to do a 90° one instead.

I'll shorten the ones to the battery when I'm sure I've got enough lugs to change them out.

When I do that I'll add some shrink insulation too. The shrink wrap I've got now is either too small or too big for these cables (the latter being for Li-ion drone batteries).

#homeStorageBatteries

Show threadDavid Penfold Feb 27, 2025

Making progress on battery #2. No photos until it's done, because it's basically the same...

More breaking news as it comes in...

Show threadDanyFeb 21, 2025
@davep I bougt "shrink tape"! It is mainly for fixing where you cannot do not want to cut and resolder/reconnect cable. The glue does not adhere properly before you heat it so it is a bit trick for thin cabled. But it should work very good for bigger area cables, methinks.
Show threadJudithJan 12, 2025
@davep I thought you were having a night off from batteries tonight!?
Show threadDavid Penfold Jan 13, 2025
@aroundthehills I was just doing some research!
Show threadJudithJan 13, 2025
@davep Of course. 🙄 😄
Show threadMatthieu Weber 🇫🇷/🇫🇮Jan 9, 2025
@davep I hope you have a big, old-fashioned guillotine power switch to activate all that 🙂 (with thunder and lightning happening outside just at the right moment, of course).
Show threadDavid Penfold Jan 9, 2025
@matthieu I have a huge circuit breaker for each battery bank. And there'll be a 400A fuse for the two paralleled battery banks (they could happily pull 600A continuous at 50V) as well as a battery management system talking to the battery inverter (so if it gets too hot, for example, it'll tell the inverter to calm down).
Show threadTyson, Chicken Rancher 🐓Jan 9, 2025
@davep Wow! This is such a cool project! Good luck!
Show threadDavid Penfold Jan 9, 2025
@tsupasat I'm hitting plenty of annoying little roadblocks, but it's nice to see it progressing 😁