Idiot's guide to a self build battery

[Colin Deng]

I just wanted to report another success thanks to all your help and encouragement (and the services of Colin)

Thank you for the Photo sharing
If there anything we can improve about the battery or the service
Please kindly let us know~

[Joeboy]

I just wanted to report another success thanks to all your help and encouragement (and the services of Colin)

Liking the different style of install.

[sw25481]

For reference I used this Box from Wickes

£23 and it fits 16 Eve cells perfectly (and has wheels)

https://www.wickes.co.uk/Strata-Heavy-D ... torage+box

The batteries are heavy so I used a piece of 12mm ply in the bottom to strengthen it.

I mounted this fused battery disconnect to the side of the box

https://www.solar-wind.co.uk/off-grid-p ... 0a-to-160a

£60 including two 100amp fuses

I used a piece of ply on the inside of the box and screwed through the box to the ply when mounting the battery disconnect. This gave a really secure mount for the fused disconnect and let me fit a shelf to hold the BMS

My BMS is the JK B2A24S20P bought from the Aliexpress JK store for £134.62, just under the £135 you would have to pay import duty on. This is the one with the 2amp balancing current and Can Bus
The BMS came with a push switch to turn it on (unlike the earlier versions) so drilled a hole in the box to mount that. The wires were short so I used a mini bus bar from Amazon to extend the negative from the BMS to the battery disconnect.

Cells were $2051 USD at the time I bought them, about £1694 including all shipping and taxes due delivered to my door.

I already had some spare cable and sundries so all in it cost me about 1900 for 15kwh of storage

I have chosen not to compress the cells much and just wrapped them in thick plastic I had left over from a damp course on a concrete floor and then wrapped them 4 at a time with fibre glass reinforced packing tape from Toolstation. I did them in groups of 4 as I could just about lift 4 at a time into the box.

I made up some cables and initially charged the batteries in banks of 4 using a 12v charger until they were close to 3.5v per cell. Then I connected them all together and used my bench power supply to bring them all up to just under 3.65v and left them for a day to complete the top balance.

Then I used the bus bars that came with the batteries to assemble them into a 16 way pack.

I chose to drill and tap the bus bars to connect the leads from the BMS. I then 3d printed some terminal covers for extra piece of mind even though the battery box has a cover. I used 5 amp fuses in holders on all the connections from the BMS

LifePO4
16 230Ah
Not got them delivered yet.


Not seen any information on best way to mount / use them.

Some people are.

Using threaded rod to compress the battery.
Side to Side.
To stop the battery expanding when it warms up.
But not end to end / Top to bottom. ?
Some are mounting them vertical. Some horizontal.
I am thinking horizontal. If metal things get dropped on them, possibly better of ?
But horizontal. Is there chance of leakage around the terminals . ?
Not seen any information on web sites about how to position them.
Use foil backed insulation on all sides / bottom.?

[Stinsy]

I noticed the terminal covers and wondered where you got them!

They seem like a REALLY good idea to me. Anything that makes it a little bit more difficult for a dropped spanner (or whatever) to have undesirable consequences is a good idea in my view!

Really nice project!

[nowty]

I noticed the terminal covers and wondered where you got them!

Its in his write up,

"I then 3d printed some terminal covers for extra piece of mind even though the battery box has a cover."

[NikoV6]

Interesting read!


How much additional effort/monitoring/maintenance is required for this sort of setup please?

Once its all in over say a plug and play solution (putting aside the additional extra cost of the P&P solution)

[Moxi]

Like JB said he might have to dust it in six months time

Moxi

[Tinbum]

I took the plunge today and ordered some after all the good reports.. I'm planning on installing more PV, have been for some time and these will go on an additional system.

[MrPablo]

Question for the group seeing as there's many smarter people than I here...
I currently have one of the Frankenstein style fuse disconnects between my pylontech stack and the inverter, and I'm planning to retain that for the DIY stack.
The question is, do I need a separate disconnect for the battery pack itself, similar to the disconnect Nowty had previously shown?

[nowty]

I took the plunge today and ordered some after all the good reports.. I'm planning on installing more PV, have been for some time and these will go on an additional system.

Additional Solar and Batteries.
Tinbum demonstrates his new system to the DNO............,