Idiot's guide to a self build battery

[Joeboy]

Andy,
These guys supplied good quality 25mm2 cable. Rated to 170A.

https://www.ebay.co.uk/str/splitchargeuk

12 degs is a big difference in temp across a stack. Are the units airgapped between each other? Do you have passive air vents in the powershed walls to allow airflow through? I used a couple in our cabin and they are excellent. 90 deg turn and bugscreen on them stainless steel, fit and forget.

[resybaby]

Is that one of those business to business transactions ?

Well, sort of

£50 "installation" charge applied - not a bad deal for an "installer" to travel (cough) all the way from Coventry to Cornwall to "fit" them me thinks. Oddly its refundsble as well once "installed" and evidence provided.

[Stinsy]

Is that one of those business to business transactions ?

Well, sort of

£50 "installation" charge applied - not a bad deal for an "installer" to travel (cough) all the way from Coventry to Cornwall to "fit" them me thinks. Oddly its refundsble as well once "installed" and evidence provided.

[resybaby]

Quite silly realy but can happily dad dance around the rules if needed to save a few quid.

Worked out @ £1109 per battery, including the associated brackets.

[Lincs Robert]

Is that one of those business to business transactions ?

Well, sort of

£50 "installation" charge applied - not a bad deal for an "installer" to travel (cough) all the way from Coventry to Cornwall to "fit" them me thinks. Oddly its refundsble as well once "installed" and evidence provided.

Hi, is something that they are happy to provide to people generally? I might be tempted myself if that’s the case

[Andy]

12 degs is a big difference in temp across a stack. Are the units airgapped between each other? Do you have passive air vents in the powershed walls to allow airflow through? I used a couple in our cabin and they are excellent. 90 deg turn and bugscreen on them stainless steel, fit and forget.

Yeah, I wasn't that happy about it and added a 100mm fan to take the air from the top of the room and dump it under the battery stack. It runs 24/7 and supposedly the bearings are good for 7 years.

Unfortunately I was so focussed on the 25ºC being optimum for the battery I insulated and studded out the small shed. It was during the build I realised that 18kW of solar is going to produce well over 1kW of heating with losses. This combined with the internal dimensions of the shed being 2m x 1.2 x 2m high means there is a huge gradient from bottom to top of the room. Passive cooling would never keep up with the heat produced at peak production. I also have two powerful 6 inch fans which are temperature controlled removing air from the top of the shed to keep it at 25 degrees. I had thought of using an air conditioning unit but they use a lot more power than the fans.

I have also considered removing the studs/insulation which will give me another 45cm or so in each dimension. This wouldn't fix the temperature but would give me more space which I desperately need. That requires days of rewiring and I'm not even sure the wires would be long enough in places. Maybe I'll consider doing it when the quattro is away for fixing. It's annoying as obviously the stud work/hardibackers came to quite a bit in cost. Instead I could have nice fire proof brick walls and be done with it.

I've even got underfloor heating embedded in the slab which hasn't been on since keeping the batteries warm before full commissioning.

[Andy]

These guys supplied good quality 25mm2 cable. Rated to 170A.

https://www.ebay.co.uk/str/splitchargeuk

Thanks, I'll check them out.

[Joeboy]

12 degs is a big difference in temp across a stack. Are the units airgapped between each other? Do you have passive air vents in the powershed walls to allow airflow through? I used a couple in our cabin and they are excellent. 90 deg turn and bugscreen on them stainless steel, fit and forget.

Yeah, I wasn't that happy about it and added a 100mm fan to take the air from the top of the room and dump it under the battery stack. It runs 24/7 and supposedly the bearings are good for 7 years.

Unfortunately I was so focussed on the 25ºC being optimum for the battery I insulated and studded out the small shed. It was during the build I realised that 18kW of solar is going to produce well over 1kW of heating with losses. This combined with the internal dimensions of the shed being 2m x 1.2 x 2m high means there is a huge gradient from bottom to top of the room. Passive cooling would never keep up with the heat produced at peak production. I also have two powerful 6 inch fans which are temperature controlled removing air from the top of the shed to keep it at 25 degrees. I had thought of using an air conditioning unit but they use a lot more power than the fans.

I have also considered removing the studs/insulation which will give me another 45cm or so in each dimension. This wouldn't fix the temperature but would give me more space which I desperately need. That requires days of rewiring and I'm not even sure the wires would be long enough in places. Maybe I'll consider doing it when the quattro is away for fixing. It's annoying as obviously the stud work/hardibackers came to quite a bit in cost. Instead I could have nice fire proof brick walls and be done with it.

I've even got underfloor heating embedded in the slab which hasn't been on since keeping the batteries warm before full commissioning.

Where is the air coming in from? I'd remove the 100mm fan and set one of the 6" driven fans on the opposite side of the room. Looking to pull cold air in directly from outside and expel it out the top at the other side.

[Andy]

Where is the air in coming from?

A hole

[nowty]

These guys supplied good quality 25mm2 cable. Rated to 170A.

https://www.ebay.co.uk/str/splitchargeuk

Thanks, I'll check them out.

25mm is the same size as the standard pylontech cables, they get warm at 100A and hot at 120A. If your thinking of a continuous max over 100A I would be going to 35mm or even 50mm. I was shocked when you earlier mentioned “future proofing” at 25mm.

It’s not just the cables that generate heat, but the isolators, fuses, crimp connectors, etc.

I have 70mm cables to my main 8kW battery inverter and 50mm intermediates to each of my battery banks. I used to use 35mm for my intermediates but they got too warm for my liking if I was running only off a single bank at 150A so I upgraded to 50mm.