Nowty Towers DIY Battery Project

[AGT]

Trust me I’ve read all the threads! Appreciate all the advise from all posters.

[Stinsy]

Hope you don’t mind me asking, as I’ve just splashed some cash due to yours and others inspiration
I know you don’t have a BMS but if you did how would a 2p16s battery like this work with a BMS, wouldn’t the 2 cells in parallel fool the BMS if there was an issue with one cell?

BMS is a horrible and somewhat meaningless term used frequently by people who don’t know what one does!

Exactly Stinsy, folk might want to back up a few posts to read my explanation about what exactly a BMS is, it is frequently misunderstood.
https://camelot-forum.co.uk/phpBB3/view ... 291#p58134

I’ve had someone tell me confidently that a BMS is “essential” but the same person couldn’t tell me what a BMS does other than “manages the battery”.

[knighty]

don't want to jump on your thread but silly to start a new one...

how's the temperature where you keep your batteries ?


building a workshop for mine, I'm a bit worried they cold in winter will do them no good.... before I install them it wouldn't be too big of a deal to box them in a bit to control the temperature a bit...

could even get a small shipping container dropped on the slab and build around it, so that it could be used for the battery storage

[nowty]

don't want to jump on your thread but silly to start a new one...

how's the temperature where you keep your batteries ?


building a workshop for mine, I'm a bit worried they cold in winter will do them no good.... before I install them it wouldn't be too big of a deal to box them in a bit to control the temperature a bit...

could even get a small shipping container dropped on the slab and build around it, so that it could be used for the battery storage

They are in a naturally cool temperate environment, typically min 10 degrees in winter and max 20 degrees in summer, cos its in a cave like place. Important thing is to avoid negative temperatures and preferably keep over 5 degrees, or even better above 10 degrees or even higher if your charging at high rates. Having a larger battery bank helps as I can charge at 200A and its still only around 0.1C.

Discharge isn't a problem even down to minus 20, but charging is,

Spec of my Envision LFP cells,



And the latest EVE LFP cells,

[Stinsy]

don't want to jump on your thread but silly to start a new one...

how's the temperature where you keep your batteries ?


building a workshop for mine, I'm a bit worried they cold in winter will do them no good.... before I install them it wouldn't be too big of a deal to box them in a bit to control the temperature a bit...

could even get a small shipping container dropped on the slab and build around it, so that it could be used for the battery storage

Low temperatures absolutely are a concern for this kind of LFP battery. However only at high C-rates.

C-rates are one of those things that might seem super complicated at first sight but are in reality VERY simple. If you have a 1Ah battery then if you’re charging/discharging it at 1A then that is 1C (and 0.5A is 0.5C, 2A is 2C, and so on). Typical LFP batteries can be discharged at 0.5C nomatter how low the battery temperature. Charging however is where the problems occur. Below 0℃ a 0.1C charge rate is recommended and below -10℃ 0.1C is recommended.

Nowty’s new battery is 16s2p, that makes it 51.2V 560Ah. So 0.5C is 280A or 14.3kW and 0.1C is 28A or 1.4kW. He’s about to double the size of his battery (IIRC) so those figures will double.

Now the important point is that Nowty lives in the south of England where ambient temperatures rarely dip below zero and it is the cell temperature that is important. These batteries have a large thermal mass, charging/discharging them introduces heat and they take a very long time to cool down. I doubt his cells would ever drop below 0℃even if he experienced a long period of unusually cold temperatures.

If you live in Scotland and the batteries are in an unheated outbuilding of some kind, then some king of “frost protection” is possibly a good idea.

[knighty]

I have 115kwh of Nissan leaf cells, but I'm planning to have a lot more that that, I'll end up with high amp loads but still low C rates

mostly worried about overnight temps dipping below zero, or extended times in winter below zero (north east England)

shipping container with an A2A system might be best

if I mount the inverters on the outside of it, it means I can relax about busbars a bit etc. don't need to cover them up as much

[nowty]

I have 115kwh of Nissan leaf cells, but I'm planning to have a lot more that that, I'll end up with high amp loads but still low C rates

mostly worried about overnight temps dipping below zero, or extended times in winter below zero (north east England)

shipping container with an A2A system might be best

if I mount the inverters on the outside of it, it means I can relax about busbars a bit etc. don't need to cover them up as much

Your cells are some sort of LMC battery and don't suffer the same problem in the cold as LFP, from top of my head I'm pretty sure they can charge at sub zero temps, I'll try and look them up later for the typical spec.

[NoraBatty]

I have 115kwh of Nissan leaf cells, but I'm planning to have a lot more that that, I'll end up with high amp loads but still low C rates

mostly worried about overnight temps dipping below zero, or extended times in winter below zero (north east England)

shipping container with an A2A system might be best

if I mount the inverters on the outside of it, it means I can relax about busbars a bit etc. don't need to cover them up as much

My 2p worth.
I had a small 1.7kw storage heater in the battery shed over winter. This kept the batteries happy in a half completed half insulated shed.
Charging the SH for 2 hrs a night got temps up to 20C in there during that period (old SH leaking alot of heat) and kept them above 10C until the next charging session 24hrs later in -14C conditions.

Since then the shed has been fully finished, with thought given to internal thermal mass, doubling up as fire proofing, and insulation.
Since the inverter was installed, and batteries now operating and running the house, charging overnight, the temperature in there has not dipped lower than 15C, with no SH, despite a few mornings waking up to -4C.
Its lovely and cosy in there and the inverter and batteries are effectively warming the space up themselves.

Next winter will be the real test, but i have heaters inside the battery cases that will keep the batteries warm whilst i experiment with the overall shed temperature and figure out if the SH is needed anymore.

I would prefer to keep the entire shed warm rather than just the batteries by their heat mats, as there is less chance for condensation and other surprises to occur if everything is warm.

The shed externally is 8x4. Internally probably 7x 3 ish now after insultation and boarding. Just so you get a sense of the space.
NE scotland.

Whatever size you go with, i would recommend following the same lines. Insulate as best you can, but give the heat generated within the area the best chance of staying in there with thermal mass.

[AE-NMidlands]

Whatever size you go with, i would recommend following the same lines. Insulate as best you can, but give the heat generated within the area the best chance of staying in there with thermal mass.

...but make sure it has an escape route in high summer?

[NoraBatty]

Whatever size you go with, i would recommend following the same lines. Insulate as best you can, but give the heat generated within the area the best chance of staying in there with thermal mass.

...but make sure it has an escape route in high summer?

Thats what an extractor fan or equivalent would do yes.
The insulation would reduce abusive temps coming in from outside in high summer. Then with an extractor running in summer to vent any heat the thermal mass would not be loading excessively.