Cold nights?

[mossdale]

Hello,
Not long been a member so hoping someone can h
elp. We've had solar since the feed in tariff days so when we added a battery in June we went the AC route with nominal 10kW of HV batteries and an AC 5 inverter
These are mounted up in our loft which our installer said was fine. I was slightly concerned about overheating on the summer but it seams the opposite is true. When I force charge from off peak in the early morning the batteries usually charge at 4.7kW but for the last two mornings they have charged at only 2kW for some time before gradually climbing to the expected 4.7kW. The point the increase starts looks like a BMS temperature of 1 6.7 degrees reaching 4.7kW at about 19 degrees. Is this a temperature effect and do I need a small heater up there or would insulation of the battery stack suffice. Any help appreciated as this is a steep learning curve for me!

Martin

[calum]

Yes, they don't like the cold. Building an insulated box (9mm OSB lined with 50mm of EPS sheet) did the trick for mine which are in an unheated garage.

See also https://www.foxesscommunity.com/viewtopic.php?t=215

[reef]

This is my solution. Its 50mm polystyrene pinned together using weed membrane pins. The batteries themselves underneath have a standard fire blanket on for further insulation and fire protection.

The results have been miraculous. Previous to this temperatures were dropping below 15C on the pack overnight and like yourself, charging rate dropped. Ever since temperatures have been between 20-28C with an absolute minimum of 19.5C despite dropping as low as 2C outside.

It cost about £30 to do all in. A no-brainer really!

[RoyS]

Thank you for the post. Are the cables inside the box and do they not get cooked?
Thank you

[reef]

I have an insulating fire blanket over the cables just for a piece of mind. However in normal running they shouldn't ever get hot.

I've had this insulation on for over a year and didn't actually need to remove it over the summer as it seems the biggest challenge has been keeping the batteries warm enough rather than cool!

I've added an extra HV25 battery in the mean time too so the cover conveniently now covers the HV25s bit not the BMS meaning the cell temps are closer to the BMS temps. Often the BMS was above 20C but the minimum cell temps much lower.

[RoyS]

Thank you so much for the quick response.
I have ordered the boards and should arrive by Monday. I assume all 5 sides are covered. Did you keep 30cm gap between the batteries and the insulation please?
Thank you so much once again.

[Dave Foster]

Thank you so much for the quick response.
I have ordered the boards and should arrive by Monday. I assume all 5 sides are covered. Did you keep 30cm gap between the batteries and the insulation please?
Thank you so much once again.

30cm is what Fox recommend to allow air to circulate, some have installed it tighter but usually with small fans to help circulate the air.

If on a cold floor, getting insulation under the batteries as well really helps.

[Can]

Regarding floor insulation atop concrete flooring. My minimum recommendation is 25mm rigid waterproof insulation with 12mm OSB on top and some batons to allow airflow underneath the pack. I’ve had very large packs laid out on this arrangement without issue.

Keep it low and simple.

[reef]

Thank you so much for the quick response.
I have ordered the boards and should arrive by Monday. I assume all 5 sides are covered. Did you keep 30cm gap between the batteries and the insulation please?
Thank you so much once again.

Mine is about a 10-15cm gap around, but it is not insulated below and is open at the back so there's enough airflow.

It still got quite cold over the last week, so I may have to close up the back. Still much better than without though!