Size of battery

Jez1987 · Sat Dec 02, 2023 9:13 pm

Hi there.

New user. Just got a new 9.5kwh battery. Is there a way of seeing the size of battery on the Fox Cloud App? I’m worried it’s not working properly as my total yield is only coming out between 6.5-7kw.

Thanks

reef · Wed Dec 06, 2023 12:43 pm

Is this 4x HV25s you have? That would be 9.8kWh. You can check the voltage of the battery if you click the eye on the top-right of the real-time data tab. From there you can tell if all of your batteries are working by the voltage. 4x HV25s would be around 205v or thereabouts.

You could also be getting less than expected because your min SOC is set higher. I think the default is 20%. This can be put to 10 or 15% safely so you use more of the battery.

I have 5x HV25s which is about 12.2kWh. In reality with a min SOC of 10% I can use about 90% of 97% of the battery, so 10.5kWh.

Jez1987 · Thu Dec 07, 2023 2:13 pm

Thanks Reef. Do you see a drop off in battery storage performance when it is cold? My battery is in an uninsulated garage so i guess that could be a problem?

Jeremy

Dave Foster · Thu Dec 07, 2023 3:15 pm

Jez1987 wrote: ↑Thu Dec 07, 2023 2:13 pm Thanks Reef. Do you see a drop off in battery storage performance when it is cold? My battery is in an uninsulated garage so i guess that could be a problem?

Jeremy

Hi, yes the batteries will suffer a loss of performance when the are cold, there are 2 effects you may see -

The first one is on the charge current and it slows the speed at which they can charge when the temperatures drop below 15C, stopping the charge altogether when it gets to 0C

The second one is discharge power and capacity, the battery will not be able to discharge as quickly or deeply as it normally does when the temperature drops below 10C - the internal resistance of the battery increases and the efficiency decreases which lowers the capacity of the battery so you may also see a reduced capacity it falls to ~90% of normal at 0C, and rapidly drops below that. At -10C the BMS will not allow the batteries to discharge.

What many people do for the winter months is to provide an insulated enclosure (usually out of sheets of Kingspan or polystyrene insulation), but anything is better than nothing (I have see cardboard, old curtains etc..), just make sure you leave a small air-gap around the batteries to allow air to move as the batteries warm themselves when you are charging them.

Low temperatures do not damage the battery, they will recover when warm - it just stops the battery chemistry working properly.

I've linked to a recent post which covers a lot of this viewtopic.php?t=544