Cost of forced charge

[TR2implant]

Good evening, I’m a newbie to the forum and not very (electrically) tech savvy.

A bit of bio first, I had a pv installation in July this year with a Fox EP12 battery and 12 Sunpower 510w pv panels. In July I also bit the bullet and had anASHP system installed.

Having had such a good summer, to date I’ve only spent about £5 on electrical energy usage and I’m on a low standing charge tariff with Octopus. As winter draws on with lower solar charging and the heat pump coming more into use I’m looking at changing my tariff.

In comparing tariffs, how long does it take to force charge the battery from 10% to 100%?

Thanks, David

[Dave Foster]

There are a number of variables that will effect the charge time, the most significant is the size of the inverter as that capacity will be the maximum charge rate of the batteries - what inverter do you have H1-x, KHx ?

The good news is the EP12 battery has a high voltage and also a battery warming function (which you should use) as that will also be a major factor on charge speed in the winter months (everything below 16C begins to be throttled).

[TR2implant]

Thanks Dave, the inverter model is H2-6.0-E-G2-WL

[MaterialBarracuda48]

I find with my KH7 and EP11 that the temperature throttling occurs below 22°C, and the rate changes below that in stages.
So above 21.9°C is full rate.

Octopus Cosy is what you will need to swap to for Winter, 8hrs of charging.
As Dave has said, there is a heating function available (firmware levels permitting) for your battery. Depending on where it is stored, inside or outside the house, you can insulate it and then you won't need as much heating.

Mine is in a garage, and I basically chucked a small blanket over it, taking care not to cover the wires up.

[MaterialBarracuda48]

In comparing tariffs, how long does it take to force charge the battery from 10% to 100%?

Forgot to answer it more directly for you, with my previously mentioned equipment.
Under perfect temperatures, ~1.5hrs. You have a little less inverter power, and a bit more energy to store, so expect to budget nearer to 2hrs.

The time to charge will increase when colder, it's important to insulate the battery where possible, and to use the heater function as backup... because if you enable heating, the battery doesn't charge at the same time (unless they have fixed this) Good news is charging does heat the battery up a fair bit, so although the rate might start off slow, it will increase.

[Dave Foster]

I find with my KH7 and EP11 that the temperature throttling occurs below 22°C, and the rate changes below that in stages.
So above 21.9°C is full rate.

Thanks @MB, Fox have been quoting the 16C and so I wondered whether the latest firmware had reduced the throttling from the 21C down to 16C, but certainly agree all models of battery in the UK ‘used’ to begin throttling as it falls past 21C. The good news with the EP12 nominal voltage at 384V it means you can lose quite a bit in throttling before you would notice it drop below the ~6kW max charge rate.

Anyhow, with a 6kW H1 you should be fully charged from 10%->100% in less than 2 hours under most conditions.

Octopus Cosy is what you will need to swap to for Winter, 8hrs of charging.

With a heat pump, totally agree

[MaterialBarracuda48]

Thanks @MB, Fox have been quoting the 16C and so I wondered whether the latest firmware had reduced the throttling from the 21C down to 16C, but certainly agree all models of battery in the UK ‘used’ to begin throttling as it falls past 21C.

I am still running the older v1.011 FW, so the temperature points could be changed for sure.
Maybe I need to get that battery FW loaded on, if the full rate kicks in ~16°C

Would be nice to see some proper firmware release notes... come on Fox!

[TR2implant]

Thanks for all your replies. I was considering Cosy as my option anyway so at least that confirms that idea. My battery is outside, although I have just boxed it in, albeit hit and miss cladding so boxing still ventilated

[MaterialBarracuda48]

IIRC you need a battery FW of greater than v1.009 for heater controls to work.

So, it's worth checking what firmware version is on your battery, and also checking in 'Quick Settings' that your 'Battery warmup' option exists, and can be enabled. Unless this has been fixed, you cannot warm the battery and charge at the same time, so if you do need to use heater controls, you are best using them on the longer (3hr) cosy cheap periods for the first 30-59 mins (04:00 to 04:29 / 04:59 for example)

Insulation is going to be your best overall choice vs. heating, with the simple blanket, I no longer needed any battery heating in the garage, outside, it will help keep warmth in (or some posh kingspan!)

[MaterialBarracuda48]

Just an update for the numbers, I recently got Fox to load the latest v1.013 FW for my EP11 battery.
Charging today, I was getting 5.5kW charge rate until battery warmed up to 21°C, then rate increased to 7.7kW.

Conclusion you need above 21°C to charge EP battery at full rate.
The rate limits might be different for other battery models (more testing data needed)

[spiral]

Just an update for the numbers, I recently got Fox to load the latest v1.013 FW for my EP11 battery.
Charging today, I was getting 5.5kW charge rate until battery warmed up to 21°C, then rate increased to 7.7kW.

Conclusion you need above 21°C to charge EP battery at full rate.
The rate limits might be different for other battery models (more testing data needed)

My battery FW is 1.010 so way behind. Why don't fox update these automatically when they become available. What is the benefit to me of requesting this to be updated and do I go to fox directly or through my installer?

[MaterialBarracuda48]

My battery FW is 1.010 so way behind. Why don't fox update these automatically when they become available. What is the benefit to me of requesting this to be updated and do I go to fox directly or through my installer?

There's always a chance when pushing out en-mass a pile of firmware upgrades. Fox have done this beforehand, usually for very good reason. For the battery though, the firmware just seems to expose different on/off temperatures, so not exactly necessary for some.

The direct benefit you will see for your new FW, is the new temperature range you can set. During Winter, if you want to charge it fast, then you may struggle (as reported last year on a mega thread) to fully charge up the battery during cheap rate windows. This is even more of an issue if you have a lot of power needing to be stored up, like say above 20kWh for example.


So 100% recommend that you get this applied, you can approach your installer, or Fox. I emailed Fox, as it's much faster than my installer by a Country mile, turnaround is usually 24-48hrs.

service.uk@fox-ess.com (or whatever your local Country uses)
Include inverter serial number (just in case)
And include ALL serial number(s) for batter(ies) (I assume they need them all?)

[spiral]

Thanks
Email submitted.