Hello all,
I currently have 3x HV25 + 1x BMS stored on one stack, in my loft. System is running great.
In the future, I am planning to swap my old gas stove with an induction stove. We cook almost every day, so I am expecting to require another 1.5-2kwh just for that. Will therefore likely add another module to cater for this. Given that I already now have ~95kg on one sqm, to spread the load, can I place them on two stacks next to each other? e.g. two stacks of two HV25 each and one of them with BMS on top? that would effectively spread only 60kg over one sqm. I think the interconnecting DC cables between the batteries are quite short, so would need to build a longer one?
n.b. loft is fully boarded with T&G 18m chipboard. Would need to check for joist dimensions, but they are I believe standard 40cm spaced.
There are longer (1 meter) FOX branded cables available for interconnecting the battery modules.
I have two phyiscal stacks of HV25s next to each other in one logical stack.
I have two phyiscal stacks of HV25s next to each other in one logical stack.
Thank you, that's re-assuring. I will let my installer know.
How many batteries do you have? Any chance you have a picture of the two stacks next to each other?
How many batteries do you have? Any chance you have a picture of the two stacks next to each other?
I've had 5 (and 6 since August, so 164kg!) HV25s up there for 2 years now. 
Mine were installed front side up by the installer, so that they span more joists. I haven't encountered any issues but its always been at the back of my mind I must admit.
I would have preferred them in the detached garage to be honest, but it is what it is.
Mine were installed front side up by the installer, so that they span more joists. I haven't encountered any issues but its always been at the back of my mind I must admit.
I would have preferred them in the detached garage to be honest, but it is what it is.
Ahh also in loft then, wow.
If they have been installed front side up, did they have to build some sort of enclosure/rack holding them in place upright?
If they have been installed front side up, did they have to build some sort of enclosure/rack holding them in place upright?
The battery brackets hold them securely upright and spread the weight over each battery. They're all attached to each other by the brackets so they can't move or fall over.
Thanks. Ah, I thought you had them split into two stacks, e.g. 3+BMS and another 3 next to it. But upright might also help to spread the load.
Last edited by nero44 on Thu Sep 04, 2025 5:30 pm, edited 1 time in total.
Hello,
I need some help please. Couple months passed and I finally managed to get hold of a battery.
I installed everything and wired it up, however the new battery is showing the alarm LED. I've disconnected it now again.
Also my BMS dip switch was set to 0 (with 3 batteries on system), but it appeared to see all of them.
How can I troubleshoot this? Is it normal to have the alarm LED blinking at the start?
I need some help please. Couple months passed and I finally managed to get hold of a battery.
I installed everything and wired it up, however the new battery is showing the alarm LED. I've disconnected it now again.
Also my BMS dip switch was set to 0 (with 3 batteries on system), but it appeared to see all of them.
How can I troubleshoot this? Is it normal to have the alarm LED blinking at the start?
Just measured voltage with a multi meter.
SOC of entire system before adding the new one was 45%.
One individual battery showed about 52vols. The new one I got (second hand but only used once to connect), only shows 15.2 volts. I assume this is the reason for the alarm.
Does it mean the battery just needs to charge or is the battery faulty? it was in storage and not connected to a system for several months.
If it just needs to be charged, I assume it would be safer to deplete the rest to minimum 10% before I connect the new one?
SOC of entire system before adding the new one was 45%.
One individual battery showed about 52vols. The new one I got (second hand but only used once to connect), only shows 15.2 volts. I assume this is the reason for the alarm.
Does it mean the battery just needs to charge or is the battery faulty? it was in storage and not connected to a system for several months.
If it just needs to be charged, I assume it would be safer to deplete the rest to minimum 10% before I connect the new one?
If the new battery is at 15.2V that is the cause of the alarm - it’s not good (potentially damaging) for a battery to get that low, the system won’t be able to deal with it - the only way to recover it is to separate it from the system and attempt a slow charge using a DC charger.
Hi Dave, thanks for responding.
I have taken it off my system immediately once I saw the alarm. My system is now running normally again in the old setup.
From my limited understanding of batteries, should the battery not show much more voltage even if it is close to depleted? To put differently, is this potentially a faulty battery, which I would need to get replaced? I've bought it off eBay, so I am not even sure I will have some warranty claim.
What sort of DC charger would I be looking at? I am assuming I require some specialist equipment, coming at a cost.
I have taken it off my system immediately once I saw the alarm. My system is now running normally again in the old setup.
From my limited understanding of batteries, should the battery not show much more voltage even if it is close to depleted? To put differently, is this potentially a faulty battery, which I would need to get replaced? I've bought it off eBay, so I am not even sure I will have some warranty claim.
What sort of DC charger would I be looking at? I am assuming I require some specialist equipment, coming at a cost.
Any new battery would be supplied at approx half charge which assumes they will be sold and installed within a fixed time (approx 12 months), given battery internal resistance the battery voltage will gradually deplete over time and eventually fall below the minimum 3.1V/cell which is where the Fox BMS will give up in attempting to charge.
To flatten a half charged battery would likely take well over 18 months so it’s likely this battery has been on the shelf a very long time or used and taken out of a system when the soc was low.
You would need either a lithium battery charge that can charge at approx 60V DC (and is capable of charging a low voltage battery), or a slow charge from a 60V DC bench power supply - it might be worth seeing if anyone you know has one (you never know) but to buy new is likely going to be £80-£100.
All you need to do is put enough charge in to raise the voltage enough for the BMS to see it as ‘real’ battery.
To flatten a half charged battery would likely take well over 18 months so it’s likely this battery has been on the shelf a very long time or used and taken out of a system when the soc was low.
You would need either a lithium battery charge that can charge at approx 60V DC (and is capable of charging a low voltage battery), or a slow charge from a 60V DC bench power supply - it might be worth seeing if anyone you know has one (you never know) but to buy new is likely going to be £80-£100.
All you need to do is put enough charge in to raise the voltage enough for the BMS to see it as ‘real’ battery.
You mean something like this? https://www.ebay.co.uk/itm/286405865852 ... =view_item
I've also sent an email to fox ess UK support to see if they can help in any way.
I've also sent an email to fox ess UK support to see if they can help in any way.
So, I have tried using a DC Bench supply.
Getting it out of the cutoff actually worked and managed to fully charge up until 58.4v. It went through constant current and then switched to constant voltage as expected. It all looked promising...
However, upon reconnecting I am getting 211 BMS Hardware Protect and the battery in question (and inverter) have the slow red LED + beeping.
Firmware is all the same on all batteries and in Fox Cloud I can see the increased capacity and voltage, but clearly something is not right.
Any other ideas, before I need to consider this a sunk cost?
Gotta say, but disappointed by Fox as I went through the trouble of getting a warranty certificate transferred only to find out that I do not have any warranty. This basically means if your installer goes belly up (which happens) then your fox system warranty is out the window...
Getting it out of the cutoff actually worked and managed to fully charge up until 58.4v. It went through constant current and then switched to constant voltage as expected. It all looked promising...
However, upon reconnecting I am getting 211 BMS Hardware Protect and the battery in question (and inverter) have the slow red LED + beeping.
Firmware is all the same on all batteries and in Fox Cloud I can see the increased capacity and voltage, but clearly something is not right.
Any other ideas, before I need to consider this a sunk cost?
Gotta say, but disappointed by Fox as I went through the trouble of getting a warranty certificate transferred only to find out that I do not have any warranty. This basically means if your installer goes belly up (which happens) then your fox system warranty is out the window...
It sounds like the battery cells have taken a charge ok - when you say the red alarm light is flashing - does it do that on its own when not connected to the pack ?.
Just wondering if there is a firmware mismatch on the batteries - the latest firmware uses auto addressing but earlier version you used to have to set the dip switches for the ID.
If they are auto addressing you don't set any of the dip switches but the older version needs it's address to be set.
It's disappointing that Fox won't offer any warranty, but if you raised a support ticket on them - they might be able to remotely diagnose (and/or reset any alarms)
Just wondering if there is a firmware mismatch on the batteries - the latest firmware uses auto addressing but earlier version you used to have to set the dip switches for the ID.
If they are auto addressing you don't set any of the dip switches but the older version needs it's address to be set.
It's disappointing that Fox won't offer any warranty, but if you raised a support ticket on them - they might be able to remotely diagnose (and/or reset any alarms)
Thanks for responding.
When not connected the battery does nothing. No LEDs no flashing, just off.
Once I connect it and start up the BMS, I get the usual checks, then the three good ones go green and the fourth one starts flashing the red alarm LED and also the BMS flashes the alarm LED. I can't recall if the beeping comes from the battery or the BMS.
All batteries are on the same firmware >> 1.01 and the BMS is on 1.004. None of them (also the functioning ones) have their dip switches set, all on down position.
Unfortunately I am not getting anywhere with Fox. I might try if my installer is willing to take a look. Of course this will come at a cost.
When not connected the battery does nothing. No LEDs no flashing, just off.
Once I connect it and start up the BMS, I get the usual checks, then the three good ones go green and the fourth one starts flashing the red alarm LED and also the BMS flashes the alarm LED. I can't recall if the beeping comes from the battery or the BMS.
All batteries are on the same firmware >> 1.01 and the BMS is on 1.004. None of them (also the functioning ones) have their dip switches set, all on down position.
Unfortunately I am not getting anywhere with Fox. I might try if my installer is willing to take a look. Of course this will come at a cost.