Uhome LFP 2400 Voltage Falling Under No Load Conditions

sb1710

Hi Folks,

In June 2022 I’ve had a Lux ACS 3600 and 4 x Uhome LFP 2400 batteries installed at my property (supplied and install by competent person) to store the surplus solar energy from an already installed roof top solar array. The system I thought had been working fine and was configured for 90% depth of discharge (DoD) in parallel for the batteries. I’d like to get some input from anyone with a similar system as to what happens with their battery voltages, does your system charge every other day in the winter?

When first installed in June, the good weather (sunny Aberdeen!) meant that the system was charging the batteries on a daily basis to 100% and I didn’t notice any issue.

However as we got into November and December, on the dark and poor solar production days, I have noticed that the pack voltage is falling once the 10% threshold for the pack is reached. So what normally happens is the voltage will gradually begin to fall over a period of hours and get to 49 volts at which point I assume that the battery management system kicks in and is triggering a charge from AC (mains), pulling approximately 360w and pushing around 1.5kWh into the battery pack every time.

What I have noticed happening and also has become more frequent, to the point of every other day at this moment in time. The pack voltage falling from 51volts to 49volts over a period of approximately 18 hours which I don't think is normal behaviour for this type of battery chemistry. I’ve got numerous 6S LiPo batteries from my RC hobby that have sat for months and lost little to no charge / voltage when I balanced and check them.

My question is I thought that Lithium Ferro-Phosphate (LiFePO 4) batteries have an initial short period of stabalising after disconnection from a load and then the voltage should remain pretty much constant with a very low self-discharge whereby the pack voltage remains the same for a long period (days or weeks)?

What i am seeing is worse than a Lead-acid battery that is damaged!

I’ve flagged this up to the supplier who changed the DoD to 14% to cover the loss of power and voltage fall, but this didn’t sit well with me as I believe that these batteries should work well at 90% DoD. Incidentally this didn’t solve the problem as the fall was/is so rapid that the system still was frequently charging from AC (mains) just on a slightly longer period (3/4 days).

I don't think that this is normal and suggests a faulty cell to me. Does anyone else Uhome LFP 2400 batteries have this type of behaviour?

I've attached an image from the Luxpowertek website from yesterday to show exactly what is going on (which I've sent to the supplier / vendor)

Any comments and thoughts would be welcomed.

propnut

Love it love it love it. I raised the EXACT same query on the same observation with my installer, with Luxpower and with the local agent for Luxpower and all I got was either deafening silence, a load of bovine feces or both.

Here check out my posts from this thread

https://forums.moneysavingexpert.com/discussion/6113817/lux-ac-battery-controller/p128

Oh and by the way it is not a faulty cell it is internal power dissipation from the DC/AC inverter stage. LUX claims standby consumption is <10w. From what I can see it is more like 30-50w

sb1710

Hi Propnut,

Much appreciate your response, it sounds like you've had the same "challenges" as I've had, asking a simple question (so that you can understand) and not getting a satisfactory response. This is my first post on here and then I was going to directly contact Lux and Aoboet if I hear nothing from the vendor.

Edit: The supplier has just sent me an email 20 mins ago!

However given what you’ve said, the internal power dissipation makes sense when the battery is at 10% SoC and continues to suck 50Wh out of the pack (loosing ~1kWh over 24 hours). Any further power drained means that the pack voltage falls rapidly when looking at the LiFePO4 discharge curve and then the BMS will kick in to prevent damage to the cells due to low voltage. I like your idea of using a remote isolator to disconnect the batteries from the Lux, I saw Tuya have a remote 125A breaker … I’m just busy with many other jobs at the moment!

Interestingly the supplier has sent out a replacement pack (to fix the autostart feature not working on one of the packs) and I still have the old battery / box in my garage on the floor which I assumed they’d want back for warranty purposes but as you’ve said I’m getting deafening silence. Perhaps it’s a free gift for me!

I’m more concerned that the battery pack have sustained some sort of damage which might affect the expected life (~10 years) as after 1 year the vendor will likely ignore me completely even though there is meant to be a 10 year warranty apparently! All I’m asking for at present is for them to demonstrate that the installed equipment (batteries) are all functional and without fault, to show me the results of the Uhome tests which they’re doing to prove the condition of the cells.

Generally the vendor has been very good apart from denying that the installer left an MBC terminal loose in the fusebox on the 10kw electric shower circuit, which tripped out many times due to heat (with the breaker getting dangerously hot) before i discovered the reason and an EPS socket wasn’t installed where I asked for it to be! We shouldn’t have to check the work of competent persons and put right faults at our own expense.

It does sound like reading through some of the threads around you post that loosing some power is normal, just how much I’m not too sure on and if the vendor had explained it when I'd asked, I’d have been satisfied!

I guess that in real terms there is a huge saving using a battery storage system in the long run it just needs to be flagged up that the winter months are going to cost you a little in electric cost with the BMS balancing and topping the packs up.

Thanks again.

propnut

So here's the thing. Switch off the batteries AND inverter at night and I am 99.9999% sure you will find the batteries have the same charge in the morning. Ergo it is not internal losses. Like you I am also an RC modeller and have loads of LiPo's and LiFE batteries sitting in my ammo boxes that haven't lost charge in almost a year as I have not been flying due to work.

Ergo if they don't lose power then dissipation is not from internal resistance.  s per my thread I also left the batteries on and disconnected the neg terminal from the inverter. The loss in this experiment was well within expected parameters as clearly the BMS must consume something but it was tiny. Connect back to the ACS 3600 and bang levels start dropping alarmingly again.

NOW!!!! I believe I have found the solution that does not require powering off or use of the remote isolator. Last night over 14 hours I lost just 0.5v. at 17:00hrs it was 51.3v and at 7am this morning it was at 50.8. Ordinarily it would have dropped to 49v well within the evening and started sucking +-350w/ph from the grid.

However I need to monitor it for a few days to ensure that wasn't an anomaly.

sb1710

So I've got the vendor looking at the Uhome batteries for me with Aoboet to confirm that there is no issues with the packs.

The issue i have is that the installer (who did a great job, hint of sarcasm there) didn't get the Uhome batteries configured online and simply buggered off and its only recently that the second home visit the installer configured these for me.

However i am still awaiting the account details!!!! Spoke again on the phone today to remind them.

Once in hand i will perform the battery disconnection test and see hopefully the same result as you, with very little in terms of self-discharge.

I'm very keen to know what the secret to this fix is once you've checked for repeatability!

SproutsMr

Hi all, 

I am new to this forum and probably have read all the materials and information that have been posted re the Luxpower and Aoboet Batteries. This is a great online community and I have found your discussions and shared information very helpful. 

I am hoping you could help me answer some questions about my system which I recently had installed.  I am afraid that the local installer has gone very quiet and the last telephone conversation I had with someone in their technical team a month ago told me "that I should stop googling things.. and that everything is fine with your system". 

I had a 2.66kw PV system installed in Nov 22 with a Solis inverter on the dc side and 7.2kw (3 x 2.4kw Aoboet Uhome batteries) connected to a Luxpower AC ESS.  My installer only showed the Luxpower app and did not set me up to use the battery monitoring app (which I learned about in this forum). 

My questions/issues are 

1.) I charge my batteries on octopus go nighttime tariff between 0030 and 0430 and I noticed my batteries only charge at max rate of 1.5kw.  I have also noticed the batteries only discharge as well at max rate of 1.5kw - any household load then that is needed above this is drawn from the Grid.  My understanding was max charge / discharge would 3.0kw based on having the 2 uhome batteries and the Luxpower ACS inverter that I have.

2.) When batteries are fully charged, the luxpower reports them having a voltage of 31.1VDC.  It never goes any higher than this.  I have discharged the batteries down to 10% and this has reported a voltage of 22.8VDC at its lowest.  I am not sure if it is supposed to behave like this (as I have noticed others in the forums post voltages about 52 vdc).

3.) Could you also provide instructions on how I connect to my uhome batteries using the uhome app?  I tried using the reset buttons on the master battery and unfortunately have not been presented with a "usr... " wifi ssid.  I have however found a secure wifi SSID with the same name as the serial number of my master battery.  I assume that is the wifi signal I would need to connect to but it is password protected. 

Please see screenshots included for reference. I am hoping you all can help me, please.  Very frustrating that my installer can only provide me with the comment "Your system is fine".  









Looking forward to a lively discussion.  Thank you all.


 

SproutsMr

SproutsMr said:

Hi all, 

I am new to this forum and probably have read all the materials and information that have been posted re the Luxpower and Aoboet Batteries. This is a great online community and I have found your discussions and shared information very helpful. 

I am hoping you could help me answer some questions about my system which I recently had installed.  I am afraid that the local installer has gone very quiet and the last telephone conversation I had with someone in their technical team a month ago told me "that I should stop googling things.. and that everything is fine with your system". 

I had a 2.66kw PV system installed in Nov 22 with a Solis inverter on the dc side and 7.2kw (3 x 2.4kw Aoboet Uhome batteries) connected to a Luxpower AC ESS.  My installer only showed the Luxpower app and did not set me up to use the battery monitoring app (which I learned about in this forum). 

My questions/issues are 

1.) I charge my batteries on octopus go nighttime tariff between 0030 and 0430 and I noticed my batteries only charge at max rate of 1.5kw.  I have also noticed the batteries only discharge as well at max rate of 1.5kw - any household load then that is needed above this is drawn from the Grid.  My understanding was max charge / discharge would 3.0kw based on having the 2 uhome batteries and the Luxpower ACS inverter that I have.

2.) When batteries are fully charged, the luxpower reports them having a voltage of 31.1VDC.  It never goes any higher than this.  I have discharged the batteries down to 10% and this has reported a voltage of 22.8VDC at its lowest.  I am not sure if it is supposed to behave like this (as I have noticed others in the forums post voltages about 52 vdc).

3.) Could you also provide instructions on how I connect to my uhome batteries using the uhome app?  I tried using the reset buttons on the master battery and unfortunately have not been presented with a "usr... " wifi ssid.  I have however found a secure wifi SSID with the same name as the serial number of my master battery.  I assume that is the wifi signal I would need to connect to but it is password protected. 

Please see screenshots included for reference. I am hoping you all can help me, please.  Very frustrating that my installer can only provide me with the comment "Your system is fine".  









Looking forward to a lively discussion.  Thank you all.


 

Sorry, meant to say "My understanding was max charge / discharge would 3.0kw based on having the 3 uhome batteries and the Luxpower ACS inverter that I have".

propnut

No way that voltage is correct. The 2400 Uhome is a 50V 50AH battery. The lowest voltage is 48v Make sure that the Luxpower is set correctly for Uhome batteries which should be option 7. Follow the instructions shown in this video to check. 

https://youtu.be/ASyUkdlkVcc

Also use the Luxpower APP to view the dashboard and where you see the voltage you should also see how many batteries it is seeing and what AH it is reporting them as. With three it should be saying 3 x 129ah (which is also not right but that's another story)

Next as far as the batteries go it sounds as though the batteries are already paired to "something" you should perhaps ask the installer first BUT if you wish to reset it as I did then follow this video BUT hold the reset button on the master unit down for 7-8 secs. It is actually covered in the manual.

https://www.youtube.com/watch?v=PC6ldzYEc9w

The manual for the batteries can be found here.

https://www.infinityinnovations.co.uk/wp-content/uploads/2021/02/Uhome-LFP-2400-User-Manual.pdf


You may find it impossible to only have the master switched on and the slaves off as the CAN bus will try an initialise the slaves. If so you will need to isolate the slaves from the master. 

WARNING!!!!! These batteries store a massive amount of energy. If you are not competent with electrics please do not attempt to break the circuits. Either get your installer back it or get a sparky with Solar experience. Accidents can happen all too quickly.

SproutsMr

Thank you for the speedy reply :-)

The tool is currently reporting a capacity of 150ah with 3 parallel batteries which you can see from my screenshot

However, following the guide in the video, my battery was set to option 2.  I have now set this to option 7 to match my uhome batteries.  As a result, the monitoring app is now reporting 3 batteries in parallel at a capacity of 43ah (please see screenshot)

Does this look right or make any sense?  Thanks again

propnut

No something is wrong. The batteries are in parallel so it should be 43 x 3 = 129ah. 
Read the battery manual fully. Then check all the dip switch settings. The master sets how many in the pack, then the slaves are set according to their number in the pack. There are red dip switches and a rotary dial.

Also check the wiring again by consulting the manual.

Alnat1

My pylontech battery has also been "strange" recently. I don't understand all this tech but I'm wondering if it could be as simple as the cold temperature in my garage, around 10C recently, doesn't suit it. Is that a really dumb idea?

Found this on the US5000 datasheet -  The recommended and max. continuous operation current is for a battery cell temperature within 10~40°C to consider, out of such temp. range will cause a derating on operation.