I live in New Zealand and have purchased three 10kWh LiFePo battery packs (total 30kWh, 3 x DL-LFP-51200’s) from Delong Battery Technology (DelongTop) from Shenzhen, China. I have been having a problem with the three packs getting progressively further apart regarding their individual SOC % (State of Charge). It got serious a month ago when we had several days of wet weather, and two of the packs were showing about 45% SOC while one pack was only showing about 25% SOC.
I noticed that when the packs were being charged their BMS sent the highest SOC value of the 3 packs to the Growatt Inverter/Charger, (displayed on the inverter screen), but when they were discharging the BMS sent the lowest SOC value. This meant that I was not going to be able to use the extra storage that was in the two higher SOC packs when the inverter inevitably shutdown due to the minimum SOC alarm setpoint being reached, (set to 20% SOC).
It is impossible to get any sensible answers from the Delong Support people because none of the engineers speak English. Has anyone else encountered this SOC difference problem from the Delong battery packs before? I am also keen to find out how many of these new Delong 10kWh pack have been sold into NZ and Australia.
So, basically, your batteries are not being top-balanced during charging due to the battery with the highest SOC controlling the charging. Very strange
Most professional battery systems have a master battery or master BMS that is able to balance all individual batteries (and cells) and provide a universal SOC to the inverter. This is one reason why they cost more.
Is the BMS internal or external? Can you provide photos of the setup? I’ve never heard of Delong
Hi Svarky, thanks for your response.
The battery packs are individually stand-alone, that is, you could use a single one on its own, or stack up to five vertically, all interconnected with parallel loops, and a single pair of wires running to the inverter/charger. See this below link to DelongTop.
On the Home page, mine is the one on the bottom right-hand corner which shows 5 stacked, but I only have a 3 stack, (30kWh).
Each pack has its own internal BMS balancing the 16 x 200Ah cells, and its doing that job really well, (apart from a major problem when they first arrived, but I won’t address that here). Each pack must have its own CT’s and it continuously adjusts its own SOC% based on what current is passing in and out of its own pack. They each have different CAN node addresses, mine are set to 1, 2, and 3, and they have a serial loop connecting them all together. Only Pack 1 is connected to the inverter/charger via a Cat.5 cable presumably running a CAN protocol. So Pack 1 acts as the master of the 3 packs as far as the inverter/charger is concerned, and as I said in my first post, I have watched the charger display panel reading the highest pack SOC% during charging, and the lowest of the 3 packs when discharging.
Because they are all wired in parallel, when there is no current in or out they have exactly the same voltage reading, (can’t be different of course). So as far as I can see, if any one pack hits its maximum allowed charging voltage (set to 57.6v), they should all reset whatever SOC% they are currently reading to 100%. This would make them “self-calibrating” and it would occur at every full charge, (ie, on most days).
I have tried to get this message through to the engineers at Delong, but since they only understand Chinese and I just use Google translate for my emails, I am getting no proper responses from them. I have been programming PLC’s for the last 32 years and I reckon I could do a much better job than they have to ensure that the SOC% don’t steadily diverge from each other.
By the way, that Delong graphic and the wordage was automatically added by the post system, not by me. At this stage I personally wouldn’t entirely agree you the words that have appeared there.
I bought 10x Delong Rack Batteries 2 years ago and they started going out of balance and then pretty much completely failed after 18 months.
Some cells in them had gone much higher resistance than others and had even swollen, distorting the case of the rack battery! They advertise 10 year warranty but are refusing to honour any warranty for me.
For anyone else looking at Delong/Delongtop batteries - steer clear!
Wow, that is scary mate. I haven’t had any problems with the packs balancing internally, I mean between the 16 cells in each pack. That is the individual BMS’s have been working perfectly. My problem is pack to pack, not cell to cell.
You say “rack-mounted” so are they the LFP-BE51100 type? ie; 48v 5kWh rack-mount?
Hi, I’m in UK with 3x10kWh hl51200 batteries. Mine were not behaving as expected storing only about 7kWh each. Someone advised me to get an update ferry for the bms, I have done that and they are now behaving as expected. I haven’t been monitoring the voltages of the packs, I might start now. Initially I would agree that delong were unhelpful, but when I asked them for the update they were good,
Hi John
I wasn’t able to upgrade my BMS firmware, I think maybe it was because I might have received an earlier version of the hardware. I currently have the files: P1547V200-21382-1.01T-002.bin installed. Do you have a later version than that installed?
I am also interested in what Inverter/Charger brand and model that you have installed? Mine is a Growatt 5kW. Does your inverter display show the HIGHEST of the three pack SOC% when Charging, and the LOWEST of the three packs when Discharging?
Paul, to ensure that we are talking about the same batteries, the user manual I have with them calls them, LFP HS51200-10
My inverter is a Sunsynk Hybrid inverter Model No: SYNK-5K-SG04LP1
Regarding the reported SOC it rounds this to the nearest whole percent, and it shows the same value charging and discharging. I checked this tonight.
The battery packs(2) show voltages that are equal to within 0.02 volts and this seems to stay the same as they rise during charging.
So to the info you really want…
The firmware delong sent me is P1547V300-21382-3.02T-001
The reason I wanted to update was that for a year the batteries never stored more than 14-15kWh of charge, the UK supplier had gone bankrupt just after installing my batteries.
So I am happy at present, and have just received a third pack direct from China. I will be installing this soon.
Delong tech support were fairly useless, but another UK user had updated his BMS firmware for another reason and it seemed a good idea to me. Helen at delong in sales I think, was helpful and sent me the files, loader and instructions. She is on WhatsApp +86 166 2087 5194
If you like I can send you the files. But I would check with delong that they are the correct ones, Helen asked me for the purchase date before she sent me the files
Hi John
Delong sent me that 3.02 version and I was unable to install it. Then after multiple emails and teeth gnashing at my end, they informed me that because my version of the BMS hardware was so old, it would not be able to be updated to the 3.02 version, and the latest that I could use was 1.01. I asked them to send me three new BMS boards so that I could update to 3.02, and initiating they agreed to send one only, (not much point when I have THREE 10kW packs), then they reneged on the offer. I think they are a real “back-yard” mob, and unfortunately it wasn’t a good idea to be a “beta tester” for them.
I’m interested to hear that you see the same SOC reported on your brand of inverter/charger in both Charging and Discharging. …cont’d
…cont’d. That my SOC% reported on the Growatt Inverter/Charger (lowest during Discharge and Highest during Charging), is probably a bug in the Growatt side. I might try and get Growatt support to look at that, (I don’t fancy my chances though).
Re the Voltages on the packs: they can’t be different if they are all connected in parallel. There can be only one pack voltage. You’ll see a heap of current passing between the packs if you turn one on when it has a different voltage to the other ones.
Make sure you have the voltages pretty close before attaching the new one to the existing two. The trick that I have used is to fully charge the first two, then turn them off, change the new one’s node address to 1 and attach the inverter’s CAN cable to it, then turn it on. When it’s also fully charged, turn them all off and change the node addresses to 1, 2, 3 in the order that you want them and move the CAN cable to the one that is set to “1”. Turn them all on, and you will notice a small amount of current passing between them until they settle out.