LV5200 charge & discharge rate limits

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jerryhawkins
Posts: 14
Joined: Wed Mar 08, 2023 6:03 pm

Similar to another thread here. I have 4 x LV5200 batteries and a Solis 6kw hybrid inverter. I experienced the low charge rates as others have due to low temperatures (3-5 deg C), so I now have an insulated, temperature controlled enclosure around the batteries keeping them at a nice warm 21-25 deg C. Looking at the data on the Solis cloud, allegedly from the BMS, the charge and discharge limit is now showing as 100A for both. This only represents 0.25C, so well within the batteries specification and the most the inverter could supply for charging. The problem I have is that something is still restricting both charge and discharge to 50A. This means that if the batteries are very low, they can't fully charge in my off-peak tariff window and also, if my house load exceeds 2.5KW (when no solar) then the balance is imported from the grid. I shouldn't need to import until I need more that 5KW. I've looked at the various inverter settings; some seem to be 'set' by the BMS and can't be changed, others are set to 100A for charge and discharge. Has anyone else seen this behaviour or able to offer any advice? I have raised a 'ticket' with Solis support and am waiting to see what they come back with. Thanks, Jerry
Dave Foster
Posts: 611
Joined: Thu Oct 13, 2022 7:21 pm

I’m not sure i’m going to be able to help much, but the LV5200 should be rated at 100A charge/discharge at those temperatures.

Looking at the LV5200 manual, it shows that the discharge curve ramps down gradually to 50A once the SoC falls below 30% to 20%, and then holds at 50A from 20% until 10% (minsoc) that would be around the 2.5kw you mention if? the soc was low when you observed that.

As to the charging, the BMS obviously can throttle the charge if temperature is low and i’ve heard of it slow charging at the 18C mark, and then picking up as the batteries warm up.

The one thing to say about the reported battery temperature is that it is an average of all cells over all packs so the ones nearer the floor/cold wall etc.. can be much lower than the average reported and so the BMS could be throttling charge even though they look to be in range.

It would be good to hear what Solis support say, probably worth a call to Fox UK support as well if you’re not getting any joy.
jerryhawkins
Posts: 14
Joined: Wed Mar 08, 2023 6:03 pm

Hi Dave,
Thanks for your reply. Before I sorted the battery heating, the SOC when overnight charge started was between 20 & 30%, so that could have been a factor. The last two or three days, post heating, the SOC at start of charge was over 40%, so shouldn't be a factor. The batteries are sitting on the 'cold' concrete garage floor so, as you say there could well be a differential between the warmest and coldest cell which may affect things. I'm still waiting to hear from Solis support - it's odd that the BMS charge & discharge limit reported via the 'Solis cloud' is 100A, whereas the 'control settings' in the inverter UI itself shows these as both 50A. I can't set these as they allegedly are set/updated by the BMS. The joys of software control!
Dave Foster
Posts: 611
Joined: Thu Oct 13, 2022 7:21 pm

I have the Fox HV batteries in a stack, right now my battery temp is showing 20.2C, whereas the high and low cell limits are showing as 20.7C and 12.1C so quite a variance across the pack.

I'm not sure how good the Solis integration is but the FoxESS BMS does have an internal BMS Charging/Discharging sensor which dynamically changes as the SoC / temperature changes, although from what you have said, it does tend to sound like the Solis is the limiting factor if it is setting 50A limits, be great to hear how you get on with them.
jerryhawkins
Posts: 14
Joined: Wed Mar 08, 2023 6:03 pm

Been a while, but just to conclude this thread...

It was the 'control parameters' 'charge limitation' and 'discharge limitation' on the Solis inverter that were imposing the 50A limit. I was unable to set these myself, but I've eventually managed to get Solis support to remotely set these to 100A. They emailed me this morning to say they'd been set; checked the inverter and sure enough they were both showing 100A. Nice bit of sun now too and max battery charge current I've seen is 64A (before they hit 100% charge), so we're past the previous 50A limit and looking good!

Cheers,
Jerry
Dave Foster
Posts: 611
Joined: Thu Oct 13, 2022 7:21 pm

jerryhawkins wrote: Mon Mar 27, 2023 11:10 am Been a while, but just to conclude this thread...

It was the 'control parameters' 'charge limitation' and 'discharge limitation' on the Solis inverter that were imposing the 50A limit. I was unable to set these myself, but I've eventually managed to get Solis support to remotely set these to 100A. They emailed me this morning to say they'd been set; checked the inverter and sure enough they were both showing 100A. Nice bit of sun now too and max battery charge current I've seen is 64A (before they hit 100% charge), so we're past the previous 50A limit and looking good!

Cheers,
Jerry
Excellent, that's a great result - and thanks for the update, very helpful for the next person suffering the same problem ;)
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