Hi everyone,

I joined the solar world by the end of 2021 and am still super happy about the investment we made.

While watching the SolarAssistant charts and graphs, I see that our inverter (it's a Sunsynk 5kWh) discharges the Hubble AM2 battery to less than 80%, although the timer settings on the inverted do basically say "charge under 80%". See screen grab here:

And here, on the chart side of things, you can see that it discharges quite quickly down to ~80%, but then keeps consuming the battery for much longer, basically until the sun kicks back in at ~8am:

And last screen grab, here, you can see that the battery is being discharged at night time, despite it being already under 80%:

My question: Is it normal that the battery keeps discharging [at a low level] throughout the night, or is there something wrong with my system?

Thanks so much for your expertise – and your thoughts,
Marc

 

Would like to know why you wish to keep your battery above 80% SOC.

Within your first screenshot where you have set your power management, I see there are tick boxes. Shouldn't you tick them to ensure that your batteries will be charged by grid or generator to keep them at 80% or above?

Hi @zsde,

Thanks for your reply.

I'm staying above 80% SOC because the battery isn't big enough to cover more then ~3-4 hours of load shedding, while our household relies a lot on being online for work. Therefore, I tried to keep the battery full enough to cater for load shedding situations. Is this a really bad idea –– or why did you ask?

Secondly, I don't really want to charge the battery from grid, if I can avoid it. My idea is to charge the battery while there is sun, and use it at night, when the sun is down. As mentioned, the battery is (by far) not big enough to get us through the whole night, but again, that's why I'm not letting it go down all the way.

To add another graph, this is a view of the last 24 hours –– including grid power (red), load power (blue) and the two MPPT solar inputs (yellow):

Also, I am currently thinking of getting a second Hubble AM2 battery so I could allow the discharge to go lower, without risking not having juice in the battery for load shedding moments. Any suggestions on this? I was going for a second 5.5kWh battery, making it 200Ah.

Thanks,
Marc

Edited March 21, 20224 yr by MarcFe

I understand. Looking at your first set of screenshots your battery went down to around 55% overnight and then the solar started charging it again. So that is not excessive.
I am sitting with the same battery usage and management scenario as you. Only one battery but it has been sufficient up to now.
So if you wish to keep it at 80%, then there is no alternative but to use grid power to charge them during the night.
The battery will discharge even if you switch off everything. The Inverter itself consumes around 50W.
Something else that I noticed on your first set of screenshots is around 50V Solar on both MPPTs during nighttime. Where do your solar panels generate that voltage from at night? 
After sunset mine drop to zero as expected. 

Edited March 21, 20224 yr by zsde

Hi Marc,

Have a look at these two topics as they may well help you with your Time of Use settings and getting your thoughts right about how to use your system.

Even though you only have one battery at this time, you should still be using it overnight to capitalise on your investment in using solar to charge it up during the day.

I too used my system as a UPS in the beginning because loadshedding had just hit badly at the time. It was only after that round subsided that I started with using the battery overnight. Initially the first single battery got us through from 12 midnight to when solar started charging in the morning. Decided then to by a second battery and we now use the batteries to run the house from 8pm to the next morning.

Hope this helps.

MdF

 

 

 

 

1 hour ago, zsde said:

I understand. Looking at your first set of screenshots your battery went down to around 55% overnight and then the solar started charging it again. So that is not excessive.
I am sitting with the same battery usage and management scenario as you. Only one battery but it has been sufficient up to now.
So if you wish to keep it at 80%, then there is no alternative but to use grid power to charge them during the night.
The battery will discharge even if you switch off everything. The Inverter itself consumes around 50W.
Something else that I noticed on your first set of screenshots is around 50V Solar on both MPPTs during nighttime. Where do your solar panels generate that voltage from at night? 
After sunset mine drop to zero as expected. 

Hi @zsde,

Good question, and well spotted! I don't know how my solar peaks show 50V throughout the night, to be honest. But looking at the seven-day charts, it does indeed seem a bit odd: 

I just updated the Solar Assistant software, hoping that it was a bug (once it showed me the battery temperature * 10 for a while –– and I wasn't in the country, hence thought my battery is about to burn –– until I figured out that the softwared needed updating, and it therefore was only showing all temps with factor 10. Ha!)

Anyway, whoever knows why this could be the case, let me know.

And, to make sure it's not a bug of the SolarAssistant software, here's a screen grab from the SOLARMAN app on my phone, which is part of the same system. It also shows the ~50V over night:

2 hours ago, MdF said:

Hi Marc,

Have a look at these two topics as they may well help you with your Time of Use settings and getting your thoughts right about how to use your system.

Even though you only have one battery at this time, you should still be using it overnight to capitalise on your investment in using solar to charge it up during the day.

I too used my system as a UPS in the beginning because loadshedding had just hit badly at the time. It was only after that round subsided that I started with using the battery overnight. Initially the first single battery got us through from 12 midnight to when solar started charging in the morning. Decided then to by a second battery and we now use the batteries to run the house from 8pm to the next morning.

Hope this helps.

MdF

 

 

 

 

Hi @MdF,

Thanks for this, I found the posts useful, indeed. One thing I need to make sure is that there is enough power in the battery for the (solar) geyser to top up on electricity if there is load shedding between 4am and 6am –– as we have tenants who want to have hot water for their showers when they get up.

I'm currently quite happy having 80% SoC around the clock, though. Over the daytime, the solar panels (~5kW in two arrays) feed the inverter with enough power to charge the battery and run the house at the same time, even on a cloudy/rainy day. So once the sun goes down, the battery discharges to 80%, and eventually ends up at 55-65%, before it gets filled up by sunlight again.

But still, I'd love to have another battery – and more storage – as it seems that the rest of the system is stronger than what I can store, and it could perhaps make us go through all night on a regular day, if I'd then also set the SoC allowance further down, let's say to ~50%, having 200Ah storage capacity.

Also, reading the articles you mentioned, I gather that the lifespan of the battery is long when only charged down less far. I was actually wondering how the Lithium batteries work, I heard that also having them charge all the way to 100% isn't necessarily good for all type of Lithium batteries, either?

Thanks!

4 hours ago, MarcFe said:

My question: Is it normal that the battery keeps discharging [at a low level] throughout the night, or is there something wrong with my system?

As @zsde already wrote, the self-consumption of the inverter is powered from the batteries - even if the system is running on grid

1 hour ago, MarcFe said:

But still, I'd love to have another battery – and more storage – as it seems that the rest of the system is stronger than what I can store, and it could perhaps make us go through all night on a regular day, if I'd then also set the SoC allowance further down, let's say to ~50%, having 200Ah storage capacity.

Agree that your system is over-paneled and adding more batteries would help better balance the system (help get more out of your system). On your screenshot above, your battery is fully charged by 09h00 again, and after that your panels only have to power your loads. So for most of the time, you only draw 1kW from your 5kW of panels

1 hour ago, MarcFe said:

I heard that also having them charge all the way to 100% isn't necessarily good for all type of Lithium batteries

I'm not a technical expert, but to my understanding when you cycle through your batteries on a regular basis, then it is ok to charge them to 100%. It is only when hardly drawing from them (e.g., a laptop battery when the laptop is always used connected to AC), then leaving the battery at a lower SOC will help extend the life.

I am drawing my set of Pylons down to 25% every night

36 minutes ago, wolfandy said:

As @zsde already wrote, the self-consumption of the inverter is powered from the batteries - even if the system is running on grid

Agree that your system is over-paneled and adding more batteries would help better balance the system (help get more out of your system). On your screenshot above, your battery is fully charged by 09h00 again, and after that your panels only have to power your loads. So for most of the time, you only draw 1kW from your 5kW of panels

I'm not a technical expert, but to my understanding when you cycle through your batteries on a regular basis, then it is ok to charge them to 100%. It is only when hardly drawing from them (e.g., a laptop battery when the laptop is always used connected to AC), then leaving the battery at a lower SOC will help extend the life.

I am drawing my set of Pylons down to 25% every night

Hi @wolfandy,

Thanks for your reply.

Agreed on all you're saying, I'd like to be using my battery (batteries) further down, too. And, having more Ah capacity, I think I'll be able to cater for load sheddings without keeping the SoC as high as 80% –– given the system (as you mentioned) charges the batteries by 9am every morning.

And yes we're barely drawing enough power from the panels, since the geyser is already on solar and our household is fairly optimised for low consumption. In any average moment, I'd say we're using ~500W, with peaks going up to 4.5kW. Nothing that the inverter couldn't handle.

Cool thanks, I'm going to buy a battery, then! 🔋

On 2022/03/21 at 1:03 PM, MarcFe said:

Hi @zsde,

Thanks for your reply.

I'm staying above 80% SOC because the battery isn't big enough to cover more then ~3-4 hours of load shedding, while our household relies a lot on being online for work. Therefore, I tried to keep the battery full enough to cater for load shedding situations. Is this a really bad idea –– or why did you ask?

Secondly, I don't really want to charge the battery from grid, if I can avoid it. My idea is to charge the battery while there is sun, and use it at night, when the sun is down. As mentioned, the battery is (by far) not big enough to get us through the whole night, but again, that's why I'm not letting it go down all the way.

To add another graph, this is a view of the last 24 hours –– including grid power (red), load power (blue) and the two MPPT solar inputs (yellow):

<SNIP>

Also, I am currently thinking of getting a second Hubble AM2 battery so I could allow the discharge to go lower, without risking not having juice in the battery for load shedding moments. Any suggestions on this? I was going for a second 5.5kWh battery, making it 200Ah.

Thanks,
Marc

As @zsdeshowed you need to select Grid Charge

How this works:
During day, will use solar to charge to 100%
During night, will discharge to 80% then switch to grid.
During load shedding will discharge to value set in shutdown screen (my shutdown is set to 10%).
After load shedding. when power returns (at night) will use grid to charge back to 80%.

If you battery is currently below 80%, it will use grid to charge to 80%.

EDIT: This is my shutdown settings

EDIT2:
From 5.11 in the manual:

I think this Grid Charge overrides Work Mode Timer Grid Charge.

Edited March 24, 20224 yr by system32
More info

On 2022/03/21 at 12:45 PM, MarcFe said:

Hi everyone,

I joined the solar world by the end of 2021 and am still super happy about the investment we made.

While watching the SolarAssistant charts and graphs, I see that our inverter (it's a Sunsynk 5kWh) discharges the Hubble AM2 battery to less than 80%, although the timer settings on the inverted do basically say "charge under 80%". See screen grab here:

And here, on the chart side of things, you can see that it discharges quite quickly down to ~80%, but then keeps consuming the battery for much longer, basically until the sun kicks back in at ~8am:

And last screen grab, here, you can see that the battery is being discharged at night time, despite it being already under 80%:

My question: Is it normal that the battery keeps discharging [at a low level] throughout the night, or is there something wrong with my system?

Thanks so much for your expertise – and your thoughts,
Marc

 

Hi, I know this is an old thread, but just thought I'd add my 2 cents, hoping it will benefit others.

I'm kinda new to solar/inverters. Got my Deye inverter installed just under 3 weeks ago. 8kw inverter, and 4× hubble am5 batteries. Sounds like overkill, but figured I'd just bite the bullet, since it's best for the long run. Deep discharge cycles dramatically reduce the battery's life expectancy. If you can keep the battery between ~50% and 100% charge, it works wonders for longevity. 

Once you start draining your batteries deeply, it starts a vicious cycle, of needing to continuously deep-drain your batteries, as each deep discharge, will decrease capacity.

Just thought I'd put this out there.

What I really wanted to mention, is regarding those "grid charge" checkboxes, on the "work mode timer". 

Let's say your battery is at 81%, and there's no load shedding. When it drops to 80%, the grid will maintain the 80% charge. So long as there's no load shedding, throughout the night, given that you set the state of charge at 80% throughout the night, the inverter will use grid power to maintain that 80% charge.

But let's say there's load shedding from 20:00 to midnight, and let's assume that your battery was on 90% before load shedding commenced at 20:00. By the time it's midnight, and load shedding stops, your battery level might be around 65%. So when grid power is back, it will maintain that 65% charge. It won't recharge the battery back to 80%, because the "grid charge" checkbox, isn't ticked.

But if the grid charge checkbox was ticked, at the 00:00 to 04:00 time slot, then your battery would have been charged back to 80%, and the inverter would maintain that charge, until either another load shedding session, or your solar panels kick in, in which case, your battery will be charged back to 100%.

So it's all a balancing act. I'm still tweaking my timer settings, but I'm getting the hang of what works for my household. When winter sets in, and we start using heaters, that will be the real test, since the ladies don't wanna use gas heaters. But 800w bar heaters, used intermittently, should be manageable enough.

Here's how my timer is currently set:

01:00 to 05:00   65%  grid charge

05:00 to 09:00  55%  grid charge

09:00 to 13:00  60%

13:00 to 17:00   65%

17:00 to 21:00   70%  grid charge

21:00 to 01:00   65%  grid charge

 

It's set to basically never need to grid charge at all, but if for some reason, the battery percentages do drop below the limits I set, the grid will only need to charge them for a very short while, till we enter the next time slot, and the battery again begins to discharge.

Recently, we had a load shedding slot from 04:00 to 06:30, where the battery level dropped to 48%, hence I set the grid charge, for the 05:00 to 09:00 time slot. It's Ramadaan right now, so we wake up before sunrise, use the microwave, kettle, etc. So there's some significant battery drain in those early hours of the morning. 

Basically, I just need to grid charge to maintain a certain percentage, until sunrise, and the solar kicks in, then I'm generally back to 100% charge by midday, if the sun is shining. My inverter is set to prioritise the load, before charging the battery.

It's just around 23:50 as I'm typing this, and the battery level is at 75%. I'm hopeful that there will be no need to grid charge at all, throughout the night, but it's generally a close call, around 6AM. The battery might near the 55% mark around that time, but I'm hoping it will still be above 60%, in which case, I probably won't need to grid charge at all, until the solar kicks in, God willing.

Sorry for typing so much. For what it's worth, hope whatever I said is helpful. 

Edited March 27, 20233 yr by SuperCwazy
Some minor corrections and additions

7 hours ago, SuperCwazy said:

Hi, I know this is an old thread, but just thought I'd add my 2 cents, hoping it will benefit others.

 Deep discharge cycles dramatically reduce the battery's life expectancy. If you can keep the battery between ~50% and 100% charge, it works wonders for longevity. 

Yes for lead acid batteries but not so much for lithium. We have to unlearn and adapt to the new tech. 

17 hours ago, Scorp007 said:

Yes for lead acid batteries but not so much for lithium. We have to unlearn and adapt to the new tech.

While lithium ion batteries can be consistently drained all the way to 90%, they don't like deep discharges. Frequent charges, keeping them around the 50% capacity mark, is best. 

I might be new to inverters, but I've got years of experience with lithium ion batteries. To give you a practical, real life example. We got a UPS device, just around 4 months back, to power our WiFi router during load shedding. Initially, we got a solid 3,5 hours out of it. Prior to getting the inverter, we were getting no more than 2 hours out of it. It's a LiPo, and while they're designed for long service life, those stage 6, four hour load shedding cycles, caused it to deteriorate very quickly, since it was being fully drained.

I can give you many examples, even with lithium polymer inverter batteries, since I have friends and family who've been using them for some time. Deep discharges cause them to lose capacity very quickly.

Please give this a read.

https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries

 

Edited March 28, 20233 yr by SuperCwazy
Typos

6 hours ago, SuperCwazy said:

While lithium ion batteries can be consistently drained all the way to 90%, they don't like deep discharges. Frequent charges, keeping them around the 50% capacity mark, is best. 

I might be new to inverters, but I've got years of experience with lithium ion batteries. To give you a practical, real life example. We got a UPS device, just around 4 months back, to power our WiFi router during load shedding. Initially, we got a solid 3,5 hours out of it. Prior to getting the inverter, we were getting no more than 2 hours out of it. It's a LiPo, and while they're designed for long service life, those stage 6, four hour load shedding cycles, caused it to deteriorate very quickly, since it was being fully drained.

I can give you many examples, even with lithium polymer inverter batteries, since I have friends and family who've been using them for some time. Deep discharges cause them to lose capacity very quickly.

Please give this a read.

https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries

 

Thanks for sharing a great link. This was my reference in another post but I could not find it when looking on the Web site. 

Is there any way on the sunsynk to get the inverter to charge the batteries to a maximum percentage of say 80%, thereafter feed the remaining pv back into the grid? Currently only possible at 100 % SoC as far as I know? 

7 hours ago, SuperCwazy said:

While lithium ion batteries can be consistently drained all the way to 90%, they don't like deep discharges. Frequent charges, keeping them around the 50% capacity mark, is best. 

I might be new to inverters, but I've got years of experience with lithium ion batteries. To give you a practical, real life example. We got a UPS device, just around 4 months back, to power our WiFi router during load shedding. Initially, we got a solid 3,5 hours out of it. Prior to getting the inverter, we were getting no more than 2 hours out of it. It's a LiPo, and while they're designed for long service life, those stage 6, four hour load shedding cycles, caused it to deteriorate very quickly, since it was being fully drained.

I can give you many examples, even with lithium polymer inverter batteries, since I have friends and family who've been using them for some time. Deep discharges cause them to lose capacity very quickly.

Please give this a read.

https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries

 

That article seems to be mainly focused on NMC chemistry and the info does not seem very accurate when comparing cycles. I would recommend actual research papers for proper information. Here is an example.

https://iopscience.iop.org/article/10.1149/1945-7111/abae37

19 hours ago, Nexuss said:

That article seems to be mainly focused on NMC chemistry and the info does not seem very accurate when comparing cycles. I would recommend actual research papers for proper information. Here is an example.

https://iopscience.iop.org/article/10.1149/1945-7111/abae37

Thanks for the link. I was actually just reading up more about this last night, and realised that LiFePO4 batteries are actually quite a game changer, and far less impacted by deep discharges, compared to other lithium ion chemistries.

That being said, even with LFP batteries, they still give a much longer cycle life, if not discharged too deeply. If you keep them above 50% SOC, you can effectively triple their cycle life. 

I came across some interesting info in this regard, on the BSL battery website, but couldn't find it when I searched for it again. But basically, they encouraged shallow discharges, as the cycle life increases exponentially, the shallower the discharge cycles get.

At 30% DoD, you get insane longevity, but at the cost of practicality. I think keeping your DoD at around 50%, seems to be striking a good balance.

We actually had a power outage today, with no grid power from like 3pm to 9pm, so I keep learning more, what works best, as we go long.

These are my amended timer and battery settings. Hopefully I've found the sweet spot now, where I can just let things be, without needing to do any further tweaking.

01:00 to 05:00   50% grid charge

05:00 to 09:00  50%  grid charge

09:00 to 13:00   50%

13:00 to 17:00    60%

17:00 to 21:00    70%  grid charge

21:00 to 01:00    60%  grid charge

 

Restart  35%

Low battery  30%

Shutdown  25%

Edited March 30, 20233 yr by SuperCwazy
Typos and amendments

16 hours ago, abd7 said:

Is there any way on the sunsynk to get the inverter to charge the batteries to a maximum percentage of say 80%, thereafter feed the remaining pv back into the grid? Currently only possible at 100 % SoC as far as I know? 

Unfortunately, there's no way to limit the SoC, when charging with solar, as far as I know. I was interested in exactly the same thing. Was hoping to let my batteries charge to 90% only.

But if you've got multiple batteries, letting them charge to 100% is a good thing, since it keeps them balanced. 

In SA, as far as I know, we can't sell power back to the grid. At least not here in Joburg. Perhaps Cape Town is an exception? I highly doubt it though. I don't think we have the infrastructure for that.

Would be cool if we did though. The bulk of our solar production, for the better part of the afternoon, is totally wasted. 

Edited March 29, 20233 yr by SuperCwazy
Minor corrections

Hey guys, I found a really interesting article which isn't too technical, makes for rather easy reading, and is perfect for the layman to understand. 

https://www.solacity.com/how-to-keep-lifepo4-lithium-ion-batteries-happy/

 

Edited March 30, 20233 yr by SuperCwazy
Removed unnecessary info

9 hours ago, SuperCwazy said:

Hey guys, I found a really interesting article which isn't too technical, makes for rather easy reading, and is perfect for the layman to understand. 

https://www.solacity.com/how-to-keep-lifepo4-lithium-ion-batteries-happy/

 

Interesting that the battery manufacturer reverts to balancing 12V batteries by charging the one with lower SOC instead of just mentioning a battery balancer can be used. 

Further they mention that lead acid in series would balance each other so no need for balancing between them. 

Why have we been using balancers on lead acid? 

Thanks for the link. 

On 2023/03/27 at 10:56 PM, SuperCwazy said:

 

Let's say your battery is at 81%, and there's no load shedding. When it drops to 80%, the grid will maintain the 80% charge. So long as there's no load shedding, throughout the night, given that you set the state of charge at 80% throughout the night, the inverter will use grid power to maintain that 80% charge.

.

But if the grid charge checkbox 

Here's how my timer is currently set:

01:00 to 05:00   65%  grid charge

05:00 to 09:00  55%  grid charge

09:00 to 13:00  60%

13:00 to 17:00   65%

17:00 to 21:00   70%  grid charge

21:00 to 01:00   65%  grid charge

 

 

Just to clarify:

- in the 1am to 5am slot, you will use your battery until 65%. Once it goes under 65% the grid kicks in and keeps it at 65%. Unless there's loadshedding in which case it keeps on going down till shutdown. 

- in the 09h00 to 13h00 slot: similarly you will use your battery until 60%, and if it goes under 60% the panels will kick in (you don't have grid ticked). But if panels are meant to keep the SOC at 100% anyways, why is it necessary to specify 60% (seeing that the panels will charge it irrespective to 100%)? Or am I misunderstanding the entire concept? 

Thanks! 

Panels work all the time when they can... If its cloudy or raining, and panels cannot supply enough power, then that setting is so the battery will provide power as well, till it drops to 60%. Then grid will take over 

Edited March 30, 20233 yr by abd7

2 hours ago, Solarmaxi said:

Just to clarify:

- in the 1am to 5am slot, you will use your battery until 65%. Once it goes under 65% the grid kicks in and keeps it at 65%. Unless there's loadshedding in which case it keeps on going down till shutdown. 

- in the 09h00 to 13h00 slot: similarly you will use your battery until 60%, and if it goes under 60% the panels will kick in (you don't have grid ticked). But if panels are meant to keep the SOC at 100% anyways, why is it necessary to specify 60% (seeing that the panels will charge it irrespective to 100%)? Or am I misunderstanding the entire concept? 

Thanks! 

The percentages in the 09:00 to 13:00, and 13:00 to 17:00 slots, are irrelevant. I could have just put any percentages in there, and it would have made no real difference, since solar is active in those hours, and generally charges it up to 100% anyway.

But if it was a really dark, rainy day, and solar was charging slowly, and I put really high percentages in those time slots, like say 95%, then it would probably have used the grid to charge (If I ticked grid charge, for those time slots, but I didn't) So I just kept the percentages low, and let solar do its thing. Thing is, I know that the battery SoC at those times, will be higher than 50% and 60%, respectively. The battery is already at ~100% by midday. Even on a rainy day, it should be over 70% by 13:00. Guess I could have put in lower percentages, to play it safe.

Thing is, I can't leave any fields blank. I'm forced to put in some %, so I just put in %'s which gave the fields some symmetry (I'm moderately OCD about symmetry). But you'll notice, I didn't tick "grid charge", during those time slots.

I actually amended the times again today. I've been in communication with the technical guys at Hubble, and they told me that I should do a full discharge, at least once every 30 charges, to keep the batteries functioning optimally, and ensure maximum longevity. I asked them if a full discharge meant draining them down to 20%, but I'm still waiting for their reply on that. So I decided not to worry too much about the timer settings, and just let things be for now. If it sometimes drops below 50% SoC, I figure it's not that big a deal.

My latest settings are as follows:

01:00 to 05:00   50%  

05:00 to 09:00   50%  

09:00 to 13:00   50%

13:00 to 17:00   50%

17:00 to 21:00   50%  

21:00 to 01:00   50%  

 

Restart    40%

Low batt   30%

Shutdown  25%

If you notice, I haven't selected grid charge at all. The only times my batteries will effectively be near the 50% SOC mark, will be around 05:00 to 09:00

As it's currently set, so long as there's no load shedding 04:00 or 06:00, my inverter should maintain the 50% SoC. But if there is load shedding, say at 04:00 to 06:30, its likely my SoC will drop below 50%, by the time load shedding ends (which is generally at around 06:15), in which case, my inverter will just maintain whatever SoC the battery is at, at the time. And I'll just have to wait for solar to charge it up again, since I haven't ticked the "grid charge" checkboxes.

Let's see how it goes for a few days, and I'll hopefully try to give them a deep discharge after another week or so, as instructed by Hubble.

Although, I'm kinda on the fence about letting them discharge to 20% SOC. I mean, not like 20% is some magic number. Shouldn't draining them to 25% be good enough?

I've read many people advising not to discharge below 20%. So why not just give myself a bit of headroom, and discharge to 25% instead? Or 30% maybe?

Anyway, let's see what reply Hubble gives me later today. For now, I remain on the fence about this issue. The batteries should equalise, when they reach 100%. I don't see the real need to drain them to 20%, since you can drain them below level that too. I just don't see why 20% is the magic number, to preserve the cells. Why not 15%, or 25%? I know it has to do with the voltages, corresponding to those percentages, but I still don't see what makes 20% the magic number.

Sorry for rambling. Hope everything I said was understandable.

Addition 

Just for the sake of thoroughness, here's what the tech guys at Hubble had to say, when I asked about the max charging amps, and whether draining the batteries down to just 50% SoC would increase their longevity:

"For the Deye inverter, we recommend a Max Charge Amp of 50A per battery. Below 100A will increase the lifespan of the battery.

We recommend 20% SOC discharge on all Hubble Lithium batteries and 100% SOC recharge to reach bottom and top balance." 

 

I then asked if it will be a problem if my batteries don't reach 20% SOC, since the most they generally drain to, before solar kicks in, is around 40%, and this is what they had to say:

 

"No it will not negatively impact the battery, provided you do a full discharge at some point. To ensure, battery longevity, It's recommended after every 30 charges, you should allow your lithium based battery to completely discharge before recharging. This preserves the cells and increases its lifespan."

 

Edited March 30, 20233 yr by SuperCwazy
Typos, amendments and additions

Another interesting article, confirming what the Hubble technicians mentioned, about fully discharging lithium ion batteries, after every 30 charges

https://northeastbattery.com/prolong-lithium-battery-life/

Although I'm still uncertain to what percentage I should allow them to discharge. Is 20% SoC a full discharge? Unfortunately, Hubble technicians didn't reply to my question, in this regard.

But let's see what happens tonight, since we're having load shedding from 04:00 to 06:30. It's 1:30am right now, and SoC is already 57%. It's likely gonna drop below 40% by the time load shedding ends. 

We had overcast weather all day yesterday, some rain last night, quite cold too. Solar charged the batteries to less than 85% during the day, plus load shedding, family using heaters, appliances, etc, hence the low SoC at present.

It's just over 3 weeks since we've had the inverter, so perhaps it's an opportune time for a full discharge. 

My timer settings are still exactly as per my last post. Inverter Set to restart at 40%, low battery at 30%, Shutdown at 25%.

Let's see how low it drops, by the end of load shedding. Kinda doubt it will reach 25% though. Hoping it will drop to somewhere close to 30% by the time load shedding ends, and that it will qualify as a full discharge.

Keen to get your guys thoughts on doing a full discharge after every 30 charges. I'm not sure if this applies to LiFePO4 cells. I'm also aware that technicians are sometimes under the same misconceptions as others, due to reading the same source material, etc. So I prefer to do independent research, as opposed to taking what any 1 person says, as the Gospel, so to speak.

As I'm sure you guys can tell, I'm still learning and figuring things out. Just taking you all along on the journey with me. 

Addition

So I just adjusted my timer and battery settings as follows, to cater for tonight's venture

01:00 to 05:00   30%  

05:00 to 09:00   20%  

09:00 to 13:00   30%

13:00 to 17:00   40%

17:00 to 21:00   50%  

21:00 to 01:00   40%  

 

Restart    25%

Low batt   20%

Shutdown  15%

 

At 03:50 battery SoC is 52%. Load shedding to kick in at 04:00. Changed things since I didn't want the inverter to reset while I was away, for my pre dawn prayers. I'm sure the ladies will be using heaters, since it's a cold morning, so there's a chance the batteries will reach 40% SoC while I'm away. It was previously set to restart at 40%, but I changed it to 25% now.

 

Also it's just around 21 days since we installed the inverter. So it's not yet 30 days. I dunno if maybe I should have just waited a full 30 days, before trying the whole discharge thing. Not sure if it makes a difference.

 

The whole purpose of the full discharge, after 30 days, has to do with the BMS and battery calibration, which is software related, so I'm not sure if the 30 day figure, has added significance.

 

Apologies for rambling. It's 3:56 right now, and I've been up all night, lol. Hope this stuff is beneficial, and adds perspective for others.

 

Addition

 

Just to update you guys. So the battery still only ended up being discharged to around 40%, before the solar kicked in. I'll have to probably run the heater for a few hours or so, the day I decide to do a full discharge.

 

For now, reckon I'm just gonna leave the timer and battery settings as they are, and let things be. I was looking at the voltage charts, and the difference between 50% SoC and 40% SoC, is a matter of 0.2V, so I'm not gonna bother about keeping the level above 50%. I think if it sometimes drops to 40% or slightly lower, it might even be a good thing.

 

Of course I still intend to do the full discharge, every 30 charges or so. But I don't think it's something to stress too much about. It was just a recommendation, after all, and I figure, so long I do it, every so often, it should be fine, God 

willing. 

 

Another interesting link I came by:

 

https://revov.co.za/news/the-value-of-a-16-cell-vs-15-cell-lifep04-battery-configuration/

 

Just a little FYI, the Hubble am5 is a 51.2v 16 cell battery.

Latest update

As confirmed by Hubble technicians, a full discharge is down to 20% SoC.

Apologies for all my ramblings. For what it's worth, hope my posts were beneficial.

Edited April 6, 20233 yr by SuperCwazy
Additional info

Hi guys, just wanted to give you an update, for the sake of thoroughness. Hopefully it will be beneficial for others. It's definitely important for Hubble battery users to know.

Regarding doing a 100% to 20% SOC discharge, the Hubble technicians made it clear that if one doesn't do this, the warranty will be voided, so it has to be done at some point. They recommend doing it after every 30 charges to ensure longevity, but this is a recommendation, not a hard and fast rule.

One day, due to poor solar generation, the battery only reached around 70% SoC or something like that (I can't remember too clearly), so it managed to drain to 22% SOC before solar kicked in. I asked them if this would be good enough. Here's what they said:

"The battery has a digital memory so discharging the battery at 22% instead of the recommended 20% the memory of the battery will see the 2% as irrelevant and therefore the battery will not discharge fully. If its not discharged at 20% cell degregation will take place die due to the 2% and this will violate the warrantty of the battery. Kindly read your warrantty."

When I asked if it was OK if the battery only charged to 70% SoC, and then Drained to 20% SoC, they said:

"Please note it is of utmost importance for the battery to reach 100% SOC and discharge to 20%. 

There is no alternative way to go about doing this. "

The solution to my issue was rather simple. All I needed to do was drop the solar mains, so the battery didn't charge when the sun came up. By around midday, when it reached 19% SoC, I switched the solar mains on again.

I set the timer to grid charge the batteries that night, just to reach 70%, so that they could pull us through the night. The battery SoC was only 55% or so (with solar charging), by the time the sun went down. 

I also upped the charging wattage to 45 amps for that afternoon, but there wasn't very good sunshine, so it mostly charged at a lower corresponding wattage anyway. 

I set my timer settings to 20% SoC on all time slots, when I did the battery drain. Just remember to change them back when you're done.

Hope this info was helpful.

Edited April 27, 20233 yr by SuperCwazy
Corrections