EEVblog 1634 - 15kWh AERL LFP Home Storage Battery Install!

[EEVblog]

Installing a 15kWh AERL Life2 LiFePo4 solar home storage battery to my Deye inverter.
Thanks to Peter Watkinson from AERL, one of my long time viewers!
AERL were the first to invent and patent the Maximum Power Point Tracker MPPT used in all modern solar systems.
https://www.aerl.com.au/mppt-solar-charge-controller-history/
https://www.aerl.com.au/
AERL Life2 datasheet: https://www.aerl.com.au/wp-content/uploads/2024/05/AERL_LiFe2_Datasheet_REV_004.pdf
Deye manual: https://www.sunovagroup.com.au/wp-content/uploads/2023/12/SUN-3-6K-SG04LP1-AU-1.pdf
Australian Standard for Home Battery Installations: https://store.standards.org.au/product/as-nzs-5139-2019
LG Battery recall: https://www.lgessbattery.com/au/recall/recallnotice.lg

00:00 - AERL Life2 LFP Home storage battery installation
01:08 - Pre-wired 19" battery storage rack
03:23 - 4AWG cables, quick-connects and bus bar
05:03 - The old EEVblog garage lab!
05:19 - Rate my Home Assistant RPi setup
05:43 - Peter Wilkinson from AERL
06:21 - The first patented MPPT from 1984
07:49 - LFP battery management PCB
08:14 - The 5.1kWh Life2 LiFePo4 LFP Battery
08:30 - LFP vs NMC fire risk and battery safety
10:16 - Is it safe and legal to install in the gargage?
11:03 - The 19" battery rack
11:51 - How does the battery talk to the Deye hybid inverter?
12:42 - Feed-in tarrifs and battery viability
13:25 - Should you 100% cycle an LFP battery? And self managed batteries.
16:01 - Do the batteries load balance?
16:56 - Installation! (+ extra solar installer FAIL)
18:48 - The 35mm cable and crimping
20:59 - Wiring up the battery cabinet
21:48 - Installing the batteries in the rack
22:31 - First power-up smoke test
23:02 - Connecting the other batteries
24:55 - Re-connecting the grid
26:07 - The next day...
27:32 - How does the Deye inverter know about the Enphase Micro Inverters?
29:21 - Big load testing with the EV, oven, and aircon
31:17 - Conclusion



Part 2:

Full talk with Peter:

Bigger Battery:

[Dread]

Dave I caught your battery upgrade Video before it went MIA.
I was an EE for 30 Years and after retirement put in Solar at my House.  I do some advice work for a Sol-Ark distributor and also help Sol-Ark itself with field testing and finding bugs.

My system is a 12K Sol-Ark and 6 x 5.4KWh eFlex Fortress Batteries, total equals 32.4KWh of batteries.
The PV is 28 x LG 365W Neon Panels = 10 KW of PV.

Your Graphs were hard to See on the Screen but it looked like your batteries were carrying you through the night.  That probably wont be the case in Summer when the AC will be sucking your power dry.

Anyway I really heard your words about the Finances and I think you should reconsider upgrading the batteries.  It is just to soon!  I started off with Two batteries and an Intention of putting in one more.
A month later I had three and I thought I would be happy but my batteries were charged by 12 noon and a lot of PV was being wasted.   I spent time studying my usage for several months to find a balance between Summer and Winter Production so I could calculate how many batteries I would need without having so many as to kill my ROI.  It takes time to get that Data.  Too many batteries can be just be a pain in the butt to keep charged and as you will see below the reason why.  But the main thing is it kills your ROI.

As for your question about batteries balancing the Load between themselves.  The Batteries only balance the Individual cells in the pack.   Most batteries use Passive Balancing but the more expensive ones use active balancing.  You need to get the BMS software from the company that sold you the packs and buy a $20 RS232 dongle to see the state of the cells inside the pack.  There is also a ton of other interesting info the software will show you like the Amount of cycles the cells have done and their Temperature and each of the 16 LFP cells voltages and the differential voltages.

As for the three packs balance themselves out under load, that does not happen.  They will naturally balance to some degree based on IR & balanced line resistance but there is nothing actively doing it in the BMS.   The BMS just turns on the MosFets full ON or Completely OFF.  My eFlex batteries and all of the really expensive commercial ones don't even use Mosfets, they use industrial 250 Amp Relay and internal Class T fuses for protection.

If your Cable lengths from the Batteries are all even in length the charge and discharge current should be within 1-2 Amps of each other.  In many Installations people have a foot or two of longer cable going to one battery or the other and this can create 3-4 Amp differences.  You should put a clamp meter on them when charging/Discharging and you will see some interesting stuff.

You do need that battery pack monitoring software because one problem with these packs have is cells going out of balance.  The BMS may cut out charging at 55.4V but that does not mean the pack is really 100% charged.  Some cells may be at 3.65V and some may be at 3.3V  This is why the very Expensive packs use active balancers so that this does not occur.  With Passive balancing it takes time to get the cells balanced and if the pack Voltage hits the Charge limit it stops balancing the pack and goes into standby mode.   If the cells are fully charged everyday the problem almost never happens but if you have several consecutive days of 50-60% Charge which becomes more likely with more packs, then it can happen.  Typically I recommend to people that if you have three consecutive low charge days of charging then Grid charge the batteries on the third evening to 100% just to keep them from getting too far out of balance.

BTW the biggest problem with Cell imbalance is that your batteries may be showing 70% SOC at 10pm and then suddenly by 10:25 PM the SOC nose dives to 40%.  It is because those 3.3V cells have been shutoff due to Low voltage levels like 3V being reached and the whole pack goes offline putting and all of the load to your remaining two packs.   You will see it in your graph as a Sudden drop in SOC during the night.

Lastly, do not discharge below 20% SOC.  All of the reputable companies warn against going lower because it does shorten the length of the battery life.  Companies like Fortress Power actually log the DOD and warn customers that they can void the Warranty if they see below 20% being done routinely.
Also very important, do not charge the batteries to 56V.  This is a common mistake that has now become so normal among the DIY group that you cannot even argue with them about it anymore.

In commercial installations we set the charge voltage to 54.4V as measured at the battery terminals. 
This will give us 100% SOC.  Anything above that is used by people who have lower B grade cells or refurbished cells.  Going up to 56 or God forbid 58V is just adding a lot of heating to the Pack and causing all sorts of issues that will show up years from now. 

Have fun, Solar is very cool.

[EEVblog]

Your Graphs were hard to See on the Screen but it looked like your batteries were carrying you through the night.  That probably wont be the case in Summer when the AC will be sucking your power dry.

Our house is very thermally efficient. We don't us that much aircon, and hardly ever leave one running the whole night.
Typically say in the kids bedroom if the wife thinks they might be too hot or two cold we leave it one for an hour or two and I turn it off before I go to bed.

As for your question about batteries balancing the Load between themselves.  The Batteries only balance the Individual cells in the pack.   Most batteries use Passive Balancing but the more expensive ones use active balancing. 

Not in this case, the designer of the battery (who is in the video) said they talk to each other and are actively balanenced between units during charging.

Lastly, do not discharge below 20% SOC.

I think you must have missed the other parts to my video, I'll link them in.

[The Soulman]

As for your question about batteries balancing the Load between themselves.  The Batteries only balance the Individual cells in the pack.   Most batteries use Passive Balancing but the more expensive ones use active balancing. 

Not in this case, the designer of the battery (who is in the video) said they talk to each other and are actively balanenced between units during charging.

How would that work? 
For that to work the battery packs voltage must be regulated individually inside each pack with a buck/boost converter, don't think so. (Power/efficiency loss, heat to get rid off, costs, etc.)
Don't think there is much in between the stack of cells and the output jacks of the pack apart from a big mosfet to be able to disconnect the pack under fault conditions.
Cell-level balancing only.

[The Soulman]

As for your question about batteries balancing the Load between themselves.  The Batteries only balance the Individual cells in the pack.   Most batteries use Passive Balancing but the more expensive ones use active balancing. 

Not in this case, the designer of the battery (who is in the video) said they talk to each other and are actively balanenced between units during charging.

How would that work? 
For that to work the battery packs voltage must be regulated individually inside each pack with a buck/boost converter, don't think so. (Power/efficiency loss, heat to get rid off, costs, etc.)
Don't think there is much in between the stack of cells and the output jacks of the pack apart from a big mosfet to be able to disconnect the pack under fault conditions.
Cell-level balancing only.

Each module would be capable of setting it's own charge level. Say, if there are 5 packs at 20% and they all know it, and the total desired system charge rate is 100A, then it's easy for each module to know to only charge at 20A.

Cool, but how? crude pwm?
If you say charge level do you mean charge-current or the level to up to were it charges (and then disconnects from the main bus?)?

[EEVblog]

In commercial installations we set the charge voltage to 54.4V as measured at the battery terminals. 
This will give us 100% SOC.  Anything above that is used by people who have lower B grade cells or refurbished cells.  Going up to 56 or God forbid 58V is just adding a lot of heating to the Pack and causing all sorts of issues that will show up years from now. 

[EEVblog]

Cool, but how? crude pwm?
If you say charge level do you mean charge-current or the level to up to were it charges (and then disconnects from the main bus?)?

Sorry I misread your post, I was wrong.
The battery designer literally said this to me in a message

"The current balancing is active at the cell level on the charge cycle, and technically passive at pack level on discharge cycle (not PWM). The active cell balacing while charging and the associated bit of current shuffling around between the modules should result in reasonably balanced packs

i..e because all the battery modules BMS's are connected and can communicate, I think he means it essentially becomes one big battery with individual cell management.

[EEVblog]

Update:
I'm getting the meter changed over to a smart meter some time between the 23rd-29th.
That will give me more potential options to switch to a provider that allows time of use charging and even feed back to the grid from my battery if I don't need it.

[The Soulman]

Cool, but how? crude pwm?
If you say charge level do you mean charge-current or the level to up to were it charges (and then disconnects from the main bus?)?

Sorry I misread your post, I was wrong.
The battery designer literally said this to me in a message

"The current balancing is active at the cell level on the charge cycle, and technically passive at pack level on discharge cycle (not PWM). The active cell balacing while charging and the associated bit of current shuffling around between the modules should result in reasonably balanced packs

i..e because all the battery modules BMS's are connected and can communicate, I think he means it essentially becomes one big battery with individual cell management.

Thanks, makes sense.
Still wondering what mechanism they use to prevent fireworks when connecting (when installing) two packs with two different states of charge.
Let the chemistry do it's thing?

[EEVblog]

Cool, but how? crude pwm?
If you say charge level do you mean charge-current or the level to up to were it charges (and then disconnects from the main bus?)?

Sorry I misread your post, I was wrong.
The battery designer literally said this to me in a message

"The current balancing is active at the cell level on the charge cycle, and technically passive at pack level on discharge cycle (not PWM). The active cell balacing while charging and the associated bit of current shuffling around between the modules should result in reasonably balanced packs

i..e because all the battery modules BMS's are connected and can communicate, I think he means it essentially becomes one big battery with individual cell management.

Thanks, makes sense.
Still wondering what mechanism they use to prevent fireworks when connecting (when installing) two packs with two different states of charge.
Let the chemistry do it's thing?

I've asked him. My guess would be to keep the new pack shut off until the others discharge to a value close enough and then you switch the new one in.
Or yeah, maybe the chemistry just handles it.

[rteodor]

One can have a LFP battery at 30% and another one at 60% in parallel and have zero current between them. That's just how LiFePO is.
I think so too that balancing is only inside each battery. If it's not then the BMS must be one kick-ass BMS. Show it to us then
However, parallel battery packs balance themselves when reaching the top charging voltage so there is no need to do fancy balancing or switching. When cells go past 3.375V they gradually reduce current so the parallel ones can catch up.

Still, the cabling should be "on the corners": one to the low side and another one from the top. Not that it matters that much at 5KW, its only that the battery closest to the wires will cycle more Ah than the next one.

As for the battery capacity its better to set a goal because its so easy to jump over the horse. For example in my case I wanted to be able to pass thru the night after a sunny December day without worries.
Otherwise you will be sort-of-happy 4 months (winter) of the year and unhappy the remaining 8 (summer).

[EEVblog]

Still, the cabling should be "on the corners": one to the low side and another one from the top. Not that it matters that much at 5KW, its only that the battery closest to the wires will cycle more Ah than the next one.

Yes, Peter also mentioned this, but at 5kW max it's not a big deal.

Last two days has been awful weather, pack only got from 20% to 25% yesterday 

[nctnico]

Cool, but how? crude pwm?
If you say charge level do you mean charge-current or the level to up to were it charges (and then disconnects from the main bus?)?

Sorry I misread your post, I was wrong.
The battery designer literally said this to me in a message

"The current balancing is active at the cell level on the charge cycle, and technically passive at pack level on discharge cycle (not PWM). The active cell balacing while charging and the associated bit of current shuffling around between the modules should result in reasonably balanced packs

i..e because all the battery modules BMS's are connected and can communicate, I think he means it essentially becomes one big battery with individual cell management.

That still doesn't explain how to route more or less current in/out a battery pack. There has to be an active element which routes the current based on SOC in order to keep the packs at equal SOC levels so the packs can be discharged / charged equally.

[EEVblog]

Still wondering what mechanism they use to prevent fireworks when connecting (when installing) two packs with two different states of charge.
Let the chemistry do it's thing?

I've asked him. My guess would be to keep the new pack shut off until the others discharge to a value close enough and then you switch the new one in.
Or yeah, maybe the chemistry just handles it.

Peter replied saying that when adding a new battery you should ensure they are within 1V of the others before connecting.
The usual way they do this charge existing packs to to 100%, switch them off, insert new batter yand charge to 100%, and then switch them all on.
He also said the BMS will not allow fireworks. You can short the batteries and they'll be fine.