Battery banks, parasitic loads and low sun hours

[SHTF Power Anyway]

The BMS cut off voltage is listed in the battery specifications.. you'll have to look it up.. I remember seeing it, just don't remember what it was.

You should print out the specs, laminate them, and put them in a folder next to your off-grid system. In fact, all important information should be in a single folder where it is quick and easy to reference. While it might be cumbersome to put the entire inverter manual or battery manual in a folder, you should put the important pages in there. For example, inverter menu options, important settings, etc. And a place for you to take notes on behavior events or reminders.

We do have a nice container of documents right next to the system and because we have multiple units, we have multiple copies of things so I can keep a copy in the house, my neighbor has a copy, our friend has a copy. lol

I do see cut off voltages but don't see anything labeled specifically the BMS cutoff voltage. There's a "Recommended Low Voltage Disconnect" which says 48V and a "Battery Low Voltage Protection" of <45V and, finally, there's a "Battery Recovery Voltage" of 45V.

 

[ElectricIslander]

I'll second the NAWS recommendation. Really excellent to deal with.
When I replaced my SLA with Discover I noticed some 'missing energy' rather quickly. Figured it was parasitic losses in the batteries from the BMS. But now I know for certain where this missing energy is going.
Yes, the self consumption power the battery uses should be a published number. Once it's on the spec sheet I suspect that it will get much lower real quick. And those companies that claim it to be a secret will have trouble selling their products.

Did you ever find out what the power loss from the Discover batteries added up to?

This would be really important for us as we are also off-grid, in a very cloudy part of the PNW during the winter.

I'm a bit alarmed to hear about your finding of significant missing energy because I was thinking of buying four of the Discover AES batteries (or their new Element batteries) but if the self consumption of the Discover BMS is anything like the Fortress E-Flex I'm not going to buy either of them.

 

[SHTF Power Anyway]

Did you ever find out what the power loss from the Discover batteries added up to?

This would be really important for us as we are also off-grid, in a very cloudy part of the PNW during the winter.

I'm a bit alarmed to hear about your finding of significant missing energy because I was thinking of buying four of the Discover AES batteries (or their new Element batteries) but if the self consumption of the Discover BMS is anything like the Fortress E-Flex I'm not going to buy either of them.

I hope you fare better in your choices. I'd love to hear how yours work out for you in the future. Some of the feeling I've gotten in all of this is that the PNW people shouldn't even attempt off-grid with Solar even if the loads are pretty miniscule. I know that's not necessarily true. I did speak with a guy from www.solarelectricuspply.com. The gentleman I spoke with lives in Olympia, WA and is familiar with our weather patterns and solar uptake. He looked at my location and thought we made the right choices with our PV placement given our circumstances and he understood what our goals were. He did suggest we might have looked at flooded lead acid batteries. Deka was the brand.

He also suggested we look at Bergey wind turbines. I don't see them being viable for us for many reasons but it may be a good option for you.

 

[rodrick]

I don’t see anyone buying one of these batteries knowing they have a idle consumption 1/2 to 3/4 of what a aio uses
obviously the saying you get what you paid for doesn’t apply hear

 

[MurphyGuy]

We do have a nice container of documents right next to the system and because we have multiple units, we have multiple copies of things so I can keep a copy in the house, my neighbor has a copy, our friend has a copy. lol

I do see cut off voltages but don't see anything labeled specifically the BMS cutoff voltage. There's a "Recommended Low Voltage Disconnect" which says 48V and a "Battery Low Voltage Protection" of <45V and, finally, there's a "Battery Recovery Voltage" of 45V.

Cut it off between 46 and 47 volts, that should do it.

 

[SolarRich]

I never figured out the power draw of the AES batteries. In my case it's not important because the batteries are only for grid outages.
The batteries are 130AH x 2 = 260AH. They lose 4% over night - which is 11 hours of no sun at this time of year. Connected to Sol-Ark 12k that is set to only charge from the PV. I don't know if the Sol-Ark is drawing any power from the batteries at night.

When I put the batteries into service I did some tests overnight by having a known power draw with the grid breaker turned off. This is when I noticed the missing power. But this also included the power used by the Sol-Ark.

 

[SHTF Power Anyway]

Cut it off between 46 and 47 volts, that should do it.

As of 12:11, the voltage is 51.42 for the bank with the BMS showing 3 - 4 SOC with the exception of battery 5 which shows 24 SOC with the same voltage showing on the BMS software of 51.4. I've asked Fortress if they would log into the batteries to take a look but have not heard anything back as of this post. I am getting concerned that we will be hitting the voltage mark in the middle of the night which is a bit problematic. I'd feel better shutting them all off before bed tonight and restarting them in the morning when I'm available to monitor and engage in restoring power to the bank. As of right now, this system is not connected to the grid for recharging. We have the generator which is extremely slow to charge the bank or we have the PV (which is not going to be good tomorrow). Suggestions?

 

[MurphyGuy]

As of 12:11, the voltage is 51.42 for the bank with the BMS showing 3 - 4 SOC with the exception of battery 5 which shows 24 SOC with the same voltage showing on the BMS software of 51.4. I've asked Fortress if they would log into the batteries to take a look but have not heard anything back as of this post. I am getting concerned that we will be hitting the voltage mark in the middle of the night which is a bit problematic. I'd feel better shutting them all off before bed tonight and restarting them in the morning when I'm available to monitor and engage in restoring power to the bank. As of right now, this system is not connected to the grid for recharging. We have the generator which is extremely slow to charge the bank or we have the PV (which is not going to be good tomorrow). Suggestions?

Pretend its a newborn baby and you need to get up in the middle of the night to check the diaper?

The closer you get to the bottom, the more accurate the diagnosis of self-consumption will be. That said, if you're at 49 volts by bed time, you could just record the voltage, turn them all off, then start up in the morning. Problem is, we don't know if they have a power draw while actually turned off, but at 49 volts, skewing the test results with that small bit of remaining power isn't going to change your view of the universe.

 

[MurphyGuy]

Check out this curve.. You're just entering the knee so voltage is going to drop off much faster from here out.

 

[ElectricIslander]

Shtf Power Anyway: Is there some reason why you can't charge your Fortress batteries from the grid? I gather they are mainly for backup. Is this a permitting issue or just need to wire a transfer switch or connection to the Sol-Ark?

SolarRich: Regarding Discover Battery Self Consumption

Two 130 AH batteries fully charged at around 50 V are 6.5 kWhr ea or a total of 13 kWhr.

If the entire Discover battery bank of two batteries goes down by 4% overnight that is a drain of 0.04 X 13,000 Whr = 530 Whr.

The specs for the Sol-Ark 12k state that idle power is 60 W, overnight (11 hrs of darkness with no PV) that is 60 W x 11 hrs = 660 Whr.

Within the likely errors in the estimate of SOC by the BMS, it looks like the estimated 4% discharge overnight is about what you would expect from the Sol-Ark being on continuously. This suggests that the Discover batteries self consumption rate is rather low compared to that of the Sol-Ark.

Would be very interesting to see what the rate of discharge of the Discover batteries is with the Sol-Ark turned off overnight!

Publishing an actual measured (or even better a manufacturer specified value) for what seems like the lower self consumption of these Discover batteries may galvanize Fortress into optimizing the design of their batteries to lower self consumption.

Self consumption is a key design parameter for an off-grid energy storage system. Not quoting it as a specification is deceptive enough to make products legally unsuitable for advertised purpose.

 

[SHTF Power Anyway]

Shtf Power Anyway: Is there some reason why you can't charge your Fortress batteries from the grid? I gather they are mainly for backup. Is this a permitting issue or just need to wire a transfer switch or connection to the Sol-Ark?

We didn't want grid tied so we didn't wire it as such. We're looking at what changes we'd need to make to be able to, at least, temporarily charge from the grid. That's next on the list today.

 

[SolarRich]

ElectricIslander: The Sol-Ark is connected to the grid. I don't know if the Sol-Ark uses power from the grid or battery or both as needed? Recall that the Sol-Ark does not need batteries to operate grid-tied. One of these days I'll shutoff the Sol-ark for the night while leaving the batteries on. In the morning I'll turn the Sol-Ark on and see what the SOC of the batteries are.
The Discover batteries use a small box called a LYNK II. This is an adapter for the battery communications with the Sol-Ark. I had to open the LYNK II up to configure jumpers for the Sol-Ark communications. Inside is (if I recall correctly) a TI processor. This is powered by the batteries directly. The LYNK II board looked well made and IMO designed and made in the US. I have no reason, nor would I want to, to open up the batteries.
However in the Discover YouTube videos, the internals of the battery look well designed and well made. These batteries are expensive and I chose to pay the money rather than DIY them like I do everything else in my life

 

[SHTF Power Anyway]

So, I tried to engage Fortress to help support some anomolies I was seeing in the battery bank because the BMS software that I had from their staff and that I was told to look at to see alarms was showing a vastly different SOC than the others but still showed the same voltage. This is the "AWESOME" support this company has for users like me:

"Heidi,
The batteries are warrantied to 80% capacity for 10 years.

The nature of batteries is the internal resistance and performance changes over time.
The battery you are describing is likely from the newly installed ones and the internal resistance will increase with age to better match the group.

The CAN tool you are using is an engineering tool as I originally stated early on in this ticket.
Unfortunately, our support team does not engage in engineering projects or investigations of non system failures,
The performance of all residential storage batteries is capacity.
At this time, there doesn't appear to be a charging, discharging or capacity issue with your batteries.

I understand your interest in understanding your storage system and inverter performance, I wish all of the installed base cared
so much and would not abuse the components. At this time I am requesting you return CAN tool that we loaned to you for turning
off the wifi. We will ship you a Guardian to assist you in monitoring the eflex battery bank.


Douglas Greenfield"

I have now turned off the batteries completely. Hey, @jrcromer, you call this support?

 

[SHTF Power Anyway]

Out of 10 batteries showing the same voltage, 9 are showing SOC of 2-3 while one is showing 24 SOC.

 

[SHTF Power Anyway]

As an FYI to the community, I was told I was only to use the BMS lights to monitor my batteries. The new "monitoring hub" that I wasn't aware of until two weeks ago was still in beta testing. I was not offered this tool until I started this thread which clearly shows problems with these batteries. Now I'm being asked to return something that was never sent to me with any indication it was a loan. How would you feel?

I am clearly angry and emotional. $35k in a bank of bricks will do that to anyone.

 

[ElectricIslander]

As an FYI to the community, I was told I was only to use the BMS lights to monitor my batteries. The new "monitoring hub" that I wasn't aware of until two weeks ago was still in beta testing. I was not offered this tool until I started this thread which clearly shows problems with these batteries. Now I'm being asked to return something that was never sent to me with any indication it was a loan. How would you feel?

I am clearly angry and emotional. $35k in a bank of bricks will do that to anyone.

Sounds like an aggravating experience, brought on in part by Fortress not initially publishing actual battery self consumption. Accurate self consumption data is a vital parameter for off-grid system design, especially when using a sophisticated and complex LiFePO4 battery system like the one you bought.

Fortress's offer of a trade in to the e-vault and of a Guardian unit for monitoring seems like the best path forward for you. I had been in touch with Fortress support about the Guardian earlier anyways when I was considering Fortress batteries. It will probably give you the information you need to monitor the batteries in a more user-friendly way than the Can tool anyways.

 

[A.Justice]

Worst case, you could always open up the battery, manually cut out the BMS, and put a new one in. It's basically the same process people use when using electric vehicle batteries. It probably wouldn't be all that difficult.

 

[summit]

I pump 140 amps into a 25kWh lithium cells from a Chevy BOLT EV, and the temperature might rise 2°F if I do it for a couple hours. It is rare that I draw more than 100 amps out, and if I do, its only for a minute.. so no warming action to speak of.

slightly off-topic, please share your setup to charge your external pack from a BoltEV, can PM me as well, thanks

 

[jrcromer]

Yea Doug's response to you wasn't great.

The procedure to recalibrate is to run in voltage mode and let the sun take your batteries up to 100%.
You can't use a generator for this process, but you could use a grid charge.

My advice to a DIYer with a grid connection and internet on site:
Use what you already pay for. Even if you want to simulate being offgrid, it's super easy to have the Sol-Ark maintain the battery, even if not selling back to the grid.

 

[MurphyGuy]

slightly off-topic, please share your setup to charge your external pack from a BoltEV, can PM me as well, thanks

Communication error..
I pump 140 amps into a 25kWh battery (lithium cells from a Chevy BOLT EV), and the temperature might rise 2°F if I do it for a couple hours. It is rare that I draw more than 100 amps out, and if I do, its only for a minute.. so no warming action to speak of.


I don't own or drive a Chevy BOLT, my off-grid battery is made of cells from a Chevy BOLT.