Battery banks, parasitic loads and low sun hours

[SolarRich]

The relay they use has a 6W coil and goes for about $45 on ebay.
I don't know enough about lithium BMS to figure out where the other 24W is being used. If indeed that 30W number is correct. I would think that the battery would be a tad warm is it was using 30W just sitting there idle w/o doing any charging.

From a distributor(Mouser) - that kilovac relay goes for between $150 and $200 depending on quantity purchased.

 

[SHTF Power Anyway]

It's a BMS, not a particle accelerator.

Allowing a generous 3 watts for the contactor, another generous 1 watt for LED's, and a very liberal 5 watts for the BMS, that's still just 9 watts of draw.

I just thought of something however.. the BMS has a disconnect and reconnect voltage spec.. How does THAT work? With my setup, I have one relay, when the BMS brings down the hammer and turns that relay off, the only way for me to recharge the pack is to either hot-wire the relay or a direct connection to the cell terminals.

So running a quick diagram in my head, maybe they have a charge relay and a discharge relay? So 6 watts for the relays, 1 watt for leds, 5 watts for BMS. That's 12 watts..

Do most of these types of batteries come with monitoring capabilities (BMS software) for the end user? This is what Fortress told me about using theirs:

The Tool you are using is an engineering tool.
This provides diagnostics to identify a battery failure.
This tool is not intended to be used as a monitoring device.

You are welcome to monitor the battery but this is similar to using a CAN tool to monitor your automobile performance.
Use at your own risk and use it to adjust how you are utilizing the unit.

The performance of the eflex batteries in normal use is monitored using the LEDs on the battery and the data provided to the inverter.

I don't know how a DIY customer is supposed to actually monitor any of this stuff if, in the end, all of the data is wrong in both the BMS software and the Sol-Arks when it comes to these batteries. How would a person like me even know I had a failing battery? I'm really quite good with analysis but not with unreliable data. As an accountant, I always built analysis with good points to confirm my numbers. I feel blind, gagged and kicked when I'm down with these damn batteries!

 

[labeeman]

It's a BMS, not a particle accelerator.

Allowing a generous 3 watts for the contactor, another generous 1 watt for LED's, and a very liberal 5 watts for the BMS, that's still just 9 watts of draw.

I just thought of something however.. the BMS has a disconnect and reconnect voltage spec.. How does THAT work? With my setup, I have one relay, when the BMS brings down the hammer and turns that relay off, the only way for me to recharge the pack is to either hot-wire the relay or a direct connection to the cell terminals.

So running a quick diagram in my head, maybe they have a charge relay and a discharge relay? So 6 watts for the relays, 1 watt for leds, 5 watts for BMS. That's 12 watts..

Put a diode across the relay contacts it will let you charge the battery when the relay is open.

 

[SHTF Power Anyway]

Is there a way to print this whole thread to paper or pdf?

 

[TorC]

Looks like the forum prints fairly neatly. There are headers that you may want to avoid if you print to paper, perhaps even to PDF.

For each page, select the posts segment of the page, go to print, and tell it to print selection only. I found page three alone was 15 pages when I did that, so you may find it's a bigger file than you want in hard copy. I think most modern OSs have an integrated print to PDF these days you can use.

 

[SHTF Power Anyway]

Looks like the forum prints fairly neatly. There are headers that you may want to avoid if you print to paper, perhaps even to PDF.

For each page, select the posts segment of the page, go to print, and tell it to print selection only. I found page three alone was 15 pages when I did that, so you may find it's a bigger file than you want in hard copy. I think most modern OSs have an integrated print to PDF these days you can use.

That's what I was seeing. I guess I'll have to just go through and pick out the most important pieces of information. I want to share the thread with my neighbor but he's 82 and not exactly computer/forum literate. There are some real gems of data/ideas in this thread that should not be wasted. He's building a small 12v system and is looking forward to building a solar panel cart that we can use to get the most uptake for him.

 

[jrcromer]

The eFlex BMS is much more advanced than what many are imagining a BMS processor to be. I could go on about the difficulties of maintaining battery-battery and battery-inverter communication with 30+ devices in the communication circuits.

@SHTF Power Anyway
Fortress can and will easily tell you if you have a failing battery. You have an entire technical support team to help you, but your conspiracy theories about cell efficiency and battery self-discharge rates postings across social media are not helping your disposition. If you feel blind, gagged, and kicked, you shouldn't. You are not using those line items in the same way the industry uses those line items. You were told the BMS tool was not a consumer-facing tool but rather an installer tool (and despite not being one of our installers, we still provided you with it as well as support to navigate it). We also now have a consumer-facing Guardian monitoring hub that is our consumer facing monitoring tool.

As to your specific, non-warranty issue, we're willing to help by swapping your eFlex batteries with refurbished original eVault battery units, which will reduce the idle consumption of your BMS, removing that problem from your mind. You will need to pay the "both ways" shipping costs, but we will help with the logistics and the good news is it costs us alot less to ship freight than you. We will also need time on our end to thoroughly test the refurbished eVaults before sending. Yes, you will have to engage with the same technical support team that you have been previously lambasting. This is the cheapest way for you to achieve your goal of lower power consumption.

Be warned in many ways eFlex is a better battery than our original eVaults aside from the obvious fact that 10 smaller batteries with their own BMS units have a larger BMS power draw than 3 larger batteries with a single BMS unit. Our eFlex testing is showing the power consumption of the BMS system to be <20W. The technician who provided the power consumption was setting a "under promise, over deliver" expectation.

You will lose closed-loop communication with the inverter and have to operate in voltage mode. You will not be able to use our now available Guardian monitoring hub (which requires a more power consumptive BMS). But you will have piece of mind on your BMS power consumption conspiracy theory.

Most importantly, all of this work won't fix your issue because as we originally told you, you aren't getting enough sunlight in the wooded, pacific northwest in the winter and your cheapest option during the winter (compared to doubling your system size) is to use your generator.

PS. For those interested, its very easy for a manufacturer to tell a warranty issue, simply due to scale. Scale will let the manufacturer quickly find out if there is a component defect (the majority of which would appear in the first year of operation) and then longer issues are typically dead cell issues which are a pack replacement (a little more complicated than that). Fortress uses large form factor prismatic cells so that we can monitor each cell - when we notice a cell issue out of range, that individual battery shuts off for safety.

 

[jrcromer]

I’ve been totally off grid for one year on two SA12k’s, 143kWh DIY w/JK BMS (<1W w/o LCD on) and 34kWp. That is double what my vendor told me I needed at 38° latitude in the hypocrite belt. No generator needed, but the Honeywell 10kW on LP gets tested monthly. I brought in 17MWh. I’ve had at least 7 days below 5kWh. We made it through Dec, Jan and Feb….barely. If you want to be off grid, you need a lot of solar panels when you think you have enough buy another pallet.

143 kwh <--- now do 15kW + 55 kwh roughly 15 degrees further north, with a shallow tilt angle in the woods. In a climate nationally famous for cloudy winters like OP.

 

[Nobodybusiness]

But you will have piece of mind on your BMS power consumption conspiracy theory.

Conspiracy theory?
Is 10 batteries using 300 watts an hour or not?

 

[jrcromer]

Conspiracy theory?
Is 10 batteries using 300 watts an hour or not?

1. The round trip efficiency and self-discharge numbers are industry standards. I've provided multiple citations.
2. Very few manufacturers publish their BMS power draw. On this discussion thread, a user asked another manufacturer to disclose their power draw, and the response was that it was a trade secret! At least our Fortress technical support provided an answer (and has since investigated further to show a <20W power draw).
3. There are reasons to have a high powered BMS. Likewise, you can find BMS that are less complex and have lower power draw, but do not support the same kind of features that the higher powered BMS has.
4. We're offering to switch the OP's batteries with a larger form factor which would address their power draw concern, but again, its not the problem.
5. The problem is OP's desire to live offgrid in the wooded pacific northwest without utilizing their generator. This can be illustrated by the OP enabling their online monitoring of their inverter system and collecting their load consumption data.

 

[cs1234]

Be warned in many ways eFlex is a better battery than our original eVaults aside from the obvious fact that 10 smaller batteries with their own BMS units have a larger BMS power draw than 3 larger batteries with a single BMS unit. Our eFlex testing is showing the power consumption of the BMS system to be <20W. The technician who provided the power consumption was setting a "under promise, over deliver" expectation.

The technician wouldn't have provided the erroneous information if you had those numbers published in your specifications, instead of hiding it like it's something to be ashamed of. If Spongebob can do it, so can Fortress.

The eFlex BMS is much more advanced than what many are imagining a BMS processor to be. I could go on about the difficulties of maintaining battery-battery and battery-inverter communication with 30+ devices in the communication circuits.

@SHTF Power Anyway
but your conspiracy theories about cell efficiency and battery self-discharge rates postings across social media are not helping your disposition. If you feel blind, gagged, and kicked, you shouldn't. You are not using those line items in the same way the industry uses those line items.

So the whole industry is a bunch of liars, and you are liar along with them? What does "98% Round Trip Efficiency" mean to you? The only way your battery could possibly achieve something like that is if you instantaneously charged it, then instantaneously discharged it. Even then, I don't think you could hit 98% round trip efficiency. I'll tell you what 98% efficiency doesn't mean to me, I give it 5000 watts of electricity and 24 hours later it can give me 4280 watts back because it ate the rest from it's BMS.

 

[cs1234]

1. The round trip efficiency and self-discharge numbers are industry standards. I've provided multiple citations.
2. Very few manufacturers publish their BMS power draw. On this discussion thread, a user asked another manufacturer to disclose their power draw, and the response was that it was a trade secret! At least our Fortress technical support provided an answer (and has since investigated further to show a <20W power draw).
3. There are reasons to have a high powered BMS. Likewise, you can find BMS that are less complex and have lower power draw, but do not support the same kind of features that the higher powered BMS has.
4. We're offering to switch the OP's batteries with a larger form factor which would address their power draw concern, but again, its not the problem.
5. The problem is OP's desire to live offgrid in the wooded pacific northwest without utilizing their generator. This can be illustrated by the OP enabling their online monitoring of their inverter system and collecting their load consumption data.

1. The whole industry is full of crap. Those words are meaningless then. You and the rest of the industry should be ashamed. You are only quoting the inherent ability of lifepo4. It has nothing to do with your product whatsoever, but the lifepo4 chemistry itself.
2. See #1. Maybe the industry should start publishing those numbers. You can lead the charge, instead of making people that have foolishly purchased your product find out the hard way.
3. Yes, I'm sure there are reasons that people might want an ultra reliable (I'll take your word for it) BMS capable of repeated high amperage surges. Many solar customers don't have that need. She purchased 10 of these things. Per your statement of 300amps discharge.. that's 3000 amps at 48v. What possible reason could she have to discharge or charge at 144,000+ watts?
4. I'll give you that, that's a nice gesture. You should still publish the numbers, lead the charge to prevent this type of foolishness in the future.
5. I don't have much to say about the OP's situation.. it's kind of silly and I don't like to think about it.

We just want you to publish the numbers. The reason we were so surprised by it, is because it's outrageous for a 5kw battery to consume 480-720 watts a day for just being turned on.

 

[Nobodybusiness]

1. The round trip efficiency and self-discharge numbers are industry standards. I've provided multiple citations.
2. Very few manufacturers publish their BMS power draw. On this discussion thread, a user asked another manufacturer to disclose their power draw, and the response was that it was a trade secret! At least our Fortress technical support provided an answer (and has since investigated further to show a <20W power draw).
3. There are reasons to have a high powered BMS. Likewise, you can find BMS that are less complex and have lower power draw, but do not support the same kind of features that the higher powered BMS has.
4. We're offering to switch the OP's batteries with a larger form factor which would address their power draw concern, but again, its not the problem.
5. The problem is OP's desire to live offgrid in the wooded pacific northwest without utilizing their generator. This can be illustrated by the OP enabling their online monitoring of their inverter system and collecting their load consumption data.

I understand they need more Solar to cover these losses but their initial computations did not take into account a 7.2Kw per day idle usage from the BMS because they weren’t aware.

If they were aware of it they could have went another route with different manufacture.

They purchased your batteries based upon published specs and Your Distributors recommendations.

I dare say how this has been handled will not be received well in the DIY community.

A company that has $2.7 Billion in Revenue and 195 Million in Net profit can afford to remedy this situation without resorting to shipping old used batteries while making the end user pay shipping both ways.

It would have been cheap PR but perhaps DIY customers aren’t a large portion of your sales.

 

[A.Justice]

It's a BMS, not a particle accelerator.

......

I can watch Netflix and play lower end video games on my laptop with 30 watts, Or 4 wifi security cameras, or a 22 inch TV, or run my entire home network.

Maybe it mines Bitcoin. ?

 

[Nobodybusiness]

I can watch Netflix and play lower end video games on my laptop with 30 watts, Or 4 wifi security cameras, or a 22 inch TV, or run my entire home network.

Maybe it mines Bitcoin. ?

You know I wouldn’t put it past some companies to hard code something like that.

Not saying that’s the case here but a small ASIC and some control logic and you have a billion tiny miners..

 

[MurphyGuy]

UPDATE:
Fortress did do as they claim in post #290, they investigated the real numbers and sent the information to the OP, who then sent it to me for evaluation.

It would appear that the problem (if we want to call it that), is that their two contactors are a little energy hungry. The BMS uses 4 watts to sit there and be happy.. it would seem that each of their contactors use 7 watts, and there are TWO of them.. So 7+7+4 = 18 watts.

A standard 48 volt Tyco Kilovac contactor uses 1.74 watts, but judging from the limited photos I saw looking at the inside of a Fortress battery, there's no way you would be able to fit two Tyco contactors in there without making the battery case larger.

It is my opinion that the 30 watt figure is a maximum draw. That would account for the BMS's needs, both contactors being active, and two or three cells being simultaneously balanced all at the same time.

Note to Fortress: @jrcromer You should really reduce the draw on the contactors. 7 watts is a lot of energy.

Also, I have to commend you for your attention to this, that speaks volumes about Fortress. And on that note, would you be willing to answer some questions about the BMS ?
First question: Does your BMS always balance or does it balance only when charging?
Second question: Does your BMS have a balance start voltage where it only balances when a cell is above a set-point? Or does it balance at any cell voltage?

I ask this because lithium batteries are generally top-balanced and get a little wacky as they discharge which causes them to go out of balance. Any BMS that balances at the lower voltages is sort of wasting a lot of energy as cells tend to come back in balance all on their own once they reach the top again.

With the REC BMS I use, the BMS has two set points for balancing. Any cell above set-point 1 will balance IF the pack is currently charging, and any cell above set-point 2 will balance regardless if the pack charging or not.

 

[jrcromer]

I'll tell you what 98% efficiency doesn't mean to me, I give it 5000 watts of electricity and 24 hours later it can give me 4280 watts back because it ate the rest from it's BMS.

Battery chemistry (lithium iron phosphate, lithium cobalt, lead acid) Cell quality (A grade, B grade) as well as form factor (pouch, prismatic, cylindrical) are not variable. RT efficiency does not have a time component in the test other than charging and discharging the battery. It does not test "having the batteries sit for 24 hours powered on". In other words, RT efficiency on a battery data sheet is a cell quality indicator. Comparatively, our SGIP test data (which cuts the battery off sooner) indicates that >99.5% of our 5.4 kwh rating is usable capacity. That doesn't match up with your math. And SGIP definitely asks for receipts.

You are welcome to call the entire industry a liar, but I think you will find Fortress publishes significantly more product information on its website than the competition.

Per your statement of 300amps discharge.. that's 3000 amps at 48v. What possible reason could she have to discharge or charge at 144,000+ watts

Having the internal battery components rated for a higher amperage is not about running the battery at 3x its maximum output rating continuously as you are implying. The over amperage accommodates instances where a single battery is subject to over amperage when the BMS has not engaged. Rare - but if it does happen, it can result in a very expensive brick. Much, much more common with mosfet BMS (where the BMS would burn up and often wreck the battery in the process). End users care about their specific system, manufacturers care about 100000x that scale. It's very difficult to damage the eFlex or eVault MAX through misuse. Whole home backup power has greater needs than smaller DIY applications and more variable needs than UPS systems. Its not uncommon for end users to turn on batteries at dramatically different states of charge as well as to not adjust inverter settings if for some reason one battery is off and the other is on (but the inverter is programmed assuming both batteries are on). Likewise, its not surprising that many DIYers are comfortable saving a few bucks installing cheaper products that you don't find professional installers selling. Fortress DIYers are typically installing products that are robust enough to be approved by solar financing companies, and just saving money by not hiring the professional.

I understand they need more Solar to cover these losses but their initial computations did not take into account a 7.2Kw per day idle usage from the BMS because they weren’t aware.

Sure. OP's problem isn't the idle load of 20W per battery BMS. It's that she would need twice the amount of solar and batteries to get anywhere near where her system expectations are. She chose not to hire a professional who could have coached her towards a larger form factor battery, and away from a server rack battery with a contactor-based BMS. We have offered to replace her used batteries with a larger form factor battery (the eVault) despite it not being a warranty issue. That will reduce her power draw by over 70% and she will still be exactly where she is today (needing to run a generator regularly in the winter). OP has other threads where other DIYers in her region have told her that her solar is underpowered for her goals of living offgrid without regular use of a generator in winter.

can afford to remedy this situation without resorting to shipping old used batteries while making the end user pay shipping both ways.

This is not a warranty issue. The end user's problem is not related to the BMS power draw, but to her system design. We're already saving her a bunch in freight charges, as it costs significantly less for companies to ship freight than individuals. We're happy to cover the logistical support, but OP needs to cover the hard cost incurred for this non-warranty issue.

OP (if she elects the option) would be returning used batteries and obtaining a refurbished batteries which have been checked out by Fortress with more nameplate capacity than what she originally purchased. Not going to get an equivalent offer from anyone else in this industry like that, and it specifically resolves her complaint. Alternately there are many eFlex customers who would be happy to purchase her batteries from her.

It would appear...the BMS uses 4 watts... contactors use 7 watts, and there are TWO of them.. So 7+7+4 = 18 watts....
A 48 volt Tyco Kilovac contactor uses 1.74 watts, but... there's no way you would be able to fit two Tyco contactors in there without making the battery case larger.

Correct, the eFlex is a compact version of the eVault MAX (i.e. digital processor BMS that is separated from the high amperage contactor controls). We use less power hungry contactors for the eVault MAX but are space constrained to deliver a premium BMS in the form factor of a server rack battery. The actual difference in your example from one system to another is (7 - 1.4 watts) x 2 = 11 watts. We feel that energy difference is worth the safety and reliability gain.

Does your BMS always balance or does it balance only when charging?
Does your BMS have a balance start voltage where it only balances when a cell is above a set-point? Or does it balance at any cell voltage?

The BMS balances based on cell-level data at the top of the battery range (i.e. charging or full).

 

[cs1234]

Battery chemistry (lithium iron phosphate, lithium cobalt, lead acid) Cell quality (A grade, B grade) as well as form factor (pouch, prismatic, cylindrical) are not variable. RT efficiency does not have a time component in the test other than charging and discharging the battery. It does not test "having the batteries sit for 24 hours powered on". In other words, RT efficiency on a battery data sheet is a cell quality indicator.

You are welcome to call the entire industry a liar, but I think you will find Fortress publishes significantly more product information on its website than the competition.

It's pretty dishonest, by you and the rest of the industry. I think pretty much everybody here would agree you and the rest of the industry are lying through omission by not having your idle consumption listed anywhere. It doesn't matter so much if it's 1 watt per hour. 20-30 watts per hour is a joke for a 5kw battery. It's a battery, not an AIO inverter. Based on your own consumption figures, I don't think you should label / market your battery as a solar or green energy storage battery at all. Grid tied whole home backup, ok. For solar, the battery is so wasteful of the energy given it, that it's not remotely GREEN.

Additionally, your published specs don't mention anywhere the kind of power output you claimed here in our discussion. Your spec sheet lists a 130amp maximum surge power rate for 5 seconds. You spouted figures here of 200-300 amps. So which is it?

I'll give you this much, your website and batteries are pretty. Your batteries also have an Intertek listing, which is nice, but still not a UL listing that is good everywhere without a potential fight with the AHJ. If you do have an actual UL listing, I apologize, but it wasn't on your website. Also, I despise the UL and the racket they have going anyway. An Intertek listing should be ok, but it isn't because of corruption.

 

[cs1234]

I didn't say the quoted line above. That was @Nobodybusiness .

Not that I necessarily disagree with them. 20-30 watts idle consumption is bad enough that it should have been a published spec on a 5kw battery. You should eat the cost to replace the things in their entirety for omitting that information. Don't blame it on a DIY'er. You have the ability to not sell to DIY'ers if you want through the rules placed on your sales partners.

 

[Quattrohead]

The battery is not broken, just not ideal for the OP. Professional assistance should have been sought or as a DIY'er you accept your own design, decisions and implementation.
I never did figure out what the OP has/needed etc for a system, honestly it was a train wreck of information and speculation.
And yeah, Chinese UL paperwork is bullshit 99% of the time.