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Old 06-14-2018, 07:34 PM   #81
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MPPT Solar and Lithium Question

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Originally Posted by uncle_bob View Post
Hi



My observation is that the 5V applies the first time the device is powered up. Why it exists ... no idea. '



Bob


That’s is my understanding as well. The victron MPPT controller needs to see a >5v differential between open circuit voltage on the panels and the battery voltage.

My batts sit at ~13.5v fully charged. My panels have an open circuit voltage of 21.2v when they light up in the morning for the first time. Delta is 7.7v - enough to get the charger to decide its time to go to work
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Old 06-14-2018, 08:06 PM   #82
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If your Venus or CCGX is configured to send data to VRM Portal via your trailer's internet connection, you can also get device information via your account on vrm.victronenergy.com in the device section once you have selected your "site".

Example attached... handy!
Thanks wulfraat. I just plugged a cheap WiFi dongle into the Venus, made a free account at that site you referenced, plugged in a little microSD card to store 16GB of data and for under 30 bucks the Venus now logs data to the web portal whenever it has a network connection. That could be your phone's hotspot or, in my case, the WiFiRanger. There are a lot of features here I haven't fully digested. This portal is more for looking at data trends, not the state of things this very instant. Anyway, another fun toy if you're a data nerd.

By the way, Victron lists some pretty obscure wifi dongles as the supported ones. I just chose a $10 one from StarTech, maker of one of the obsolete ones they list, and it seems to work fine. Mine is part number USB300WN2X2C.
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Old 06-14-2018, 08:20 PM   #83
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MPPT Solar and Lithium Question

FYI you can actually connect to remote console real time using the VRM portal if the Venus is online, over the Internet. There is also a VRM portal app if you don’t want to use the full browser version.

You are right though - it’s mostly for analyzing energy trends in the system.

I have a 16G card in my CCGX as well... I think you can store 200 decades of data on the 16GB card
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Old 06-14-2018, 08:23 PM   #84
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FYI you can actually connect to remote console real time using the VRM portal if the Venus is online, over the Internet. There is also a VRM portal app if you don’t want to use the full browser version.

You are right though - it’s mostly for analyzing energy trends in the system.

I have a 16G card in my CCGX as well... I think you can store 200 decades of data on the 16GB card
That's interesting, I didn't know you can get real time data as well. That might be nice not to have to change to a different wifi hotspot to get info from the Venus.
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Old 06-15-2018, 09:03 AM   #85
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Hi

Ok so this is a bit obscure - just what *can* you do with the remote console on the Venus and how easy is it to do this or that via the internet? Can some random bored teenager play with the settings on your charger?

Bob
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Old 06-15-2018, 10:41 AM   #86
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Hi

Ok so this is a bit obscure - just what *can* you do with the remote console on the Venus and how easy is it to do this or that via the internet? Can some random bored teenager play with the settings on your charger?

Bob
What I can say is by default two-way communication with your trailer is turned off so unless you turn that on all that you see on the remote console is data it has collected, you can’t control anything.

it has the usual password to get in. Plus you need to know the unique 10ish alphanumeric code for your unit.

I’m sure there are more interesting hacking targets out there but anything is possible.
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Old 06-15-2018, 04:51 PM   #87
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Thank you for this, Bob. This does require an explanation.



In our experience most customers that want to use lithium in their RV are the type that want to be plugged in the least amount possible. But we understand your question and have highlighted it below.


Concerning leaving the battery at high SOC…there has been concern among some folks that leaving the batteries at high SOC would leave the cathode at a consistently high potential, which could potentially accelerate the aging process by increasing the rate of chemical reaction between the cathode material and the electrolyte. This is something that we were concerned about as well. It turns out that the LiFePO4 cathode material is remarkably resistant to high SOC (see, for example, Electrochimica Acta 62 (2012) 256–262). This is probably because it operates at a lower voltage than the other Li-ion chemistries. But to be sure, we did our own experiments where we left that pack sitting at 14.6V for extended periods of time, and we did not see any discernible decrease in capacity. This also agrees with some computations we did in house, where we modeled the long-term capacity degradation based on modeling the chemical reaction rates on the cathode. Because of this, we are not recommending that it is necessary to keep the pack at a lower SOC.


In regards the the charger comparison, we have simply instructed the user how to program or how each device works with our batteries. There are many components out there that work great with our batteries.


Concerning low SOC, all of our long term cycling tests involve taking the cells down to 2.2V. That will not harm the cell. However, long-term storage of the batteries at low SOC is a bad idea, because the self discharge of the batteries (about 3% per month) could take the cells down to unacceptable voltages over time.




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Hi

The Battle Born low voltage cutout is spec'd as "9.0 to 10.5V". There then is a note about "many converters need to see over 10V to charge". I take that to mean that they really may not cut out until 9V. That is taking each cell bank down to 2.25V.

They did some discharge runs against 12V batteries and there really isn't much capacity left at 12V. ( = you loose nothing with a 12V cutout)

https://battlebornbatteries.com/comp...teries-series/

Most published data suggests that 2.5V is the "may damage" point for these cells. At 12V you are well above that, at 9V ... not so much.

To me the $100 is pretty cheap compared to damaging a battery .... Yes, I have had things go flat. One of the repair guys left a switch on. I also camp a lot in the shade..

Indeed this *is* the flip side of the "max charge voltage" question. That still is ( at least to me ) an open issue.

Link to their video endorsing 14.6V all the time chargers:

https://battlebornbatteries.com/prog...tery-chargers/

Link to their video endorsing setting up for *not* 14.6V all the time:

https://battlebornbatteries.com/powe...po4-batteries/

( = that charger can run either in fixed output or multi-stage mode ).

So yes, just as on the "high voltage end" you can go several ways, there are ( at least to me ) multiple choices on the "low voltage end".

Bob
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Old 06-15-2018, 05:00 PM   #88
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Thanks for your question. Please see our previous post concerning high SOC. We have not observed adverse affects with high SOC storage. Actually, the voltage curve is very steep at high SOC, and the self-discharge of the cells actually brings the voltage down fairly rapidly.


About our cycling tests - we do all long-term cycling tests at 100% DOD. That corresponds to cycling cells between 2.2V and 3.65V. We have observed that capacity degradation scales more with charge rate than anything else. At a 1-hr charge rate, the average degradation is 20% at 2000 cycles. At a 5-hour charge rate, the average of 20% degradation occurs over 3000 cycles. In fact, if we take cells that have degraded to 80% after 2000 1-hour cycles, and then continue cycling those at a lower charge rate, the rate of degradation is significantly slowed.





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Nice support here from battle born. In today’s world, customer experience and customer support are the differentiator!

Question for you while we have you on this topic - I’ve certainly read that the LiFePO4 chemistry does not like to be “kept at” or “floated at” or “stored at” 100% SOC if your goal is maximum lifespan. I’ve read for instance that they are best stored / used at between 50-90% SOC ... especially when storing a full battery at temperatures above 25C.

Can you comment on your testing / research / findings regarding battery lifespan / cycle life as it relates to constantly “floating” a LiFoPO4 battery at 100% until its time to actually use its reserves? Can you also comment regarding how battle born battery lifespan is affected by cycling between 100% and 20% SOC vs say 100% and 50% SOC?
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Old 06-15-2018, 05:32 PM   #89
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I think people are forgetting Battle Born's initial business model. Which, in my opinion, was to supply a drop in replacement for existing flooded cell or AGM batteries.


Does that mean that their batteries will be optimally utilized, absolutely not. What is does mean is that, even with sub-optimal charging/usage devices, that their batteries are better than the alternatives.

They are a new company, and from what I have observed, are dedicated to building on their initial successes and are not afraid to interact with their customer base.

Will they branch out into more sophisticated batteries and BMS's, I hope so.


PS: I am in no way affiliated with Battle Born.

Pat
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Old 06-15-2018, 06:49 PM   #90
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Quote:
Originally Posted by uncle_bob View Post
Hi

My observation is that the 5V applies the first time the device is powered up. Why it exists ... no idea. '

Bob
Probably to provide hysteresis so when the sun comes up it doesn't start trying to charge until there's enough sun to be somewhat assured it won't turn on and off and on and off.
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Old 06-15-2018, 08:02 PM   #91
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Thank you for this, Bob. This does require an explanation.



In our experience most customers that want to use lithium in their RV are the type that want to be plugged in the least amount possible. But we understand your question and have highlighted it below.


Concerning leaving the battery at high SOC…there has been concern among some folks that leaving the batteries at high SOC would leave the cathode at a consistently high potential, which could potentially accelerate the aging process by increasing the rate of chemical reaction between the cathode material and the electrolyte. This is something that we were concerned about as well. It turns out that the LiFePO4 cathode material is remarkably resistant to high SOC (see, for example, Electrochimica Acta 62 (2012) 256–262). This is probably because it operates at a lower voltage than the other Li-ion chemistries. But to be sure, we did our own experiments where we left that pack sitting at 14.6V for extended periods of time, and we did not see any discernible decrease in capacity. This also agrees with some computations we did in house, where we modeled the long-term capacity degradation based on modeling the chemical reaction rates on the cathode. Because of this, we are not recommending that it is necessary to keep the pack at a lower SOC.


In regards the the charger comparison, we have simply instructed the user how to program or how each device works with our batteries. There are many components out there that work great with our batteries.


Concerning low SOC, all of our long term cycling tests involve taking the cells down to 2.2V. That will not harm the cell. However, long-term storage of the batteries at low SOC is a bad idea, because the self discharge of the batteries (about 3% per month) could take the cells down to unacceptable voltages over time.
Battlebornli:
Seems like you'll need to put a few more words around your recommendations to new users and tell them how to program their systems. Do they just run their chargers at 14.5v flat out all the time and the same for solar or is that just something that they CAN do with the possibility of diminished battery life? I was told by you folks to float them at 13.5v and charge at 14.5v which is what started this whole journey into smarter charging systems. I'm still happy with where I ended up (with the Venus controller) but that solution is an expensive one for many if they don't have the full Victron stack and the wherewithal to connect and program it. Perhaps articulating the tradeoffs clearly could help users decide. I was led to believe it wasn't even an option to not float at 13.5.
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Old 06-16-2018, 09:15 AM   #92
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Hi

Ok, so now we *do* have some definitive information on this from Battle Born ... THANKS !!!

If I have a 400AH bank, I would need to charge them at 400A to hit a "1 hour rate". To hit a 5 hour rate I would do an 80A charge. At least I believe that is what is being said. If so, neither rate will ever be hit by my setup. It would be nice ( but not essential ) to know what even lower charge rates do.

The high voltage (and low voltage) information does indeed clarify things a bit. Now the question becomes 14.2 / 14.4 / 14.6 volts. It's not real clear to me that there is a lot of capacity lost charging at 14.2 vs 14.6.

Some information on the "use case" here:

The trailer sits in storage for much of its life. That *is* a shame, but it also is reality. Part of the year it gets out and about. As soon as it pulls out of the indoor storage, the solar comes up. Probably 50% of the time, the batteries are running on the solar setup. The rest of the time, they either are on the DC/DC from the TV or on the charger / converter. Indeed, the batteries *could* come out of the mix once the charger / converter gets them up to full charge. That is not how it is set up ... yet.

I suspect that there are a *lot* of RV's that fit a similar use pattern.

Again - Thanks !!!

Bob
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Old 06-16-2018, 12:02 PM   #93
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We apologize for the miscommunication. We did not mean to mislead you in anyway. We try our best to make sure everyone gets the right component for their application. Can you give me a call Monday or PM me your number so I can call you and we can talk about this. I will make it right for you.

Sean
Quote:
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Battlebornli:
Seems like you'll need to put a few more words around your recommendations to new users and tell them how to program their systems. Do they just run their chargers at 14.5v flat out all the time and the same for solar or is that just something that they CAN do with the possibility of diminished battery life? I was told by you folks to float them at 13.5v and charge at 14.5v which is what started this whole journey into smarter charging systems. I'm still happy with where I ended up (with the Venus controller) but that solution is an expensive one for many if they don't have the full Victron stack and the wherewithal to connect and program it. Perhaps articulating the tradeoffs clearly could help users decide. I was led to believe it wasn't even an option to not float at 13.5.
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Old 06-16-2018, 10:40 PM   #94
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Operating voltage may be 18V max, but “open circuit” voltage is ~22V.
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Old 06-17-2018, 08:29 AM   #95
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Hi

Looking at Vmax in the history plot, it does appear that the MPPT only wakes up in the morning when it sees a 5V delta. Sitting here under the trees and a cloudy sky, the panels somehow made it to 18.3V already this morning. Not sure how much good the 0.6A I'm getting will do, but every little bit helps. Three days 19 hours left

====

Does anybody know what the "back feed" current is into the Victron charger / inverters is when fully powered down? ( = not inverting / not charging )

Bob
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Old 06-18-2018, 05:10 PM   #96
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Thanks for calling today. I am glad we cleared that up that you are actually talking about a Solar Charge Controller and not a charger.

UPDATE***We wanted everyone to know that we also believe there is a part in Dale's system that is not reading voltage properly causing his Victron charge controller to behave differently that all the other ones we have in use.

Dale was able to over come the issue using the Venus from Victron.

But for most people this not a necessary part to use lithium. Just the BlueSolar or SmartSolar and the BMV700 series monitor will work just fine.

Our recommended settings are different for each customer based on the devices they use to recharge and how those devices behave when charging. The best thing I can recommend is to call us or reach out here with questions.

When it comes to a solar charge controller you have a little more latitude because its not charging 24 hours a day. Here is an example of a common part: Some GoPower Charge controllers float at 13.8 volts, no big deal on a Solar Charge controller.

Generally you can find success with these ranges

Bulk and Absorb 14.2-14.6 volts
Equalize: Below 14.6 volts (most are on manual equalize these days)
Float: 13.6 or lower
Absorption time: about 0.5 hours per 100ah of power

Remember if you have a question just ask we are happy help anytime, even if your not our customer.

There are some devices that charge on a fixed profile like the Progressive Dynamics Converter, these run at 14.6 volts. They work fine with out batteries.

Some have asked if holding this high voltage will shorten the lifespan of the battery, not true under normal circumstances. There are many other chemistry's some that might have an issue with this, but in our experience most customers that buy lithium are staying unplugged as much as possible, otherwise they would not invest in lithium. Long story short most people that make the investment to upgrade to lithium are not going to be plugged into park power for months at a time.
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Old 06-18-2018, 08:34 PM   #97
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We are typically not concerned with charging below a .5C rate, at 80 amps you at a .2C rate. These rates of charge will not shorten the batteries life span outside of normal degradation.

We typically test all of our batteries charge and discharge at a 1C rate and we see a 25 to 30% loss after 3000 cycles.

We do test at the lower rates and you can expect to see this "normal" degradation many cycles later.

Due to a few variables, your lower recharge rate and the fact that you are most likely not fully cycling the battery every time you use it. Its hard for me to say exactly.

Every case is different in the real world but you will get more cycles than our testing for sure. We would estimate you would be closer to 5000 cycles before seeing that 75% capacity remaining mark, in most cases.

On leaving the Airstream in storage, best bet charge up the batteries to full, use your disconnect switch and let them sit. You don't need to plug in, these lithium's hold a charge very well. The self discharge rate is low. This means you can roll out anytime and the batteries will have power left in them. Just make sure you disconnect the bank, in case you leave a light on or something.

Sean
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Old 06-19-2018, 12:24 AM   #98
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Quote:
Originally Posted by battlebornli View Post
Dale
Thanks for calling today. I am glad we cleared that up that you are actually talking about a Solar Charge Controller and not a charger.

UPDATE***We wanted everyone to know that we also believe there is a part in Dale's system that is not reading voltage properly causing his Victron charge controller to behave differently that all the other ones we have in use.

Dale was able to over come the issue using the Venus from Victron.

But for most people this not a necessary part to use lithium. Just the BlueSolar or SmartSolar and the BMV700 series monitor will work just fine.

Our recommended settings are different for each customer based on the devices they use to recharge and how those devices behave when charging. The best thing I can recommend is to call us or reach out here with questions.

When it comes to a solar charge controller you have a little more latitude because its not charging 24 hours a day. Here is an example of a common part: Some GoPower Charge controllers float at 13.8 volts, no big deal on a Solar Charge controller.

Generally you can find success with these ranges

Bulk and Absorb 14.2-14.6 volts
Equalize: Below 14.6 volts (most are on manual equalize these days)
Float: 13.6 or lower
Absorption time: about 0.5 hours per 100ah of power

Remember if you have a question just ask we are happy help anytime, even if your not our customer.

There are some devices that charge on a fixed profile like the Progressive Dynamics Converter, these run at 14.6 volts. They work fine with out batteries.

Some have asked if holding this high voltage will shorten the lifespan of the battery, not true under normal circumstances. There are many other chemistry's some that might have an issue with this, but in our experience most customers that buy lithium are staying unplugged as much as possible, otherwise they would not invest in lithium. Long story short most people that make the investment to upgrade to lithium are not going to be plugged into park power for months at a time.
It was great taking to the folks at Battleborn. They really are a class act and care deeply about their customers.

The bottom line is they believe in normal circumstances if the batteries are floating at 13.5 at full charge they should drop down to 13.2 by they time you are at 80% state of charge which SHOULD be enough to cause your solar charge controller to spring into action and try it’s best to get the bank back up to 13.5. You ought to see this activity on your battery monitor or the solar charge controller’s panel if you have one. I didn’t see that but it sounds like normal people should. If you don’t give them a call. That is assuming you want load support durring the day and aren’t just satisfied with the batteries charging up first thing in the morning.

I personally feel better having a central controller watching state of charge and doing the right thing mixing power from different sources but that’s just my geeky engineering brain working overtime.

I think we all already know this but be sure to never leave your expensive lithium batteries online while the trailer is in storage. Always have a master disconnect to absolutely take them out of the circuit. Not doing so will prematurely age your batteries for no good reason.
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Old 06-19-2018, 08:57 AM   #99
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Hi

My *only* concern at this point is the 13.2V "float" mode on the converter / charger that I happen to own. I have empirical data ( BMV 712 readouts ) that would suggest that my particular setup is still above 13.23V at 75% capacity. That just *seems* like a lot of cycling to me.

Yes, I could call. Oddly enough the cell signal here at this campground is almost good enough for internet but not good enough to make a phone call that does not drop after 10 seconds ....

Bob
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Old 06-19-2018, 10:00 AM   #100
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Hi

Does anybody know what the "back feed" current is into the Victron charger / inverters is when fully powered down? ( = not inverting / not charging )

Bob

Bob,


The Victron Datasheets list the Self Consumption for most of their Charge Controllers at 10mA.


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