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Old 06-08-2014, 14:30   #31
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Re: Baqon drop-in LiFePo battery systems with BMS

The DIY crowd using the BMS to control the high voltage and low voltage cut out. So if we use the data from Mainesail on the winston cells, and his BMS.
The house BMS is set for a high cutout at 15 volts With a warning at 14.2
Maine has found it best based on testing to charge at 13.8 to 14 volts.
The BMS is essentially a safety device rather than a charge controller based on what Ive seen so far in these banks. This is not to say that a BMS could be more it's just that the multiple charging sources in use on a cruising boat add further complication.
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Old 06-08-2014, 15:00   #32
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Re: Baqon drop-in LiFePo battery systems with BMS

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Maine has found it best based on testing to charge at 13.8 to 14 volts. .
Main Sail can certainly comment, but he is running his tests more in a lab/data collection style than how a cruising boat may actually operate. Meaning, he is looking to count cycles by turning his charge sources on and off. While this is great for data gathering, it's also not how it works on a real cruising boat. (now everyone this is in NO WAY a ding on Mail Sail, he is a great guy and deserves many kudos for the time and energy he puts into his testing and willingness to share it). On a real cruising boat, solar is always charging during the day, alternators are charging when under way, shore power is plugged in while at the dock, and a wind generator is charging when the wind blows.

It's this active charge/discharge condition that I think needs more thought and focus rather than the on/off charging when gathering data for cycle count. In this condition, a simplier charge value could be 13.4v. Why not set all of your charging devices to 13.4v and all but eliminate the risk of over-charging by using 13.8v or 14v? Alternator, Solar, Wind, Battery Charger, and Flux capacitor, just set them all to charge at 13.4v.

Sure you should still have your high and low cell alarms, but this way you effectively have taken away the over-charge issue. Because at a 13.4v charge voltage on a cell with a 3.33v resting voltage (13.4/4=3.35)...well you can't put any more amps into the battery once you reached that resting voltage. Easy to do, easy to set-up and no risks. I have not seen data that says charging at 13.4v vs 13.8-14.0v hurts the cells. So what is to be gained by charging at a higher value and then dropping back down to a lower valve for "resting" or turning off the charge, since there is no "float stage" on a LiFePO4 bank the way we think of it on a Lead Acid battery.

I think this need and want to adjust charging voltage and resting voltage comes from the Lead Acid mindset and in all honetly is part of the BS Marketing of why you need a Gazillion Dollar BMS in the first place! Let's make it sounds like rocket science and scare people to death or better said into buying our BMS that has this fancy 7 stage battery charging and conditioning...again the old Lead Acid Games that may not apply here.
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Old 06-08-2014, 15:09   #33
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Re: Baqon drop-in LiFePo battery systems with BMS

I want a BMS for monitoring cell temp and discontinuing charge if temp gets high, and for cell balancing.
This mindset may come from using LiPo and old style wet Nicads but I can't see any harm in monitoring for a thermal runaway, nor in balancing cells, and it ain't hard or expensive to do.
Low voltage cut out shouldn't be necessary either, but everyone either has or will someday walk away from their boat leaving something on that they didn't intend to , be it a light in the engine compt or a fan or something that if left for days would deeply disharge the battery if it were not for the BMS
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Old 06-08-2014, 15:27   #34
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Re: Baqon drop-in LiFePo battery systems with BMS

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Originally Posted by SV THIRD DAY View Post

I think this need and want to adjust charging voltage and resting voltage comes from the Lead Acid mindset and in all honetly is part of the BS Marketing of why you need a Gazillion Dollar BMS in the first place! Let's make it sounds like rocket science and scare people to death or better said into buying our BMS that has this fancy 7 stage battery charging and conditioning...again the old Lead Acid Games that may not apply here.
I agree to some extent, now to be clear I haven't tested these banks myself. I'm fairly new to the whole LiFePo world but I have read some as well as talking with some friends in the battery and charging side of the marine world. Most agree that you can steady charge a LiFePo bank at a constant voltage I hear varying number but lets just call it somewhere between 13.2-13.9 volts.
I think the real trouble with a drop in solution, is the many chargers out there that are not adjustable to that type of charge regime. Also the alternators present another issue which can be solved with a good regulator that can adjust the voltage and keep the alt from destroying itself but again not a drop in for most boats out there.

The BMS as I said before isn;t really a charging device rather it's a safety feature to prevent problems with the bank. In reality we should have BMS systems on large lead acid banks too. I think you are starting to see some of that now, in fact I get more requests for low voltage cutouts for conventional banks every week.

Again this is not the most complicated thing in the world but it's still not dropping in a Lithium battery for your old Exide.
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Old 06-08-2014, 17:02   #35
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Re: Baqon drop-in LiFePo battery systems with BMS

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.... Why not set all of your charging devices to 13.4v and all but eliminate the risk of over-charging by using 13.8v or 14v? Alternator, Solar, Wind, Battery Charger, and Flux capacitor, just set them all to charge at 13.4v.
Simple, ohms law will tell you that you won't get charge rates anything close to 1C unless the voltage is higher. Now you're back to longer charge cycles like you're trying to get away from using LA.
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Old 06-08-2014, 17:20   #36
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Re: Baqon drop-in LiFePo battery systems with BMS

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Simple, ohms law will tell you that you won't get charge rates anything close to 1C unless the voltage is higher. Now you're back to longer charge cycles like you're trying to get away from using LA.
That sounds good on paper...but it's also not the reality I am seeing here in real life with a 400AH battery bank charging at 13.4v. Not to pick on you Don, but in my opinion this type of thing is why engineers can calculate all day long but then not look up from the Hp 48G calculator long enough to see if the numbers they are crunching make any sense in a real world application. What does "1C mean" with my 1380W of solar, KISS wind generator, 100A alternator, and 60A Sterling procharge battery charger?
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Old 06-08-2014, 18:58   #37
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Re: Baqon drop-in LiFePo battery systems with BMS

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That sounds good on paper...but it's also not the reality I am seeing here in real life with a 400AH battery bank charging at 13.4v. Not to pick on you Don, but in my opinion this type of thing is why engineers can calculate all day long but then not look up from the Hp 48G calculator long enough to see if the numbers they are crunching make any sense in a real world application. What does "1C mean" with my 1380W of solar, KISS wind generator, 100A alternator, and 60A Sterling procharge battery charger?
You are not going to fool physics. Given unlimited charging capacity, it will take longer to reach full charge @13.4v than it does @13.8v. And, yes, that's called ohm's law. Your comments makes one think you are using all your charging capacity @13.4v.
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Old 06-08-2014, 19:24   #38
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Re: Baqon drop-in LiFePo battery systems with BMS

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You are not going to fool physics. Given unlimited charging capacity, it will take longer to reach full charge @13.4v than it does @13.8v. And, yes, that's called ohm's law. Your comments makes one think you are using all your charging capacity @13.4v.
There's no such thing as "unlimited charging capacity" on a boat...maybe in a Lab, but not a boat and that is the reality we are talking about here right? Or are we drifting into theoretical? That’s fine if we want to have a theoretical discussion, but that’s a completely different ball game from the systems on a boat.

The trick is applying Physics from the text books to the real world, which is where many folks go wrong. I see it almost every day when distraught cruisers show me their excel energy balance spreadsheet which shows on paper they should have plenty of battery power. Then the cold hard truth of applied physics kicks them in the ass when they wake up and see their Lead Acid battery bank at 12.1v in the morning.

Your concern about it taking "longer" to charge at 13.4v compared to 13.8v or even 14.0v....yes...but do you know what that means in real life terms? What does our buddy Ohm tell us about that and does it mean anything to a cruiser with a 400AH LiFePO4 battery bank? (hint…it’s a great trade off to guarantee top end battery protection when most of the data shows playing with the top end knee of the charge curve is bad juju.)

Maybe I wasn't clear enough about the 13.4v Charge level...I AM using 13.4v for all of my charging sources. There is no worry of coming back to the boat after a Taco Run Trip to Mexico for a week and finding my $1700 400AH bank fried. If it's gonna be a viable technology for a cruising boat, then it needs to be as KISS as possible, at least that's my thinking and product philosophy. Some agree with that approach, some call it Pollyannaish, and I’ve certainly been called worse at times when my smart-ass-warped sense of humor leaks out…ha ha ah
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Old 06-08-2014, 19:39   #39
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Re: Baqon drop-in LiFePo battery systems with BMS

I got one can't tell what full charge is... I'm either putting amps into the battery of taking them out ...


Sent from somewhere other than where I want to be!
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Old 06-08-2014, 19:55   #40
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Re: Baqon drop-in LiFePo battery systems with BMS

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I got one can't tell what full charge is... I'm either putting amps into the battery of taking them out ...
That's what a Good Amp Meter is for.....

Sing it with me...K.....I......S.......S........
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Old 06-08-2014, 20:24   #41
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Re: Baqon drop-in LiFePo battery systems with BMS

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There's no such thing as "unlimited charging capacity" on a boat...maybe in a Lab, but not a boat and that is the reality we are talking about here right? Or are we drifting into theoretical? That’s fine if we want to have a theoretical discussion, but that’s a completely different ball game from the systems on a boat.

The trick is applying Physics from the text books to the real world, which is where many folks go wrong. I see it almost every day when distraught cruisers show me their excel energy balance spreadsheet which shows on paper they should have plenty of battery power. Then the cold hard truth of applied physics kicks them in the ass when they wake up and see their Lead Acid battery bank at 12.1v in the morning.

Your concern about it taking "longer" to charge at 13.4v compared to 13.8v or even 14.0v....yes...but do you know what that means in real life terms? What does our buddy Ohm tell us about that and does it mean anything to a cruiser with a 400AH LiFePO4 battery bank? (hint…it’s a great trade off to guarantee top end battery protection when most of the data shows playing with the top end knee of the charge curve is bad juju.)

Maybe I wasn't clear enough about the 13.4v Charge level...I AM using 13.4v for all of my charging sources. There is no worry of coming back to the boat after a Taco Run Trip to Mexico for a week and finding my $1700 400AH bank fried. If it's gonna be a viable technology for a cruising boat, then it needs to be as KISS as possible, at least that's my thinking and product philosophy. Some agree with that approach, some call it Pollyannaish, and I’ve certainly been called worse at times when my smart-ass-warped sense of humor leaks out…ha ha ah
I really don't care, I'm not arguing with you, I simply picked up on your expressed displeasure of absorption charging time of LA and pointed out that you could decrease charging time with your LifeP04 by increasing the voltage. That's not theoretical, that's physics. You can do what you like.

Is there any evidence of the long-term effects of charging LifeP04 at 13.4 vs 13.8 vs 14 ???
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Old 06-08-2014, 20:49   #42
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Re: Baqon drop-in LiFePo battery systems with BMS

No arguing Don...that's a problem with reading writing vs talking.

I'm just trying to make sure things are clear because you have to remember how chat rooms work. One reader can easily take your comment about Ohm’s Law (because anyone quoting Physics Laws is an expert on a chat room we all know that) and your theoritical rate of charge and then the next thing you know this guy becomes the local LiFePO4 battery dock expert saying:

"more volts is better...heck it charges the battery faster...so if 13.8v is good...14.8V is better…Ohm’s Law and all".

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Old 07-08-2014, 04:35   #43
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Re: Baqon drop-in LiFePo battery systems with BMS

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If it's gonna be a viable technology for a cruising boat, then it needs to be as KISS as possible, at least that's my thinking and product philosophy. Some agree with that approach, some call it Pollyannaish, and I’ve certainly been called worse at times when my smart-ass-warped sense of humor leaks out…ha ha ah
I have an interesting job in that I work exactly on the boundaries between the theoretical guys and the real world guys.

The engineers do "optimize" or at least have "controlled" laboratory environments. I am sure you agree they must have that to do apples to apples comparisons. We do lots of testing and try to simulate everything but it is still not the real world where there is variation.

What you are skirting around is what we would call operability margin. That is, how far back do you dial a technology in order for it to be safely and reliably operable in a wide variety (all?) of conditions by a wide variety of skilled and not so skilled persons.
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Old 07-08-2014, 05:33   #44
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Re: Baqon drop-in LiFePo battery systems with BMS

So who knows the relative charge rates for 13.4 and 13.8V?
Is the relationship linear or exponential?
Are we talking about 20% longer to reach a full charge or 50% longer?
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Old 07-08-2014, 05:39   #45
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Re: Baqon drop-in LiFePo battery systems with BMS

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No arguing Don...that's a problem with reading writing vs talking.

I'm just trying to make sure things are clear because you have to remember how chat rooms work. One reader can easily take your comment about Ohm’s Law (because anyone quoting Physics Laws is an expert on a chat room we all know that) and your theoritical rate of charge and then the next thing you know this guy becomes the local LiFePO4 battery dock expert saying:

"more volts is better...heck it charges the battery faster...so if 13.8v is good...14.8V is better…Ohm’s Law and all".

Point taken, but you also have to consider...

"Rich is a smart guy and says 13.4v will never cause a fire, so that must be best."

When in fact your LifeP04 will die prematurely due to lack of proper charge voltage.

But, what do those stupid engineers know???
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