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Old 12-05-2012, 18:59   #406
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Hi T1 Terry,

Glad to see you back on this thread. I have been studying all the previous posts and really appreciate all the good info you and others have posted here. I am also considering adding the Cell logger so I can be more involved in monitoring my bats but I have a question. Will the logger be able to read the individual cells when they are in Series? Or should I just install one for the 4 Parallel strings of batteries?

Thanks for your help.

CJ
The Junsi cell logger 8 will handle 1 to 8 sets of paralleled cells connected in series, this covers 3v to 24v systems. The units will display paralleled cell voltages to 3 decimal places, has adjustable alarm functions for high cell voltage, low cell voltage, high pack voltage, low pack voltage a differential voltage between cells. It has an alarm port that can trigger a relay to cut charging voltage, cut non essential loads, set off an external higher volume alarm.... what ever function you can think of.... all for $14 or $28 for a unit that can also monitor up to a mth or mores battery voltages for all cells monitored and display it a graph or as a table chart. This is very useful for maintenance assessing, if a set of parallel cells drop voltage more than the others under load yet register higher voltage than the others while charging it clearly indicates this is an aera that requires further attention. Generally nothing more than a loose terminal bolt or corroded connection, fixed at this stage it’s fixed, left till cell failure causes a lot more problems. If a shunt balance BMS system is continually covering up this issue it won’t appear until cell failure occurs.
If an alarm sounds then generally most people will go and see why, the cell logger flashes what parameter set off the alarm so it can be attended to, the human brain is the battery management system, the cell logger merely reports what's happening.
The question is, do you have 100% faith in a system still under development? Or do you trust your judgement ability to decide the correct course of action if an alarm goes off? $28 and your brains or what ever $$ and a system with no guarantee of success or financial restitution for failure, which looks the better deal?

If the EV community are removing their already purchased BMS systems to me it says a lot about their faith in them.

T1 Terry
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Old 12-05-2012, 19:09   #407
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Nothing funny here, Genasun is too expensive, there is no point for us to design a system at same price range as Genasun as we would be in direct competition in a very frugal and small market. So we had a simpler and cheaper system to offer, but now that this market is growing and more people are getting into LiFePO4 it makes sense economically for us to offer a more flexible system, but still at very affordable price point.
Genasun is a whole different kettle of fish, a sophisticated dual battery system giving a full redundancy capability is one battery system should fail, expensive yes, but too expensive? Your system isn't offering anything like the Genasun system does is it so how can you use it as a comparison?
Never a good look try to make your system look better compared to another, it should be able to stand on it’s own merits shouldn’t it?

T1 Terry
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Old 13-05-2012, 06:44   #408
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Nothing funny here, Genasun is too expensive, there is no point for us to design a system at same price range as Genasun as we would be in direct competition in a very frugal and small market. So we had a simpler and cheaper system to offer, but now that this market is growing and more people are getting into LiFePO4 it makes sense economically for us to offer a more flexible system, but still at very affordable price point.
Makes sense. For the DIY folks that want (and are able) to put together their own system. Genasun has also sold BMS-only kits to those that want to get their own cells, build the racks, etc.
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Old 13-05-2012, 10:00   #409
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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If a shunt balance BMS system is continually covering up this issue it won’t appear until cell failure occurs.
This is not true and it shows your lack of basic understanding of BMS systems.

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If the EV community are removing their already purchased BMS systems to me it says a lot about their faith in them.
This is another baseless and false statement from the top of a soap box.


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Never a good look try to make your system look better compared to another, it should be able to stand on it’s own merits shouldn’t it?
First off I never said my system is better, I said its simpler and cheaper, learn the difference. Is Cadillac better than Honda? Is apple better than orange?

And there is nothing wrong with comparing different systems based on true specs and features, not just some dramatic statement from the top of a soap box.
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Old 13-05-2012, 17:04   #410
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Quote"
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I do agree that BMS is not absolutely required on 4S banks if handled properly, but at the same time investing a small extra capital in a simple system which serves as insurance policy, is a wise thing to do."


If you are that confident your BMS will not kill cells but instead save them from damage (isn't that the reason for fitting a BMS in the first place?) then give a full battery bank replacement guarantee with every one of your BMS units fitted. Until you are willing to do that you are practicing and fine tuning your gadgets in the market place at the customers peril. If a BMS is not really needed for a 4 cell series system then why would someone spend the $$ and take the risks?
If a cell shunt fails to the “on” condition, how does your system turn it off? Isn’t it true that any such failed unit must be removed from the cell to stop it continually discharging that cell to the point of cell failure?

T1 Terry

Maybe you missed this post Electric1 as you haven't mentioned the level of faith in your own product to offer the guarantee I mentioned...... could there be a problem?


My knowledge comes from a lot of research over many yrs including a wealth of knowledge from the true lithium guru, jay Whitacre, and 12mths of hands on testing and either verifying or debunking various untruths being spread by some with a vested interest in these myths continuing.

(1) Cells do not go out of balance with each other if a sensible max charge voltage is maintained
(2) There is no more capacity to be gained after 3.4v per cell rested voltage
(3) 4 cell unit packs built as parallel/series packs will self balance as load and charging is applied as long as they were balanced from the beginning.
(4) Shunt balance systems need the cells to be balanced in the first place as their ability to discharge over capacity is very limited due to heat issues.
(5) Shunt balancing systems also need special charging systems so the charge rate can be reduced to a lower value than the shunts max load capability, this makes them none compatible with normal charging systems.

Basically, a shunt BMS system will maintain a battery bank in balance that would have remained in balance anyway, therefore they are not necessary and an added risk component completely nullifying the KISS principle that all good systems use. Why add complication and error points to a system that simply doesn't need it?
I have no financial vested interests in the knowledge I offer, can you say the same thing?

T1 Terry
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Old 13-05-2012, 18:02   #411
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Maybe you missed this post Electric1 as you haven't mentioned the level of faith in your own product to offer the guarantee I mentioned...... could there be a problem?
I didn't miss it, I just chose to ignore it because it's asinine. Why would I offer a warranty for a product I don't sell? ( battery itself ). Show me one company in the world that warranties someone else's product. Completely unreasonable. However, I work with several battery dealers who package my BMS with their cells and then offer much better warranty than if cells alone were sold. I have faith in my product based on 100s of customers with positive feedback and not a single return over 3 years. There have been warranty claims, no one is perfect, vast majority are installation mistakes though, which we still fix under warranty unless they are blatant errors covered to death in the install manual.

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My knowledge comes from a lot of research over many yrs including a wealth of knowledge from the true lithium guru, jay Whitacre,
Well, unfortunately a lot of your "knowledge" is false, but I have no time or desire to educate you. The video posted by professor Whitacre is excellent, but most people don't understand critical details of it because he can't cram entire course of electrochemisty in such short timeframe. You have shown in many of your posts that you don't understand some important points, but I am sure its just a matter of time if you choose to keep an open mind.

As for BMS for housebank, I have always been saying, its an insurance policy for the most part, to protect the pack from the user himself. If you are meticulous and have time on your hands to babysit the battery, don't buy anything other than DVM. But, if you want to have a life outside of the battery compartment, get a simple BMS and move on.
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Old 13-05-2012, 18:25   #412
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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I have no financial vested interests in the knowledge I offer, can you say the same thing?
This kind of attitude is the main reason I chose not to post on forums. For some ridiculous reason people think that best advise would come from someone without vested interest in the subject. Its the most retarded logic ever.

When I need advise or want to learn something, I want to hear from most vested people, since they made the subject their business and hence have true knowledge. Why would I want to learn from some armchair self-proclaimed expert who played with one battery and suddenly knows everything?

I think most people here are smart enough to see thru a sales pitch when they see one, so I don't feel any shame in sharing my knowledge despite being in the business of designing, producing and selling BMS systems. But after I encounter this resentment and attitude from people I am trying to help, I'd rather just go away and spend my valuable time elsewhere.
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Old 13-05-2012, 18:37   #413
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Whew, relax guys! As far as I can tell, most everything both of you say is true (on the tech side) however different perspectives can eventually reach different answers.

Regarding warranty, I don't think I'd be selling (mostly) Genasun if they didn't cover everything in the system. Cells & all. However, having that level of security probably adds to the cost, so I can't say that's the only way to go for everybody.
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Old 14-05-2012, 06:40   #414
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

I'll leave it at that Electric1, you obviously must need to make a living from what you sell so I'll leave it up to the customers to decide, derogatory remarks don't actually help your case, especially when they are so far off the mark.
My 720Ah house system, the 180Ah demo pack and all the systems I have helped set up don't use a BMS system and they all function as designed with no out of balance issues over the last 12 mths, that speaks for itself. Set the system up properly from the beginning and it won't cause you any grief, they look after themselves as far as balance as long as you don't over voltage charge them, no need to be continually watching them, the $28 cell logger does that for you.

T1 Terry
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Old 14-05-2012, 07:29   #415
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Regarding warranty, I don't think I'd be selling (mostly) Genasun if they didn't cover everything in the system. Cells & all. However, having that level of security probably adds to the cost, so I can't say that's the only way to go for everybody.
For those of you looking for a complete LiFePO4 package with warranty, google search "Lithionics Battery". They offer wide variety of batteries for any application, with integrated BMS.
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Old 14-05-2012, 09:23   #416
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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I'll leave it at that Electric1...
You made a lot of good posts here and shared a lot of good info, kudos to you for taking the time. I only intervened when you slipped into false rhetoric, which serves no purpose and only pushes people away from true knowledge.

Lets stick to facts and numbers and leave empty rhetoric to Internet trolls
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Old 14-05-2012, 11:22   #417
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Hi Electric 1. Your BMS has worked very well for me so far. My system is not set up correctly because if my battery SOC is high and we have a hot cloudless day and i am not on the boat , my outback charger over charges and your BMS kicks the solenoid and the charge is stopped till i reset....so its saved my Hi-power LifePO4 a few times already
My question is : any idea why the outback flexmax 60 does not go into float mode ?
and could it be that i have one supercell which is lower than the other 3. I have 600a , 12 x 200ah high power. I tried to balance them but found it long and tiresome . As soon as one super cell was going red and i would bleed it down , trying to get the lagging cell up , then one of the other super cells would turn red and i was jumping from cell to cell , back and fourth...all this at 3am in NC in mid winter out in the cockpit of the boat.
So for the past 5 months , i have been living with one super cell out of balance.I have 3 kyocera 240 w panels
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Old 14-05-2012, 11:31   #418
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

I also use a link 10 monitor. When i am 300 ah in the neg , my SOC reads about 13v. This is pretty close to flat i think. I have a 600ah bank. 80 % = 480ah
Does this sound right
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Old 14-05-2012, 11:39   #419
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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My question is : any idea why the outback flexmax 60 does not go into float mode ?
I just downloaded user guide for Flexmax 60/80 , on page 23 there is a setting for Absorbing and Float voltages. What do you have these set to? Chance are you have one or both set too high, hence tripping HVC.

I recommend to set Absorbing to 14.2V and Float to 13.6V

at 13V you still have plenty of energy left in the bank, you can easily drive it to 11.8V and still have reserve capacity left.
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Old 14-05-2012, 11:45   #420
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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...all this at 3am in NC in mid winter out in the cockpit of the boat.
So for the past 5 months , i have been living with one super cell out of balance.
Yes, initial balance can be tedious, but its only done once. You have been on the right track, just didn't see it thru. Maybe get back to it on a nice summer day when you have some spare time? You might have been very close to finish when you stopped it.

Nothing wrong with imperfect balance as long as you have cell level BMS protection and don't drive your bank to empty every cycle. Imperfect balance simply means you would not be able to get rated bank capacity if you ever needed it, since least charged cell would limit at the bottom and most charged cell would limit at the top. BMS would prevent you from over-discharging former and from overcharging latter, so no harm done.
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