Discussions about LiFePO4 cells and Battery University

I assume/believe the molex/bms connection on one is shorted for sure aka 1-8s is how the product is labeled. I could never get a good celllog reading other than some 25vdc for a 24vdc pack. Plus some of the cells on celllog threshold where way above 3.2vdc to 3.7vdc range

 

FYI for Enginer owners -- I received a reply from Jack about the BMS16D HVC levels. It does require a firmware update that can be done by Ecotronics. I just sent my BMS off for updating (they charge $30 for the service, plus I had to ship it). I am aware of the balance issue. I built myself a switch box with which to do manual balancing (I can select a cell and add charge or discharge it through a 1 ohm, 50W resistor), which makes it a bit less painful.

So it seems to me that if I get the HVC of the BMS fixed and keep things balanced, I am okay now. Unfortunately I now have a weak cell in my pack.... Grrrr. My local installer will fix it for me, at least (for a price!).

 

Hey if do not mind post image of your s-box and material list thanks

There are cross over chargers that come from the RC ebay market . Icharger and cellpro come to mind. If you have bottom balance these correctly . Why is the BMS16d necessary for discharge? Also some1 please explain what the term/process hand/manul balance is?

LiPo Balance Battery Charger and Discharger Icharger 3010B 1S 10S | eBay
iCharger 3010B 1000W 10s Balance/Charger

 

"Manual" balancing is balancing that is done by a person who attaches loads or power supplies to individual cells or groups of cells by hand, as needed to bring a pack into balance. The opposite would be "automatic" balancing, which is done by a BMS of some sort or another with no direct human intervention.

 

For me, I simply view the log files every day (approximately, anyway). I pay attention to how high my total pack voltage gets before one (or more) of the cells climbs up to HVC. If things are so out of balance that the charger doesn't reach CV mode, then I attach my box, dial in the high cells (one at a time), and drain ~1 Ahr from each of them. If there is one cell that is bottoming out at the end of the discharge cycle and causing a LVC before the total pack voltage gets to the point where the converter shuts down (45.6V for mine), then I will add a bit of charge to the low cell. The problem is when the same cell is the high one causing HVC during charging and the low one causing LVC. That means you have a weak cell that is limiting your pack capacity.

I'm sure I could've found something commercial that I could use to do the manual balancing, but the process is conceptually so simple that I decided to make my own. I had a lot of the components lying around, so in that respect I saved some $$$, too.

 

I also found this DC Constant Voltage Constant Current Regulated Power Supply 60V High Voltage | eBay
which would be good for a monitor charge of Lifepo4 pack.

 

Hi WBK9,

I am in the process of acquiring some A123 20AH cells for a battery pack. My Chinese supplier has ran out of cells except for these A123 cells which have no marking. The supplier claims that the cells were supplied when A123 went bunkrupt and were unfinished during production so they were not marked. The supplier sent me a photo of these unmarked A123 20AH cells, photo is attached.

I find it odd that both tabs are copper and not plated. The copper tabs will oxidise.

I have no reason to doubt the honesty of my Chinese supplier (don't laugh!).

What is your expert opinion on these cells and do you think they are genuine?

Thanks,

John


UPDATE

My supplier has sent me a new photo of the unmarked A123 cells (previous photo was probably not same A123 cell). These cells in the new photo have plated tabs and look genuine. Photo is attached.

 

What are you defining as loads and am curious why you skip the part of my question of discharge.

 

Sorry, I laughed pretty hard for a second there.

I highly doubt these were built by anyone at A123, and they are definitely NOT production cells from before, during, or after the bankruptcy. The tab material, as you correctly point out, is completely wrong. Those tabs also look really thin--dangerously so for a high-current application. Even the ones that have the right color are much too wrinkled to be the right thickness. The rest of the cells look pretty convincing though, at least in the photo. In-hand, who knows? It would be interesting to compare performance, but you can't really do so without lending a hand to skullduggery, at least not without significant, public, follow-up. How much are they asking for these, and are they promising the same performance?

When I ignore your questions, it's almost always because the grammar is so twisted up, I cannot figure out what the question actually is.

A load is a resistor or any other device you can strap across a power source (in this case, a cell or group of cells) for the purpose of drawing current. Few nouns in electronics are more basic or ubiquitous than "load", which leads me to the other reason I sometimes don't answer. You ask questions that are already answered in the thread, or are so basic that it's clear your grasp of electronics is tenous at best. There is a lot of literature on the web on this subject. Start by googling "Li ion battery balance schemes". If the academic engineering papers that come up are over your head, find some more basic literature on electronics, read that, then go back and read the more advanced stuff again. You should be reading, not writing.

 

Your ability , background, mindset is just empowering. So I am learning grammer from A123 bankrupt company employee ...........why thank you
In regards to your (just opinion)responses ..
If you want pick and choose what to respond to (which everyone does) I have no issue with that and also no response works too . Just seeking insight about DISCHARGE.

Let see so you found the misspelled(word) china company name (covered that)
You found bankrupt ownership issue (okay)
OH you missed this one the Livonia (taxpayer wasted money) facility .Oh yes the facility was touted to create new green jobs in USA and thats not really working out (HOW?) from a bankrupt A123 company
OH the dastardly Chinese(no worries here) red army never cyber spies on anyone

Yea got those covered now thanks

How about RFE 24VDC 80ah(Lifepo4 20ah cells) that was top balanced charged to a point where the BMS(molex connection)connector (JST 8S) is shorted (darkened) and got burn/blackend (jacked up) . How do I repair that connector to start or not

since that was missed/skipped

 

My guess here is that you somehow got two sense lines shorted together and burned up your harness with massive current. Replace the wires and/or connectors. Why on earth do you need me or any other "expert" to tell you that? Lack of basic knowledge is the only answer I can come up with, and I don't have the time or inclination to teach you how to strip and crimp a piece of wire. You really should stop playing with big boxes full of energy that you don't understand before you hurt yourself or a member of your family. If you can't figure out how to put a load on a battery cell to drain it of charge, or how to replace a simple connector, then you've got no business trying to build an electric car--none.

I've already said I don't know enough about the physical makeup of the Enginer packs to tell people how to tear them apart and repair, so I can't help you there. From the pics I've seen here, these modules are sealed and have almost zero serviceability, so you may have to just scrap the module and replace it.

I thought you would probably find my post insulting, but I call 'em like I see 'em--always. I'm not a diplomat. When it comes to technical issues, I try to stick only with the unvarnished truth. That post has already snagged a "like", so it seems I'm not the only one around here who feels this way. Insulting as my post may have been, I sincerely hope it was no more insulting to you than it is to others to post unintelligible questions laced with partisan political rants and then having a tantrum when you finally get some honest answers you don't like. My patience for it is now fully exhausted. Good luck.

 

Actually already familiar with load . Apparently you have no method or process to be suggested on how to pull down a charge on individual cell aka load.
"A load is a resistor or device "

resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element.
The current through a resistor is in direct proportion to the voltage across the resistor's terminals.
I = V/R

"A load is a resistor or device " what?
More empowering and intellectual double talk . I have a grasp of what has merit and value. Not really finding that with your posts.

More insight thanks again....
FYI
Some of these threads(this thread) and posts are by PChat members that do have Enginer products .Additionally some have BMS16 (automatic)(your word) by enginer. The reality is the BMS16 is not automatic(although marketed that manner) and has charge and balance issues which several OPchat members including Lopez have touched on. Sadly the automatic (your word) has ruin cells and damaged Lifepo4 enginer packs.

Fisker vehicles have had fires which required the the local fire department. Your (double speak) sheds no light on that and one would need a filing of Freedom of Information just to begin to know the details of those incidents.
thanks again

 

Both battery packs have chemistry that has Li.
Even this battery had automatic(your word) BMS design by a team of professionals. Sadly the balancing,charging, and BMS functions did not automatic(your word)prevent the destruction of the pack or cells.

 

Lets or let us start to untangle or undo the twisted(your word) a few of the post you have made. Just so we can
call em(your word) and varnish(your words) something maybe of a technical concept, process, and thread focus.
Start with your varnish(your word)background

Okay,let see you have working knowledge of high school grammar, english, and spelling.
Think we have covered that issue even though had no focus of the thread. So lets push on into the math, science ,technology, and forum thread and posts .

Okay call'em(your word) on the topic of A123 and Hymotion L5
Let see both corporation have demised and cease to function under those corporate banners. A non disclose agreement you undertook makes any comment you make suspect and with little or no merit. Comments on charge and discharge specs of individual product A123 cells is therefore tainted and of no value. Any opinion or comment on similar or other manufacture of Lifepo4 cells and you have no common or critical working knowledge. Curious do you work at the former lab of A123 or just corporate marketing because that would make some of the comments more in line with your posts and less tainted.

 

Fisker fire investigation info.

Fisker completes investigation of latest Karma hybrid EV fire, issues vehicle-wide cooling fan recall

The Texas and California fires were attributed to an overheating cooling fan in the engine compartment, a device driven by the 12V battery. The Li battery had no involvement whatsoever.

Click the "show press release" button on the page to see the details.

 

Well said Tony,

thing is this thread has some great info on lifepo4 batteries and their characterisitcs from a guy who works with them daily, a person that can contribute and help greatly for others to understand how to manage and care for their packs. I have for sure learned alot form reading this thread and hope this doesnt put off wb9k from helping others with their batteries and how to monitor / care for thier valuable assets that are lifepo4 batteries.

Regards, Anthony.

 

I must concur with the previous post. Wb9k has added significant information to folks who own and now must fix their own Enginer systems. Solid technical information is difficult to come by for this class of battery. I for one don't care about the abstract theory of Lithium technology. I need to know how to fix it when it breaks

I have a question concerning temperature of operation. Here in New England it can get quite cold, staying below freezing for several days in a row. I find that unless I apply extraordinary measures, my battery pack does not work well below 32F. If it gets much colder than that, it doesn’t work at all, so I leave the system off until we get a day in the low 40s. I can force the issue by warming the pack with a couple of old heating pads overnight. However, that gets old quickly.

I have the older Mott cells with 4 KWh of capacity. The system was installed in May 2010. I can’t find any information about the electrolyte used in these cells, but I assume it must be water-based. Perhaps it is some other chemical that inhibits ion exchange reactions at the freezing point of water.

In any case, I assume that this is not a generic problem with Lithium technology. I have not heard any comments about problems with using the Plugin Prius Lithium battery in cold weather. Do the newer Real Force batteries have the same problem I have?

Paul

 

Hi Paul,

Thanks for the kind words. All batteries are affected by temperature and none of them like extreme cold. Most batteries perform better at higher temperatures (within reason), but most batteries also age faster at high temps. Thermal management is pretty important, especially for a traction battery that may see high and low temperature extremes as part of its normal life.

I don't think there is a great deal of difference among most LFP electrolytes, but I'll keep my comments limited to A123 products. The electrolyte contains no water, but is VOC-based. The real world does get cold enough to begin to freeze it, but not until well below the freezing point for water. The numbers you give, however, are pretty extreme and may indicate another sort of problem--maybe a sense wire or some electronic component is losing connectivity at these temps, so the BMS won't play nice? You don't give details about how the systems becomes inop, so it's hard to say much more, but the cold shouldn't shut down your drive capability until you're well below 0 degrees F.

Below freezing, you should expect that the range capability of your pack will decrease, and the colder it gets, the worse it gets. This is primarily due to a natural rise in cell output impedance as temperature falls. (I don't know enough about the precise electrochemical mechanism to give more detail). This is worst (for us anyway) when the vehicle is stone cold. As the cells deliver drive power, they self-heat and impedance gradually falls to what we're used to seeing at warmer temps. Charging times will be extended a bit (or more) as well (more on that below). OEM plug-ins I'm familiar with address this problem by heating the coolant in the pack's cooling plate when plugged in at low temps, so the batteries are always warm enough to give good performance when you unplug.

Cold temps are a greater hazard to the cells during charging. As temperature falls, the amount of charge current a cell can handle without plating Li also falls. At -40 degrees C, allowable charge current is near zero. If your BMS does not compensate for this, it could be very bad for the calendar life of your cells. Again, OEM plug-ins have strategies for dealing with this with minimum disruption, but the DIY-er needs to be aware of these issues as the consequences of ignoring them are not trivial.

Hope that helps.