LiFEPo4 sitting several months NOT hooked up = freaking about self discharge = Brick?

[dax]

Thanks SunKing.

Should I still get a charger that has a connector for BMS? Or will a regular charger meant for Lithium be fine?

Someone had suggested perhaps unconnecting everything and hooking them up parallel for a day or two to let them all equal out. Do you suggest that?

Do you have any advice for a good quality BMS? It'd be nice to have one that had a good display that I could see the individual cell voltages and perhaps something that would give me some control. That is, once I know enough to not screw things up.

We have some lifepo4 50amp cells which have been sitting for 4 years and started of at 3.5v, this is a part of our proving tests to determine lifespan and SOC over time. So far none of the cells has dropped below 3.2v and they are all within .02v of each other. I also have a lifepo4 36v bike battery pack, which is more than 6 years old I bought as a backup for mine, but so far have never used it and it still has 3.15v. Reading this thread reminded me of it so went and checked it.

Lifepo4 cells tend to be very stable and maintain their charge for long periods, depending on how they go, expect the test cells will still be sitting there in a few more years and hopefully still have a usable SOC. These tests are being done under controlled, stable environmental conditions at 21deg, which can be simulated in any off grid connection to give a long stable life. Our installations come with pack temp controls and anyone using lifepo4 should do the same if they want them to really last. They don't handle charge discharge below 0 deg, or over 25. The best range we've found is 18-25deg and 21deg seems the best so far.

As for a BMS, we use our own and the same with chargers, we have them built for our purpose and are not satisfactory for the DIY, as they are sealed from the customer. There are very few dedicated lifepo4 BMS, those available are mainly for Li-ion or Li-poly which have very different charge parameters for lifepo4. Lots of sellers claim to sell lifepo4, but they are li-ion and have higher charge voltages compared to lifepo4. plus shorter life and no where as stable or safe and you should pay more for real lifepo4 cells.

A DIY needs a BMS which has active cell balancing, including bleeding, plus adjustable charge and discharge parameters. Whilst you are finding these things, have a look at ebay, they sell cell voltage alarms which handle 8 cells. All you need extra is a couple of relays and a small 5w cell bleeder. When one cell reaches the upper charge limit, it will switch the relay and disconnect the charge. This way no cell will go over and the rest will be pretty close, if not you may need to check your cell connections and how you charge them. We found over the years, lifepo4 likes being charged at the 4 points of the pack, this seems to keep cells very close together and if you have a load during charge sequences and balanced your cells at 3.2v, or preferably 3.5, they will stay pretty much in balance. I contend cell voltage alarms are the most essential requirement for the DIY lifepo4 user and they are cheap.

It's not rocket science, just very different to lead acid and once you understand how they perform, it's basically set and enjoy what they provide for your energy needs.

[Sunking]

Should I still get a charger that has a connector for BMS? Or will a regular charger meant for Lithium be fine?

That is an Oxymoron question. Any Lithium charger worth having will have some sort of interface with a BMS. The trick is there is no Industry Standard of what Protocol the Interface should be. The Auto EV Industry is the only sector that has a Standard so you can use a Charger from one Manufacture, and a BMS from another manufacture. For RE there is no standard as of yet. Just no demand for Lithium batteries. What little is out there is al proprietary. So the Thing to do right now is use a charger and BMS made for EV's. However if your intention is to use solar to charge the batteries you are going to have to figure out how to integrate a BMS.

Someone had suggested perhaps unconnecting everything and hooking them up parallel for a day or two to let them all equal out. Do you suggest that?

That someone was me. It was a conditional statement, the condition was if the batteries are way out of balance. It does not appear your batteries are way out of balance. With new batteries, you have to perform an Initial Balance aka Bulk Balance. To do that you connect all cells in Parallel and walk away for the day. That will passively Middle Balance the cells. From there you must choose between Top Balance or Bottom Balance. To Top Balance requires a special charger to do the Initial Top Balance. You leave the batteries in parallel and use a 3.6 volt 50 to 100 amp charger.

Some try to use a BMS to do the initial Top Balance with a Charger. The problem with that approach it takes a long time to do that. The Bypass current on all BMS is very small in the range of 150 to 500 ma. On something like a 180 AH battery like you have the difference between the highest and lowest cell can be 30 to 50 AH. So when the First cell reaches 100% SOC, the Charger has to limit current to what the Balance boards can bypass. So if the Balance Current is say 200 ma, and the lowest Cell still has say 40 AH to go, will take 40 AH / .2 Amps = 200 Hours to charge.

Do you have any advice for a good quality BMS?

Yes I do, an Orion Jr. It is a 16 Channel Centralized BMS which means it is made with a 16S battery (48 volt). It has a Coulomb Counter (Fuel Gauge) which takes a Shunt to make it work, monitors Cell voltages and Temperatures, and is programmable so you can pretty much interface it to anything. It has Can Bus Protolcol an automotive standard so it can communicate with a charger and all aspects of an EV. It can easily be made to work with a Midnite Solar Charge Controller.

Click this link. It is a BMS finder and has every BMS known to man listed. Just input your requirements and it will tell you all the BMS available. Next CLICK THIS LINK and start reading. If you go all through the tabs and read everything, you will be an expert on anything Lithium Battery.

[Raj]

danewguy,

The batteries are fine, and fairly well balanced. They should be ok for months to come. Just take weekly voltage readings on the batteries to monitor any change.

You paid a lot of money for this system. Surely they are covered by a warranty, right? If so, then changing it in any way will void the warranty. Just something to think about.

[danewguy]

Thanks SunKing.

Should I still get a charger that has a connector for BMS? Or will a regular charger meant for Lithium be fine?

Someone had suggested perhaps unconnecting everything and hooking them up parallel for a day or two to let them all equal out. Do you suggest that?

Do you have any advice for a good quality BMS? It'd be nice to have one that had a good display that I could see the individual cell voltages and perhaps something that would give me some control. That is, once I know enough to not screw things up.

[Sunking]

Hey Guys,

attached are some close up pix of the BMS from inside the black box, the sensors, and the silver box with holes in it.

attached is also the map of readings. The organized blocks looking one is the bottom level, and the jigsaw puzzle looking one is the top level.

my multimeter read the bank total as 52.4v.

Listed out the readings are:

Top:
3.278
3.283
3.277
3.276
3.280
3.276
3.281
3.278

Bottom:
3.274
3.277
3.276
3.275
3.277
3.277
3.275
3.278

thanks.

First thing is your batteries are just fine. They are roughly at 60/70% SOC.

As for the BMS, get rid of it. It is what is called a Distributive Mini BMS which means it is two parts. Vampire Boards called Cell Boards, and a Controller which does not do much other than operate a relay to Disconnect the batteries or Shut off a charger. What Cell Boards does it use? Do you have the relays?

Anyway you can charge the batteries with no real problems if you can set the Charger Float Voltage. Set it to 54 volts and no worries as you will be well below 100% of 57 volts. Never let it go below 48 volts.

[Willy T]

I believe the Head Board and Cell Boards are from CleanPowerAuto.

http://minibms.mybigcommerce.com/

[danewguy]

Hey Guys,

attached are some close up pix of the BMS from inside the black box, the sensors, and the silver box with holes in it.

attached is also the map of readings. The organized blocks looking one is the bottom level, and the jigsaw puzzle looking one is the top level.

my multimeter read the bank total as 52.4v.

Listed out the readings are:

Top:
3.278
3.283
3.277
3.276
3.280
3.276
3.281
3.278

Bottom:
3.274
3.277
3.276
3.275
3.277
3.277
3.275
3.278

thanks.

[karrak]

So, new updated plan... tomorrow I chart out and log each individual cell and then I'll post back for ya'lls thoughts.

It would be good to get all the separate cell voltages. I will be surprised if you find anything out of the ordinary.

I did find a couple of chargers online that have integrated BMS. If I were to need to get one of those then at that point I guess I'd need to figured out how to hook it into the battery bank's.

I wouldn't rush into getting any special equipment until all the details of what you currently have has been worked out and you have worked out a long term strategy. At worst you might want to keep just the batteries and dump the rest of the electronics in the box and replace them with something better, or you might be able to use some of the electronics that is currently there. I think it is likely that you will be able to leave your battery until you get your solar gear installed and use this to charge the battery.

I looked up the accuracy specifications for your multimeter. It is 0.5% for DC voltage readings up to 400 Volts. This will mean that the readings could be wrong by up to 0.25 volts at 50 volts and 0.015 volts (15mV) at 3 volts which is not fabulous but is OK.

It appears that my current BMS is this one here:

This is only part of the BMS that is currently installed with the battery. What is under the black box marked "MASTER CONTROL BOX" is a major part of the BMS. If you could take the cover off and take some photos of what is underneath that would be useful. Could you also get some better photos of the black BMS modules connected to the groups of individual cells. We need to work out the details of what these and the MASTER CONTROL BOX do.

Simon

[solar pete]

Get lost SPAMMER

Its OK SK I sorted him

[Sunking]

Having the goods is a start depending where you are I may be able to help you. I and my colleagues train, install and maintain many Solar systems with and without batteries we will use any type but obviously have our own preference.

Get lost SPAMMER

[Sunking]

It appears that my current BMS is this one here:

http://minibms.mybigcommerce.com/tem...er%20Guide.pdf

That is not a BMS. It is a EV Fuel Gauge and a poor one at that. It is a volt meter with a Fancy Name. It measure cell voltages, pack voltage, and cell temps. That is it. It does not Balance or manage a charger. It is a Cell Monitor, not a BMS.

Your monitor needs an additional 12 volt battery or converter to work. IMO is completely worthless.

[Chas-KniFe]

Having the goods is a start depending where you are I may be able to help you. I and my colleagues train, install and maintain many Solar systems with and without batteries we will use any type but obviously have our own preference.

Admin Note, welcome to Solar Panel Talk, newbies advertising themselves or company is against the rules, dont do it again or you will get banned.

[danewguy]

Ok. Dude, ur a master! Thank you. Sincerely.

So, new updated plan... tomorrow I chart out and log each individual cell and then I'll post back for ya'lls thoughts.

I did find a couple of chargers online that have integrated BMS. If I were to need to get one of those then at that point I guess I'd need to figured out how to hook it into the battery bank's.

It appears that my current BMS is this one here:

http://minibms.mybigcommerce.com/tem...er%20Guide.pdf

[Sunking]

Hey guys,

I switched on the enclosure today and I'll list the exact results below. The display has 2 buttons side by side that each cycle through a top or bottom row of basic info. Without a manual, I assume they reflect the top and bottom level of batteries inside??? Or maybe they both represent the whole so you can check two different numbers at once. Cause both rows said the exact same thing as I cycled through both buttons.

" 0 A "
" 0 W "
" 52.4 V "
" 66F Tmp "
" 1.0 Ah "
" 52 Wh "
" E F "
" 0% Fuel "
" 0% SoC "
" 0 A "

OK all this info is bogus except the Voltage and Temperature. Everything else from the BMS is gibber jabber garbage. At 52.4 volts is an INDICATOR the pack voltage is OK. It does NOT MEAN all the cells are OK. You need to measure and record every cell voltage on a spread sheet. Then look at them all and find the highest and lowest cell voltages. If the range is .05 volts are less you are in fairly good shape, and your BMS might be able to balance the cells. If the range is greater than .01, then you will need to disassemble them, and reconnect all of them in parallel and walk away for a day to let them equalize. Look very carefully for any queer cell voltage. If you find one get rid of it before it blows a cell. A queer cell will be one radically different than all the others, especially any 3 volts or less. If any are at 2.5 or less, you have problem. At 52.4 volts hopefully you will not find any cell less than 3.25 volts or greater than 3.3 volts.

A) condensation on all the cross bars bridging cells. (stupid question, but how do I wipe them off without shorting anything out or electrocuting myself???)

OK this is not very good news, but not a show stopper. It means the batteries were improperly installed, and you need to fix it. Whoever installed them did not use an Anti-Oxidant grease. Bad mistake and poor workmanship. Buy you a small tube of San Chem No-Ox-Id A Special grease. Remove all the intercell-bus bars off the batteries, and apply a light coat of the grease. VERY LIGHT COAT. Be sure to put a light coat on the battery term post. Also use it to coat all wire skinners before compressing terminals. Do this and you will never have any corrosion problems for 50 years.

Pro-Tip: Put the grease in a pan and heat it up until it melts. Then brush on bus bars and dip wire skinners. Also apply a light coat to all power connection points. Again a VERY LIGHT COAT

B) the black squares on every 3 cells (8 on each level = 16 total) (the BMS Sensors???) were all blinking, even though I had the battery bank turned off.

C) the top row and the bottom row had 24 cells each. So the whole bank has a total of 48 cells. (Is that 1 cell for each of the 48V that the system is?)

OK this tells me you have a 16S3P battery. 16S means you have 16 cells wired in series. Each cell is 3.2 volts. So 16 x 3.2 = 51.2 volts aka 48 volt battery. 3P means 3 in parallel. You have Vampire Bleeder Boards with cell temp monitor, the curse of any BMS. You have one Vampire board to Bleed 3 cells in parallel, and you have 16 Vampire Boards. Need to know what BMS and Vampire Boards you have to tell you what the Blinking Light means. You should be able to figure it out yourself. Otherwise tell me what make and model they are.

I went by Home Depot and got a $99 Klein Multi Meter. - Depending on your advice I'll try to check the cells tomorrow. From the looks of the inside of the enclosure I'm not sure how many of the bottom row I can actually reach.

You must measure every cell. Otherwise sale everything you have and get rid of it. You have 16 voltage measurements you must make. One measurement will read 3 cells in parallel. But you must know what each cell voltage is before you can do anything. If they are out of balance, you have a major project on your hands. Refer to above about putting all cells in parallel and walk away for a day.

I'm still trying to figure out where I can actually go buy a 48v charger in person instead of having to order one online and wait. Even if I have to drive an hour away to get one. But if this thing is "dead" would there be any special instructions or specific charger to trying to revive it before officially pronouncing it a lost cause?

Thanks

Very bad idea at this point. You need a charger that can interface with your BMS, and you need to know what the Bypass Current is of the Vampire Boards. Your batteries have sit for a long time. The Vampire Boards bleed your batteries 24 hours a day at different current rates. That throws your batteries out of balance. Most Vampire Boards can only make very small corrections of about 150 ma to 500 ma. We have no idea what you have. For each 1 AH out of balance takes 7 hours to correct with a 150 ma Vampire Board. You have a large battery with 3 parallel cells of what looks like 180 AH total. It is very likely you could have as much as 20 AH out of balance. It would take your BMS 133 hours to balance, and can only do that if it can communicate with your charge to limit current to what the Vampire boards can handle. If you exceed that limit, you will severely over charge over half of your cells and damage them, and/or start a fire. This is why you must know the cell voltages before you do a thing as that will determine your corrective action plan. Don't take it lightly. At a minimum your batteries are at risk if you make a mistake. At most your life and property is at risk.

[Mike90250]

Only charge it for a couple hours, then stop and check things . My bad, I'd thought you said you measured 48v, but I'd misread your post. So it's not ultra critical. But if the batteries in the center of the bank are still below freezing (I don't know the local temps) you can't charge lithium batteries below 0 C