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

[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.

[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.

[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

[solar pete]

Get lost SPAMMER

Its OK SK I sorted him

[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

[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.

[Willy T]

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

http://minibms.mybigcommerce.com/

[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.

[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.

[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.

[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.

[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.

[danewguy]

Thanks SK. thanks a ton.

So it's interesting your references to the EV market. Through some input from some other guys on an EV forum, they posited that the entire BMS I got is actually from Clean Power Auto. Not just the display. - also the head guy, or at least someone official with them is marked as stating that in the past they had indeed sold those systems to Balqon, or at least one of their people (where I got the bank). And interestingly enough also, Balqon's main demographic is and has been EV's. not sure if it's just the California region or beyond.

Raj. - point on the warranty. However, were I to legitimately end up having a warranty issue, due to the state of the company, barring aggressive and personal legal involvent I doubt it would or could ever be addressed. After all. For 6 friggin months I have been unable to reach them just to get a user manual OR warranty info. They have completely relocated their warehouse and operations. And evidently for the last few years they have been in financial upheaval flirting with bankruptcy. So, once I learn a whole lot more I almost will feel more confident in dealing with things myself. Starting with a worthwhile BMS and dealing with the corrosion on the bus bars. Sigh...

Thanks Dax. Good info.

[karrak]

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?

The CleanPowerAuto HousePower BMS and MiniBMS cell modules (thanks Willy T for working that out, is this the same BMS as in your system?) that are installed in danewguy's system will disconnect the battery if any cell gets above 3.65 volts or bellow 2.6 volts via the round black relay/contactor and will also provide a LVC signal below 2.9 volts which could be used to switch off the inverter and a HVC signal above 3.6 volts which could be used to shut down the charge controller. The MiniBMS cell modules will balance the cells at 3.55 volts, so all in all the current setup will provide the appropriate protection for the battery, see here for more details http://minibms.mybigcommerce.com/tem...ower%20BMS.pdf. The only thing this BMS does not provide is a readout of the individual voltages.

To date, the BMS that is part of danewguy's system has not flattened the battery or made it go out of balance so I can't see any reason for changing it.

The Orion Jr. BMS is a very nice unit but is it worth the $425 plus to get the extra functionality which could be obtained much more cheaply with a device that just reads out the voltages?

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.

Only problem with this charging regime is that it only charges the battery to around 80% so you are wasting about 10-15% of your accessible storage capacity. The vast majority of currently installed systems that I know of charge to around 3.45 volts/cell (55.2 volts) which will charge to above 90% with no ill effects. Raj, I am intrigued to know what voltage and end current you charge your battery to?

Simon

[Willy T]

CleanPowerAuto HousePower BMS and MiniBMS cell modules (thanks Willy T for working that out, is this the same BMS as in your system?)

It work's as advertised, as was posted if someone feels they need individual cell voltage, then it's probably not for you, buy something more sophisticated. I find in stuff I buy that some features you buy a more expensive unit for end up being something I never use anyway.