Help with seting over volt disc. and charge limit on MT50

projectile

Hi All
Please help me before I kill me batteries.Lifeop 
I want to change me over volt disconnect to 28.7 and my charge limit to 27.7 volts
When I try, I get PARA.Error and the mt50 will not save my changes.

Thanks

mcgivor

You need to stop charging now, the cells are way out of ballance, if the BMS?? is attempting to ballance the cells it may take extremely long  days, weeks, months or even years, depending on capacity.

The Para.Error appears to be the controller has reached its charge limit, the battery voltage 28.86V would indicate that, the value accounting for voltage drop, or the lowest setpoint available is >27.7V  . With so little information along with being unfamiliar with the controller these are only guesses at best. All I can say for sure is 710 mV spread is too much, the cells need to be ballanced properly, there is the risk of fire if there is no control via a BMS.

projectile

HI Mcgivor:
I am using the system found here https://www.mobile-solarpower.com/2000-watt-24v-solar-system.html
Minus The ATS, no 24v to 12v converter and no Battle born batteries

I  have two 325 watts poly solar panels in series.
40 amp mppt Epever charge controller
mt50 remote monitor
victron energy battery 100w 24v it is set to option A8: under voltage shut down 24v
                                                                                      under voltade restart 26v
no other bms
I  have an eight s battery monitor which shows me the volts of each cell.

the 8th cell is where the main positive is located. Its voltage does not change much. from 3.296v to 3.353v
I would wondering if it is bad.

I hope this will help you help me

mcgivor

Whilst it is possible to operate without a BMS, I personally don't recommend doing so, lithium batteries should be controlled at a cellar voltage level not a bank voltage. When there is imbalance the battery as a whole will be the combination of all cells in series regardless of individual cell voltage, so a cell which is far from full capacity will cause the ones at higher capacity to increase, potentially into the danger zone.

The reason cell 8 is not rising is because cells 5 & 6 are close to maximum capacity driving the bank voltage to where the controller is satisfied then stops charging. This is potentially hazardous you need to disassemble the bank discharge each cell to approximately the same voltage to prevent high current transfer when connecting in parallel for top ballancing. 

There are 2 methods of ballancing bottom and top, only one can be done one involves dischargeing each cell to its lowest allowable voltage then assembling the pack, which is commonly used in EV applications. The other involves charging each cell to its maximum voltage wit all cells in parallel. The top method requires a single cell charger which drops the current as the voltage approaches maximum, much like a BMS would do, at the upper limits the cell voltage can increase extremely rapidly if current isn't reduced. Such chargers are available for ~$40, once all are fully charged they are reconnected in series, this is typically used in solar applications.

You really need to address the ballance issue first, because operating without doing so is dangerous, especially with LiPo cells which are not as forgiving as some other chemistries, lifepo4 for example.

There are other things with the attached link which are of concern but those are not as important.

This like provides a wealth of information especially in the white papers. 
http://liionbms.com/php/wp_parallel_balance.php

This is for charger https://m.aliexpress.com/item/32872106786.html?pid=808_0000_0105&spm=a2g0n.search-amp.list.32872106786&aff_trace_key=1f5a158981114b37ab6b64f7fe2fc8e6-1564382013135-00741-KnSGCh6&aff_platform=msite&m_page_id=3051amp-ZXkLFFJjLTwwvWd9Q8WQJQ1564556895275

projectile

HI Mcgivor:
I am using the system found here https://www.mobile-solarpower.com/2000-watt-24v-solar-system.html
Minus The ATS, no 24v to 12v converter and no Battle born batteries

I  have two 325 watts poly solar panels in series.
40 amp mppt Epever charge controller
mt50 remote monitor
victron energy battery 100w 24v it is set to option A8: under voltage shut down 24v
                                                                                      under voltade restart 26v
no other bms
I  have an eight s battery monitor which shows me the volts of each cell.

the 8th cell is where the main positive is located. Its voltage does not change much. from 3.296v to 3.353v
I would wondering if it is bad.

I hope thiswill help you help.

projectile

Hi Mcgivor:

Corrections My victron Battery protect is 100A not w

My 8 batteries are connected in series.
 

I have 8 LiFePO4 3.2V 100Ah 320wh connected in series to run a 24v system.

I would like to learn how to bottom balance the batteries. I will follow your steps. But I think need a set of resistors to quickly draw the power down on each cell. my cell balancer will take years to do it. The cell balancer, to me, is only good for seeing the volts on each of the 8 cells.

I was trying to follow Mr. Will videos and website to use a 24v relay and Daly separate port bms but I could not figure out where one red wire from the relay should connect.

Do you know of an inexpensive BMS that I can attach to this battery? 

When the battery is drained down(26.3v) the cells are within 50mv does that mean anything?

Why does the battery drain quickly from 28.8v to 26.5 and stay at 26.3v with me running tv, router, lights, and computer laptop?

Thanks so much for your help

 

projectile

when it starts
 to charge the cells look balanced
I will disconnect the PV until I balance the cells, find/build a  BMS

mcgivor

Lifepo4 makes a difference, the image of the cell monitor shows LiPo. Ultimately it changes nothing, the cells need to be ballanced, ballancing is a time consuming process whichever method is chosen, personally I recommend top ballancing, it works better with solar controllers and there is no need to flirt with the lower end, unlike with EV applications.
 
Read the linked white paper about ballancing, it's really important to understand this procedure, top ballancing  will require a single cell charger and is probably the safest method given the charger controls the current, things happen rapidly at both ends, also known as the knees. The regon between the knees is a very flat regon of the charge/discharge curve, this will explain why you see a rapid decline in bank voltage between 28V and 26.3xxV. The cells may appear to be close during the flat part of the curve but may increase in difference as they approach the lower knee.

The reason I use the word may, is because I'm assuming you have not ballanced the cells one way or another, my recommendation is to stop using the cells / battery until they are properly ballanced, then discussion on charging and dischargeing can be discussed, along with the BMS requirements. Take time to do it right, don't rush into this, it may seem complicated at first but it's actually quite simple once there is an understanding of the dynamics.

To select a BMS the following information is required, battery type, obviously Lifepo4, battery capacity, maximum charging current and maximum discharge current. Other details such as wether a display is needed and or computer monitoring is a requirement, these are  are personal preferences which don't nessersary determine the quality of the equipment but is nice to have.

So to repeat myself, go slow, ballance the cells, then move on to the next step, patience is a virtue, the rewards will speak for themselves. 

projectile

Ok
I will order the stuff to top balance the cells.

Sinopoly batteries by Ruixu Max charge should be 3.65volts each

I have stopped charging and discharging the battery 
Thanks for the explanation on why quick voltage drop. It makes sense to me.

projectile

you can see the battery specs here

https://smile.amazon.com/gp/product/B07PV5FCYX/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

mcgivor

The thing to do before ballancing is to discharge the cells to a voltage ~ 3.280V individually before parallel connection. This 
https://www.aliexpress.com/item/32870792884.html?spm=a2g0n.store_allProduct.allProducts_11109905.32870792884 is the charger I used, it takes a few days to reach fully charged because 50% of 800 Ah is 400Ah @3.6V. The charging will begin at 14A but begin to reduce as it nears full capacity right down the mA range in the final stages. My ballancing was on 32 × 100Ah  cells, took about a week to complete.

This is another useful link worth reading  http://nordkyndesign.com/assembling-a-lithium-iron-phosphate-marine-house-bank/

Do you have any BMS in mind ? The one I use is attached pdf cost was around $110 including shipping. The image in the pdf is incorrect there are seperate charge and discharge ports, othwise identical.

projectile

I had ordered the first charger 4.2v that you listed but had to cancel it and get the one you just listed.

I don't have a BMS in mind.
if the lws will work for me I will order it esp if it is coming from China and will take a month or 2 to get here.
My cells are right now at:
3.277
3.286
3.282 
3.294
3.286
3.330
3.289
3.275

How do I drop the volts on the ones that are still too high?
Buy resistors and connect them to that cell?
If so what size resistor should I get?

Raj174

@projectile
Warning, this method is a PIA. I used 3.3 ohm 10 watt ceramic resistors with my cells. They will draw about 1 amp per hour out of the cells. Monitor this closely. It's like watching molasses in winter, but if you forget and leave it connected too long, the result will be more time and effort getting them close.

https://www.amazon.com/uxcell-Power-Resistor-Ceramic-Cement/dp/B07CWSH3F8?psc=1&SubscriptionId=AKIAILSHYYTFIVPWUY6Q&tag=duckduckgo-d-20&linkCode=xm2&camp=2025&creative=165953&creativeASIN=B07CWSH3F8

I later used a different method which worked better for me. I charged the cells individually to 3.4 volts, connected them in parallel, let them rest at least 8 hours and then charged them to full with the 3.65 volt charger.

Rick 

mcgivor

Another method to drop the voltage is to get some 12V 20W bulbs, connect them in parallel 5 will be ~ 4A load, more could be added for higher current. The voltages may seem close but it's quite misleading,  55mV difference represents a fair bit of capacity, don't walk away and forget as Rick said, it could result in cell failure the voltage goes too low, again like the charging knee, this will happen very fast if a high load is connected.

The contact person at LWS is Helen Fan, email is, sales5@lws-pcm.com  should you choose to go that route, I have no affiliations with them.

When ordering from Aliexpress or anyone in China, you can request express shipping for additional cost, it's usually quite reasonable.

projectile

Hi Mcgivor and Rick and everyone out there:

I contacted Helen about a bms and she wants to know what is the charge and discharge current of my system.
How would I find that out? is the charge current 28.8v?

I have been reading the articles that were mentioned. But 1/2 of it I still don't get.

Rick I see that you charge your batteries from the middle of the pack. Is there a reason for that?
If I will eventually have to put my 8 cells in parallel I will need more than the 8 bars that I now have.
Where is a good place to get more bars? I did not see just battery bars for sale on Aliexp

Thanks guys

mcgivor

Base the charge and discharge currents on what you expect to encounter in the future, this leaves room to expand. The values are subject to the maximum discharge allowable for the battery, 2C or 200A in your case, although you'll probably not venture there, charging wise same thing, leave room for expansion. Your battery could accept 70A  charge and 130A discharge, not that you would do so on a regular basis but it would leave room to expand, so use these figures, request a different port type such as the LWS-20S 120A-175-RO1 (8S) Different port. The different port allows PV to bypass the battery during times of excess power, to power loads which is a handy feature.

Personally I didn't leave room for expansion but I don't expect to expand, other then capacity, the charging/discharging  will remain the same and exceed my needs.....for now 

Raj174

No, in my opinion, the charger connection location doesn't really matter with a buss bar. Your cells have 61mm centers. I searched, but couldn't find any for your Sinopoly cells. The bars are pretty much specific to the battery manufacturer, and the place where I bought mine does not sell Sinopoly. However, a set specifically for balancing can be easily made out of aluminum bar stock (Home Depot). That's how I made the ones in the photo. Just need, in your case, a piece of aluminum bar stock 48"x1.5"x 3/16" which will be cut in to two 24" bars. Also, a hack saw, a file to clean up the edges and a drill with a 9mm bit (you have 8mm bolts and I recommend a little wiggle room) and a step bit used to take off the sharp edge of the holes. I also recommend lining the cells up, like in the photo, then make a cardboard template directly on the cells so that the hole locations are accurate. The bars can be replicated from the template.
If you don't want to make them yourself, there are companies that will duplicate what you currently have, just search custom buss bars.

Rick  

projectile

Rick 
I asked the people at Ruixu that made my batteries in a chat but they did not reply.
They sold me the batteries originally with 8 bus bars.
I'll use the Homedepo Idea.

Is there an app for this forum?

Raj174

Don't think there's an app. Access by web version for a phone or tablet, but I have not used it.

projectile

maybe an app will come soon.

Helen sent me this because my inverter is 2000/4000 
Does it look like all that you recommended?

mike95490

Raj174 said:

........ However, a set specifically for balancing can be easily made out of aluminum bar stock (Home Depot). That's how I made the ones in the photo. Just need, in your case, a piece of aluminum bar stock 48"x1.5"x 3/16" which will be cut in to two 24" bars. Also, a hack saw, a file to clean up the edges and a drill with a 9mm........

Argggghhhhh  !!!!   aluminum is a terrible material for electrical use.  Steel is better.   Why ?    Aluminum instantly develops an oxide coating when exposed to air, when you cut and drill it.  The oxide is invisible, very tough (sandpaper is made from aluminum oxide), and a good electrical insulator.   If you do use it, you have to get a tube of No-Ox or anti-ox or something from the electrical department for preparing aluminum conductors.   in electrical boxes, aluminum is tin plated to avoid the oxide issue.

 With steel, even with it's higher resistance, you can at least see when it's rusting and easily clean it.

mcgivor

projectile said:

maybe an app will come soon.

Helen sent me this because my inverter is 2000/4000 
Does it look like all that you recommended?

That would be a good choice if 40A maximum charging is all you'll ever need, they match the capacity to your provided specifications.

Raj174

mike95490 said:

Raj174 said:

........ However, a set specifically for balancing can be easily made out of aluminum bar stock (Home Depot). That's how I made the ones in the photo. Just need, in your case, a piece of aluminum bar stock 48"x1.5"x 3/16" which will be cut in to two 24" bars. Also, a hack saw, a file to clean up the edges and a drill with a 9mm........

Argggghhhhh  !!!!   aluminum is a terrible material for electrical use.  Steel is better.   Why ?    Aluminum instantly develops an oxide coating when exposed to air, when you cut and drill it.  The oxide is invisible, very tough (sandpaper is made from aluminum oxide), and a good electrical insulator.   If you do use it, you have to get a tube of No-Ox or anti-ox or something from the electrical department for preparing aluminum conductors.   in electrical boxes, aluminum is tin plated to avoid the oxide issue.

 With steel, even with it's higher resistance, you can at least see when it's rusting and easily clean it.

I understand where you're coming from, however the balancing bars are only used once every 2 to 3 years and the higher conductivity of aluminum is desired in this case. If they are oxidized the next time they are needed, contact points can be sanded clean in minutes.

projectile

hI Mcgivor:

I want to buy a BMS that can expand with me as I get more involved with solar.

I see that your max charge is 70a. the max charge that Helen suggested for me is 40a will that be a problem for me
when I expand battery bank or things I want power in the future?

Is the operating max temp of +65C good enough for the future or should I ask for +85C?

She proposed (4s) different port as opposed to (8s) is that significant?

Thanks

mcgivor

With 8 cells in series you would need a 8 S BMS,a 4s would be for a 12V nominal system, opting for a higher current capacity will leave  the opportunity to expand, it's not the charging/dischargeing current that is is of importance but rather the cell protection from over or under voltage, which would be included in any current format. Yes I have 4× the battery  capacity you have, my inverter is 2.5Kw though I would never expect to use that even being 100% off grid. Choose a nominal current for maximum charging  then a maximum discharge current and foward the information, the LWS- 20S 120A--175-RO1 (8S ) Dual port,  has served my needs, you have to consider the vendor can only determine your particular needs based on information provided so saying 4000W maximum would prompt them into thinking that is the normal maximum expected, even though it may never happen. Being in your situation the aforementioned model. number would probably be applicable to your system, allowing some room for expansion 
.

projectile

120A-120A was a typo? in the model number

mcgivor

projectile said:

120A-120A was a typo? in the model number

Indeed, should be LWS- 20S 120A--175-RO1 (8S ) Dual port, 
Just to clarify my previous comment, about the charge/discharge currents of the BMS not being of importance, the rationale behind this is related to your particular arrangement and this particular BMS.
You wouldn't want  charge/discharge thresholds that exceed the batteries capabilities, such as a 500A value for both with 100Ah cells, for example. 

projectile

Mcgivor:

They want me to buy 2 bms for $93 each.

Do you recommend getting two bms?

These are the latest specs of the bms are they still good?

Thanks

mcgivor

Their minimum order quantity is 10 units on Alibaba, they sold me a single as a sample, perhaps policies have changed who knows, perhaps you could find someone who needs one, offer it for sale, or save it as a spare for when you build another battery. The price is based on bulk order so very good value. That's the same one I have, the nice feature is the large screw terminals, unlike many others which require soldering wires onto the board.

projectile

Alie has shipped my charger and she will send one unit.

Can't wait

About to build the extra bus bars for when I need to put the cells in parallel.

mcgivor

Good to hear, the most important thing is patience, you could prepare by dischargeing to equal cell voltage, before parallel connection, then the long slow ballancing when the charger arrives, it's worth doing right the first time. Don't be overly concerned with controller settings for now, that is for the next chapter, when the BMS is connected.