Your Charge Controller "Charges" the line between your Battery.

Michael77 said:

Hi, Thank you. I now see that almost everyone is saying the same thing, that I shouldn't use my BMS to stop the charge cycle.

For 2 years I used a simple non programmable PWM Charger to charge My LFP Battery and the only way the charge cycle would stop is when the Battery's BMS would stop the charge cycle.

With my new, programmable MPPT Charge Controller - even at default settings, or even in the User settings, there is no way to stop the charger from sending energy to the battery and for the first week I owned it and had it in the LFP preset mode, the only way the battery stopped charging is when the Battery's BMS stopped the charge cycle

How do you stop the charge cycle on your Lithium Iron Phosphate Battery?

Click to expand...

What I did is program my Renogy Rover in the user setting. I set moderate values because I don't want to overcharge my LiFePo batteries with the default lithium settings. I used the Renogy BT app.

Texas-Mark said:

Yes. Set your charge controller to the proper settings after you get the cables fixed.

Click to expand...

Hi, thanks, again, and I don't mean to be a pain, but there is no setting to stop the current from flowing from the charge controller to the battery.

Also, can I kindly ask, how do you stop your charging cycle on your system?

Risky Rob said:

What I did is program my Renogy Rover in the user setting. I set moderate values because I don't want to overcharge my LiFePo batteries with the default lithium settings. I used the Renony BT app.

Click to expand...

Do you every charge to full. How do you actually stop the charging cycle?

sunshine_eggo said:

I would no longer use either the BMS or the charge controller for voltage values only the BMS for current. I would check the battery terminals and the charger terminals with a voltmeter. You have no idea if either of those are accurate, and even if your voltmeter is inaccurate, it should be relatively accurate such that the difference between the two values is correct.

NOT here:
View attachment 108786

But ON the battery terminals.

and here:

View attachment 108788


And given that those are puny little Phillips that already look partially boogered up, I would looking at this connection very closely.

Click to expand...

Thank you.

Ahh, yes thank you. That is my old PWM charger that I swapped out - I used it for 2 Years and it works great. I still keep it as a backup.

It seems that everyone is saying pretty much the same thing, so as I have already stated, I will be swapping out the wires from 8AWG to 6 AWG. And triple checking all the connections, etc.

Once I pull the counter off the kitchenet and have better access to the system I will do a lot more testing and monitoring, and I will make sure to check the voltages at the terminals like you suggest, for both the charger and the battery

Among many of the concerns people are having is the 1 volt delta between the charger and battery and I appreciate your assistance and theoretical mathematical analysis of the system, though I have to admit, I don't remember a lot of my advanced math... Though I do fully understand the underlying theories and equations. And I do agree with you that there technically is something wrong, especially based on the very solid foundations of the theoretical models you have provided. (But there is a possibility that there is a hidden variable, or factor that is not in the equation... though I think you are very smart and thorough, and I really don't have any idea of what that could be, other then to guestimate and say that the Battery is a "Black Hole" and it is able to absorb energy faster then the current can actually travel through the wires... - I know... laugh right now - hahaha black hole, welling up, etc etc - how can you compare electricity with a garden hose or fluid dynamics - NO ONE uses water through a hose to explain electricity, and any such use of the thickness of a garden hose, or the well that is supplying it to try and explain electricity is ridiculous! lol)

Once I change out the wire I will definitely report back, if this help or fixed the issue, and if not, I'll be willing to looking at other options and reasons, but, as it is right now, my system is running great, the new MPPT with my aggressive settings and the 2 additional solar panel (=6x100w) are giving me more energy then I have every been able to produce and I am using the system to cook with about 750/900 watts for about 4 hours every day!

"As we move into the cooler Fall months, I will continue to monitor and use the system daily, cooking, and even seeing if I can cook and run a small 12v 300 watt heater, and have enough juice. I will monitor the system and I will report back on the progress. I have confidence in my Batteries, and though I may be "shaving years off of them" by using aggressive charging parameters, I am more than sure they will hold up just fine for a very long time, and if not, its not a big deal, they are the cheapest Chinese Packs I could get from China. They could fail for any reason at any moment, and if they die, they die. Based on the safety data on these batteries, there is more of a chance that any other component will fail before the battery cells themselves fail, and if that happens I will tear them apart and harvest them."

Thank you for all your great help and advice. Thanks.

Every manufacturer seems to use different wording. Post your charge controller, or ideally, screenshots of the available settings.

Michael77 said:

Do you every charge to full. How do you actually stop the charging cycle?

Click to expand...

My controller stops charging at about 90%, based on the settings. You could set it for 100%.

Texas-Mark said:

I just noticed that he is measuring on a lug that is not even connected to the battery. Why?????

Click to expand...

Hi, thank you for all your help and advice on my system, I appreciate the extra eyes on it so I have confidence I haven't missed anything. Your help is greatly appreciated.

Hi, yes, I did make that clear several times to other people, but those are the wires that connect to the the 250A Busbar that connect the Charge Controller with 8 AWG cable (I will be swapping out to 6AWG) - Connecting to the Battery with 2' 2AWG cable and 2AWG cable to the inverter. Those are an extra 6 AWG cables for adding a second battery in parallel.

Thanks again. I will definitely report back once I swap out the charge controller wire with bigger cable and I will have a lot more room to tear the system apart and get better pictures and information. Right now everything is in a cabinet under the kitchenet and I would have to tear the whole thing apart really at it

Thank you again for all your assistance, thanks

Risky Rob said:

My controller stops charging at about 90%, based on the settings. You could set it for 100%.

Click to expand...

What charge controller are you using, and can you show me the settings you use. Do you have a custom BMS profile for your LFP Batteries?

Texas-Mark said:
I just noticed that he is measuring on a lug that is not even connected to the battery. Why?????

400bird said:

How did I not see that either?

Click to expand...

Hi, i don't know how to double reply so here is my reply to Tex

"Hi, thank you for all your help and advice on my system, I appreciate the extra eyes on it so I have confidence I haven't missed anything. Your help is greatly appreciated.

Hi, yes, I did make that clear several times to other people, but those are the wires that connect to the the 250A Busbar that connect the Charge Controller with 8 AWG cable (I will be swapping out to 6AWG) - Connecting to the Battery with 2' 2AWG cable and 2AWG cable to the inverter. Those are an extra 6 AWG cables for adding a second battery in parallel.

Thanks again. I will definitely report back once I swap out the charge controller wire with bigger cable and I will have a lot more room to tear the system apart and get better pictures and information. Right now everything is in a cabinet under the kitchenet and I would have to tear the whole thing apart really at it

Thank you again for all your assistance, thanks"

And thank you again, I will look at all the new round of questions and get back to you on those. I really appreciate all the great information and advice.

Risky Rob said:

What I did is program my Renogy Rover in the user setting. I set moderate values because I don't want to overcharge my LiFePo batteries with the default lithium settings. I used the Renogy BT app.

Click to expand...

Hi, thank you for all your great help and the great information. It sounds like your Renogy Rover has some type of cut off voltage and stops charging once your batteries are charged up to a set voltage.

My MPPT does not have any type of cut off voltage in the "USE" (User) Parameter settings. I am sure if I use the AGM, or some other Lead Acid Battery Preset it would cut of the voltage at a designated value, but in the user programmable settings area, AND with the Lithium Iron Phosphate Preset, it does not stop current until my BMS turns of charging.

I was going to buy a Renogy Rover a couple years ago, but they were very expensive back then, and just recently picked up a new model 2022 MPPT for $125 - maybe it was so cheap because they don't have any way to manually stop the charge cycle if you are not using one of the lead acid presets.

Also, do you have a programmable BMS, and what do you set it to? Edit: And Thank You

Wow. Just found this thread. Very entertaining, if a bit scary.

Dunning Kruger effect, perhaps the best I've seen.

But it's good to see that the regulars here got the poor fellow back on the right track.

time2roll said:

A full volt between that short connection is too much. Verify the issue with a voltmeter. Then fix it.
Although I wonder if the controller is displaying the set point rather than the actual output voltage.

Click to expand...

Hi, thanks, pretty much everyone is saying the same thing as you and, I guess a 1 volt delta from the charge controller to the battery is an issue, and is definitely questionable. max amps through the 3 foot 8 gauge AWG thin strand silicon wire is 33 amps, while the charge controller is max 40 amps.

The wire is within spec and should be able to handle it, and I did report to many other people that the wire IS getting hot. I have already decided to replace it with 6AWG cable. I am all about efficiency and peace of mind.

The voltages from the controller, BMS and my multimeter are all perfectly matching when I take manual readings or at night when there is no energy coming in from the solar panels to the charge controller...

Thanks for pointing these things out, and I will definitely keep the community updated on the system, when I swap out the wire, and the overall progress I am having.

Michael77 said:

Hi, thank you for all your great help and the great information. It sounds like your Renogy Rover has some type of cut off voltage and stops charging once your batteries are charged up to a set voltage.

My MPPT does not have any type of cut off voltage in the "USE" (User) Parameter settings. I am sure if I use the AGM, or some other Lead Acid Battery Preset it would cut of the voltage at a designated value, but in the user programmable settings area, AND with the Lithium Iron Phosphate Preset, it does not stop current until my BMS turns of charging.

I was going to buy a Renogy Rover a couple years ago, but they were very expensive back then, and just recently picked up a new model 2022 MPPT for $125 - maybe it was so cheap because they don't have any way to manually stop the charge cycle if you are not using one of the lead acid presets.

Also, do you have a programmable BMS, and what do you set it to?

Click to expand...

No, my LiPo battery bms isn't accessible. I can't read it or program it. I guess you need to stick with the default lithium setting on your SCC.

Horsefly said:

Wow. Just found this thread. Very entertaining, if a bit scary.

Dunning Kruger effect, perhaps the best I've seen.

But it's good to see that the regulars here got the poor fellow back on the right track.

Click to expand...

Gonna google that right now... : - )

Could be the wire, could be a hidden variable, either way, as I have told all the ppl in this community; thanks for the help, and I will swap the wire, double/triple check all the connections and keep people updated. Thanks again!

Risky Rob said:

No, my LiPo battery bms isn't accessible. I can't read it or program it. I guess you need to stick with the default lithium setting on your SCC.

Click to expand...

I have a Bluetooth App that tells me my BMS values on one of my 2 batteries. Even with the default "LI" preset the only way my battery stops charging is when the BMS shuts off the charging, I can see the BMS Flip off charging, and I can not "turn on charging" until the voltage drops below the set "Charge Voltage Reconnect Voltage" or something like that..

So, yea, even in the preset mode for LI, my BMS is the only way my batteries stop charging.

What did you program your charge controller to stop at?

Supervstech said:

And the BMS last line of defense is on the cell level, not the entire battery level. So, the BMS main and most important job is to detect cell imbalance to prevent pack failure… not to control the pack voltages.

Click to expand...

Hi, thank you for all your help.

Everyone in here is saying I should not use my BMS to stop the charge cycle.

I had a PWM Charge Controller that was not programmable and I used it for 2 years. I still have it and it works great. The only way by battery would stop charging is once the BMS on the battery hit the charge cutoff voltage and stopped the charging cycle. This is the same with both of my LFP batteries

My new MPPT Controller that I can program has no way of manually stopping the charge voltage, and even with the Lithium Iron Phosphate preset ("LI") - the BMS turned off the charging once the battery was full.

I appreciate your help and information; how do you stop your Lithium Iron Phosphate Battery from charging, what charger do you use, what cutoff voltage is it set to? do you have a BMS and what is your settings?

Thanks for your help! Such a great helpful community in here.

Michael77 said:

Hi, Thank you, you have been really helpful. I really appreciate your advice. I am running the 40Amp MPPT Charge Controller through a 3 Foot, 8 Gauge AWG Thin Strand Silicon Cable with a T90 Connector to the 250 Amp 4 3/8" Stud Busbar, and that connects to the Battery with a 2AWG 2 foot Cable, and a 2AWG Cable to the 2200W Pure Sine Inverter. (Will be upgrading the 8AWG cable to a 6AWG Cable, as I already said & double check all wires, connections, etc.)
.

Click to expand...

Aha! I think I found an issue in the install…
Can you post a picture of the bussbar you are using?

There is a 4 post bussbar listed for 250A, that is made of BRASS… and it will drop your voltage all by itself.

Michael77 said:

The voltages from the controller, BMS and my multimeter are all perfectly matching when I take manual readings or at night when there is no energy coming in from the solar panels to the charge controller...

Click to expand...

I find it very odd that the multimeter would read so much different than the controller display. Or the BMS display. Maybe something is just out of calibration. If the controller needs to be set at 15.2 volts to actually get 14.2 volts then it is a functional issue maybe covered under warranty.

I mean if the voltmeter matches the BMS and then directly on the controller terminals is a full volt lower than the controller display there is an issue with what is displayed on the controller. All this talk might just indicate a calibration issue of the controller and everything is actually fine.

If replacing wire, #6 will be better. I would end up with the max that fits in the terminals.

Browneye said:

It is generally accepted that your charging termination parameters are set at the charger level so that the BMS does not need to get involved. Using the BMS to do this is considered bad practice. The BMS shut down of current in or out of a lifepo4 bank is considered emergency use or application.

The battery voltage displayed on the SCC is with the charge current added on top of the system or battery voltage level. It is common for it to read a little higher at the SCC. Again, the only way to get a true volts reading on a battery is after resting with no load or charge current. At that point, your SCC and battery should pretty well read the same. With charging current it is going to read higher at both the SCC as well as the actual battery, and any meters you employ. At least that has been my experience.

Same for loading a system - an inverter will show a slightly lower battery voltage that the actual battery - but the battery also reads lower than at rest, called load sag.

Once your system is built and you are monitoring loads and charging, and what everything displays, you'll have a lot better feel for how your system is performing.

Click to expand...

Hi, thank you again for all your help with this. There are a lot of people that have been stating that the BMS should not be used to stop the charge cycle.

How do you stop the charge cycle on your set up?

For 2 years I used a non programmable PWM charger that did not stop charging until the BMS stopped the charge cycle, and it worked excellent. I have now switched to an MPPT and there are presets for Lead Acid, Li for Lithium Iron Phosphate, and USE for user parameters.

I tried the LI setting for a week and I know that the only way the charge cycle was interrupted is when my BMS stopped the charge cycle.

I also used the USE, user definable parameters settings and there is no way to stop the charge cycle or set a cut off voltage, and the only way for the battery to stop charging is for the BMS to stop the charging.

Am I missing something, can you please help me with this, everyone is saying the same thing, but I really don't have any way to not use the BMS - and insight or advice would be greatly appreciated.

And again, thank you for all your help. And such a great community and forum.

Supervstech said:

Aha! I think I found an issue in the install…
Can you post a picture of the bussbar you are using?

There is a 4 post bussbar listed for 250A, that is made of BRASS… and it will drop your voltage all by itself.

Click to expand...

Are you talking about that video that DPoz made? He said the same thing and YES, I have those exact 40$ "cheap" but way overpriced IMO busbars! They should be able to handle 33/40 amps though... right? They are rated for 250 amps and nothing else was on when I did these tests... - thanks for your help on this. And what a really great helpful community!

Michael77 said:

Are you talking about that video that DPoz made? He said the same thing and YES, I have those exact 40$ "cheap" but way overpriced IMO busbars! They should be able to handle 33/40 amps though... right? They are rated for 250 amps and nothing else was on when I did these tests... - thanks for your help on this. And what a really great helpful community!

Click to expand...

Yup, thems the ones…
You have brass bussbars, and a weak conductor, and crimp connections, and likely non flat lug connections with oxidation… it all adds up. Try testing voltage at the bussbar, at the battery terminals, and at the charge controller… see where the voltage drops.

time2roll said:

I find it very odd that the multimeter would read so much different than the controller display. Or the BMS display. Maybe something is just out of calibration. If the controller needs to be set at 15.2 volts to actually get 14.2 volts then it is a functional issue maybe covered under warranty.

I mean if the voltmeter matches the BMS and then directly on the controller terminals is a full volt lower than the controller display there is an issue with what is displayed on the controller. All this talk might just indicate a calibration issue of the controller and everything is actually fine.

If replacing wire, #6 will be better. I would end up with the max that fits in the terminals.

Click to expand...

Hi, yea, thanks for your help on this. The multimeter is accurate, even more accurate then I thought it would be - it was only like 20$, but yea, triple checking all the voltages, the BMS, Controller and Multimeter all read the same values when compared against eachother and together...

As everyone is pointing out, a 1 volt delta from the charge controller to the battery is very odd, if not, as at least one other has said totally FUBR! lol...

I am pretty sure I will be able to get a #6 cable in there, if not I will trim the end every so slightly so that it fits, and that way the bulk of the cable will be "large enough/larger then necessary..."

I think my battery is a Black Hole and the event horizon is somewhere on the line, and it is absorbing more energy then can actually flow through the lines... - while I jokingly use astronomical depictions of this occurrence, I think you understand the theoretical concept...

Thanks for the help and such a great community helping me make sure my system is tits! tippy top tits... okay, now its getting late! haha thanks again!

Michael77 said:

I have a Bluetooth App that tells me my BMS values on one of my 2 batteries. Even with the default "LI" preset the only way my battery stops charging is when the BMS shuts off the charging, I can see the BMS Flip off charging, and I can not "turn on charging" until the voltage drops below the set "Charge Voltage Reconnect Voltage" or something like that..

So, yea, even in the preset mode for LI, my BMS is the only way my batteries stop charging.

What did you program your charge controller to stop at?

Click to expand...

High Voltage Disconnect 14.5v
Charge Limit Voltage14.1v
Equalization Charge Voltage 14.0v
Boost Charge Voltage 14.0v
Float Charge Volt 13.6v
Boost Char Return Volt 13.3v
Over Disc Return Volt 11.0v

I don't discharge the LiFePo bank daily, so these are mild settings meant to not stress the battery. I've read that high charge can be as bad for the LiFePO4 as low charge.

Texas-Mark said:

I just noticed that he is measuring on a lug that is not even connected to the battery. Why?????

Click to expand...

There are two threads from the same OP going on at the same, I did ask about that on my post #25 but did not see the answer.

Supervstech said:

Yup, thems the ones…
You have brass bussbars, and a weak conductor, and crimp connections, and likely non flat lug connections with oxidation… it all adds up. Try testing voltage at the bussbar, at the battery terminals, and at the charge controller… see where the voltage drops.

Click to expand...

Yea man, the thought flashed through my mind when I saw him file away the corner on that video!

Totally agree, you literally read the back of my mind. When I get the 6 Gauge wire I will tear the whole thing apart and connect directly to the battery - for testing purposes and see WTF is up.

Spot on! Thanks