LFP not charging with solar

[ForeverDes]

My new 560 AH LFP bank is not accepting any solar charge.
My fridge draws about 5 amps (as shown on the capacity monitor at night as net charge/draw) When it isn't running, my mppt controller shows 0 amps output and the capacity monitor shows 0 amp net. When it runs my mppt shows 5 amps output and the capacity monitor still shows 0 amps net.
I switched my solar the the FLA starting battery, and the mppt immediately shows 11-12 amps (it was pretty overcast, so that tracks with last years performance)

What could cause the LFP to not accept charge? I assume the immediate suspects are the BMS and the capacity monitor shunt. What else could I be missing?
My boats on a mooring ball now, so 120v charging sources are more difficult, although I could bring a generator to test something if needed.

I could also go ahead and install a dc-to-dc charger, but I'm worried the LFP won't accept charge from that either, unless I identify and correct the issue first.

Any thoughts or suggestions on what to check?

Additional info:

Battery negatives go through bms, then to the capacity monitor shunt, then to a (-)4 lug bus bar.
Battery positives go to 500 amp ANL fuse, then to (+)4 lug bus bar.
Solar (mppt) negatives and positives go to bus bars. Bus bars then feed fuse panels (+) and common negative for loads.
Mppt set for 13.6v charge

[smac999]

Sounds like the battery is full if the controller is outputing the 5a fridge current but nothing extra to battery.

Or the solar voltage is to low the battery does not accept anymore at that voltage. It should probably be bulking at higher then 13.6.

What is your Soc when this is happening ?

[ForeverDes]

According to the battery monitor, the SoC is about 20% (110 of 560 AH)
I thought about raising the charging voltage to see what happened. I may give that a try. I think at full SoC I was slightly higher than 13.6v. I will have to check my notes to verify that though.

[Flod]

Maybe a voltage drop from where you feed the incoming solar and to the battery? Have you a long run between?

[ForeverDes]

Originally Posted by Flod

Maybe a voltage drop from where you feed the incoming solar and to the battery? Have you a long run between?

I have 6 AWG wire running about 11 feet from the panels to mppt and 4 feet from mppt to battery. 380 watts if solar at about 22v, so It *shouldn't* be an voltage drop issue. However, checking voltage at the bus bars is an easy step to verify, I'll do that next time I'm at the boat. If it's higher than 13.6v I can increase my mppt output, and if it's lower I can eliminate a potential issue.

[Flod]

As lifepo4 have a very flat voltage curve it could be that you have 13,6 v out of the mppt but that you loose 0.2-0.4 in the cable. Then you will have maybe 13.2v at the battery. This might not be enough.
The other thing I was thinking about was if you have a charge relay? It could be closed by the BMS

[hzcruiser]

Originally Posted by ForeverDes

My new 560 AH LFP bank is not accepting any solar charge.
My fridge draws about 5 amps (as shown on the capacity monitor at night as net charge/draw) [...]
My boats on a mooring ball now, so 120v charging sources are more difficult, although I could bring a generator to test something if needed.
[...]
Mppt set for 13.6v charge

All that power on a <30foot boat? Sounds like a lot to me.

[ttex]

Charger isn't set high enough. Needs to be set closer to 14.2. 14.6 is generally full charge. I only take mine up to 14.25.

[Oceanride007]

Your Negative for starting shouldn't be connected to BMV anyway, maybe they connected the wrong wire. ie Your negative is not connected to the Battery Monitor.

[ForeverDes]

Originally Posted by hzcruiser

All that power on a <30foot boat? Sounds like a lot to me.

It was only supposed to be 280ah, but I was sent 8 cells instead of 4, and had room for them all, so I decided to use them.

Originally Posted by ttex

Charger isn't set high enough. Needs to be set closer to 14.2. 14.6 is generally full charge. I only take mine up to 14.25.

I think you're probably right. My notes says I charged all the cells to 3.65 volts each, so that's 14.6 total. (Iirc it was more like 14.55 when I connected all the cells and checked).
I honestly don't know why I didn't think of this, but right now it's the most likely culprit. Thankfully changing the charging profile for the mppt is easy.

Originally Posted by Oceanride007

Your Negative for starting shouldn't be connected to BMV anyway, maybe they connected the wrong wire. ie Your negative is not connected to the Battery Monitor.

The negative for the start battery isn't connected to the monitor. Only the house bank is, and only through the negative shunt.

[T1 Terry]

Unless you have a good quality BMS unit that measures cell voltage and stops the charging if a cell hits 3.6v, I'd be inclined to limit the charging voltage to 14v bulk and 13.8v float and a max of 15 mins absorption time .... while watching the cell voltages like a hawk.
If the battery pack has not been fully charged a number of times, they will be a long way out of balance and no balancer will be good enough to get them back into balance without the BMS stopping the charging when a cell hits 3.6v.
Over voltage in ant LFP cell is one of the quickest ways to kill it, the quickest way is to pull it below 0V while in a pack, that is virtually instant death, we are talking seconds not mins or hrs ......

T1 Terry

[ForeverDes]

Originally Posted by T1 Terry

Unless you have a good quality BMS unit that measures cell voltage and stops the charging if a cell hits 3.6v, I'd be inclined to limit the charging voltage to 14v bulk and 13.8v float and a max of 15 mins absorption time .... while watching the cell voltages like a hawk.
If the battery pack has not been fully charged a number of times, they will be a long way out of balance and no balancer will be good enough to get them back into balance without the BMS stopping the charging when a cell hits 3.6v.
Over voltage in ant LFP cell is one of the quickest ways to kill it, the quickest way is to pull it below 0V while in a pack, that is virtually instant death, we are talking seconds not mins or hrs ......

T1 Terry

I have Daly 250 amp bms on each set of 4 cells. I don't know enough about bms but they are supposed to balance cells automatically. I didn't check the cutoff voltage on each cell, but I did charge each cell to 13.65v and had less than .04v spread after 24 hours, and then I did a few charge/discharge cycles after hooking up the bms and rechecked with similar results

[T1 Terry]

Originally Posted by ForeverDes

I have Daly 250 amp bms on each set of 4 cells. I don't know enough about bms but they are supposed to balance cells automatically. I didn't check the cutoff voltage on each cell, but I did charge each cell to 13.65v and had less than .04v spread after 24 hours, and then I did a few charge/discharge cycles after hooking up the bms and rechecked with similar results

Sorry if this comes across a bit harsh, but unless you get on top of understanding lithium batteries are nothing like lead acid batteries, your life is going to be a whole hell hole of confussion.
I'm guessing you mean 4 cell battery not each single cell. 13.65/4= 3.4125v. No mention of the differential between highest and lowest cell when the 13.65v cut off was reached so not really of much value I'm afraid.
The end of charge cell voltage in each and every cell must be greater than 3.5v and after the rest period still be greater than 3.45v to determine the cell as fully charged .... any voltage lower than that is "not fully charged" and has no other reference value.
LFP and LYP are not like lead acid cells where a volt less than fully charged means something like 98% charged or some similar number. The only meaningful numbers are greater than 3.45v rested means 100% charged and 2.8v rested means less than 0% capacity .... more than 100Ah has been draw out of the 100Ah cell, not a clever move if you want the long cycle life you are expecting for the big $$ you have just parted with ......... If this doesn't make sense then you have failed the first part of understanding lithium batteries and that is, forget all you knew about lead acid batteries because it is meaningless when it comes to lithium batteries. Very hard to do, I know, but unless you start out from scratch and forget all you knew about batteries and accept a whole new set of rules for lithium batteries, you are going to have no end of problems that you can't seem to solve.

Step 1, get the battery to hold greater than 3.45v in every cell after a 12 hr rest, the battery is now fully charged to 100% and you can start to make calculations from there. Any cell voltage lower than 3.45v after a 12 hr rest is not fully charged so needs more charging till it does rest at better than 3.45v.

Step 2, The differential between the highest and lowest cell at any voltage less than 3.45v or greater than 2.8v is not the true difference between the state of charge in each cell. The discharge curve is virtually flat, the only thing that puts any sort of curve in it is when charging or discharging. This means two cell voltages that are close to the safe does not mean the state of charge is similar in those two cells if the voltage is inside the upper and lower voltages I just mentioned .... very important that this is fully understood.

Not difficult to understand once you let all the other battery knowledge you had get filed away under "lead acid, not relevant" and store a whole new lot of knowledge filed under "LFP/LYP chemistry lithium batteries", This one can be tricky, only write any new information in this file in pencil until it is confirmed, then you can rub out the mis-information that is riff across the interweb.

T1 Terry

[ForeverDes]

Originally Posted by T1 Terry

Sorry if this comes across a bit harsh, but unless you get on top of understanding lithium batteries are nothing like lead acid batteries, your life is going to be a whole hell hole of confussion.
I'm guessing you mean 4 cell battery not each single cell. 13.65/4= 3.4125v. No mention of the differential between highest and lowest cell when the 13.65v cut off was reached so not really of much value I'm afraid.
The end of charge cell voltage in each and every cell must be greater than 3.5v and after the rest period still be greater than 3.45v to determine the cell as fully charged .... any voltage lower than that is "not fully charged" and has no other reference value.
LFP and LYP are not like lead acid cells where a volt less than fully charged means something like 98% charged or some similar number. The only meaningful numbers are greater than 3.45v rested means 100% charged and 2.8v rested means less than 0% capacity .... more than 100Ah has been draw out of the 100Ah cell, not a clever move if you want the long cycle life you are expecting for the big $$ you have just parted with ......... If this doesn't make sense then you have failed the first part of understanding lithium batteries and that is, forget all you knew about lead acid batteries because it is meaningless when it comes to lithium batteries. Very hard to do, I know, but unless you start out from scratch and forget all you knew about batteries and accept a whole new set of rules for lithium batteries, you are going to have no end of problems that you can't seem to solve.

Step 1, get the battery to hold greater than 3.45v in every cell after a 12 hr rest, the battery is now fully charged to 100% and you can start to make calculations from there. Any cell voltage lower than 3.45v after a 12 hr rest is not fully charged so needs more charging till it does rest at better than 3.45v.

Step 2, The differential between the highest and lowest cell at any voltage less than 3.45v or greater than 2.8v is not the true difference between the state of charge in each cell. The discharge curve is virtually flat, the only thing that puts any sort of curve in it is when charging or discharging. This means two cell voltages that are close to the safe does not mean the state of charge is similar in those two cells if the voltage is inside the upper and lower voltages I just mentioned .... very important that this is fully understood.

Not difficult to understand once you let all the other battery knowledge you had get filed away under "lead acid, not relevant" and store a whole new lot of knowledge filed under "LFP/LYP chemistry lithium batteries", This one can be tricky, only write any new information in this file in pencil until it is confirmed, then you can rub out the mis-information that is riff across the interweb.

T1 Terry

Sorry Terry, harshness aside, your post has pretty well zero useful information for me. There was a typo in my post, but you're dead wrong in your assumption, so let me correct it here:

I did not charge 4 cells in series to 13.65v. I actually put 4 cells in parallel and charged them to 3.65v.

I wasn't planning in answering you a second time at all, since responding to you the first time worked out so poorly, but for the sake of anyone else reading and wondering, not to mention a chance to keep this thread alive, I thought a correction was in order.
As a personal note, you may find, when something doesn't make sense, that asking for clarification is better than making assumptions. I would have happily acknowledged and corrected my error sooner, if responding to you didn't make me feel so much like I'm feeding a troll.

[T1 Terry]

Originally Posted by ForeverDes

Sorry Terry, harshness aside, your post has pretty well zero useful information for me. There was a typo in my post, but you're dead wrong in your assumption, so let me correct it here:

I did not charge 4 cells in series to 13.65v. I actually put 4 cells in parallel and charged them to 3.65v.

I wasn't planning in answering you a second time at all, since responding to you the first time worked out so poorly, but for the sake of anyone else reading and wondering, not to mention a chance to keep this thread alive, I thought a correction was in order.
As a personal note, you may find, when something doesn't make sense, that asking for clarification is better than making assumptions. I would have happily acknowledged and corrected my error sooner, if responding to you didn't make me feel so much like I'm feeding a troll.

Ouch ..... Please accept my apology for try to offer assistance, even if it wasn't wanted, I'll try to mend the errors of my ways in future

I guess we will soon enough find out if you speak for all who read these forum threads, if that is the case and others would prefer I didn't post, then please say so and I will stop adding "troll" posts

T1 Terry