About a year ago I got rid of my lead acids and switch over to Pylontechs. I placed 3 x US3000 in parallel, with a Raspi and ICC software monitoring the whole lot. All went well. Recently I added another pylontech ot the mix. I hooked up the new pylontech and allowed the four batteries to reach equilibrium, so to speak, before connecting back to the inverter. Now I expected the older ones to discharge first, but it appears to be happening the other way around. The new pylontech is the master. See the screenshot from my ICC while the batteries are charging, the new one is way lower than the other 3, and is drawing less current.

For the same current draw I would understand the new one being lower during charge, as it's capacity will be higher and thus needs more current to fill up. But why would there be such a great difference in SOC, and why would the new one charge with less current than the rest? And, why would it discharge before the rest?

I've even seen the ICC software report a SOC of 101%! (In the pic, the blue circled number on the left is the total SOC).

Could this be due to a firmware difference between the old and new ones? I'm not even sure if these batteries' firmware can be updated? Any input would be appreciated!

 

Edited June 18, 20205 yr by OomD

Have you done a full charge since adding the new battery? if not, the the SOC is probably just incorrect. I would do a full charge to 53.2V and you should see the SOC jump to 100% at some point. Then see what happens during the next few cycles.

1 hour ago, OomD said:

I expected the older ones to discharge first

I would actually expect the new one to discharge first.

When placed in parallel batteries always contribute discharge current proportional to their capacities. New battery will have the highest capacity and will take the brunt of it. The difference with LiFePO4 is that it isn't as detrimental (on recharge) as it would be for lead acid.

Just now, plonkster said:

I would actually expect the new one to discharge first.

With that said though, if you're talking about the LED-based SOC indicator, new batteries always take a while to settle, and while they do their SOC tends to jump to and from 100% because of mild imbalanced between cells. So best is to monitor it daily, chances are in about two weeks' time it will all normalise.

To my understanding this is nothing to worry about - it is just the new battery getting settled

I also recently added another Pylon to my system and am seeing exactly the same as you. On some days the new battery is closer to the older ones, one other days the difference is a bit higher. I believe over time they will all converge (as my other 2 also did)

1 hour ago, OomD said:

I've even seen the ICC software report a SOC of 101%!

Same thing also here. Again, as far as I understand nothing to worry about

1 hour ago, Stanley said:

Have you done a full charge since adding the new battery? if not, the the SOC is probably just incorrect. I would do a full charge to 53.2V and you should see the SOC jump to 100% at some point. Then see what happens during the next few cycles.

Yep, 6 full cycles since I've added the new battery, as can be seen on the screenshot.

 

48 minutes ago, plonkster said:

I would actually expect the new one to discharge first.

When placed in parallel batteries always contribute discharge current proportional to their capacities. New battery will have the highest capacity and will take the brunt of it. The difference with LiFePO4 is that it isn't as detrimental (on recharge) as it would be for lead acid.

Strictly speaking, if stronger batteries give more current then the SOC should remain the same for all. But things are obviously not always in proportion, I understand. What baffles me most is how come the stronger battery draws less current during charging? I would expect the "flattest" battery to draw the most current. But, this is with "dumb" batteries in parallel, perhaps the built-in battery manager in these are the cause of it. Some fancy algorithm they use to distribute the charging amongst all the batteries? I dunno, just thinking out loud here.

Thanks guys, appreciate the feedback. I'll keep an eye on it over the next few weeks.

Hi OomD

Did the batteries tend to equalize eventually? If it did how long did it take?

 I am experiencing the same issue after adding a battery to my system.

Regards Vijen

Is your new battery a type c pylontech

If so the bms cable in the box is wrong

Goodwe Flyer.pdf Note US2000C&US3000C- Dip Switch & Cable Pins.pdf

Edited August 5, 20214 yr by paul99

Yes, It is a UP5000C. I have however read the documents you attached and I do not believe that is my problem. I use ICC with communicates with battery via the console port and the correct type C cable is used. I think that the issue is caused because of the difference in SOC when I installed the battery. It appears it should self correct after a few 100% charges, or at least I hope it does.

I have taken note of the voltage settings tho and made sure that I do not go over 52.5V.

Hi Paull99,

I upgraded my system by adding two Pylontech US2000C batteries to my existing 4X US2000B batteries (Goodwe ES 4.6kW inverter). They are connected as follow: 

A1	2000C (Master)	B1	2000B
A2	2000C	B2	2000B
A3	2000B	B3	2000B

All batteries connected in parallel and group A and B connected in parallel on a busbar at the DC Breaker.

Before adding the two C’s, the BMS and CT Meter worked fine. However, after the upgrade the PV Master reports a CT and BMS communication failure. As per the Goodwe Flyer, I disconnected Pin 2 and then only connected pins 4&5, but this problem persist.

Any ideas?

Thank you