Battery voltage high, but SoC low?!?

[miahallen]

I recently setup a new off-grid system designed around the Outback FP-1 system with a MATE 3 system controller.
A few weeks ago, the MATE 3 encountered a known bug and went into a boot loop...so it has been out of the picture for some time. But the rest of the system seemed to be functioning normally. Until two days ago, when the power went out 4 times, once first thing int he morning (battery level showed below 50%, and then three more times that night. Each time the power went out I reset the system, but that evening...it was quite obvious the batteries were dead. The next day I ran the generator all day to restore the batteries and I figured it was simply due to low solar exposure due to a few rainy days. The weird part was that after resetting the system, the battery level indicator showed the batteries were full again, which seemed was quite obviously incorrect.

Yesterday, I replaced the MATE 3 system controller to get more detailed information on the system and we also we had pretty good sun yesterday and today. But I noticed at the end of the day today, the battery SoC was showing and error again, and the MATE 3 is indicating a battery level of 34%...HOWEVER, the battery voltage is reported as 58V and I confirmed that with my MM. The batteries are 8x Trojan L16P-AC 6V 428Ah. All components are about 3 months old. I checked the water level in the batteries and it is good.

I'm still learning a lot about this stuff...but it seems to me that the voltage level I am observing, indicates a higher SoC that what the MATE 3 is reporting...is that a possibility? My float setting is at 52.8V, so it seems that the batteries are never going into MPPT Bulk charging, because the voltage level is too high...why is this happening?

TIA

[Sunking]

Well first thing is forget anything any of your meters or gizmos are telling because they are not capable of telling you anything about the batteries. SOC voltage measurements are completely useless on a operational system, and the voltages you see do not mean anything except when you see low voltages. The only way for the SOC voltage to be relevant, is to disconnect the batteries from everything and let them set for several hours rested at room temperature. See the problem? You cannot do that on a working systems. The only way to tell the true SOC is with a temperature compensated lab quality hydrometer, and no FLA battery should be without one. . .

What you are describing is the classic symptoms of a sulfated battery for which there is no recourse or corrective action if that is the case. If you had a hydrometer would tell you instantly what is going on. But it indicates a much worse problem which most people make. You are using more power in a day than your system is capable of generating and delivering aka Deficit Charging, and it means exactly what it sounds like. You make $5 a day and spend $10 a day. In life and government you can get buy with that for a while, but there is no excuses or mercy allowed when it comes to energy. You either have it or you do not.

[miahallen]

Thanks for the reply Sunking. but with all due respect...I came here when designing the system and made sure to figure out the best components to purchase and setup. I have only been running the system for about 6 weeks...and I was watching everyday tracking my usage, and it seemed as if it was well planned and running as expected. Most mornings when I got up and checked the battery level, I would find them around 65-75% full. Which as I read in the stickies...should be perfectly acceptable.

I did order a hydrometer, but it won't be here for another month or so. I guess I will know for sure at that point. In the meantime....I really hope you're wrong

[russ]

T I would find them around 65-75% full. Which as I read in the stickies...should be perfectly acceptable.

Nowhere here did you read 65% to 75% was OK - 80% is the limit for that type of OK - you are pushing it and giving up your battery life. What happens in lousy weather?

[miahallen]

There is a common misconception that you cannot cycle batteries below 50% DoD or it will ruin them. This is totally and blatantly false for real deep-cycle batteries. They can regularly be discharged to 80% DoD and it doesn't hurt them one bit. And in fact, it makes them more efficient on charging.

here - http://www.solarpaneltalk.com/showth...ng-Gen-Support

[miahallen]

I think I might know the problem...could this have been caused by overcharging?

I think the "float" setting was way too high for the past few weeks. When I re-installed the MATE 3 a couple days ago, I set everything according to the specs (float is 52.8V), but it seems to me, that the float setting was much higher before, around 58V. Could that have caused overcharging over the past couple weeks causing damage to the batteries?

[Sunking]

I think I might know the problem...could this have been caused by overcharging?

I think the "float" setting was way too high for the past few weeks. When I re-installed the MATE 3 a couple days ago, I set everything according to the specs (float is 52.8V), but it seems to me, that the float setting was much higher before, around 58V. Could that have caused overcharging over the past couple weeks causing damage to the batteries?

Possible yes. High voltage on batteries does two things.

High water use.
Plate corrosion.

Both are easy to see.

[miahallen]

Possible yes. High voltage on batteries does two things.

High water use.
Plate corrosion.

Both are easy to see.

Just checked the water level is good...but the bottom of the caps have a lot of black residue.
What is the best thing to do at this point? The charger has been in "MPPT Bulk" all morning, but the battery level is not increasing. It is as if the charger just isn't sending any of the energy to the bank.

edit - the weird part is that I just started the generator and it seems to charge the batteries just fine. Why would the generator charge the batteries, but not the PV panels?

Would it be smart to do an EQ charge right now, or would that potentially make things worse?

[Sunking]

OK you have a problem with your equipment and needs corrected.

[miahallen]

OK you have a problem with your equipment and needs corrected.

Do you care to elaborate please?

[miahallen]

edit - the weird part is that I just started the generator and it seems to charge the batteries just fine. Why would the generator charge the batteries, but not the PV panels?

Scratch that....the charger just switched to "absorb" mode but the SoC is indicating only 15% right now

[Sunking]

Stop now, you got everyone confused.

Disconnect the batteries, let them rest a few hours, and report back the RESTING voltage please.

[inetdog]

It is not at all clear what your SOC meter thinks that it is measuring!

[miahallen]

I spoke with the local expert down here and he told me this is a common issue and that it makes sense what I'm seeing since the computer was just changed out (the MATE 3). He suggested it lost calibration because I powered it up for the first time when the batteries were low and it always starts up with the default assumption that the batteries are full. So, he had me ensure the batteries were at nominal voltage (I ran EQ for and hour with steady 62V observed, then shut the system down and let the batteries rest. After that I powered back on and the system seems to be back to normal.

I'll post back if any issues remain

edit - @SunKing, the resting voltage was about 54V

[ChrisOlson]

I spoke with the local expert down here and he told me this is a common issue and that it makes sense what I'm seeing since the computer was just changed out (the MATE 3).

None of this makes any sense. The Mate3 displays SOC but ONLY if you have a FlexNet DC in the system. Do you have one? If you don't, you can't believe anything the Mate3 tells you about SOC. Replacing the Mate3 does not affect the FlexNet DC (assuming you have one).

Lots of assumptions here because I don't know what you got there. But even if you do have a FNDC, it needs to be calibrated. And it sounds like you got your LBCO set way too high. And it sounds like your charge controllers are not even set properly.

Details. Lots of them needed.