Mpp 1012lv display voltage

[SeanWatts]

I have an mpp 1012LV that I just set up, connected to 3, parallel 12v 100ah lifepo4 batteries all connected with 2awg copper.

The display says 13.7 volts.
My volt meter on the mpp lugs say 13.5 volts, and each battery shows 13.48 at the terminals.

It has been in the sun all day yesterday and today, and the voltage at the batteries has not gone over 13.48.

Setting 26 is set to 14.4
Setting 27 is set to 13.6

Panels: 2x 230 watt 39 ocv in series.

Does that sound right? Why is the battery not charging past 13.48?

I hooked up an inverter style ac, that I had working yesterday, and it showed it was pulling 600 watts. Today, it will run for a minute then goes into fault and shuts the inverter off.

Not sure what is going on.

 

[sunshine_eggo]

I have an mpp 1012LV that I just set up, connected to 3, parallel 12v 100ah lifepo4 batteries all connected with 2awg copper.

The display says 13.7 volts.
My volt meter on the mpp lugs say 13.5 volts, and each battery shows 13.48 at the terminals.

If current is flowing, that may explain the discrepancy. What are the values when PV input is 0.

It has been in the sun all day yesterday and today, and the voltage at the batteries has not gone over 13.48.

The vast majority of charging occurs below 13.8V.

Setting 26 is set to 14.4
Setting 27 is set to 13.6

Panels: 2x 230 watt 39 ocv in series.

460W / 13.5V = 34A max output in perfect conditions.

Does that sound right? Why is the battery not charging past 13.48?

With no loads of any kind, 1-2 days to fully charge. Note that the inverter itself consumes power. 15W * 24h = 360Wh = about 25% of one of your battery's capacity.

what gauge wire?

Have you confirmed that all connections are of high quality and properly torqued?

 

[SeanWatts]

If current is flowing, that may explain the discrepancy. What are the values when PV input is 0.
I

I disconnected the pv negative, and the voltage on the screen was within .02 of the terminal on the mpp, and within .04 of at the terminals, so that is not bad.

The vast majority of charging occurs below 13.8V.

It has never gotten that high. Only 13.48 at the battery.

460W / 13.5V = 34A max output in perfect conditions.



With no loads of any kind, 1-2 days to fully charge. Note that the inverter itself consumes power. 15W * 24h = 360Wh = about 25% of one of your battery's capacity.

I have been turning the inverter off at night, and didn't turn it back on until I tested the ac again this afternoon.

what gauge wire?

2awg copper

Have you confirmed that all connections are of high quality and properly torqued?

I used the hammer style crimper, copper lugs, and voltage reads the same weather from the terminal or the cable end, so I would think it should be okay. I did not put a torque wrench on it though.

I guess my concern is that it doesn't seem to take anymore charge once the mpp shows 13.6 on the screen. And that it cannot run an inverter style ac that is rated at 700 watts, but was only pulling 600 watts yesterday.

 

[sunshine_eggo]

I disconnected the pv negative, and the voltage on the screen was within .02 of the terminal on the mpp, and within .04 of at the terminals, so that is not bad.

That confirms the discrepancy is due to wiring losses. 0.2V feels a little high.

It has never gotten that high. Only 13.48 at the battery.

Which may mean that you have never fully charged the battery. If you are powering loads, you may not be keeping up. If your array gets any shade or is getting excessively hot, you may have notably reduced output.

I have been turning the inverter off at night, and didn't turn it back on until I tested the ac again this afternoon.

That helps.

2awg copper

That's okay.

I used the hammer style crimper, copper lugs, and voltage reads the same weather from the terminal or the cable end, so I would think it should be okay.

That ONLY matters when current is flowing. You get your answer when big current is flowing.

I did not put a torque wrench on it though.

Proper torque can be critical.

I guess my concern is that it doesn't seem to take anymore charge once the mpp shows 13.6 on the screen. And that it cannot run an inverter style ac that is rated at 700 watts, but was only pulling 600 watts yesterday.

A valid concern, but we don't know why it's happening.

I would not attempt to power any loads at all for the next 1-2 days. Observe the charging behavior. Is it still taking current at 13.XXV? If so, it's still charging. If you can also use the AC charger to fully charge the batteries, I would do so.

You may be dealing with a situation where your cheap LFP batteries are imbalanced and refusing to accept current due to a single cell being over-voltage. It's pretty common.

Once you have confirmed the batteries are fully charged, then discharge testing is next.

 

[JAS]

FYI: I have the same unit and also see voltage discrepancies... sometimes as much as half a volt. This usually during AC charging. In my case, charging would stop prematurely. I adjusted the charging parameters accordingly and watched if/when the BMS cut off charging due to high cell voltage and adjusted again... Voltmeter readings at the Inverter terminals are/were nearly identical to the battery terminals. So the voltage inaccuracy is internal to the MPP unit..

I did get a firmware update from MPP (via Ian at Watts247), but never installed it since I now use Solar Assistant to control when the switching from AC passthru to Inverter happens.

 

[SeanWatts]

That confirms the discrepancy is due to wiring losses. 0.2V feels a little high.

How so? Disconnecting one of the pv cables made the screen show the correct battery voltage, and voltage from the terminal on the mpp was within .02 volts of the voltage on the battery terminal. Sounds to me that the discrepancy is in the mpp unit when it is getting power from pv, the screen does not show the correct voltage.

Which may mean that you have never fully charged the battery. If you are powering loads, you may not be keeping up. If your array gets any shade or is getting excessively hot, you may have notably reduced output.



That helps.



That's okay.



That ONLY matters when current is flowing. You get your answer when big current is flowing.

It's only a 12v system and the 700 watt ac is the biggest load it will ever see.

Proper torque can be critical.



A valid concern, but we don't know why it's happening.

I would not attempt to power any loads at all for the next 1-2 days. Observe the charging behavior. Is it still taking current at 13.XXV? If so, it's still charging. If you can also use the AC charger to fully charge the batteries, I would do so.

When the display on the mpp shows 13.6 it throttles down pv to 20 watts.

You may be dealing with a situation where your cheap LFP batteries are imbalanced and refusing to accept current due to a single cell being over-voltage. It's pretty common.

I never mentioned the cost or brand of my batteries. They all came out of the box at 13.1 volts. I connected them together and let them settle for a few hours before I connected them to the mpp unit

Once you have confirmed the batteries are fully charged, then discharge testing is next.

 

[SeanWatts]

Update, I added two more of the same solar panels, so now it is 2s2p of 230 watt panels.

Currently the display says 13.6 volts and is only taking in 20 watts. Battery voltages where 13.66 on each of the terminals. I am guessing only 20 watts is because it is in float charge?

 

[sunshine_eggo]

I missed the .02v difference. Agreed.

Are you watching the unit to confirm that it never attains 14.4V?

But you have gone from a max of 13.48 to 13.6?

 

[SeanWatts]

I missed the .02v difference. Agreed.

Are you watching the unit to confirm that it never attains 14.4V?

I have been checking on it every couple hours. I have yet to see above 13.66 at the batteries while the panels are in full sun.

But you have gone from a max of 13.48 to 13.6?

Yes, which is going in the right direction at least.

 

[sunshine_eggo]

I have been checking on it every couple hours. I have yet to see above 13.66 at the batteries while the panels are in full sun.

The run from 13.6 to 14.4V can be VERY abrupt - on the order of 15 minutes. If the unit only spends 30 minutes in absorption, you might miss it.

Yes, which is going in the right direction at least.

IMHO, set float to 14.2V just to confirm you're not missing the drop to float.

 

[TomC4306]

connected to 3, parallel 12v 100ah lifepo4 batteries

I think you're just being impatient.
And, since new, you haven't ever charged them up.

12.8v x 300ah = 3840 watt hours.
Assuming they were at 30% SOC when you got them, means 2688 watt hours to fully charge.
WITHOUT Loads....