Midnite classic only showing 200-600 watts

[Dralkyr]

Brand new here and grateful to have found this forum.

We recently bought 4.5 acres very off grid to live and farm. We found a great deal on the latest model of DC Solar trailer and brought that out for our power. This has 10 265 watt panels, Midnite Classic controller, 2 SMA Sunny Island inverters, the light towers, and generator.

Well at first it was working okay but recently not so much. Currently the batteries are charging *really slowly.* We has full sun today from about 9am to 7pm and the batteries only went from 16% to 32%. The controller is showing only between 200 and 600 watts coming in, from what I feel should be 2.6kw. I’ve called SMA who have been as helpful as they can, but obviously they can only speak to the inverters, not the other components or the entire system.

Help!

 

[sunshine_eggo]

Get a clamp DC ammeter and check each string of panels for current flow. Look for anomalies.

Inspect all connections. Ensure they are not loose.

Assuming batteries are lead-acid, and the % reported is an accurate value reported by a quality battery monitor, stop running your batteries down to 16%. You're going to kill them damn fast. Do not discharge below 50%.

Find the model number of your panels and get the data sheet. Look at the NOCT rating. This is a "real world" rating that factors in things like reduced solar input and hot panels. 2000W is a more reasonable expectation... and that's at high noon with the panels pointed perfectly perpendicular to the sun. At all other times, you'll get less.

 

[Dralkyr]

I never intend to run them that low. The generator *should* be kicking on automatically at 50% and charging them to 95, but even that setting is obviously not working properly.

 

[sunshine_eggo]

Something else I didn't consider, is probably not in play, but is worth mentioning.

Lead acid batteries should only be charged so fast. I would expect faster than 600W, but typically it's about 10% of rated, i.e., a 500Ah battery should be charged at no more than 50A.

A way to test if you're up against some sort of arbitrary limit is to add a big load. If the solar jumps to help power the load, you know something else is at play. if you were closer to fully charged, if the battery is in absorption phase, it's voltage limited, so the battery will only accept as much power (current) as it needs to maintain the absorption voltage. Again, a big load applied at this time should show the array power increasing to meet the demand.

 

[fromport]

Brand new here and grateful to have found this forum.

Well at first it was working okay but recently not so much. Currently the batteries are charging *really slowly.* We has full sun today from about 9am to 7pm and the batteries only went from 16% to 32%. The controller is showing only between 200 and 600 watts coming in, from what I feel should be 2.6kw. I’ve called SMA who have been as helpful as they can, but obviously they can only speak to the inverters, not the other components or the entire system.

first: I took the light towers off ( warning: with a forklift, they are _top heavy_) since the shade during the afternoon is a real bummer.

Can you take a photo of the midnite solar CC half an hour before it gets dark and post it here?
That will show voltage and amount of kWh the panels produced during the day.

Just a headsup: I have yet to see a DC-solar trailer where the forklift batteries had > 50% capacity left.
I personally inspected 15 or 16 so far and they were all trashed. Not saying your batteries are shot, but the odds are not in your favor.

 

[Dralkyr]

first: I took the light towers off ( warning: with a forklift, they are _top heavy_) since the shade during the afternoon is a real bummer.

Can you take a photo of the midnite solar CC half an hour before it gets dark and post it here?
That will show voltage and amount of kWh the panels produced during the day.

Just a headsup: I have yet to see a DC-solar trailer where the forklift batteries had > 50% capacity left.
I personally inspected 15 or 16 so far and they were all trashed. Not saying your batteries are shot, but the odds are not in your favor.

Well… that sucks
Yes, I can get that tomorrow.

It has previously been charged to 100% within the last few months.

 

[fromport]

Well… that sucks
Yes, I can get that tomorrow.

It has previously been charged to 100% within the last few months.

Many threads on this forum about the DC-solar trailers, like this one: https://diysolarforum.com/threads/dc-solar-trailer-lbm-questions-newbie.25803

 

[Dralkyr]

Here are two images from the controller. First was at 9am and second at 2:11pm. Even with it showing 1557 watts the batteries have only come up to 33% soc according to the inverter.

 

[fromport]

Here are two images from the controller. First was at 9am and second at 2:11pm. Even with it showing 1557 watts the batteries have only come up to 33% soc according to the inverter.

9:00 am
Voltage is 46.7, divide that by 4 to have reference to a 12 volt battery = 11.675 volt
According to many tables out there on the internet but let me use this as an example:

Deep cycle battery voltage & state of charge

A guide to determining deep cycle battery depth of discharge and how battery voltage levels relate to remaining capacity.

www.energymatters.com.au

11.8 volt is 100% depleted.
A lead acid battery should never go below 50% so you are KILLING your battery
50%=12.3V x 4 =49.2 minimum voltage

If the 10 underpowered panels on the trailer are able to "recharge" your battery to 33% in 5 hours i only can make one conclusion:
Your batteries are shot.

Welcome to the club

 

[Dralkyr]

9:00 am
Voltage is 46.7, divide that by 4 to have reference to a 12 volt battery = 11.675 volt
According to many tables out there on the internet but let me use this as an example:

Deep cycle battery voltage & state of charge

A guide to determining deep cycle battery depth of discharge and how battery voltage levels relate to remaining capacity.

www.energymatters.com.au

11.8 volt is 100% depleted.
A lead acid battery should never go below 50% so you are KILLING your battery

If the 10 underpowered panels on the trailer are able to "recharge" your battery to 33% in 5 hours i only can make one conclusion:
Your batteries are shot.

Welcome to the club

Well... shoot. They did sit with low water for over a week because we live a long way from any stores and all the stores were out or limiting distilled water. We undid all the loads and left during that time, but still.

 

[fromport]

Well... shoot. They did sit with low water for over a week because we live a long way from any stores and all the stores were out or limiting distilled water. We undid all the loads and left during that time, but still.

it probably doesn't make you feel better, but imo a week with low water won't kill those batteries

 

[Dralkyr]

it probably doesn't make you feel better, but imo a week with low water won't kill those batteries

They were working decently before and would get up to 100%. They never worked perfectly - something was always weird about the settings - but now it's just bad.

 

[sunshine_eggo]

it probably doesn't make you feel better, but imo a week with low water won't kill those batteries

Charging them with low water will.

 

[Dralkyr]

Charging them with low water will.

I tried to get all the load off of them and un-deployed the panels. But obviously I should have just turned everything off :'(

 

[fromport]

They were working decently before and would get up to 100%. They never worked perfectly - something was always weird about the settings - but now it's just bad.

But you also have proven your own subject wrong:
the 14:30 photo clearly shows 1557 watts being put into the battery, that is 4-2.5 times more than you claimed in the subject.

a)
the panels on the trailer are about 1/10 of what it should be for the size of the batteries to re-charge.
b)
You are draining the batteries below 0% which is _really_ bad
c)
if the voltage goes up to 33% in 5 hours and according to the midnight solar CC 7.7 kWh that would be roughly x3 for 100% = 21kWh.
The units are 510Ah x 48 volt x 2 batteries = 49kWh in new state.
As it indicates now, your batteries are 21/49 = 42% of new capacity.

Take all this with a big grain of salt, this is just a very rough indication.

The inverters should be set to stop inverting at 49Volt in order to prolong life on your batteries.
The fact that someone obviously already overruled that setting means more evidence the previous owner new it was shot.

 

[Dralkyr]

But you also have proven your own subject wrong:
the 14:30 photo clearly shows 1557 watts being put into the battery, that is 4-2.5 times more than you claimed in the subject.

a)
the panels on the trailer are about 1/10 of what it should be for the size of the batteries to re-charge.
b)
You are draining the batteries below 0% which is _really_ bad
c)
if the voltage goes up to 33% in 5 hours and according to the midnight solar CC 7.7 kWh that would be roughly x3 for 100% = 21kWh.
The units are 510Ah x 48 volt x 2 batteries = 49kWh in new state.
As it indicates now, your batteries are 21/49 = 42% of new capacity.

Take all this with a big grain of salt, this is just a very rough indication.

The inverters should be set to stop inverting at 49Volt in order to prolong life on your batteries.
The fact that someone obviously already overruled that setting means more evidence the previous owner new it was shot.

The wattage never got that high yesterday, so from the post yesterday it was accurate. Yes, at our fullest sun today we were getting much more - yay.

a) That's.... unfortunate
b) I'm draining them below 0%?
c) Is that to say that the 33% soc is ~78% of its current max charge? 100/42*33 = 78.

I really don't know what's up with the settings. I've even called SMA and they walked me through doing what I thought was a full factory reset, but things continued to be weird.

 

[sunshine_eggo]

The inverters should be set to stop inverting at 49Volt in order to prolong life on your batteries.

This is not a sensible recommendation. FLA voltage to SoC relationships are only valid when the batteries have been at complete rest (no charge/discharge) for at least two hours, preferably more than 10 hours.

It's not the low voltage that kills them. It's the low state of charge.

Significant loads can easily pull batteries down below 12.25V when they can be happily resting fully charged at 12.6V. The only way I would ever consider such a restrictive cut off is if it can also be coupled with a duration, e.g., drops below 49V for 15 minutes for something arbitrary. The reality is that cut-off should be based on SoC computed with a quality battery monitor. If one is intimately familiar with their system

 

[fromport]

The wattage never got that high yesterday, so from the post yesterday it was accurate. Yes, at our fullest sun today we were getting much more - yay.

a) That's.... unfortunate

This trailer was designed for a ponzi scheme, not a real usable item.

Solar Power Ponzi Couple Pleads Guilty In Billion-Dollar Fraud

An auction of the Carpoffs’ 140 cars fetched $8.3 million. Highlights included a 1969 Plymouth Road Runner and a 1978 Pontiac Trans-Am once owned by Burt Reynolds.

www.forbes.com

Imo they could have saved some real money by only using 1 forklift battery

b) I'm draining them below 0%?

Yep, like I wrote before: 0% would be 49.2Volt
You showed with photo 1 at 9:30, when the midnite already put 0.5kWh into the battery that the voltage was "up" to 46.7
Taking 49.2 Volt as completely empty, you emptied it below 0 and doing serious harm to what is left from the battery capacity.

c) Is that to say that the 33% soc is ~78% of its current max charge? 100/42*33 = 78.

I am not going to try and follow your reasoning.
Let me write mine down differently
if 33% soc == 7.7kWh (photo2)
100% would be x 3 -> 3 x 7.7 = 23.1 kWh to have your battery 100% SOC

your batteries SHOULD be 49kWh when 100%SOC

23.1/49 = 42% battery life left.

That is my (crude) deduction based on the info that is currently available to me.

I really don't know what's up with the settings. I've even called SMA and they walked me through doing what I thought was a full factory reset, but things continued to be weird.

Each inverter has a minimum voltage where it will say "battery empy, i will stop using energy from the battery now"
That is probably not set in your inverter(s) and thus you drain your batteries below 0% without any security.

 

[fromport]

This is not a sensible recommendation. FLA voltage to SoC relationships are only valid when the batteries have been at complete rest (no charge/discharge) for at least two hours, preferably more than 10 hours.

It's not the low voltage that kills them. It's the low state of charge.

Significant loads can easily pull batteries down below 12.25V when they can be happily resting fully charged at 12.6V. The only way I would ever consider such a restrictive cut off is if it can also be coupled with a duration, e.g., drops below 49V for 15 minutes for something arbitrary. The reality is that cut-off should be based on SoC computed with a quality battery monitor. If one is intimately familiar with their system

I did hope you read my disclaimer that it was a rude evalution?!

What voltage would you say the inverter should cut off in this case?

I just looked up datasheet of similar battery:

Do not discharge (drain) batteries over 70% of rated capacity.
Do not use batteries with specific gravity below 1120
Properly charge batteries with matched chargers. Do not undercharge or overcharge the battery. (Voltage, A.H. and type. Max overall AH variance of 10%)
Always allow your battery to cool down after charging. (Ideal usage: 70% discharge, 6-8 hours charge time, 4 hours cool down time)

 

[sunshine_eggo]

I did hope you read my disclaimer that it was a rude evalution?!

I did, but you went on to make a fairly forceful sounding recommendation and claims of cause/outcomes.

What voltage would you say the inverter should cut off in this case?

It depends on the system and usage. 49V as an arbitrary "should" is almost certainly going to cause most people frustration as their inverter kicks off regularly with normal use while the battery remains at a high state of charge.

If you MUST be arbitrary about it, select something down around 20-30% SoC for the specific model of battery. My Rolls indicate - 11.8V. Most batteries will survive a few hundred cycles to this depth without catastrophic failure.

I just looked up datasheet of similar battery:

Do not discharge (drain) batteries over 70% of rated capacity.
Do not use batteries with specific gravity below 1120
Properly charge batteries with matched chargers. Do not undercharge or overcharge the battery. (Voltage, A.H. and type. Max overall AH variance of 10%)
Always allow your battery to cool down after charging. (Ideal usage: 70% discharge, 6-8 hours charge time, 4 hours cool down time)

That is the most viable option for FLA as SG is the strongest correlation to SoC available; however, it does lag as well and can be inaccurate due to stratification of the electrolyte.

I routinely test 12V down to 10.5V@25A to validate their reserve capacity rating. This doesn't do damage because there is still typically around 10-20% of their C20 capacity rating.

Voltage, current, SoC and temperature are all in play.