Where is my power going?

[New England Rhinoceros]

A bit long winded but I am confused and frustrated.

I bought a whole house system from Shop Solar Kits a little over a year ago. I have eighteen 365 watt panels wired into two LV6548 inverters which charge two 9.2kw Big Batteries. We currently live in an RV on our property and the array was purchased so when we build a house next year we will have the power needed to operate our home. It seems like overkill for an RV and in my mind we should have power for days. We are frugal with our usage, we don't leave lights on when not in use, etc. All our appliances are gas, fridge, range, water heater, heat. We have a tiny wood stove that we use to heat and the heting system really only comes on overnight when the fire burns down or during the day when we aren't home. Everything is wired into an electrical panel and we have a 50amp double pole breaker that plugs into an RV cord to power the RV.

A year ago I was having trouble getting my generator to connect to my system when the days were dark enough to not get the solar I needed and spent a LOT of time on the phone with the "help desk" people at Shop Solar. What I didn't know then and learned through this forum was that I needed an inverter duty rated generator. Once we got one of those our system connects and charges no propblem. Prior to learning that the "help desk" had me changing numerous settings in my inverters and not once was mention made about an inverter duty rated generator.

Last night we had approximately 85% charge in both batteries. After 2 hours of television, with a single lamp on in the living room, one of my batteries had drained down to 15% and the other battery was discharging to bring that battery back out of the red. The television is a 40" flatscreen that was energy star rated, have had it about a month. Why would two hours of TV and a single lamp devour about 8kw of power? Are some of my settings in my inverters incorrect? Many of the settings don't line up with the default settings that I was told to try and change because of the charge problems I was having and I'm so confused and frustrated.

I will be hit or miss in response on the thread today but any and all options anyone might have would be greatly appreciated. Thank you all in advance.

Rhino

 

[Checkthisout]

A bit long winded but I am confused and frustrated.

I bought a whole house system from Shop Solar Kits a little over a year ago. I have eighteen 365 watt panels wired into two LV6548 inverters which charge two 9.2kw Big Batteries. We currently live in an RV on our property and the array was purchased so when we build a house next year we will have the power needed to operate our home. It seems like overkill for an RV and in my mind we should have power for days. We are frugal with our usage, we don't leave lights on when not in use, etc. All our appliances are gas, fridge, range, water heater, heat. We have a tiny wood stove that we use to heat and the heting system really only comes on overnight when the fire burns down or during the day when we aren't home. Everything is wired into an electrical panel and we have a 50amp double pole breaker that plugs into an RV cord to power the RV.

A year ago I was having trouble getting my generator to connect to my system when the days were dark enough to not get the solar I needed and spent a LOT of time on the phone with the "help desk" people at Shop Solar. What I didn't know then and learned through this forum was that I needed an inverter duty rated generator. Once we got one of those our system connects and charges no propblem. Prior to learning that the "help desk" had me changing numerous settings in my inverters and not once was mention made about an inverter duty rated generator.

Last night we had approximately 85% charge in both batteries. After 2 hours of television, with a single lamp on in the living room, one of my batteries had drained down to 15% and the other battery was discharging to bring that battery back out of the red. The television is a 40" flatscreen that was energy star rated, have had it about a month. Why would two hours of TV and a single lamp devour about 8kw of power? Are some of my settings in my inverters incorrect? Many of the settings don't line up with the default settings that I was told to try and change because of the charge problems I was having and I'm so confused and frustrated.

I will be hit or miss in response on the thread today but any and all options anyone might have would be greatly appreciated. Thank you all in advance.

Rhino

SOC is out of sync maybe.

Try running the Gen for a long period of time even after the batteries show 100% soc and see what kind of amps are flowing into the battery.

 

[New England Rhinoceros]

SOC is out of sync maybe.

Try running the Gen for a long period of time even after the batteries show 100% soc and see what kind of amps are flowing into the battery.

Not to sound naive, what is SOC?

 

[Danke]

State of charge. 0% = empty; 100% = full

Depending on the battery type/configuration you can also look at voltage Values.

 

[New England Rhinoceros]

State of charge

Thanks.

 

[New England Rhinoceros]

SOC is out of sync maybe.

Try running the Gen for a long period of time even after the batteries show 100% soc and see what kind of amps are flowing into the battery.

I have noticed sometimes when charging the batteries will hit 100% and still indicate they're charging. I would have thought that would be bad for the batteries.

 

[Mattb4]

Your 2 Big Batteries and how they are connected so that one attempts to charge the other seems odd to me. Likely you will need to talk to those folks. However in the meantime try charging your batteries fully by generator.

 

[Checkthisout]

I have noticed sometimes when charging the batteries will hit 100% and still indicate they're charging. I would have thought that would be bad for the batteries.

No. As long as they aren't going over voltage.

I would run the generator until charging stops and see what you end up with.

To me it looks like SOC is out of sync and the battery probably needs to balance itself as well.

Can generally solve these two issues with a good sustained charge.

 

[New England Rhinoceros]

Your 2 Big Batteries and how they are connected so that one attempts to charge the other seems odd to me. Likely you will need to talk to those folks. However in the meantime try charging your batteries fully by generator.

Yeah, me too. From day one i have been curious as to why they don't drain equally, it seems like every other day my system decides to deplete one battery for a day or two, then the other. Never made sense to me.

 

[New England Rhinoceros]

No. As long as they aren't going over voltage.

I would run the generator until charging stops and see what you end up with.

To me it looks like SOC is out of sync and the battery probably needs to balance itself as well.

Can generally solve these two issues with a good sustained charge.

OK. What would over voltage be? My system is 48v but my batteries NEVER read less than 51v or so.

 

[Quattrohead]

Do you have any method of monitoring your system like the watch power software that comes with the LV6548 or a shunt or solar assistant ?
My initial thoughts are you just don't have enough battery for your situation, those inverters are a little power hungry 24/7 even if not doing anything much.

 

[New England Rhinoceros]

Do you have any method of monitoring your system like the watch power software that comes with the LV6548 or a shunt or solar assistant ?
My initial thoughts are you just don't have enough battery for your situation, those inverters are a little power hungry 24/7 even if not doing anything much.

I do but I haven’t hooked it up. As far a battery amount, 18.4kw I feel is quite a bit. I have friends that live off grid as well with less storage than have that operate a 2500sqft house with a three bay garage with finished space above it. They have less storage but their power lasts a lot longer. I feel like one television and a single lamp for two hours shouldn’t completely deplete one of my batteries. The batteries have only cycled about 130 times apiece.

 

[Zwy]

Your batteries probably are not holding balance. Cable length needs to be the same on both batteries, best practice is run to a common busbar from each battery (with that same cable length). Positive and negative do not need to be the same length but each pair of positives need to be the same length and both negatives need to be the same length.

I'd charge each battery up fully to 100% individually if possible (using generator), then parallel them back together with the equal cable length.

If cables are the same length, then you may have a battery with a bad cell.

 

[New England Rhinoceros]

Your batteries probably are not holding balance. Cable length needs to be the same on both batteries, best practice is run to a common busbar from each battery (with that same cable length). Positive and negative do not need to be the same length but each pair of positives need to be the same length and both negatives need to be the same length.

I'd charge each battery up fully to 100% individually if possible (using generator), then parallel them back together with the equal cable length.

If cables are the same length, then you may have a battery with a bad cell.

Thank you. I have bus bars and all my cables are the same length.

 

[JWLV]

Is your battery truly 48.0 volts (15 cells)? Most LiFePo batteries are 51.2 volts (16 cells). Both are still called a 48 volt system.
If your batteries are 51.2 volts, then a fully charged battery should measure at least 53 volts. Said battery at 51 volts would indicate that it is nearly drained. Determining the battery state of charge using voltage is not an exact science. It's more of a rough estimate. You need to use a shunt or data from the battery's BMS to get the true state of charge.

 

[New England Rhinoceros]

Is your battery truly 48.0 volts (15 cells)? Most LiFePo batteries are 51.2 volts (16 cells). Both are still called a 48 volt system.
If your batteries are 51.2 volts, then a fully charged battery should measure at least 53 volts. Said battery at 51 volts would indicate that it is nearly drained. Determining the battery state of charge using voltage is not an exact science. It's more of a rough estimate. You need to use a shunt or data from the battery's BMS to get the true state of charge.

What is BMS?

 

[n2aws]

Yeah, me too. From day one i have been curious as to why they don't drain equally, it seems like every other day my system decides to deplete one battery for a day or two, then the other. Never made sense to me.

This is a red flag. This should not be the case.

I would advise taking pictures of both batteries, and how they are wired/connected to each other and posting them up for review.

 

[New England Rhinoceros]

This is a red flag. This should not be the case.

I would advise taking pictures of both batteries, and how they are wired/connected to each other and posting them up for review.

I will as soon as I get back home.

 

[New England Rhinoceros]

Is your battery truly 48.0 volts (15 cells)? Most LiFePo batteries are 51.2 volts (16 cells). Both are still called a 48 volt system.
If your batteries are 51.2 volts, then a fully charged battery should measure at least 53 volts. Said battery at 51 volts would indicate that it is nearly drained. Determining the battery state of charge using voltage is not an exact science. It's more of a rough estimate. You need to use a shunt or data from the battery's BMS to get the true state of charge.

They are 16 cells. That explains why I always read over 48v. That always confused me.

 

[Steve_S]

Please post your charging settings.
The more detailed info you can provide about your equipment the better.
Provide the specific link to your Battery Packs.

LFP is a fairly simple charge profile. It is two-stage, meaning it uses (Constant Current - Constant Voltage) for Bulk & Absorb cycles and then switches to (Constant Voltage - Variable Current) for Float to finish off the last 5% +/- and top-off / balance the cells.
* Absorb can be set to 1 hour, but would likely never reach that period as Endamps will be triggered and switched to float by that time usually..

The Transition from Absorb to Float occurs when the EndAmps/Tailcurrent is reached. This is when the internal resistance of the batteries increases to a point where they are 95% Full (real world) and can only accept a lower charge. EndAmps/Tailcurrent is calculated as follows:
100AH X 0.05 = 5A or 280AH X 0.05 = 14A

For a STANDARD 48V - 16S (16 Cell Pack) the voltages should be as follows.
54.400V (3.400 Volts per cell) = 100% full.
51.200V (3.200 Vpc) = 50% SOC and is also the Nominal Cell Voltage.
48.000V (3.000 Vpc) = 0% SOC technically *1
*1 Many people will allow it to go down as far as 2.700Vpc 43.200V and set Low Volt disconnect thee to prevent bricking the BMS if it gets too low.

Take Note: There is some general confusion & misunderstandings with regards to LFP voltage ranges. ALL Batteries have Two Ranges, the Allowable & Working voltage ranges..
LFP Allowable (which does not harm cells) is from 2.500 to 3.650 Volts. This is NOT working range.
LFP Working Voltage Range is from 3.000-3.400 which is what range delivers the specified AH rating of the cells @ Nominal Temp of 25C/77F.
LSF will ALWAYS Settle post charge, this is normal & expected. Generally we suggest charging to 3.450-3.500 MAX which will then settle to around 3.400 after about an hour post charging.

A NASTY GOTCHA !!!
When charging a battery pack, is one cell races ahead and triggers a High Volt Disconnect because it reached 3.650+ Volts, that will make the BMS report 100% Full, even if all the other cells are below 3.400. This kind of behaviour can be managed to a point by careful adjustments to teh charging profile.

Last Note on Voltage Readings.
The Battery Pack(s) voltage readings are what matters most. 99% of the time an AIO / Inverter / SCC will see 1 voltage but through line losses and wire resistance, this will not match the voltage at the battery terminals. This requires adjustments on the charger side to ensure you are not sending more power, even a 0.1 Volt difference can cause issues. Also the Low Volt Disconnect for teh Inverter Side has to be right, otherwise it could cut off too early or worse too late resulting in a bricked BMS.

Please download these resources, they will be helpful to have handy when your looking at the voltages etc.
Also grab the UPDATE graphic as well...
General LiFePO4 (LFP) Voltage to SOC charts/tables 12/24/48V

Good Luck, Hope it helps.