Plum Crazy Rob
Solar Enthusiast
Battery Management System
Where is my power going?
- Thread starter New England Rhinoceros
- Start date
DIYrich
Solar Wizard
Is this the battery you have?
shopsolarkits.com
Do you have grid power available?
BigBattery 48V [GRIZ] 9.2kWh Lithium Powerwall | 9,200wH / 180Ah - ShopSolar.com
This 9.2kWh 48V GRIZ is a leading lithium ion-based battery bank that can be used in a variety of applications. We're dedicated to keeping the environment clean and believe it's necessary to displace dirty diesel generators at construction sites, factories, offices, hospitals, homeless shelters...
shopsolarkits.com
New England Rhinoceros
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I do not have grid access. This is the battery I have. Two of them.Is this the battery you have?
Do you have grid power available?BigBattery 48V [GRIZ] 9.2kWh Lithium Powerwall | 9,200wH / 180Ah - ShopSolar.com
This 9.2kWh 48V GRIZ is a leading lithium ion-based battery bank that can be used in a variety of applications. We're dedicated to keeping the environment clean and believe it's necessary to displace dirty diesel generators at construction sites, factories, offices, hospitals, homeless shelters...
DIYrich
Solar Wizard
What are settings 26 and 27 on your inverter?
Set 26 to 58.0v
Set 27 to 54.4v
Charge battery and let it float for a few hours.
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Steve_S
Offgrid Cabineer, N.E. Ontario, Canada
NO THAT IS TOO HIGH !
58.0V = 3.625 Volts per Cell ! DON'T !
56.0V = 3.500 Volts per Cell and that is MAX for a Working Battery Pack.
Even then, this is still considered Aggressive hence why a Majority of longterm LFP users will not go over 3.450 Vols per cell or 55.2 Volts for Bulk/Absorb and Float at 55.00V or 3.437Volts per cell.
The ONLY TIME to charge Battery cells to 3.6## is to Top Balance or after longterm storage ONLY !!!
This is also stated in many manufacturers spec sheets.
New England Rhinoceros
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The Shop Solar "help desk" had me set those values even higher than that. Should I return those settings to factory?
DIYrich
Solar Wizard
Thread 'Recommended Charge Profile for DIY LiFePO4 Batteries *Sticky Post*' https://diysolarforum.com/threads/r...e-for-diy-lifepo4-batteries-sticky-post.5101/
Also, the specs for the battery state a charging rate of 55.6-58.0v.
If OP's batteries are not charging to full on a regular basis with solar, then the additional Volts (increased watts at same max amps) may help a little.
zanydroid
Solar Wizard
Big Battery is having some big time drama right now with its supplier, I don't know how productive this would be.
DIYrich
Solar Wizard
What were the original values? What are the Shop Solar values? How long did you charge from generator?
New England Rhinoceros
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Default are 56.4 bulk charge and 54.0 float charge. Current values are set to 58.0 bulk and 54.4 float. Generator charge time depends on battery depletion.
Steve_S
Offgrid Cabineer, N.E. Ontario, Canada
DIYRich, Will wrote that in 2020 and has become more moderate.
Whatever, a decade + exp and being an retired engineer, I know nothing, see nothing and hear nothing.
Good thing I tell my clients the reasonable & problem free settings/values and never have to deal with such.
You simply are NOT doing yourself ANY FAVOURS by pushing beyond the Working Voltage, the consequences are all yours.
Good Luck
PS, Even Andy @ Andy's garage finally wised up and suggests the same voltages.
Whatever, a decade + exp and being an retired engineer, I know nothing, see nothing and hear nothing.
Good thing I tell my clients the reasonable & problem free settings/values and never have to deal with such.
You simply are NOT doing yourself ANY FAVOURS by pushing beyond the Working Voltage, the consequences are all yours.
Good Luck
PS, Even Andy @ Andy's garage finally wised up and suggests the same voltages.
New England Rhinoceros
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My battery setting is set to "USE" which I believe is user defined. My default battery equalization is set to disabled but the very limited manual with my inverters says I can set this value, (program 30) to enable battery equalization if my batteries are set to USE.
What values would you recommend? I'm at my wits end here and have a LOT of money in this system.
He is only changing the inverter settings anyway. The BMS is going to control the charge situation as long as the inverter is providing more voltage than the BMS needs it isn't going to impact the battery. 58v at the inverter doesn't translate to 3.625v/cell because the BMS is just going to disconnect from the supply when it sees fit. Personally I run my inverters at 56.4 for all bulk and float and the BMS's take care of the rest. 58 is high but with ANY decent BMS it won't cause problems because even with a 56v setting the BMS will disconnect when it needs to . The risk of running 54v float charge though is that his BMS is never resetting to 100% because the inverter is not giving the BMS enough voltage to ever see an OV situation or whatever triggers it to "decide" the batteries are 100% and re-calibrate. That is likely why he is seeing the SOC reading be way off.
Especially with two batteries without really good data communication between batteries and inverter there is no guarantee that they both need the same voltage at the same moment in time (to come to full charge) so better to run it a bit high and let the batteries do what they are supposed to for themselves.
Especially with two batteries without really good data communication between batteries and inverter there is no guarantee that they both need the same voltage at the same moment in time (to come to full charge) so better to run it a bit high and let the batteries do what they are supposed to for themselves.
Steve_S
Offgrid Cabineer, N.E. Ontario, Canada
LFP NEVER EVER Gets Equalization which should be disabled IF POSSIBLE and if not set to no higher voltage than BULK/ABSORB.
IF you have 1 cells in a battery reach High Volt Disconnect, the whole pack stops charging.
A runner can & WILL run ahead once passed 3.450 on average... That will cause the other cells to not gain charge.
When more than 1 pack is in parallel, this can and WILL Handicap the entire bank. This is because the other battery may gain higher charge, but as soon as charging end it will attempt to backcharge the lower sibling. This can be observed by watching the BMS's apps.
USE is User Setting.
IF you have 1 cells in a battery reach High Volt Disconnect, the whole pack stops charging.
A runner can & WILL run ahead once passed 3.450 on average... That will cause the other cells to not gain charge.
When more than 1 pack is in parallel, this can and WILL Handicap the entire bank. This is because the other battery may gain higher charge, but as soon as charging end it will attempt to backcharge the lower sibling. This can be observed by watching the BMS's apps.
USE is User Setting.
@New England Rhinoceros, you're getting a lot of good info here. You mentioned the cables from the inverter to the batteries are the same length (and I'm assuming gauge). Good. Have you confirmed that the fasteners are tight? A loose terminal connection can cause the batteries to discharge at different rates. This is something to check whenever diagnosing a problem like this. Fasteners can loosen over time, esp. if not torqued correctly at install.
As you continue to develop this system you may want to buy a Kill-a-watt or similar meter to measure consumption of individual loads. You mention that the TV and lights shouldn't have drained the batteries so much and I agree. What's the actual consumption of the fridge (maybe it's propane in your RV), of your Starlink or other internet service. The Kill-a-watt or other meter will move you from assumptions to more precise knowledge that you'll rack up to better answer the questions.
IMHO, don't get too caught up in charger set points at this time. Set them at the conservative numbers suggested by Steve_S and track down the original problem. You can learn more about them and make choices once you've solved the primary problem.
Why does equalization never apply to LFP? Equalization is used for older lead-acid chemistry batteries and is designed to way overcharge the cells periodically (once a month or so). This can be therapeutic to lead acid batteries leading to longer battery life. It can/will kill LFP batteries. It's ridiculous that the software designers don't automatically disable the equalization option if LFP batteries are selected but they all don't so set it to a low voltage and/or short time period so your batteries are never overcharged using this setting.
Unless the products are faulty you'll figure this out and learn how to diagnose and solve in the future.
As you continue to develop this system you may want to buy a Kill-a-watt or similar meter to measure consumption of individual loads. You mention that the TV and lights shouldn't have drained the batteries so much and I agree. What's the actual consumption of the fridge (maybe it's propane in your RV), of your Starlink or other internet service. The Kill-a-watt or other meter will move you from assumptions to more precise knowledge that you'll rack up to better answer the questions.
IMHO, don't get too caught up in charger set points at this time. Set them at the conservative numbers suggested by Steve_S and track down the original problem. You can learn more about them and make choices once you've solved the primary problem.
Why does equalization never apply to LFP? Equalization is used for older lead-acid chemistry batteries and is designed to way overcharge the cells periodically (once a month or so). This can be therapeutic to lead acid batteries leading to longer battery life. It can/will kill LFP batteries. It's ridiculous that the software designers don't automatically disable the equalization option if LFP batteries are selected but they all don't so set it to a low voltage and/or short time period so your batteries are never overcharged using this setting.
Unless the products are faulty you'll figure this out and learn how to diagnose and solve in the future.
New England Rhinoceros
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I agree. A LOT of good info. Difficult to sort through it because some of it is conflicting. I do notice that initially (February when I got an inverter duty rated generator) my batteries would charge much more quickly. Now they seem to take quite a bit of time. I will reset my charge points to more conservative numbers and go from there. I’ll look into the Kill-o-watt or similar meter and see what I can see. I appreciate all the feedback here. Thanks.
Zwy
Emperor Of Solar
I'd run the default bulk charge at 56.4V, float at the 54.4V you currently have. This will allow balancing to occur between cells yet keep the BMS from disconnecting with a runner cell. It is quite possible the cells have become severely unbalanced and this will take time to correct.
I find 58.0V bulk too high. There is no need for it, those few Ah's between 99% and 100% SOC aren't worth sacrificing long term cell life. At 54.4V on float, it will allow balancing to occur as that translates to 3.4V per cell. That is where I set my float at.
Conservative is good but I would increase your float up to a tad over 56v. Example here is a charge curve from my batteries this morning (I run a similar off grid to RV setup as you) only with 2x 5KWH Trophy batteries and an EG4-6000EX inverter. To points others have made it is very likely your batteries SOC monitor is off. Most of the BMS' need to see a few minutes of no current flowing with an input voltage higher than the pack. In the example below the SOC rise from 12:05 to 12:25 is real charging happening (energy into the battery). The rapid rise just before 12:40 is not charging it is the BMS deciding that it must surely be at 100% because it has had plenty of volts to charge from but no current flowing. This is how the BMS "resets" the SOC (not all BMSs make this decision the same way, some will trip to 100% with a single cell going over voltage, which as "Andy" has pointed out is kind of dumb). You can see from the second graph that if the inverter supply voltage was only at 54V (green line) that period of charge from ~96.1SOC to ~97.2 SOC would never have happened and the battery would never have reset to 100%. Because the BMS also assumes standby losses over time it would tend trend down falsely. In the second graph the green line is inverter supply and the yellow is pack voltage. Whenever the two lines are on top of each other (ish) the BMS has the batteries connected to the inverter supplied voltage. When they are clearly separate it is because the BMS itself (not the inverter) has chosen to stop charging (disconnect from supply). Without watching these data points on the BMS you wouldn't know this was going on, the battery would always be ready to supply power to the loads.
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Zwy
Emperor Of Solar
I would probably disconnect one battery while the generator is charging the other and use a separate charger plugged into the generator to charge the other. Something like the Chargeverter or another inverter with charging capability.
New England Rhinoceros
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There is a reading on my batteries on the status screen that says BmsSat: 0000
What does that mean?
Also, are my inverters also my BMS?
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