New LFP House Battery
- Thread starter SycloneDriver
- Start date
I will check when I am on the boat tomorrow.
i don’t recall seeing that menu option when i went through the settings, but maybe i missed it or it is called something else. I do have a Charge switch and a Discharge switch. The discharge switch will kill the outflow of power out of the battery. But in the photos, both batteries are showing the discharge switches as being on.
Greg
I don't see anything wrong.I don’t want to hijack @SycloneDriver’s post, but this is AlFP system related, so hopefully not egregious… if I should start a new thread, please comment,
I was checking my new Humseink LifePo4 batteries today after the batteries have been on the charger for a few days. Batt 1 showed 100% SOC and Batt 2 showed 99%. Interestingly, the BMS on Batt 1 shut off the charging switch. I assume since it was at 100% and couldn’t accept any more charge. The batteries are paralleled (see photo below).
View attachment 233092
I went out for a 2.5 hour sail today, with a light load on the house bank (fridge, VHF, stereo, CP & instruments).
When I got back, I left the charger off until I could check the BMS for the 2 batteries. Now, Batt 1 still showed 100% SOC and batt 2 was at 86% SOC.
I am not sure why these batteries, if wired in parallel, would not supply power to the house system in equal measure. Instead, it seems that one battery is doing all of the work
View attachment 233093 View attachment 233094
I have written to Humseink to see what they can tell me (if anything). I have discovered that their BMS app will not let me see what the individual cells are doing. They did say that their engineers are working on an upgrade to the app.
So, here is a crude drawing of my DC system (left out the AC side of the equation for now)...and only the house side. Left off the starter battery, switch, charger, etc for that.
View attachment 233095
Does anyone see anything blatantly wrong with this set up (I hope not, as I have sailed with it a few times now). Or could this just an issue with the batteries? One thing I could try is to install a positive and negative bus bars and hook each battery individuslly to the bus bars. But the charger would charge the bus bars (single output charger ). Not sure that changes things much. Does paralleling LFP batteries need to be different than FLA?
Greg
I am curious as to what you have the charge and maintenance voltages set at in the charger?
Does the alternator have a programmable regulator?
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 23,162
It was a glorious sunny day, and it was time to test the solar panel charging my LFP.
A 50-watt panel is producing 36 watts. The app says that at this rate, it will take 36 hours to fully charge your battery. The battery is at 18%. So I let it go, and an hour before sunset, the battery had recovered to 25%.
My second battery was at 22%. I plugged in the 12V 25W Victron charger. When I got going, the message was that 25amps at 14.2 would take 3 hours to charge the battery.
When it was at 100%, I disconnected the battery, put it away, attached the solar-charged battery (at 25%) to the power charger, and went off to dinner. By the time I returned, it was at 75%.
A 50-watt panel is producing 36 watts. The app says that at this rate, it will take 36 hours to fully charge your battery. The battery is at 18%. So I let it go, and an hour before sunset, the battery had recovered to 25%.
My second battery was at 22%. I plugged in the 12V 25W Victron charger. When I got going, the message was that 25amps at 14.2 would take 3 hours to charge the battery.
When it was at 100%, I disconnected the battery, put it away, attached the solar-charged battery (at 25%) to the power charger, and went off to dinner. By the time I returned, it was at 75%.
This can happen when the individual cells in a battery are not balanced. The BMS will continue accepting a charge until all the cells are balanced at (or very close to) the same voltage. In use the cells will not charge or discharge evenly, top balancing returns them to equal voltages. This is pretty normal behavior for LFP batteries.
The other problem, uneven discharge between the 2 batteries seems more unusual. It may take a few charge/discharge cycles for the BMS to learn the SOC. The usual causes for the imbalance between the 2 batteries are uneven jumper lengths or the manner in which the batteries are put in parallel. The way you have wired the batteries was once the recommended method, it is still fine, however, current thinking has the batteries connected to a bus bar to parallel them and the loads taken off the bus. Buried somewhere on the Victron site is a basic wiring manual that shows the different methods of paralleling batteries. There may also be information on Calder's site, www.BoatHowTo.com.
While we're looking at the photos, the DC+ wires all need to be fused. One of the dangers of LFP batteries is the amount of current they can discharge in a short time. There should only be 2 DC+ connections on the battery, the jumper from B1 and B2 and the cable to a Class T fuse. A Class T fuse should be used because it has a higher interrupt level (AIC) than other fuses. If there is a short the power delivered from an LFP battery can arc across a blown fuse. Class T fuses prevent the arcing. All the wires after the Class T fuse can be fused with other styles of fuses. ATC fuses in inline holders or a Blue Seas fuse box will work. The fuse box is a bit neater.
Hi Troy,
My alternator (original dumb alternator), is still wired to my starter battery, so it is not in the house system.
My charger is a new 20-amp Victron.
It doesn’t say what the “bulk” setting is. I think it is around 13.5 or so.
Greg
Thanks Dave,
I was disappointed to learn that the BMS app for these Humseink batteries won’t let me look at individual cells
But I had the batteries on the Victron for a few days, so I was assuming it would have balanced the cells (and the batteries).
I turned off the discharge switch on the lower voltage battery last night, forcing the 100% SOC battery to run the fridge overnight. I will check on them today to see what the look like. Oddly, I think they were acting like “normal” a few days ago, showing a draw on both batteries. Even though they did not show an identical SOC, both were sharing the load it appeared.
I am using an MRBF fuse on the DC+ wire. Not as good as a T fuse?
Appreciate the tips.
Greg
”Bulk” is not a voltage setting. It is maximum current that the charger can apply. With a discharged battery, the voltage at that current will initially be below the absorption voltage setting. As the battery SOC gets higher, its voltage will rise. Once the programmed absorption voltage is reached the charger will reduce the charge current so as not to exceed the absorption voltage setting.
Looking at your screenshot it appears battery 2 has its discharge FETs off, even though the app is reporting they are on. Notice the difference in voltage (13.15V vs 13.38V). You can have small differences in reported voltage with paralleled batteries but not that large. Can you cycle the discharge FET switch? Maybe that will reconnect it.
I'm not familiar with that brand of battery, but 13.2V is too low a float voltage for lifepo4 chemistry.... ideally 13.5-13.8V. In the case of lithium, absorption = bulk.....
I wouldn't trust a BMS that doesn't let you monitor individual cell voltages..... just like a flooded lead acid battery, lithium batteries do require some monitoring and maintenance especially when connected in parallel. Sometimes they have to be separated to be rebalanced.
If you can't confirm cell balance, I'd use a lower charge voltage, maybe 13.8 to 14.0V.... to avoid large cell imbalances. A large imbalance could trigger the BMS to shut down the charge MOSFETs....
MRBF fuse is not recommended for a lithium battery.... get a good quality Class T fuse.
Don't forget to secure that battery!
What is the alternator output rating? Using an isolator is generally not recommended when charging lithium with a flooded/agm battery. The agm/flooded battery have a very very different charge profile than the lithium battery. They need and can take an extensive absorption phase, where as the lithium only needs about 15 minutes at peak voltage... I'd discontinue the use of the isolator immediately. If you have a programmable alternator regulator, connect the alternator output tot he house bank. If you have a dumb (aka stock) alternator, wire it to the start battery and then use a DC-DC converter to charge the house batt with a lithium profile.
If you wire the externally regulated alternator directly to the house battery, and your shore power 30A charger is also connected to the house battery, then all you need is a small dc-dc charger to charge the start battery from the house batt whenever the voltage is >= 13.8Volts.
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GregI was checking my new Humseink LifePo4 batteries today after the batteries have been on the charger for a few days. Batt 1 showed 100% SOC and Batt 2 showed 99%. Interestingly, the BMS on Batt 1 shut off the charging switch. I assume since it was at 100% and couldn’t accept any more charge. The batteries are paralleled (see photo below).
View attachment 233092
I went out for a 2.5 hour sail today, with a light load on the house bank (fridge, VHF, stereo, CP & instruments).
When I got back, I left the charger off until I could check the BMS for the 2 batteries. Now, Batt 1 still showed 100% SOC and batt 2 was at 86% SOC.
I am not sure why these batteries, if wired in parallel, would not supply power to the house system in equal measure. Instead, it seems that one battery is doing all of the work
View attachment 233093 View attachment 233094
I have written to Humseink to see what they can tell me (if anything). I have discovered that their BMS app will not let me see what the individual cells are doing
So, here is a crude drawing of my DC system (left out the AC side of the equation for now)...and only the house side. Left off the starter battery, switch, charger, etc for that.
View attachment 233095
Does anyone see anything blatantly wrong with this set up (I hope not, as I have sailed with it a few times now). Or could this just an issue with the batteries? One thing I could try is to install a positive and negative bus bars and hook each battery individuslly to the bus bars. But the charger would charge the bus bars (single output charger ). Not sure that changes things much. Does paralleling LFP batteries need to be different than FLA?
On the RV forums I subscribe to, several campers with 2 LiTime batteries were experiencing similar. Basically, one battery was going into "standby" while the other carried the load. There were various "fixes" suggested by LiTime which included taking both batteries to zero, and then resetting. Nobody wants to take LFP batteries to zero for fear of never being able to wake them again, especially on a boat.
Bottom line: it's a BMS software flaw that eagerly shuts down one battery of a parallel combo. I wonder if your battery set is using the same BMS as LiTime.
Solutions:
- download and try Solar Overkill app on your phone. This may allow Bluetooth access to more BMS functions and information. I prefer the Solar Overkill app because I know the software is being maintained. I have a Techcella battery I bought 3 months ago that has disappeared from the market, so I have no hope of the OEM app being updated.
- cell balancing on a regular basis is critical in a parallel environment
- follow factory instructions on recovery. But in LiTime's case the problem reoccurs regularly.
- go to single battery ops, either buying a larger battery or using existing batteries one at a time and switching between them. If you keep 2 batteries at any significant difference in SOC, you CANNOT parallel them.
- I went with a single larger (160AH) battery because in both personal experience and electrical engineering I have learned that paralleling batteries - regardless of type - is inherently unstable because no 2 batteries are perfectly matched. Nobody wants to talk about this until something goes wrong. And there are many, many users of paralleled batteries where nothing has ever gone wrong. In my case it was a battery fire with lead acid batteries (no BMS except me to shut things down). Others have experienced what you are going through.
- I have had many, many people tell me I'm wrong and don't know what I'm talking about. But whenever the voltage is the SLIGHTEST bit different between the 2 batteries, they will try to equalize the voltage, often with tremendous currents depending on wire size, voltage difference, and internal battery resistance. That's why the parallel configuration requires attention to details of wire lengths or placement of bus bars at equal distance from the batteries. And correct fusing. The BMS in an LFP battery is the last line of defense to protect the battery when things go wrong.
Fred W
Thanks. I was looking for something in the literature. I guess it runs at 20 amps (max for my charger).
Greg
Thanks for the tips on the alternate BMS software. I tried a few (I don't think I tried Solar Overkill)..none of the alternates really did much. I will try your favorite tomorrow when I get to the boat.
I did hear from Humseink today on my question. A little confusing but I will separate the 2 batteries and charge them separately for a few days to see if I can get them to within 0.3 volts difference.
I did get both batteries to "contribute" to the load today on my sail, but they are not equalized. When I get to the boat tomorrow, I will see how they charged at how close their SOC's are.
Greg
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Hi Greg Johnson,
Thank you for your order, 1 battery showed 88% SOC and the other was still at 100%, this is normal
1. BMS Priority and Firmware Logic
The battery's Battery Management System (BMS) uses prioritization logic to select which battery is discharged first. Some intelligent BMS systems (commonly found in modular setups) are programmed to cycle the batteries in sequence to achieve the following:
Extend life: Avoid stressing all batteries at the same time
Balance wear and tear: Prioritize batteries with the highest state of charge (SOC) or lowest internal resistance
Typically, when batteries are connected in series or parallel, the battery closest to the load's positive and negative terminals will be consumed first.
This behavior is not standard in parallel systems, but is intentional in “smart” battery design. We use advanced BMS algorithms to manage load distribution based on real-time conditions.
Please try more full charge-discharge circles, and connect two batteries when they are within 0.3V voltage difference.
If the problem persists, we can also send you return label.
For RMA Initiation:
If the battery remains non-functional, please provide:
A photo of the product’s side label (showing the serial number).
Multimeter readings of the current voltage (if available).
We look forward to your response to ensure a swift resolution. Should you require further assistance, do not hesitate to contact us.
The batteries should be charged independently before being placed in service and after winter storage. Using the Victron charger plug it in and let it run until the BMS shuts down the charging. This may take a pretty long time. Don't use or parallel either battery until both are fully charged and the BMS has shut down charging. The SOC may show 99% or 100% while the BMS stays in the charge mode, this is due to both rounding errors and the individual cells not being balanced.
This really isn't an issue with a 2 battery system wired in the manner you have wired yours. It is a problem if both + and - come from the same battery with the second battery attached to the first.
Is the communication between the BMSs on your 2 batteries? I think this is a bunch of hogwash on batteries with internal BMSs especially if there is no communication between the two BMSs. A single external BMS that manages several batteries in a bank may do this, but not independent BMSs without the ability to communicate with the other batteries. On my 3 battery parallel bank the batteries are always in the same state, (charging, discharging, standby) and the charging current is evenly divided between the 3 batteries because the cables are all the same length and they all started independently charged and balanced.
So, take the batteries home, put each of them on the charger and try again. You might want to ask the company how to read the cell voltages. Without being able to read the cell voltages there is no way to confirm the batteries are top balanced.
Thanks Dave,
I did charge them independently before I took them out to the boat. But I will try that again. I don't know if they were both in "Storage" mode when I switched the charger to the other. Maybe that is why I have some difference in the 2 batteries. ..
I bought new cables to parallel the batteries, so they have the exact same cables on the + and - terminals.
The part about the BMS's talking to each other (from Humseink) is the part I find confusing. I was not aware that these 2 batteries would talk to each other and decide which one is providing the juice... and which one is taking it easy. Seemed a bit far-fetched to me.
I will re-balance them again over the next few days (I am probably not bringing them home...but will disconnect one at a time and let the charger do its thing over night for each battery.
I did ask about seeing the cell voltages. They said the APP doesn't do that (yet), but they are working on a new release... so who knows.
I guess I know what you get for $139.
Greg
Greg
The BMS's don't talk to each other. Internally the BMS measures voltages and currents at the battery terminals and compares it to either the total of the cells or the individual cells. But a BMS can detect a mismatched SOC because of the high current (usually short term) as the parallel batteries try to equalize their terminal voltages. Unbalanced cells can also produce mismatched voltages at the battery terminals. That's why parallel batteries can be risky/unstable - physics requires them in the absence of a BMS to equalize the voltage between the 2 batteries. The BMS in many of the cheaper batteries aggressively tries to protect the batteries from this cross-battery equalization by shutting down the output. It's also why cell balancing is pretty important in parallel installations. The good point of the aggressive BMS is that your batteries are well protected. The bad is the battery shutdown when you really want/need it in a marine environment.
In the old days of lead acid and no BMS, when the voltages got different, the good battery would dump charge into the bad battery to equalize the voltage, but nobody knew (or cared) it was happening until the mismatch was severe enough to get parallel cables hot. The energy potential of LFP batteries require a BMS to protect the battery from destructive currents in or out. In the marine situation, the standards committees don't like relying on a BMS of unknown quality for protection, and want fast acting fuses to take charge instead, and to provide audible notification of what is going on. But that is expensive and most DIY installers don't know enough to comply.
A single battery has all the cells in series. In the event of a cell voltage mismatch, the battery loses some capacity, but otherwise functions normally. Cell balancing can prevent this but is not needed nearly as often.
Fred W
I don’t want to hijack @SycloneDriver’s post, but this is AlFP system related, so hopefully not egregious… if I should start a new thread, please comment,
I was checking my new Humseink LifePo4 batteries today after the batteries have been on the charger for a few days. Batt 1 showed 100% SOC and Batt 2 showed 99%. Interestingly, the BMS on Batt 1 shut off the charging switch. I assume since it was at 100% and couldn’t accept any more charge. The batteries are paralleled (see photo below).
View attachment 233092
I went out for a 2.5 hour sail today, with a light load on the house bank (fridge, VHF, stereo, CP & instruments).
When I got back, I left the charger off until I could check the BMS for the 2 batteries. Now, Batt 1 still showed 100% SOC and batt 2 was at 86% SOC.
I am not sure why these batteries, if wired in parallel, would not supply power to the house system in equal measure. Instead, it seems that one battery is doing all of the work
View attachment 233093 View attachment 233094
I have written to Humseink to see what they can tell me (if anything). I have discovered that their BMS app will not let me see what the individual cells are doing
So, here is a crude drawing of my DC system (left out the AC side of the equation for now)...and only the house side. Left off the starter battery, switch, charger, etc for that.
View attachment 233095
Does anyone see anything blatantly wrong with this set up (I hope not, as I have sailed with it a few times now). Or could this just an issue with the batteries? One thing I could try is to install a positive and negative bus bars and hook each battery individuslly to the bus bars. But the charger would charge the bus bars (single output charger ). Not sure that changes things much. Does paralleling LFP batteries need to be different than FLA?
Greg
For overall state of charge considerations, the BMS and shunts built into the batteries, aside from perhaps very high end, are notoriously inaccurate and suffer from manufacturing variances.
You should never have the BMS need to disconnect/shutdown itself from your charger, or in general ever shut anything off, unless there was a problem somewhere else in the system.
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I can turn off charging and discharging. My battery does not have heat. I am not sure what “Forced Hibernation” does.
Greg
It is pretty standard to be able to shutdown charge and discharge circuits on the battery itself. A very handy feature I think for people that work in the trades. Also, that feature is built into the BMS of your battery to do ‘last gasp’ disconnects for a bunch of stuff like overcharging, charging too fast, discharging too fast, too low charge, etc.
These are features of modern LifePO4 batteries that need to be thought of as what they are - to avoid overruns on these newer batteries that have massively more energy density than what we have been accustomed to in the past.
The battery BMS, and any shutoffs/disconnects that it does, is there to provide an ‘at worst’ safety disconnect.
It is not there as a regular regulating device.
If your BMS ***EVER*** has to do anything, your boat was already involved in a situation where other systems have failed.
And in particular, the battery BMS is not there to protect you, your guests, or your boat from not having appropriate fusing. Which for LifePO4 on a 40-footer is typically Class-T per battery, plus the main, and class NH for somewhat larger installs/
These are features of modern LifePO4 batteries that need to be thought of as what they are - to avoid overruns on these newer batteries that have massively more energy density than what we have been accustomed to in the past.
The battery BMS, and any shutoffs/disconnects that it does, is there to provide an ‘at worst’ safety disconnect.
It is not there as a regular regulating device.
If your BMS ***EVER*** has to do anything, your boat was already involved in a situation where other systems have failed.
And in particular, the battery BMS is not there to protect you, your guests, or your boat from not having appropriate fusing. Which for LifePO4 on a 40-footer is typically Class-T per battery, plus the main, and class NH for somewhat larger installs/
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