Voltage drop with BattleBorn batteries

[Mike Lewis]

This title might get the attention of some of you. Earlier in the year I expanded my BattleBorn system from two to four batteries when I was informed that the system had to be completed within two years. Currently I am on a 3-4 month trip that is serving as a shakedown cruise for this new battery configuration.

After two cloudy / rainy / stormy days in Wisconsin I was startled to hear my inverter whining. I checked the Victron app to find that my state of charge had dropped to 67%, no surprise there, but the voltage had dropped to 10.7 volts. I thought these things were supposed to maintain 13+ volts output until they got very low, like five or ten percent charge. What am I missing?

Re the photo: since taking the photo I've changed the battery-to-shunt connection from Battery #1 to Battery #4, in case anyone notices.

Did I not upload the photo? Well, crap. Here it is:

[M_canada]

At 60% SOC, my 3 BattleBorn are around 13.1-13.2V. What was the current draw when it was 10.7V?

[Centex]

Hard to tell for sure from the pic but are you pulling your (+)cable to charger/loads and your (-)cable to charger/ground both off of 'battery 1' terminals?

I'm not sure that would contribute to the phenomenon observed, but if the answer is Yes you might try moving one of those to the corresponding terminal on 'battery 4' in the parallel array after re-charging each individual battery to as near identical an SOC as you can, and see what behavior you get over time having done that.

Current is pervasive in the 'buss' of the interconnecting cables but it also takes the path of least resistance; there's an ongoing slight difference in the resistance from battery 4 to battery 1 if both legs of the circuit are terminated at battery 1. That might lead to an increasingly imbalanced SOC among the batteries in the array over a period of time, causing issues. Connecting the charger/load cables at opposite ends of the parallel array will minimize that effect.

EDIT - I just/finally comprehended your "Re: the photo ..." note ; did you recharge each individual battery to a near-identical SOC when you made that change?

[Brian B-P]

Originally Posted by Mike Lewis

After two cloudy / rainy / stormy days in Wisconsin I was startled to hear my inverter whining. I checked the Victron app to find that my state of charge had dropped to 67%, no surprise there, but the voltage had dropped to 10.7 volts. I thought these things were supposed to maintain 13+ volts output until they got very low, like five or ten percent charge. What am I missing?

These lithium-ion units consist of four LiFePO4 (LFP) cells, with a nominal voltage of 3.2 V/cell, or 12.8 V nominal for the battery... which means that an average over the whole usable range of state of charge will be about 12.8 V, while there is no current draw. More than 13 V is more than 3.25 V/cell, which is more than half-charged. By 10% the battery voltage will likely be down to 3.1 V/cell (12.5 V total) or less, and by 5% it's useless.

Voltage drops quickly from the "absolutely stuffed" level to something like 13.2 V (for four cells), then loses less than a volt over the whole range from fully charged to roughly 10% charge left... then falls of a cliff. And that's at zero current: at 1 C (current to discharge nominal capacity over one hour, or about 100 A for a 100 Ah battery) the voltage will sag by perhaps about another volt, compared to what it would be at the same state of charge with no current flowing.

(from RELiON battery)

You're never going to see 13+V over the whole usable range. Staying over 11 V even with high current all the way down to 20% SoC seems like a reasonable expectation.

10.7 V is still really low for a battery voltage, especially at 67% SoC. Was that measured at the battery, or at the inverter input terminals, or somewhere in-between? If the battery voltage is fine but the inverter is screaming because it is seeing two volts less than there is at the battery terminals, you don't have battery voltage sag, you have too much wiring resistance (including at connections).

[rubicon327]

Mike: FWIW when I was testing my 400AH Bestgo lithium off the inverter on Friday I started with 13.28V (95% SOC) at the battery. When I pulled 104A initially I saw 12.88V at the battery and 12.5V at the Xantrex inverter. About 2.5 hours later (~65% SOC) I caught the mini-split dialed down and battery read 13.14V and inverter read 13V drawing 3A. At about 50% SOC I read 12.83V at the battery and 12.5V at the inverter when drawing 78A. At about 30% SOC when I concluded my test I was drawing 77A and saw 12.68V at the battery and12.5V at the inverter. My Victron BMV battery monitor read very close to the direct battery readings during the entire test. My point here is that seeing 10.7V even under high load is way too low with your impressive setup.

I would call BattleBorn and talk through some troubleshooting. Is it possible you have a bad bad connection somewhere or a bad battery?

[alanmalk]

Originally Posted by Mike Lewis

...
I checked the Victron app to find that my state of charge had dropped to 67%, no surprise there, but the voltage had dropped to 10.7 volts.
...

Here's a thought:
Assuming that the Victron is calculating the SOC by integrating samples across the shunt - what if one cell went bad and the remaining batteries were trying to recharge the bad cell? None of this "lost" current would be flowing across the shunt and therefore the calculation of 67% would be wildly inaccurate.

Sounds like you might have to disconnect individual batteries and take voltage readings.

[dstreight]

I was wondering about the balancing between the batteries & cells. I remember reading a couple years ago BB had a few BMS failures. But they were good about replacing ala their warranty.

[Mike Lewis]

More info:

- Right after posting the start of this thread last night my system shut down completely. I closed my propane tanks as I had no propane alarm, had a cussfit, and went to bed. Goodbye food in the fridge (fridge is snickering).

- All negative connections back to the battery bank go through the shunt, in my case a Victron SmartShunt. There are two connections to the "load" side of the shunt: a big cable from the inverter and a cable leading to a small bus, on which negative connections from my trailer system, ham radio, etc., go. From that bus it goes to the shunt.

- I am starting the fourth week of my current trip. The first week I was on electric service most or all of the time. The second week I was in Oshkosh on battery power, which seemed to work flawlessly. The third week I was in my current location in Wisconsin, again on battery power. Today I am moving to a site with electric service and will be there for a week.

- I had anomalous behavior from my ham radio a few days ago and investigated. I saw that the nut had come off the stud on the small negative bus, and wires from the trailer system and the radio had come loose. Somehow the batteries still worked, so I guess the negative current passed through the inverter cable back to the shunt. This incident is probably the cause of my problem.

- Each battery is protected by an MRBF fuse. I haven't checked them yet. They are arranged so that if one fuse blows it doesn't take out the entire battery bank.

- I have installed the Progressive Dynamics charger, so I'm assuming that when I have electric service again it will charge all of the batteries evenly, assuming my fuses are good (I'll check them later). Then I will go through some diagnostics you have suggested.

- I don't trust my SmartShunt. Although I have it set up for a 400 Ah battery bank and otherwise used the settings BattleBorn suggested, it tells me that my batteries are fully charged before noon every day. I have 355W of solar on the roof. I am skeptical. For instance, right now it says my batteries are at 100%. Bull!

Please continue to comment. I appreciate the help.

[M_canada]

Originally Posted by Mike Lewis

More info:

- Right after posting the start of this thread last night my system shut down completely. I closed my propane tanks as I had no propane alarm, had a cussfit, and went to bed. Goodbye food in the fridge (fridge is snickering).

- All negative connections back to the battery bank go through the shunt, in my case a Victron SmartShunt. There are two connections to the "load" side of the shunt: a big cable from the inverter and a cable leading to a small bus, on which negative connections from my trailer system, ham radio, etc., go. From that bus it goes to the shunt.

- I am starting the fourth week of my current trip. The first week I was on electric service most or all of the time. The second week I was in Oshkosh on battery power, which seemed to work flawlessly. The third week I was in my current location in Wisconsin, again on battery power. Today I am moving to a site with electric service and will be there for a week.

- I had anomalous behavior from my ham radio a few days ago and investigated. I saw that the nut had come off the stud on the small negative bus, and wires from the trailer system and the radio had come loose. Somehow the batteries still worked, so I guess the negative current passed through the inverter cable back to the shunt. This incident is probably the cause of my problem.

- Each battery is protected by an MRBF fuse. I haven't checked them yet. They are arranged so that if one fuse blows it doesn't take out the entire battery bank.

- I have installed the Progressive Dynamics charger, so I'm assuming that when I have electric service again it will charge all of the batteries evenly, assuming my fuses are good (I'll check them later). Then I will go through some diagnostics you have suggested.

- I don't trust my SmartShunt. Although I have it set up for a 400 Ah battery bank and otherwise used the settings BattleBorn suggested, it tells me that my batteries are fully charged before noon every day. I have 355W of solar on the roof. I am skeptical. For instance, right now it says my batteries are at 100%. Bull!

Please continue to comment. I appreciate the help.

Yes, something seems up with the SmartShunt. A deficit of 40% of 400Ah is about 160Ah which is about 2000Wh. That will take much more than a morning to restore from 355W of solar.

[splitting_lanes]

Would it be feasible to try running on two of the batteries for a period of time and then switch to the other two? It’s just a way to narrow down a battery issue, and if you don’t see an issue with either pair, it could point to a wiring issue.

Measuring voltage across each battery when disconnected is a great suggestion, they should be very similar, especially after a charge.

[Mike Lewis]

I let my batteries charge from shore power for a good 30+ hours, then disconnected shore power and shut off the batteries. I isolated the batteries from each other and took voltage readings. All four read either 14.38V or 14.39V.

I tested each MRBF battery terminal fuse, the fuses for the solar controller and the B2B charger, and the circuit breaker for the solar panels using a continuity tester. All are good.


I reconnected everything and made sure all connections are tight. I put a lockwasher on the negative bus bar stud that connects the trailer system negative.

That's it so far. I'll be on shore power a few more days as it's warm and humid at my location. Then when I'm on battery power again I'll keep a close eye on things.

[dstreight]

How long did you wait after disconnecting them from the charger before taking a voltage reading?

[sumac.rhus]

I know next to nothing about electricity...but could your battery profile selection have accidentally switched, messing with balancing and topping off?

[Sean Murry]

Originally Posted by Mike Lewis

More info:

- Right after posting the start of this thread last night my system shut down completely. I closed my propane tanks as I had no propane alarm, had a cussfit, and went to bed. Goodbye food in the fridge (fridge is snickering).

- All negative connections back to the battery bank go through the shunt, in my case a Victron SmartShunt. There are two connections to the "load" side of the shunt: a big cable from the inverter and a cable leading to a small bus, on which negative connections from my trailer system, ham radio, etc., go. From that bus it goes to the shunt.

- I am starting the fourth week of my current trip. The first week I was on electric service most or all of the time. The second week I was in Oshkosh on battery power, which seemed to work flawlessly. The third week I was in my current location in Wisconsin, again on battery power. Today I am moving to a site with electric service and will be there for a week.

- I had anomalous behavior from my ham radio a few days ago and investigated. I saw that the nut had come off the stud on the small negative bus, and wires from the trailer system and the radio had come loose. Somehow the batteries still worked, so I guess the negative current passed through the inverter cable back to the shunt. This incident is probably the cause of my problem.

- Each battery is protected by an MRBF fuse. I haven't checked them yet. They are arranged so that if one fuse blows it doesn't take out the entire battery bank.

- I have installed the Progressive Dynamics charger, so I'm assuming that when I have electric service again it will charge all of the batteries evenly, assuming my fuses are good (I'll check them later). Then I will go through some diagnostics you have suggested.

- I don't trust my SmartShunt. Although I have it set up for a 400 Ah battery bank and otherwise used the settings BattleBorn suggested, it tells me that my batteries are fully charged before noon every day. I have 355W of solar on the roof. I am skeptical. For instance, right now it says my batteries are at 100%. Bull!

Please continue to comment. I appreciate the help.

I have pretty much the same set up. 4x100A Battle Born Lithium batteries with the Victron battery monitor. I set up the monitor with the values BattleBorn suggested. Put in 400A etc. etc.
My battery monitor will never get below 99% state of charge. However the voltage readings seem to be accurate. I used the monitor for the voltage readout, then compare that to a chart giving the state of charge for lithium based on various voltages.
Would be nice to be able to simply read the state of charge on the monitor, but it just doesn't seem to want to cooperate

[rubicon327]

Originally Posted by Sean Murry

My battery monitor will never get below 99% state of charge. However the voltage readings seem to be accurate. I used the monitor for the voltage readout, then compare that to a chart giving the state of charge for lithium based on various voltages.
Would be nice to be able to simply read the state of charge on the monitor, but it just doesn't seem to want to cooperate

I would give Victron a call to help troubleshoot. I wonder if a factory reset might be in order or a firmware update. I think they'll be able to get it straightened out for you.

Recently installed the BMV-712 Smart and love it.

[Mike Lewis]

Originally Posted by dstreight

How long did you wait after disconnecting them from the charger before taking a voltage reading?

I disconnected from all power, then I had to physically disconnect two terminals on the negative side of the battery bank then two terminals on the positive side. Add in my usual fumbling and cussing and I'd say about thirty minutes before I measured the voltage.

[Mike Lewis]

Originally Posted by Sean Murry

I have pretty much the same set up. 4x100A Battle Born Lithium batteries with the Victron battery monitor. I set up the monitor with the values BattleBorn suggested. Put in 400A etc. etc.
My battery monitor will never get below 99% state of charge. However the voltage readings seem to be accurate. I used the monitor for the voltage readout, then compare that to a chart giving the state of charge for lithium based on various voltages.
Would be nice to be able to simply read the state of charge on the monitor, but it just doesn't seem to want to cooperate

I noticed that from the beginning the SmartShunt indicated that the batteries were charging quickly, before noon every day. I left the trailer on battery power at home for several weeks before departing on my current trip and they never drained down more than 30% or so. I figured that the batteries have to charge cycle a few times for the monitor to calibrate, but with 400 Ah that is a challenge. The "history" feature on the SmartShunt app shows only two cycles but 19 "synchronizations", whatever that is. Time to read the fine manual again.

[RangerMan]

Originally Posted by Mike Lewis

I noticed that from the beginning the SmartShunt indicated that the batteries were charging quickly, before noon every day. I left the trailer on battery power at home for several weeks before departing on my current trip and they never drained down more than 30% or so. I figured that the batteries have to charge cycle a few times for the monitor to calibrate, but with 400 Ah that is a challenge. The "history" feature on the SmartShunt app shows only two cycles but 19 "synchronizations", whatever that is. Time to read the fine manual again.

When it syncs it set some parameters, such as amp hours back to 0. It syncs when the battery(s) are back to full charge. You can also do a manual sync.

[Perry Butler]

Originally Posted by Mike Lewis

I noticed that from the beginning the SmartShunt indicated that the batteries were charging quickly, before noon every day. I left the trailer on battery power at home for several weeks before departing on my current trip and they never drained down more than 30% or so. I figured that the batteries have to charge cycle a few times for the monitor to calibrate, but with 400 Ah that is a challenge. The "history" feature on the SmartShunt app shows only two cycles but 19 "synchronizations", whatever that is. Time to read the fine manual again.

I installed a 712 to monitor our batteries in 2019 after the first set of AGM's died after only three months. One of fhe first things I noticed was the Victron BMV 712 would claim 100%, but the GoPower only claimed 90%. After a couple of years and talking to a couple of others who noticed the same 100%/90% it became apparent the batteries were not at 100% despite what the Victron claimed. I can read my 712 while driving down the road with our 5.0. Our controller is set for 14.6v for bulk and 14.6 for absorption.

Today I was watching the phone app while driving down the road on a low-use four lane highway. The second the Victron 100/30 showed 14.6 it went into absorption, and when I switched to looking at the 712 it showed 100% charged. LOL! I know it's not truly at 100% charge, but I bought the 712 to check battery health, not find out when my batteries are 100% charged. In addition, I have our Victron BMV-712, 100/20, and 100/30 all interfaced with each other. While the GoPower controller charged my batteries just as fast, it was a dumb unit, and provided no other details to monitor the health of my batteries. It's just a cheap controller, but it will charge the batteries quite well.

Because of the death of two sets of AGM batteries I decided to pull the fuses on our WFCO charger. I've read where the WFCO can go haywire and decide to over-volt the batteries. A couple of months ago I started learning more about the 712 and realized in the 712's data at some point the batteries saw 21 amps going in. That is probably what killed our two sets of batteries. As long as everything is going right and you have enough panels the GoPower controller is just fine, but once you encounter problems it helps to have historical data to try to find the problem.

On another note, according to my Victron BMV-712 manual:

A charge cycle is counted every time the state-of-charge drops below 65%, then rises above 90%.

Apparently you've only taken your batteries below 65% twice, thus you only have two cycles. I wonder what other companies consider a cycle?

Food for thought,

Perry

[Rossue]

This is why many van builders- myself included- are going with Goal Zero(have a 3000x) or Bluetti "Solar Generators". They perform. The new Bluetti being released soon is expandable as well. Having bought my GZ from REI I have a year to return it. The half life of these devices is growing shorter by the month.

No way would I wire up 3-4 BB batteries with an inverter and DC plugs and feel safe. I realize adding them to an existing system is perhaps a bit less complicated, yet this thread illustrates that even then problems can arise. Hope you get it resolved Mike.