Fogstar Drift Problems. (1 Viewer)

[Carpmart]

Should have been back to 100% within 15mins I'd have thought (mine only really stop accepting when they are virtually at 100% - not Fogstars though) Any chance one battery might be getting hotter or something silly like that?

It’s a classic internal resistance problem of cells in one of the batteries being higher. The power flows to the path of least resistance, hence one battery (the one with lower IT) charges much quicker, the BMS of the ‘better’ battery then says thanks I don’t need anymore charge and the higher IR battery then charges as quickly as the cells with the higher IR will allow.

 

[AdrianChen]

It would need to be at least an hour charging at 87 amps.

Ah I've misunderstood - "the other battery at 94% charging at 68 amps" thought that meant 6% to go at around 68amps charge....

 

[Lenny HB]

Ah I've misunderstood - "the other battery at 94% charging at 68 amps" thought that meant 6% to go at around 68amps charge....

They got to that state in about ¾ hour then I just left them until both were at 100% didn't keep exact track of time but when they reached 100% it was still quite a while until charge current dropped to zero.

 

[suavecarve]

Two 18650 cells in the same vape!

I realised that part but i just so wanted 2 vapes connected in parallel owing to the amount of Batteryampphobia in the thread. Just made me giggle

 

[Carpmart]

I realised that part but i just so wanted 2 vapes connected in parallel owing to the amount of Batteryampphobia in the thread. Just made me giggle

Sorry to disappoint… I must try harder!

^{_{Subscribers  do not see these advertisements}}

 

[OldAgeTravellers]

Join the club Lenny HB. After my episode of “imbalance” and all the contributions on here I realised that for twelve years I have had no idea whether my two or for the last eight years three LA batteries were balanced or not and I never gave it a thought. But now I can see everything that is going on so I can worry about it. But as has been said above the Lithium batteries are bound to have different internal resistances so will obviously discharge at different rates in the same way LA’s would. It is the amount that was the most startling. I have now come to the view that the BMS’s should be looked at like a fuse. Don’t even think about it, It is there to protect the battery from over charging, over current, low temperature and low soc. Hopefully it will do that with better reliability than the figures it sends us via Bluetooth to the app. Only time and usage will tell. I now only look at the Shunt output because that appears to be far more accurate. Unfortunately only time will tell, at least it seems to be more pessimistic than the readings from the app.

However, I now have a new thing to worry about. I noticed today that with not very much switched on, the shunt was reporting approximately a 10 amp discharge. I checked the output from the solar panels which was only a couple of amps. The only thing that could be producing that draw was the fridge. I continued to watch it for well over an hour and the discharge continued. So I disconnected the S+ signal from the Votronic 350 MPPT, click the fridge lit.
It seems that although I have set the jumpers for lithium the device hasn’t modified its algorithm. It has seen a little bit of sun, and also that the leisure battery is apparently fully charged (if it were LA) at 13.2volts. So, woopie I can run the fridge all day long from the leisure battery until it drops a volt or two. Which is obviously why my 600Ah lithium setup has been reducing so quickly. It obviously doesn’t do it in 30 minute bursts as it does or I thought it does, on lead acid. It obviously sees no variation from 13.2v which would be fully charged on LA and thinks I will keep going. My lithiums were at 50% but of course they do not reduce voltage at all until they falloff a cliff at about 5%. So, the wonderful Votronic MPPT which has saved me a fortune on gas while touring in Spain is not bright enough for a Lithium system. I have searched today for an explanation of the Votronic algorithm but cannot find it. So all I can do now is either disconnect the S+ and use more gas or leave it and run my batteries down if I am only sitting or only doing short distances.OK, I can fit a switch but then I have to think about it.

 

[Lenny HB]

The only thing that could be producing that draw was the fridge. I continued to watch it for well over an hour and the discharge continued. So I disconnected the S+ signal from the Votronic 350 MPPT, click the fridge lit.
It seems that although I have set the jumpers for lithium the device hasn’t modified its algorithm. It has seen a little bit of sun, and also that the leisure battery is apparently fully charged (if it were LA) at 13.2volts. So, woopie I can run the fridge all day long from the leisure battery until it drops a volt or two. Which is obviously why my 600Ah lithium setup has been reducing so quickly

Rather than just a Smart Shunt I bought a BMV 712 for my master plan as it has a programable relay that can be programed in percentage. The idea is to use that to switch the S+ via a timer so the fridge runs in blocks during the day when the batteries are in a healthy state.

 

[Raul]

Nothing to worry about Lenny, bms has wild accuracy from one end to the other. It's not calibrated for low or high load. It may be close or accurate in one end and wild on the oposite. Just trust the shunt for SOC and voltage. When I build a battery, each bms gets calibrated for voltage and amps at 0.15C draw for that given battery. I use a known multimeter that is accurate enough to match the bmv. Why at 0.15C? Because its dead right in the middle of 0.3C the rate that LFP likes and is recommended for long stable life.
Being calibrated in the middle, it will be close at those values, and equal discrepancies at each extremities.
Take bms values with a large pinch of salt, unless you personally calibrate it. Even so the bms ability to stay calibrated depends on its components. I don't worry about it. Just trust the shunt.

 

[Lenny HB]

It’s a classic internal resistance problem of cells in one of the batteries being higher. The power flows to the path of least resistance, hence one battery (the one with lower IT) charges much quicker, the BMS of the ‘better’ battery then says thanks I don’t need anymore charge and the higher IR battery then charges as quickly as the cells with the higher IR will allow.

When I put them on charge one was charging at 43 amps and the other one at 44 amps that would suggest the IR is similar for both batteries.

 

[AdrianChen]

Nothing to worry about Lenny, bms has wild accuracy from one end to the other. It's not calibrated for low or high load. It may be close or accurate in one end and wild on the oposite. Just trust the shunt for SOC and voltage. When I build a battery, each bms gets calibrated for voltage and amps at 0.15C draw for that given battery. I use a known multimeter that is accurate enough to match the bmv. Why at 0.15C? Because its dead right in the middle of 0.3C the rate that LFP likes and is recommended for long stable life.
Being calibrated in the middle, it will be close at those values, and equal discrepancies at each extremities.
Take bms values with a large pinch of salt, unless you personally calibrate it. Even so the bms ability to stay calibrated depends on its components. I don't worry about it. Just trust the shunt.

I know the Smart Shunt calculates SOC counting down from the 100% position as defined in the settings IE a voltage point and tail current for a given time (and over time can drift if these aren't reached regularly), but when do internal BMS's start counting? do you need to hit the OVP from time to time to reset the counter, or is there some other setting in the bms that can be set?

Also although in my Shunt I have set the battery sticker value as their capacity, and given the various different chargers settings (including any voltage drop which DVCC takes care of) I presume I am reaching that capacity, or possibly exceeding it, but I again don't know what capacity a BMS uses (or how it is derived) if their shunts and therefore capacity calcs are possibly only indicative?

My current batts have a BMS for cell protection (and safety) but no bluetooth or heaters, the Victron kit gives me an overall SOC and cuts of charging when cold and, if ever it might occur, limits charging current to 150amps which is well within safe limits for the batteries. So I have to trust the BMS for cell protection, and that it is balancing correctly, and since I have no decline in the capacity I use in practice I assume it is working...

I ask because I am pondering repositioning all my kit as it was installed hurriedly before a trip so could be neater/better, and also because getting to the black tank valve requires removal of the batteries, so thought I might take them from the original battery box and pop them into a new box in the garage (the garage is large and pretty empty). Doing so would allow more/bigger batteries, so contemplating 2 more of what I have: cylindrical cell basic BMS, or changing to what would be almost the same cost (tiny bit more capacity) using Drift Pro's linked to the Cerbo, would the Drift Pro controlling the charging system really be any better?

The third option would be to get a grown up (Off Grid) to build a battery and box that suits the garage, with a known BMS/settings....

So reading all the above posts I am now not sure the extra functionality of the BMS's are actually worthwhile/reliable

^{_{Subscribers  do not see these advertisements}}

 

[bubble63]

From the Fogstar website

Deep Dive: Demystifying the Fogstar Drift Battery Management System

Did you know, we use a JBD Battery Management System (BMS) inside our Fogstar Drift batteries? If you're a battery enthusiast or someone who values precision, stick around as we discuss how your Fogstar Drift BMS operates in a bit more depth

www.fogstar.co.uk

 

[OldAgeTravellers]

Rather than just a Smart Shunt I bought a BMV 712 for my master plan as it has a programable relay that can be programed in percentage. The idea is to use that to switch the S+ via a timer so the fridge runs in blocks during the day when the batteries are in a healthy state.

The BMV702 that I have also has a programmable relay I read, never used it so will have to look it up. But also the CerboGX has a programmable relay which could also do the same job. Not sure how to use it on the Pi-Venus set up, I will have a read. But it could be set to enable S+ say above 90% SOC then disable it at say 80%SOC. I don't see the need for a timer because if there is adequate solar the Fridge would be on between those values. Then wait until the batteries have recharged to 90% before switching on again.
I will have to do a bit of reading.
Disabling the S+ yesterday has allowed the Solar to maintain the batteries SOC.even though I have been using the laptop all day long. But wed had to go back to the Gas kettle much to Judy's dismay as she had grown to like using the electric one.

 

[OldAgeTravellers]

Rather than just a Smart Shunt I bought a BMV 712 for my master plan as it has a programable relay that can be programed in percentage. The idea is to use that to switch the S+ via a timer so the fridge runs in blocks during the day when the batteries are in a healthy state.

It looks like you can use the relay in the MultiPlex Inverter as well, see this video. Or this one could be used to turn a water heater on when the SOC reaches a set value.:

 

[AdrianChen]

The BMV702 that I have also has a programmable relay I read, never used it so will have to look it up. But also the CerboGX has a programmable relay which could also do the same job. Not sure how to use it on the Pi-Venus set up, I will have a read. But it could be set to enable S+ say above 90% SOC then disable it at say 80%SOC. I don't see the need for a timer because if there is adequate solar the Fridge would be on between those values. Then wait until the batteries have recharged to 90% before switching on again.
I will have to do a bit of reading.
Disabling the S+ yesterday has allowed the Solar to maintain the batteries SOC.even though I have been using the laptop all day long. But wed had to go back to the Gas kettle much to Judy's dismay as she had grown to like using the electric one.

Yes I guess using an assistant if you have a multiplus, then if the internal battery monitor is on you could use SOC, or Im sure with node red it would be possible just using the shunt values. To save me thinking about it I'm waiting for Lenny to get it done and post

There was some reason I didn't want to use the monitor in the Multiplus, but can't remember what it was..........

 

[OldAgeTravellers]

Yes I guess using an assistant if you have a multiplus, then if the internal battery monitor is on you could use SOC, or Im sure with node red it would be possible. To save me thinking about it I'm waiting for Lenny to get it done and post

I think you will wait a long time for Lenny HB to get into NodeRed programming.
It's something I want to learn but haven't had the time to dedicate myself to it. I need to give up this retirement lark, as the saying goes; "I don't know how I found the time to go to work!" I want it mainly for HomeAssistant, but it would be useful for the bells and whistles on the GX.

^{_{Subscribers  do not see these advertisements}}

 

[lonnie]

I'm early on in my lithium conversion 'journey' so I'm doing as much research as possible. This thread - which focuses on the differing performance of two or more batteries - leads me to an obvious question, why have two smaller ones instead of one big one? Resilience? Redunancy? Cost? Will need to do more research

 

[AdrianChen]

I'm early on in my lithium conversion 'journey' so I'm doing as much research as possible. This thread - which focuses on the differing performance of two or more batteries - leads me to an obvious question, why have two smaller ones instead of one big one? Resilience? Redunancy? Cost? Will need to do more research

Yes those things, and potentialy the max output from a single battery's BMS, which may be the same as the smaller ones, rather than double.

 

[ChrisL]

I'm early on in my lithium conversion 'journey' so I'm doing as much research as possible. This thread - which focuses on the differing performance of two or more batteries - leads me to an obvious question, why have two smaller ones instead of one big one? Resilience? Redunancy? Cost? Will need to do more research

Space, there may not be sufficient height for one big one, but two smaller ones may fit.

 

[Carpmart]

I jumped in when it was expensive (over three years ago now) and I have three totalling 500A+. if I had my time over, I’d build myself one large battery! TBH, I may still do that!

 

[Raul]

I know the Smart Shunt calculates SOC counting down from the 100% position as defined in the settings IE a voltage point and tail current for a given time (and over time can drift if these aren't reached regularly), but when do internal BMS's start counting? do you need to hit the OVP from time to time to reset the counter, or is there some other setting in the bms that can be set?

Also although in my Shunt I have set the battery sticker value as their capacity, and given the various different chargers settings (including any voltage drop which DVCC takes care of) I presume I am reaching that capacity, or possibly exceeding it, but I again don't know what capacity a BMS uses (or how it is derived) if their shunts and therefore capacity calcs are possibly only indicative?

My current batts have a BMS for cell protection (and safety) but no bluetooth or heaters, the Victron kit gives me an overall SOC and cuts of charging when cold and, if ever it might occur, limits charging current to 150amps which is well within safe limits for the batteries. So I have to trust the BMS for cell protection, and that it is balancing correctly, and since I have no decline in the capacity I use in practice I assume it is working...

I ask because I am pondering repositioning all my kit as it was installed hurriedly before a trip so could be neater/better, and also because getting to the black tank valve requires removal of the batteries, so thought I might take them from the original battery box and pop them into a new box in the garage (the garage is large and pretty empty). Doing so would allow more/bigger batteries, so contemplating 2 more of what I have: cylindrical cell basic BMS, or changing to what would be almost the same cost (tiny bit more capacity) using Drift Pro's linked to the Cerbo, would the Drift Pro controlling the charging system really be any better?

The third option would be to get a grown up (Off Grid) to build a battery and box that suits the garage, with a known BMS/settings....

So reading all the above posts I am now not sure the extra functionality of the BMS's are actually worthwhile/reliable

If you got fogstar batteries will be JBD bms; not a bad bms but basic. It will have to hit cell over voltage to re set to 100%. Most bms do this. Also it will be set for the capacity before use by someone. JK has a function where you set a voltage per cell to reset to 100%. Some do it on pack voltage like seplos V3.
So the idea is to set cell over voltage well below 3.65v to allow it to trigger the reset. I set mine JK at 3.55v and 3.54v recovery. It resets few mins into the absorb/ balancing time. When you build your own, you start with a fresh bms with full access and can tweak values to suit. Saying that, you should never chase 100% SOC, and never worry if bms re sets or not. Spend as little time as possible at high voltage, and use it. In winter I hit 100% SOC maybe every 2-3 months.

^{_{Subscribers  do not see these advertisements}}

 

[OldAgeTravellers]

I'm early on in my lithium conversion 'journey' so I'm doing as much research as possible. This thread - which focuses on the differing performance of two or more batteries - leads me to an obvious question, why have two smaller ones instead of one big one? Resilience? Redunancy? Cost? Will need to do more research

My whole reason for fitting two was Redundancy thereby giving me Resilience. I was heading off for a 90 day tour of Scandinavia where I intended to be off grid for most if not all of the time. Lithium is relatively new and developing fast and I didn't want to experience a battery failure in a country where any replacements would be mega expensive, if I could even find replacements. So two were a good insurance. In fact the system has been fantastic. I only experienced problems latterly as I was only doing a few miles each day, so my batteries were running down. In fact it was my Votronics Solar controller switching the Fridge to 12 volt as it thought my batteries were full because Lithium has a higher resting voltage than lead acid.
So, go for it and Don't forget to use Off Grid Solutions who are members on here and give a generous discount to members if you pre register with them. They also give an amazing amount of help and advice and regularly post answers on here. RogerIvy & nigelivy No connection other than I am just a very satisfied customer.

 

[AdrianChen]

If you got fogstar batteries will be JBD bms; not a bad bms but basic. It will have to hit cell over voltage to re set to 100%. Most bms do this. Also it will be set for the capacity before use by someone. JK has a function where you set a voltage per cell to reset to 100%. Some do it on pack voltage like seplos V3.
So the idea is to set cell over voltage well below 3.65v to allow it to trigger the reset. I set mine JK at 3.55v and 3.54v recovery. It resets few mins into the absorb/ balancing time. When you build your own, you start with a fresh bms with full access and can tweak values to suit. Saying that, you should never chase 100% SOC, and never worry if bms re sets or not. Spend as little time as possible at high voltage, and use it. In winter I hit 100% SOC maybe every 2-3 months.

Thanks - that's very helpful - Option three looking more likely!

 

[Lenny HB]

The BMV702 that I have also has a programmable relay I read, never used it so will have to look it up.

It is only programmable for voltage where as the 712 is programmable with percentage.

There was some reason I didn't want to use the monitor in the Multiplus, but can't remember what it was..........

Me to, I think I decided the BMV712 shunt relay would be a better option & more accurate.

 

[AdrianChen]

It is only programmable for voltage where as the 712 is programmable with percentage.

Me to, I think I decided the BMV712 shunt relay would be a better option & more accurate.

Yes your right accuracy is an issue, it doesn't account for current/loads etc that dont go through it I think.

 

[Raul]

It is only programmable for voltage where as the 712 is programmable with percentage.

Me to, I think I decided the BMV712 shunt relay would be a better option & more accurate.

There are 3 options when you have a GX, multiplus, and bmv. All 3 have relays to be set same as bmv. All 7xx bmv’s with monitors have a relay. My bmv 700 has one at the back of the monitor. The GX as well and multiplus to, and the multiplus relay is the most sophisticated and features loaded. It will be as acurate as the shunt because you set in GX what bat monitor to be used. So it’s not the case that the bmv relay is more accurate. In fact the Multiplus relay is the most used by many as it offers power options, temp, etc. on top of the bmv relay options. You can also program AC 2 out as a relay, ( on multiplus 2), for loads based on power, SOC, voltage etc, similar to virtual switch options.
The AC2 out has a relay/ contractor now on the new board, and can be controlled when to switch on, for hot water or dump load, on a dedicated separate circuit.

^{_{Subscribers  do not see these advertisements}}

 

[OldAgeTravellers]

It is only programmable for voltage where as the 712 is programmable with pecentage.

Me to, I think I decided the BMV712 shunt relay would be a better option & more accurate.

So I will install a relay on the RasPi and use the SOC which is read from the Shunt directly. It seems a shame to lose the S+ AES function which save a great deal of gas when there is a lot of sun. Interesting how moving to Lithium opens up a whole can of worms. Like playing Whack-A-Mole.
It looks like I need to check my Sola panels now as well as we have been getting quite a lot of sun but not a great deal of charge. But they are twelve years old.

 

[RogerIvy]

They got to that state in about ¾ hour then I just left them until both were at 100% didn't keep exact track of time but when they reached 100% it was still quite a while until charge current dropped to zero.

Confirm that was the BMS’s that reported 100% whilst still accepting charge?

And confirm that when they were being discharged the current draw was at least 1A per battery?

 

[RogerIvy]

So I will install a relay on the RasPi and use the SOC which is read from the Shunt directly. It seems a shame to lose the S+ AES function which save a great deal of gas when there is a lot of sun. Interesting how moving to Lithium opens up a whole can of worms. Like playing Whack-A-Mole.
It looks like I need to check my Sola panels now as well as we have been getting quite a lot of sun but not a great deal of charge. But they are twelve years old.

This time of the year has surprisingly low solar yield. You’ll notice hazy skies much of the time. Interestingly, in certain places much of that is caused by vapour trails left by jets.

 

[RogerIvy]

Note that the JBD BMS has a “Cell Full Voltage”. If this is set too low the BMS will reach the voltage and report 100% SOC whereas it could take some time to reach OVP. I like to set my Cell Full Voltage to 0.1v below OVP.

 

[Lenny HB]

Confirm that was the BMS’s that reported 100% whilst still accepting charge?

BMS reporting 100% battery still charging at 5 amps for about 15/20 min then dropping to 0.

And confirm that when they were being discharged the current draw was at least 1A per battery?

Shortly before driving off we were running the air fryer at 125 amps.

Difference appears to come about while charging from the B2B on the way home, taking into account the shunt reading I would say the BMS's were reporting the state of the batteries correctly.

^{_{Subscribers  do not see these advertisements}}