Cheap LiFePO4 BMS?

[Tony1]

1 hour ago, Dr Bob said:

 

Tony, I am probably one of the few people with direct experience of what you are doing as I have a very similar system, a hybrid LA/Li set up with B2B's, long wires controlled by a BMV 713 and a BEP switch. I do think you are overcomplicating it a tad! There is two sides to this i) the technical set up and ii) how it is operated in practice. Lets look at these separately.

Firstly the technical bit. For me the first level of control has to be the charge source reducing its input when a set level is reached, rather than the isolation switch activated. You say your first line of defence is the isolation activated when you get to 80% SoC. If you are using solar, then the MPPT will work fine to turn down to float so your isolation switch will never be needed. If you are on the alternator for charge then the B2B's will turn down once the set level is needed. I assume your isolation switch is the BEP. In the 4 years I have operated my system, my BEP has not activated once (on its own). I test it infrequently. For me the first level must not rely on the isolation switch.

You then say you need 3 BMVs. Why are you controlling on SoC? On my BMV, SoC is pretty useless after a couple of weeks since sync. Why not use voltage? My BMV is set to trigger the relay for high voltage at 13.9V. This is an absolute value. My state of charge limit is always the same – when the alternator gets to 13.9v at circa 50A (drops from 120A at start). The SoC reading could be anything. One advantage of using voltage is that the BMV has a high level and low level relay so the one BMV does both. That removes your 2^nd BMV, and also allows your charge sources to shut down rather than relying on the BEP.

The BMV voltage is my second line of defence but as above it is never normally triggered. My third defence is the BMV sounding an audible (just) alarm at 14.0V volts, then a fourth - a cell monitoring device that activates the BEP if an individual cell goes above 3.8V and then a final audible alarm if the whole lot goes over 14.4V. The automated isolation is all via the BEP switch which is a vulnerability in the way Tom's Tyco bipolar relay could fail, but shutting down the charge sources in normal operation has to be the way to do it.

I think though that you have to look at normal operation. I very rarely get anywhere near isolation events. I see 2 modes of operation, moving and stationary. An example from this summers 3 months trip out. In the stationary mode, we are tied up not going anywhere. Our 200Ah of power has gone out overnight (and previous 24hrs) and the BMV is showing -200Ahrs. The sun starts charging, we run the engine for an hour to warm the water (putting circa 100Ahr back in). The sun does the rest and the mppt goes into float at the end of the afternoon. No intervention at all. No B2B running – just straight from the solar to Li's. Lack of sun one day and I run the engine for an extra 30 mins. Never any chance of getting near full charge with the engine. I will turn it off after the time I estimate. If I died in the interim, the BEP would isolate it. In moving mode, we are down -200Ahrs at the start of the day. I know we will be charged enough after circa 60 mins and the B2B will shut down the charge then. In practice though I have given up with the B2B's (2* 60A) as they consume so much power and heat up the boat! …..and I just manually isolate the Li's when the voltage gets to circa 13.8V. If I want it automatic then the B2Bs are fine but I am always watching the instruments as we idle along so spending 10 secs to turn a switch is not a chore. It really is so simple.

Now the solar is loosing its efficiency, when stationary, we just run the engine for 90 mins instead of 60 – but we are a very heavy power user.

I do use 2 BMVs, one on the Li system that does all the controlling and one on the LA system. Both are needed to understand battery health for the two banks.

Anyway, well done on setting up your system. It sounds complicated to the non initiated but it isnt. I would certainly encourage you to move to isolating the charge sources at source and then using voltage to control the BMV rather than SoC in an emergency situation.

 

How do you monitor your system with the 3 BMVs? I have mine wired into a Raspberry Pi which dumps all the data to the Victron server (data 24/7) so can see all of the data from the last year from my armchair.

 

For peeps new on here who dont know me, (who can you trust on the internet these days?)my electrical knowledge is significantly lacking when compared to Nick and Simon (MP) so my system was developed from a 'user' approach rather than a technical approach and one where I could marry 2^nd hand Li's to a new boat where I didnt want to void any warranties – hence the hybrid. I do however consider myself an expert on Li batteries, particularly in their safety as I am director of a company working closely with the aviation industry setting standards (via destruction testing) on their transport on passenger aeroplanes and also developing new technology for early warning of battery failure leading to ignition or explosions (ie during dendrite failure).

 

 

 

 

The challenge was that the Valences I have dont have an internal BMS, and I felt I needed high-voltage and low-voltage disconnects to protect them in the very unlikely event that something ever went wrong with the MPPTs or the B2Bs. So that was why I got two of the BMV712s. 

And as emergency disconnects, they haven't been triggered yet in 18 months of use, apart from the odd test. 

 

The controversial element was the third BMV712 that I use to monitor SOC. At the time I was doing the installing, all the info I was reading described how long the batteries would last, and it was based on different charging regimes- and all of these regimes were measured via SoC. 

The graphs I could see seemed to show that the longest lifespan would be achieved if you cycled the batteries (mostly anyway) between 25-75% on a day to day basis. I decided that 30-80% would still give excellent longevity, so my thoughts were focused on ways that I could make this happen, and I knew a BMV712 could monitor SoC, so I took the plunge and got one to use. 

I didnt stop to consider that that a charge profile set correctly could manage the day-to-day charging just as well.

I had used a charging profile to try to control my A2B charging (from alternator to lithiums via a lead acid), and as you can imagine it didnt work at all.

Not only did the alternator get too hot during the tests, but more worryingly, the A2B let the batteries go to 14.8v and beyond, and in my ignorance I very nearly ruined my batteries.

So after that I was a bit sceptical about how safe it was to rely on any charger to manage the battery voltage safely during charging. I didnt realise that a B2B or MPPT is a totally different beast to an A2B when charging lithiums. 

Plus, I basically had tunnel vision about SoC being the thing to monitor, so I set up this system where the BMV712 tells the MPPTs and the B2Bs to switch off when the SoC gets to the daily target value of 80%. 

I wasnt very clear at the time how much the SoC can drift over a few weeks, but there was one occasion the SoC was so inaccurate that I thought my batteries were up to 80% when  in fact they were at 95%. 

The lesson for me there was that voltage has to be the most reliable guide about the battery state. Unlike SoC it is not a derived/calculated value, and when it gets high, you know you have an issue. Voltage doesn't lie, I guess you could say. 

Having put the SoC management system in, I've left it, and it has a couple of minor advantages, but what I always do when looking at SoC is to also look at voltage.

The voltage and SoC should correspond (taking account of current draw lowering the voltage, and vice versa), so if I see them not corresponding, I know I have an issue with the SoC and it needs recalibrating. 

 

But thats only part of the heath robinson story. Because my domestic alternator is rubbish and cant put out more than 35 amps without overheating (at tickover anyway), I've also ended up with an overly complex winter/engine charging system, that uses no less than four B2Bs in order to drag every possible amp out of both alternators, without overheating them.

As I said, at tickover my domestic alternator can give about 35 amps safely, but if I rev up to 1300 rpm say, it can give an extra 10-15 amps and still stay relatively cool.

So to get this extra power from them, I connected an extra (lower power) B2B to each alternator.

So the process now is that when doing a static engine charge during the winter, I run the engine at 1300rpm, switch on the extra two B2Bs, and I can get a combined 90-95 amps charge from the two alternators, so my charging is completed more quickly.   

All this was to work around the limitations of crappy alternators, but to paraphrase Macbeth, I was so far steeped in B2Bs, that it was easier to carry on with them. 

Four B2Bs is verging on ridiculous, and I'm certainly not going to try and justify it by the extra amps I squeeze out of the alternators. The only thing I can say is that it seemed like a good idea at the time, and it kept me from being on the streets mugging pensioners. 

 

 

 

Edited September 11, 2022 by Tony1

[nicknorman]

On 09/09/2022 at 16:27, Tom and Bex said:

Has anyone else that uses the tyco BDS-A bi-stable relay had problems with it? I've just had a second one fail open circuit (with evidence of overheating). 

 

Only used on the charging side (load side uses a BEP motorised battery switch) and never been switched under load (to my knowledge). Max charging current is around 160a (although we rarely see more than 140a) so it shouldn't be overloaded. I think @nicknorman uses one and can charge at a much high rate than i can! Annoyingly both failures have resulted in blown alternator😡

 

I put the first failure down to poor connection as clear evidence of the connection post and cable overheating with corrosion to the cable. This was probably my fault for reusing old cable and crimped end, and in fairness there were warning signs for several weeks before it failed. All cable replaced with new well made crimps when the relay replaced 6 months ago.

 

No problems until today with sudden failure of all charging when cruising. No prior warning at all, and evidence points to relay itself rather than cable connections. Do I replace with another used one? Or bite the bullet and buy new? Or forget the tyco completely and use something else?

 

Evidence of overheating to internal relay contacts, but no evidence of significant wear, pitting, or corrosion on dismantling.

 

 

I’m glad you posted this because it made me check my system. At the normal charge rate of 90A or so it gets slightly warm, which I don’t think is an issue. But when I whack it up to fast charge from the alternator + travelpower into Combi, I can get a charge current of 240A. Yes the relay does get very hot at that, too hot to touch. Well it is the A terminal that gets very hot. The B terminal doesn’t. Which seems odd. Maybe I need to check the crimping of the 75mm^2 cable end. Anyway, in the mean time I’m not going to use the fast charge mode. One doesn’t really want a sudden disconnect with 240A flowing!

 

And before anyone says “it’s only rated at 190A” that is the rating at 85C ambient. At 23C ambient it is rated at 260A.

[MoominPapa]

15 minutes ago, nicknorman said:

I’m glad you posted this because it made me check my system. At the normal charge rate of 90A or so it gets slightly warm, which I don’t think is an issue. But when I whack it up to fast charge from the alternator + travelpower into Combi, I can get a charge current of 240A. Yes the relay does get very hot at that, too hot to touch. Well it is the A terminal that gets very hot. The B terminal doesn’t. Which seems odd. Maybe I need to check the crimping of the 75mm^2 cable end. Anyway, in the mean time I’m not going to use the fast charge mode. One doesn’t really want a sudden disconnect with 240A flowing!

 

And before anyone says “it’s only rated at 190A” that is the rating at 85C ambient. At 23C ambient it is rated at 260A.

This is useful info for me, as my maximum charge rate is about 70A and maximum sustained discharge rate is lower than that. Looks like I'm in the sweet spot.

 

ETA, I think for new LFePO4  systems, there's a strong argument for 24V or even 48V.

 

MP.

 

 

MP.

Edited September 20, 2022 by MoominPapa

[IanD]

1 hour ago, MoominPapa said:

This is useful info for me, as my maximum charge rate is about 70A and maximum sustained discharge rate is lower than that. Looks like I'm in the sweet spot.

 

ETA, I think for new LFePO4  systems, there's a strong argument for 24V or even 48V.

 

MP.

 

 

MP.

 

24V would be fine for most (new) boats, most or all of the DC electrics can run off 24V and use thinner cables than at 12V, and half the current just makes a lot of things much easier (including 24V alternators). Or a 24V==>12V DC-DC converter is cheap, and allows use of standard 12V DC electrics.

 

Probably not worth going to 48V unless you want *really* high-power (5kW+) electrics (e.g. "gas-free", with a generator) or for an electric/series hybrid boat -- you then need a 48V==>24V (and/or 12V) DC-DC converter for all the DC stuff.

Edited September 20, 2022 by IanD

[Craig Shelley]

Some clean data at last. The same data is plotted on both graphs. Charging was from solar, discharge was from various fixed loads. On the fourth day, charging was stopped due to upper voltage limit being met.

[rusty69]

On 31/05/2022 at 22:47, Ronaldo47 said:

I don't claim to be an expert in lubrication, other than possibly under the definition of "expert"  mentioned by my college professor many years ago: " A person who knows the meaning of one more technical word than you do" !

 

What I know about friction and  lubrication stems mainly from lectures at college half a century ago, which started with the prof saying that the mechanism of friction in general  was poorly understood.

 

What might appear to be a smooth surface is far from flat at the microscopic level, when it will be seen to consist of random peaks and valleys. When two unlubricated surfaces are pressed together, the concentration of force at coinciding random  peaks can fuse them together, which is an explanation for the phenomenon of "stiction" , in which a larger force is required to start something moving from rest, than the force needed to keep it moving. The stiction force is needed to break the welded-together peaks. 

 

When oil is applied to a surface, 

the oil molecules in contact with the surface,  become arranged with one end sticking to the surface and the opposite end directed away from the metal surface like the bristles of a brush. The opposite ends repel each other, so when two oil-coated surfaces get close together, the mutual  repulsion of the oil molecules, which coat the entire surface, including the peaks,  make it hard for the  surfaces to come into physical (and therefore also electrical),  contact, and allow the surfaces to easily slide over each other. 

 

Later, for a work project where I needed to find out information about the electrical properties of greases, I had a meeting with a chemist who was a grease expert, and he told me about how lubricating greases are mixtures of oil and soap, the soap helping to ensure that oil stays put. Vaseline, being a pure hydrocarbon , does not contain soap, and its molecules do not behave like the molecules of oil.  Under pressure, vaseline will readily flow and allow the peaks of the metal surfaces to come into intimate contact. That is why the presence of vaseline does not have an adverse effect on electrical  contact resistance when two metals are urged into contact.

 

The beneficial effect of vaseline in making low-resistance  joints in busbars carrying high currents was discovered in the late 19th century when attempts were made to use cheaper aluminium busbars instead of copper ones. Aluminium metal is highly reactive, and on exposure to air, its surface immediately becomes coated with a layer of non-conducting aluminium oxide.  So attempting to simply bolt two aluminium busbars together will result in a high-resistance joint. It was discovered that, by coating a thick layer of vaseline over  the areas of the busbar where the joint was to be made, filing the joint areas bright through the vaseline with a coarse file, and then bolting the busbars tightly together without cleaning off  the dirty vaseline first, produced excellent low-resistance joints.

 

This jointing  method is described in a book on power engineering published in the late 1920's, the author writing that joints he had inspected  that had been made in this way more than 30 years earlier were still in use, and that the technique could also be used with advantage on copper bus bars where a really low resistance was required.  

 

And that's about the sum of my knowledge as to why, on the one hand,  vaseline is good for making low-resistance electrical joints, while on the other hand,  conventional lubricating grease needs to  be kept well away from them.  I don't suppose the laws of physics have changed that much in the past 50 years!

 

 

 

 

 

Resurrecting this, and this comment in particular as I am about to remake the connection on my battery terminals.

 

Having used my LifePo4's for almost a year now, one 'set' is a little out of balance, so I intend to break it down an re balance the lot. Its possible that as I have quite a lot of connections, and lots of bus bars that one bank was not as clean as it could have been when I assembled it.

 

My very brief reading on the subject suggests that aluminium will begin to oxidise within seconds of cleaning, and so its important to prevent this as soon as possible.

 

Anti oxidisation products are available, but what is recommended, or will vaseline suffice?

 

 

Edited January 5, 2023 by rusty69
spellinggg kindly pointed out by rocket man

[magnetman]

25 minutes ago, rusty69 said:

 

 

Anti oxidation products are available, but what is recommended, or will vaseline suffice?

 

 

Rocket salad. 

[peterboat]

40 minutes ago, rusty69 said:

Resurrecting this, and this comment in particular as I am about to remake the connection on my battery terminals.

 

Having used my LifePo4's for almost a year now, one 'set' is a little out of balance, so I intend to break it down an re balance the lot. Its possible that as I have quite a lot of connections, and lots of bus bars that one bank was not as clean as it could have been when I assembled it.

 

My very brief reading on the subject suggests that aluminium will begin to oxidise within seconds of cleaning, and so its important to prevent this as soon as possible.

 

Anti oxidisation products are available, but what is recommended, or will vaseline suffice?

 

 

I use copper slip, in the hope that the copper helps 

Edited January 5, 2023 by peterboat

[rusty69]

2 minutes ago, peterboat said:

I use copper slip, in the hope that the copper helps 

 

Thanks peterboat. Does it? Its sounds preferable to using salad tbh.

[peterboat]

Just now, rusty69 said:

 

Thanks peterboat. Does it? Its sounds preferable to using salad tbh.

It's designed to stop things seizing but the high copper content has to help make a better connection and the grease keeps air out

[nicknorman]

33 minutes ago, rusty69 said:

Resurrecting this, and this comment in particular as I am about to remake the connection on my battery terminals.

 

Having used my LifePo4's for almost a year now, one 'set' is a little out of balance, so I intend to break it down an re balance the lot. Its possible that as I have quite a lot of connections, and lots of bus bars that one bank was not as clean as it could have been when I assembled it.

 

My very brief reading on the subject suggests that aluminium will begin to oxidise within seconds of cleaning, and so its important to prevent this as soon as possible.

 

Anti oxidation products are available, but what is recommended, or will vaseline suffice?

 

 

 

I put a very thin layer of vaseline on mine. However vaseline does dry out, so it probably isn't ideal. Perhaps the best thing would be graphite grease because it is a bit conductive? Although of course the point is that nearly all the grease gets squeezed out, just leaving a bit in the micro-craters. I had a look at the Nordkyn Design website, he talks about cleaning/abrading the mating surfaces but not about using any product on the surfaces. Of course with Lead Acid, one tended to use grease because of the sulphuric acid vapour, but obviously that is not applicable to Li.

[rusty69]

3 minutes ago, nicknorman said:

 

I put a very thin layer of vaseline on mine. However vaseline does dry out, so it probably isn't ideal. Perhaps the best thing would be graphite grease because it is a bit conductive? Although of course the point is that nearly all the grease gets squeezed out, just leaving a bit in the micro-craters. I had a look at the Nordkyn Design website, he talks about cleaning/abrading the mating surfaces but not about using any product on the surfaces. Of course with Lead Acid, one tended to use grease because of the sulphuric acid vapour, but obviously that is not applicable to Li.

 

Vaseline was my first thought, unless there is something better. Some people suggest this stuff (Piccy), but it doesn't appear to be readily available in the UK. There must be a UK equivalent.I'll look into the graphite grease. Thanks.

[rusty69]

30 minutes ago, peterboat said:

It's designed to stop things seizing but the high copper content has to help make a better connection and the grease keeps air out

I just found half a tin of copper slip in the engine room. Looks like alumslip is also a thing.

[rusty69]

So after many many minutes of research, and the link below, i decided to go for the graphite grease in the end. The main thing I took from the video in the link is to go sparingly with any grease you use as the majority of them are an insulator. The other point he mentioned was that the copper grease on aloominium terminals could cause galvanic corrosion, but I suppose that is a possibility with copper bus bars on aluminium terminals anyway.

 

https://garagedetective.com/battery-terminal-grease/

 

 

Edited to include a spelling error.

Edited January 5, 2023 by rusty69

[Craig Shelley]

Hi,

I'm not sure I'd buy into the greasing of contacts on sealed flat-terminal batteries. As far as I see it, any contamination between the contact points is unwanted.

On conical posts seizing can be a problem, and where there are corrosive vapours a protective barrier to the exposed metal parts is needed.

As far as I'm aware, LiFePO4 shouldn't be producing vapour, and in dry conditions flat surfaces shouldn't be seizing or corroding together.

 

I might be wrong about this, as far as i'm aware, the best dry electrical contact is achieved by maximising the metal to metal contact area. This can be achieved by polishing the two surfaces so that they are as flat as possible. By polishing I just mean working up to 800 or 1200 grit wet and dry paper with a solid block behind it to ensure flatness is obtained. As soon as the finish looks good enough i.e.major imperfections flattened out, wipe it clean to ensure no grit is left behind, and immediately bolt the two surfaces together.

The exception is that if the contacts are plated with nickel and are in brand new condition, sanding can only make the surface finish worse. Nickel naturally plates to a very smooth mirror finish. The lugs on our battery pack are tin plated, which is significantly less durable. As a result, they have needed a bit of work to flatten down the contact area. On the copper terminals it's easier to see where the physical contact between the surfaces has been poor; sometimes evident by the formation of oxide in localised patches. Also where the copper and aluminium contacts, which were previously clamped together, are separated it's sometimes possible to observe an amalgam layer on one of the surfaces - I forget which one.

 

I can fully appreciate why grease is necessary in a variety of other situations e.g. on connectors where the contacts slide together, or any connection point that is regularly connected and disconnected and/or exposed to environmental contamination/corrosion.

 

--

Craig

[Dr Bob]

4 minutes ago, Craig Shelley said:

As far as I'm aware, LiFePO4 shouldn't be producing vapour, and in dry conditions flat surfaces shouldn't be seizing or corroding together.

 

 

Rusty,

being a very qualified muppet, I can exclusively report that when put my LiFePO4 system together (is it that long ago ...4 years?) I used no anti-corrosive stuff at all. The batteries are inside the bote and I've had no issues at all. Over 4 years on, I have a set of batteries that are responding exactly the way they were when i set them up and did the initial balancing work. The balance has remained exactly the same for 3.5 years and the voltage/power out curve is exactly as it was. I reckon they will be the same in 2033 (I might not be!).

Mind you, it is Friday 13th next week which also happens to be Mrs Bob's birthday. Any ideas for a pressy?

 

Maybe Craig is right. Do you need it?

 

All the discussion on Li's vs lead acids on her back in 2018/19/20. Its a no brainer. Its been great sitting on the bleeding edge .......and never fell off.

 

 

[rusty69]

10 minutes ago, Dr Bob said:

Rusty,

being a very qualified muppet, I can exclusively report that when put my LiFePO4 system together (is it that long ago ...4 years?) I used no anti-corrosive stuff at all. The batteries are inside the bote and I've had no issues at all. Over 4 years on, I have a set of batteries that are responding exactly the way they were when i set them up and did the initial balancing work. The balance has remained exactly the same for 3.5 years and the voltage/power out curve is exactly as it was. I reckon they will be the same in 2033 (I might not be!).

Mind you, it is Friday 13th next week which also happens to be Mrs Bob's birthday. Any ideas for a pressy?

 

Maybe Craig is right. Do you need it?

 

All the discussion on Li's vs lead acids on her back in 2018/19/20. Its a no brainer. Its been great sitting on the bleeding edge .......and never fell off.

 

 

Ah, Dr Bob. The difference may be, that my cells don't remain totally condensation free, and I may not have balanced one set as well as I might have. 

 

I am addressing both of these issues, but for the want of a bit of 'product ', it seems silly not to apply some if I'm going to strip them down. 

 

As for the present. Yes, I suggest you upgrade Mrs B's hand cranked singer for one of those electrically powered new ones now you have the amps to spare. 

 

How's the duck BTW. Did you eat it at Christmas? 

Edited January 5, 2023 by rusty69

[magnetman]

Speculation and not intended to be real:

 

Maybe the Winston Thundersky cells rusty got were taken from dismantled Mastervolt MLI batteries where the BMS had knocked the voltage down over time, cut the batteries out and made the units a bit awkward to sell. I was offered a couple of these Mastervolt batteries by someone in the waste management trade a while ago. New boxed Mastervolt batteries but they had discharged to below BMS cutout and for some reason sent to the recycling man. Quite big batteries they were. Doing some research I found that they had Winston cells in them.The yellow ones.

 

https://pbase.com/mainecruising/mastervolt_lifepo4_autopsy

 

They could have been ever so slightly different from the start of proceedings if they had been previously discharged to the BMS LVC cutout then recharged.

 

Not saying this is what happened but it isn't implausible at least to me.

 

Manual balancing of individual cells and very clean terminals seems to be the right thing.

 

 

Edited January 5, 2023 by magnetman

[rusty69]

1 minute ago, magnetman said:

Speculation and not intended to be real:

 

Maybe the Winston Thundersky cells rusty got were taken from dismantled Mastervolt MLI batteries where the BMS had knocked the voltage down over time, cut the batteries out and made the units a bit awjward to sell. I wlas offered a couple of these Mastervolt batteries by someone in the waste management trade a while ago. New boxed Mastervolt batteries but they had discharged to below BMS cutout and for some reason sent to the recycling man. Quite big batteries they were. Doing some research I found that they had Winston cells in them.The yellow ones.

 

https://pbase.com/mainecruising/mastervolt_lifepo4_autopsy

 

They could have been ever so slightly different from the start of proceedings if they had been previously discharged to the BMS LVC cutout then recharged.

 

Not saying this is what happened but it isn't implausible at least to me.

 

Manual balancing of individual cells and very clean terminals seems to be the right thing.

 

 

Possibly, but I did measure all for voltage and resistance when I bought them. I seem to recall all voltages were within +/- 0.01v. 

[magnetman]

5 minutes ago, rusty69 said:

Possibly, but I did measure all for voltage and resistance when I bought them. I seem to recall all voltages were within +/- 0.01v. 

 

Cleanliness is probably next to godliness in this situation. Do you have a charger which can do individual cells? There is a RC plane battery charger which can be set to very precise voltages but I cant remember which one it is. i or X something I think it was.

 

ETA I'm getting worried about my own spelling errors now! Some sort of MCI creeping in. Oh dear.

Edited January 5, 2023 by magnetman
edit for spelling error

[rusty69]

1 minute ago, magnetman said:

 

Cleanliness is probably next to godliness in this situation. Do you have a charger which can do individual cells? There is a RC plane battery charger which can be set to very precise voltages but I cant remember which one it is. i or X something I think it was.

I have a bench power supply. I recall charging them as a 12v bank until the BMS cut out and then disconnecting and top balancing at 3.6/3.65. However, one set of 7 has always been a bit off, so it may simply be a bad or dirty connection. 

[magnetman]

Just now, rusty69 said:

I have a bench power supply. I recall charging them as a 12v bank until the BMS cut out and then disconnecting and top balancing at 3.6/3.65. However, one set of 7 has always been a bit off, so it may simply be a bad or dirty connection. 

 

Batteries are a lot less important than brain cells.

 

Hopefully you can sort it out by cleaning.

[rusty69]

Just now, magnetman said:

 

Batteries are a lot less important than brain cells.

 

Hopefully you can sort it out by cleaning.

Here is a screenshot from today. For your brain cells 

[magnetman]

Are traffic lights red orange and white in China?

[rusty69]

1 minute ago, magnetman said:

Are traffic lights red orange and white in China?

Just red I think.