240v Battery Charger for Lithium Upgrade

[Busman]

They make multiple ones, better to use those I think. (for 24 and 48 I mean)

[native pepper]

I reckon its great! We have a few brains in the country who have runs on the board, all trying acheive the same outcome - who have come up with different methods to do it. Pepper, T1, Julian -brilliant minds sticking their worik into the RV side. There are others doing similar things in boating and they have all mostly filtered down from the lunatics in Electric vehicles who really know how to push the boundaries

NP, the rapid switching charging regime is not to replicate balancing, its to turn a taper into digital. The chargers utilized are not capable of transmitting the amperage we need so they are used to switch a number of higher amperage relays. As the (lead acid but not running in that mode) charger senses the battery voltage rising to its required setting then it ramps down the "on" time causing increasingly rapid switching of the relays.
Balancing is another story, T1 sorts that in other ways. (I think)

Could you post more infomation on your balancing choices currently available? If I check ebay for example, I find a zillion Lifepo4 balancers.

Have no idea what "taper into digital" means, isn't electric energy just that. however do understand digital is precise, analogue is variable. Thought the use of lead acid chargers required the need for switching relays, that's why we went for single phase bulk chargers. Using lifepo4 chargers solves all the problems you get using lead acid controllers and lifepo4 seems to love the approach. Went through the relay setup years ago and had so many problems with them, they decided to build a single phase charger and after the active bms failed to cope, made a cell equaliser as they called it. Have a few charge and control setups we tested over the years, well my mate tested, I was just the test bed so to speak and just did what i was told. Except for the cells it never cost me anything and was always told if the cells get destroyed, they would be replaced for free. I use the term balancer, but have always been told, no it's an equaliser. Didn't even bother asking the difference as it would have entailed a long technical physics lesson which is way beyond me.

Just had a look at ebay, there are lots of supposed balancers and most are for aa/aaa setups. The link below looks like the ones we use, but the price has gone up a huge amount, we paid less than $20 for ours, but did buy a lot. Our equalisers balance the cells at any voltage, so the chemistry has no bearing on their operation and every time I check the cells manually, they are all equal.

http://www.ebay.com.au/itm/48V-Solar-Sy ... SwlndZI7cm

It's a breeze to setup an RV with this technology, even I can do it with ease, as consumption is very low compared to a mainstream house. Having been off grid since 1976 and going from flooded car batteries, to flooded 6v cells, to AGM and gel, what I have now on my house, workshop, boat and bus is light years ahead of them all. The difference we get with mppt compared to pwm input is amazing and it means you can use cheap 24v panels, panels in series connections for long runs and not have to worry about the controller coping.

This youtube reflects my relationship with digital and analogue, also a great song that's in our repertoire. Made a disastrous attempt to move the band to a digital system from analogue, the control was much better, but the output awful for a live band. So went back to an analogue setup and even dumped our digital feedback destroyer which took a lot of colour out of the music.
https://www.youtube.com/watch?v=il1Byvn_vMA

[bagmaker]

(first links to music video)
Woohooo! Joe Walsh???! I had every album in the 80s..... wonder where those vinyls are now??

Digitally charging relies on the time of the charge being absorbed by the battery. With lith batts the absorb is quick compared to LA.
So the controller is wanting to charge to (example) 14v. It charges at full amperage until it senses 14v and shuts off. A few zillionths of a second later and the voltage drops as the charge is absorbed into the cell. So the charger turns back on again.
repeat repeat repeat.
Kind of like a flouro light, our eyes see a constant light but in reality its turning on and off 50 times (100?) a second. Strobing so fast we cannot see it.
But put it over a lathe and the appearance can be the chuck has stopped at certain speeds. Which is why flouro lights are not fitted over lathe chucks.

Analog monitors the voltage level and maintains an output to keep that level where its required.
Its probably that ALL chargers now days are digital anyway, they just work too fast for us to note.

Anther analogy is that women are digital and men are anolog, like the song.
Woman arrives at the car. Puts down shopping bag. Sorts through handbag. Gets out keys. Opens door. Puts shopping in. Away she goes.
Man arrives at the car with key in one hand and shopping in other hand. Enters car with shopping bag being dropped in passenger seat and key being inserted simultaneously. Away he goes.

Woman arrives at stop sign. Stops car, looks both ways and continues. Slow and safe
Man arrives at stop sign having looked as he approaches, no need to stop. Faster but illegal and not quite as safe.

Not better or worse particularly, just different.

[T1 Terry]

I could keep debating this for ages but it gets a bit pointless when the basics aren't understood a tech based answer will go straight over the head.
One more try, if NP charges at 60 amps then an active balancer would need to be able to move the 60 amps from the cell that is too high to the cell that is too low to stop a cell voltage run away. Active cell balancers shift possibly 5 amps if the voltage difference is huge purely because of the components used. Basically a capacitor is connected across the high voltage cell, charged to that voltage, then connected to the low voltage cell and the capacity discharges till the voltage between the capacitor and cell are the same, then the process is repeated.
If the high cell is at 3.6v and the low cell is at 3.35v, about as far out of balance as you will see in a battery that isn't in a death spiral, there is only 0.250v difference between the high cell and the low cell. That isn't much of a difference so rapid charging of the capacitor or rapid discharging of the capacitor isn't going to happen.
Next is the amount of electrical energy a capacitor can move each time. A capacitor about the size of a fly spray can could maybe shift about 0.5Ah, but the rate the capacitor can be charged comes into effect, too fast and they explode, so either a capacitor much smaller would be required or a resistor to slow the rate the capacitor charges and discharges. Ultra capacitors are still just fantasy and super capacitors need near zero temps to function at their full capacity at high speed, all to do with resistance and current flow creating heat just like the bar heater for warming your feet, no point in getting more techo than that at the moment. A small capacitor would also be required to fit into the balancer box, can you imagine a fly spray can for each cell looking inconspicuous in the battery box
So this leaves us with a small amount of electrical energy being moved from the high cell to the low cell, that sure isn't going to shift 60 amps from one cell to another while the charger is still running....... basically cell balancing only works relatively slowly and the graph show the voltage run away happens very quickly, it simply can not balance a battery while on a high rate charge at the point a cell voltage run away occurs, physics is physics and no amount of typing will change that.

T1 Terry
For some reason only one graph came out, I'll add the other graph showing a 5 amp cell balancer in action, note how long it takes to get the cells all together, then look at the other graphs to see how quickly they can get out of balance but then return to a near balanced set after a load is applied.

Battery charging 1.JPG

Cell balancer test 1 520Ah at rest..jpg

The blurred bit is actually the monitor recording the balancer each time it removes a bit, the line goes down as the capacitor charges and returns to the unloaded voltage when the charge stops, the low cell records a higher voltage as the capacitor discharges in the cell, then drops back to its rested voltage

[El Gringo]

after the active bms failed to cope, made a cell equaliser as they called it. Have a few charge and control setups we tested over the years, well my mate tested, I was just the test bed so to speak and just did what i was told. Except for the cells it never cost me anything and was always told if the cells get destroyed, they would be replaced for free. I use the term balancer, but have always been told, no it's an equaliser. Didn't even bother asking the difference as it would have entailed a long technical physics lesson which is way beyond me.

Our equalisers balance the cells at any voltage, so the chemistry has no bearing on their operation and every time I check the cells manually, they are all equal.

Hi NP.
I was swapping emails with Bob not long before his accident and he sent me pics of his setup then (was the active BMS he was working on at the time), sounds like things have kept developing quite a bit since.
You say these equalisers work at any voltage - i have to say that sounds like a near perfect system - just wondering though what capacity they can send power to each cell? I would be worried about their capacity to handle a 60A charge, but if they are truly nearly balanced before charge then that probably isn't so much of an issue.

I still haven't done anything about Lithium house batteries as we are parked up beside my dad's house to look after him in his old age, been here over 2 years now, mum died last year but dad's still going OK.
I have followed the subject very closely though and am familiar with T1's approach, i think personally that your equalisers may work well combined with T1's control method, but of course my thoughts may not even be worth 2c.

Cheers,

P.S. BTW you don't understand T1's approach to charging, there is no tapering of charge just bulk till full, similar to yours but not using purpose built equipment.

[T1 Terry]

P.S. BTW you don't understand T1's approach to charging, there is no tapering of charge just bulk till full, similar to yours but not using purpose built equipment.

Two separate sections of control, one is constant voltage until a preset voltage is reached and maintained for 6 mins using PWM control, the same as all controller whether MPPT or PWM use at the voltage sensing phase, all the charging before that is at the max available current stage which isn't constant current as that requires a very big power supply, 300 amps for a 100Ah battery and that just doesn't happen in an RV so a different approach is required. After that 6 min period the voltage drops to 13.8v and charging resumes if the voltage drops below this point as long as the sun stays shining on the solar panels. This control method watches battery terminal voltage.
The separate control section monitors cell voltage watching for a cell to run away to 3.6v, if that doesn't happen then it does nothing, if a cell goes over 3.6v all charging stops for a predetermined period, really relies on the constant load on the battery, when the system resets it looks for a cell voltage over 3.6v, if it sees one then it stops the charging again and the cycle repeats until a cell no longer causes an over voltage alarm. Often the 2 will sort of work together, the cell reaching 3.6v might occur at the very top of the terminal voltage charge control, after a few over voltage trips the main control has already changed to the lower voltage setting so the charging stops before a cell reaches 3.6v.
The often mysterious antics of lithium cells causes a different cell to actually reach the 3.6v at the top end of charging, even within the same charging cycle, sometime that one alarm is all that happens and the cell doesn't run away again, just one of the quirks lithium batteries have. There is a reason but I won't go off the subject to explain it here, just accept that it happens, could a cell balance system actually understand that this is normal and part of the cell self maintenance so don't interrupt the process?

T1 Terry

[exscott]

So looking at your second graph the cell balancing looks to do the job well but then I saw the time scale, I don't suppose 12hr over 13.8v is what you want to do too much. The first one is a bit hard to understand without knowing whats going in and out amp wise for me though it does appear by putting a load on while the cells are the furthest apart there would be a few extra watts coming from the high cell due to the higher volts.
Seeing all these graphs i am starting to think a logger would be handy on any system.

[native pepper]

Hi NP.
I was swapping emails with Bob not long before his accident and he sent me pics of his setup then (was the active BMS he was working on at the time), sounds like things have kept developing quite a bit since.
You say these equalisers work at any voltage - i have to say that sounds like a near perfect system - just wondering though what capacity they can send power to each cell? I would be worried about their capacity to handle a 60A charge, but if they are truly nearly balanced before charge then that probably isn't so much of an issue.

I still haven't done anything about Lithium house batteries as we are parked up beside my dad's house to look after him in his old age, been here over 2 years now, mum died last year but dad's still going OK.
I have followed the subject very closely though and am familiar with T1's approach, i think personally that your equalisers may work well combined with T1's control method, but of course my thoughts may not even be worth 2c.

Cheers,

P.S. BTW you don't understand T1's approach to charging, there is no tapering of charge just bulk till full, similar to yours but not using purpose built equipment.

G'day Bernie, you're right have no idea what Terry's system consists of, or how it works and haven't seen one that he has installed. Other than it uses lead acid charger controllers and switching relays and don't have the expertise to comment on it, can comment on just my system and that's all I do. To me the more knowledge passed around the better for all, can't understand why people don't want to reveal their setup, this technology is still new and little understood by most. Keeping everything closed, does nothing for the future use of lifepo4, just makes it hard for those interested to get a good grip on the technology, so they can use it successfully. I understand the commercial aspect, but if you have a good working simple system why not share it. If you understand business, in the long run it you benefit out of it, there will always be those who don't have a clue, don't want to know and just want it to work in a way they can understand. Spreading knowledge around helps everyone, especially those who like doing thongs themselves and save a bit.

Bob had a number of setups working and had made an equaliser that I was testing when he died, the BMS he was working on I now have and it is sitting in a box along with a couple of others and lots of components. Have no idea what his future plans were as he never told me or anyone, he had lots of notes and drawing, which his daughter now has as she is the technical wis. He'd just turn up or send me something and tell me what to do, then harass me into providing him with a running commentary of the performance.

His approach was, give it to a dummy to test and if it works for them, it will work for anyone. Luckily picked up a lot over time to be able to continue, as his kids have their own lives and haven't heard from them for over a year. Having met the manufacturer of the charge controllers when he was in Aus and the equaliser worked so well with the bulk charger, decided to get some made and use them until someone came up with a better system.

After a couple of years, this is working so well won't change it and all in the buyer group are extremely happy with the outcome. One uses an equaliser on their gel house batteries and is champing at the bit for the next cell buy so they can move to lifepo4, we are waiting for the Aus dollar to rise a bit more so we can make a big buy up and save a heap. But it will probably go down and we will have waited for nothing, but more expense. What amazes me is have some 40amp cells in my workshop that are over 9 years old and a couple of 50amp Bob had which are older, they all still sit at 3.2v, and were checked about a week ago. He gave them to me to store so we could see how long it took for them to start losing charge, how much and at what speed, but they are still fine and have no idea how long it will be before they start to deteriorate.

Terry, to the best of my knowledge and from those who know about lifepo4, unless a cell is faulty they don't go out of balance until approaching their upper capacity. There is a chart Bob had that shows this and why it happens, which I could explain if I knew the right terminology, but it has to do with how the electrons line up and are accepted into the cells, compared to lead acid.

A decent cell line equaliser works all the time, so there's little possibility of it having to transfer 60amps between cells, that would be a ridiculous scenario unless a cell was dead and then it wouldn't accept any charge. Have been an observer when testing cell capacities, cell resilience and ability to handle dead cells in line, a very interesting exercise and one that has given me confidence in this system and using lifepo4.

The difference between cells would be just a few milliamps and easily handled by a cell equaliser. Considering the time my system has been in operation using these equalisers, it works wonderfully well and there's not been a time when any cell is out of balance when charging stops or the pack voltage settles, which takes just a couple of minutes.

[T1 Terry]

So looking at your second graph the cell balancing looks to do the job well but then I saw the time scale, I don't suppose 12hr over 13.8v is what you want to do too much. The first one is a bit hard to understand without knowing whats going in and out amp wise for me though it does appear by putting a load on while the cells are the furthest apart there would be a few extra watts coming from the high cell due to the higher volts.
Seeing all these graphs i am starting to think a logger would be handy on any system.

I now realise a whole section of the post was lost, I'll try again
http://www.ozervnews.com/forum/download ... &mode=view
This is the first graph. From 0 hr on the graph the cells are connected to a cell balancer that claims to move 5 amps. The charger is turned on at a max rate of 40 amps and starts at about the 12hr mark where the graph goes vertical, the charger was set to bulk but immediately dropped into maintenance mode and the charge on/off can be seen by the small spikes as the voltage very slowly increases from 13.5v to 13.55v roughly, the normal hysteresis between target voltage and charge cut, you can see the cells already drifting apart yet the current at this point averaged out must be miniscule, certainly less than 1 amp anyway. At about the 15 hr mark the charger is turned off, at around the 16hr 40 min mark the whole lot as disconnected for the night, there is a sudden drop in all the graph lines just after this point where the logger was plugged back in and logging turned on again, the drop shows the settling over night that is just part of what the cells do all by themselves, no balancer connected. A short time later the charger was again turned on and the same thing happened as the day before, so a 0.5 amp constant current charger was connected after the first charger was disconnected, the line dropping and immediately climbing shows this swap over, all the cell lines are blotted over by the maroon coloured line so you can't see them all drop or rise at the same time.
From here a steady increase in voltage across all the cells yet they remain the same distance apart, the balancer having no effect at this point. The sudden drop is where I tripped over the charger extension lead The voltage in all cells continues until the 13.6v charge cut activates. The charge cut was for an hr while the cell balancer was given time to balance the cells, then the 0.5 amp charge started again, it steadily climbs until the 13.6v is reached and this time the charge cut is roughly 1 min instead of 1 hr. During this very slow charge/stop/charge period it can be seen the cells are still out of balance, they only came closer together because all the cells had dropped below the 100% charged mark, maybe only 0.01% but with lithium cells there is full and not full that can be represented by voltage, the only other time voltage means anything as far is state of charge is at the completely discharged end of the scale.... not 100% of the advertised capacity but 100% of what was actually stored in the cell, two different things that are hard to get the head around unless you abandon any comparative thinking between lead acid and lithium.
The last part is where I would have expected to see the balancer bring all the cells together as there is no charging and the cell voltage is dropping.
Now compare the start of the charging period to the end of the charging period, the cell voltages have ended higher but much further out of balance. Even though the charge rate was very small the balancer that it was claimed could move 5 amps hadn't actually been able to get the cells to even stay together, in actual fact the cell represented by the yellow line has dropped below the average where it was close to the average before the charging/balancing started.... I'll leave the reader to determine the effect seen and what may have caused it.

T1 Terry

Opps: The second graph is the balancer in operation in an expanded time graph with no charger connected. Does the balancer actually improve the cell balance over 19 1/2 hrs or is it just that the cell voltage dropped because there was still some absorption occurring in the high cells resulting in the cell dropping slightly below the 100% full mark because more storage area had come into play..... sort of like getting the last air bubbles out of a water bed so it is full of water only, not a combination of water and air.

[nut17]

I don't get back on this site half often enough !!
In the total absence of any individual cell monitoring, or automated cell balancing electronics in the five and a half years I have been enjoying the delights of LiFePO4 in our caravan, my son has just presented me with this black box with four pairs of wires and a label "Battery Equaliser"

( https://www.aliexpress.com/item/Battery ... 2f5a52c743 )

He assures me that provided my cells are fairly accurately balanced when this device is installed it easily has the capability to keep my four pairs of 300AH cells perfectly balanced He even suggested that I could re set my solar controller charge voltage (bulk & absorption) to 14.4 !! I have been sticking to 13.8v for the last two years.

So Terry, do you think this device will be of any use? I will install it and monitor the results including trying a higher charge voltage. My balancing regime has still been limited to about once every three or four months using a 14.8v charge current and restricting any pairs if cells that are inclined to climb above the others with an old coil ballast resistor clipped across the offending pair of cells. I have three of these resistors set up and can usually complete a top end balance in 15 - 30 minutes.

If this new magic black box works I am going to have to look for a new hobby to while away my time.

Cheers
Chris