240v Battery Charger for Lithium Upgrade

[T1 Terry]

I have 2 of those equalizer's on a 24 volt pack and I agree with NP the longer they are there the better they seem to work. Just had a look and my pack is at 47% and within 4 ml volt which it would never do before

Anything less than 100% or more than completely discharged will always be within a few milli volts, there is something seriously wrong that a balancer won't fix if this is not the case. The out of balance occurs most often in a house battery type system when the cells are very close to fully charged. That is not always the same as the battery monitor reading 100% SOC, there is a reason for this but far to detailed to go into here. Even a cell reading of 3.45v might not mean the cell is fully charged. but at least it is close to it, memory charging effect is the reason for this problem and even more complicated to explain here so I won't even try
A cell is truly fully charged when it will not accept any further current without the voltage rising rapidly and continuing to climb at roughly the same rate. With this as a base, the first cell to reach this point will then see a rapid voltage increase yet the cells that have not reached this point will still be accepting all the current they can get without increasing their voltage..... this is what we refer to as a cell run away. Unless the balancer device can move the amount of current the whole battery is receiving via the charger (solar, mains or DC to DC) from this already full cell to the other cells the full cell will suffer a voltage run away, if there is no other device in place to monitor this cell voltage run away and stop the charging before that cell's voltage exceeds the safe boundaries that cell will be irreparably damaged. The level of damage depends how long it is held at an unsafe voltage, just how high that voltage reaches and just how much current is involved.... and how many times it happens. It does not result in instantaneous destruction of the cell, that requires a lot of abuse, but it does result in death by a thousand cuts and each cut won't heal.
The practice of lowering the battery end of charge voltage on the premise it will stop a cell reaching the run away voltage point only results in delaying the inevitable and introducing a greater level of memory charging effect resulting in a gradual reduction in stored capacity. This can be recovered, but again, not something I'll go into here.

T1 Terry

[T1 Terry]

My battery consists of 8x 300AH cells configured into 4 pairs. These cells were three years old when I purchased them and had comprised half of an "off grid" house battery bank. I should have purchased all 16 cells at the time as they were a bargain at $NZ312 per cell.

When performing a top end balance I have one pair (same pair each time) that can be 0.25v lower than the other three pairs. I correct this by applying a resistance over the three lower pairs until the low set catch up or get slightly higher. This is necessary every two - three months. I am using three automotive coil ballast resistors hooked up with alligator clips to easily apply the load to individual cells.
IMG_1648 (Medium).JPG I put this issue down to the poor maintenance that these cells were subjected to in their previous installation. They are still in daily use and seldom get taken below 75% SOC = 450 AH remaining.

My plan is to get the bank perfectly balanced and then install the new magic black box in the hope that it will gently massage the charging process and keep on top of the gradual minuscule drop off of the offending pair of cells. The daily current adjustment would barely be measurable. I certainly would not expect it to magically balance up a set of cells that were significantly out of balance.

Cheers
Chris

IMG_1645 (Medium).JPG

We use a small single cell charger to bring the low cell up when/if needed. It puts out 4 amps flat out but that tapers back to milli amps and then nothing by the time it finally reaches 3.7v.... but you would need to leave it connected for days to reach the 3.7v point. We recommend the balance should not be commenced until the battery is more than 150mV out of balance when fully charged, the same cell group (highest cell) has been recorded as tripping the 3.6v charge cut 3 days in a row and the same cell group (lowest cell) has been the low cell for those 3 days. When the pack is again fully charged, then and only then, connect the single cell charger power by either mains or an inverter to the positive and negative of the low cell group and bring that group up to the same voltage as the high cell.... while the system remains connected and charging via the normal method.
The idea is the total battery voltage should reach the point the charger stop before any cell group reaches 3.6v. By charging the lowest cell group the total should again reach the charger cut off point before a cell group reaches 3.6v. As long as the no cell reaches 3.6v before the charger reaches its cut off voltage all is well and you don't need to do anything.
The reason for the 3 day recording is to ensure there actually is an out of balance problem and not just a cell group clearing a charge memory problem or just going through one of those strange unexplained things that these cell do. I have a lot of recoded graphs where a cell group will initially jump to 3.6v causing a charge cut only to later in the same day become the low cell group and another cell group become the high one. the next day is like none of that ever happened.

T1 Terry

[native pepper]

I disagree about dedicated LiFePo4 chargers, I recently had a lot of correspondence with the Winston factory regarding an import and they do not agree that you need dedicated chargers, they did say that was the thinking early on, but it has been proven to not be so.
William

Have yet to come across a manufacturer, supplier or installer that doesn't swear by their methods William. Have yet to see any form of testing over a 5-10 year period that supports lead acid manufacturers claims regarding lifepo4 longevity. Lithium manufacturers and suppliers, have a vested interest in return sales. There are very few commodities today which don't have a built in time line redundancy and failure, today everything revolves around consumerism turnover, not reliability or long life spans. for their business model to succeed, they need return sales methods built into what they sell and with lithium, it's the charge regimes and upper lower voltage parameters which provide that for them, using expensive lead acid chargers. When all you need is a simple one stage charger that will switch off at 14 and stops supply at 12v. Then you are in the really safe zone of lifepo4 use and will get good long term service out of them.

If my understanding is correct and people stick to using lead acid charging regimes, we will see many lifepo4 systems losing capacity and dying as they get close to 10 years old. Two of my packs are at that age now and they have lost nothing, according to my gauges and fluke. Using lead acid float etc, means your pack will take much longer to fully charge, whilst a lfeipo4 bulk charger will pump in all the amps until the pack reaches 14v and then completely stop charging. So you can get a real full charge long before a lead acid charger dribbling in amps and wasting heaps of energy.

I'm still waiting and looking for the drop in capacity after 10 years of daily house use predicted by some experts, who claimed the approach I've adopted will ruin the cells. None could explain to me how or why that would occur as the cells never get into the upper or lower charge limits they recommend, all they would say is they know what they are doing and I don't.

But my knowledge comes from someone who dedicated more than a decade testing different types lithium cells and traveled the planet to get the best info from those who actually use them in military and industrial settings. The advice he got was what I use to control my systems and so far after all these years, it's working really well. Hope to come across someone who has used them daily for more than 10 years one day before mine reach 20 years, so can't make any judgments others methods, just my own.

As with everything William, it's horses for courses and as this technology is still relatively new, no one knows and it's all just guess and hope. But I reckon if you keep your within 12-14v and don't go over, you have a great chance of getting really long lives from them and if you use a bulk charger, you will get a better experience and maybe longer life.

My late mate kept saying he reckoned if you kept your pack in the right condition and charged them properly, he couldn't see why they would deteriorate at all for many decades. So that's what I'm doing and have over ten years up so far without a problem and have yet to come across the supposed small but noticeable charging memory some have put forward as being inevitable. Again see that as comes from regimes that use lead acid charging and create these problems, but could be wrong.

If it's working for you William, then stick with it. Most of these discussions revolve around different approaches and if they achieve the same outcome and people are happy, that's all that matters. It's the dissemination of knowledge that matters, nothing else and from that we all grow our understanding.

[Busman]

Well I don't agree about them needing repeat business with the sort of time frames quoted !!!!
Even building another factory to build 10,000 Ah cells they can't keep up.
I enquired about 200,000 Ah's and they told me was a small order !

[native pepper]

Was being conservative William, already know a couple of lifepo4 people, using lead acid chargers and after 6-7 years, their cells have lost some capacity. They still charge properly, but rarely get over 13.4v after settling. Gave them one of our charge controllers and told them to charge the cells, which is 14v and discharge as rapidly as they could 2-3 times and the cells should come back to normal.

Saw this done by my late mate, he'd been testing some cells with what could be classed as high and very low charge parameters and they began to fail. He rang some bloke in Canada he knew and was told to try this method and it worked. Not sure for how long it continued working, but his explanation and someone can probably phrase it better, was. All the little ions ( I think), in the cells like to be treated the same and face the same way and the charge methodology is very important as to how cells take and use charge.

With lead acid charging, it is constantly increasing or decreasing charge, to cater for the resistance of lead acid cells. What this supposedly does is make the ions bank up and face different directions, making it even harder to get charge in and when you add heat because of ion build up and being crammed together facing different ways, it gets worse. Inside a lead acid cell, the ions coming in, bounce of those already there and send them all moving in different directions, causing resistance. It then takes them awhile to get themselves in order, so charge can be used. But because of how lead acid operates, the ion confusion means ions are forced out and you lose charge. This continues on throughout the life of the cell, because of the internal environment the ions are stored in. When you want charge, you are restricted as to how much you can take instantly without damaging the battery, because all the ions are scattered everywhere and create a resistance to use.

With proper lifepo4 charging there's no confusion in the ions, they are transfered directly from the charge system to the cells without significant resistance, so flow smoothly into the cell. Because of the type of chemicals used and as they are dry, there is little resistance from either the charger, or cell. So cells flow rapidly into the cell all facing the same way and in line, when they enter the cell they are not dispersed willy nilly, but form a line all facing the same way. Within the cell, instead of floating they are all lined up in what could be called a big, ever decreasing circle into the centre of the cell. When they are needed, all you have to do is pull the string of ions and they flow smoothly out.

But if you use lead acid charging regimes and equipment on lifepo4, you will get confused ions and over time they will create confusion within the lifepo4 cell, create resistance and finally block capacity. Heavily charging them properly then discharging heavily a couple of times, is claimed to give the ions the chance to get untangled and then take charge properly.

This is how I was told it works, being non technical can understand it this dummies explanation. But how true it is, have no idea, it's working for me nicely and only time will tell for us all using lifepo4, as to what and what doesn't work with them for a longer better life span. They are light years ahead of what we've had to use, so charging them properly and not like lead acid, seems logical to me.

[nut17]

I have installed the new cell balancer and performed a top end balance prior to hooking the new magic black box up. Will track cell voltages with great interest over the next view weeks. All four cells were between 3.71v and 3.74v when the solar went to sleep around 6.30pm. The mains charger is switched off and the fridge should take around 20 AH out of the battery overnight. We are scheduled to hit the road about 10.30am tomorrow.

Cheers
Chris

[BruceS]

Enjoy your trip Chris!!
Do you have CELL top limit alarm? (just in case a couple drop down and one of the others bolts.......)

[T1 Terry]

Well I don't agree about them needing repeat business with the sort of time frames quoted !!!!
Even building another factory to build 10,000 Ah cells they can't keep up.
I enquired about 200,000 Ah's and they told me was a small order !

200,000Ah isn't even a container full so you would be waiting at the end of the supply queue for delivery. That is the problem the two suppliers here in Aust suffer, not a big enough order to move to the front of the queue. We have been doing face to face negotiations with the big men within the Winston delivery section and a single container would get us to the forward section of the queue, 5 containers would get us near the front..... that is the level demand for the product. We are still negotiating and our direct contact has serious level political clout, but without outlaying over $1mUSD we aren't in the hunt as far as leverage goes. Add to the deal that all orders are paid in full in advance and then the shipping, Aust import duties etc still goes on top there is simply not the market in Aust to make that sort of financial commitment viable.

T1 Terry

[Busman]

Nope not a container full, they way they pack them it is actually cheaper to ship as a mixed container load, they can cram so many Ah into a plywood box it is amazing.
This was a wake up call to me.
They do however want to move large amounts and are looking for a high volume, low margin supplier which is what we are talking about.
6 weeks delivery out the door is what I was quoted for 200,000 Ah, though they would prefer to do it in 2 shipments to spread the load on their production.
If the farm sells for way more than wifey expected I have plenty to play with so we will see what happens.
It is an interesting idea, may well play with it once farm has gone, we have never had the NP (that's nett profit not native pepper) that daughter has achieved so it will go quickly.
Then we will see if we do something or go travelling.
If we did something I am looking at working 3 days a week and using VP for the other 4, could be an acceptable lifestyle ? I have 2 interested parties already that would soak up the first delivery, so not enough risk to worry about.
Just a bit worried about doing nothing................

[nut17]

Enjoy your trip Chris!!
Do you have CELL top limit alarm? (just in case a couple drop down and one of the others bolts.......)

Sorry Bruce. A bit slow to reply. I have no individual cell monitoring or alarms. The main charge source is from my 1200w solar bank through a Fangpusan "knock off" Flexmax Outback 80 controller set to 13.8 volts bulk and absorption and 13.3 volts float. Float mode rarely operates as 13.3 volts is the static lightly loaded voltage of the bank even as low as 70% SOC.

The new budget auto cell balancer is brilliant with the cells keeping accurate perfect balance to two decimal places at any state of charge experienced so far - Have not gone below 70% SOC.

Cheers
Chris