PL 8 - Q and A section - How to Set up - Use etc,

[Scooterman]

Well done BM, much better than the heaters I was googling, and a good price.

I will get myself one of them

I'll use countdown alarm on my phone and set a back up alarm so I don't do what you warn of

[Scooterman]

BM - Could the LOAD be wired in parallel with a pair of lead acids via a high amp diode (to stop the LOAD discharging into the lead acids). (And so PL8 sees a voltage).

And then connect the PL8 to the LOAD so that lithium discharges into LOAD (but not lead acids) and then discharge current can be graphed?

or

[Irving]

The Load is passive, current only flows into it, never out. I'm not sure what you suggest is possible or necessary, but maybe I've misunderstood?

[Scooterman]

The way I thought of it is that the load and lead-acids are connected to PL8 input, lithium to the output.

Switch PL8 to Regen discharge and discharge at circa 40A into LOAD, resulting in fast discharge and warm room.

[Burgerman]

I think he means...

Connect the lead acids as a SUPPLY to the PL8. With a diode. So the PL8 cant charge them.
Then connect the load device to the PL8 input, so the regen can only go to the load device.

You could. But as soon as you connect it, it will begin sucking 40A out of the supply battery. Until you start discharging. So I dont see any advantage over no diode...

The PL8 wont overcharge your lead supply battery whatever you do. It stops or reduces power as the voltage rises to whatever the regen supply is set to do.

[Burgerman]

Study settings on this page CAREFULLY.

I set my POWER SUPPLY to 24.0V exactly.
So now, I connect the DUMP DEVICE to my POWER SUPPLY, as well as the PL8 input.

What happens? PL8 lights up, recieves 24V.
DUMP DEVICE also sees 24V and starts taking 40A from the POWER SUPPLY. And gets hot!

Now I choose DISCHARGE and set to 40A. REGENERATIVE.
The PL8 starts to ramp up to 40A discharge, and makes its graph.
The PL8 pumps its regen current into the POWER SUPPLY but this raises the voltage to 14.4V (28.8V) as thats what was choosen below. So now the 24V POWER SUPPLY is adding zero Amps. Since the voltage is ABOVE the 24V it is set to.

And this state of affairs continues to the end of your discharge. At which point the power supply starts feeding the DUMP DEVICE. And you turn off. Add a switch.

[Burgerman]

Add this https://www.ebay.co.uk/itm/24V-Battery- ... Sw1LRZsACz

Or similar, with a 40A capable relay or SSR and the power supply will not feed the device, only the INCREASE IN VOLTAGE on regeneration will switch it on. So you can leave the dump load, and set 24V or less, and it can stay connected indefinitely to the suppy.

This way, your PL8 will have full 40A discharge capability.

I have in fact just ordered that item, already have an SSR (60A) and a heat sink.
So my SM 3040 power supply will have the DUMP DEVICE connected permanantly, and it will never cut in unless I set voltage above the 12/24V level I set. I will set 25V. Set supply at 24V. And regen to 26V or similar. And fiddle with them in detail till it all works as planned.

Relays, get the 60A DC/DC one. https://www.ebay.co.uk/itm/SSR-Single-p ... 9vg2lTXoxw

It will need a heat sink. https://www.ebay.co.uk/itm/Heat-Sink-fo ... xycmBSxmLW

[Scooterman]

Study settings on this page CAREFULLY.

I will, I need to read several times, assimilate and cogitate until I feel bold enough to reply

[shirley_hkg]

Dumping it into empty batteries is easy, with no additional gadget.
No worry about over charging . PL8 will switch to its internal discharge mode, when batteries are full.

https://www.wheelchairdriver.com/board/ ... ly#p139228

[shirley_hkg]

They're offering refurbished units at $180, approx 21% off already, so with the extra discount thats 37% off. That's a real bargain!

Bought 2 at $313.

My first one was refurbished one. Working fine till I sold it last week with a 200Ah pack .

[Burgerman]

Dumping it into empty batteries is easy, with no additional gadget.
No worry about over charging . PL8 will switch to its internal discharge mode, when batteries are full.

But discharging a200Ah pack into lead for e.g. will need about 8x 70Ah lead batteries all sat in a discharged state! Or it just reverts to a 3.X A discharge.

[Scooterman]

I've read and re-read it and totally get it BM, it's clever. The SSR is to prevent arc when connecting load. And your screen shot was really useful.

But have decided not too. After charging scooter pack to 3.6v yesterday. Since 6pm yesterday I'm discharging to 3.17v to measure capacity (something I've never done), then will charge to about 40% SOC to store over winter.

I plug the pl8 into xlr and internal discharge for 40+ hrs. Only downside is to graph ties up laptop for a couple of days.

But only do it once or twice a year.

And don't have to graph.

Pl8 display zeros at 100ah is that correct?

[Burgerman]

No idea, I watch a PC screen.

[Burgerman]

The SSR is to prevent arc when connecting load.

No the SSR is to switch a 40A load, with a low current capable voltage switch. Use a mechanical relay if you want. But its no cheaper.

[stevelawiw]

Your DHL Express shipment with waybill number XXXXXXXXXX from REVOLEKTRIK HOBI INDONESIA PT is arriving in the country and will require customs clearance. There is import duty/tax due on your shipment. The amount is GBP 24.53

WTF? I'm being stung by customs Has anyone else had this or am I just lucky?

[foghornleghorn]

Hello, Your FedEx shipment Airway Bill #number has been imported from outside the EU; it is subject to an import charge of 27.19 GBP.

My parcel from Revolectrix a year ago was the same. Although FedEx delivered it then started demanding money afterwards.

[stevelawiw]

Oh ok thanks FHLH, not just me then!

[Burgerman]

At least fedex dont hold your parcel ransom for weeks while they get around to sending a second class letter to demand payment before delivery. And they actually deliver it, instead of knocking on the door and running away and making YOU collect it or jump through more hoops to get it redelivered. You then have to wait at the door or they do it again. Its easier for the driver to post a missed you card than actually find and deliver the parcel you see. I detest parcelfarce.

[stevelawiw]

Well maybe thats a plus that it's not parcel farce then! I'd better get on and pay it

[wheelie junkie]

Accurate charge - so in the factory charge presets there are accurate charge options, there doesn't seem to be a lot of difference, possibly lower charge rate but balance and termination almost identical. What do you need to alter to get an "accurate charge"?

[Burgerman]

Again.
There are no factory presets that you should be using on lead or on LiFe. Quite apart from the rediculous descriptions such as 'accurate charge'.

There are many things wrong with all of the factory presets, that are NOT adjustable, and that you cannot change.
They are unsuitable for any charge on either the A123 cells they are set up for, or especially any larger LiFePO4 cells we are using at all.

Use my presets, and adjust the settings you want in the advanced tabs, on those.

NOW to answer this:

Accurate charge - so in the factory charge presets there are accurate charge options, there doesn't seem to be a lot of difference, possibly lower charge rate but balance and termination almost identical. What do you need to alter to get an "accurate charge"?

Some BEHIND THE SCENES settings that you cant change.
And the balance start voltage (must be 3.500V or at CV only.
The total charge time limit.
The balance mV tolerance.
The balance setpoint -mV
The balance deadband -mV
The CV timeout period
The CV termination method and set point.
And a number of other things.

All the NON accurate charge profiles charge faster because they dont waste time balancing properly or terminating when each cell is full. Only the accurate ones work at all, but have many HIDDEN settings that are not suitable anyway. DONT use factory presets!!!

[wheelie junkie]

I'm using your preset but wanted to understand the difference between a "normal" charge and an "accurate" one more time at CV? Different termination current? Just trying to grasp how they differ and what makes one "accurate" sorry should of explained on the factory presets

[Burgerman]

What makes one accurate is very dependent on the actual battery type, c rate, cell capacity, cable length internal cell resistance etc and actual balance at the time.

If you charge a 2C life cell fast to 3.600V and then stop, it will be nowhere near charged as its a high resistance low C cell. Long charge cables make this worse. Since you may lose 300mV just down the cable at a few Amps! Even without a high impedance 2c cell. If its a 90C Lipo, with almost zero resistance, on short hobby style charge cable it will be 99% done.

So how long you hold the cell at its 3.600V and its other 7 groups of cells, determines how close it is to being full. 99 percent is fine. But realise that 1 group will be at CV much longer than some of the rest. Depending on actual balance level and internal self discharge and a few other things. So if you stop as soon as that last group reach CV then all the cells will be still unbalanced and display different voltages.

So...

How do you set for an accurate charge? By watching the graphs. And making adjustments to one of my profiles so that it terminates after around 1 hour at CV after the cells all reached 3.600V. So total CV may need to be 1.5, or 2.5 hours or whatever. You COULD just hold them all at CV for hours. That ensures that all cells are equally topped up and balanced. But they dislike being full. So the aim is to get all cells full, (so the stay balanced after disconnecting from charge, then stop.

And cell deadband narrow. This means setting about half a dozen setting to fine tune per pack. And another half dozen that are hidden from the end users.

[wheelie junkie]

Thanks, that is a lot clearer. I could modify a profile with different length CV time, lower charge rate and use it every so often. My off road LiFeP04 were charged with the A123 profile for a while and I want to try and get them properly balanced and as much charge in as possible but it doesn't get used much over winter.

[steves1977uk]

I delete all the factory presets and use my own since they're better set up for LiFePO4.

Steve

[wheelie junkie]

I'd do more but can't access the hidden parameters, without being able to look at everything that can be changed I don't think that I could start from scratch. Modifying something that I know is a good start point like the one BM did for me isn't as daunting.

[Burgerman]

If you start with any of the ones for lead or for lithium ion phosphate that I have posted here that are full power, (can do 40A) then all the settings you cant see are the same. Pretty much. So all you need do is correct the termination current, to suit your pack, to make it end after :

All cells are at the same voltage you chose. Ideally 3.600V.
Then add 1 hour for soak to make sure the lowest cell is also sat long enough to be full.

All the other settings, such as say 4 hours CV limit, charge Amps, termination current, charge voltage, etc can be adjusted. You may want to set that CV time limit to none, if balancing a new or long time stored pack to allow balance time to complete. You may also then want to set 3.500V charge, and balance only at CV so that the high cells dont spend a day at 3.600V at the same time. The thing is it all depends... On many things.

As long as you start with one of mine, all the hidden options are set to the widest limits so you can safely forget about them. They wont trip you up. The 12A XLR ones are limited to 12A max however.

[wheelie junkie]

That was my plan, use one as a starting point then watch a charge and alter termination and cv time then watch again. I'm guessing that my 60ah pack could do with a longer cv time. Lots to learn about charging.

[Burgerman]

It may now be OK. Or it may need a long CV for one charge to level it up properly. It all depends... And also what you see on the graphs. My charge profiles should have sorted that out already.

[Burgerman]

The NORMAL charge profiles, used in hobby chargers are really designed for SPEED of charge. To get that heli back in the air fast! (so very short CV, near enough balance, very high charge rates like 2 to 8C). Thats why our little hobby chargers charge our toys at a massive 40A, in a few mins, instead of overight. The so called ACCURATE charge, just charge fully. At least on a LiPo...

This works OK on lipos because:

Lipos = super low resistance. And very high current capability up to 130C or so. 8C or higher charge. ultra low resistance. So a tiny 4Ah lipo battery in my plane, can be charged at 32A easily... 40 in a rush. And start a car. And its impedance is so low that it doesent touch CV until its almost fully charged already. Its solid. The problem is that these same parameters are typically used on their LiFePO4 profiles too. Because some early A123 cells were 20C or better. So performed like a LiPo. The cells we use DO NOT!

Imagine this.
You have 3 batt types.

Lead.
LiFePO4.
LiPo. All in a bucket of water CV comparison analogy...

1. Lead, is like bucket full of dry stone & brick. Try and soak a bucket of dry (discharged) bricks with water and it will take many hours sat soaking under water (CV) before it becomes 100% saturated and all the air bubbles stop coming out. Around 8 hours in fact to fully saturate the bricks or lead battery. Trying to drain the water out has the same problem. Hence peukert...

2. LiFe, is like a bucket of sand. It takes maybe 60 mins before all the bubbles stop, and the sand becomes fully saturated. So a much shorter CV is needed before all the water is absorbed into the dry sand. Likewise the water can be removed almost as fast. So compared to lead, almost no peukert. But there is a few percent.

3. LiPo or lithium polymer hobby packs are like a bucked with nothing in it. Just the empty bucket. You fill it with water and its done. No CV time (soak time) is really needed. All the bubbles stop and its full straight away! So only the CC (filling up) bit is needed. So after maybe 3 mins all the bubbles stop, the bucket is as full as you can get it. Likewise it can be emptied as fast as you pour it out. Hence up to 130C capability.

Once you grasp this, it all becomes simple! CV current or soak, in this analogy, is the termination current. When current drops to almost zero, the bubbles have stopped and the battery is fully saturated/full.