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

[wheelie junkie]

Thanks for the explanation, very useful. I was intending to alter your profile for the times the cells come out of storage, give them more time at CV. My support workers need it to be simple so 2 slightly different profiles is the easiest way. Just have 2 on screen clearly labelled.

[Burgerman]

The time spent at CV depends on several things.

Charge rate. The faster you charge, the longer the CV stage. Because it pushes the volts up (high impedance, so low C cells do it faster) earlier in the charge cycle.

Theres a box that says BALANCE MUST BE DONE if ticked it will end charge only if all cells are within the 2 or 4mV or whatever you set deadband. But remember that the PL8 may still be applying a 'brake' of up to 1A to the full cells. And so it can end while the low cells are still being charged at 1A or so. Meaning that while CV was maybe 30 mins to 2 or more hours, the LOWEST cell, was still charging. Its voltage was supported by the 1A charge.

So even if that is ticked, it should be!, then thats not the only thing that determines CV time.

You can set CV timer to none. This is then only imited to a hidden timer, a charge limit for overall charge time. Which is determined by a few parameters, such as if the cell count is auto, for e.g. So it needs to be set to 8S not auto, on a new or out of balance pack at which time the total charge time limit is 16 hours. If theres a cell fault that prevents it reaching its low termination mA point, and you have no CV timer limit (set off) then that means you could end up charging a bad cell at 40A for 16hours if theres an internal short... So is a fire risk. All of this needs to be considered. So if set to NONE, then you really need to monitor whats happening.

So, for e.g. if CV limit is set to 2 hours, and say 500thC termination current, and all cells are withinn choosen bandwidth, it will end due to low correct termination current once reached. In around 30 mins to 1 hour after CV starts typically.

If after you do that, and monitor cell voltage afterwards, and one cell drops a lot faster than the rest, do an extended charge with maybe 2 hours CV as limit and 1000thC termination. It will bring the slightly low cell up to full. But the other cells wont loke being held high for the extra hours. Everything is a compromise. However a WAY better compromise than any BMS that tortures the cells.

[wheelie junkie]

Thanks again. I did watch the last charge and you can see cells start to bypass and the current changing in line with this, by watching for a few hours you can see the current slowly drop so should be able to find a termination current point for the pack depending upon how long I want them to soak. I was hoping to get the preset done quickly because of a looming deadline but might have to talk to my friend who built the pack for me.

[Burgerman]

I have an option that lets me see and change a lot of things...
E.G.

Look at the menu bars above.
And the options even on the first tab...
The issue is that if everyone had these, without knowing how they all affect the actual algo, options, and when goes on behind the scenes that you can make it dangerous, and damaging to your cells, and non of this stuff is obvious esp if you dont really understand batteries well.
Like the manufacturer of the charger! They are clueless about lead or LiFePO4 needs in non hobby use or sizes. So thats why I change stuff...

Not to mention plenty of scope for messing up the charger...

[stevelawiw]

Got my PL8 it's just the bare charger in a plain white box, is that right? I feel like it's a refurb but I paid for a new one
I did order the FUMI thing and some extension balance wires tho
I just soldered an EC5 with 10awg silicon wire, I don't like them, they are nasty! I'll probably change it for an anderson later

[Burgerman]

Yeswhite box.

[stevelawiw]

Oh ok thanks

[foghornleghorn]

Mine came in a black Revolectrix box, although that was 12 months ago.

[Burgerman]

4 of them here. All white box. From singapore.

[wheelie junkie]

I'd noticed the tabs in some other screenshots and can see why you need to understand what you are doing. Like most things there is the assumption that the end user is an idiot but looking at the technical tab parameters it is perfectly reasonable to hide that from the majority of us.

[Burgerman]

Yes. Its not just the tech tab. I have many extra options, and wider choices in the other tabs. Things like the allowable cell gap mV levels, or the upper and lower voltages allowed on connection before errors, etc. And the ability to up the max current allowed, on various chemistries or many other options. Choices that wont make any sense to 99% of users. That are therefore hidden and geared towards safety and hobby packs alone.

So now I am deleting it so revolectrix dont know I have access...

[steves1977uk]

Both of mine came in black boxes with the Revolectrix logo on them.

Steve

[shirley_hkg]

Received my two refurbished PL8. One is V3.33, but the other is V3.31 .

Should I keep it as is , or should I return it ?

[steves1977uk]

Just update it to V3.33 in CCS Shirley, under the firmware tab.

Steve

[Burgerman]

Yes, or many of the changes they made, that I argued for, will be missing... Easy to update. Takes seconds.

[stevelawiw]

Any chance of a charge profile to charge 8 15ah headways in series please?

[steves1977uk]

Here's what I use Steve, you might want to tweak it to suit your pack.

Steve

[stevelawiw]

Thanks Steve

[Burgerman]

That will end quickly. At 150mA. Which may be OK on a set of already balanced headways. But if its a new pack, just built, or stored a while, better to set to a lot less like termination, at maybe 30mA. (500thC)
To give a chance to fully balance and all end up at the same full level.

[stevelawiw]

Many thanks. I have 16 I'm using to test my prototype GB chair so charging them as 2 8s1p as I only have the one PL8 newly unwrapped charger

[Burgerman]

So then, 2S is 30Ah, so 60mA is 500th of capacity, 5oothC. A good starting point. But once its all working well, headways charge faster (higher C rate than many cells) so that can be increased.

[Burgerman]

STORAGE profile. CHARGE first, if you think the pack may be unbalanced. Otherwise just start it and choose DISCHARGE.
This is after much experimenting...

It cuts off when discharging at approx 35 to 50% discharged. Or 50 to 65% full. So is OK for storage.
Its also OK for charging. But set your own termination current, and charge Amps to suit yourself. Currently set to charge at: 40A and 250mA / 8 hour limit.

It does stop at the right place on the 120Ah headway pack I am testing, at 3.270V and while discharging at 3.5 to 3.75A. (100W limit).
AFTER discharge, volts read approx 3.310V due to the bounce back and the cell resistance. Yours may be different! But not by much.

It is dependent on your lowest cell reaching the cutoff votage, your own packs resistance, and temperature.
So your mileage may vary! Each manufacturers cell varies a little too. These are on headways.

Its very hard to do this, because if you set higher, even a few mV, it cuts off power anytime between 10 and 40% at random times because here voltage does not = state of charge. Depending on a bunch of things. So it cant really be raised to a higher cut off voltage.

It cant really be lowered either! Or it can, but a few mV may mean you end up with a 60 or 70% discharge for similar flat curve reasons.

So try and if it works for you when watched the first time, then it should be OK on any subsequent discharges.
As long as the room is around the same temp.
The reason it works is that theres a notable step in the discharge curve, at around 40% to 45% point on many LiFePO4 cells when discharged at low speed, and this is set to stop in the middle of that step.

[Scooterman]

IR varies, but if we say 1 milli ohm per cell, and are trundling along pavement drawing say 40A. Are we dropping 0.32V across pack?

[Burgerman]

Internal resistance doesent just depend on cells.

Theres some voltage drop although not much on lithium because of the speed the chemistry takes place as well. This is many volts on a lead battery, and takes time to recover. In lithium recovery is fast. In lead its around 16 to 20 hours in full.

Then theres resistance of every connection.
Remember that theres 2 on the controller, 2 on a fuse or contactor, 2 on every cell so another 16, and these all add up. Then theres approx 40mOhm on the battery to controller cables. This can all add up to almost twice the motor impedance. So best to measure it!

[Scooterman]

Ah, yes! I remember reading in r-net settings that the motor cable resistant on the salsa is 40 milli-ohms?

While on the subject of voltage. On my scooter s-drive I increased battery volts to 27V for the lithium and gained about 1/2mob on a 9.5mph mob scooter.

But I've scored the r-net parameters and can not find a battery voltage setting anywhere which surprised me as r-net is a higher level controller than the ex-wife (s-drive) I don't know how that happened, lousy cheap android tablet

[Burgerman]

Motor voltage limit is only in the sunrise version.

[Scooterman]

Do you mean pgdt supply sunrise with bespoke r-net software for sunrise chairs?

And the r-net generic OEM software doesn’t have a motor voltage limit?

YES/NO?

Sorry to be dumb

[Burgerman]

Yes. Theres small differences between manufacturer versions and generic versions. And then theres permobil...

[Scooterman]

Thanks

[Scooterman]

PL8 manual says best practice is to connect balance wires first then banana jacks.

BUT it doesn’t say what is best practice for disconnecting?

I remember you saying always power up PL8 before connecting to batteries. And disconnect charge/balance leads from batteries before powering down PL8.

BUT Back to disconnecting charge/balance leads, is there a sequence? I normally remove the balance plug first then the banana jacks. But I don’t know whether that is right or wrong?

Sorry this question turned out to be a bit long winded.