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

[expresso]

i noticed they updated there PL8 bump unit - not sure what was upgraded or if its now good for our use or not - it shows an app you can download also to control it -- maybe thats the upgrade ?


http://www.revolectrix.com/chargers.html

[Burgerman]

Theres always been a phone ap. Theres still no windows ap. Other than to update firmware. And its still all safety nazid and we dont know what it will do. So, avoid! The only advantage that bump thing has is if you are like me, a hobby user. With dozens of different lipo packs at the flying site. Theres at least 10 on my bench. One for heli, 2 different ones for my quadcopters, 3 different ones for my planes, and a bunch of random or older ones. Also some in transmitters, goggles, etc. So at the flying field You just bump and plug in. The charger remember all the settings (which are limited) for each. Different cell counts, different charge voltages from HV lipos, normal lipos, and lithium ion cells etc. So it stops you needing to choose a profile manually or choosing different parameters.

For e.g. some of my packs are 8C charge. So fast. Some are 1C. Or .5C. Some are 7S and 8S, most are 3 or 4S.

For our use its pointless and offeres only basic settings. And even if we have 3 powerchairs, the same profile will likely be fine for all 3.

[expresso]

ok just checking if they upgraded it enough for our use -

i am still waiting on my new charger since Feb - now they say maybe in August to start shipping them out -

[snaker]

BM, I bought some 18650 li-ion cells, they are lishen 2500mA, 5C discharge (lishen is fairly popular here). The seller claims new and full 2500mAh capacity but he is not sure about charge rate. By your experience, with its 5C discharge, can I charge it at 3.0A SAFELY?

[sacharlie]

Tagged for future ref.

[snaker]

BM, do you know if a single genuine Panasonic or Samsung 3500mAh 18650 li-ion cell could be charged at 3A?

[Burgerman]

Normally you can charge them at a max of 1C so yes, but its not recommended. Its like charging your 100Ah lithium pack at 100A. You can do it, no problem. But they dont much like it if you keep doing it.

Better to be say 1A to half C max. Its not much slower in the end anyway. Because the high capacity ones are higher impedance. They will take a while anyway.

[funkykeyboard]

PL 8 and regular use.

So once you have created your "perfect" battery pack, what is people's experience with the PL 8?

How many charges have you done in your Pack's life, and how many times has the PL 8 spotted something, made you aware of something, that you needed to rectify?

What kind of things has the PL8 made you aware of, how (what appeared in the graphs) and how have you rectified the problem?

Funky keyboard

[Burgerman]

How many charges have you done in your Pack's life, and how many times has the PL 8 spotted something, made you aware of something, that you needed to rectify?

All the time. Sevearal packs. Mostly a cell developing higher self discharge or a bad connection. Over the last decade I lost count. And its essential for setting up and building a pack initially too. If you had a lot of time, and adjustable power supply, a bit of knowledge and a clamp ameter and a decent voltmeter you could build a pack. But very hard to monitor it without visual aids like a graph or resistance readings etc.

[expresso]

i wont feel good without one that i can see the graphs - i have had about 3 or 4 times on 3 different packs - that i had to address -

i would not have know if i couldnt see the graphs - or another time - it was the dump load that got my attention but only because i can see the graphs at the same time

i noticed one cell dropping too fast right away - it was a connection issue - i had to resolve before starting to use the pack or install it -

but strangely - if i had never tested it with the dump load - i wouldnt have noticed - since the PL8 discharges slow - it didnt have an effect

once i discharged at 40A a hour - i noticed it - so its not 100% either - i now like to use the dump load after i build a pack to discharge some and make sure not any once cell is dropping too fast over the others - it could be a weaker cell also - depends if it keeps dropping or drops and then levels out - either way having the graphs to see it happening is needed - or else it would have been installed and used for who knows how long before it becomes a bigger issue - at some point down the line

my first pack - same thing after a year - i noticed something - turned out - cell was bad - headway - i changed that one cell and never touched it again - without the graphs - i wouldnt know and would have just kept using it -

this winter i also redid one of my ADD Ons - which had a connection issue on one Cell - i ended up stripping the Cell - no longer could use a screw on it - changed that one cell and fixed it back better with the connections -

without it - is like using a BMS - you never know what is going on - each time i build one i try to improve from the previous - either with wiring or connections - more careful to locktite the screw good - etc,

and still waiting for the PL8 - now its March - each month i call its the next month -

[funkykeyboard]

i wont feel good without one that i can see the graphs - i have had about 3 or 4 times on 3 different packs - that i had to address -

i would not have know if i couldnt see the graphs - or another time - it was the dump load that got my attention but only because i can see the graphs at the same time

i noticed one cell dropping too fast right away - it was a connection issue - i had to resolve before starting to use the pack or install it -

but strangely - if i had never tested it with the dump load - i wouldnt have noticed - since the PL8 discharges slow - it didnt have an effect

once i discharged at 40A a hour - i noticed it - so its not 100% either - i now like to use the dump load after i build a pack to discharge some and make sure not any once cell is dropping too fast over the others - it could be a weaker cell also - depends if it keeps dropping or drops and then levels out - either way having the graphs to see it happening is needed - or else it would have been installed and used for who knows how long before it becomes a bigger issue - at some point down the line

my first pack - same thing after a year - i noticed something - turned out - cell was bad - headway - i changed that one cell and never touched it again - without the graphs - i wouldnt know and would have just kept using it -

this winter i also redid one of my ADD Ons - which had a connection issue on one Cell - i ended up stripping the Cell - no longer could use a screw on it - changed that one cell and fixed it back better with the connections -

without it - is like using a BMS - you never know what is going on - each time i build one i try to improve from the previous - either with wiring or connections - more careful to locktite the screw good - etc,

and still waiting for the PL8 - now its March - each month i call its the next month -

sorry, what is the "dump load"

Thank you for that. I obviously have a lot of conflicting opinions on this topic. I do have a PL 8 now, but I have friends who would like the lithium but don't want to spend the money (£500 on 2 chargers). So I was wondering if I could build them for them, and then just give them a cheap charger.

Probably ask you some more questions about this when I know what a "dump load" is.

[Burgerman]

Yes you can. And yes there will be problems down the line. Esp if you dont know what you are doing yourself and offering to build for others. Its not the charger that fixes and sorts everything its knowledge. Logic. Experience.

The PL8 can only do an internal discharge at 100W or 10A whichever occurs earlier. So discharging a large pack to test takes days. So many of us use a 24V 40A load to dump the power into while using the PL8 to monitor voltages. This lest you see a high resistance cell or conection too as the higher load makes a voltage drop on a cell look much more obvious. And it allows a 100Ah pack to discharge fully in say 2.5 hours. It will not cut off automatically you have to do that yourself.

[expresso]

the best of my understanding is that the PL8 is the best charger for the job - for the large packs we use - its also been modified some with BM's help with the company - to make it work better and not give errors with large packs - or not balance correctly - in its stock presets - they wont work as good or if at all -

using the presets BM will make - are the ones you would load in the PL8 and use only those made - you can make some changes to them such as charge rates - term. cut off etc, - but they have been modified to work - which is done in the background - we wont be able to change that -

you can try other chargers if maybe the pack is small - ADD ON etc, it may be Ok - i cant say for sure it will work correctly - if you want to make sure it works - use the PL8 - and not worry - now if they start shipping them again - would be nice -

[swalker]

PL 8 and regular use.

So once you have created your "perfect" battery pack, what is people's experience with the PL 8?

I think you are asking how important I think the PL8 is for my lithium setup.

I judge it to be critical, so much so that I have two PL8s in case one goes down (and one has gone down and was replaced under warranty).

I used the PL8 to assess the quality and characteristics of the cells in my pack. The PL8 has been the only charger used for that battery pack, which has been in service for almost 2 years now. I don't know how many times I have used it to charge the pack, but "a lot" would be a good answer.

I started off with some pretty questionable cells. Some were bulged and they showed obvious signs of prior use, despite the sellers insistence that they were new. The PL8 has allowed me to keep an eye on them and make sure they are behaving OK.

I had a circuit breaker fail on the wheelchair. The PL8 allowed me to have confidence that the batteries were not involved in the failure.

In short, I have 2 PL8s and 2 power supplies. I would not want to use any other currently-available product to do the job.

Steve

[funkykeyboard]

So basically a load dump, whatever that is (eBay makes me no wiser) is a stress test. You put the pack under a lot of stress to identify any weaknesses.



https://www.ebay.co.uk/sch/i.html?_from ... p&_sacat=0

[Burgerman]

No. Its a method of discharging a large current x volts = a high wattage by turning it into heat. Why would you do that? Because to store a lithium pack that you are not using daily you need to discharge it by around 30 or 50%. Usint the PL8 to do that will take a very long time. A load of any kind, such as a heater, or anything will do, but I use one that is designed to pull 40Amps at 24V. In this case for a wind generator as with no load to dump power when a battery is full they overspeed and it throws blades...

[expresso]

https://www.ebay.com/itm/24-Volt-1500-W ... SwHoNfWOfB

i have a small compact one - does 40A 24V - i wouldnt say stress - when we ride out chairs - it discharges much faster than the PL8 - so a dump load is somewhat how it reacts when you use the chair for real - most times the chair dosnt use 40A - sometimes it uses alot more - 120A and most times 15A

either way - if you connected one to your new pack - it will start to discharge it at a much faster rate - so you can see how the pack Cells react when under load for real -

if thats all you wanted to do - or if you wanted to discharge a 200ah pack - using the pl8 takes about 18 hours - if you wanted to do it faster - connect one in the chain and still use the pl8 to monitor the volts - so you can stop it before they go too low and damage the cells

just a way to discharge faster - that was my main reason for getting one - and i realized its good to use to check the pack - since its closer to how it would react under real life using the chair outside -

[funkykeyboard]

https://www.ebay.com/itm/24-Volt-1500-Watt-Divert-Dump-Load-Resistor-Bank-for-Wind-Turbine-Generators/390947911868?epid=2263228609&hash=item5b064fb8bc:g:sUYAAOSwHoNfWOfB

i have a small compact one - does 40A 24V - i wouldnt say stress - when we ride out chairs - it discharges much faster than the PL8 - so a dump load is somewhat how it reacts when you use the chair for real - most times the chair dosnt use 40A - sometimes it uses alot more - 120A and most times 15A

either way - if you connected one to your new pack - it will start to discharge it at a much faster rate - so you can see how the pack Cells react when under load for real -

if thats all you wanted to do - or if you wanted to discharge a 200ah pack - using the pl8 takes about 18 hours - if you wanted to do it faster - connect one in the chain and still use the pl8 to monitor the volts - so you can stop it before they go too low and damage the cells

just a way to discharge faster - that was my main reason for getting one - and i realized its good to use to check the pack - since its closer to how it would react under real life using the chair outside -

Okay I understand better now your earlier comments.

So you were using A pack in the wheelchair and not noticing that one cell was discharging at a higher rate (this would be the volts per cell graph wouldn't it?) than the other cells because you couldn't monitor the cell drop whilst using the wheelchair, until you mimicked the wheelchair with the "dump load" with the 2 pack power cables plugged into it from the pack, and the balance cable from the pack plugged into the PL 8 and set to monitor, yes?

[Burgerman]

Thats what he does. I have an adjustable power supply. It allows me to also add the dump to the power supply output. And switch it in (with anderson) when I choose do do a regenerative discharge. So I dont plug it in seperately and monitor, althougH I can. But it allows the PL8 to do a 40A discharge directly that isnt limited to 100W or to 10A. And so I can monitor current, and cell balance, and internal resistance directly. It tales a little setting up and undestanding but it works.

[funkykeyboard]

i wont feel good without one that i can see the graphs - i have had about 3 or 4 times on 3 different packs - that i had to address -

i would not have know if i couldnt see the graphs - or another time - it was the dump load that got my attention but only because i can see the graphs at the same time

i noticed one cell dropping too fast right away - it was a connection issue - i had to resolve before starting to use the pack or install it -

but strangely - if i had never tested it with the dump load - i wouldnt have noticed - since the PL8 discharges slow - it didnt have an effect

once i discharged at 40A a hour - i noticed it - so its not 100% either - i now like to use the dump load after i build a pack to discharge some and make sure not any once cell is dropping too fast over the others - it could be a weaker cell also - depends if it keeps dropping or drops and then levels out - either way having the graphs to see it happening is needed - or else it would have been installed and used for who knows how long before it becomes a bigger issue - at some point down the line

my first pack - same thing after a year - i noticed something - turned out - cell was bad - headway - i changed that one cell and never touched it again - without the graphs - i wouldnt know and would have just kept using it -

this winter i also redid one of my ADD Ons - which had a connection issue on one Cell - i ended up stripping the Cell - no longer could use a screw on it - changed that one cell and fixed it back better with the connections -

without it - is like using a BMS - you never know what is going on - each time i build one i try to improve from the previous - either with wiring or connections - more careful to locktite the screw good - etc,

and still waiting for the PL8 - now its March - each month i call its the next month -

so in all of these instances, the PL 8 has several graphs for different functions, but it was thegraph that shows the rate at which the voltage was dropping that indicated there was a problem?

Are there things to look for in particular in the other graphs, that shows packs are faulty?

[Burgerman]

Yes many. And the shape of the graphs and esp the shape of the balance traces tell me many different thigs.

By PM I told elryko that he had a bad connection. He said not. In the end he removed the pack and found that he had stripped several threads. The shape of the graphs told me that because I undestand cell resistance, ohms law etc.

E.G.

Re: Hi! John

Sent: Wed Jan 13, 2021 3:15 pm
From: Burgerman
To: elryko1992
Does it still do this download download/file.php?id=14754&mode=view

Re: Hi! John

Sent: Wed Jan 13, 2021 4:53 pm
From: Burgerman
To: elryko1992
You have a bad connection on a terminal.

Re: Hi! John

Sent: Wed Feb 10, 2021 10:46 am
From: Burgerman
To: elryko1992
You should have installed them with RED LOCTITE and not overtighten them. Or the nuts.

You should use abrasive paper on the surfaces before connection. To remove all oxides. You should use a stainless nyloc nut and a stainless flat washer. I would not have used M7. I would have helicoiled every cell.

That graph told me you had bad connection somewhere.

Please post this info on the forum.

Re: Hi! John

Sent: Wed Feb 10, 2021 10:29 am
From: elryko1992
To: Burgerman
Hi! I change all the screw to my cells, i found 3 hole broken and i make it again and put M7 screw, very nasty... but i did. i will charge this days to see the graph. Thanks BM. i put this 2cm. https://www.ebay.com/itm/M6-Stainless-S ... 1195.m1851

[Burgerman]

I diagnosed which call, which connection, based on what I saw on that graph very easily. When he took it apart he found exctly what the PL8 suggested. Diagnosed in the UK based on his graph in rumania. I look at my charge graphs on every single charge. Mostly they show no problems. Except maybe say cell 5 has higher self discharge, or cell 8 is higher resistance but not enough to worry about yet. Or that I should tweak the termination current a little based on what I see.

[funkykeyboard]

I diagnosed which call, which connection, based on what I saw on that graph very easily. When he took it apart he found exctly what the PL8 suggested. Diagnosed in the UK based on his graph in rumania. I look at my charge graphs on every single charge. Mostly they show no problems. Except maybe say cell 5 has higher self discharge, or cell 8 is higher resistance but not enough to worry about yet. Or that I should tweak the termination current a little based on what I see.

Wow! That's like scary psychic shit.
My cell 8 was completing charge slightly quicker than all the others, and my cell 5 was slightly slower. So I swapped the 2 of them position wise in the pack, so 8 became 5 and 5 became 8 to check the wiring, and the situation remained the same so, I assume it is the cells.

That was the new pack with this new charger. Now they've been charged and discharged a couple of times, the original sell 5 doesn't seem to behave as badly. the original Cell 8 is still always the 1st to complete charge.

[funkykeyboard]

The reason I'm asking this is as I said before it would be really nice to be able to help my friends in Southport who use wheelchairs, who don't have the time, the money, and interest in doing this themselves. Especially with all the accoutrements the lithium cells need.

The 2nd reason I'm asking this, is my last lithium pack was on my previous Lifestand wheelchair, which had 2 battery boxes one on each side of the chair with the standing mechanism in between, with 2 6V batteries in each which were terrible. Dying virtually every 12 months. The electrician I had built up 2 lithium pack wired together. I used a Hyperion charger, and that fusion power supply for at least 4 years. Never looked at a graph, and never had any problems with it. It was absolutely brilliant mileage wise.

That's what's given me the impression that this task was not as complicated as it now sounds.

Why "I would not have used M7. I would have helicoiled every cell." To increase surface area of contact?

[expresso]

Yes funky - i dont monitor the cells during use in the chair - i really dont need to being the pack is large - But you can add extra balance wiring and then connect a cell monitor if one chooses - i dont want the extra wiring and i really wont be checking it to be honest -

I check it when i build the pack before going into the chair - so if i see something is a bit off - either the screw - or if not then its a weaker cell - depending how you see the volts react - you can decide if its ok to leave alone or replace if its that bad -

once i am done and install it in a chair to use - i will only know if something goes wrong when i get home to recharge on the PL8 with the graphs - and i only realized this when i started to build a Large Pack - i didnt want to wait so long with the charger to discharge it - so i got a load dump to do it faster and thats when i seen one cell dropping faster than the rest -

usually it would drop faster instantly - turned out to be a connection - screw - had to replace - and worked fine after - hopefully it should remain that way for a long time

[Burgerman]

Wow! That's like scary psychic shit.

No its not. Its an understanding of physics. Those laws are not like your hobby of philosophy. Thats the opposite to physics. As I say after physics everything else is stamp collecting. It the problem you have with all that other opinion and woo woo based stuff.

It was looking at the graphs, and the voltages, and knowing that the charge current was limited to the balance current to keep the blue/purple cell from going above the CV voltage that was doing the initiall "fully charged" impression, which that dropped lower once the rest caught up that SHOWED me what was happening (high resistance to main cell connector on that cell) because after current fell due to the others cells becoming full it then showed less than full. And took ages to catch up. So it wasnt really full at all. The charge current was making it look that way due to high resistance allowing it to push voltage up to the limit. Ohms law. And as lenny said elsewhere you can break human laws, you cant do that with ohms law. Or any other law of physics.

[funkykeyboard]

So does anybody load this information collected from the graphs into spreadsheets?

It seems to me at the bare minimum if you put into the spreadsheet what mileage you have done, and the amount of fuel you have put in the cells, you are going to get a rough idea of how far you can get on the open road on a full charge.

As anybody produced a spreadsheet that goes beyond that. Any chance of you sharing it if it is more useful?

Thanks in anticipation, funky keyboard

[expresso]

i think most of us - at some point become familiar with distant range - and battery life - that you just know more or less - how many miles you can do - i save my charge graphs but i dont add in the details of that days range - with my chairs - i just know give or take

i figure 90ah - pack - good for 30 miles safely - 200ah pack 50 miles - 60 miles easy - all depends - give it a good year of using a new chair with lithium and you know - but good idea to save on a spread sheet if you put the time in to enter the info.

or at least put the info. on the graphs when you charge and save them - date and distance traveled- plus how much battery used -

[funkykeyboard]

i think most of us - at some point become familiar with distant range - and battery life - that you just know more or less - how many miles you can do - i save my charge graphs but i dont add in the details of that days range - with my chairs - i just know give or take

i figure 90ah - pack - good for 30 miles safely - 200ah pack 50 miles - 60 miles easy - all depends - give it a good year of using a new chair with lithium and you know - but good idea to save on a spread sheet if you put the time in to enter the info.

or at least put the info. on the graphs when you charge and save them - date and distance traveled- plus how much battery used -

thanks very much for your support expresso. May all your coffees be perfect LOL

[expresso]

believe it or not - making a espresso is not as easy as it seems - its actually very hard to get it right - alot is involved that has to correct to get that good shot

temp. bean grind - dosing - amount of grams - fresh beans only - temp in the apt. changes the outcome also - different in the morn. than the evening shot -

kind of beans used - once you have a real espresso shot - nice creamy tasty - you cant have one outside any more - they all suck - starbucks is joke -

since i am always trying different beans - not always get the perfect shot - besides the right grinder - and espresso machine - cleaning - water softener - all makes a difference.