80Ah ADD ON build

[expresso]

SB 120 - used one 6 AWG and 8 AWG together in one end - - 8 AWG going to the SB 50 - i need to make the last Cable going from this SB 50 end to the pack end - and then the charge cable SubD - for the pack -

[Gnomatic]

Looking good!

[expresso]

thanks - that cable was a bit of a pain to make and i had one shot at it - i didnt buy any extra - - but i took my time today with Quickie helping me - going from a 8 AWG wire to 6 AWG - is a huge difference - even looking at them - looks like its double the size - will use 8 AWG for the rest of the wire to the pack - and try for the first time to solder 8 AWG to an XT 90 connector - so the next cable will be SB50 end going from this cable to XT90 end going to the pack - that will be it for this and i can use it connected all together from then on - too bad its cold - i would love to go test this thing outside - will have to wait -

next when i am done - will make the Volt meter using this one - https://www.ebay.com/itm/Lead-Acid-Lith ... 2749.l2649

and this - https://smile.amazon.com/gp/product/B01 ... UTF8&psc=1

i can turn this so the wire is straight up the chair into my lap to keep an eye on it -

[expresso]

turns out i made my cable a bit too long - the Black SB 50 i used was too long - so i managed to fix that - i had to cut up some heatshrink that was too long coming out of the SB 120 end with both cables - it didnt look as nice after - so i wrapped just a small bit of graphing Tape at the ends -

would that be a problem leaving the graphing tape when its being used ? or should i remove it - i had to cut up some heatshrink - i wasnt able to get a nice clean cut all around - so i added the tape just to look nicer - it wont be seen either way -

would it be OK to leave it there ?

i have to learn to use less heatshrink from now on - i had too much going over both the cables and then i couldnt angle the black SB50 because of the heatshrink - so i had to cut some off to give the wire more room to flex and angle - i didnt realize how long it was overall -

[expresso]

this is before - even the SB120 - fits but just about - i can redo it - but this works and it fits - i was worried if too short the cable would be hard to snap in the shells being so close together - i should have double checked this before making it -

but the SB 50 was way too long - had to fix that - you can see the back pack with the ADD ON inside - all done etc, - its dosnt go past the rear - it sits flush even with the rear of the chair - i like how this one worked out - size of the pack - compactness - and looks neat from the outside - look just like a normal backpack -

Charge Cable is made and installed on the pack - all thats left to do is make the connecting cable from the chair to my pack - and volt meter will make also

[Scooterman]

This is very nicely done expresso. It’s not easy terminating short thick cables. Especially having to fit 2-pair of cables into one connector

[Burgerman]

Is a shame the bounder chairs use so much power.

That same 100+ the addon 70? would have made your Quickie chairs go enormous distances. Like 4 times as far as a set of MKs. That would be like having EIGHT MK 74Ah batteries on board without the weight.

Now imagine having those 176Ah cells in the quickie chair. AND that 70Ah extra. Thats around 245Ah. You only get around 40 from a set of 70Ah ead. So thats around 6x the range, and a bit which is a bit rediculous... Even for you.

[expresso]

yea i agree - i was a bit disappointed with the range on the bounder with 100ah - but its possible due to my tall gearing - because my friend got the same chair - but 10 mph gearing and he did much better than me the first time - which was the only time we went out to ride - end of day - short ride about 8 miles i would say -

my last option if i am really not happy with this setup is reduce the speed to 10 mph also and then i would gain alot more range back - but if i can get enough out this setup -

i am looking for a good solid 40 mile range with a touch left over to be safe - then i may just leave it alone if i am happy with the rest of chair speed etc, - if not - gear change and solve it that way.

no rush - i enjoy the speed thats for sure - and i still have 150ah on the 646 chair - -

[expresso]

Last cable done and ready to go - all connected -- i decided to try the 8awg on the XT 90 just to keep it neater without an adapter -

i wanted to stick with 8 Awg - if this didnt work - i would make it both SB50 end with small adapter -

If i recall BM said a while back - he did the Math and this bounder uses about twice the battery per Mile compared to my 646 chair

If i am lucky then i should just about make a 40 mile ride with the extra ADD ON now -

4 Ah per mile - 40Miles x 4 = 160Ah - I hope i can manage this much - i will be testing the range slowly - inching my way up to 40 miles

i have the volt meter made also - shows percentage - volts and bars - its configured for LifePo4 chemistry and 8 Cells -

i will just keep an eye one the volts - 24.5v is my limit on my ADD ON - the chair who knows -

[Scooterman]

Puzzled?

The single cell graph makes sense to me when CC charging. As the cell soaks up the current it's voltage slowly rises, then shoots up vertically when charged. (A characteristic of lithium)

And after about 2.5 hrs the cell is still at about 3.4v.

BUT when charging 8 cells the per cell voltage of all 8 nearly hit 3.6v in minutes, and yet they are obviously a long way off from being charged, they now balancing.


The question is why ONE cell 3.4v after 2.5hrs.

Yet 8 cells are at ~3.5...v after only minutes?

[Burgerman]

Because your cells have
a: resistance.
b: different lengths of time sat at CV.

So lets say the highest cell its 3.6V at 8am. Its now reducing in current sat soaked at 3.6V or whatever you set. Its NOT FULL, its sat at that voltage only vecause the charger is pushing its voltage high which is can do due to its internal resistance. But its the MOST full cell.

2 hours later all the other cells reach CV. But only just, and are nowhwere near full yet. But that cell above has been sat at CV for 3 hours already waiting for the rest. That one cell is REALLY full. And drawing no current. The rest are not YET full. But have reached the chargers chosen CV termination current. So reduce it. So that all the cells stay at 3.6v for longer. But its very hard to do that realistically on the tiny cells you bought. So charge ends with some cells at 99.7, 99.8. 99.9% full, and one cell or so at 100%

[Scooterman]

Sorry BM I should have made myself clear. The graphs are for espresso’s 80Ah cells.

But I’ve noted what you said regarding my tiny cells.

I’m not bothering with my 600mAh cells anymore, as you say I bought the wrong ones. But I might have one last go with them in a 4p2s arrangement

[Burgerman]

It is just the same no matter what size cells though. But with larger cells, you can set a lower TERMINATION point giving a longer CV so all end up fuully charged. Then they all will all drop at a similar rate afterwards. But remamber that not all cells drop at the same rate. That depends on self discharge rate. 3.4V is still full though..

[Scooterman]

Thank you BM

This is your 100Ah preset.

So the charger is initially putting out 3.6V and a CC of 26A.

The cells start balancing when the first cell reaches 3.5V. Then the charger switches from CC to CV, and the cells continue to balance.

The PL8 output is CV = 3.6V and variable current.

Then when the charge current drops to 200mA the charge terminates and the PL8 switches off, or does a cycle if required.

This must be really tedious for you but can you just say

YES or NO if I've understood this correctly.

Thanks.

[Scooterman]

I've just been comparing your lifepo4 presets.

So as a starting point for 90Ah in a 2P8S arrangement

Charge would be 40A

and Termination would be 360mA

Everything else remains the same.

[Burgerman]

I usually charge at around 1/4 the capacity. So 25A for a 100Ah pack. If you want faster, feel free. But within reason. LiFePO4 is happier charged at around the 3 to 4 hour rate long term. If you charge slower than this then thats not much of a problem, but it means more time and its not necassary to charge this slow.

Termination current. If the pack is high C rate, and well balanced, then a 300th or 330th termination poing works well. So that would be say 300mA on a 100Ah pack. If the thing takes a long time to balance, and to hold voltage evenly after charge, then reduce that to 500th or 750th of capacity. So it stays at CV longer. A 4 hour CV timer is OK on a pack that balances easily. An 8 hour limit is too long, but may be needed to balance an out of balance pack, or much longer. So initially this should be set to off or never ending on a new built pack.

Theres no correct settings, only the best at the time. Like once the pack is in service and balanced well, then reducing charge votage to 3.550V will extend service life a bit.

[shirley_hkg]

They are stored for a year or two .

I will charge @20A max , at least for the first few cycles .

[Scooterman]

I usually charge at around 1/4 the capacity. So 25A for a 100Ah pack. If you want faster, feel free. But within reason. LiFePO4 is happier charged at around the 3 to 4 hour rate long term. If you charge slower than this then thats not much of a problem, but it means more time and its not necassary to charge this slow.

Termination current. If the pack is high C rate, and well balanced, then a 300th or 330th termination poing works well. So that would be say 300mA on a 100Ah pack. If the thing takes a long time to balance, and to hold voltage evenly after charge, then reduce that to 500th or 750th of capacity. So it stays at CV longer. A 4 hour CV timer is OK on a pack that balances easily. An 8 hour limit is too long, but may be needed to balance an out of balance pack, or much longer. So initially this should be set to off or never ending on a new built pack.

Theres no correct settings, only the best at the time. Like once the pack is in service and balanced well, then reducing charge votage to 3.550V will extend service life a bit.

I understand thank you for that

Re your lifepo4 presets. The read me text says the preset settings are for 1S-8S only.

With say a 16 x 100Ah cell pack in a 2P8S arrangement, which preset would one use. The 100Ah presnt and select 2P parallel packs in PL8.

OR just use the 200Ah preset?

They are stored for a year or two .

I will charge @20A max , at least for the first few cycles .

Thank you Shirley, I understand

[Scooterman]

ADJUNT: When the parallel packs option is selected on the PL8, does the PL8 just multiple the relevant values by the number of parallel cells?

[Burgerman]

Dont use it. It increases current by x amount but leaves termination the same. Designed by an idiot. If using the daft auto charge finish thing that hobby people use on lipos it works. Set that to no in the setup screen and the option will go away.

[Scooterman]

Dont use it. It increases current by x amount but leaves termination the same. Designed by an idiot.

Understood thanks

[Scooterman]

BM - I've read elsewhere you mention that a CV phase of say 30 mins - 1hr or so is about right.

What does it do/achieve? You mention something about, that it stabilises the cell/s voltage after balancing?

So too short a CV phase is not enough to stabilise the cells, and too long is bad.

Is the latter bad because it's not good to hold lifepo4 at 3.6v or 3.55v for extended periods?

I didn't have a lot of success with my titchy cells so they weren't a very good learning experience. But I did notice that when the charger switched off the cells immediately dropped down from their 3.6v~ level, but to what voltage they dropped down to I can't rightly remember

But it's interesting trying to learn.

[Burgerman]

What does CV achieve?

Think about a battery as a resistor. Because it is also that!

If you take any battery at a low voltage. Say a LEAD battery, its all the same. Its dead, flat, exhausted at 11V. If you set a power supply to say 300A and 14.4V max, and connect the battery, in 2 seconds it reaches that CV voltage. Is it charged?

Obviously no! Take away the power, and the voltage drops back to 11V after say 8 hours. And its now 1% charged...

If you LEAVE it at that 300A CV for a while it will still be at 14.4V and the amps will gradually tail off. And become lower and lower. Eventually it reaches almost zero Amps. Now, it has soaked up that power. So now when you release the charger cables, and wait, it will fall back to the FULLY CHARGED voltage of 13.15V. This takes 8 hours approx on a lead battery at CV.

Lithium has a much lower resistance and zero Peukert to speak of. So it can be fully charged in as little as 3 mins CV for LiPo, 20 to 40 mins Lithium ion, and about 1 to 2 hours for LiFePO4. But with lithium theres a further complication.

We use 8 in series. So we must balance!!! So the FIRST of those 8 that reaches CV starts its soak time sooner, its absorption time, sooner than the last cell to reach CV. This is why its important to balance fast, to try to make sure all cells spend a similar time at CV. If you spend say 1 hour balancing, then the full cell spends 1 hour extra at CV. So it is "more full" than the others when charge ends and its voltage drops off less after charge ends. So if your lithium pack wasnt well balanced, or if balance current is too low, then you need to add more CV time... To ensure ALL cells get full. By lowering termination current.

[expresso]

BM - i am recharging my bounder now - and had it set to monitor with the PL 8 like i did the first time - But for some reason this time - its not showing me the Cap in ? i wasnt getting that info..

so i stopped the charge - and restarted it with the PL 8 preset - it was running about 30 mins - before i stopped it - restarted with pl 8 alone -

i am curious to see how much was used - first time out with the chair and my ADD ON - its Much better for sure - 26 mile ride - mostly flat though - JS number was about a 9 first 18 miles while in use - then i stopped to check my phone etc, - settled down to a 7 - i continued to do another 8 miles - i has hit a 6 - but back to 7 if i could ride another 10 miles before settling on 6 solid - then it may do a good 40 miles -

it will be different when i do hills - next time i will try to hit 30 miles and check the recharge - but why did the preset this time on monitor didnt show me any info. ?

[Scooterman]

What does CV achieve?

Think about a battery as a resistor. Because it is also that!

If you take any battery at a low voltage. Say a LEAD battery, its all the same. Its dead, flat, exhausted at 11V. If you set a power supply to say 300A and 14.4V max, and connect the battery, in 2 seconds it reaches that CV voltage. Is it charged?

Obviously no! Take away the power, and the voltage drops back to 11V after say 8 hours. And its now 1% charged...

If you LEAVE it at that 300A CV for a while it will still be at 14.4V and the amps will gradually tail off. And become lower and lower. Eventually it reaches almost zero Amps. Now, it has soaked up that power. So now when you release the charger cables, and wait, it will fall back to the FULLY CHARGED voltage of 13.15V. This takes 8 hours approx on a lead battery at CV.

Lithium has a much lower resistance and zero Peukert to speak of. So it can be fully charged in as little as 3 mins CV for LiPo, 20 to 40 mins Lithium ion, and about 1 to 2 hours for LiFePO4. But with lithium theres a further complication.

We.

Thank you John that is so helpful, I really appreciate it
I see now that if a cell/s have high resistance then they can't absorb the charge current as easily so their voltage shoots up, but they're a long way off charge. Whereas a low resistance cell/s can easily absorb the charge current so the cell voltage stays low until the point when the cell is becoming full, can't absorb the charge current so easily, and it voltage rises. That makes perfect sense to me. When I was a child I built a power supply but I could never understand why it could power a small lightbulb and voltage stay high (high resistance), but if I put a heavier load on it (low resistance) the voltage would disappear. It's a similar principle.

And different cell chemistries have difference internal resistance, I get it.

We use 8 in series. So we must balance!!! So the FIRST of those 8 that reaches CV starts its soak time sooner, its absorption time, sooner than the last cell to reach CV. This is why its important to balance fast, to try to make sure all cells spend a similar time at CV. If you spend say 1 hour balancing, then the full cell spends 1 hour extra at CV. So it is "more full" than the others when charge ends and its voltage drops off less after charge ends. So if your lithium pack wasnt well balanced, or if balance current is too low, then you need to add more CV time... To ensure ALL cells get full. By lowering termination current.

This is a bit more tricky for me, but I will stick my neck out and have a go...
The idea is get the cells balanced as quickly as possible so they don't have to remain at CV for so long. That's why we set the balance speed to x16. AND it's bad to leave nicely balanced cells too long on CV stage. Is that because the cells are already balanced and the CV phase, is precisely that, it's CV and DOESN'T BALANCE the cells. So because of the inherent nature of lithium balanced cells will tend to go out of balance if left at CV too long.

Now for cells that take a long time to balance we need to keep them at CV longer.

So if balance phase takes 2 hrs and you terminated the charge without going onto CV then the strongest cell would be 2hrs more saturated than the weakest cell. So the strongest cell has been absorbing at CV 2rs longer than the weakest.

So by adding say a 3 hr CV phase the strongest cell would be at CV for 5hrs, and the weakest at CV for 3hrs, so the percentage difference between the amount of absorbtion at CV is less and the cells should hold their balance better during their discharge cycle.

Sorry if I've repeated some of what you said, it helps it get clear in my own mind. If I've screwed up, pleased correct me I don't mind.

[Scooterman]

BM - Have I marked the correct stages on this graph?

[Burgerman]

The bit marked balance is the CC stage where voltage is rising. Balance starts about 3.5V and continues to the end.

[Scooterman]

The bit marked balance is the CC stage where voltage is rising. Balance starts about 3.5V and continues to the end.

Yes of course! Thank you for that.

It really helps you clearing things up for me. It's important for me to 'understand' rather than just mimic parrot fashion. Because if I run into problems in years to come and if especially yourself (or others aren't) around, I'm screwed. You can't get yours (and others) level of knowledge of lithium (and powerchairs) in other forums.

[Burgerman]

Always. Learn. Knowledge is power. You MUST know how everything works. If I ever find a thing I dont understand completely, it drives me nuts. I will spend hundreds to buy a thing and take it apart if need be, just to find out. Been that way all my life. Still am! I am a sponge that loves to soak up knowledge.

Took my dads petrol mower apart to its smallest component when I was 10. Every last part. Not the mower, just the engine and its auto clutch. Because I just wanted to know what made it go. Back together again, too. Took me days!

But I learned stuff. E.G. That simple carburettor for e.g. It showed me how and what it did, how the various Jets and air bleeds inter-reacted. How the float chamber level worked, how the idle mixture circiut and emulsion tubes worked. Showed me what the main air corrector jet did. And why it brought the mainjet into play earlier when float set higher. Etc etc. Later in life with big drag bikes, and huge V8 carbs etc I was a go to man to sort out carburation issues. They all work the same. More or less. I have a feel for setting up fuel systems and carbs that is just natural. It allowed me to set up carbs or fuel injection from scratch quickly and accrately because I understand what every part of a carburator does and why. Everything you learn is useful.

[shirley_hkg]

We usually set Balance Start V at 3.5, so balance starts here and till the end .

Charge is still going with full throttle .

When voltage keep rising and reaches Charge Voltage eg. 3.58V , PL8 will keep no cell beyond this by manipulating the charge current . It leaves the CC stage and enters CV stage now .

Absorption period may vary . It depends .
CV timeout or Terminal current will end the charge , whichever comes first .