80Ah ADD ON build

[Scooterman]

Ok - i made all the cables - i want to test it before i tidy up the cables and pack it before i consider it done - so far so good i think -

It's tricky to differentiate the close colours on my laptop display.

But it looks like cell 2 the strongest and cell 6 the weakest. Is that correct?

[Scooterman]

so far i am really liking this pack - i will start testing it on Sunday Morn. - i am discharging it now for a few hours - then Sunday morn.. do a full Charge and full Discharge to 2.9V - will take at least 3 or 4 days with the PL 8 - - once done - i can see what the real pack Ah is - and the Volt limit i need to watch out when in use -

then full recharge again. and thats it - move on to the next step - Pack Should be done. set aside.

When you do a full discharge do you discharge into 2 x 12V = 24V lead acid batteries?

[Burgerman]

Are you talking about a full pack?

When you discharge a full lithium pack for a powerchair or your test cells, you do so as an 8S Pack.

You can then discharge each group, as a whole battery and watch which cell group drops to the 2.9V level first. You then know thats the smallest Ah group. So thats the one to watch as you drive... You can look at the total Ah you got from the pack when it stopped at that point.

You CAN discharge into lead batteries, as long as they are BIGGER than your lithium pack, and they are discharged when you begin. Or you can discharge and dump the energy as heat directly into the charger at up to 100 Watts. Or 10A whichever occurs first.

[Burgerman]

But it looks like cell 2 the strongest and cell 6 the weakest. Is that correct?

Thats just balancing an already charged pack.

[Scooterman]

Are you talking about a full pack?

When you discharge a full lithium pack for a powerchair or your test cells, you do so as an 8S Pack.

You can then discharge each group, as a whole battery and watch which cell group drops to the 2.9V level first. You then know thats the smallest Ah group. So thats the one to watch as you drive... You can look at the total Ah you got from the pack when it stopped at that point.

You CAN discharge into lead batteries, as long as they are BIGGER than your lithium pack, and they are discharged when you begin. Or you can discharge and dump the energy as heat directly into the charger at up to 100 Watts. Or 10A whichever occurs first.

I was talking Expresso's pack. It's a lot of amps to dump and I was wondering whether it's quicker to discharge into LA, plus it seems like wasted energy just letting the amps (I should probably say watts) dissipate to atmosphere as heat.

[Burgerman]

Heres the problem. Heres the problem. His ADDON has double the capability of 2x MKs.

He has 25.6 nominal volts x 80Ah to discharge plus say 10% headroom so he doesn't run out of somewhere to put it... 25.6 x 80 + 10% = 2,253Wh.

An MK lead brick, at best if discharged over a long slow period, like a full day, has 24 x 70Ah. (2 MKs) 1680Wh. Nowhere near enough.

At 40A discharge, that means you are recharging at the 1/2C rate. So it will go to CV after about 1 hour, and around 40Ah returned and then the discharge current on the lithium will fall to a low level as the battery charges at CV... Eventually the discharge will stop when the lead is full.

So that wont work. Realistically you COULD do it with 4x fully discharged MKs. But. It will still slow down towards the end. And you now have to completely discharge 4 MKs, which takes 20 hours.

I use a power supply and allow a day to discharge at 100W VIA the PL8 directly. I also have a 30A dummy load but lets not go there!

[expresso]

I have it discharging now - will do a full discharge of the Whole pack down to 2.9V - PL 8 is slow on discharging so this will take over 24 hours steady - sometime tomorrow afternoon - or a bit sooner should stop - and will then know the Cell Ah - and Pack volt at 2.9V and can use that to monitor when in use with volt meter

it wont be 100% accurate i dont think - when i use the volt meter - since its being attaching to the Chairs 100ah lithium - but either way its something you can monitor and watch and stop if you get near 2.9V - will have to wait 6 more months to try this out -

[Scooterman]

I also have a 30A dummy load but lets not go there!

No let's not!

I get it, good explanation

[expresso]

Ok the verdict is in - I have recharged full before starting a full discharge down to 2.9V - i am a bit disappointed i wont be getting the Full 80ah out of these Cells - they are solid and all seem fine - there will always be the weak one and it turns out its Cell 8 -

i was expected closer to 80ah when done - turns out its much less than 80ah if i stopped at 2.9V in use - End Volt is 24.5V - so that would be what i would need to watch out for with the Volt meter when in use.

here is the full charge before i started the discharge

[expresso]

This is where it was when i went to bed last nigh - i was expecting it to stop around 9am today - and i heard it beep around 6am - 3 hours shorter than i was expecting -

[Burgerman]

So how many Ah on the full discharge test?

[expresso]

When i got up and finally looked at it - it ended and Cell 8 was the lowest 2.9v the rest had some more juice left - so i am a bit disappointed i didnt get more out of this - but at the same time - they are all solid and working together nicely of course till the end. according to Seller specs etc, - the Cut off is 2.5V and no more than 2v to protect the cells from damage - how much more could i have gained if i followed those specs - who knows - maybe 10Ah or less - i am not going to stress it and risk damage by trying to get the last few Ah out of them -

[expresso]

So how many Ah on the full discharge test?

here is the graph from full discharge to 2.9V - i am a bit disappointed - but even this is about 30ah more than a 45ah headway pack thats a smaller footprint also - i would have liked to see more - - i am done for a while now - this will be added to the bounder 100ah - i had bounder here today to finish up on my chair foot hangers seat belt adjustment location and bracket to adjust my Joystick in more - should be good now - done -

[Burgerman]

Those are 70Ah cells. If you went down to damaging 2.5V levels.

At safe levels 68Ah. The Chinese lie...

Even so, a 70Ah addon is still almost the same as 4 mk grp 24s. So that should give almost 3x the range as the MK's alone if used with a diode.

Or on your bounder, a 70% range boost. In use dont go lower than 3.1V stationary. or rather 8x 3.075V = 24.60. So diode def needed for lead.

[expresso]

yeah i wont go past 2.9v - will make a volt meter for this chair also - and keep an eye on it - this ADD On wont be used with Lead - its goin on the bounder with 100Ah lithium already - if i ever used it on a Lead Chair - i have the diode in place already - which i can just unplug from one chair to another also

its hard to find a honest real lithium seller it seems - other than headways - maybe the site where you are looking at those 176ah Cells - maybe they are more honest - who knows - or the other site where they have those Sinopoly Cells - they have others- i just wasnt finding the Size i was looking for in a Cell - and this size was what i wanted so i got them - .

the most i can fit with headways are 45ah - so even though i am short from the full 80ah i was suppose to have - i am not complaining - it has to be an improvement for sure. the bounder guy was here today and hes interested in doing a chair also - hes making a 4 wheel drive Chair - to plow and do other things - wants to do lithium after seeing my packs - so i guess i be helping him

the bounder is all new to me with how there battery displays numbers - 10 being full which hits 9 after doing one block - and 3 being where you dont want to go or BMS will cut it off - i am curious to see how it acts with this ADD ON also - my friend got his bounder today also - hopefully we can take a spin this weekend - i am curious to see his speed on hill etc, compared to mines - hes got 10 which is where i may be heading.

[expresso]

they say - no lower than 2V - 2.5v is the cut off but no lower than 2v to protect them - but i wont go below 2.9V or 3v - 24.5v pack volt or even 25V

[Burgerman]

the bounder is all new to me with how there battery displays numbers - 10 being full which hits 9 after doing one block - and 3 being where you dont want to go or BMS will cut it off - i am curious to see how it acts with this ADD ON also

EXACTLY the same. Same chemistry. You will just go 70% further before each light drops.

[expresso]

if i can go 70% further - it may just do the trick - or at least give me enough range to enjoy the day and do my long trips - will have to test slowly for sure how far i can go and be safe

[ex-Gooserider]

I have a set of the hole punches that Scooterman linked to, and have been underwhelmed... They don't do that great a job, although it may in part be that it is a cheapo HF set...

My tool of choice for precise holes in thin stuff is one of the many variants of this:

https://smile.amazon.com/Neiko-02612A-M ... 0002T87CW/

Works on pretty much any sort of thin plastic, aluminum, copper leather, fabric, etc. It will even work on light gage steel such as electrical enclosure boxes....

It comes with a bunch of interchangeable die sets to make different holes from about 1/16" to about 1/4" diameter

It is mildly tricky to get the hole placement just right, so what I usually do is use a prick punch to make a dent at the desired point. The punch dies have a small point in their center, which will then fit into the dent....

ex-Gooserider

[Burgerman]

What are you guys doing?



And I use 15mm or 1/2 copper pipe out of the garage. Just cut a bunch of short bits to length with a pipe cutter... Flattened in the vice! Clean and shiny when using new tube. Easy to DIY.

I then put them in the drill vice 8 at a time, and use the pillar drill... Drill all at once. Drill 6 or 8mm. Debur with a countersink bit in my hand as copper is soft. You can do 8 or so in about 10 mins. You only need 7.

[expresso]

thanks - that hole puncher looks much better than the one i purchased and returned - i returned both hold puncher and blanks - Amazon is great for that - - i just ended up using the connectors i received - doubled up on them - and worse case - i would make cables from now on if connectors dont arrive with Cells

https://www.ev-power.eu/LiFePO4-small-c ... se-CE.html

i did find a connector here which matched the hole spacing etc, - i bet would be a perfect fit - but at over 5 dollars a connector - too much - but they look strong - and the Cells here look to be brand new and honest place - didnt have the size i was looking for - and didnt have these 60ah from what i recall when i was looking for them.

then later i found i noticed these and same size i purchased - i was upset a bit - but what can you do -

[expresso]

What are you guys doing?



And I use 15mm or 1/2 copper pipe out of the garage. Just cut a bunch of short bits to length with a pipe cutter... Flattened in the vice! Clean and shiny when using new tube. Easy to DIY.

I then put them in the drill vice 8 at a time, and use the pillar drill... Drill 6 or 8mm. Debur with a countersink bit in my hand as copper is soft. You can do 8 or so in about 10 mins. You only need 7.

that works for you who has all the tools needed talking about the connectors i wanted to get new ones - make larger holes etc, - i though i had it under control but hole puncher i got was a joke - too small a hole and not smooth clean cut - - blanks i purchased were perfect but needed a nice size clean hole which i couldnt do

i returned everything and just used what i received doubled up on them and thats it - works fine -

[expresso]

i decided to rearrange the Cells to make it as thinner in the plastic shoe box - turns out much more compact this way and saves 2 inches - will sit better behind the chair and not stick out past the chair itself - this chair is much more compact that i though - the rear is much more compact - dosnt stick out as i imagined it would.

i had to make a cable to connect the two halves - turns out - this may be the shortest cable in history i think - 8 awg wire - pack is done now - i have to cut up my plastic box to make it smaller thinner - not the best solution - cant seem to find anything better so i stick with what works at least

[expresso]

different views

[expresso]

very compact

[expresso]

this pack is more compact than just one MK Gel 24 - and twice the juice - - 2x range amazing lithium

[Burgerman]

Very pretty. New Yorks lithium expert factory.

[expresso]

besides my plastic box i put it in - dosnt look bad - too bad i dont have any more chairs to do - full packs - i want to do those 176ah Cells -

with this ADD ON - i would have about that much total - making it thinner - saved 2 inches - that makes a huge difference with how the backpack looks now -

i also added a strap to the backpack on the bottom which will wrap around the handles on the chair and snap together behind the bag - wont be seen and will keep the backpack near the seatback - making it look neater and more stable - i will also add my bungee cords also - it wont move when done and compact - wont stick out past the battery box -

next i have to work on the cable for the chair - using SB120 to get my 24V for the cable going to this pack -

[expresso]

Very pretty. New Yorks lithium expert factory.

thanks - its addictive - i wish i could convince others to do this - i would do it for them -

i have a XLR Cable to make the Volt meter - which is angled so would sit flush when plugged in and can keep an eye on the volts at least -

waiting the volt meters - ebay

[Gnomatic]

Nice job! Thats crazy capacity for an add on!