Battery ADD on pack - First Attempt -

[expresso]

yes it seems like allen bolts - my camera is my phone and didnt come out good in the pictures - flash and lighting wasnt helping

but the color is a darker blue on some - some lighter in person - the dates are all the same - i was going to wait to get the next batch i ordered and then check them all at once -

i hope i get them this week - but not sure whats going on - i think they are still in HK - could be the holidays the reason

[terry2]

Can these packs connect up to MK Gel batteries(some how) to get extra distance?

[Burgerman]

Yes. Thats the point of them. But false economy if you just need new batteries. With healthy batteries they extend range by as much as you want. Depending on how many Ah you add.

[shirley_hkg]

It's all marked up.

Balance leads are screwed on as numbered ; 01 ---- 08 .

BMS has only =/- for battery terminals.

[expresso]

Ok - thanks - looks nice - simple enough once i know where to put those balance leads

Shirley - you added an XLR also to charge with slower charger ? also the Pos and Neg. cables - those have ring terminals also ? i am still waiting on my other 8 Cells - not sure what happened but they are still in HK

[expresso]

Ok - thanks - looks nice - simple enough once i know where to put those balance leads

Shirley - you added an XLR also to charge with slower charger ? also the Pos and Neg. cables - those have ring terminals also ? i am still waiting on my other 8 Cells - not sure what happened but they are still in HK

Found out - New shipping rules in 2016 - and my order was sent back to the shipper - they have to reship - hopefully with UPS and not DHL - always something - so i guess it wont even ship till next week - its not a big deal but still i want to have them already and check the volts - get started to do something -

[shirley_hkg]

Ok - thanks - looks nice - simple enough once i know where to put those balance leads

Shirley - you added an XLR also to charge with slower charger ? also the Pos and Neg. cables - those have ring terminals also ? i am still waiting on my other 8 Cells - not sure what happened but they are still in HK

All the other connections are completed already.

[expresso]

Nice - All i need to do is make a Cable to go from this BMS to my chair - Besides connecting all the balance cables and leads etc, - will be needing HELP to do that - to be sure i put them in the correct locations -

My order wont be shipped out till after the holidays - you will show me how to get them balanced first time ? is there anything else to connect to do that beside the balance cables - you said something about a DC to DC item ?

[Burgerman]

With a hobby charger, you just plug in charge lead and press go. That charges and balances solidly at 1A till all are done extremely accurately before ending the charge automatically.

With a BMS charge and balance are much, much slower... So I think Shirley is also sending a small 3.6v charger to do each group individually ??? Which will work, but take about 100 times longer.

Regarding your initial balancing, I'll include a DC-DC power module to bring up lagging behind cells to 3.6V.

One by one , though a bit slow.

Your money has paid for it.

[expresso]

I see what you mean -BM - but i believe i have to use the slow small charger just once to get the cells all balanced - and then can just plug it in and charge normally - leaving the BMS to do the job - hopefully good -

this is my first project - learning - -- i just want to understand it better - hoping to pick up on the understanding when i actually start to do it with my hands etc, - getting the guidence here for you and shirly etc, - so its done correctly safely and put it to use -

i am still not clear how i would balance each set - with the dc to dc thing - - if i understand correctly - i would plug it once all done and charge with my charger 8 amp or even 5 amp i have - slowly first time - then when done -

i would disconnect the balance plug off the BMS - and connect it to the DC to DC item ? and that would bring it fully balanced ? once fully charged - balanced the first time - then i wont have to do that any more and just plug in and charge normally the same way i am doing now -

i am close ?

[Burgerman]

>>>i am close ?

No idea. I avoid all the complication, wires, balancing problems, that BMS bring. I am sure that he will tell you how/why this will help.

Personally I would just plug the lot into my hobby charger and let it sort everything out/charge. One thing. If you store it a while, and the cells self discharge at a different rate as they do, you will need to do all this balancing thing again because the balance circuits in a BMS are very low power and can take literally days.

[expresso]

thats another issue - since the winter time - i wont be using it really - i havnt decided if i will connect it and try it out maybe - or leave it till the summer and then use it - if i do that - i should charge the ADD on alone about once a month ?

i hope it dosnt takes days to balance it out for real - its a small pack - 16 cells - i like to have it done in a day at least so i can watch it etc, -

once done - i can charge once a month during the winter if i am not connecting it to the chair ?

summer time i can leave it on the chair since i use it - and charge daily leaving it on the charger as i normally do till i am ready to use the chair

i am sure i will end up with a hobby charger at some point in the future - even if this works out and i hope it does - i will get one if i do a larger pack or whole chair - or if i find this to be too complicated or too slow - all depends -

its good practice for me to learn -

Looks nice and simple - giving it does the job - and charging balancing works out - i dont mind - at least for this Add on pack - your getting me worried now

[Burgerman]

BMS balance circuit typically 50 to 100mA if balance is a long way off. And they work either ONLY if voltage is at peak voltage. Or all the time (which is a bad thing and can put balance a long way out long term.

So lets say your 24Ah pack is 4Ah out of balance after being stored for a bit. To correct that, with a tiny 100mA balance circuit, will take 40 hours. plus charge/CV time. So 2 days on charge banging over the limit on the top cells. Charger cutting off/on every few seconds. If for some reason its more than 4Ah out, say 10Ah, it will take 5 days.

Hobby charger like PL8 is 1000mA balance and works at 3.4V upwards. So 5 hours for complete charge and perfect balance. No cell going over voltage, and everything controlled proportionally to 0.003v accuracy.

[Burgerman]

once done - i can charge once a month during the winter if i am not connecting it to the chair ?

These cells don't like being stored full. So that's not advisable.

Again, the PL8 can charge full, balance, in 20mins then discharge to say 60 percent for storage. Or can charge to say 3.38V per cell and balance. But its less important anyway, because it balances literally 10x the speed. So no real need, it will just rebalance in summer fix it fast as you charge.

[expresso]

i like that 20 min charge full -

so i would charge - balance full the first time i get this going and just leave it till i am ready to use it in the summer ? then charge again full balanced and - connect to chair - use daily -

i can just leave them sitting the whole winter - not charging after the first time - i say a good 3 months at the very least - if the rest of the winter is like what we are getting now - summer may come early enough to start riding sooner than expected with this warm weather so far -


40 hours to get back 4 ah ? whow - i hope thats not the case with mines -

[Scollard]

Again, the PL8 can charge full, balance, in 20mins then discharge to say 60 percent for storage. Or can charge to say 3.38V per cell and balance. But its less important anyway, because it balances literally 10x the speed. So no real need, it will just rebalance in summer fix it fast as you charge.

I'm with BM. A BMS needlessly complicates matters, is a point of failure, and is way slower than a hobby charger. With a PL8, or Hyperion in my case, and a combo Sub-D connector you have the simplest most powerful system. I'm building my LiFePO4 pack with that in mind. I have all my individual cells charge saturated and they are sitting for 1 month. Then I will determine each cells self discharge rate and build my 8 parallel cells so they self discharge as close to the same rate as each other. Then my Hyperion keeps everything in check.

Expresso, an answer to one other question you had: I did get an invoice from FedEx for Duty. It was only $20 so I just paid it rather than try and figure out how to import them tax free.

[shirley_hkg]

Whenever connecting 2 cells or 2 batteries together in parallel, you MUST check and ensure their voltages are nearly the same.

That takes some work.

I shall leave them connected and would not seperate them with no reason.

[expresso]

Whenever connecting 2 cells or 2 batteries together in parallel, you MUST check and ensure their voltages are nearly the same.

That takes some work.

I shall leave them connected and would not seperate them with no reason.

i understand - at first it will take some time to get them all the same or close as you can - each cell - - but after the first time i get it all done balanced etc, - you suggest i leave it connected to my chair as one and just charge normally each day i use the chair - ?

i dont get it - the charging procedure is going to be the same way i do it now - which is - i charge my chair and leave it on the charger for ever - i dont shut it off or take it off the chair - it just floats till i use the chair -

would that be ok once i add this pack to the chair ?

there are many days i dont use the chair at all - i may stay home in the winter time - and i dont use my outdoor chairs - i have another i just use in the home - the outdoor chairs i leave charging all the time till i use one or the other -
i may not use this chair with the ADD On - each day -

[expresso]

Again, the PL8 can charge full, balance, in 20mins then discharge to say 60 percent for storage. Or can charge to say 3.38V per cell and balance. But its less important anyway, because it balances literally 10x the speed. So no real need, it will just rebalance in summer fix it fast as you charge.

I'm with BM. A BMS needlessly complicates matters, is a point of failure, and is way slower than a hobby charger. With a PL8, or Hyperion in my case, and a combo Sub-D connector you have the simplest most powerful system. I'm building my LiFePO4 pack with that in mind. I have all my individual cells charge saturated and they are sitting for 1 month. Then I will determine each cells self discharge rate and build my 8 parallel cells so they self discharge as close to the same rate as each other. Then my Hyperion keeps everything in check.

Expresso, an answer to one other question you had: I did get an invoice from FedEx for Duty. It was only $20 so I just paid it rather than try and figure out how to import them tax free.

Thanks - at least it wasnt too much extra you had to pay - that was for 72 Cells ? not bad -

if i ever do the whole chair like you and BM does etc, - i will have to get the PL8 charger etc, - this is my first time and really dont know much - i know alot more now - but i already got this going with the BMS in mind - Shirley went out of his way to help do the BMS etc, - if he had good success with it - i dont see why i shouldnt either - i am not ruling out doing with out BMS in the future - if for some reason it fails down the line or i just dont like it for some reason - i can remove it and do it over with the PL8 if thats the case -

my goal when i decided to do this was - to

1. ADD on pack to extend range - something i can fit in my backpack - so everything looks the same - just a wire coming out of the pack going to my chair - i already have a wire on my chair at the rear -

2. I wanted to not make it complicated - and since i never used hobby chargers - dont have any - i though it was going to be complicated if i did it that way at first -

3. I wanted to keep it simple to charge - and figured if i could use my current chargers - that would make it simple for me - nothing changes much - i can plug it in and charge - same way as before - so this BMS is what will allow me to do just that -

so i decided to do it this way -

now that i am learning more about it - i see how the BMS Can be more complicated that just using the Hobby charger from the start - But if the BMS does its job correctly - or at least 80% correctly - lets say - it should be fine

but i understand how its another item in the middle of it all that can and will at some point fail - everything fails at some point - so not having it - makes it less likely to fail -

i had electronics for years - amplifiers for 10 years - still kicking like new - they can fail also and will at some point - - so the BMS can work fine for many many years - or can fail much sooner - or may not work correctly at all -

its a gamble either way - but i will let you know for sure - how it works out - if it works well enough - or if it fails - i will report back here about it - either way - and its no ones fault - what ever happens - i choose this way for now -

but i am getting worried more now - still excited to get it going and try it anyway - how great it would be if BMS works great - the way it should -

Happy New Year everyone -

[Scollard]

Expresso, there are a couple of 'gotchas' with a BMS that we have discussed before on this board. One is that the hobby chargers will balance the cells to within 5 mV or less, whereas most BMS's do not come to that accuracy. Shirley can tell you the specifications for his BMS. The other is the Cells do not like 100% charge so you can't just float a lithium pack. With a Hobby Charger you can charge 100% then take out 10-15% of the charge. I'm sure you can probably also accomplish this by charging to a slightly lower voltage. BM would know the answer to that question. But you must also be able to set the voltage in the BMS if you're going to charge to 90% SOC.

I didn't go with 72 12ah cells, my pack is going to be made with 56 15ah cells. It will be a 7p8s pack with 105ah.

Also, I checked all my cells before charging them fully. They all came almost fully charged and measured between 3.33 and 3.36V. They all took around 0.15-0.20ah to fully saturate. I then drew off 1ah so they wouldn't be at 100% SOC. In another couple of weeks I will determine how many ah they self discharged over the past month. I can then build my 7p cells so they self discharge at the same rate. The consequence of going to this trouble is to make it easier (faster) to balance the 8 cells because they all self discharge at the same rate so the individual cell voltages will stay very close to each other. Unfortunately you will not be able to do this with your pack, so if some of the 2p cells you make self discharge at different rates than the others the individual cell voltages will diverge and this will make charging take longer because the BMS cannot balance the cells at the same rate (amps) that the Hobby Charger can.

[expresso]

I understand now - i been reading on this over the web and found something that was understanding and showed pictures - so i get it now - it will take longer to charge - i havnt checked my cells yet - volts etc, - waiting on my other 8 Cells still in HK - didnt ship yet - most likely wont till end of next week i think -

So if i cant leave it charging floating like i do now with the Leads - i dont see how i can leave it connected to the chair and charge normally - it would seem best to charge the chair normally and charge the Pack alone on its own - so i can leave the chair floating on the charger and stop charging the Pack when thats full - and just connect it each time before i use the chair -

that makes sense to me if they done like to be floating charge - i dont see any other way if thats the case - if i want to keep it correct ? or leave it connected and charge the whole chair with the pack connected -

have to figure out which is best way -

i like that you can use 56 Cells instead of 72 - even though they are larger in size - i wonder if the 15Ah cell may fit better in my other chair - if i do the whole chair - thats the first thing i am going to do once i get the other 8 cells -

i want to check it to be 100% sure that i can fit 72 cells in my tray - with the blocks etc, - i still got this feeling it wont - i think the tray itself may limit it - may have to cut those orange block tips - or i feel even the height may be a problem - its very tight in my battery space -

if its really 14mm higher than a MK Gel - that may be a problem for me - but thats another discussion - i will wait till i finally get them and see for myself - will take pictures when i check it to post here - i already checked one cell and its just a little longer than the battery with the orange tips - will see -

for now - i am hoping this BMS works for me - since its a small pack i am doing - shouldnt be too bad to charge

[Scollard]

Well there are many ways to accomplish the deed. Look at BM, he's on Version 3.0 of his chair. You just file away all this information and when it come time for 2.0 you have a number of improvements you can implement.

I have an enormous amount of room. I have a Pride Pursuit XL. My pack will be 2 sets of 7p4s in a 7x4 configuration. I could make a 14p8s but to me it wasn't worth doubling the cost. At 105ah, of which most is usable, I don't have to worry about getting outside the sweet spot for LiFePO4. I'm still trying to figure out a slick way to monitor the usage. I found this bluetooth enabled 8S monitor that broadcasts to an iPhone but they don't seem to have any available right now.

http://www.flytron.com/icell/269-icell- ... nitor.html

I'm going to attach an 8s monitor to the combo Sub-d so I can see the cell voltages. BM, do you know or have you determined, the Voltage vs. SOC curve for these LiFePO4 cells?

[Burgerman]

I'm still trying to figure out a slick way to monitor the usage.

Turnigy watt meter. Count watt hours. Or failing that, less accurately, count Ah.

You *cannot* tell anything useful based on voltage. Other than its full. Or empty.

It remains much the same between 98 percent full, and about 20 percent remaining. The discharge curve is literally flat. And at high currents, it is reversed where voltage increases initially for 1/3rd the discharge. It even rises as it warms up. For the same reason a dumb BMS that tries to balance cells below 3.4v (and many try to do it all the time), actually spend all day incorrectly shunting power from the warmest cells to the coldest... Or just because they are not calibrated well enough. Or just those that naturally have a higher voltage to the lowest. And they may not *be* higher or lower based on Ah. Then when you recharge, it may be miles out of balance... BMS are great! If you sell cells.

It varies more between cells than it does by discharging!
Discharge curve -- check voltages. These have not changed since 98% full as I discharge the cells. If I put the house heating on it rises...

http://www.wheelchairdriver.com/BM3-con ... 0curve.gif

So:
I fit enough Ah that I will never run out.
And the roboteq is set to remove power at a very low voltage at which point the battery is at 100 percent discharged anyway to prevent damage. That only works with a lot of Ah and high C rate cels or voltage drop under load also cuts power (just like a dumb BMS/too small pack)

In adition the roboteq flashes the status lamp on my pod at about 80 percent discharged based on the algo in the script that lenny wrote. It doesent look at voltages under load. Only at rest and averages them over time.

And the hobby chargers count Ah back when you recharge. So you soon get an idea of how much or how little was left. So can set a simple alarm up to test voltage at the knee where it starts to drop to tell you to go home.

[shirley_hkg]

Just checked that ODYSSEY recommend a 13.6V float charge for PC1500. That is 27.2V which result in 3.4V per cell of the lithium pack.

That's way below 3.6 .You surely can leave the add-on pack connected to your chair all the way, even when your charger is in float stage for prolonged period.

LiFePO4 UPS is widely used in telecommunication industry. It can withstand long period of time in full SOC.

THAT'S why I always emphasize you don't have to change your driving and charging pattern at all.

We've been doing it for more than 6 years, and no adverse effects were found so far. Besides, it will extend lifespan of your lead battery too. I've mentioned that my pair of MK G24 was ten years old already.

[expresso]

Ok Shirley - - Sounds good if i dont have to worry much and just use as before - I have a few chargers - all different a little - i will be using the 28.8V charger for my pc1500 with this pack will be on - the float that charger i think is 27.6 or 27.7v

dont remember the specs - i have the manual somewhere - but in that area - would that still be OK - to leave connected in float after charger is in the Green -

Let me know when your done and ship it out to me - Please dont forget to put my APT. number on the package - i PM you with the details already - and if you can ship it UPS - that be great - -

what do you think of my backpack

[expresso]

Just kidding - thats not mines - haha - but funny

[expresso]

looking over some of the other chargers - the 20 amp i have floats at 27v and also the salmex so those both would be good also - and faster to charge - the slower charger at 5 amp also does 27 V float - and the 8 amp i think does 27.6 or 27.7V float - at 28.8V charge thats the generic one you get with the chair -

[terry2]

looking over some of the other chargers - the 20 amp i have floats at 27v and also the salmex so those both would be good also - and faster to charge - the slower charger at 5 amp also does 27 V float - and the 8 amp i think does 27.6 or 27.7V float - at 28.8V charge thats the generic one you get with the chair -

How are you going to connect the pack up to your gel batteries?(that's if you're using them).

I'm very interested in a add on pack as I have to visit a hospital twice a week which is a 25 mile round trip.
Yes we have buses here but I can never get on one as it has only one space for a chair or push chair

[Burgerman]

I have to visit a hospital twice a week which is a 25 mile round trip.

Seriously? I never found any chair that actually does the 20 or 25 ISO miles claimed.

Usually about 9 to 14 before you stop... Depending on batt size.

Connecting is easy. You hook them directly to the 24V battery system. Via any connector, usually Anderson or similar.

[expresso]

Terry - Yes you can do it also - and it will just connect to my chair - simple plug in - this is my first time doing this and i am learning alot here - 25 miles i think can be achieved - but it will all depend on your chair - the road you ride on - the condition of the batteries to begin with etc, - i can say for me - my chairs are power hungry and suck them up fast - and i can get a good 15 to 17 miles out of them - you want to be very close to home towards the end though - so keep that in mind -

now with the ADD ON - i cant say yet how it will be - but if all goes well - i think i can do 25 or close to it - i wont know till i do it - it will also depend how big a ADD ON pack you make - mines is actually a small pack - i just wanted to test it and see how it feels etc, - but even with this small pack i am going to do - i may be able to get an extra 8 or maybe maybe 10 out of it - which brings me to about 25 miles -

again i dont know just yet - hopefully by the summer i have this done and i can give real info on how it works for me - for me the whole point of enjoying the summer time is riding - not taking buses etc, - unless i have no choice or just tired that day -

i have a Pos and Neg. cable connected to my batteries which stick out of my chair - and thats how i charge my chair with a faster charger - i dont use the joystick chair charging port for that - you can still do so - and use the charger you get with your chair -

once the cables are made - this ADD ON - can just connect to that cable you made sticking out of your chair somewhere - and thats it - if you are like me - pretty much new to alot of this stuff - i would read this forum and get as much info as you can from reading so you have a better understanding of everything -

i started at first with just adding the cable and a faster charger - which is good also - but i realized if your outside with the charger - still not easy to find a place to charge and then even though its faster to charge - you still have to sit still for a good hour at least or two to be safe - so i decided the ADD ON may be better and replace the charger instead

MK GEL 24 batteries should be used at least - since they will give you the best range and are a quality battery - any other brand type etc, wont hold up as much - -