Page 6 of 14
Re: Rebuild BM2 green...
Posted:
01 Jan 2016, 01:31
by Burgerman
My cells have been sat in a box for 6 weeks awaiting recharge.
They were charged individually to 100%, 1000mAh accurately removed (taken out), then stored 1.5 month. 5A charge 25mA termination, @ 3.600CV.
Subsequent re-charge at 5A and 200mA termination current, @ 3.600V Gives me figures like this (this is 8 cells from 80 that I have.)
- Code: Select all
Cell Beep@CVpoint EndCharge@200mA Self Discharge mAh (Lost)
1 809 1038 38
2 789 1016 16
3 775 1002 2
4 756 997 -3
5 783 1024 24
6 896 1122 122
7 782 1019 19
8 788 1020 20
As you can see they all vary, and cell 6 varies more than I like. I ordered 2 extra cells. I may not use the 122mAh lost cell. This way I can assemble GROUP[S of cells that have the same AVERAGE self discharge. So they will stay in balance if unused for a while.
Re: Rebuild BM2 green...
Posted:
01 Jan 2016, 20:26
by Burgerman
The long boring process of building a 120Ah battery. Every cell group tested for same self discharge rates, careful planning so we get each cell the correct way around...
One at a time.
Re: Rebuild BM2 green...
Posted:
01 Jan 2016, 20:47
by Burgerman
This cell required the 1Ah removed, plus 16 extra mAh to be fully charged. So it had just 16mAh self discharge.
Re: Rebuild BM2 green...
Posted:
01 Jan 2016, 21:26
by Burgerman
The BLACK end is negative obviously. The other end is positive and silver. And vented. Dont use too long bolt here.
Re: Rebuild BM2 green...
Posted:
03 Jan 2016, 01:25
by Burgerman
- Code: Select all
PL8 charger used.
Charged individually to 100% 15mA termination 3.600v, then 1000mAh
accurately removed, stored 1.5 month in box a cupoboard.
Then, 5A charge 200mA termination, 3.600CV.
Subsequent re-charge gives us the amount lost through self discharge:
Cell Beep@CV EndCharge@200mA Self Discharge mAh (Lost)
1 809 1038 38
2 789 1016 16
3 775 1002 2
4 756 997 -3
5 783 1024 24
6 896 1122 122
7 782 1019 19
8 788 1020 20
9 690 990 -10
10 712 1104 4
11 725 995 -5
12 756 1011 11
13 813 1019 19
14 781 1016 16
15 815 1020 20
16 813 1023 23
17 819 1034 34
18 768 1008 8
19 777 1013 13
20 902 1120 120
21 761 1010 10
22 780 1012 12
23 802 1047 47
24 796 1015 15
25 760 1007 7
26 760 1018 18
27 0 44 44? Over full in seconds? This one wasn't discharged 1Ah...
28 800 1016 16
29 800 1016 16
30 748 1018 18
More done! 30, only 50 to go!
Re: Rebuild BM2 green...
Posted:
03 Jan 2016, 20:31
by terry2
Looking great BM(I'm jealous as hell)
Re: Rebuild BM2 green...
Posted:
04 Jan 2016, 04:58
by Burgerman
Well its hard work. Esp if you spend most of the time held up waiting for a carer to pick up that screw, tool, bracket, or whatever that you needed and you have been running over all day, or waiting for the post from china for some obscure tiny thing you cant do without...
I have a BM3 with a failed Cush drive rubber I need to fix, so cant use it. But cant fix it because I have a BM2L (lithium) in the way covering every spare bit of space in 200 bits and pieces.
But don't watch. Get the hammer out!
Re: Rebuild BM2 green...
Posted:
04 Jan 2016, 05:04
by Burgerman
Anyway, my mates are so used to me turning up with new chairs they no longer go wooo! They don't notice.
That's why I did polished alloys, fat low profile tyres, Kawasaki green ultra bright welding mask paint, orange/blue battery etc. This one was meant to stand out. Might fit a bright coloured car race seat yet!
I am normally of the opinion that chairs should be neat, clean, and go unnoticed. So black and dull and invisible.
Re: Rebuild BM2 green...
Posted:
08 Jan 2016, 22:18
by Burgerman
Here's one I made earlier. 80 12Ah cells, split into 2 packs, for easy lifting of uneven size and obscure shape to allow some parts to be 7 cells deep while others are 5...
120Ah and still 50lb lighter than a couple of lead bricks.
Looks odd. Fits great. Will allow HUGE range and uses up space wasted under the seat to the millimetre.
Re: Rebuild BM2 green...
Posted:
09 Jan 2016, 22:35
by motoman
Burgerman wrote:[img]
This pic is actually after a mid air collision with a Cessna I believe
Nomex undies and ear plugs would have been ineffective
Re: Rebuild BM2 green...
Posted:
09 Jan 2016, 23:06
by Burgerman
Everything would be ineffective!
Re: Rebuild BM2 green...
Posted:
15 Jan 2016, 15:36
by Burgerman
Built, cells carefully selected into 8 identical groups, so that they have equal self discharge rates, capacity, etc.
And under test. Wiring will be tidied up and cable tied. This splits into 2 halves.
80 Cells, 120Ah, 3000 plus watt hours, all cell groups selected after 6 weeks for similar self discharge rates, and for Ah capacity. This is under test.
Re: Rebuild BM2 green...
Posted:
17 Jan 2016, 21:36
by Burgerman
Tidied up...
Charge cable connected and testing. Just ONE connection. That black connector. One half stays on the chair, bolted under the seat. Other half stays on the charger. That connector has 9 balance wires, and 2 power wires. Safe for 40A charging.
It cant get any easier! The PL8 charger does a much better job of charging, with better control and information than a BMS. And the chairs controller does a better safer current and voltage control limiting than a BMS too. So non is required.
And apart from lasting a great many years, this battery is SAFE! Not all lithium batteries catch fire! These LiFePO4 cells are SAFER than your existing lead batteries.
Re: Rebuild BM2 green...
Posted:
18 Jan 2016, 00:23
by Williamclark77
Very nice! I wish I had known of those connectors before I did the Anderson and aviation plug connection to charge my 14s pack. It works fine but is three things to plug in. Simple enough but the aviation plugs are pretty annoying to get connected good.
What's the heavy red cable at the top for? The short one horse-shoe'd over. It looks to be making a parallel connection. I was wondering why it instead of a two hole plate?
Looks good! I'd like to see a real world range test when done.
Re: Rebuild BM2 green...
Posted:
18 Jan 2016, 01:21
by Burgerman
viewtopic.php?f=2&t=1813&start=620Part numbers, pictures of the correct connectors.
The battery is in 2 halves. Hence the link cables. Tried Anderson, has too much resistance and at 40A charge cell 4 shows 10mV too high... So solid cable link. And very tight bus bars. It even matters where you connect the balance wires. Can be 5mv difference from one end of a bus bar to the other...
Get it right and it looks perfect and the exact same voltage to 3 decimal places on every cell.
If you fit the cheap turnigy watt meter, you can find out ultimate range easily. With lithium as you already know, there's no Peukert. They run at full power to 99 percent. So you can measure actual Ah used, over a typical day, use your phone GPS to measure miles, and just do the maths. It will be within 1 percent. Range should be rather good. Lower current 6.2mph motors. Rounded profile 6 ply radial tyres have very low rolling resistance. Battery is lighter, chair is 100lb lighter. The stock chair claims an ISO 24miles from 56Ah Sonnenschein gel batteries. Which is bull but... With better tyres, less weight and a true 120Ah I should go at least 3x to 3.5x further. That's 75 to 85 or more ISO miles. Or real world about about 2/3rds that. We will see -- I am fat!!!
Re: Rebuild BM2 green...
Posted:
18 Jan 2016, 01:30
by flagman1776
I actually look at this connector... when I salvaged my generic China pack... was it 2+ years ago? Since I had already made up the Anderson output to the TravelScoot, I just reversed it as the main charge leads...
However, building a pack that doesn't get disconnected with every use, a single connector is so much cleaner.
What is the service life of the connector?
Is there a rule of thumb for getting the best balance reading?
Re: Rebuild BM2 green...
Posted:
18 Jan 2016, 01:39
by Burgerman
Service life? Unknown. But I can soon fit another. Looks pretty well made.
Its quite heavy gold plated. But even when that's worn away I don't see much of a problem. If there is it will show on the graph screen as uneven balance? But its proportional, and so will adjust for resistance changes on the fly... Cells all look pretty well matched here to the 0.001V level! (This Shirley, is why we don't use a BMS!)
BM2 one (2 connectors, as a 6S and a 7S pack at once).
And an 8S 120Ah discharge shows why voltage tells us nothing useful... Temperature varies the voltage far more than discharge level:
First charge so not completely together:
Discharge testing my quadcopter battery, through same connector while testing (only 3 cell, and all 3 well matched, this is LiPo so different voltages:
Re: Rebuild BM2 green...
Posted:
20 Jan 2016, 20:51
by Burgerman
More pics while it was in the kitchen... Bit of space.
BIG ONES!
Just ordered anti tip wheels (80mm black hard urethane inline skate wheels) and spacers, and bearings. And a 120mm M16 8.8grade bolt for the tie down. Those have to be fitted, tested for fit and angle befopre battery can be added as I cant get it up on the bed afterwards. Too heavy!
Re: Rebuild BM2 green...
Posted:
20 Jan 2016, 21:19
by hank
Should'nt be far away now John. Looking well
Re: Rebuild BM2 green...
Posted:
20 Jan 2016, 21:23
by Burgerman
Once the tie down bolt is in and the correct length, anti tips on, and battery in place then its all over. Just bolt the seat together. And then make a footplate (by a beermat drawing and a online laser cutter!) and drill a few holes etc to fit it. Then we can go for a silly mileage marathon!
At a narrow 24.6 inches wide its the same width as most 55Ah 22nf battery INDOOR/outdoor type chairs that use skinny tubed or rock hard flat free tyres with about 15 miles max battery destroying range like the Smaller TDX chairs, the Pride Quantum 600 and Edge chairs etc. Only with about 60 miles or 4x the range. And the ability to work properly outdoors without filling loss or the casters sinking in or high centering. Its also shorter.
Re: Rebuild BM2 green...
Posted:
20 Jan 2016, 21:29
by hank
Bet you cant wait.
Can see a roboteq nxt on shopping list.
You have speed in your blood still
Re: Rebuild BM2 green...
Posted:
20 Jan 2016, 21:36
by Burgerman
Well that battery can be reconnected for more series, less parallel, for more speed/volts with no loss of range or torque. And that will mean its 6mph motors, with larger diameter wheels, as fitted, will be a little faster anyway. So about 11 mph. So it does seem like a good idea.
Re: Rebuild BM2 green...
Posted:
26 Jan 2016, 15:30
by Burgerman
Battery testing complete.
Discharged by 50Ah and left for 10 days.
Recharge test, all cells remain in perfect balance, and 50Ah returned at 32A recharge rate in under 2 hours. Will fit battery on Wed.
Re: Rebuild BM2 green...
Posted:
26 Jan 2016, 20:28
by steves1977uk
BM, can you post pics of both sides of the battery pack please, so I can see how the balance wires connect. If I see rightly, you only have them connected to 9 places on your pack.
Steve
Re: Rebuild BM2 green...
Posted:
26 Jan 2016, 23:19
by Burgerman
Yes. 8S needs 9 wires...
I can take one shot of the other side, but the cell layout is very confusing!
1 - 2 - 3 - 4 - 5 - 6 - 7 - 8
Theres a wire at each end (plus 24V and minus or 0V) and then 7 wires on every one of those hyphens above.
Re: Rebuild BM2 green...
Posted:
27 Jan 2016, 21:04
by Burgerman
Tie down bolt...
Its about 1/2 inch too long! My tie down is correct when 2.75 inches or 3 inches to the shoulder of the bolt. This is only 2 here.
And I need to order a shorter one. I already waited 4 days for this... Note huge 24mm red spanner.
Re: Rebuild BM2 green...
Posted:
27 Jan 2016, 21:05
by Burgerman
And the PM is mounted to the alloy plate, bolted to the seat frame under the front. I am considering adding 2 computer fans...
Re: Rebuild BM2 green...
Posted:
28 Jan 2016, 02:41
by Burgerman
Looks a bit sad upside down. Like a dead bug.
Re: Rebuild BM2 green...
Posted:
28 Jan 2016, 13:51
by Burgerman
Checking wheel, tyre, run-out, balance & bearing seating etc, caster stem bearing preload, and finally adding the puncture seal. Because once you have there's no way to test balance for eg.
Run-out of tyre or wheel does make a difference. Caster preload does too.
Does balance "matter"? Not much if at all at 6 ot 8 mph. Unless its really bad and not central. But I use the same casters/wheel on my chairs and these are swappable. So these may end up on the 16mph chair. And then it does matter.
Re: Rebuild BM2 green...
Posted:
30 Jan 2016, 14:55
by Burgerman
Anti tips fitted. 80mm inline skate wheels. 8 new stainless steel bearings. Because the new 10 inch wheels are about 30mm higher overall.