40T, neodymium magnets, plasti dip cycle test

[goatman]

tested overnight and once again, house cooled off and battery temp was 73f/23c when it started the 5th charge. im going to try and insulate the battery, its too cold.

im doing a test right now where discharge is 10amps to 3.5v then switches to 7.5amps to 3.0v in one discharge curve to see if I get more mah by discharging at 100% for half the cycle and when it switches to 7.5 im hoping when it cuts off the cell bounces back to 3.22ish?

I took a picture of 7.5amp discharge mah around 3.35v compared to 10 amp test above

 

[goatman]

I took the 16 gauge wire and splayed it radially on the 3/8 magnet, I need to go get some copper Permatex then do a test

 

[goatman]

heres the 10amp/7.5amp discharge

the data

combined capacity 3148mah
combined wh 11,149

 

[goatman]

got the copper antisieze Permatex, swapped out magnets and plasti dipped. the battery is charging then ill do a 10 amp discharge

 

[goatman]

heres the 10amp with Permatex magnets and 16 gauge splayed wire

volts after discharge

 

[goatman]

heres a question, I can run 10 cycles of the 7.5amp battery or 10 cycles of the 10 amp battery and will be ready tomorrow morning, which battery should I run?
the 10amp reached 107f on discharge and was still 96f when charge started, second discharge again 107f so I stopped it

im doing the 10amp to 3.5v then 7.5amp to 3.0v cycle test. its the test I think im going to life cycle

 

[goatman]

im doing another 5 cycle test but ive changed the charge from 5amp to 3.95amp

 

[goatman]

im losing 10mah every cycle so I ran it again changed charge to 3.95amps and paid attention to temperature on the discharge. 10amps the line got scratchy at 3.6v and temp reached 98f at 3.5v, when it switched to 7.5amps temp stayed around 96f til 3.2v then climbed to 103f by 3.0v

I made a change and the discharge temperature reached 92f

not much mah

ive made another change, charge is 3.75 amps

 

[goatman]

heres the new test numbers, battery temp was 73f/22.7c when discharge started and reached 83f/28c when it switched from 10 amp to 7.5 amp peaked at 94f/35c when it switched to 3.75 amp

total mah is 2865, wh 10.057

3.352v was when the charge started

I think this is kind of simulating a fast ebike ride cycle?

 

[goatman]

the last test was 10 watt hours. I run 17s4p at 2200 watts on the trike and 2500 watts on the other bike. 68 cells to the pack is
680 wh. I average 20wh/km, that's 34km range.
charged battery would be 17x4.12= 70.04v dead battery 17x3.2=54.4

2500 watts/54.4= 46amps/4p=11.5amps per cell
2500 watts/70.4=35.5amps/4p=8.9 amps per cell

2200 watts/54.4= 40.44 amps/4p= 10.1 amps per cell
2200 watts/70.4= 31.25 amps/4p= 7.8 amps per cell

930 watts/62= 15 amps/4p= 3.75 amps per cell

when I ride if im not going up a hill im going down a hill or stopped at a light

I use 10 amps from stop lights and steep hills.

I don't want a huge battery so if I can fully recharge in 80 minutes that isn't too bad.

ill cycle this setting a couple times and hopefully not lose 10mah/cycle

 

[goatman]

im running these settings through 5 cycles

emailed my battery guy for a new 40T but hes completely out, I figured id do the test with a brand new cell. theres a glitch in the chart when it switched from 7.5a to 3.75a on discharge. im just going to let this cycle for a couple days.

 

[goatman]

I didn't like the numbers, im new to this, so the problem is probably me, something im doing.

I changed cut off to 0.20a

I looked up the 40t charge specs

changed cut off to 0.16a

 

[goatman]

hopefully this means I get proper charge saturation and the numbers become consistent

getting better

checked battery temp at end of charge, 70f/21c. datasheet puts low temp at 23c so I put blanket back on box. temps changed when I changed the c/o settings. I want to keep the battery between 25c and 35c, see what happens

during discharge at end of 7.5a to 3.75a switch temp peaked at 98f/36.6c and steadily dropped to 92f/33c at end of discharge. charge started at 88f/31c. once charge reaches 4.12v@3.75a temp is 85f/29c and end of charge temp is 71f/21.6c. I could try turning up room temp but I don't want to run too hot on discharge. leave it and see

 

[goatman]

on the 7.5amp battery I had the copper electrode magnets but I switched to to splayed wire and copper Permatex, im going to test to see if theres any difference in the result

I like the magnet with copper electrode

heres the effects of temperature on neodymium magnets

https://www.stanfordmagnets.com/ndfeb-magnets-temperature-ratings.html


big difference in result, doing some tests to figure it out, this is the last numbers with electrode

this is the splayed Permatex magnet, battery was on cool side when started

im going to cycle the Permatex on this new setting with adjusted charge c/o to 0.13a

then ill pull the Permatex and try the electrode magnet again to see what the problem is

took 2 hours just to charge

changed the charge to 3.75/0.16 do another cycle then swap magnets and retest

The Vancouver sky hasn't been this clear for years

getting late, im going to cycle these settings overnight then swap magnets in the morning. takes 1.5hrs to charge at these settings

 

[goatman]

I have a question about charging.
I was surprised a 5amp charge/0.13a c/o took 2hrs, 3.75amp charge/0.16a c/o was about 85 minutes.

it makes me think a 3 amp charge with 0.175a cut off might be faster? would the saturation be as good?

 

[fourbanger]

Bookmarked for further reading.

Alls I knows is magnets aint so magnetic once theyses gets hot. What's to say of conductivity, I have no idea, except that as a rule of thumb resistance increases proportional to heat in a given conductor. Right?

Thanks to SM for the link from
https://endless-sphere.com/forums/viewtopic.php?f=14&t=60517

 

[goatman]

Bookmarked for further reading.

Alls I knows is magnets aint so magnetic once theyses gets hot. What's to say of conductivity, I have no idea, except that as a rule of thumb resistance increases proportional to heat in a given conductor. Right?

Thanks to SM for the link from
https://endless-sphere.com/forums/viewtopic.php?f=14&t=60517

I had this posted above but it was kind of hidden
https://www.stanfordmagnets.com/ndfeb-magnets-temperature-ratings.html

that is why im playing with the magnets, find a good method of using the magnet and then cycle test it, end of test, remove magnet and see how much strength is left.

 

[goatman]

went to bed and looks like when the battery switched from 7.5a to 3.75a the cycle stopped? I wonder what did that. when I moved my finger across the laptop pad to "wake up" the lap top the tester started and I got this chart with the cycle test resuming.

 

[goatman]

this is going to be a trouble shooting post ****Edit why did these pictures get big all of all sudden?****

i could see the glitchs happening but just wanted to get some results before I shutdown and restarted the program
finished 3 cycles on the Permatex

pulled the plasti dip and Permatex magnets and swapped the magnets

started the 4-1 charge and the numbers stopped showing on the sidebar but test is still running, ill take a pic of tester screen when charge is done. then shutdown and restart computer.

the blue line on right side of chart is where I swapped out the magnets, it only took 2 minutes but that's why volts went to zero.

 

[goatman]

I figure out the problems, you cant just swap out batteries. now I click disconnect com port, turn off tester change battery then turn tester on and click to reconnect com port.

the Permatex seems to be an issue also, I retested the 10amp battery and got same results as before

so I pulled those Permatex magnets and will try with electrode magnets and compare results.

 

[goatman]

this is copper electrode with 3.75a/0.16 charge to 4.12v

tweaked the settings to see if it will charge faster

about 40 minutes into charge when it switches to c/o amps, 2640mah

fully charged in 64 minutes :thumb:

 

[goatman]

heres the graph and settings, results. battery temp peaked at 93f end of 7.5amp discharge

this I tweaked a little to 4.15v, 70 minute charge. temp peaked at 94f end of 7.5a discharge c/o should be 3.4v to keep temp at 93f

I gave a 10 minute break between discharge and charge to lower the starting charge temp from 88f to 80f

 

[goatman]

I tried a setting for the 7amp battery where I was having problems. I did it on the 10 amp cell. ill switch batteries and run a slightly tweaked setting of this.

 

[John in CR]

How will all those little magnets affect the inductance of your pack? As I understand inductance of a battery pack should be minimized to the extent possible, eg keep the loop of wire containing the battery from the controller + and - terminals as small as practical.

 

[goatman]

How will all those little magnets affect the inductance of your pack? As I understand inductance of a battery pack should be minimized to the extent possible, eg keep the loop of wire containing the battery from the controller + and - terminals as small as practical.

that's a good question, now I need to go google what youre talking about

if i see packs with plates of copper or nickel for high amp packs, I wonder if that would be the same effect or tesla packs. I think ill go google it.

heres the 7 amp battery, I think the Permatex is a nogo but maybe less is better? Ill do a little testing today. to compare.

I also need a new 40T to start the test with.

doing a 5 amp charge and you can see the line gets scratchy at about 4.4 amps and 3.2amps. this is the first 5amp ive tried but ive seen the 3.2a scratch on other tests. im just thinking you might not want to charge at 3.3 to 3.0 amps. the charge took 52 minutes and 3107mah. im going to do a discharge at 3amps and see if battery temp gets higher than 88f. test started at 75f

I think I found a problem with the software, doing the test at 3amp discharge battery temps are steady 76f but the screen isn't recording mah this pic is 11 minutes in the test. temp peaked at 79f/ so 4.2 to 3.2v gave 3154mah

I cant even stop the test, I close the program and tester is still going :lol: i know i can program the tester to cycle test without the pc software so when i start the cycle test ill do batches of 50 cycles then do 1 cycle test on the software to post in the thread with the results.