msx pro, bricked M50 packs and fried controller

[alcatraz]

What cells are you using to replace the bad old ones?

Edit: Just read your comment on youtube. So you're building an 18650 pack to test the BMS.

Edited March 17, 2022 by alcatraz

[goatman]

im putting samsung 30Q cells that i have salvaged in it  for now and the other side im putting in some sony vtc6 but i need to increase the diameter of the cell holder holes by 0.2mm to fit the slightly larger sony cells.

i want to know whats up with these bms' 

 planning on P42a-21700 with active cell balancers.

i can get the 40T3 for a little cheaper but they are a warm weather cell, great for summer but not winter.

you get an extra 400mah from a P42a over 40T3 in winter.

4p=1.6ah

and not as saggy in the cold

[alcatraz]

There are many options to get high current and high capacity at a good deal, one way is to go 18650 and go 24s3p with high capacity cells. 

Sanyo/Panasonic are really nice 18650GA or 18650PF (affordable). LG MH1 are very affordable.

For bms you can try to hook both packs up to one bms. Gotway or third party. Third party you can pick one that's smart with bluetooth. If you want to be able to monitor voltages using the original you can attach balance leads.

[alcatraz]

Ok, to be honest I don't know the prices globally. It could be very different over there. 

In China it's crazy affordable to get cells that have been salvaged (like from crashed vehicles etc). You can get all the exclusive kinds. Problem is if they aren't matched you're going to need a quality bms with good balancing currents.

If you intend to use the gotway bms then you really need matched new cells.

[alcatraz]

By matched I mean that they come from the same batch.

(Obviously they should all be the same model.)

[goatman]

i couldnt jam 24s3p-18650 into the same space as the 24s2p-21700 unless i got rid of the speaker and alarm 

30q and vtc6 are perfectly fine to parallel together as separate packs

 

to do both 24s packs on 1 bms you would need to run 25  balance wires to the other side of the shell. then if 1 cell went bad in any of the 2 packs it will wipe out both p-groups leaving you stranded

 i dont like BMS', i call them a Battery Murder System, i prefer active cell balancers

when i talk batteries, i dont talk in general, i talk specific cells because they are all a little different

do you people know if the control boards are using regen or plug braking for the braking and reverse function of the euc?

[RagingGrandpa]

1 hour ago, goatman said:

know if the control boards are using regen or plug braking for the braking and reverse function of the euc?

For me, "regen" means briefly connecting two motor phases together to cause the phase current to rise, then dumping the voltage flyback from that big pulse of current, into the battery pack.

"plug braking" means driving the motor in reverse, by applying battery voltage in the same direction as the EMF. Once the motor speed reaches zero, this is simply "reverse drive" and the motor will accelerate in the reverse direction. 

EUC's do both, selected by firmware according to speed and load.

[Planemo]

2 minutes ago, RagingGrandpa said:

EUC's do both, selected by firmware according to speed and load.

I'd be quite interested in learning how the braking process works. It seems so simple that most dont think about it when riding, but I do wonder at what point the MB decides to regen or plug. I appreciate your load/speed comment makes it pretty variable but the transitions are totally seamless which amazes me. I know nothing about the process given my only other experience is with ebikes and they don't use motor braking.

[goatman]

 on my ebikes with phaserunner controllers you can feel the switch, braking gets stronger, at about 10km/h

on a side note, those controllers start sensored and switch to sensorless at about 10/15 km/h or about 10 meters, if the settings are off a little you can feel the switch. when the S20 was cutting out in the first 10? meters thats what i thought was happening to the S20

had to change the throttle torque ramp up rate from 50 milli-seconds to 20 m/s

you can read about it in this post

https://endless-sphere.com/forums/viewtopic.php?f=49&t=111861&p=1659575&hilit=vibration+spine#p1659575

Edited March 19, 2022 by goatman

[goatman]

started assembling the batteries

0.1mm copper and magnets

 

i give a light coat of plasti dip and then 2 more heavy coats,

locks everything in place, waterproofs and insulates

[alcatraz]

Are magnets the only thing keeping the copper strips on the poles?

[goatman]

yes, been using them for awhile, ive used them up to 15 amps max but should be kept to 10 amps max on the 7.5mm ring magnets

ive never used them on vtc6 til now, typically the positive end of an 18650 positive is 8mm dia. and convex so the inner 2mm dia circle of the magnet is where the main contact pressure is

but the vtc6 is concave with 3 high points on its outer diameter

my battery guy is getting a shipment of p42a cells mid may so ill be using these until then

 

edit, anyone knoww where to buy the cell holders for 900wh battery packs?

Edited April 4, 2022 by goatman

[alcatraz]

Be careful of heat buildup, from poor contact.

[alcatraz]

Can that plastidip withstand the heat generated at the contact points? Do an inspection after a few rides.

[Planemo]

3 hours ago, alcatraz said:

Are magnets the only thing keeping the copper strips on the poles?

I must admit, the use of magnets to hold on the interconnects scares the hell out of me. That said I've never tried it.

[alcatraz]

Let's assume the contact isn't ideal. If not now, maybe in the future after light corrosion has developed etc. 

The resistance combined from all the contact points is going to add up. That means heat, when you try to run a current through. It also means you have a lot of internal resistance in the power source. Which means that more voltage will be lost internally when you close the circuit to take out power from the pack.

I think it will behave as if it had a ton of voltage sag, plus heat.

[alcatraz]

Also, what's the chance of the plastidip from creeping in between the contact points? Capillary effect or whatever it's called.

[alcatraz]

I'm not trying to be a negative nanny. I think it's a cool idea. Just be careful when you're putting current through the pack. 

Voltage sag can lead to a cutout, but heat can lead to fires.

[goatman]

done lots of testing and usage, no corrosion after a year (no oxygen)

ive been using them for about a year on my other packs using copper slug tape and 7.5mm magnets

had trouble with 5mm square magnets , you need the circle in the middle

if theres a bad connection it shows as a p-group out of balance, like a spot weld does

also when doing lifecycle testing of batteries id use the plasti dip and magnets with no issues after 500 cycles

heat isnt an issue, they run at the same temperature as the cell

tried heavy duty reynolds aluminum foil, that runs hot in comparison to cell temperature. actually alot hotter

i thought aluminum foil would run cooler than nickel but theres iron and silica in it

id be more worried about bad spot welds on nickel strip than the magnets

the majority of dead packs that ive salvaged cells from, were bad spot welds

[goatman]

got a new board

 

its completely different in the lay out and after looking at it for a bit

i dont think i need this board anymore

 

just unplug the wires from it and plug them into the main control board

i think i saw a diagram that labels what plug goes where on this forum somewhere

 ginger on wheels at 8:20 but it should be time stamped for diagram

 

just need to solder up the bms and see if its any good

 

Edited April 10, 2022 by goatman
add video clip and bms pic

[goatman]

battery and bms are finished, nothings getting warm, voltages are fine

the blue and green phase have been reversed from the original board and the phase wires dont really like that

was kind of bracing for some violent shaking when i turned the wheel and lifted it but it works just fine

need to shrink the packs then see if vba tape will hold them in place

and then extend some of the wiring harness connectors to fit the new board

 

[alcatraz]

Nice. If those bms' aren't damaged then this could be ond of the  few MSP that will stand the test of time. 

How about soldering some balance wires to those packs, so you can monitor them...

[goatman]

the vtc6 pack and bms seem fine, heat shrinked and connected to the wheel, theyre sitting at 91.5v

the 30Q pack and bms not so much from the 13s parallel group to 24s parallel group

that whole side has dropped from 3.05v to 2.95v

from 1s to 12s theyre holding steady

its not connected to anything

just sitting on the work bench

nothing is warm on the bms????

 

i was only planning on using these packs for a month til my other packs are ready

any problems with the leaperkim bms'

need to source cell holders and new bms'

Edited April 11, 2022 by goatman
pic

[alcatraz]

Good you noticed. Some people just measure a few hours later and heatshrink it all up, dust themselves off. Then a few days later, fireworks.

It can't be the cells when it's so many groups. The bms must be doing something weird. 

[alcatraz]

Another thing worth testing is the communication between packs. Have a cell group slightly higher charged and monitor it when the wheel is on the charger. Make sure the charging gets cut off before it goes over 4.25v.