How to know if my Lithium Battery Pack is bad

[ElbadoKing]

I recently got my Daymak EM2 upgraded from a 72v/20ah lead acid to a 72v/30 lithium. I ride without the governor mostly. I noticed a slight increase in torque, speed, and distance. I was expecting more from this upgrade, how would I know if I got ripped off with my lithium pack.

 

[john61ct]

Exactly what model cells comprise the pack, and were they new, fresh, grade A and genuine?

Capacity test, precisely timed CC load test between 100% Full and say 3.0Vpc

Also resistance.

See how fast those two benchmarks decline every 50 cycles or so.

 

[ElbadoKing]

Sorry im not really savvy with the terms you used. Is there any way I could tell as a beginner.

 

[goatman]

you can get a watt meter and plug it inline between the charger and battery, then when you charge your battery the watt meter will tell you how many watt hours or amp hours you put in

 

[john61ct]

Sorry im not really savvy with the terms you used. Is there any way I could tell as a beginner.

Sure but you're guessing just using common sense "feels OK to me" judgment.

To really know the objective numeric reality of their condition / quality compared to the specifications you were promised,

you need to put in a little effort educating yourself and spend a bit of money on measuring instruments.

Which everybody should do who wants to avoid getting ripped off by the scammers and ripoff merchants,

which in some product categories and source locations might be 99% of the vendors.

Especially for those shopping based on price.

 

[jimmyhackers]

checked their website, never seen them before, looks cool.

only problem i saw was the motor rating at 500w. i will try to explain/help

essentially a 500w motor will only ever draw around 500watts at its rated voltage. it will only ever ask for 500w

so if your old lead acid battery could provide says 600w and your new battery can provide 2000w your motoor will still only ask/use 500w.

the increase in torque,speed and distance youve seen will probably be mostly atributed to weight loss (lighter battery) and less voltage sag (slightly higher top speed)

you said a 72v20amp hour lead acid and a 72v30amp hour lithium?
from thier website its a 30amp hour lead acids, are you sure you didnt start with this and then get a 30ah or 20ah lithium?

either way....you shouldnt notice much difference in range between a 30ah lead acid pack vs a 30ah lithium at that 500w (7amps) discharge rate.

 

[john61ct]

essentially a 500w motor will only ever draw around 500watts at its rated voltage. it will only ever ask for 500w

This is 100% wrong.

Go look for Justin's blurb about motor ratings at the Grin site.

 

[jimmyhackers]

its really not that wrong.
its usually the motor manufacturers ratings that are wrong really.

the manufacturers website says 500w....so i assume a 500w controler and a 500w hub motor. but i suppose the motor could handle more power.

that is why i said "at its rated voltage" and "around 500w"

what i kinda did that was wrong was not mention that also applies a lot moreso to the chaps exsisting "500w" controller.

if the lead acid could provide the 500ish watts the controller was asking for swapping to lithium you wont see much difference either as a result.

there is potential that swapping the controller for say a 72v 1000-2000watt unit....would most definately yield results in torque/acceleration. but i wouldnt be so sure about a drastically higher top speeds.

for 40-100quid its worth a go. would give it the performance to match the looks. these work great. a 1000w unit should roughly double torque, 1500w triple and 2000w quadruple.

https://www.ebay.co.uk/itm/48V-72V-1000W-Brushless-Motor-Controller-Electric-Bicycle-For-E-bike-Scooter/391045522309?hash=item5b0c212385:gRoAAOSwcgNZCal6

https://www.ebay.co.uk/itm/48V-72V-1500W-Electric-Bicycle-Brushless-Motor-Controller-For-E-bike-Scooter/392028785293?hash=item5b46bc8a8d:g1YAAOSwSata4aA-

https://www.ebay.co.uk/itm/72V-2000W-Electric-Bicycle-Brushless-Motor-Controller-For-E-bike-Scooter/392029317457?hash=item5b46c4a951:g:zpkAAOSw9uNa0lRx

they came within 2 weeks of ordering.