How can I test a battery's health

[TECH_GEEK10]

I have 36v 20Ah lithium pack that I have no knowledge of its past use. I am able to get about 5 to 15 miles on a single charge without pedaling at all, just constant 100% throttle with a 250w controller, geared sensored 350w? rear hub motor on a steel frame. I load the bike with 200 to 250 pounds and am often going up a semi steep hill. Anyone have any idea based on this info what the health of my battery is? If no idea than how can I test its health/age/total charge cycles with a multi meter and/or a genuine Imax b6 mini smart charger with usb logging?

My bike: http://arrowebikes.com/Home.html

 

[flat tire]

Discharge and note capacity of each cell block using your imax...duh.

 

[TECH_GEEK10]

How much capacity am I looking for?

 

[TECH_GEEK10]

If it is in need to be replaced that is.

 

[flat tire]

You're looking for 20AH (or the pack capacity or maybe 70% of it at worst) in any series combination which I guess will take a while with your imax so best discharge groups of 6s at once to maximize efficiency. This will take a while but give you a good idea of the overall health of the pack.

If you're looking to find bad cell groups you can go for a ride til the battery is close to needing a charge then measure each group with a multimeter. If one of your parallel groups is low in voltage it may have a bad cell or bad connection.

 

[neptronix]

^-- legit advice.

Do you have a cycle analyst, watt meter, or other device that can count the amp hours while you are riding? a simple indication of voltage sag during load can tell you a lot. Having the amp hours counted by a watt measuring device can tell you more. And if you really want to dig into it, a multimeter measurement of the voltage of each cell group in series will give you even more data on the health of the battery.

 

[TECH_GEEK10]

^-- legit advice.

Do you have a cycle analyst, watt meter, or other device that can count the amp hours while you are riding? a simple indication of voltage sag during load can tell you a lot. Having the amp hours counted by a watt measuring device can tell you more. And if you really want to dig into it, a multimeter measurement of the voltage of each cell group in series will give you even more data on the health of the battery.

I do not at this time but would gladly invest in one if it is available for under $30. Can you link me to anything?

 

[TECH_GEEK10]

also what per-cell voltage should I be cutting of discharge at.

 

[999zip999]

How old is your bike ? 5 years it probably needs a new battery. Run to cutoff check each cell looking for a weird low one. A lot of those bike use a cheapb generic Chinese cell. If buying a new battery make sure to get known quality cells. If they say Tesla like cells, run.

 

[neptronix]

I do not at this time but would gladly invest in one if it is available for under $30. Can you link me to anything?

https://hobbyking.com/en_us/turnigy-180a-watt-meter-and-power-analyzer.html

There ya go. Best battery analysis tool you'll ever buy, other than the cycle analyst