battery capacity

[dutchcyclingman]

how to messure the battery capacity

i have discharged it with a light bulb and messured voltage and current and time

current from 5,3amp to 4.6 amp voltage from 41.6 to bms schut down but time was only 2.5 hour
so thats only about 12,5 amp/hour 
i have a 16 amp/hour battery

or is this not the way to messure capacity 

thankx gerrit

[Leslie]

You have to do this test with a  1 amp load and then see if you get 16 hours.

A 5 amp load about near LVC will create a slump.

4.6 amps is quite a load on a dead battery.  A 12ah battery should be lucky to ride you a little more or less 1 hour easy going.

This is why its called AH (amp hour) and not amp .2 hour.

If you are going average 32kph this is a 32km ride.  That is about right for a 12ah lithium battery.

If you average 38kph, this would mean less stops and starts, yo9u may be lucky to push this.

If you get 22kms and shes dead then your capacity is suffering.

On many sites lifpo4 12ah bateries say you should ride for 35km average before LVC.

And LVC stops you from getting full amp hours anyway to protect the battery.

Your battery seems good to me.

How far can you ride?

[dutchcyclingman]

hallo 317537

average is about 34- 36 km/h [55min-33km] maximum distance on one scharge  about 50 km
but that depends on the load 

with windforce 8 in front it lasts not more than 40 km and average is down to 32km/h

was a little worryd about the 12,5 amp/h for a 16 amp battery

wil try for the 1 amp discharge  need a 36 ohm resistor to do this  or 3x12v-10 w bulbs 

[Leslie]

40~50kms?

That's awesome capacity for a 16ah battery.

Again I am sure your battery has optimum capacity.

Be careful with the 1ah test because draining them slowly in such a way the ebike bms is not designed to protect the lithium in this fashion.  The ebike BMS usually is designed to LVC with higher loads and you may over draw the capacity too close to the cells capability.



It should be fine but really you should be satisfied with the first test with 5 amp load.

Remember LVC is supposed to cut you battery from draining 16ah from the battery if you were to get 16ah from a LVC protected 16ah battery then I would class this as a 20+ah battery.  Remember 16ah running time on a 16ah lithium battery = dead battery, caput, finished, zero more cycles po0, Deathpo0 ..

It doesn't make sense to get 16ah from a 16ah LVC protected lithium battery.

LOL.  A dead LiFePo4 = Po0.

[GM Brazil]

This is very useful and relatively cheap: http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=10080&Product_Name=Turnigy_Watt_Meter_and_power_Analyzer

And this is veeery cool for battery testing: http://www.powerwerx.com/tools-meters/computerized-battery-analyzer-3-cba-iii.html

But just if you are a dealer, or RC enthusiast, etc.

[Leslie]

Do not do the 1 amp test unless you watch it closely.

It's just I think I remember have read some warnings about this on other forums.  Usually my long term memory is very good.

I think 16 hours is a long time to watch, and the battery will go into LVC and out of LVC. On, off, on, off until your battery is finished.  You must watch it with such tests and turn it off on the first LVC event.

[dutchcyclingman]

found this one on ebay 

http://cgi.ebay.nl/ws/eBayISAPI.dll?ViewItem&item=300374546418&ssPageName=STRK:MEWAX:IT

http://cgi.ebay.nl/ws/eBayISAPI.dll?ViewItem&item=370293256032&ssPageName=STRK:MEWAX:IT

i am a little worried about the extra wiring 

[dutchcyclingman]

can we use RC batterys for powering our ebikes   

http://cgi.ebay.nl/ws/eBayISAPI.dll?ViewItem&item=120500776287&ssPageName=STRK:MEWAX:IT

[GM Brazil]

The batteries GM use is kind of a big version of these.

But the problem is that RC batteries use LiPo and they are dangerous (can explode) and difficult to maintain. Need an expensive recharger, etc etc.

Because of this even in RC they are changing to use LFP batteries too (you can find them to buy)

I did not calculate, but to have the same capacity, You will need a lot of RC packs, and can become more expensive...

Resuming, yes you can, but it is not recommended to use LiPo!

[Leslie]

can we use RC batterys for powering our ebikes  

http://cgi.ebay.nl/ws/eBayISAPI.dll?ViewItem&item=120500776287&ssPageName=STRK:MEWAX:IT

Sure Lipos are great and as stated above very dangerous. You should rest and cool before charge and before use after charging.

BMS and chargers for these sizes are not standard so you either have to build one or have one built.

Some places do sell both lipo chargers and BMS's. Many have used lipo tool batteries with great results.

Some lithium chemistries in these types are of the highest discharge and energy densities than all other batteries.  You would need 10 of these for a 55v 20ah pack.

Separate all packs in case of thermal runaway and get a lipo safe pouches for each cell block and BMS and you will be safe enough.

Shipping can be expensive due to the safety risk.

They should last as long and under high loads they should be more robust than most other packs.

The fires these have caused burn whole factories down to the ground.

Here are some good vids that show what happens when things go wrong.

http://www.youtube.com/watch?v=gSgjj6NT5U8&feature=related

Watch it through as it shows the lipo safe sacks in action.

Some of these tests are done on 2ah batts.  Think about an event 10 times this size and you will understand why only very knowledgeable enthusiasts usually only play with the devil of all batteries.  

[Leslie]

Lifepo4 is the safest of all chemistries as far as I know.  Even safer than Lead acid, nimh, and NICD.