I've just connected up my CA and wanted to check how the Ah reading works. According to the manual it says it shows how many Ah you've used since the CA was reset.
My battery pack is 16 x 3.2V 30Ah cells = 51.2V 30Ah = 1,536Wh
Does the CA take into account the voltage of the battery pack in working out how many Ah you've used? Do I just make sure the Ah reading on the CA doesn't get to 30?
Also I've got the high current model which uses an external shunt resistor. This is connected between the controller and the negative terminal of the battery pack. After some initial testing, the Vmin read 15V which seems very low. Is this an accurate reading of battery pack sag or could this be the controller acting like a transformer and stepping down the voltage when the motor RPM is low? I'm using an Alltrax controller.
Thanks!
Andrew
Amps and Volts are different things. Amps is essentially the number of electrons flowing by - volts is essentially how energetic the electrons are. Physicists probably just screamed and ran out the room pulling their hair out, though. In any case when it tells you amps that would be irregardless of the voltage. It's watts that is the combination of amps and volts.
What kind of current draw are you pulling out of the pack?
Unloaded does the cycle analyst record a reasonable voltage? e.g. fully charged this pack should be closer to 60 volts. If you use a multimeter to measure the pack voltage directly, does it match up with the reading in the cycle analyst?
No, 15 volts does not sound healthy at all. Especially as this is obviously a lithium pack. Lithium packs don't have much voltage sag under load (unlike lead).
Are all the cells okay?
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
Thanks for clarifying that. I think I understand how the Ah reading on the CA works now.
The maximum current drawn was 120A. Unloaded the CA shows 50V. I'll test with a multimeter this weekend to see if they match.
I hope the cells are ok. Any ideas whether or not the speed controller could be the reason why the voltage reading is so low? I've read something about controllers reducing voltage to the motor to increase amps when motor RPM is low or have I completely misunderstood this.