AussieInSeattle
New Member
- Joined
- Jan 2, 2020
- Messages
- 59
My 16S 120Ah order from XUBA ($837 shipped via sea to Seattle) should arrive the first week in September so I've done a lot of reading on what to do when they arrive. I've come up with the following approach for doing a capacity test as quickly as I can with only having to purchase minimal items - anyone have any comments on this approach? I know I could buy one of those 150watt single cell capacity testers but even with "only" 120Ah cells it would take a long time to test each one based on my calculations - they'd also take a month to get here so would need to order asap if my calcs are wrong
Items I have already that will be used when golf cart is put into service:
STEP 1 - TOP BALANCE:
Items I have already that will be used when golf cart is put into service:
- Golf cart - 2011 Precedent with AllTrax 500amp controller and Admiral MOT-A2 speed motor - 12" wheels (these things will all matter for real world capacity test)
- 1200 watt heat gun
- 16S 30Amp Bluetooth BMS
- Relays, etc to control charge and discharge cutoff (need these as a golf cart can draw 200+ amps)
- 10Amp 58.8 volt (adjustable) AC charger
- Renogy Battery monitor to track capacity remaining once pack is in use
- 100 Amp shunt based battery monitor that shows Wh consumed ($20 on amazon)
- Two 8S battery monitors - could also get this info via BMS Bluetooth app but this is easier ($30ea on amazon)
- 1500 watt AIMS 48v inverter ($250 at home depot) - will likely sell on Craigslist once I am done testing to recoup some of my cost
- CC/CV 10Amp adjustable DC power supply recommended by Will ($60 on amazon)
STEP 1 - TOP BALANCE:
- Upon arrival put cells in 16P using XUBA supplied busbars for 48 hours
- Put cells in 16S and hook up 30Amp BMS and set BMS to HV cutoff of 3.6 volts per cell
- Hook up two 8S battery monitors so I can watch voltage per cell (easier than phone based app)
- Charge 16S pack using 10Amp AC charger I purchased for the golf cart - charger set to 57.6 vols (3.6 volts per cell)
- Put cells in 16P again and use CV/CC power supply (recommended by Will) set to 3.625 volts and wait for amp draw to drop to 0
- Put cells in 16S and hook up 30Amp BMS and set BMS to LV cutoff of 2.5 volts per cell
- Hook up 100 amp shunt based battery monitor that measures cumulative Wh
- Use AIMS 1500 watt 48v inverter (90% efficiency) and 1200 watt heat gun - at 1200 watts and 90% efficiency I should draw 1333 watts per hour from the pack - run heat gun and check watts draw on battery monitor from step 2
- Pack should start with 6960 watts (3.625 x 16 x 120) so expect the BMS to cut off after about 5 hours and 13 minutes - pretty close to a 0.2C discharge
- Analyze test results
- Charge thedepleted 16S pack using the 10 Amp AC charger and take note of voltage via the shunt based battery monitor when I've put 90% of the charge into the pack and 95% - can get these total watts numbers by multiplying Wh from capacity test above by .9 and .95
- Once charging has finished, set charger to desired absorption voltage (90%, 95% or 100%) - will likely use 90% as I have lots of capacity for my needs
- Set BMS settings appropriately to match charger voltage for HV cutoff from step 2 above and set LV cutoff to 3V per cell
- Remove the 100amp battery monitor
- Hook up shunt based 500 Amp Renogy battery monitor and set its 100% Ah capacity based on above settings - this will be used to track remaining Ah while cart is in service - due to cart pulling 200+ amps at times my 100Amp monitor would not work - Renogy monitor does not track Wh so cannot use it for capacity test - also like the appearance/layout of the Renogy monitor over the cheaper ones
- Fully charge pack to whatever I decided above (90% capacity)
- Use golf cart until BMS cuts out - track how many miles I drive via phone app, how aggressive I drive, hills, etc - expecting this to take 3-4 rounds of golf (20-25 miles) and errands
- Analyze results - this capacity test is moreso for likely questions I'll get regarding "how many miles can you drive with a 120Ah pack?"