Troubleshooting Guide > Vehicle Only Runs At Partial Throttle
Vehicle Only Runs At Partial Throttle and Does Not Run At Full Throttle
When the vehicle only runs at partial throttle and does not run at full throttle the most common cause of this type of problem is an old, worn out, or faulty batter or battery pack. There is a speed controller wired in between the battery and motor and most speed controllers have a low Voltage cutoff function which turns the motor off when the battery or battery pack Voltage drops down to a zero percent state of charge. This low Voltage cutoff function prevents the battery or battery pack from being over-discharged which is necessary because if the battery or battery pack is over-discharged then it may become damaged and not be able to be recharged again so it would need to be replaced. When a battery or battery pack is old, worn out, or faulty then it can temporarily drop down to its zero percent state of charge during heavy use which causes the speed controller to turn the motor off, however, under lighter use its Voltage will rise to above its zero percent state of charge. This is what cause the motor to run at partial throttle and not to run at full throttle. A 0% state of charge is not the same as zero Volts and it is usually just a few Volts under a 100% state of charge. We have a Battery and Battery Pack State of Charge Chart that can be used to see what the zero percent state of charge Voltage level is for the vehicle's battery or battery pack.
If the Throttle has Indicator Lights Use Them to Determine Voltage Drop
If the vehicle's throttle has indicator lights then these lights are a Voltage indicator which can be used to help determine the condition of the battery or battery pack. If if the indicator lights drop down at full throttle and go up at partial throttle that indicates that the battery or battery pack is dropping a significant amount of Voltage under a heavy load.
Try Deep Charging The Battery Pack for 48 to 72 Hours
Sometimes lead-acid battery packs need a deep charge to equalize the cells and help the battery pack regain capacity. Try charging the battery pack for 48 to 72 hours and then see if that helps. It is a good practice to perform a deep charge a couple of times a year or whenever a significant loss of capacity is noticed.
Test The Battery Charger Port
(No Tools Needed) If the battery charger is plugged into the wall, unplug it. Plug the battery charger into the battery charger port on the vehicle and look for an illuminated indicator light on the battery charger. If an indicator light on the battery charger illuminates then the wiring and wiring connectors going to the charger port are good and the charger port itself is good. Not all battery chargers have an indicator light that will illuminate when the charger is only plugged into the vehicle, so if the light does not illuminate then a secondary Voltage test with a multimeter should be performed as described below.
(Tool Needed: Multimeter) If you have a multimeter the battery charger port's Voltage can be tested. The Voltage level present at the charging port should be the same as at the battery pack. If the charger port has male terminals then great care needs to be taken to avoid short circuiting the terminals to each other or to the charger port's housing if it is metal.
Test The Battery Charger
(Tool Needed: Multimeter) After testing the charger port and confirming that it has Voltage then the battery charger can be tested. If the charger port has no Voltage then that issue will need to be fixed before testing the battery charger. To test the battery charger to confirm that it is recharging the battery or battery pack, first test the Voltage of the battery or battery pack to confirm that it is below a 100% state of charge and that it needs to be recharged. We have a Battery State of Charge Chart to help with determining if the battery or battery pack needs to be recharged. Once it has been determined that the battery or battery pack needs to be recharged, plug the battery charger into the vehicle's charger port, and then plug the battery charger into the wall. Next test the Voltage of the battery pack with a digital multimeter to see if its Voltage is slowly climbing. The multimeter should be set to a DC Voltage range that allows reading the tenths or hundreds of a Volt of the battery or battery pack. If the battery or battery pack's Voltage slowly climbs to a higher number then that indicates that the battery charger is recharging the battery or battery pack. Continue to charge the battery or battery pack until the light on the charger indicates that it is fully charged, then test the battery or battery pack Voltage to see if it is at a 100% state of charge as specified in our Battery State of Charge Chart. If the charger is not charging the battery or battery pack up to a 100% state of charge then the charger is faulty.
Test The Battery Pack On A Scooter That Runs
Visit our Battery Pack Load Testing Guide.
Test The Battery Pack On A Scooter That Does Not Run
(Tool Needed: Battery Load Tester) If the scooter is not running, a load test can be performed on its batteries by removing the battery pack from the scooter and taking the individual batteries out. The individual batteries can then be tested with a automotive battery load tester. Most entry level automotive battery load testers place a 100 Amp load on the battery which is too high so an adjustable carbon pile battery load tester is required and should be adjusted to place a 30 Amp load on the batteries.
Test The Voltage Of The Battery Pack
(Tool Needed: Multimeter) The battery or battery pack Voltage can be tested to determine its state of charge. Once the Voltage has been read our Battery State of Charge Chart Page can be used to determine what percent the state of charge is. A good battery or battery pack's Voltage will be at a 100% state of charge level after it has been discharged and allows to sit a few minutes, or if it has been in storage. If a battery pack Voltage does not bounce back to a 100% state of charge level within a few minutes after being discharged that points toward a faulty or worn-out battery or battery pack. When a battery pack has been charged to a 100% state of charge and its Voltage drops below a 100% state of charge level after sitting for a while that points toward a faulty or worn-out battery pack. Good batteries and battery packs will bounce back to a 100% state of charge within a few minutes after the vehicle has been driven.