Diagnosis of Electric Bike and Scooter Problems

Weak (or Dead) Battery

Introduction

If you are experiencing poor battery performance (charging problems, slow speed, low range, etc.), there may be a simple cure. In some cases, the "push-on" battery connectors are quite loose as they come from the factory. This loose connector problem can cause any of the above mentioned difficulties as well as intermittent operation or losing power after going over bumps. If you have experienced any of the above problems, spend a few minutes tightening these battery connectors. Open the battery compartment and remove the push-on connectors from each battery ONE AT A TIME. Using pliers, squeeze the connector to improve its tightness, and reinsert onto the battery tab. If you still have problems, read on.

Battery capacity can be visualized by thinking of three glasses that are all 5" tall. The first is your new battery and is a fat 4" in diameter with about 64 units of "juice". The second glass is only 2" in diameter so it can only hold 16 units of "juice" when fully charged. The last glass, a mere 1" in diameter, can still be filled/charged up to 5" (13.5 volts), but it only holds 4 units of "juice".

New batteries are "stiff". Usually 3 charge/discharge cycles bring new batteries to 90%+ of their full capacity.

Symptoms/Causes

Symptom: LEV doesn't go as far on a charge.
Cause: weak battery
As an LEV's batteries weaken, they lose voltage quickly. If starting voltage is above 12.5 volts but drops to 11.8 volts after a short distance, the battery is weak. The fact that a battery seems rejuvenated after a rest is typical for batteries in all levels of discharge; they all have a recovery capability.

If a multiple-battery pack (standard on 24-volt LEVs), has one strong battery and one weak one, replace both promptly because:

• Overcharging of the weak battery could occur leading to overheating, fire, and toxic gases.
• Retaining the weak battery will limit range and speed - and lead to cell-reversal and drastically worse performance.
• For best long-term results, batteries must be balanced; that strong battery won't likely be as strong as a new one.

If your LEV's batteries have provided a year's use and only lost 25% of their range, you have gotten your money's worth.

Sealed Lead-Acid (SLA) battery voltage should vary only about 15% over and 10% under the nominal voltage. When fully charged, a 12-volt battery should read 13.2 volts. When discharged, it should still read at least 11.8 volts -- if you want to get hundreds of charges.

Symptom: Sizzling battery sound when fully charged
Cause: Ending voltage is too high
Smart chargers switch their voltage down when fully charged to comply with battery manufacturers' stated "maintenance" voltage of about 13.8V. (27.6V for the pair). The sizzling sound says your charger is staying at the "cyclic" max charge voltage. That's a battery killer over time.

Testing a Battery

Visually inspect for obvious problems like damaged case, corrosion, loose hold-down clamps or cable terminals.

Here are three ways to test a battery:

1. Perhaps the easiest method for checking batteries is to measure the voltage after charging, and then again after several hours. The voltage should not drop more than a few tenths of a volt.
2. Another test is to fully charge the batteries, let them sit over night, and charge the next morning. If the charger doesn't go green (indicate fully charged) almost immediately, your batteries are weaknening. The longer it takes to charge after sitting over night, the weaker are your batteries.
3. After charging your battery, allow it to sit for two to three hours. Then, ride your LEV on level ground for three minutes. Allow it to sit for five minutes before measuring the voltage. Use the following table, determine the battery's state-of-charge.

approx. state of charge	SLA battery voltage	Hawker battery voltage
100%	12.66 volts	12.84 volts
75%	12.45 volts	12.48 volts
50%	12.24 volts	12.21 volts
25%	12.06 volts	11.85 volts
0%	11.89 volts	11.58 volts

Note: If the temperature of the battery is below 70 F, then add .012 volts (12 millivolts) per degree below 70 F.

A battery may have an internal hidden break. Monitor the voltage while pressing on various spots - especially around the terminals. A drop in voltage indicates a hidden break.

Controller Problems

Controllers are electronic devices that stand between the throttle (what you want the motor to do) and the motor. Most controllers are programmed to limit acceleration and top speed. Oftentimes, when something burns out in the controller, there's an unmistakable bad smell of burned electronics. When the burn first occurs, you'll likely also see smoke pouring out.

All electric motor powered vehicles have built in devices to protect them from damage caused by excessive loads or heat. These "excessive loads" and/or heat can be caused by high ambient temperature, heavy riders, hills, low tire pressure, lengthy high speed operation, or a combination of these factors. Generally, the protection devices are in the form of circuit breakers, fuses, current limiting circuitry, and thermal breakers. Their job is to protect the active electrical components from damage. These devices generally stop or retard the performance of your LEV. For example, if the controller detects a low voltage condition, it may stop the motor; going slowly and lightly on the throttle may allow you to limp along for another mile. In the case of overheating, you may have to wait 30 minutes before the controller allows you to go again.

Motor Irregularities

Neither brushed or brushless motors are designed with user servicing in mind. The bearings are sealed, and brush replacement is often a difficult process. The nominal service life of these motors is so great that service is essentially unnecessary. Even so, motors do fail.

If you open your motor for a look, check for these tell-tale signs of problems:

• Brushes: pitted, burned, chipped, worn
• Springs: discolored, dissimilar pressure
• Armature: overheated (i.e. discolored) windings, loose laminations
• Commutator: brush debris between segments, wear, erosion/wear, oxidation
• Bearings: dry, loose, tight
• Magnets: loose, scored by contact with armature

You can clean the commutator - gently - with emery paper. Carefully remove the debris from between the segments with a toothpick. If you replace the brushes, be certain they are exactly the same as the originals. Same with the springs, although sometimes it's advisable to use slightly stronger ones. You MAY be able to lube the bearings, but replacing them is probably best if they're the sealed type.

A good source for small motor brushes is an automotive electric shop that actually rebuilds alternators/generators. Another possibility would be W.W.Grainger or other industrial supplier that specialize in electric motors.

Throttle Problems

Diagnosing throttle problems:

Symptom: Either the throttle sometimes works, or it doesn't work at all AND the motor/controller smells OK.

Throttles come in three types: simple ON/OFF, potentiometer, and Hall Effect. With the simple two-wire ON/OFF throttle switches (used on Zappy, Tracker, Tomb Raider, Eboarder, etc.), start by unpluging the throttle from the the controller. Then, using a multimeter, measure the resistance through the throttle. It should be way high until you activate the throttle when the resistance will drop to near zero ohms. It it doesn't drop, the throttle switch isn't making connection. If you can't repair it, replace it.

With the potentiometer type of throttle (used on Currie, GT, Schwinn, and Mongoose scooters with finned motors, Currie bicycles, PowerCats Tiger scooters, Lashout scooters and bicycles, etc.), start by unpluging the throttle from the the controller. Then, using a multimeter, measure the resistance (Ohms) between 'common' and 'low => high'. The resistance should be below 100 ohms. As the throttle is activated, the resistance will rise to about 5,000 ohms. If initial resistance is 400 ohms, the motor/controller will think something is wrong and won't respond. Also, measure the resistance (Ohms) between 'common' and 'high => low'. The resistance should be about 5,000 ohms; as the throttle is activated, the resistance will fall to below 100 ohms.

Another test for the potentiometer type of throttle is to test the connection to the motor/controller. After unplugging the throttle wire from the motor/controller, turn on the power to the motor/controller. Then, use a paper clip to jumper between the two outer pins of the motor/controller's throttle connection (red and brown in the drawing). Doing so makes the motor run and continue to run until the jumper is removed. WARNING: make sure the drive wheel is off the ground and the vehicle is secure.

With the Hall Effect type of throttle (used on Currie, GT, Schwinn, and Mongoose scooters with brushed motors, most Chinese-made electric scooters, bicycles, pocket bikes, mini choppers and go karts, etc.), start by probing the throttle wires while still connected to the controller. This may require that you insert sewing pins or needles through the insulation of the throttle wires. Then, using a multimeter, measure the voltage on the three pin leads from the controller. Normally, the red wire carries 5 volts from the motor/controller to the throttle for the Hall Effect power source. The white or green wire is the ground wire. The yellow wire returns the Hall Effect voltage to the motor/controller; it ranges from 1.0V (for OFF) to 4.2V (for top speed).

Here's how the throttle voltage and Currie's brushless motor/controller work together for many throttles:

There are 3 wires that go to the throttle, let's call them SOURCE (black), SENSE (red), and GROUND (brown/common). With ground as reference: sense is at a constant +5V, SENSE controlls motor speed. Impedance from SENSE to GROUND is about 5Kohm, SENSE positive, power on. When SENSE rises above 110mV, the motor control circuit energizes. Below 180mV the motor doesn't turn but it becomes resistant to turning backwards. Above 180mV the motor starts turning. No matter how slowly SENSE is raised the motor starts abruptly with a slight jerk. Motor speed rises in proportion to the voltage on SENSE until it reaches 3.6V at which point the motor abruply jumps from medium to full speed.'

These wire colors and behavior varies. For example, one Hall Effect throttle has a red wire (+5v), green wire (+4.2V) and yellow wire (ground) while a second throttle has red (+5V), green (+4.2V) and black wires (ground).

Battery Charger

A 12-volt smart charger will charge the batteries up to about 14.4 to 15 volts before dropping into the 13.8 volt maintenance phase. To find out if this is happening, you need to monitor the charge voltage throughout the entire charge cycle.

The Soneil 24-volt chargers top at 28.8V - and cycle back on if voltage drops below 27.6V. Output voltage of most 24-volt chargers ranges from 27-28 volts, but always below 30.5 volts.

A 36-volt charger should finish the charge at 44.4V, then drop to 41.4 for maintenance.

The Deltrans is a constant current charger like the Soneil. However, it works a little differently in that it has 3 modes of charge:

• constant current "BULK" charge (red LED)
• slower topping off charge as the voltage approaches the peak of 14.9volts (red and green blinking LED)
• stand-by charge of 13.5volts (green LED).

If the charger stops working, open it and re-tighten all connectors. Sometimes this will fix the problem.

Smart chargers switch their voltage down when fully charged to comply with battery manufacturers' stated "maintenance" voltage of about 13.8V. (27.6V for the pair). When the charging current falls to 125-150ma, the battery is fully charged. (for all practical purposes). Unfortunately, the some "stupid" chargers (generally with 1-amp capacity) don't drop voltage and keep charging at the 28.7V level! A "smart" charger will, at this point, drop to 27.6 volts. If you hear a sizzling sound, that's due to overcharging at the bulk charge voltage (28.7V). Over time, this will reduce useful battery life expectancy. If you have a dumb charger, unplug it when the green LED lights up.

3 LED smart chargers (such as the ZAP and EV-Warrior chargers):
If the yellow LED is on, the charger is properly connected to the batteries.
If the red and yellow are both on, that means it is charging.
If the charger never gets to the alternating yellow and green (charged/float) stage, then explanations exist:

1) One of the battery cells shorted within the battery and the battery won't ever charge to full voltage;

2) The "pot" needs to be adjusted to the proper output voltage. To make the adjustment yourself, first unplug the charger and then unscrew and remove the casing (back side). The pot is obvious, it's a small plastic white dial with a small slot. Insert a small precision (or any small slotted) screwdriver and turn it clockwise one or two degrees. 

Then close up the charger and plug it back into the battery pack and wall socket. Give it half an hour to charge to full capacity. If the scooter doesn't go to the alternating green/yellow stage, then repeat until it does. Important: do it in small stages (small turns of the pot each time, one or two degrees), even if it means opening and closing the charger a few times; that's better than having it set too high. When it does reach the charged stage, check to ensure it's at the proper finishing voltage. After it's charged, wait half hour or so and check the voltage of the batteries by inserting meter leads into charging port, it should read between 26.6 and 27 volts (for a 24-volt charger).

Wires, switches, fuses, etc.

If the fuse blows on a Currie scooters or Electro Drive bicycle systems, follow these diagnostics steps:

Is your battery box blowing fuses when connected to nothing?

• IF Yes.... battery box bad.
• IF No......Connect box to motor/throttle. Then turn battery box on.

Did fuse blow?

• If no... then When does fuse blow?
• If yes..... Disconnect Battery box and hookup alternate 24 volt source with fuse.

Does Fuse blow with alternative 24v source?

• If yes.... motor/conroller bad.
• If no.... check original battery wiring.

Blown fuses are an indication of something seriously wrong. Simply replacing the fuse doesn't prevent further failures. However, you can expect to blow one or more fuses performing diagnostic tests such as the one above. The 40A fuses used in Currie products are difficult to find at auto parts stores. Instead, try your local car audio store.

Check electric connections - especially at the battery terminals - for corrosion. If corroded, clean the connections and apply No-ox, Ox-guard, etc. It's a gray-colored conductive goop for copper and aluminum contacts. It's like vaseline mixed with graphite and is used commercially for electrical contacts to guard against corrosion. Some folks just use plain old wheel bearing grease.