Hiboy S2, S2 Pro and KS4: E5 low voltage error or the battery won't charge

The display shows E5, or the scooter dies early and won't seem to take a charge. Hiboy's troubleshooting guide lists E5 as low voltage protection on the S2, S2 Pro, S2 MAX, S2R, S2R Plus, KS4, KS4 Pro and MAX Pro, and on the S2 Lite. Its advice is to charge the scooter, and to replace the battery if E5 is still there after charging (Hiboy troubleshooting guide). The short answer: prove the charger works and give it a full charge in the right temperature before you assume the battery is gone.

Most likely cause

E5 means the battery voltage has dropped low enough that the controller protects it by cutting power. Most of the time that's simply a flat battery. When E5 stays after a proper charge, the battery can no longer hold its voltage, and Hiboy's fix is a new battery (Hiboy troubleshooting guide). A charger that has quietly failed gives the same picture, so test it first.

Other causes to rule out

• A dead charger: Hiboy's won't turn on guide says to plug the charger into a known working outlet, check its light, check the cable for damage, and try a compatible charger if it seems faulty.
• A dirty or wet charging port: Hiboy's common problems guide says to check the port for dirt, debris and moisture, let a wet port dry, and never force the plug.
• Cold: the same won't turn on guide notes lithium batteries underperform in the cold and suggests warming the scooter indoors. The S2 and S2 Pro manual gives a charging range of 5 to 45°C (41 to 113°F) (S2 and S2 Pro manual).
• E6, over-voltage: a different code. Hiboy points to sudden braking and riding uphill, with a new battery if it persists.

How to confirm

1. Plug the charger into a wall outlet you know works. Hiboy's S2 charger and S2 Pro charger pages say the light is red while charging and green when full.
2. Check the charger cable and plug for kinks, cuts or a loose barrel.
3. Look into the scooter's charge port with a light. Clear dust gently and let it dry if wet. See check your charger.
4. Bring the scooter indoors to room temperature, then charge. The manual gives about 5 to 6 hours for the S2 and 6 to 7 hours for the S2 Pro, and says not to charge for more than 12 hours (S2 and S2 Pro manual).
5. Power on after the full charge. If the battery shows full but E5 comes back within minutes of riding, or the charger light goes green almost at once, suspect the battery.
6. If you can, try a known good charger of the right type before buying a battery.

Fix options

Charge it properly (easy)

Many E5 cases end here. Recharge when the battery drops below 20 percent, as the manual advises, and see store your battery for winter if it sat unused. The manual says to store at 30 to 50 percent and recharge about every 60 days.

Replace the charger (easy)

Hiboy sells a charger for the S2, KS4, S2 Lite, S2 SE, S2 Nova, DK1 and C1, and a separate one for the S2 Pro, KS4 Pro and U2 rated at 42.5V and 2.0A (S2 Pro charger). Use only the charger listed for your model.

Replace the battery (pro)

If E5 stays after a full charge on a working charger, Hiboy's fix is a new battery. Its S2 series parts page lists a 36V 7.5Ah battery for the S2 and KS4 and a separate S2 Pro and KS4 Pro battery. Have a shop fit it, since the pack sits in the deck and connects straight to the controller. Battery prices often make this a repair or replace decision on an older scooter.

Parts

• Charger for your exact model (Hiboy part)
• Battery for your exact model (Hiboy part, shop installed)

When to get a pro

Get help for any swollen, hot, leaking or damaged battery, for a battery swap, or if the charger and port are fine and the scooter still won't charge. See battery won't charge, e-bike battery care and when to call a pro.

Sources

• Hiboy troubleshooting guide, hiboy.com
• won't turn on guide, hiboy.com
• common problems guide, hiboy.com
• S2 and S2 Pro manual, cdn.shopify.com
• S2 charger, hiboy.com
• S2 Pro charger, hiboy.com
• S2 series parts page, hiboy.com

Stuck after these checks? Find a shop near you.