Budget e-scooters are commonly available online and from high street retailers. We bought a generic scooter from an online marketplace to find out whether we think it’s safe enough to bring into a house.
We didn’t buy the cheapest scooter we could find. This was a model that has good reviews online for build quality, performance and reliability. We are choosing not to identify the manufacturer and model as this is a problem for all scooters, not just the model we bought.
TL;DR – this scooter is NOT safe to bring into your house unless fitted with a BMS such as BatteryIQ and the manufacture does more work on environment & moisture management. We are willing to pass on our findings to scooter manufacturers.
Nick Bailey holds a Master’s degree in engineering from the University of Cambridge, UK and is the designer of the BatteryIQ system, and conducted this analysis.
Scooter construction
The scooter is aluminium alloy with a foldable steering column, the base part welded into the scooter main platform. It’s front wheel drive with suspension on front and rear.
I was generally impressed with the quality of the mouldings, parts and construction. Used as intended for reasonably smooth roads, the construction is strong enough for a 120kg rider.
The scooter user guide says not to ride ‘in stormy weather’ and has an icon suggesting it should not be used in the rain. There’s a line on the platform suggesting the scooter should not be submerged below a certain depth, corresponding to the position of the bottom panel on the platform.
Platform assembly
The main platform of the scooter is an extruded and welded aluminium alloy assembly. The bottom panel is zinc plated, black powder coated mild steel and is bolted onto the platform with several cap-head allen bolts.
There has been a moderate effort to environmentally seal the bottom panel with a foam gasket. The gasket appears to be open cell foam and is not fully compressed along the gasket interface. It is highly likely that water would travel through and past this gasket.
The steerer tube has open holes into the platform. Any water that gets inside the steering tube (including via two loose cable entry grommets) will flow down into the platform and fill it up like a fish tank.
The platform has a wiring harness exiting the back of the platform past a bulkhead. A minimal effort has been made to use silicone to seal the cables past the gasket but it is not waterproof.
The main power circuit board has been fully potted with a clear compound and is likely fully waterproof.
The design problem with the platform is that water can and will get into the platform enclosed volume and there’s not an easy way for it to get out. Water sloshing around in this volume (or even moisture) is in direct contact with the battery.
Battery pack
The battery pack is comprised of 30 cells of 18650 2.6Ah (approximately) arranged into 10 series, 3 parallel to create a 36/42v module. 2.6Ah is not a high capacity for this size of cell so it is likely these are at the budget end of lithium ion cells.
The pack has a budget generic BMS providing basic protection against extremes of battery failure such as low voltage. It is known that these BMS units do not protect against over voltage, the most dangerous failure mode for packs. If this scooter was charged with the wrong charger repeatedly, it could potentially catch fire. These BMS units also do not protect against deep-discharge; repeated deep-discharge can cause cells to fail dangerously.
The battery pack is heat-shrink wrapped which is presumably supposed to be waterproof. This blue polyolefin wrap is brittle and cracks easily in use and this new scooter already had a crack in the wrapping. The wires had a minimal effort at waterproofing in the enter to the pack.
To all intents and purposes the battery pack is not at all waterproof and if/when water gets into the platform it will likely get into the battery pack and onto the cells.
Lithium ion cells themselves are not waterproof so water will find a way into the cell and lead to corrosion. This can lead to catastrophic failure.
Conclusion
Mechanical design & assembly – PASS
The construction of the scooter is actually very good and impressive for its price and is well assembled.
Overall design – FAIL
Water and rain is a reality of scooter usage. The scooter is not at all waterproof and should not be used in the rain or run through puddles. This is contrary to the manufacturer’s user guide, which suggests the scooter is moderately capable of being used around water. The suggestion on stickers on the platform that the scooter can be run through deep puddles is particularly worrying.
Battery pack waterproofing – FAIL
The efforts made to waterproof the battery are insufficient and had already failed when this new scooter was opened. If water gets into the platform (which it will), it will rapidly get into the battery cells.
Having taken apart and analysed this e-scooter, I do NOT recommend buying or using a scooter of this type. In particularly, it should never be charged in a location where it could cause harm if it catches fire.