Saturday, November 20, 2021

My experience with a grown man Electric Scooter - the Chinese 5600 Watt Laotie Ti30 - Part 2

Moving along with the range of improvements that this scooter requires - of which some are practically essential, the parts I needed for doing a few more improvements have conveniently arrived.

One of the things that have been identified by some as a weak point, are the boxes that are used for connecting the 3 phases coming from the ESC's, which provide power to the motors.

While the boxes and insulating material are not bad and appear to have reasonable thermal resistance and good insulation, there are users who upon pushing harder on the scooter, find that these connection points tend to overheat, causing cables to melt and eventually serious problems to occur. 

My guess is that with the vibration, the screws that keep the terminals in place, may become loose, causing a poor connection which increases the resistance and heat buildup in these points. The yellow box will not necessarily melt, but the cables can heat up to the point of melting lower temperature plastic these might get in contact with, as is the case of the hall effect sensors connectors:

As such the first thing I did was replacing the yellow connection boxes with 6.5 mm bullet connectors:

It takes a lot of heat and solder to properly install these, so it is important to use a powerful soldering iron.

To insulate the bullet connectors I have added heat shrink tubing to each one. It is also important to add the same tubing or a bit of electrical tape to cover the joint between the two connectors, to avoid electrical contact with other parts.

The second improvement was on the charging port. The original aviation connectors are rather inadequate for this purpose because these are not weather proof (there is only a rubber cap for protection), and there is only air between the pins on the socket. 

It is therefore possible that the pins can bend or some metal part comes into contact with these, causing a short circuit. And unfortunately the BMS on this battery allows discharge current on this port (however strange this might seem).

As such I looked for an alternative connector that could support the required charging current (at least 4 Amps), be water proof (ideally IP68), and fit the same holes as the original aviation connectors. That is when I found the SP16 connectors:

These were not too expensive (actually more or less the same price as the aviation connectors), and have the advantage of being water proof. The socket can also be covered with the threaded lid that it comes with (unlike the flimsy rubber cap of the original connectors). According to the vendor, these connectors can withstand 10 Amps, which is an ok margin in respect to the current that is expected to go through these (no more than 4 Amps).

At the same time I looked forward to simplify the charging process, and as such instead of exposing two charging ports, I installed only one which in turn is connected to two battery charging connectors inside the deck (actually I could verify that these are simply two cables connected to the same point on the BMS, no distinct charging circuitry or anything like that, so no worries there to just have one charging port).

In order to use the charging power supplies without changes, I prepared an adapter using the removed aviation sockets:

This way we have a unpopulated hole to which I haven't yet given a purpose to. One option may be of adding a key switch for additional security, or for less security but more safety, place a fuse box or a circuit breaker (less security because by exposing a fuse box we are creating a backdoor for disabling the alarm). Yet another idea would be to place an emergency battery disconnect there. Something which could be pulled out quickly in case of catastrophic battery short circuit would be of great value.

In order to handle the chargers in a slightly more practical way, I have grouped together the cabling, and added the adapter:

I may consider a more tightly coupled approach in the future, but for now is good enough, as it helps keep the cables tidy while using the chargers.

In fact this is another sub-optimal aspect of the product: given that the scooter was bundled with two chargers already, wouldn't instead be more cost effective to add a single 4 Amps charger instead of a couple of two 67.2 Volt 2 Amps chargers that are then connected in parallel to obtain the full 4 Amps? It is a point but my guess is that judging by what is more predominant in the websites, eventually the 2 Amp chargers are much more abundant (and therefore cheaper) than 4 Amps for this charging voltage..
As I have covered in the previous post, one other aspect that requires attention is the folding mechanism. To avoid the creaking sounds, the nut in the bottom needs to be properly torqued:

Not too much that it prevents folding (unless you never plan to fold it), but just enough so that it holds the hinge tight. There is also a plastic part sandwiched between the red lever and the hinge axis, which may get damaged with excessive pressure. In order to prevent the nut from getting loosen with the vibration, I have added a second self locking nut behind it. Ideally thread lock should also be used here.

Finally, one thing that I have initially disregarded is the fact that these parts are completely exposed to sand, dirt and everything that is lifted from the ground by the front wheel. As such in order to protect these, I have covered the hinge with duct tape on the side that is most exposed to the ground.

This prevents sand and other debris from coming into contact with the moving parts in this folding mechanism, therefore avoiding abrasion and damage to the surfaces. Also avoids contact with water, eventually preventing corrosion.

No comments: