72 Volt Upgrade – Introduction

All the ingredients of the 72V upgrade have been discussed already in this blog and others like it, as well as in places like the Electric Motoring Forum. But a lot of people just want the ‘recipe’ in one convenient chunk.

It’s not actually quite as simple as this as there are subtly different ways of solving some of the problems confronted by upgrading to a 72V system. There are also many different opportunities to reconfigure the existing system, or to add new features, such as regenerative braking or cruise control. You will want to decide how far you want to go with this upgrade, and how important it is for you to preserve things like range while adding the extra power needed to make it act more like a ‘proper’ bike.

There are four main areas of consideration that need to be born in mind when upgrading to a 72V system:

1. Batteries and Power System Cables

The first thing you should do is upgrade the power cables with something a little more substantial. You don’t have to do this if you’re using just a basic 72V controller, but I would recommend it, as the existing wiring on the 48V bikes is a bit flimsy. The thicker the cables, the less resistance there will be in the system, and the more current can be drawn without the risk over-heating. Upgrading the cables in this way means better performance and one less bottle-neck in the system; it also means you’ll be able to use any controller you want, and draw as much current as the motor is capable of handling (and then some).

If you just want to get up and running quickly with a basic controller, then you can skip this part and come back to it later if you upgrade to a better one, but my instructions on fitting the controller assume that you’ve done this, and that you’ve included an anderson connector in your new arrangement. If you want to skip this part of the work, you’ll have to improvise a little to take this into account.

Prepared for the Upgrade – Welding Cables replace existing Battery Wiring

If you’ve committed yourself to the upgrade and already ordered the parts you’ll need, this is a good thing to spend time on while you’re waiting for them to arrive. That way you can have all the cables needed for the existing and extended battery system ready for when it comes time to wire in the controller. You can also have the main part of the work (the controller) done in a single evening, so you’re not off-the-road for too long.

To actually charge the new battery bank, you’ll also need a 72V charger. These can be found on eBay but will probably have to be ordered from China. my shop now does a 72V charger suitable for this purpose.

2. 72V Controller and Connections

eBay has many merchants selling stock, budget controllers, most of which appear identical, but usually need to be ordered from China and have little if any documentation. If you definitely want regenerative braking, though, it’s best to stick with the well documented (but more expensive) Lyen’s “Extreme Modder” Edition (reviewed here and here) or e-crazyman controller, as these can include a programmable interface so that they can be set up with the right regen voltage for the Ego Scoota.

A typical, stock 72V Controller

If you expect to be relying heavily on your bike, then it might be worthwhile getting an extra, cheap one as a spare. That way you can be up and running quickly if this essential unit breaks down.

The connectors on the controller will also need changing to some degree to make them compatible with the bike. If the phase wires don’t come with 6mm ring connectors then these will need to be added, and the power wires will need to be hooked up to an Anderson connector  which can accommodate the thicker cable we’ll be using on the battery bank. A two-pin mini-connector will also be needed for the brake cut-off and power-feed wires on the Ego’s loom.

3. Running the 12V system

Once you upgrade to 72V, the 48-12V converter that provides power to the 12V system for the headlights, indicators etc. will no longer work. The crucial connector Bk/Y/R that converts the full battery bank voltage into 12V will need to be served by something else. Quality 72V versions of these (they will actually allow any input from 20-90V) are now available from my shop. The unit has exactly the same connector as the 48V converter that comes with the bike, and can therefore be mounted ‘plug and play’ in the same position as the old one. Since it can function with the original 48V input voltage, it is also a good place to start for an upgrade as it will still work fine with the original battery bank.

The 72-12V DC-DC Converter

Alternatively you can use Mike’s recipe to modify a PSU for this purpose, but bear in mind there can be complications (as with myself) when the polarity of the unit varies, and you can end up with -12V instead of +12V coming off the final product. This will require a couple of wires switching – the 12V and the ground.

If you don’t have a suitable converter available, you can set up a workaround by simply powering the 12V system from a single battery, either a separate one, or an existing bank-battery. Bear in mind, though, that this battery will go out of balance more easily with prolonged use and may require topping up. But this is easy enough to do through a homemade connector that can allow you to charge the battery from the connector that hooks it up to the loom.

The loom connector for the 12V system supply. As an interim solution, it is fed here by a lead from the first battery in the bank

Out of these alternatives, I’d recommend the replacement 72V converter available from my shop, as it’s built for this specific purpose, is as cheap as (if not cheaper than) the PSU-based solution and is also much more energy-efficient.

4. Adapting or Replacing the Battery Meter Setup

Another problem is that the Battery Meter will no longer function. There are three main ways that people take care of this. One solution involves running a lead off of the positive terminal of Battery 4 to provide the 48V that the existing meter requires. However this solution also requires a relay to be attached so that the 48V is only applied when the ignition is on. Another solution is to use a zener diode to drop the voltage of the battery meter terminal on the upgraded system back down to the 48V required.

The third solution is the route I opted for, which is to simply replace the existing battery meter for a better unit. I collaborated with Sparklight Products to customise their 6-LED, 12-state battery meter and bring it out as a kit suitable for the Ego Scoota. This kit is available in 48V, 60V and 72V form.

The meter is much better than the existing one, and very affordable (a tenner plus change). If you like tinkering around, and don’t mind the work involved in refitting the meter then this is probably the solution for you.

The Sparklight Products 6-LED, 12-State Battery Meter

This guide is split into five parts:

If you go through all five parts of this in order, it should be hard to go wrong. With the availability of the Thunderstruck 72-12V converter unit, 4.2.2 can be skipped if you take this route. Regenerative braking isn’t covered as yet, but that will probably be coming soon. Remember to get a Lyen’s “Extreme Modder” Edition or  e-crazyman  controller if you definitely want that feature, as most cheap controllers don’t support this feature or explain how to make it work.

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