Saturday 9 July 2016

Ghetto ebike: Charging

I would like to show how I am charging my ebike battery packs. In the Electric Vehicle (EV) world, developments in battery charging means that we can now recharge vehicle batteries in a short amount of time. 
With charging systems such as on a Tesla car with huge batteries which weigh a whopping 544KG, for the Tesla to achieve a rapid recharge in around 80minutes it needs to also use a massive charger like the 'Tesla Supercharger' station seen above. Big batteries need Big chargers, and this is exponentially matched if you wish to recharge within this short time frame.

The same is true for ebikes. If you wish to recharge in a short time frame, you need a decent charging station, albeit modest when compared to the Tesla Supercharger. At the moment, there are limited options for an ebike owner to buy a packaged system from a retail company, and the price is also suitably matched (high priced) from these companies. If you google ebike charging station you get a whole host of Utopian-idealist dreams.

As we stated above, the Tesla battery weighs 544kg, my ebike battery weighs 3.8kg.

This is where a spot of DIY can save you lots and lots of money. In the Hobby Remote Control world it is well known that people make their own systems for quite small amount of cost. A popular solution is to use PC computer power supplies and connect them to a charging controller to supply the battery with a particular pattern of charging depending on its capacity and chemical composition. What this means to you and I, is that we can use this same system (with a little know-how) and have our very own ebike/Tesla Supercharger in our own home.

Here is my ghetto setup

I am using two cheap (but powerful) 12 volt power supplies taken from a computer, they have been wired in series to make 24 volts. Then, they run to a charging system which can be set to match your battery, in my instance; two 24 volt Lithium batteries with a capacity of 16ah. Together they make a 48 volt battery to run the ebike motor.

A little bit of test observation for the Turnigy Reaktor 300W charger, charging the 16000mah 6s batteries, the charger is capable of charging at just under 13 amps. A more powerful charger and we could charge the batteries at the 1C rating of 16 Amps, but that of course would cost much more money for such a charger. For example, the icharger 3010B puts out 30amps/1000Watts (£160), Turnigy Reaktor 30amp/1000Watt (£100). More on the Junsi range here.
For my budget, I am okay with just-shy-of 13Amps charging. Maybe I will test other chargers in future. Charging the ebike batteries takes my charger approximately 30-45minutes each depending on how depleted they are. 1hr 15mins from 'flat' (3.2v per cell).

My Power Supply unit could easily power two chargers at the same time. Probably four or more at the same time.

(China charging station)

What this means to you and me is that I can recharge my batteries just like the Tesla supercharger, and in around 1 hour I have a fully charged battery ready to ride again. This is how the DIY charging station is going down in Shenzen China. Retail systems made by companies seem to be pricing around £2000 just for recharging systems. If you want off-the-shelf stuff you will pay about £500-600 for a 1-hour charging station. DIY is much much lower cost, but you have to know what you are doing, and most of us don't.

Of course we can also recharge slowly using cheap chargers, which will be suitable for 12-hour overnight charging, and these can be had for modest amounts. But if you wish to be a DIYer you can have a 1-hour supercharger for just a little bit more.

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