I finally settled on the batteries that will be used for the eTrike.
They are the same ZIPPY Flightmax 5000mAh 6S1P 15C from hobby city that I have previously mentioned. For those not versed in battery speak, 6S is 6 cells in series (in a line) and 1P is 1 parallel (side by side).
Each cell within the pack has a nominal (normal under use) voltage of 3.7V. So a single pack has 22.2V. The total voltage I can use is limited by the controller and motor. This limit is around 48V. As the top speed and power output of the motor increases with voltage I intend run it at the full 48V.
To achieve 48V I will be using two of the Zippy packs in series. This makes a total of 12cells, 6per pack, which is equal to 44.4V nominal. It should be noted though that when freshly charged each cell can get as high as 4.2V, or a total of 50.4V, hence why no more than 12 cells in series will be used.
With this setup I would have a 12S1P 44.4V pack with a capacity of 5000mAh (5Ah).
This will not be enough capacity for a 60km range.
So I plan to use a total of 6 packs, configured in 12S3P for a total of 15Ah capacity. Even then it stands to be seen if this is enough for the desired range.
These six packs will have a combined weight of 4.3Kg. This is astoundingly light considering the amount of power contained within them. For comparison, if sealed lead acid batteries were to be used to get the same 720Wh storage capacity it would require 18.45kg worth of 12V batteries. This is over 4 times the weight and a good example of the power contained within lithium batteries
The 6 Zippy batteries will be mounted on the bike within two pannier bags hanging over the rear wheel. Three batteries per bag for good weight distribution. These bags will also be mounted as low to the ground as possible to help prevent roll over.
Due to the volatile nature of lithium batteries when damaged they will be contained within some sort of metal box within the soft cloth bags. This should protect them from any mechanical damage as well as the weather. This box will be padded internally with some form of foam to stop the cells moving around. The metal box will also contain a vent plug facing towards the rear of the bike just in case a LiPo pack does go up in flames.
Now for the charing.
This is by far the most difficult part of dealing with this type of lithium batteries. Trying to keep every single cell at a constant voltage requires some custom work. This I will cover in a follow up post as i’m still working on the detials