Battery Safety

As i’m planing on using some lithium batteries for this project its important that safety be a of the highest priority.

Normally the biggest concern with this type of battery comes from over charging them past 4.2V per cell. If over charged it can and will lead to large amounts of fire followed by small amounts of money. Hopefully this side of the problem will be addressed by the home assembled custom charger.

The second cause for concern comes when using the batteries. If they are over discharged below 80% (less than 20% remaining) then it will reduce their over all life span and if taken down further, possibly yours. Lastly, the packs I intend on using are rated at 15C. Remembering that 1c is discharging the pack in 1 hour. So 15C is discharging the pack in 2 minutes. For more info on battery terms look here. The pack should never be taken over this limit.

Ok so with that in mind it is important to know what voltage the packs are at when riding. This will be achieved in two ways.

The first is looking at the over all net energy taken out of the batteries using the cycle analyst. The cycle analyst measures many things such as speed, distance, range, battery voltage, battery draw current, battery watter hours uesd etc. More info on what it records can be found here. The key parts to watch is the total pack voltage and the total amount of watt hours thats been pulled out. By making sure these are above a set level by the time you reach home all is well.

CA-DPS

Cycle Analyst

Secondly, I also plan on using a 6S battery monitor for each individual pack. These can be found over at hobby city. These simple devices only job is to set off a loud buzzer if any of the packs drop below 3V. There will be a total of 6 of these, one for each pack.

batt-monitor-6S (1)

Hobby King Battery Monitor 6S

 

The hope is that through the combination of this low voltage alarm, the cycle analyst readings and balancing the pack at the sell level every charge, there shouldn’t be any problems.

Many thanks to recumpence for sharing his years of knowledge on battery safety in a post he made over at endless sphere.

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About Richard

I am a Materials Engineering working in the field of Magnetic Materials in Melbourne, Australia. This blog covers my personal interest in all things CNC.
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