So far 1400km of driving with electricity has been fun and easy! This winter has been quite warm and the lowest temperature has been -10C while driving. On that temperature the battery performance is weakened remarkably. Their internal resistance is increased lowering power output and efficiency. I assumed that the batteries would heat up internally to a more efficient working temperature level but this has not seemed to happen. For that reason I decided to try to decrease the batteries cooling by blocking the airflow through the battery pack. The pictures above show how the airflow was blocked through the front mask of the car. Also the original motor covers were installed below the batteries which guide the airflow away from the batteries.
I do not yet know if this modification helps to increase the battery pack working temperature as I still do not have temperature sensors equipped. Also the winter got warmer so I'll have to wait for more cold driving experiences.
A combined ampere-hour / temperature meter is under development using an Arduino and DS18B20 temperature sensors. After all needed components have arrived I am optimistic to get them installed soon as we got a flying start with the application thanks to my brother's Arduino experience!
2 comments:
Warm your battery pack with a heating pad. I got small ones from the drug store for $20 each and pre warm my lifepo4 packs. The difference is dramatic!. With a 48v pack, resting voltage of between 51.8v fresh off the charger after the float has been burned off, with a 15a load my voltage drops are ~4v @ -5degC and 1V @ +20degC. Heating my pack with 2 50watt heaters has given me almost 200 W/h extra power. I haven't wired up the heaters to my pack(yet). Theyre on AC and my packs are insulated with foam and bubblewrap. After seeing some of the discharge voltage vs temp curves from manufacturers I decided to do something about it.
Thank you for the hint! How big is your battery pack and how long does it take to warm up the pack? Do you have any kind of temperature control in the battery pack heater?
I'll definitely insulate my pack better and also consider installing a heater.
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