PROBLEM: Reduced life of lithium (LiFePo4) batteries due to excessive temperatures: <32F and >80F.
SOLUTION: A thermoelectric cooler can cool the batteries, extending their life.
Technomadia reported that their lithium batteries had reduced life due to being stored in a non-climate-controlled compartment. Here is a cheap, simple solution. The TEC, or Pletier device. The BTU calculations say it should produce about 267 BTUs of cooling, enough for this compartment, even accounting for the heat of the environment and other heat producers in the compartment.
The system draws about 144 watts, but solar power will easily make up for this.
When the temperatures exceed 80 F, the digital thermostat will engage a relay and testing will begin. The heat is dumped into the Joey bed area, where an exhaust fan may need to be installed. See the photos below.
COOL!
How did you transfer the heat from the "cold side" to the "hot side" in the joey bed compartment?
There is an identical heat pipe / radiator on the hot side, in the Joey bed. It just clears the slide mechanism.
The system is reversable, so the batteries could be heated in the winter. This is MUCH more efficient, because, prior to this, I was running the AC, which draws at least 1700 watts or would have to run the furnace during the winter.
As we transition from lead to lithium batteries, active cooling will be needed and Foretravel will need to engineer solutions like this, if we customers make it known that we care about battery longevity.
On a longer term schedule than we all probably have the inventor on the li-ion battery dr goodenough made another breakthrough on the design.
Because of the newer design to come we will be in an electric battery world I think.
Cheaper, not temp sensitve, three times more capacity, charge in minutes not hours, silicone not lithium.
Trucks and busses and cars running on battery.
Will happen. Just a matter of time we probably do not have personally.
But an electric Foretravel would be the bomb.
Sorry for the hijack just dreaming about the future
Excellent engineering. The heat pipes, radiators, and fans are a big improvement over the old passive finned pletier thermocouples used in my old semi-cold beer cooler.
Tesla's electric semi is supposed to be debuting this fall.
an all electric Foretravel may not be as far away as you think.
Elon Musk gives us a glimpse of Tesla's electric semi truck (https://www.engadget.com/2017/04/29/elon-musk-tesla-electric-semi-truck/)
Tim you are my new favorite mad scientist! :)
see ya
ken
Very nice! What was the source for your thermoelectric cooler?
Don
It's not working. The cool side is not cool. The heat pipes are either:
1. Not oriented correctly.
2. Not designed for this application: horizontally oriented and the internal wick either doesn't exist or is not the right material.
Back to the drawing board.
Do you have circulation pump, or are you trying to rely on natural fluid convection? I'm not understanding the layout in your pictures. A pelier cooler has a hot side, and a cool side. Why not stick the cool side on the battery?
The way I understand heat pipes is a liquid in the wick that heats and then evaporates, transferring the heat to the radiator, and a fan removes the heat from the radiator. The problem with putting the cold side on the batteries is that the hot side is on the other side of the pleiter and the heat just goes back in the compartment. With the radiators and heat pipes, the heat can be transferred to a different place, in this case, the joey bed compartment. I am thinking that the heat pipe will not transfer the cold as well as the heat. In that case, the pleiter could be in the battery compartment with a blower on the cold side, circulating the air, and the hot side could use the heat pipes and radiator to send the heat to the other compartment. Just a theory.
Tim,
Those fin towers look liike CPU heat sinks. If the are then there are plenty of them running in horizontal positions for years at a time. I don't believe the tubes have fluid in them - just holliw copper tubes.
Liquid cooled CPU heatsinks are a completely different animal.
Chris
Tim,
Can you separate the batteries using spacers to allow air circulation? That would aid in any cooling, whether high tech or just an exhaust fan.
heat pipe How a Heat Pipe Works - heat sinks (https://www.aavid.com/product-group/heatpipe/operate)https://www.aavid.com/sites/default/files/literature/aavid-heatpipes.pdf
Thanks for the suggestions. The whole battery pack is now surrounded on all sides by one inch of air to aid in heat dissipation. To put a separator between all cells would require non-standard battery straps and custom-made separators.
I am investigating a PC liquid-based cooler, which does not rely on the copper heat pipe vapor principal.