How to improve the heat dissipation of high-voltage batteries

Hello everyone, I have a problem with the third generation high-voltage battery of my Prius. The fault code thrown means that the battery pack needs to be replaced. I am testing the capacity to replace the weaker unit. In the process, I found that all the units with problems appeared. In the middle part, I don’t know if it is a coincidence, so I thought that if a resistor of a certain value is connected in parallel to the three temperature probes, so that the ECU mistakenly thinks that the battery temperature is high and increases the fan speed, it may be possible to improve the heat dissipation problem of the battery unit. , this resistance value cannot be too high that it has no effect, nor is it too low that the ECU thinks the temperature is too high and throws a fault code. The resistance value needs to be selected during testing. Do you think it is feasible? Or have any suggestions, thank you.

 

Thank you very much for your suggestions. This is not an original battery, and I don’t seem to have any original new batteries for sale here. If we count this time, I have repaired the battery pack for the third time, but with good luck, I can always find battery cells that are in good condition. During the inspection, I mainly tested the cell capacity. Last time, they were selected after almost 2ah. I have been using it for more than 2 years, and except for the obvious change in the internal resistance and capacity of one piece, everything else is pretty good. The second-hand batteries I purchased this time have relatively large capacities, so I raised the standard to 3.5ah. The way I measure it is to charge 5a to about 8.6v, some can reach 8.7v. If the voltage does not rise for a long time, it will be considered to be fully charged. Use a homemade 14a constant current source and fan for discharging. The discharge cut-off voltage is 6.4v, and if the time exceeds 15 minutes, it means that the capacity will not be less than 3.5ah. I hope it can be maintained as long as possible this time.
After several practices, the bad unit is basically located in the middle, and the temperature probe is a thermistor with a positive temperature coefficient. The resistance is about 10k at 37 degrees Celsius. I want to test it by connecting a 30k or 25k resistor in parallel first. If the battery The actual temperature is 37 degrees, and the OBD display is 42 degrees. The fan should be able to rotate at this time. Keeping the fan working diligently may lower the temperature of the battery and extend its life.
After this repair, the hybrid system fault light will light up again at some time in the future. If the owner of the car has not changed at that time, I may consider using lithium titanate batteries or sodium-ion batteries. Their voltage range spans It is as widespread as nickel metal hydride and can easily reach 20ah. If the capacity is large, the current of 50a is not difficult for these lithium batteries. You must know that even for a 10c battery with a capacity of 20ah, the standard current is 200a. If it works at low In the load area, heat and life can be guaranteed, and there is no need to design a specially designed heat dissipation solution. If you have time, they are very cheap, but you need to purchase additional insulating partitions, pole connectors, suitably sized and sturdy boxes, cables, and protectors. The amount of work is considerable, and the performance and longevity should be no problem.

 

Thank you for your reminder. I admit that I haven't thought of using a thermal imager to find damaged cells. I will buy one. A normal battery will also generate heat when working. The internal resistance of the battery multiplied by the current is its heat power. The drying of the electrolyte will increase the internal resistance, and heat will accelerate this process. The decrease in the capacity of the battery will make it easy to be filled. If it is already full and continues to be charged, a lot of heat will be generated. At this time, the charging power is completely converted into heat. High heat will aggravate the vicious cycle, so maintaining normal temperature is very important for all rechargeable batteries. Please forgive my unclear English description. The code is a fault code, which is what I want to express.

 

It's good to weigh in on the cell, I don't own it yet, probably I will buy it. With the tools I currently have, I have to do it the clumsy way of testing capacity, it's a waste of time, the only advantage is that it reflects the battery status very intuitively。
Thank you very much for your reply. Can you tell me how many grams a cell in normal condition weighs?

 

It is difficult to find cells of the same batch, architecture, and factory year. When choosing cells, I prefer the second generation battery cells, which have a slightly lower voltage than the third generation, perhaps using different plate materials. The third generation cells are at 7.4v for a long time when discharged, while the second generation is 7.2v. Under the same current, the output power of the second generation will be a little smaller, but it is more solid, so I will give priority to the second generation cells, but finding it is already a difficult thing for now.

 

You should learn to be polite to others, whether they are rich or poor. It is good to buy new batteries, but not everyone will choose new ones compared to the price. Besides, who knows how many years the new battery has been sitting in the warehouse. Life is about constantly trying to learn. There is nothing wrong with taking time to do what you like. If you don't like my question, why not keep silent? Meaningless speeches and emotions have no practical effect.

 

You are a keen observer? That's great. I would very much like to speak for the people of Fiji, but frustratingly, I can't speak for anyone else. I'm just asking my own questions. I love where I live, but the economy is bad and there are few companies that offer repairs, so my options are limited. Scarcity makes things more expensive, and I don't want to invest too much money in my second-hand car. I'm glad you told me that Toyota batteries are new and not long-term stocks. I agree very much and admit that I misunderstood before. Regarding your answer that replacing the sensor may cause code errors, I will seriously consider it, perhaps replacing the parallel resistor with a thermistor of a certain resistance value, or abandoning this plan and finding ways to improve the air duct flow. Although you didn't say much, I can see that your precise, concise and implicit answer solves most of my problems. Thank you very much.