Valeo Develops Direct Cooling System for Li-ion Battery Packs
04 October 2008
Valeo has developed a direct cooling system to control the temperature of lithium-ion batteries in hybrid and electric vehicles. The system consists of an evaporator that is built into the battery module and is connected to the vehicle’s conventional air conditioning circuit. This evaporator, which is inserted between the cells, releases cold to enable heat exchange.
The system is completely integrated into the air conditioning circuit. There is no secondary water or air circuit to recover the cold and convey it to the battery.
In the system, R134a fluid air conditioning circuits flow through two parallel-mounted evaporators: the first one, for the cabin, positioned in the HVAC (Heating, Ventilation and Air Conditioning) unit and the second one, built into the battery module.
Evaporators are usually made up of a multitude of tubes that form a radiator. In order to integrate the evaporator into the battery, these aluminum tubes are coiled in the space available between each cell. Aluminum fins, secured by a plastic frame, are used for an ideal heat exchange between the cells and the coils. Each cell is in contact with two coils—one in the outward circuit and the other in the return circuit—in order to make sure that the temperature of the cells is even. Finally, the system is sound-proofed in a steel casing.
A second water/glycol type loop or an air exchanger circuit is not necessary for the battery pack. The direct cold circuit is very efficient, according to Valeo, which helps to cut the vehicle’s overall consumption. It also offers an improved cost/performance ratio by using the existing compressor and eliminating the need for an additional pump. It is also compact, reduces the volume of piping and does not require the installation of air hoses or a distribution unit.
The direct battery cooling system is compatible with three different battery configurations: 4 rows of 9 cells, 3x12 and 2x6. The system is also light in weight—for example, the system for a 42-cell module weighs 2.2 kg (4.9 lbs).
"releases cold to enable heat exchange"??.. I'm getting a headache from that one..
why would you want to cool lipos that much?.. for extensive usage in Death Valley? glycol and a small radiator should be more than enough.
Perhaps it is for a small pack (Prius size) that will be worked very hard.
Posted by: Herm | 04 October 2008 at 08:16 AM
Unfortunately the engineers misunderstood. Their task was to develope a system that would increase the value of BEVs not increase the cost.
Posted by: ToppaTom | 04 October 2008 at 09:30 AM
What is hard to understand? This is a very smart company that knows what it is doing. Cabin air conditioning is thermostat controlled, and I would assume this is to. Sounds great to me.
Posted by: deanrunyan | 04 October 2008 at 11:42 AM
'releases cold':
Please. 'absorbs heat' would be more accurate, I think.
Posted by: Nick | 04 October 2008 at 12:26 PM
This will lower costs because you leverage battery thermal management from the existing air conditioning system.
Reverse cycle the system on cold days and hold the pack within a specified temperature range for optimized performance.
This is a good idea, but I would prefer to see a more robust Li-ion chemistry that does not require thermal management.
Posted by: Andrew | 05 October 2008 at 12:00 AM
Definitely issues with battery and electrical system heat are looking for ongoing solution.
That this system can maintain close temperature parameters is great, but doesn't do much for the rest of us.
How about a hydraulic regenerative accumulator or ammonia cycle system to integrate and power all this air con.
We are already hearing about electrically powered air.
Posted by: arnold | 05 October 2008 at 04:01 PM
ZEBRA batteries can be cooled, if necessary, with 120 degree and hotter air. And they will not catch fire if not cooled. They can be made to have an energy density equal to most, if not all, LiIon units. How much do these cooling units reduce the energy density. The additional weight and size of the air conditioning system and the power that it requires must be considered in the actual energy density. ..HG..
Posted by: Henry Gibson | 05 October 2008 at 11:14 PM