Mike Dabrowski 2000
10-27-2007, 10:04 PM
To continue the battery management discussion where it belongs.
We were playing with an Insight battery pack today, and I got to thinking about the re balancing. Many of the cheaper power tool battery chargers for NICAD and NIMH used the charge to target temp method to detect full charge.
at 100% charge, most of the energy in the charge current turns into heat, so a simple average temperature measurement relative to ambient can assure 100% SOC in all cells. A FULL charge.
Take a look at the bottom photo on my battery exposed page.
The nearly charged 2 pack of prius subpacks started charging at ~85% charged.
It saw an additional 6A for 4 to 5 hours.
http://www.99mpg.com/resources/articlesandblogs/batterypacksexpose/
The subpacks work just fine, and seems to be of normal capacity.
Hope to get some time to test them more thoroughly soon.
Ian detected final charged cel to cell temperature differences within a subpack, so there was obviously a different SOC within the 6 cell subpack, probably meaning that some of the cells had not quite got to the full charge condition.
The blog about the first charging test where you can see the unbalance:
http://www.99mpg.com/workshops/mikessaturdayhybri/
I think as a result of these experiments, that the packs are a lot tougher than intuition would lead us to believe.
100A out of a D cell for 100K partial cycles says it all. They are tough.
The pack could be put into a balancing charge with a setup of a variac and a rectifier, using the PTC thermal strip to signal when the pack reaches some average temp that says ok everyone is up to max 100 %. Fans running of course.
Then we let the pack sit and cool before putting it back into service.
When I get the right IMA pack in my lab, that would be a great and simple reconditioning process to try.
Lets see D cell spec is 500 full cycles to drop to 80% capacity, that means that one could rebalance their pack with a balancing charge every 6 months and still last for 250 years.:rolleyes:
In theory one could just look at the PTC strip resistance which is in physical contact with each cell, to tell when all the cells had reached a maximum temperature, thats where all the electrical watts are turned into thermal watts, or 100% balanced and charged.
should work?
We were playing with an Insight battery pack today, and I got to thinking about the re balancing. Many of the cheaper power tool battery chargers for NICAD and NIMH used the charge to target temp method to detect full charge.
at 100% charge, most of the energy in the charge current turns into heat, so a simple average temperature measurement relative to ambient can assure 100% SOC in all cells. A FULL charge.
Take a look at the bottom photo on my battery exposed page.
The nearly charged 2 pack of prius subpacks started charging at ~85% charged.
It saw an additional 6A for 4 to 5 hours.
http://www.99mpg.com/resources/articlesandblogs/batterypacksexpose/
The subpacks work just fine, and seems to be of normal capacity.
Hope to get some time to test them more thoroughly soon.
Ian detected final charged cel to cell temperature differences within a subpack, so there was obviously a different SOC within the 6 cell subpack, probably meaning that some of the cells had not quite got to the full charge condition.
The blog about the first charging test where you can see the unbalance:
http://www.99mpg.com/workshops/mikessaturdayhybri/
I think as a result of these experiments, that the packs are a lot tougher than intuition would lead us to believe.
100A out of a D cell for 100K partial cycles says it all. They are tough.
The pack could be put into a balancing charge with a setup of a variac and a rectifier, using the PTC thermal strip to signal when the pack reaches some average temp that says ok everyone is up to max 100 %. Fans running of course.
Then we let the pack sit and cool before putting it back into service.
When I get the right IMA pack in my lab, that would be a great and simple reconditioning process to try.
Lets see D cell spec is 500 full cycles to drop to 80% capacity, that means that one could rebalance their pack with a balancing charge every 6 months and still last for 250 years.:rolleyes:
In theory one could just look at the PTC strip resistance which is in physical contact with each cell, to tell when all the cells had reached a maximum temperature, thats where all the electrical watts are turned into thermal watts, or 100% balanced and charged.
should work?