Ricky Suiter wrote:
> Ohh no, your giving me good, probably warranty voiding ideas. I would
> probably do that if there wasn't such a generous warranty on the IMA
> stuff. Actually, looking at the design I've been starting to wounder how
> the air flow through the box is as there are the fans that blow air in,
> but nothing that really pulls it out very well. I've been contemplating
> potentially making myself a clear plastic cover for the box, which would
> make an awsome display to begin with, and put a couple fans to suck air
> out of the back of it. Considering the only place I can see where air
> goes out of the box is in the holes that are in the bottom of it so I
> wounder if cool air is entering the box and just falling out of the
> bottom more than it getting rid of hot air that rises to the top.
Any convective air currents will be easily overcome with forced air. Opening the lid on the power pack and using a clear cover _will_ increase the greenhouse effect when the cover is exposed to direct sunlight. (read add heat to the battery pack)
> The other thing that bothers me about thermal cutback is that it will
> limit charge, but will not limit assist. You can still get full assist
> reguardless of how hot you seem to get the thing.
Well it theoretically reduces the thermal load by at least 50%, and there may be a difference in charging vs discharging in NiMH chemistry that further reduces the thermal load during discharge.
> Eventually if you get it hot enough it will stop auto stopping to
> prevent that fast inrush needed to crank over the engine.
Which as I remember is the highest current load on the pack, 80A +- and its cutoff is reflection of the BCM's thermal management.
> The other thought is if I still have the car out of warranty and the
> pack dies I might just have to find a way to fit some prismatic cells
> rather than the cylindrical ones. They are made for higher currents so
> they shouldn't heat up as much.
An interesting challenge. However, the thermal management of these different batteries will also need to be changed for maximum battery life.
A better approach will be to attempt to manage the overall interior temperature of your Insight and reducing (or in winter increasing) its interior temperature and thereby allowing better battery operation.
Secondary to that is improving the battery pack's internal temperature. Accurate temperature measurements need to be made as a starting baseline so that it can be seen if there is room for improvement. This might be done through manual operation of the existing fans. And or improvement of the existing intake and exhaust points, possibly directly ducting some of the Heat/AC directly toward the existing intake(s) for more rapid cooling/heating (in winter).
An accurate thermocouple probe with readings adjacent to the existing thermo sensors will define the sensor resistance value(s) as they relate to temperature and allow easier gathering of data identical to the BCM's input. After the internal sensors are mapped you would simply need to take an Ohm reading at a relatively easy access connector to determine its thermal value. The most difficult readings will be the cell surface sensor in that you will be dangerously close to a 144v source and that this sensors value is an average for all cells. Any specific point will likely be different and may require multiple points before an accurate sensor resistance correspondence to temperature can be mapped. Fan on operation would also need to be mapped to see if more aggressive fan operation could be of benefit. And cabin air temperature data will need to be time synchronizable with all of the above.
I would think that the batteries thermal mass and the corresponding time factor in warming or cooling the battery pack could be reduced by one or both of the above. And could be anticipated for those in areas that require heavy IMA assist for hills and the like. Anticipation being something that the existing battery management logic simply can't do.
But as you can see without some expensive automated charting equipment its not a weekend task.
Perhaps its best to simply let the experts do their job. I've lost the link but I remember some technical site reviewing the Honda IMA battery pack design. As I remember their harshest finding of fault was that the lowest cell group in the array may not be sufficiently monitored for temperature thus allowing damaging current loads _if_ frozen.
John K. Bullock
aka. Insightful Trekker