Tuesday, November 27, 2012
My new battery pack is amazing!
I got all the batteries installed at work today. It required a few new battery cables because the posts are located differently on these new ones. To clear things up, I am using three of my original AGMs with nine new AGMs, a Paccar/TRP rebadged Deka 8A27M.
Let me just say that I cannot believe what a difference it made. I can accelerate...well....like a "normal" car while voltage sags to maybe 69V where it used to go to 62-63 before. As a matter of fact, during my long wide open throttle hill climb on the way home, system voltage never fell below 67V (11.2V/battery, 1.86VPC). I reached 60 km/h on the hill in second where I used to reach 55 km/h. With the old pack I could go into 3rd and "amp" my way up to 60 km/h so I can't imagine what the eBooger will be able to do now if I really want to torture the new pack and do the same.
All 12V pairs stayed dead even with each other. Plus, there was no degradation of performance by the time I got home.
Next I fully turn my attention to my PWM field controller.
Posted by James Voth at 8:02 PM
Thursday, November 15, 2012
It really pains me to say that I have given up on Paccar Dual-Purpose truck batteries. Simply put, my car murders them VERY quickly. I have spend the last week crunching numbers on various battery options. I need to do something fast or I will be walking to work. I have two good group 31 AGMs in my pack and another [identical] AGM running my accessories.
Option 1: Lithium. $3839 for 100aH (including HST sales tax) + shipping. That's WAY more than the amount I have into the car so far.
Option 2: Walmart Marine Batteries. 10 X $1000 + HST = $1120. A cheap pack, but are they going to last any longer than my current style batteries? I doubt it.
Option 3: I found out that the Paccar (did I mention that I work at a Paccar truck dealership??) BA29D51 AGM "Dual Purpose" battery is made by East Penn/Deka (Same as MK) and is a 8A27 (group 27). I can buy them at cost for $147/ea, and then I only need 9 because I can use all three of my current AGMs. That totals $1482.
What have I chosen?
Paccar AGMs, option 3. And I'm pretty excited. I know I have now blown the budget away but at least I will get the performance bonus of AGMs. For those of you who don't know, AGMs have FAR less voltage sag than floodies, and FAR less peukert effect, meaning more range with less aH. They also do not quickly go bad when left with less than a full charge. These 8A27s are 92aH X 2 X 72 = 13.25 kWh.
I took delivery of two of them yesterday (the rest are on backorder) and replaced my weakest pair with them. The drive home revealed how strong they really are. Close to home 3/4 of the way up the hill, all floodie pairs were at 9.0-10.0V (wide open throttle), my original AGM pair was at 11.2V and my new AGM pair was at 11.3V. I am excited for next week when everything stays above 11V at WOT!
Posted by James Voth at 5:43 PM
Wednesday, November 7, 2012
BMS: Battery Management System. Usually a computer controlled gizmo that automatically controls upper cell voltages during charging (and regen braking) and lower cell voltages when they are almost dead.
I needed BMS to diagnose bad battery pairs in my pack made up of batteries of varying types and condition. The only way to truly diagnose battery issues is to monitor the voltage of each pair while I am driving. In other words, while I am putting the batteries through hell.
I already had six small voltmeters sourced from China ready to go - I just hadn't gotten around to executing it. Until yesterday. Now I have a removable BDU. Battery Diagnostic Unit. I just made that up. There's nothing like a good TLA (Three Letter Acronym) to make an idea seem credible. I'll stop now and move on to pictures.
Here is the BDU:
Crude, but awesome. And yes folks, that is a plug from a Caterpillar engine harness.
Here is the BDU in action:
It was very quick to find one pair of batteries that was 2 volts lower under heavy torture than the rest as I was driving home from work. So I split the bad pair to load test them and found another one had bit the dust. Another visit to my secret stash of batteries solved that problem.
The bad news is my car keeps murdering seemingly good batteries. I see a fancy lithium pack in the future. Just not yet.
Posted by James Voth at 11:09 PM