Sunday, July 31, 2011

Charging up....

At last, the batteries are installed and the wiring is connected! The pack is doing it's first charge cycle. Along the way, there were some interesting incidents.

Upon connecting the LIN HUB for the first time, the LED indicator panel showed a red LED "wiring fault" and the main display showed that the "battery capacity" was 0%. Yet no alarms were showing and going through the screens, it appeared as though each battery circuit board was being polled successfully. Also, when the charger was plugged in, the individual battery voltages seemed to be charging correctly. The fix was simple. Leave the charger plugged in. Then go through the settings. I found the unit was set as a zero AH pack. So, entering 60AH for my 16 cell pack size turned off the fault LED and updated the bar graph to show 100% capacity. The main pack, fully charged, shows 53.8V.

Another interesting incident. When I powered up the DC-DC converter, the charge controller for the accessory 12V battery was flashing that it was having trouble charging. I found the problem rather quickly. I had wired it in backwards! The battery was trying to charge the DC-DC converter, obviously failing to do so. Fortunately, no damage was done. After reversing, the unit appears to be charging the 12v battery properly. However, the charge controller, being only a 7A unit, seems to be on continuously even though no load other than the BMS is drawing from the battery. So, it's hard to establish that this circuit is charge limiting. At least I know the 12V pack, initially charged, was at 12.9V. I'll be measuring that voltage again later.

For now, the pack charger is removed when not in use. A mount will be constructed and the charger installed into it. After, it will be time to take the BugE out on it's first drive with the new pack.

On my BugE, all lighting plus the BMS is directly powered by the 12V battery. I did this since the battery safety cutoff circuit should stop all power being drawn from the pack including the DC-DC converter. That means in the event of a battery cutoff during a journey, not only would the BugE have no power, but it also would not be able to signal to other traffic that it had a problem!

I built my own wiring harness. The 12V system was built to be completely independent of the bottom of the BugE. That way, during assembly, I could just plug the + and - into the cowl lighting to test all lighting plus speedometer indicator lights without requiring the rest of the BugE to be present. Both cowl lighting and BMS run directly off a12V accessory battery (autocraft part#5L-BS). The size of the battery was picked due to it being on sale rather than being an optimal size. However, that battery size seems to work just fine. To charge the battery, I use a Sevcon DC-DC converter to feed into an ICP 7Amp solar charge controller. Not that either are optimal components. Both are much more expensive than are needed. However, to preserve the ability to go back to a lead-acid pack with no need for a supplemental accessory battery, I decided to keep the DC-DC converter arrangement as-is for now.

Post construction note:
If I were starting from scratch again, I would not muck about with a DC-DC converter at all. The weight savings isn't a big enough benefit. Instead, I would simply use a motorcycle battery with a separate 12v battery charger, mounted on the tail shelf where my DC-DC converter now sits.

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