Out with the bad batteries...

Yesterday was a lot of heavy lifting. I pulled out the 18 old batteries and cleaned them up:

And worked on cleaning up the mess they left behind. The baking soda in the front clearly did its job:

I have some more cleanup and painting to do, perhaps this afternoon. And then, I need to adjust the battery box sizes for the new (shorter) batteries and I can start putting things back in.

P.S. Anybody know something useful to do with 18 8V golf cart batteries? Craigslist does not allow posting them for sale / free. I can certainly recycle them, but they only have about 400 or so partial discharges and generally seem in good shape. It seems a waste not to put them to some good use - solar array energy store? 18 golf carts? Something.

Meet the new boss...

...not quite the same as the old boss. Yesterday, this showed up on my doorstep:

1050 pounds of lead, acid, and packing material. Just like on the ElectroJeep, these are the Concorde AGM-1280T. They are very similar in volume to the US-8VGC:

About an inch shorter, about 10 pounds lighter (56 vs. 67 pounds), and, of course, 12V 80Ah instead of 8V 160Ah. This means my nominal pack size is 17kWh, down from 23kWh, but the convenience of no leaky batteries plus the peppiness from almost 20% lower battery weight and 50% higher voltage will hopefully make up for it.

This weekend will see major operations toward getting back on the road.

Preliminary 216V Front Wiring

Design is in progress on the 216V upgrade. Here is a preliminary drawing of the front wiring. The grey box highlights the replacement relay board. All of the components are sized so that I could upgrade to 316V in the future if I want.


You can also download a PDF.

Time to upgrade the batteries

I am finally sick and tired of the mess that flooded batteries make - the latest is a fault in the HV isolation caused by the acid mess, leading to problems with the 12V system among other things. So, I will be upgrading them to sealed AGM over the next month or so. I thought about lithium, but it is still a little too rich for my blood (I think I would have to spend 10-12K on lithium + BMS).

Here is the plan which I've put in motion:

• 18 Concorde AGM-1280T 80Ah 12V sealed AGM (same as in the ElectroJeep)
• System voltage 216V nominal (230V at full charge, 190V at 10% SOC)
• Manzanita Micro PFC-20 charger (same as in the ElectroJeep)
• Manzanita Micro Mk2 analog regulators (so as not to kill the batteries via inbalance)
• Upgraded DC-DC converter (probably the APS-55 220V - the Zivan NG1 was suggested but I have worries about its use at other than full charge)
• Various other upgraded components (relays, fuses, heater contactor, battery interconnects, etc.)

This will give me 17kWh nominal pack size (compared with 23kWh for the floodies) - but I'm willing to live with the potentially 25% reduced range for the tradeoff in reliability, convenience, and power (the pack will weigh about 200 lbs less than the original, and the higher voltage will gain perhaps 10% in performance, for a net of nearly 20% perf gain)

Stay tuned, I'll update with more details as they evolve.

Retrospective: design decisions

Just over a year after getting the Volt914 running, I've spent some time thinking of "if I had to do it all over again...". First - choice of motors (AC vs. DC). I'm occasionally disappointed at the performance of the AC24 motor. So I played a "what-if" game - I found some power output curves of the original 1.8L engine in the 914, and plotted a curve of horsepower vs. speed (assuming that one would always shift to maximize horsepower). I added curves for the AC24 as well as the Advanced DC 9":


You can clearly see that the AC24 is lower performance than the original motor, not even taking the extra weight of the batteries into account. The ADC 9" is generally higher performance until you get to 60 MPH or so - probably even taking battery weight into account.

So, if performance is your desired goal - go with DC. I do believe the range of the AC option is greater - higher efficiency, lower HP in general, the option of regen braking. Given that I mostly commute with the volt914, I think I made the right choice.

The next "what-if" game involves batteries. I'm somewhat discouraged by the acid issues with the Zivan charger and floodies. So much so that I'm saving my pennies for an upgrade this summer. I'll either go with AGMs (and a new charger) or, optimistically, something exotic if the prices have dropped enough. Stay tuned.

Other than those considerations, though, I'm very happy I did this project.

Sigh - more leaky batteries

I knew in my gut that the front batteries were probably leaking like the rear ones were. Last weekend, I finally got around to removing the front battery box so I could see how bad it was. Pretty bad:


The front box is a pain to remove because of all the relays, batteries, DC-DC converter, etc. that are attached to it. You can see all the little green masking tape labels I put on all the wires to make sure I got things put back together correctly.

Here is the front compartment after attacking it with a wire wheel on my angle grinder:


It was warm enough that day to put a couple of coats of spray paint on it, so I did:


I went to Sam's Club and got 4 12-pound bags of baking soda. I put about 6 pounds below the front rack (looks like snow!):


I put about 1/4" or so inside the front battery box:


For good measure, I put some below the middle battery box (not shown) and inside the middle battery box (that's the ElectroJeep in the background - sealed batteries, no acid leaks there...):


Hopefully the baking soda will neutralize the acid spills as they happen. But this is something I will have to check every several months.

Electric New Year

Happy New Year! The Volt914 is still running well. Today, I mounted an "ELECTRIC" label on the back just for fun. I hope everyone's conversion projects are successful in 2009. In case you had not noticed, my activity is nearly 100% on the ElectroJeep these days - come on by!