The part of the project that arguably could make or break it. I have thought up two approaches to this issue:
Buy the cheapest off the shelf batteries in Costco and experiment – run a series of on road tests and get and idea of range / capacity in the real world. From here I would have useful stats about increasing power / range.
Buy high end batteries (Trojan look good) then put some real effort into getting the battery design right – and try to get right first time.
Option 1, Costco batteries
Costco have a 12v / 115Ah Marine / Deep cycle battery for $84 – trying to determine the OEM so I can run the numbers with evconvert calculator.
Useful web link: http://www.evconvert.com/tools/evcalc/?s=b
Using 12 batteries = $1008 + GA sales tax (6%)
Brought 2 x Costco batteries purchased for measurements / experimentation
Option 2, Using Trojan 6V
Requires 24 batteries @ $130 / each = $3,120
The most important consideration with the batteries is the potential range. I have settled on 144v in the previous discussion about controller and motor. Using 144v will drive using either 12 x 12v, 18 x 8v or 24 x 6v for the battery configuration.
Option 3, C&D Technologies (Dynasty UPS) – “Max Rate”
David offered option for a set of 12 second hand C&D Technologies AGM cell.
Battery specifications:
12v, AGM, 138Ah capacity
http://www.cdpowercom.com/product/battery/vrla/pdf/mr12_490.pdf
Getting their first charge…
Planned layout
State of charge calculations
| Charge | Volts per battery | Pack voltage |
| 100% | 12.65+ | 152 |
| 75% | 12.45 | 149 |
| 50% | 12.24 | 147 |
| 25% | 12.06 | 144 |
| 0% | 11.85 | 142 |
Battery log / management system
Battery log – Manual measurements of battery voltages before and after various trips.
BMS – Design and work to build a automatic monitoring systems
Journal entries
2009 08 11 – Took delivery of 12 x C & D Technology, Dynasty Series, “Max Rate” AGM batteries
2009 08 12 – Rigged up a parallel charging harness and to allow a low rate charge (2A) using a standard automatic charger (on AGM setting.)
2009 10 19 – Battery racks in place