Results tagged “battery” from The GPSy EV Project

Found a great article that describes how to make a LED voltmeter using a chip designed specifically for that, the LM3914. http://www.evconvert.com/article/led-bargraph-battery-monitor

I just won a bid for twelve Prius packs! They should hopefully be arriving later this week or early next.

Update: Batteries arrived and ready to be installed!

Each pack is a 7.2 volts 6.5 Ah prismatic NiMH battery with six cells. I'll be configuring them as 6S2P for 43.2 volts 13 Ah. I'm hoping that I can get at least 60% of the SOC from them (80% to 20% as on the Prius). That would be 43 volts, 7.8 Ah or 335 watt-hours.

This is perfect as I'm currently consuming 200 watts-hours each way with the heavy SLAs. The lighter NiMH packs should get my power consumption down even lower.

Type	Description	Wh	Weight
SLA	Tempest TR35-12 (rated 35Ah) -- 35 Ah @ 36 volts -- I don't get 35Ah, closer to 10 Ah due to Peukerts Specific Energy 35 Wh/kg nominal Specific Energy 10 Wh/kg derated	360 Wh	1 @ 11.8 kg 3 @ 35.4 kg (78 lb)
NiMH	Prius Gen II Battery (rated 6.5Ah) @ 1040 grams -- 13 Ah @ 43.2 volts -- derated 60% for a conservative Ah of 7.8 Ah Module Weight 1040 g Specific Power 1300 W/kg Specific Energy 46 Wh/kg nominal Specific Energy 27 Wh/kg derated	335 Wh	1 @ 1.04 kg 12 @ 12.48 kg (27.5 lb)

It looks like I'll be saving a good 20 kilograms or 50 pounds with only a slight loss in Watt-hours! I will have to bodge up a new battery carrier as the cells need to be kept under compression when being charged.

I just had a nice conversation with one of the staff at BatterySpec.com, which is where I bought my Tempest TR22-12 sealed-lead acid (SLA) battery. I had inquired about a warranty exchange. They denied it but they gave me a really good reason why -- which is why I'm giving them two thumbs up.

The reason my TR22-12 died on my Piaggio is because I had it in a 2 serial 2 parallel configuration with slightly lower capacity Rhino batteries. I had them configured as a bank of Rhinos and a bank of Tempests. The internal resistance of the Tempests is lower than the Rhinos, so the Tempests were discharging faster and this is why one of them failed.

If anything, I should have done a mixed bank of Rhino-Tempest paired with another Rhino-Tempest. This would have protected the Tempests. But in general, mixing different capacity batteries is a big no-no -- which is why my warranty claim was denied.

In any case, my TR35-12 should be good for its purpose so we'll see where to go from there!

All in all, I'm very happy with BatterySpec and glad that they took the trouble to call me to tell me why my warranty claim was denied and why I shouldn't be doing what I had been doing.