Recently in Charging Systems Category

I have the Prius NiMH batteries installed and test drove it but the snowstorm of 2009 has put the dampers on harder testing. In any case, here's the new revised bill of materials (BOM) (dated 2009.12):

Base Unit	Piaggio Boxer (1971) - 50 cc 2-stroke internal combustion engine (removed)
Electric Motor	HXT 80-100-B 130Kv Brushless Outrunner from United Hobbies - link to new version of motor - Tachs: 5600 rpm @ 43.2v nominal (4500 rpm @ 36v; 6000 rpm @ 48v) - Max amps drawn: 100A @ 43V - Max watts drawn: ~ 4300 watts - Speed: 45 kph top speed (at current gearing)
Electronic Speed Controller	Castle Creations Phoenix HV-110 (link) - 110 amps @ 50 volts limit
Throttle	Magura 0-5K Potentiometer motorcycle twist grip throttle
Servo Tester (Pot to ESC)	Boman Industries Polar-Matic PC-50 (ebay)
Power Monitor	Cycle Analyst (link)
Batteries	Currently SLA: Prius Gen 2 NiMH - 6S2P packs (12 in total) - 43.2 volts nominal @ 13 Ah - 330 watt-hours (conservative) - Range: unknown
Power Connectors	- Anderson PowerPole 75A on main connections - link - Anderson PowerPole 30A on sub connections - link
Wiring	- 8 gauge stranded copper on main power lines and motor leads - 12 gauge stranded copper on sub power lines
Lighting	- Front lighting using high-power Luxeon LED - Rear lighting using high-power red LEDs
Low Voltage (12/5VDC) Converters	12VDC converter using National Semiconductor LM2576HVT-12-ND buck-converter for motor cooling fan, front lighting (via 5vdc) and rear lighting 12 volt to 5VDC converter using MC34063 Based Switching Regulator for front lighting Another 12VDC converter using National Semiconductor LM2576HVT-12-ND buck-converter for ESC controller cooling Quark Pro BEC 3A UBEC for servo tester / RC components
Things I burned out/destroyed	E-Sky EK2-0907 Servo Tester Doc Wattson power monitor ELF 100 ESC speed controller Castle Creations Phoenix HV-110 Right index finger on burnt out ESC Various burns and scrapes

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.

Revised bill of materials (BOM) (dated 2009.09):

[moved to after the jump]

I just bought a used iMax B6AC charger (LiPo/Li-Ion/NiMH) to complement my previous Turnigy Accucel-8 charger. I had trouble finding the user manual but finally located it. I'm posting a copy here just in case anyone wants it:

• iMax B6AC Charger User Manual (pdf)

And here's a little comparison table that I drew up comparing the iMax with the Turnigy units:

	iMax B6AC	Accucel-6	Accucel-8
Max Power	50 watts	50 W	150 W
Max Current	5.0A	5.0A	7.0A
Max LiPo Cells	6	6	8
Max NiCD/NiMH Cells	15	15	27
Max Pb	20v	20v	36v
Power Input	100-240 VAC 11-18 VDC	10-18 VDC	10-18 VDC

Li-Po batteries have the best power/weight performance of all of the mini battery sizes. If only they'd come down in price more, they'd have more utility. In any case, I'm using small Zippy brand 11.1 volt (3S) 2200 mAh battery packs. The only problem I found is that the balancing connectors on them aren't nearly long enough to reach from my Turnigy charger to my bomb-proof charging container (an old army-surplus ammo case). I tried to see if anyone sold 3S lipo battery connector extensions, but no luck.

Also, my Turnigy charger requires two connections for LiPo balancing -- the main Dean's connector and the balancing connector. This is a pain in the waddle since you can do it with only one connector -- as long as you remain within the relatively low amp constraits of the balancing connector (likely < 5 amp).

To make life difficult, there are apparently four (4) different LiPo balancing connectors in use. My Zippy batteries use the Align standard, which is a JST XH connector. Here's a very handy chart describing the various connectors and which batteries use which connector: http://www.rcaccessory.com/pdf/Battery%20Tap%20Configuration%20Guide.pdf

Now that I know that both my Turnigy charger and my Zippy batteries use JST XH, I just had to go to Digi-Key and order the right parts:

1	10	455-2249-ND	CONN HEADER XH TOP 4POS 2.5MM	JST XH SHROUDED HEADER	0	0.13500	$1.35
2	10	455-2267-ND	CONN HOUSING 2.5MM 4POS	JST XH HOUSING	0	0.05700	$0.57
3	100	455-2261-1-ND	CONN TERM CRIMP XH 26-30AWG	JST CRIMP CONNECTOR	0	0.03340	$3.34
4	10	455-2219-ND	CONN HOUSING 2.5MM XH 3POS	JST XH HOUSING 3 PIN	0	0.05700	$0.57
5	10	455-2248-ND	CONN HEADER XH TOP 3POS 2.5MM	JST XH HEADER 3 PIN	0	0.10000	$1.00

Once the connectors arrive, I'll have enough to play around with them for quite a while!

p.s. Bonus, the same connectors can also be used to create extensions for my LiPo battery monitors.

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.

I stopped riding about a month ago because I had severe sciatica. It's getting better now and so I thought I'd get back on the horse. One thing I had noticed last month is that my Piaggio was barely making it to work where previously it had been able to go there with energy to spare. I thought it was simply the cold weather.

For a related project, I bought a relatively sophisticated balancing charger, the Turnigy Accucel-8 150W 7A Balancer/Charger. One of the reasons I got this particular unit was that it could charge up to 36 volts of SLA; 32.4 volts of NiMH; or 8 cells = 29.6 volts of LiPo. Most other intelligent chargers I've seen can't handle this high a voltage. I want to experiment with switching over to NiMH or LiPO but I didn't want to have to take the packs apart to charge them.

One of the interesting aspects of the charger/discharger/balancer is that it has an accurate ampere-hour gauge, so you can tell exactly how many Ah you are putting in -- or taking out of the battery. I used this to test the various batteries I have in my stable and found quite a few bad packs.

What surprised me, though, was that one of the SLAs that I had been using in the Piaggio had gone bad. My original setup was 2S2P or two parallel sets of 2 serial 12 volt batteries:

 Battery 1: Rhino SLA17-12  (rated 18Ah) = 10.508 Ah @ 2A discharge
 Battery 2: Rhino SLA17-12  (rated 18Ah) = 10.485 Ah @ 2A discharge
 Battery 3: Tempest TR22-12 (rated 22Ah) = 12.092 Ah @ 2A discharge
 Battery 4: Tempest TR22-12 (rated 22Ah) = 1.880 Ah @ 2A discharge

Yikes!!! Very bad. And I had used it for less than two months... But no wonder I wasn't getting any mileage. I was going to just replace the battery with another similar sized one when I decided to see how many Ah were in the larger batteries that were in my power scooter.

 BigBatt #1: Tempest TR35-12 (rated 35Ah) = 30.612 Ah @ 2A discharge
 BigBatt #2: Tempest TR35-12 (rated 35Ah) = 30.539 Ah @ 2A discharge

Wowza..... This blew my mind a little.

• Revelation 1: The big batteries were getting significantly closer to their nominal ratings than the little ones.
• Revelation 2: Two big batteries had more amp-hours than four little ones == 30 Ah @ 24 volts vs. 22 Ah @ 24v
• Revelation 3: The big batteries were 11.8 kg each x 2 = 23.6 kg
• Revelation 4: The little batteries were 6.8 kg each x 4 = 27.2 kg

This all added up to .... it was better to use two big SLAs rather than four little ones because: 1) I would gain 50% more amp-hours; 2) it was lighter; 3) it was smaller; 4) and in hindsight, it would have been much cheaper.

That was easy enough to accept but it meant that I would have to redesign the battery carrier system. This was something I had been planning on doing anyay. More posts to follow.