Recently in Lithium (LiPo, Li-Ion, LiFePo, etc.) Category

I'm thinking of getting a new battery system for my EV conversion. Right now I'm using a Prius Gen 2 NiMH pack in a 6S2P setup (43.2 volts nominal @ 13 Ah), which cost me $144 in December of 2009. I can conservatively pull about 330 watt-Hours, so it works out to 43 cents per Watt-hour.

(Nominally it is 561 Wh for the pack, but there is considerable voltage sag at the end which reduces the amount of energy I can extract). The nominal price/performance is 26 c/Wh….

Let's price out some LiPo solutions….

18650 cell (single)	LiPo	$4	2.4 Ah	3.7V	8.8 Wh	45c / Wh
18650 cell (single)	LiPo	$7	2.8 Ah	3.7V	10.36 Wh	68c / Wh
Zippy Flightmax 8000 mAh 6S1P 30C	LiPo	$88	8 Ah	22V	178Wh	49c / Wh
Zippy Flightmax 8000 mAh 5S1P 30C	LiPo	$74	8 Ah	18.5V	148Wh	50c / Wh
Zippy Flightmax 8000 mAh 4S1P 30C	LiPo	$58	8 Ah	14.8V	118Wh	49c / Wh
Zippy Flightmax 8000 mAh 2S1P 30C	LiPo	$28	8 Ah	7.4V	59Wh	48c / Wh
Turnigy 5800 mAh 8S 25C	LiPo	$100	5.8 Ah	29.6V	172 Wh	58c / Wh
Zippy 5000 mAh 10S 25C	LiPo	$106	5 Ah	37V	185 Wh	57c / Wh

I checked the prices in May (2013.05.20) and there was no change in prices. But there are some bigger cells coming on the market which might change things. This is from dealextreme.com:

26650 cell (single)

LiPo

$7.60

6.0 Ah

3.7V

22.2 Wh

34c / Wh

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.