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Wednesday, January 18, 2012

Inexpensive Expensive LiPo Chargers - Head2Head

Update:  See for more charging options.

Update 7/5/12: The Onyx has become unusable, indicating a "Balance Error" a few minutes into charging any battery.  Moved to avoid.

LiPos are great because they pack a lot of punch.  But use them for a while and you'll discover their Achilles heal: inconsistent useful lifespan.  Some swear that if you charge LiPos right, they'll last forever.

I'm not one of those people. 

I've witnessed wide variation in lifespan, power and cost between LiPo brands and a wide variation their willingness to accept a full charge per cell after light to moderate use.

Some LiPos last a long time, but most don't and often times the more expensive batteries quit first: 

E-Flite's terrible across-the-board line of LiPo batteries jump to mind--these are consistently weak performers with no internal wire-lead fold often causing catastrophic failure from terminal connection fatigue.  My best luck has come from inexpensive Turnigy Nano-Tech (regular Turnigys are inconsistent) and also from relatively pricey Hyperion and NRG batteries.  Some of my off-brand LiPos included with direct-from-China PnPs and RTFs have held up the longest. 

But one of the most interesting things is how batteries cooperate with various chargers, especially over time.  The cheap plug-n-play 2-3S balance chargers often do a good job, but those inconsistent balance performance (most of them) seem to beat a battery down pretty quickly.   And with over 100 LiPos from 30 mAh to 5000 mAh in my battery bags forming my biggest RC expense, I've been wanting to do a LiPo charger H2H for quite some time.
For this H2H, I've decided on two inexpensive expensive chargers:  the Dynamite Passport Lipo 6S vs.  the Duratrax Onyx 235.  I wouldn't bother if there weren't large differences between the two.

First the street price and manufacturer Specs:

Dynamite Passport AC/DC Li-Po 6S Charger
- AC Input: 110 to120V (220 to 240V for international version)
- DC Input: 11 to 14V
- Battery Type: Li-Po or Li-Fe
- Battery Cell: Li-Po; 2S to 6S (7.4~22.2V)
- Li-Fe; 2S to 6S (6.4~19.2V)
- Charging Mode: Constant Current/ConstantVoltage (CC/CV)
- Banana plug output for more connector flexibility
- 1, 2, 3, 4 and 5-amp selectable charge rates
- Balance sockets molded into the side of the charger for convenient balance charging
- 12–bit CPU controller provides precise charging
- Memorize the last setting of balance charge automatically
- LED and beeper charge status indicators
- Reverse and short circuit protection
- Durable, compact and portable design with an aluminum casing and plastic end caps
- Built-in cooling fan

Duratrax Onyx 235 Advanced AC/DC Charger
- AC input: 110V AC 60Hz – 240V 50Hz, detachable cord, 50W
- DC input: 11– 15V DC, detachable DC cord with insta-gator clips, 70W
- Battery types: 1– 10 NiCd or NiMH (1.2 – 12.0V), 1– 4 LiPo, Li-Ion, or LiFe (3.7– 14.8V)
- Battery capacity range: 50-9900mAh
- Fast charge current: 0.1– 8.0A linear, adjustable (4C limit for lithiums, 5A limit with AC input)
- Fast charge termination: peak detection for NiCd/MH, cc/cv for lithiums
- Fast charge safety timer: off - 300 minutes
- NiCd/NiMH Peak sensitivity: 3 – 20mV adjustable
- NiCd/NiMHTrickle charge current: auto (1/20 fast chg setting), or manual adjust (0-250mA)
- Lithium Balancing Accuracy: 5mV per cell
- Lithium Balancing Socket: JST EH
- Included balancing adapters: ElectriFly® & FlightPower®/Thunder Power Adapter Board
- Controls: 4 pushbuttons
- Battery memories: 10
- Display type: LCD with backlight
- Setup tones: on / off
- Audible melodies: 5
- Output connections: banana jacks, radio jack, regular USB jack for charging mp3 players, cell phones, etc (5V, 500mA), mini USB for firmware updates
- Included output adapters: Banana plugs to Standard
- Banana plugs to Traxxas®
- Banana plugs to Deans® Ultra® Male
- Protective devices: solid-state reverse polarity and current overload

 The specs and features speak for themselves so I won't recap.  Here is my scoring and rationale:


Dynamite Passport AC/DC Li-Po 6S Charger

Charging Performance: A+
- Consistent 4.2V fully charged, balanced cells 
- No voltage readout

Power/Noise:  A-
- Up to 6S
- Selectable charging speed in 1A increments
- Watt-limit limits charging speed to 3A with 4S+ batteries 
- Thin 2-prong AC lamp cord
- Very noisy fan 
- Beeps once every 10 seconds after charge complete

Desk Space: B+
- Rear AC prevents sitting flush against a back wall
- Convenient, built-in, front mount balance plugs
- Thin 2-prong lamp cord

Setup/Use: A+

- Quick and easy to use  
- Auto-voltage by selection of balance plug
- Easy selection of faster/slower charge rates
- Charge rate only in 1A increments
- Can't charge slower than 1A
- LiPo by default; finicky switching to LiFe mode

Value:  A
- Lowest price with best charge balancing and completeness
- 2-6S
- Misses lower capacity batteries due to 1A min rate

Overall Grade:
- Simple, fast, complete balance charging at a good price.  Too loud.

Duratrax Onyx 230 Advanced AC/DC Charger

Charging Performance: B
- Occasionally leaves a cell undercharged (~ 4.0V)
- Running readout of total V, individual cell V, and charge capacity 
 - Automatic safety timeout

Power/Noise:  A+
- Limited to 4S
- Selectable charge rate in fine 10 mA increments
- Auto-selects a 1 hour charge (charging Amps =mAh rating)
- Very quiet fan
- Beeps only when charge complete

Desk Space: B-
- Needs clumsy tack-on balance board
- Bulky 3-prong power cord
- Large unit

Setup/Use: D

- Onerous menu system requires reading the directions--yuck
- Type, cell count, charge rate, and capacity must be manually entered
- 10 battery memory is self-justified by complexity
- Charge rate in 10 mA increments down to 10 mAh capacity

Value: C
- Captures lower capacity range of 2S-4S LiPos
- Misses higher voltage 5-6S LiPos
- Charges lots of non-LiPo battery types

Overall Grade: 
- Feature packed.  Complicated to use.  Occasionally undercharges a cell.

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