Well, over the last few weeks I have been testing lithium polymer batteries (Lipos)against nickel metal hydride batteries (Nimh -5 cell version).  To date, I have only used LRP products (4200 Big Mama cells and 5300mah Lipo) until this weekend.  And in my testing to date, I have found that there has been a significant difference between 5 cell Nimh and a 7.4v Lipo, but I thought there would be as it wasn’t a true comparison.  What would have been fairer and truer to test would be 6 cell Nimh against a 7.4v Lipo.  But All I wanted to do was to see what the hype was with Lipo batteries – was it all it was supposed to be?

Space Cadets: 
Well, I can say putting performance aside for the time being, Lipos have a distinct advantage over Nimh – amount of pit equipment required to charge and maintain batteries and also the reduction in stress levels (for me anyway) to make sure my Nimh batteries are ready for the next race.
My normal list of electronic equipment on my pit space comprises of the following:

1. Power  supply
2. 2 Chargers
3. Battery Heatsink
4. Battery Discharger
5. Tire Warmers and cooker
6. assorted tools (drivers, sockets, camber, droop and ride height gauges, scissors, pliers)
7. Solerding Station
8. Setup Board
9. Clock and temperature gauge

When using Lipos, I do not have to carry or have 2 chargers, battery heatsink, discharger and soldering station. (I will still carry 2 chargers and a soldering station – just in case it is required).  Also, I do not have to spend time thinking about when to put my next battery on charge (timing it to peak just before the start of the next race) and also discharging and equalising the Nimh before and after use. 
Basically, Lipos use less equipment to use and maintain, and seem to be more hassle free.
 
Where the Rubber meets the Road… 
After testing my first Lipo battery, I wanted to see if there were any differences in performance between different rating and brands of Lipos.  My test subjects are:

• LRP 5300 25C (2S2P) – soft cased
• Core 5000 20C (2S1P) – hard cased

I would have thought that if the numbers were correct as published, the LRP would have ‘better’ performance on and off the track.  (LRP: 5300x25C = 132.5amps max continuous vs Core: 5000x20C = 100amps max. continuous).
Setup: 
I did not bench test (cycle) the batteries before using them.  I ran the batteries at my local track – Brendale with LRP TC spec ESC and a LRP 3.5t motor.  Using a 6 cell gear ratio (9.4FDR), and making no setup changes on the car in between runs, there was a noticeable difference bewteen the 2 different brands. 
 
 
Between the two brands, the difference were the initial performance and the drop-off in performance towards the end of a run.  The LRP Lipo was very ‘punchy’ at the start of each run (first 2-3 laps) when compared to the Core Lipo, however the LRP seemed to drop-off in performance quite noticeably towards the last part of the run (last 2 minutes feels like driving a 5 cell Nimh).  The lap times reflect this in each run as the first few laps were about 0.1 sec per lap faster with the LRP Lipo and then once the drop-off point was reached, the LRP Lipo would be between 0.05 to 0.1 sec lap slower than the Core.
The Core Lipo felt very similiar throughtout the run and it did not seem to display any drop-off in performance.  Both batteries seemed to take similiar charges after use (approx. 3500 – 4000mah).
 
Bench Testing:
I wanted to know what the numbers were like compared with a Nimh and also between the LRP and the Core Lipo.  I ‘cycled’ the batteries at home using my LRP Pulsar 3 charger with the following settings:
Lipos :

• 2 cell 7.4v
• 10 amp discharge rate
• 5.0amp charge rate 
• cut off voltage 6.0v

 
Nimh:

• 10 mv delta peak cutt off
• 10 amp discharge rate
• 5.3 amp charge rate
• cut off voltage 6.0v

 
The results are:
LRP Lipo

• 7.569 avg volts
• 4312 mah (discharge capacity)
• 1525 sec (discharge time)

 
Core Lipo

• 7.606 avg volts
• 4774 mah (discharge capacity)
• 1722 sec (discharge time)

 
Nimh

• 7.788 avg volts
• 4372 mah (discharge capacity)
• 1515 sec (discharge time)

All cycles were done at room temperatures.
From the data, the Nimh have a higher avg volt than the Lipos, but without a data logger to plot the discharge curves, I can only infer that the Nimh have a much greater initial discharge curve than the Lipos, but drop-off quicker (as this is what I felt when driving on the track).  The data between the two different brand Lipos is quite surprising.  I would have thought that the LRP with the ‘better’ numbers wuld have been a higher performing battery.  But in both track testing and bench cycling the Core Lipo comes out on top (in all areas – avg volts, capacity and runtime)
 
Bling Time:
I also got my hands on one the of the new Core UDC 20 chargers.  This charger is quite compact and looks the part (chrome black metal with chrome writing/buttons along with a blue backlit lcd display).  The specifications of the charger are:

• Charges – Nimh, Nicad, Lipos, LiLo, and Lead Acid
• Up to 5 cell Lipos
• Charge Rate 5 amps max.
• Balance charge rate of 200mah/cell
• NO discharger

 
The charger also comes with a multitude of different connectors to charge various items (see pic) and also various balance charge connectors.  The charger is very easy to use and operate.  Just follow the prompts on the LCD display.  I have charged both Nimh and Lipos on the charger and it has been flawless.  The main reason why I got this charger is to be able to balance charge my Lipos.  So far, I have balance charged my Lipos (even though it wasn’t required) and I have not noticed any difference in performance.

Pros:

• cost
• small and compact
• great looking
• comes with almost every connector type

 
Cons:

• no discharge feature
• instructions are quite poor (although quite easy to operate if you have used chargers before) 

If you are looking for a small and cost effective charger (only), you can’t really go wrong with the Core UDC-20.
Mastercard:
Cost of:

• Core UDC Charger $100 approx.
• Core 5000mah 20C Lipo $125.00 approx.
• LRP 5300mah 25C Lipo $170.00 approx.
• Not having to carry so much stuff and stress at the track: PRICELESS!

 
Finally:
I will continue Lipo testing and keep you posted on the progress.  I am about to receive a SMC 5000mah 28C (2S2P) Lipo this week along with PPD Lipo balance weight and Diggity Designs Lipo tray.  I will take some pics and let you know on the results.
 

These are my personal comments and findings and in no way am I sponsored or paid in regards to these above mentioned products.