Archive for the ‘Lipo Batteries’ Category

https://hpisavagex46.wordpress.com. As you can see from my previous blog post, I ordered me a new Kyosho Ultima DB. It came stock with Tamiya battery connectors. Tamiya connectors can’t take high voltages (they’ll melt!), so I have to put the Lipo packs away for awhile. Until my new soldering iron arrives, I’ve to use either my existing Nickel Metal Hydride or Nickel Cadnium battery stick packs. My first run with NiCd’s seemed to produce quite good throttle response and acceleration. So, I thought, this calls for a time of comparison and discovery, to see whether NiMh or NiCd batteries are better.

Nimh Battery with Tamiya Connectors

Nimh Battery with Tamiya Connectors

NiCd Battery Pack with Tamiya Connector

NiCd Battery Pack with Tamiya Connector

Here’s a helpful RC Battery Type Comparison from http://www.rccartips.com/rc-car-batteries.htm

Type Pro Con
LIPO
  • Cheap
  • No memory effect
  • Powerful
  • Very light, typically only 250grams
  • Can be charged and used several times in a day
  • Will burst into fire if overcharged or punctured
  • Not recommended for beginners
NiMH
  • Can be used twice a day
  • Powerful
  • Very heavy, typically 400grams
  • Takes a long time to charge and sometimes needs both temp and peak detection chargers
  • Memory effect
NiCad
  • Cheap
  • Relatively durable even if abused
  • Old technology
  • Lacks power and capacity
  • Heavy at around 350grams
  • Memory effect

In addition, here are some following notes from http://www.rccartips.com/rc-car-batteries.htm

About the 7.2 volt battery

Your rc car or truck uses a 7.2 volt battery pack to power the electric motor, and most cases, the receiver.

The 7.2 volt battery pack is made up of six 1.2 volt sub-c sized batteries soldered in a series configuration (6 x 1.2 volts = 7.2 volts).

There are two physical configurations… the stick pack and the side by side pack. Both are 7.2 volts, except that the side by side pack is slightly wider.

Update: Lipos have a different configuration. 1S = 3.7v, 2S = 7.4v.

NiCad vs. NiMH rechargeable batteries

There are two popular types of rechargeable batteries, the nickel cadmium (NiCad) and the Nickel Metal Hydride (NiMH).

The NiCad is the old battery technology. It is still good for beginners and playing around. The good thing is that these batteries are now cheap (e.g. $12 USD). The bad news is that these batteries develop memory.

Memory means that these batteries remember their last charge. For example, if you use only 80% of the battery, then recharge it, the battery will only charge to 80% of its maximum capacity. This is not what we want.

To work around this memory effect, racers usually discharge the battery completely, before recharging.

The NiMH is the new battery technology. These are more expensive than the NiCad but do not have the memory effect. NiMH also are designed to have more capacity, usually 3000mAH.

Note: Battery capacity is measured in milli ampere hours. For example, an rc car using a 2400mAH battery will run twice as long as a car using a 1200mAH battery.

Tip: Remember, a battery with higher capacity will perform better, but will cost more, and will also weigh more. If you are racing in a stock class, it is sometimes better to use a lower capacity battery that is lighter in weight.

What to do to get the best performance from batteries

Secrets to making your batteries perform better and last longer…

  • Discharge completely before charging.
  • Use a peak detection charger.
  • Charge at a consistent rate, usually 3.5 Amps.
  • Use or cycle the battery (charge, full discharge) at least once a week. (Note: this does not apply to LIPO)
  • Avoid using a battery more than once a day for NiCad and NiMH. For LIPOs you can use several times a day.
  • Avoid charging a warm or hot battery. Let it cool first.

Tips: The higher the charge rate, the higher the voltage and performance, at the sacrifice of lifespan. I usually charge at a 3.5 Amp rate.

Which Holds More Power?
taken from http://en.wikipedia.org/wiki/Nickel-cadmium_battery

Unlike alkaline and zinc-carbon primary cells, a NiCd cell’s terminal voltage only changes a little as it discharges.

The capacity of a nickel cadmium battery is not significantly affected by very high discharge currents. Even with discharge rates as high as 50C, a nickel cadmium will provide very nearly its rated capacity.

This results in a preference for NiCd over NiMH in applications where the current draw on the battery is lower than the battery’s own self-discharge rate (for example, television remote controls). In both types of cell, the self-discharge rate is highest for a full charge state and drops off somewhat for lower charge states. Finally, a similarly sized NiCd battery has a slightly lower internal resistance, and thus can achieve a higher maximum discharge rate (which can be important for applications such as power tools).

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