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(Original by Phil Sensibaugh, edited by Bill Pickl)
Since RC combat warships are battery powered selecting batteries for a ship is something all skippers must do. Two different types of batteries are typically used 1) Nickel Cadmium and Nickel Metal Hydroxide (NiCad and NiMH) and 2) Sealed lead acid (SLA). There are also other types of batteries available, but they are more expensive and require specialized chargers so they are rarely used in our hobby.
NiCad/NiMH batteries typically have about twice the power density of a SLA battery, but cost 2 to 4 times as much. NiMH is much better than the old technology (NiCad) that it is replacing. . NiMH is a newer version of NiCad batteries, which not only packs in more power in the same size cell, but also eliminates the need for complete cycling (running the battery till dead). NiMH typically, however, do not support fast charging. NiCad batteries on the other hand support fast charging, but require complete cycling for the maximum service life. Because of the cost NiMH packs are typically used in boats where space and weight are a premium and long run times are not required, i.e. medium cruisers down to destroyers. I recommend buying NiMH over NiCad and both types of cells can be found at reasonable prices from surplus houses or new from internet suppliers such as www.houseofbatteries.com or www.cheapbatteries.com.
As stated above SLA batteries are heavier, but much cheaper than NiMH/NiCad batteries. When you need to pack 14 amp hours of power into a battleship SLA batteries are the only economical choice. Sealed lead acid (SLA) batteries require a slow or moderate charging rate and fast charging can destroy the battery. Therefore you must either size your SLA to last all day or carry a charged set of spares since you will not be able to recharge them quickly enough pond side. SLAs also have a maximum discharge rate limit that is lower than a similarly sized NiMH battery. SLAs can be used for transports, cruisers and battleships, although the cruiser application may be a bit tricky if your weight is at a premium. SLA batteries can be obtained through BDE, surplus houses or online distributors such as www.aventrade.com.
3.1.1 Battery Chargers
(Original by Phil Sensibaugh, edited by Bill Pickl)
Typically, each of these types of battery requires its own charger and using the wrong charger will reduce battery performance and possibly lessen the life of, or even destroy the battery. Any battery can be destroyed by over charging. There are commercially available chargers for all batteries, but not all battery chargers are created equal.
For NiCad/NiMH a good charger will support a range of voltages automatically, have adjustable current charge rate and a flat-peak voltage detection circuit, which reduces the charge rate to a trickle or stops the charging altogether when the battery is fully charged. Another good feature is a temperature probe that attaches to your pack to ensure you don't cook the batteries. Moderately priced chargers may support only two voltages at a fixed charge rate with peak voltage detection and trickle charge. Less expensive chargers employ a timer to shut off the charger or reduce the charge rate to a trickle after a preset time. The cheapest just charge at a preset rate until you remember to remove the battery from the charger. I do not recommend this type of charger at all, but if you can't afford better do not use a charge rating higher than 1/20th of the amp hour rating since most batteries can tolerate this load indefinitely without significant damage to the battery.
For SLA batteries a good charger will support both 6 and 12 volt, have adjustable current charge rate and a peak voltage detection circuit, which reduces the charge rate to a trickle or stops the charging altogether when the battery is fully charged. Moderately priced down to cheap have the same characteristics as those for NiMH above, but typically will have a max of 1 to 2 amp current rating to prevent damage to the battery (you'll need less than that if sizing the cheap option i.e. 1/20th of the amp hour rating).
3.1.2 Battery Capacity
(Original by Phil Sensibaugh, edited by Bill Pickl)
How long will a battery power your boat on combat day? At a given load this is determined by the amp hour capacity of the battery. The ampere hour capacity of a battery is defined as the time required to discharge a battery to a specified point on its voltage (Continued on page 5)
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