CA­PAC­ITY & VOLT­AGE

RC Car Action - - TECH KNOW -

The im­por­tant things to con­sider when look­ing at any bat­ter­ies, whether NIMH or Lipo, are ca­pac­ity (which de­ter­mines how long your car or truck will run per charge) and volt­age (which de­ter­mines how much speed and power your model will de­liver). Here’s what you need to know:

CA­PAC­ITY

The big num­ber on most bat­tery la­bels (3300, 4000, 5000, etc.) in­di­cates its ca­pac­ity in mil­liamp hours, which is gen­er­ally short­ened to “mah.” The greater the mah num­ber, the longer your car will run per charge (and con­versely, the longer it will take to recharge the pack). “Big­ger num­ber = longer run time” is all you re­ally need to know, but it’s help­ful to un­der­stand what the mah rat­ing ac­tu­ally means. If your bat­tery is rated at 5000mah, that means it can hold a steady 5-amp load for a full hour. We get “5” from “5000” be­cause a mil­liamp is 1/1000 of an amp. Di­vide the mah rat­ing by 1000, and you get amp-hours: 5000 ÷ 1000 = 5. If you have a 6000mah bat­tery, it can hold a 6-amp load for an hour. Or, if the load is 3 amps, that 6000mah will run for two hours. Greater ca­pac­ity = longer run time.

VOLT­AGE

The volt­age of a bat­tery pack is de­ter­mined by how many cells it has. A sin­gle NIMH cell de­liv­ers 1.2 volts, and NIMH bat­ter­ies are most com­monly of­fered with six or seven cells. These may be re­ferred to as “6-cell” and “7-cell” packs, or they may be re­ferred to by their volt­age: 7.2 volts and 8.4 volts (since 6 x 1.2 = 7.2, and 7 x 1.2 = 8.4). It’s dif­fer­ent with Li­pos.

The prin­ci­ple is the same, but since a sin­gle Lipo cell de­liv­ers 3.7 volts, Lipo packs have fewer cells for a given volt­age. The most com­mon con­fig­u­ra­tions are 2-cell, 7.4-volt packs (2 x 3.7 = 7.4) and 3-cell, 11.1V packs. As with ca­pac­ity, more volts is bet­ter—to a point. Your ve­hi­cle’s power sys­tem is de­signed to han­dle a cer­tain amount of volt­age, and ex­ceed­ing that volt­age will, at the very least, shut the sys­tem down if it has “over­volt­age pro­tec­tion” or, at worst, fry the elec­tron­ics. Al­ways check your ve­hi­cle’s (or speed con­trol’s) man­ual for the max­i­mum volt­age spec­i­fi­ca­tion be­fore up­grad­ing to a pack with more volts.

This Dy­na­mite Lipo’s ca­pac­ity is 5000mah, and its volt­age is 11.1 volts.

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