CHARGE MODE LiPo cells require special charge modes that alter charge current as voltage rises to keep below a max voltage per cell. For this reason, charging on anything other than LiPo mode is very dangerous and has one of the greatest potentials of starting a fire. Some chargers have auto-detect features to safeguard against this, but many units don’t, thereby allowing LiPo packs to be charged on, say, NiMh mode, which is very dangerous. Maximum voltage is also a concern, with standard LiPo maxing out at 4.22V per cell. Anything higher is bad unless you’re using the somewhat new high-voltage LiHV packs; but this is a beginner article, so we’ll leave that for another day. There isn’t much more to say here other than make sure you’re charging your lithium packs with a good-quality charger on the correct mode with a safe peak voltage. CHARGE RATE The higher the charge rate, the faster the charge and the greater the “punch,” so it can be tempting to crank it up; but don’t. The simple rule is to charge at 1C—or close to it— which is one times the current of the battery. For example, if you have a 5000mAh pack, charge it at 5000mA, or 5A (to keep units consistent). Some cells allow for 2C or even more, as regards charge current, but for the greatest safety, stick to 1C. On a technical note, most drivers don’t like charging faster than 1C anyway, as it induces a higher initial voltage that makes your car harder to drive at first, as the power is much greater, but it quickly tapers down to the standard discharge curve anyway. This extra initial speed makes it difficult to downside jumps or time corners, making reasonable charge rates not only safer but also more consistent on the track. Newer HV cells have a higher voltage ... here we go again! WWW.VRCMAG.COM 29
Velocity RC Cars Magazine VRC_031
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