17. Chargers and balancers
Its important to choose a good battery charger that is suitable for charging your type of
batteries. Do not go cheap, as you will inevitably want to upgrade to a better & faster charger in
a short space of time. Ideally, you will buy a charger that can handle both lithium based and
Nimh cells, that way you are ready for a lipo or A123 upgrade in the future without having to buy
a new charger. A good charger will allow you to charge upto 14 cells or 6s lipo, and charge at a
1c rate (1c = batteries mah capacity, 1amp = 1000mah). This is important as some chargers
have a lower wattage rating than others, and therefore must lower their charge current (in amps)
when charging a high voltage battery pack, in order to stay within that wattage rating, EG:
A 50watt charger will drop to around 3.5amps when charging a 4s (14.8v) lipo 4000mah pack.
To workout how powerful your charger needs to be to charge a pack at 1c, simply multiply the
fully charged voltage of your biggest pack, say 6s lipo (25.2v) by its capacity in amps, say 5amps
(5000mah), which gives you 126watts. You will therefore need a charger that is rated for about
120watts or more, though generally speaking 50-100watts is more the norm that you will find in
terms of mains powered chargers.
If your charger is a DC type, it will need a power supply that is capable of outputting sufficient
amps to power the charger, same rules apply basically when looking at power supply specs. An
old PC is a good source for a good strong power supply, though it will require some modifications
to serve its new function. Finally are balancers, which were covered before in section 16, but
there is a little more to add. When choosing lipo or A123 battery packs with balance taps, it is
important to concider the type of tap they come fitted with, as there are a dozen or so different
brands/styles, and you may need to find a suitable adaptor so that your lipo battery can be
balanced by your balancer. My advice is to choose the most common brand of tap when you are
given the option (some stores allow you to choose the brand of tap you want fitted to your
packs), and always choose that type whenever you buy new batteries. It is no great hardship to
rewire a lipo pack, or to find a suitable adaptor, it just requires a lot of searching around and
head scratching usually, but that is the nature of the hobby really; welcome to the wonderful
world of RC.
TUTORIALS
CONTENTS:
1. Lithium Batteries
2. Brushless power systems
3. Low Voltage Cutoffs
1. Lithium batteries
What voltage?
What capacity?
What size?
What C rating?
Which brand?
What runtime?
What charge rate?
What about balancing?
What about series vs parallel?
Waterproofing?
Puffing?
What voltage?
In the stock Emaxx, the Evx2 is equipped with a pair of battery leads, each one intended for use
with a 2s lipo (7.4v), giving a total of 4s lipo (16.8v). It is best to use a pair of matching 2s lipos
for space and weight reasons, but it is entirely possible to use a single 4s lipo. To do this, you
must connect the 4s lipo to the BEC side of the Evx2, and then use a jumper to short circuit the
un-used battery input leads. This diagram explains how:
(28 Seiten)
(116 Seiten)
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