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Old Jan 23, 2013, 12:20 PM
theothercliff is offline
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Temple, GA, USA
Joined Jun 2009
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Confusing 4mm red plastic bullet connector wiring

To efx: here is more detail about parallel adapters with the kind of connector that you have.

Red wires are supposed to be positive and and black wires are supposed to be negative.

I have a friend who is an electrician who absentmindedly plugged two batteries straight together with these connectors. He got them back apart in less than a second, but the connecters were blackened by then. The rule that he should have followed is before connecting, make sure black goes to black and red goes to red.

Notice that on the battery (or anything that gives power) the red wire has the larger plastic connector sleeve and has the female metal connector inside. Notice that on the ESC (or anything that receives power) the red wire has the smaller plastic connector sleeve and the male metal connector inside. This allows you to plug the red wire into the red wire and the black wire into the black wire, but it means that power sources (e.g. batteries) and loads (e.g. ESC's) must be wired differently.

A simple extension cord for this type of connector is the most confusing. It has a different wiring on each end because the side that plugs into the battery must act like an ESC and the side that plugs into the ESC must act like a battery. The confusing part is that you can swap sides with this extension cord. When you plug this extension cord in backwards to the battery, you have put the positive on the black extension wire. It will work because the red battery wire is actually connected to the red ESC wire even though it connects through a black extension wire.

Watt meters act like an extension wire. You run the motor as normally, but you can read the meter as it runs. You plug the battery into one end and the ESC into the other end, but yours is not wired that way. Either you need an adapter on the right (load) side or they have the wrong color wire on the right side. I would plug a battery into the left (source) side and measure the DC volts (NOT AMPS) on the right side to make sure the polarity matches the wire color. I would not plug a load (ESC) into it (right side) until I knew the polarity was correct, because you will be plugging black wires into red wires (which may be right or may be wrong) if you do.

A parallel battery adapter is an extension with two plugs to connect to batteries and one plug to connect to the ESC. Imagine two separate complete extensions on the table in front of you with the side that connects to the battery on the left and the side that connects to the ESC on the right. On one extension, strip away about a half inch of insulation from both wires in the middle of the extension. On the other extension, cut it in half and throw away the right half. Strip a half inch of insulation from the ends of the remaining piece. Place it on top of the full length extension with the half piece to the left where it came from. Solder red to red and black to black. The best way to do this is to actually cut the full length one in half in the middle so you can slip two pieces of heat shrink tubing (one each for red and black wires) on before soldering. I actually use 3 pieces, one for red, one for black and one big one over both. Of course you can do this starting with wire and connectors, but it gets confusing with the red and black wire, the male and female metal connectors and the large and small parts of the plastic connector hood.

When done, you plug two batteries in on the left side, making sure that black goes to black and red to red. After that, the right side connector acts just like a single, bigger battery.

You only plug one battery into the watt meter at a time. You plug it into the left (source) side. This paralleled battery acts just like one battery.

If you are going to make a Y adapter first get some pigtails with connectors already on them or some wire and connectors. If you buy pigtails, they will be inclrrectly colored for either the left side or the right side. You can fix that with colored heat shrink tubing. Better yet either buy one pre-made or buy two extensions and assemble as described above.

For anyone reading this, be aware that you should never parallel a discharged battery with a charged battery. The charged one will try to charge the discharged one way too fast, damaging your batteries and possibly causing a fire. You should never ever parallel two batteries that have a different number of cells or chemistry for a similar reason. It is perfectly safe and reasonable to parallel a big battery with a small battery or an old battey with a new battery, just make sure they are both fully charged. I go the extra step of measuring voltage to make sure they are within a tenth of a volt of each other before connecting them together.

The balance connector is a different issue. These batteries should be disconnected from each other so they can be charged and balanced separately. If you have a Lipo alarm that connects to your balance connector, connect it to one or the other pack. I would connect it to my oldest, least balanced or most expensive pack. You should not parallel your balance connectors when discharging because a single low cell can cause a large current to flow through the small balance connector.

Edit: I see you have already successfully made a Y adapter and got your watt meter figured out. I'll leave this here in case someone else needs it.
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Last edited by theothercliff; Jan 23, 2013 at 12:29 PM.
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