Battery Connections - why bullets?
 

Hello everyone,

I was wondering why bullets are "the thing" with batteries now? It seems like it's adding what's typically a poor style power connector inline with the battery is counterproductive.

I know we have packs that hang onto voltage a lot better... Has anyone does studies on the resistance of those bullet connections?

here is another thread that was started a while ago:

http://www.rctech.net/forum/radio-el...connector.html

And many in 1/8 are running XT60 connectors now

I think the main reason is because lipos come with bullet sockets, so bullet connectors plug right in. That makes them neat, simple and minimiszies the need for extra connectors. I much prefer bullet connectors to deans connectors or Tamiya connectors.

4mm connectors have been used for decades on things like power supplies, multimeters, audio equipment. I'm not sure of the resistance numbers, but they have worked fine for me. There are a range of high quality connectors available too.

To me it seems like the main disadvantage is that it is possible to plug them in backwards (reverse polarity). I've just adjusted the wiring on the ESC so that the positive lead is only long enough to reach the positive terminal on the battery.

A six year old thread... There are good points there, and all points that are why I'm (so far) standing by my Deans connectors on my batteries. I'm suprised they're "only" runing XT60 in 1/8. I'd expect XT90, but they're also running much higher voltages, which make resistances matter less.

Right. I want to know why that was ever a thing. Who made that decision?

They range from pretty awful, to "acceptable". The only time I've seen bullet connectors used for high current applications is in R/C. There's lots of things I've seen done in R/C, that "I only see" in R/C, those things usually are wrong.

Removing a keyed connector is A BIG DEAL.

I think this needs some testing, and research. The companies I trust to make good decisions are using the 4mm bannana plugs... so maybe i've got something wrong.

What difficulties have you had with bullet connectors? What terminal would you like to see built in to batteries?

The decision to use 4mm terminals was likely based on cost, ease of manufacture, proven use for sustained mid-high current, and selecting a connector designed to be repeatedly plugged and unplugged. I'm really glad to see that fixed leads coming out of a battery case are no longer the usual thing. There was even a time where racers would solder batteries on to the ESC for each run to avoid adding the resistance of connectors- glad that is in the past too.

Are you adding a deans connector on to batteries with 4mm terminals?

Always funny how people think their connector is a huge resistor while from battery up to motor many solder connections are found, solder connections mostly made with a normal high resistance lead-tin solder......

So far? None. I don't use them anywhere but on my voltmeters.

Bannana plugs are not particularly good at carrying high currents. If you look at connections that carry high current, you'll notice something in common. They're almost usually flat, with sprung contacts. That describes both motor brushes, and things like Anderson Powerpole, Electrical Sockets, The fittings for breakers in your breaker box. The exceptions are the power sockets on electric cars, and the contacts for commercial 3-phase extension cords. Those all have sprung pin contacts, with significant spring force on them, which most bullets do not have.

I used to think that too. Lead is still a reasonably good conductor of electricity. (I'll measure some tonight..) But the reality is, on a solder joint, is that there's more wire area than there was with just the copper. The typical solder joint, has much more surface area, than the actual stranded area of the wire. This should lead to a good soldered joint having less resistance than the wire itself. Assuming you know what you're doing....

Connectors range from "huge source of resistance" to "better than the same length of wire". RC Car Action used to do tests, and show you what connectors were better. At the voltages we run, and peak currents, it's definitely to our advantage.

Our motors are "also" rated in KV. Every bit of a volt you can get, gives you more RPM to play with. And more torque when you're not spinning the motor out.

I've welded cheaper bullet connectors.

Before LiPo, wires were commonly soldered directly to the battery, no connector at all. When LiPo was introduced, I believe rules were put in place that a connector must be used with LiPo for safety reasons, as LiPos are much more volatile than the NiCd/NiMH they replaced. You'd have to ask the manufacturers why they chose to standardise on bullets, but they actually work fairly well. You keep saying that the only time you'd use bullets are on multimeters, but they use different types of bullets. In the attached image, the left bullets are the cheaper ones used in many devices, the right ones are typically used for higher performance RC applications.

It's better to have more contact surface in my opinion.

Yeah, I remember. (I got into RC in 88 or so..) The RC connectors have good cross sectional area, but I've seen them inserted, they definitely don't have strong spring pressure. Also... how do we know how the cells are conencted to the inside sockets...

That's why high power connectors are flat plates with high spring pressure. Circular connectors are very hard to get good spring pressure and contact area on.

Something like that, & I'd also suggest that manufacturers also use bullets because of cost savings. With bullets, they don't need to keep as much heavy-gauge wire in stock, which makes pack construction cheaper, plus having less wire in their inventory at the end of the year means they pay less taxes on their inventory(most companies are assessed taxes based on how much of their inventory they keep at the end of a year, that's why many have year-end sales)....:cool:

I would go with the bullet style since that is what electric meters use. The most consistent and the best overall surface area. Spring clips may lock in better but that doesn't mean it has a better resistance. Maybe ohm it out

This is a great way to put it. I have Multimeters, and Meggers, that I have to switch leads and probes on and off for work, all of which still have passed calibration recertification with no issues, minor issues being batter replacements or battery box replacement. And all still have their original probes, leads, and ancillary equipment.

But these all have at the minimum a 4mm bullet style connector, and I have always felt if its good enough to accuratly provide a measured value, its probably decent enough for my RC. No issues, I have never felt that the Bullets have inhibited or led to a decrease in performance.

I use the 4mm Reedy Low pro. Bullet Connectors

My Fluke 189 and 88 both have bullet connectors. If those fail, I die.

Biggest failures with 4mm plugs can be lessened by never unplugging them. I use alligator clamps to charge usually.

I use just the bullet connectors on my pan cars. It makes the wiring very clean.

May be off topic but for all my truggies/buggies I run the castle 6.5 connectors. The things are great and plenty of room to solder large wires in it.