4mm Bullet connectors trouble

Alastor

Alastor

1 kW
Joined
Apr 24, 2012
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Greece
Hello mates , i want your help concerning the damn 4mm bullet connectors that get loose all the freaking time.

Well i was lucky this time but i don't really know if i will be that lucky again !!

I have 4 x RC lipos 6s1p 5000 they are all connected via 4mm bullets to form a 12s2p pack.Today i was happy :p making my test ride with my new battery but ..... one of the bullet connectors witch connected the two 6s1p packs to form a 6s2p pack was loosen....One of the packs was 22.86 when i stop my ride....The others where 23.83 and the unplugged one 25.00.

I ordered 20 x Anderson PP30's as replacement for all my existing bullet connectors do you think this will solve the issue i am having ?Bullet connectors are also trouble to anyone else that uses a lot of rc packs together ?

Is there a reliable way to make sure that all packs are well connected in parallel ?In series its easy but the parallel connection ?


Thanks
 
The 4mm HXT bullet connectors are normally reliable, but some seem to be made better than others. I have one on my bike I must replace because it has developed a high resistance.

I also have 12S2P and the packs are formed into 2 x 6S2P. The parallel connections are never disconnected, with the series connectors being plugged/unplugged for charging. This means if a connector wears it should be a series one, and if it fails, the bike will simply stop (or slow down) and I will know immediately that something is wrong.
 
My series connection is taped and is not going anywhere in my setup ... the ones that can get loose are the parallel ones ... and that can be messy :( you see i am having a parallel charging wire so i didn't think of soldering the two packs together.

I found out that the bullet connector from the battery that was unplugged is working with only one connector from the parallel harness wire i marked it and will keep an eye on it till i get the Anderson connectors and replace all parallel string with PP30's.Its so boring to have to tape your connectors in each ride .

I have two cell meters from hobbyking that i might use in the pack with the issue one for each 6s1p pack but i have the impression that this little meter's are consuming quite a lot of power ... any suggestion for an LVC 12s2p or 3p little board that i can use be even safer ?

Thanks again
 
I had even worse luck with andersons coming unplugged in paralell connections. There are thingy's you can buy that help keep them clipped together. However, then you still have the annoying tendency for anderson contacts to back out of the housing. Tape or a clip won't fix that.

Also, 45 amp andersons work poorly on wire above 12 guage, so there is that problem.

My advice is this, replace the one bad bullet, and then tape up paralell connections. Losing one paralell battery really whacks the remaining ones. So a bit of tape might be a hassle, but nothing compared to ovedischarging batteries.
 
Damn .... andersons caving in .... and i was hopping that they will be better from the bullet connectors.

I will need the andersons anyhow in order to make a new series connector because the one from hobbyking has only 14AWG wire and is getting a little hot.
No issue with the wire size i hate anything above 12 AWG anyhow ;)

I will follow your suggestion and will make the parallel connections permanent .I will also make a new series wire with andersons at 12 AWG that i can simple unplug and simple charge the two packs in parallel.And as Punx0r suggested if the andersons fail i will know it because the scooter will stop.That way i will not have to use the cell meters all the time.
 
I ditched the smaller APP pins; Ypedal is right -> go with APP45.

That said, I have noticed some of my series HTX 4mm barrels backing out a bit, although not to disconnection. I was just thinking of a slightly similar problem I have with stub-out connections; Terminations of high-current connections: I take a not-connected end and put heat shrink over the wire-end of the business and seal it off – making a pull-tab terminator out of it. The heat shrink may pull off, so my plan was to either zip-tie it together or use strong thread from the industrial sewing machine… a rather permanent arrangement. Or, there are zip-ties than can be undone, as well as thin Velcro ties. Regardless, the forces that pull the connections apart are slight although constant and in conjunction with vibration. All that is required is a simple way to tie the two connections together – like the APP clips (not the roll pins). Or, hit the male contact with a bit of solder and trim it down with an X-Acto Knife to tighten the contact.

Little digging at Amazon, I found these…

Out of the box, or possibly my cage... KF
 
Hmm. I have never had a 4mm come even close to coming disconnected. I have Andersons also and haven't had trouble with them either as far as coming unplugged. Have had an issue with my poor crimping on small gauge wire. Maybe it depends on the company that sells the bullet connectors; perhaps some are made better than others. I get them from EPBuddy, a really good distributor in the US. There is no way in heck I can imagine them coming loose. They are actually kind of difficult to get apart, relative to (at least the small) Andersons, if my hand is the least bit sweaty. I am pretty sure I could hang my battery pack from the bullet connectors and it would still be connected. I have noticed that it is easy not to get the pins and sockets completed inserted into the holders though. I saw a tip somewhere that suggested using the opposite mating connector not in the housing to completely seat the connector. That works well.
 
pdf said:
Hmm. I have never had a 4mm come even close to coming disconnected. I have Andersons also and haven't had trouble with them either as far as coming unplugged. Have had an issue with my poor crimping on small gauge wire. Maybe it depends on the company that sells the bullet connectors; perhaps some are made better than others. I get them from EPBuddy, a really good distributor in the US. There is no way in heck I can imagine them coming loose. They are actually kind of difficult to get apart, relative to (at least the small) Andersons, if my hand is the least bit sweaty. I am pretty sure I could hang my battery pack from the bullet connectors and it would still be connected. I have noticed that it is easy not to get the pins and sockets completed inserted into the holders though. I saw a tip somewhere that suggested using the opposite mating connector not in the housing to completely seat the connector. That works well.
Click to expand...

I took all my stuff from hobbyking i am not happy with the quality in harness wires at all :shock: .I as well saw that some bullet connectors are better than others.Some connectors even makes a nice pop sound and fit perfectly when you connect them and some others do not and can be unplugged with very little force !! even from the vibrations while riding this is probably my case today.

I have the andersons ordered and if i experience any more trouble i will replace the bullets.

I am happy that the poor solo battery didn't fell under 22.6 volts.

Any suggestions of an LVC ? for lipos not cell meters

thanks again mates for all the help
 
The male bullet connectors are spring tension type that plug into the female. Over time they will loose tension, but you can use a screwdriver or other tool to spread them apart again many times to maintain a good connection. I've never had a connection come loose because if it feels weak when I plug it in, I fix it. If you can't get to it with a screwdriver you might try using a rod and taping it with a hammer to expand the spring part.
 
That's strange, i've never had mine loose connection either. Are you sure that nothing is tugging on your connections?
 
neptronix said:
That's strange, i've never had mine loose connection either. Are you sure that nothing is tugging on your connections?
Click to expand...

Yea nothing was tugging on the connectors.After some tests i did i found out that the male connectors side in one of the batteries is a little deformed from a spark perhaps.That probably happened the time the connector disconnected while i was riding.

After all i taped em all out after ensuring that the connection is good.
 
This may be a silly question, but if you currently have permanent series connections, I assume you are charging at 12S?

If so, why not make all connections (series and parallel) permanent? So you run 12S2P on the bike and also charge at 12S2P?
 
Something along the same idea as wesnewell: instead of trying to open up the male connectors, just grab a pair of pliers and pinch down the female bullets into a slight egg shape firms up the bullets everytime! I've never had a problem since doing it to every female bullet in my packs
 
Doesn't that tend to make the bullet only contact at two of the four contact points on the male? I'd say tweaking the males out would be best, but you do have to remove them from the housing to do that.

The problem is not that dissimilar with either type of connector. Tape em up seems to work fine if in a place they might snag and yank loose. Andersons with properly aligned contacts don't tend to pull out of the housings. You just gotta learn to bend the tip down if they don't click in solid. 45 amp contacts would have been better, but ordering more contacts is cheap compared to the housings.

Currently, I am running parallel y adapters with bullets on the battery side, and andersons that are on the other end. They make my newer packs compatible with older packs that have permanent paralell connections and andersons. So in this setup, all the paralell bullet connections are taped up. If a series connection shakes loose, the bike just stops, no big deal.

In this setup, my bullet connectors don't get any wear. The andersons do, but they can hack that better in my opinion. I just find it easiest now, to make harnesses rather than permanently modify packs.
 
I have some more news ...i am so lipo noob that i didn't connect the bullet connectors all the way down.....OOOOO my god hahahahaha at least i learned something.Only one of my male bullets was a little bit deformed but i made it the right shape again by removing some plastic.

Punx0r
Lol by permanent i wanted to say ( bullet connector's with tape ) ofc i do parallel charging.

crusoe
You are right man the connectors that do the nice pop sound and having nice connection and a nice one are not a perfect circle but have a little tiny egg shape.I will try to pinch em now a little bit and see the results.Its working all my connectors fit perfectly now (and all the way down :p ).

dogman
The egg shape just a pinch to achieve.I will follow your suggestion and not going to permanent connect em after all.

P.S.
Imagine me riding with all my bike without connecting all the way down the bullet connectors and have your laugh :)

Thanks again for all the help again mates and sorry for wasting your time apparently ...
 
I had a similar problem but with a poor solder joint on my Turnigy. I'm soldering the power and balance leads together like on my first bike to minimize the danger of unparalleled cells. It's just too hard to notice until it's too late.
 
23skidoo said:
I had a similar problem but with a poor solder joint on my Turnigy. I'm soldering the power and balance leads together like on my first bike to minimize the danger of unparalleled cells. It's just too hard to notice until it's too late.
Click to expand...

That's why when i make something new i test it out thoroughly first.

Unparalleled cells can be real hazard if you don't be careful.In my case i have 20A max load out of 2x6s2p 5ah packs even when one pack was disconnected the other battery was not stressed from the load.Also i saw that the battery voltage was dropping quickly and the battery thermometer picked up some calcium so i figured out that something was not ok.

Now its working perfectly :wink:
 
Testing parallel systems at low discharge at first can reveal a bad parallel connection without damaging the battery.

How does one thoroughly test connectors that work 99 times out of 100 times?

For the main connector, the problem is obvious. For the parallel connectors, it isn't.
 
23skidoo said:
Testing parallel systems at low discharge at first can reveal a bad parallel connection without damaging the battery.

How does one thoroughly test connectors that work 99 times out of 100 times?

For the main connector, the problem is obvious. For the parallel connectors, it isn't.
Click to expand...

In my opinion you just have to know how your battery behaves normally.If the voltage drops quickly there is an issue.
There are other solutions as well a watt meter or CA for example.
 
Both times I had a pack unplug, leaving a single pack pulling the whole load, I was having too much fun to notice till I smelled the pack venting and puffing and getting all hot. In one case, plastic melted and the pack looked just about ready to go off. Another reason riding with gloves can be a good idea.

Both of those times, an anderson shook loose, housing and all.

Haven't had the problem since. I make sure andersons are cliked in good, then tape em on paralell connections. Newer packs have the bullets, and I tape them too. So only series connections can disconnect, with no harm done then.
 
Thought id bump this thread with a mod which, hopefully might help this problem.

I salvaged quite a lot of brass bullets from some scrap items recently.
What i noticed with these is what i think is a silicon rubber insert that slots down the middle and helps keep the male bullet spread.
I swapped a few into some HK 5.5mms for a pack rebuild.
The connections are really tight now, sweet.
View attachment 2
20121101_145930.jpg

Now getting them in bulk hmmm.
 
Its silicone rubber cord.
4mm bullet might need a 2 or2.5mm insert guessing.
Havnt got them myself only the polymax 5.5's @ 3mm insert.
 
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