Battery connection adaptors - work of the devil.

[leccyflyer]

Had a very lucky escape a couple of days ago, which further reinforced my opinion that adapters are the work of the devil. Funnily enough, I mentioned just before the flight that I really don't like adaptors. I like to change out the various connectors supplied with batteries and ESCs for the no-fuss 4mm "gold" bullet connectors that have worked very well for decades across most of my favoured model sizes. In this case a second hand, little used EFlite foamy Corsair, fitted with one of those blue EC-5 connectors,  had the ESC well secured below a ply plate and, not wanting to be wielding the soldering iron over the airframe, I opted to make up a short adaptor. The lead length was already remarkably generous.

 

I'm really enjoying flying the Corsair recently, especially the landings. Anyway, I was just doing the usual beat up of the field and as the model passed I noted that the motor was stuttering and something was up. Two seconds later the motor stopped and furthermore I had no control. The model settled into a fairly tight, flattish circular flight path about 100m away and nothing that I could do with the sticks affected that. After three circles the Corsair disappeared behind the small rise at the edge of the field. I fully expected the model to be trashed, but on getting to the crash site the only damage was the very tip -last 20mm - of one elevator was broken off, with the small piece of foam sitting on the ground next to the model. Didn't even break the four bladed prop.

 

However there was no response to the radio. Nothing. Completely dead. Opening the battery hatch revealed a very hot connector, with the heat shrink shrunk right back, revealing bare metal and bright solder, and the plastic adaptor very floppy, The positive lead was completely disconnected. I can only conclude that there was a breakage in the adaptor, giving a high resistance joint which had heated up in flight and parted. The model was completely on her own, with no radio - ailerons were level, elevator was level, but the rudder was deflected 15 degrees, giving that tight circle.

 

Back on the bench the adaptor was consigned to the bin, the male connector replaced on the battery pack - which tested out fine, with no inbalance - and the EC5 on the ESC replaced with the proper connectors attached to the leads. My reluctance to wield the soldering iron over the model was cured using a tip I'd read somewhere, a sheet of cardboard to protect the model, with the leads passed through a hole. The connectors were secured with a wooden clothes peg to allow the quick soldering job to be completed.

 

Another lesson relearned, but won't be forgotten now. I do still have some adaptors, for the purpose of arranging packs in parallel in a few models, but I won't have adaptors for mismatched connector types in the model.

[Frank Skilbeck]

Had this happen on an EC connector on one of my models without an adaptor, but I share your pain with the myriad of different connectors. I also find the XT90's difficult to separate.

[RottenRow]

I had exactly the same issue as Frank. One half of an EC5 unsoldered itself in flight on a model that drew about 40A on full-throttle (so well within the connector’s rating). Luckily the ‘free-flight’ arrival caused minimal damage and the model is still flying today.

 

On inspection, it was one of the pairs in the EC5 that had overheated, and that pair (male and female, the male was on the ESC lead) was found to have zero friction when plugging and unplugging. Yet as a complete connector, with the outer blue housings, that had not been evident, as the housings offered the resistance as the connectors were plugged together.

 

The model had been well flown and being on the ESC lead, that same male pin was connected and disconnected for every flight, and the ‘springiness’ of the pin has gradually been lost, unbeknown to me.

 

I no longer use EC5s for this reason.

 

Brian.

[leccyflyer]

Thanks for that information guys.

 

As I mentioned, I greatly prefer the simplicity, low bulk and ease of use of the humble 4mm "gold" bullet connectors and must have several hundred in regular use. However, their Achille's heel is where the gauge of cables is too large to fit inside the cup. So, for my models using 6s1p packs I have reluctantly retained the EC5 connectors that their ESCs tend to be equipped with and therefore use batteries equipped with those connectors.

 

Your comment makes me reconsider that and I will need to seriously consider investigating 6mm gold bullets as an alternative. The possible mitigating factor is the frequency with which those larger models are flown, in comparison to the rest of the fleet. Most of them are still awaiting their maiden flights.

[RottenRow]

One thing that you could do Leccyflier is to have some spare EC5 pins (a male and a female, each soldered onto bits of wire for ease of handling) without the blue housing. Then just use these on occasions to test the tightness when they are mated, one at a time, with their opposite half. I hope that makes sense?

 

Then at least you will be aware if they start to become looser fitting.

 

Brian.

[leccyflyer]

That's a great idea Brian- will put that into operation immediately. 😎

[Outrunner]

Almost all of my connectors are XT60, easy to solder, almost impossible to short out, easy to connect and separate. I use 3.5 bullets on motor to esc and small models get JST or XT30.

 

I got rid of 4mm bullets years ago as being to easy to short out and even once stupidly connected a battery to itself, fortunately is was a nicad and got very hot and burnt my fingers separating the connector. I then switched to Dean's but when XT60 came along I switched.

 

I do have a couple of adapters I made for converting from JST to XT30 but very rarely used and so far no issues.

 

 

[leccyflyer]

I tried Deans, but really didn't get on with them at all. I find the XT60s unreasonably bulky and only have them on two packs for a specific model. The  4mm bullets work great for me. It's easy, with a bit of thought to prevent against the possibility of connecting a pack to itself and to protect against inadvertent shorts. They are also very easy to periodically check for any issues that might emerge - there were reports years ago of the male pins becoming loose over time, but I haven't found that to be an issue. The thought of changing over several hundred connectors is a bit of a nightmare and not something to be embarked upon lightly.

[robert chamberlain]

My sailplane has a narrow fuselage, and so I was planning on using two smaller batterys wired in  parallel with a "Y" cable. With this set up it would be possible for a good pack to cross feed to a bad pack. What is the number  of a diode that would be wise to use?-------"1N5401"?    Bob C

[Dale Bradly]

To possibly answer, need to know more: what are these batteries for? Motor or rx? And what is the size and construction of the batteries? (Lipo etc?)

[Nigel R]

RX? Best answer for me (sorry) would be, find a single battery that fits the space. Simplicity wins for me.

 

For a motor? Never a diode.

[Andy Stephenson]

The 1N5401 is only rated at 3Amps!

[Martin Harris - Moderator]

Diode choice will depend on the maximum current drawn by the servos but unless there’s a cell failure there will not be any meaningful cross feeding. Cell failure during a flight is extremely unlikely so diodes are not absolutely essential. Power will be drawn from the pack with the higher voltage so pack capacity is irrelevant. 
 

You do need to charge separately - never in parallel - and to be able to check each battery’s condition prior to flight.  Use separate charge/switch harnesses to achieve this.  Do not charge with “smart” chargers simultaneously if powered from the same supply - most, if not all, will interfere with each other’s peak detection circuitry due to the common “earth” connection. 

[Engine Doctor]

I think that the EC5 connectors are rubbish and always change out for an Xt type connectors . Ive had two EC5's fail buy letting one of the pins push out whole plugging them together. To have a pin or socket held in place by a thin circular barb that fails if it gets hot is IMO poor design.

It always pays to check the friction of a plug to socket as a loose or easy fit must be considered suspect , can get hot and fail.

As for adaptors , they are ok for testing etc on the bench but why use an adaptor continuously in a model . Any extra connections can be a failure point . 

 

[leccyflyer]

Aaarghh, I forsee much changing of those EC5 connectors, rereading this thread and given that comment. I'll have to look at those 6mm bullet connectors as an option.

[Dickw]

18 minutes ago, leccyflyer said:

Aaarghh, I forsee much changing of those EC5 connectors, rereading this thread and given that comment. I'll have to look at those 6mm bullet connectors as an option.

I use both 4mm or 6mm bullets depending on application. Up to about 60A applications I use 4mm, but above that I use the 6mm.

All my charger leads now terminate in 6mm bullets with a "6 to 4" adapter added. That way I can charge either 4mm or 6mm fitted batteries just by removing the adapter. Charging is a low current event, so the adapter is not a problem there.

 

Dick

[leccyflyer]

Thanks Dick - could you let me know what gauge wire do those 6mm adaptors take, as a maximum? I've found some on eBay and have asked the seller that question, but any leads (no pun intended) would be good to follow up on. I've decided that I must change all of those EC5s out and will be happier once that is done.

[Dickw]

I don't really think in terms of guages, I tend to think in terms of cross section e.g. I have use 6mm^2 cables in them.

Looking at the connectors I have, I can say the solder socket is ~5mm diameter which looks like it should take 6swg cables according to the charts I can find.

Have a look at the pictures on the 4Max site https://www.4-max.co.uk/connectors.htm  for pp-con60. The picture looks the same as the connectors I have. They seem good for 200amps or even 400 amps for brief bursts in my applications, despite being very compact.

 

Dick

 

 

[leccyflyer]

Thanks Dick, they look like they would be most suitable - I think the heftiest wires on my existing packs are 8AWG, so that should work. I'll be much happier with these than the EC5s.

[Andy48]

I had a plane lose all power on take off. Fortunately it had the grace to make a successful stop without damage. Turned out the connector on one side of the EC5 plug was pushed out of the housing. It made enough contact to run for the first few seconds but the vibration of the take off was enough to shake it loose. Binned the lot and now have the XT30/60/90 range.

[Mike T]

Just a few observations on connectors:

 

4mm bullets are fine electrically, but when connected, present you with an unyielding 'bar' about 3" long.  Wrangling two of these into a compact battery compartment can be a pain.  To get around this, I switched to 3.5mm bullets as a standard, because these were shorter, but there came a time where so many batteries had XT60 as standard that it became easier to adapt the ESC's rather than the batteries, so I've standardised on XT60s.  I still have a couple of 'jumpers' in the battery bag.  These are XT60s with 3.5 and 4mm bullets soldered directly to the contacts of the XT60, mechanically reinforced with a slug of brass tube in the solder buckets.  People were sniffy about my 3.5mm connectors until I pointed out that XT60s are in fact 3.5mm bullets in a fancy plastic moulding...

 

In any installation the connector that gets the most exercise and wear is the bullet/male connector on the ESC.  The batteries are rotated, but this connector gets used all the time.  I found it good practice to either replace the bullet or the entire connector periodically, to ensure continued good connection.

 

Re 6 and 8mm bullets - I considered these as they looked shorter than the 4mm, but obviously had better current handling and lower resistance.  Has anybody tried them and are they in fact shorter than 4mms?

[Dickw]

I am not sure where you get 3" for the length of a 4mm bullet connection, as mine seem much shorter.

My 6mm bullets are indeed shorter than the 4mm ones, and I have used them a lot in higher current applications.

Photo attached of 4mm and 6mm bullets both separated and together, plus a ruler confirming sizes/

 

Dick

[Geoff S]

 

11 minutes ago, Dickw said:

I am not sure where you get 3" for the length of a 4mm bullet connection, as mine seem much shorter.

My 6mm bullets are indeed shorter than the 4mm ones, and I have used them a lot in higher current applications.

Photo attached of 4mm and 6mm bullets both separated and together, plus a ruler confirming sizes/

 

Dick

 

 

I used to use 4mm bullet connectors but eventually opted for what appears to be the most common XT60s for most of my packs.  I recognise the top pair as very similar to my 4mm bullets (even if they are actually 6mm) but the bottom pair look nothing like any I've seen before and look very short.  My 4mm bullets are about 30mm long but if you add in the relatively inflexible shrink-on insulation/stress-relief parts then it's up to 45mm approx. 

 

Some installations suit bullets and others XT60 but, on the whole, the latter work well. 

 

I have various home-made adapters.  Some for converting connector types and some for reversing polarity which are mostly used either for charging or current/power measurement.  I haven't had any problems with any of them.

[Dickw]

7 minutes ago, Geoff S said:

........  I recognise the top pair as very similar to my 4mm bullets (even if they are actually 6mm) but the bottom pair look nothing like any I've seen before and look very short.  .....................

For clarity - the top pair are 4mm bullets.

The bottom pair are 6mm bullets that are fairly common amongst high current users and seem to be available from many sites including 4Max.

Those 6mm bullets were originally developed by Lehner Motoren Technik in Germany  and are sometimes referred to as LMT connectors.

 

Dick

ps. yes most batteries come with XT60 connectors, but I just cut them off and replace with my bullets.

Edited June 30, 2023 by Dickw

[leccyflyer]

4 hours ago, Mike T said:

Just a few observations on connectors:

 

4mm bullets are fine electrically, but when connected, present you with an unyielding 'bar' about 3" long.  Wrangling two of these into a compact battery compartment can be a pain.  To get around this, I switched to 3.5mm bullets as a standard, because these were shorter, but there came a time where so many batteries had XT60 as standard that it became easier to adapt the ESC's rather than the batteries, so I've standardised on XT60s.  I still have a couple of 'jumpers' in the battery bag.  These are XT60s with 3.5 and 4mm bullets soldered directly to the contacts of the XT60, mechanically reinforced with a slug of brass tube in the solder buckets.  People were sniffy about my 3.5mm connectors until I pointed out that XT60s are in fact 3.5mm bullets in a fancy plastic moulding...

 

In any installation the connector that gets the most exercise and wear is the bullet/male connector on the ESC.  The batteries are rotated, but this connector gets used all the time.  I found it good practice to either replace the bullet or the entire connector periodically, to ensure continued good connection.

 

Re 6 and 8mm bullets - I considered these as they looked shorter than the 4mm, but obviously had better current handling and lower resistance.  Has anybody tried them and are they in fact shorter than 4mms?

 

The dimensions of the 4mm connectors are such that they are not typically much larger in diameter than the battery leads on common packs. In terms of fitting them into narrow and confined spaces they have significantly smaller dimensions than the vast majority of housed connectors, which are often bullets of similar length but shrouded in a big chunk of plastic, as you've observed. They are also significantly more flexible in terms of creating series or parallel connections, which are easily made up with short wire lengths, or even connectors soldered back to back. Shorter 4mm connectors are available - in fact I sent two packs back just last week, as the supplier had sent those in error, instead of my standard 4mm connectors and they are incompatible, as they leave a section of the standard male pin outside of the shorter female socket, as you can see below.

.

 

I also queried the 6mm connectors as I'd expected them to just be scaled up versions of the 4mm bullets, but in fact they do look shorter, in comparison, but I'm prepared to live with that and have a bunch on order from 4-Max. One of my rainy day jobs this weekend will be to replace the EC5 connectors on all my 6s1p packs and ESCs for those models.