RCA 10.5 Connector for Battery Charger

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RCA 10.5 Connector for Battery Charger

Post by jkaness » Feb 12, 2018 12:51 pm

Has anyone found a source for the concentric connector, some call it an "RCA 10.5" that is similar to the audio RCA connector but with the outer shell of equal length to the center pin? My new 48-volt 20AH battery and 2A charger use this and they work fine. I have another charger with the Amphenol 3-pin connector and would like to change that connector, or make an adapter, but cannot find a source for the concentric male connector. My son's ebike was damaged in a fire and I rebuilt it- he's riding it again. Details posted at http://www.jimkaness.com/engineering/2018ebike.pdf .
RCA 10.5 Charger Connector.JPG
RCA 10.5 Charger Connector.JPG (15.19 KiB) Viewed 173 times
Last edited by jkaness on Feb 13, 2018 9:56 pm, edited 1 time in total.

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Re: RCA 10.5 Connector for Battery Charger

Post by rhizomatic » Feb 12, 2018 3:59 pm

My charger, using this connector, just died and I have had a hell of a time sourcing one online. Worse, my 36v 12s lithium battery pack needs 43.5 volts and not the common 42 volts for a 10s lithium (if I understand the system correctly). Adapters I found for purchase online are of the audio RCA type. Stuck without my bike for most of a week now, I found wiring diagrams for adapting an XLR type connector to the audio-style RCA connector. I have ordered a charger that will deliver 43.5v and has the XLR. I am going to use my existing (dead) charger's connector for a DIY adapter. Wish me luck!

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Re: RCA 10.5 Connector for Battery Charger

Post by jkaness » Feb 12, 2018 4:38 pm

I am NOT a Lithium battery expert- I just buy them and use them! As I understand it there are several different lithium battery chemistries and they are "close but not the same" with regard to voltage. The only safe comment I can make is to use the charger that came with the battery. Many of these items come from China and the literature and specifications are hard to find. On two occasions I have emailed the manufacturer in China and received useful replies.

A useful article on lithium and other battery voltages is at http://batteryuniversity.com/learn/arti ... h_voltages .

I found and ordered an XLR to RCA adapter cable today at https://www.mycablemart.com/store/cart. ... ail&p=6380
When this adapter arrives I will need to verify the polarity of the voltage at the RCA end to be compatible with my battery (center pin positive). While I am capable of making up an adapter, I cannot buy the parts for the price of this adapter! If necessary I should be able to rewire the XLR to get what I need.

Good luck!

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Re: RCA 10.5 Connector for Battery Charger

Post by rhizomatic » Feb 12, 2018 8:49 pm

Thanks for the tip! I just followed your lead and ordered the adapter. Much cheaper than ebikes.ca (a site that I love). So cheap, I just could not resist. I also might still do the rewire thing... here is one of the simple diagram sites I found. Easy stuff:
http://www.mediacollege.com/audio/conne ... rca-1.html

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Re: RCA 10.5 Connector for Battery Charger

Post by jkaness » Feb 13, 2018 9:17 am

Just one caution. I have in hand an ebike charger with an XLR connector. My charger (56.4 volts @ 2 amps) has the POSITIVE output on pin-1 and the NEGATIVE output on pin-2, measured by my voltmeter. Pin-3 is not used. This would be the REVERSE of what your diagram shows for audio use. Just make sure your RCA plug offers the correct polarity before connecting it to your battery! My battery wants the center pin to be POSITIVE. Please make sure what YOUR battery wants the center pin to be. You and I might have to rewire the XLR connector on the adapter cable we ordered, This is still cheaper and easier than buying separate parts!

Standards are great. But in this case we are using connectors, designed years ago for audio use, for battery charging.

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Re: RCA 10.5 Connector for Battery Charger

Post by fechter » Feb 13, 2018 9:42 am

Just curious:
Was the fire caused by the bike?
"One test is worth a thousand opinions"

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Re: RCA 10.5 Connector for Battery Charger

Post by eCue » Feb 13, 2018 9:49 am

I needed to charge hoverboard batteries with a charger so bought this connector

It can be found on eBay with this search term

Connector Adapter Plug Converter DC 5.5 x 2.5mm Female to XT60 male

You can find other connector versions under DC 5.5 x 2.5mm male (or female)

Image

:)
Solar charge station on wheels = distance not limited by the wall sockets :D

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Re: RCA 10.5 Connector for Battery Charger

Post by jkaness » Feb 13, 2018 10:02 am

Re: the fire. The battery (48 volts, 16 AH) was inside the trailer being charged when the fire broke out. The bike was outside leaning up against the trailer. No one saw what started the fire. My own best guess is that the battery started the fire but we will never know for sure. The AC wiring in that old trailer had been messed with over the years. The person who custom made our bike, and who custom made the original battery from individual cells, admitted to me that he had had other fires in some of his batteries and has now changed his approach to making batteries. That original battery had been in heavy use for some 18 months before the fire and we were comfortable with using it.

For what it's worth, the original battery used an XLR connector for charging. The charger I have in hand now was a spare for that. The original charger burned up in the fire.

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Re: RCA 10.5 Connector for Battery Charger

Post by jkaness » Feb 15, 2018 12:19 pm

Here is a drawing of the XLR to RCA audio cable (1) as purchased, and (2) as modified to provide positive polarity to the RCA center pin. The audio RCA male plug fits well (goes fully into the socket) into the battery's charger port and now the previous spare charger is available for use with the new battery. Tested and verified.

If desired, the RCA plug center pin could be cut off to be shorter, but it is not necessary here. Thus the need to purchase an "RCA 10.5" connector that started this thread is overtaken by events. :D
XLR RCA Adapter.png
XLR RCA Adapter.png (29.85 KiB) Viewed 128 times

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Re: RCA 10.5 Connector for Battery Charger

Post by rhizomatic » Feb 21, 2018 3:16 pm

Stupidly, I rushed in an burned the connector cable up. THEN, I discovered the problem you cite about positive/negative. No really bad damage. The ends of the adapter are fine, as is the charger and the battery, as far as can be told by voltage readings. I had suspected I should check, and then I rushed in anyway. Very dumb move on my part. Fortunately, it all looks like it can be rewired alright. Time to get some new wire and pull out the soldering iron! I figure I need 18awg wire for 4amps and 36 volts
IMG_20180221_120336-1.jpg
IMG_20180221_120336-1.jpg (47.31 KiB) Viewed 107 times
In the photo you can see the blue wire. It is positive. But positive meets negative on the charger! Booo.

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Re: RCA 10.5 Connector for Battery Charger

Post by jkaness » Feb 21, 2018 3:40 pm

Yes, 18 gauge will be more than adequate for this use. The shielded blue wire that came as part of the adapter should work as well if not "over-amped". Even common AC zip-cord should work here but the wires are usually the same color making it hard to remember which wire is positive etc. In my 60+ years of wiring things I have done what you did---and worse!

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Re: RCA 10.5 Connector for Battery Charger

Post by rhizomatic » Feb 21, 2018 9:27 pm

I notice in your wire scheme you don't cross the 2 & 3 positions (negative and ground). You left position three unconnected? Is that safer?

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Re: RCA 10.5 Connector for Battery Charger

Post by rhizomatic » Feb 21, 2018 10:34 pm

Done. And charging. Did it exactly as you diagrammed. But I am watching it closely, irrationaly fearing fire. This 4amp charger really charges fast! My old "High Power" unit was 1amp.

Noob pleasures. I have nearly 4500 miles on this 12s lithium battery. Still no voltage drop to speak of (was originally 41.8 and now stand "full" at 41.7) ... Wanna keep it.

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Re: RCA 10.5 Connector for Battery Charger

Post by jkaness » Feb 22, 2018 8:45 am

1. Glad it is working right for you. Well Done!
2. Four amps will charge much faster than one amp (my own is 2 amps). The only issue is the size of the cells and how they react to that charge current. I am not the expert for that subject. Recommend following what the manufacturer of your cells says about that.
3. For AUDiO applications it is desirable for the metal shell of the XLR connector to be connected to the system ground to keep hum and noise out of the audio. For battery charging applications I consider it optional if the metal shell (pin-3) is connected to anything.
4. A personal comment: why this industry decided to use AUDIO connectors (XLR or RCA) for battery charging is a mystery to me. Of course, any 2-wire connector that can handle the voltage and current can be used.

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Re: RCA 10.5 Connector for Battery Charger

Post by amberwolf » Feb 22, 2018 2:27 pm

jkaness wrote:
Feb 22, 2018 8:45 am
2. Four amps will charge much faster than one amp (my own is 2 amps). The only issue is the size of the cells and how they react to that charge current. I am not the expert for that subject. Recommend following what the manufacturer of your cells says about that.
Yes. Sometimes they use a low-current charger because they're cheap and small, and sometimes it's because the cells can't handle teh higher current well. (on some cells, it can cause fire if the charge current exceeds max spec by far enough).

3. For AUDiO applications it is desirable for the metal shell of the XLR connector to be connected to the system ground to keep hum and noise out of the audio. For battery charging applications I consider it optional if the metal shell (pin-3) is connected to anything.
It's actually safer to not connnect the shell in chargers, because you then cant' short the shell to the opposite polarity pin inside it by accidentally pushing the end agianst a metal object. ;)

4. A personal comment: why this industry decided to use AUDIO connectors (XLR or RCA) for battery charging is a mystery to me. Of course, any 2-wire connector that can handle the voltage and current can be used.
Audio connectors are generally widely available, and often cheap because of that, and while not cheap like RCAs, XLRs are still common.

XLRs are large and easy to handlej, so they make good user-interface and are cheaper than connectors of similar handling ability that were intended as power-handling / charging connectors. (or at least, were when all this stuff started being used that way back then).

XLRs also have 3 pins, so you can have +, -, and a thermistor pin, which was important in the NiMH/NiCd days when these were more commonly used for charging. Or it could be used as a pack-ID pin so the charger wouldn't charge if it didn't detect the right resistnace on it, or the right zener diode voltage drop, etc.

Also, 3 pins plus a shell can actually be used as a four pin connector, or a higher-current 2-pin, by paralleling two of the pins and one pin plus the shell. Might also have been a factor in some designs' choices.

It oculd also have simply been the experience of the "engineer" that chose that part, having used them for other things before. ;)

Or the company taht made some large batch of chargers (or bikes, or both) already had a warehouse full of those connectors, and said "use these or you're fired". ;)

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Re: RCA 10.5 Connector for Battery Charger

Post by jkaness » Feb 22, 2018 6:39 pm

Amberwolf made some good comments. I have experienced all of them over the years. Many "technical" decisions are made on the basis of cost, prejudice/personal favorites, and other non-technical reasons.

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Re: RCA 10.5 Connector for Battery Charger

Post by rhizomatic » Feb 22, 2018 7:16 pm

Ugh. The first time I charged it went to 41.8 volts. The second time 41.4. And right now it sits at 41.2. 4amps is killing the battery, isn't it? For two and a half years it has always cut off at 41.7 or 41.8 volts.

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Re: RCA 10.5 Connector for Battery Charger

Post by jkaness » Feb 23, 2018 8:44 am

Rhizomatic: Again I claim no battery expertise, but all rechargeable batteries have some finite number of recharges before the chemistry inside gets all messed up and they no longer work like they used to. They do not last forever no matter how well you treat them.

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