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Author Topic: Solder Grade?  (Read 2435 times)

bj

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Solder Grade?
« on: July 19, 2015, 09:55:27 PM »

Having upped the battery size in a fast electric boat from a 2s 5200mAh Lipo to a 6200mAh I found that the soldered banana joints have un-soldered themselves while running .......
What grade of solder do you use for this purpose?
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JimG

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Re: Solder Grade?
« Reply #1 on: July 19, 2015, 10:19:22 PM »

I use normal tin/lead flux cored solder for all electrical connectors without any desoldering in use. Are the connectors suitable for the current you are using? If the connectors are getting hot enough to melt the solder then they must be a higher resistance than wanted. Check the soldered joints are good as a poor joint will give a high resistance.
I use XT60 connectors for almost all battery connectors and these are good up to at least 50 - 60A.

Jim
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inertia

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Re: Solder Grade?
« Reply #2 on: July 20, 2015, 09:03:36 AM »

You'll find that a lead-free solder which contains a tiny amount of silver has a much higher melting point than good old 60/40.
DM
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malcolmfrary

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Re: Solder Grade?
« Reply #3 on: July 20, 2015, 09:17:01 AM »

You'll find that a lead-free solder which contains a tiny amount of silver has a much higher melting point than good old 60/40.
DM
Very true, and the soldered join will be more reluctant to melt in service, but the connector should not be getting hot enough in the first place to melt whatever type of solder was used.  Higher melting point solder might just move the problem along and overheat something expensive.
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derekwarner

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bj

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Re: Solder Grade?
« Reply #5 on: July 20, 2015, 04:17:11 PM »

Interesting that it is ONLY between the ESC and the motor where the solder plugs have melted. It is the same ESC, same motor on BOTH boats (one surface drive and the other submerged).
 The output side of the ESC and the motor are 14AWG wires and the input side from the battery are 12 AWG wires.
Can only be down to the higher C discharge rating of the bigger battery
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inertia

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Re: Solder Grade?
« Reply #6 on: July 20, 2015, 04:41:20 PM »

Very true, and the soldered join will be more reluctant to melt in service, but the connector should not be getting hot enough in the first place to melt whatever type of solder was used.  Higher melting point solder might just move the problem along and overheat something expensive.
Point well made, Doc, but with not knowing anything much about the ritual abuse of motors and batteries which is called "fast electrics" I wondered if these high-temperatures were considered 'normal'.
BJ mentioned two boats in his latest post - perhaps the submerged drive is taking more current than the surface one? It's a fact that the performance of some motors is restricted by the ability of the battery pack to deliver the level of current which they can handle, so increasing that factor could certainly have increased the current and therefore the temperature. My advice would be to increase the thickness of all the wiring and keep all lengths of cable as short as possible.
This table might be of use:
 AWG                Conductor dia (mm)               Max current (Amps)
10                                2.59                                         55
12                                2.05                                         41
14                                1.63                                         32

Dave M

 
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bj

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Re: Solder Grade?
« Reply #7 on: July 20, 2015, 06:15:35 PM »

My advice would be to increase the thickness of all the wiring and keep all lengths of cable as short as possible.
This table might be of use:
 AWG                Conductor dia (mm)               Max current (Amps)
10                                2.59                                         55
12                                2.05                                         41
14                                1.63                                         32

Dave M


14G is the size that both of the brushless motors are prewired. The ESC's are also prewired 14G (3.5mm bullets) - otherwise I would have done that. Seems strange to me though that the batteries are wired as 12G and the ESC's are 12G in and 14G out
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inertia

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Re: Solder Grade?
« Reply #8 on: July 20, 2015, 06:59:41 PM »

Search me, BJ. If you find out the answer please post it up on this thread. Meanwhile there's nowt else I can offer you, m'duck.
Dave M
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malcolmfrary

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Re: Solder Grade?
« Reply #9 on: July 20, 2015, 08:23:22 PM »

Interesting that it is ONLY between the ESC and the motor where the solder plugs have melted. It is the same ESC, same motor on BOTH boats (one surface drive and the other submerged).
 The output side of the ESC and the motor are 14AWG wires and the input side from the battery are 12 AWG wires.
Can only be down to the higher C discharge rating of the bigger battery
Not quite.  In a situation with a nice newly made connection, I would suspect the new kid on the block, the connection, as being the guilty party for generating the unwanted temperature in the place where the solder melted. 
If a very neat connection between bullet and wire end was achieved, there might be a lot of bullet shell conducting and heating up before the current transfers to the sleeve.  When terminating cable into a bullet, I preferred a nice blob of solder in the nose, if only to make sure that the wire would stay connected.  Then there is the surface to surface connection between bullet and sleeve.  Any lack of either area or tension between the two will generate local heat.
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