powerchute50

Is there a good (versus bad) way to solder or attach battery tabs to batteries? I notice that some of the commercial electronics with batteries (shavers and so on) seem to have the tabs spot welded on with very tiny electrodes. I would worry about the battery acting as too large a heat sink and requiring too much heat to get the solder to flow.

Is there such a thing as electrolytic glue? Could you mix a bit of aluminum powder with epoxy or something to get a conducting adhesive? How about liquid solder, the cold stuff?

Don

jooNorway

There is ONE way: Usa a good iron (100+ Watts and good tempreg), the right fluss (for nickled surfaces if neccessary) and the right solder!
Remember: a good solder is made within 2-4 seconds of heating.
Make a jigg to hold the batteries and heatsink them.
Clean the areas and tool during work!

Red Scholefield

My Feedback: (9)

Soldering directly to Ni-Cds/Ni-MH or any other cells is not a good idea. Try to use the welded tabs and solder to those if at all possible. Soldering to the positive button will have a very high probability of destroying the nylon seal. You just can't get the button hot enough to get a good solder joint without compromising the integrity of the nylon seal ring. This ring is under compression and raising its temperature will allow it to relax and the sealing properties are history.

If you can hold a penny between two fingers long enough to get a good solder joint with #18 stranded wire or braid, then go ahead and solder to your cells, otherwise get cells with solder tabs. Remember, nylon is a good insulator, electrical and thermal. There is no thermal path for the soldering heat to dissipate when heat is applied to the cover button of a cell.

Nylon characteristics:
Nylon has its glass transition at 460°F - 500°F . The maximum use temperature of nylon 6-6 parts is about 300°F. (Note that this is considerably below the glass transition temperature.)

Soldering temperatures are in the 450°F to 650°F range.

I realize this flies in the face of all the electric flight “experts” that assemble their own packs but it is never the less fact.

You have never seen a pack assembled by a cell manufacturer or any other pack manufacturer (outside of the hobby market) where connections are soldered directly to a cell. There is a reason.

Sanyo Cadnica Sealed Type Nickel-Cadmium Batteries Engineering Handbook
SF-9785ND
Section 10 General Remarks and Precautions
5 Safety Insturctions (page 48)
"Never solder lead wire directly to Cadnica battery terminals. Soldering
heat may damage the safety vent in the positive cap after a terminal plate
is spot-welded on the battery terminal, solder a lead wire on it."

Sanyo Twicell Sanyo Nickel-Metal Hydride Rechargeable Batteries
Engineering Handbook SF-9787ND Section 5 Important Cautions for Handling
Batteries 5-3-3 Do Not Misuse Batteries - "Never solder a lead wire or
plate directly to Twicell batteries. The heat generated by the soldering
may melt the insulation, damage the gas release vents or protective
devices, cause leakage of battery fluid, heat generation, bursting or
fire."

General Electric Nickel Cadmium Battery Application Manual [Library of
Congress Cat Card No 86-80684 Section 6.5.3 9 (page 6-20) "Never solder
directly to the nickel-cadmium cells, only to solder tabs or wire leads.
A hot soldering iron placed directly on the cell is likely to cause seal
ring and vent seal damage as well as damage to the separator systems."


First let me say that I am not on a crusade to stop the modeling world
from soldering directly to cells in construction of packs. All that I'm
trying to do is to alert modelers that there are some caveats they should
consider in making the decision to solder or not.

In the electric propulsion application and particularly on the competitive
side, the reduction of pack resistance plays a key role in obtaining
maximum performance. Direct soldering has been found as one means to
achieve this.

Soldering directly to cells that are destined for flight control operation
is not justified and can compromise the reliability of the packs. These
packs are frequently hidden away in the plane and are not frequently
available for inspection for any leakage and corrosion that may have
resulted from damage to seals/vents from direct soldering that can
compromise the reliability of the control system.

The risk (safety-wise) of soldering directly to cells is minimal but quite
dramatic on the rare occasion that it does surface. There are probably
more "incidents" resulting from abusive charge regimes than from actually
soldering. Of course the question always comes up was the soldering
contributory to the ultimate cell burst?

As far as warnings on the product as sold through hobby channels one has
to consider that no cell manufacture cells directly to the public. Sales
are through one or more levels of distribution, original equipment
manufacturer or pack assembler. It is the responsibility of the cell
manufacturer to inform the OEM or pack assembler of possible hazards in
assembly. This is done quite adequately in the engineering handbooks made
available by the cell manufacturer. If the OEM or pack assembler chooses
to ignore them, or passes cells on to the end user without informing him,
that becomes his responsibility.


Fortunately the hobby market is infinitesimal compared to the overall
market for batteries make risk exposure equally infinitesimal to the cell
manufacturer and further insulated by one or more layers of distribution.
This is not to say that the cell manufacturer cannot be held responsible.
In several cases I have been involved in as an expert witness (with TASA)
the cell manufacturer has been able to show due diligence in conveying
information to the OEM or pack assembler so that they were not held liable
for misapplication of the product by the end user. This "minimal risk
exposure" is probably the only reason why a major industrial manufacturer
(like Futaba/OS) even messes with the hobby - can you think of anything
more dangerous than a model engine with an exposed APC prop? I just tells
you how insignificant this hobby is in the overall scheme of product
liability.

One classic case, where the OEM did not make adequate provisions (due
diligence again) for preventing a battery from being inserted in a string
in reverse the resulting cell leakage (an alkaline primary cell in this
case) and caustic burns to the child did not result in the cell
manufacture having to pay - it was the OEM that took the hit.

Bottom line: Soldering directly to cells is not recommended. Do it
understanding the risks and possible trade offs to performance, safety and
reliability.

Peter Khor

My Feedback: (4)

Any idea if any cell mfg have switched from nylon to some other high-temp equivalent in recent years?

Red Scholefield

My Feedback: (9)

General Electric used Polysuphone on batteries for high temperature operations (refered to as Gold Top) . I don't know if any others are using it at this time. It does not make as good a seal as the nylon and has some other problems, making it a bit more difficult to work with.