General > General Technical Chat
Adding reverse polarity protection help
EPAIII:
A further alternate arrangement for my idea above would be to have both of the original connectors separate as they are now, but with a piece of insulation material (PC board scrap) epoxied to them, sticking out the forward end, so they can not be plugged into the charger. Then a third connector would be added with the steering diode for charging. It would be the only one that physically could connect to the charger.
This means no changes to the charger and all the mods are made to the batteries. Any charger with the same connector could be used. It's the batteries that are made fool proof. And a completely dead battery connected backwards would get no charging current through the diode. Your improved version of the fool is going to have to be a lot better fool to get around that.
A small cable tie wrapped around the connector and insulator finger combination while the epoxy is still curing would make that sandwich a lot stronger.
CatalinaWOW:
There is no need to overcomplicate the connector situation.
Current always flows out of the battery to the load in use. Designate that lead as the red lead, and if you are thinking in terms of conventional current, current is flowing out of the positive terminal.
Current always flows into the battery during charging through the same lead that supplies current to the load in use. That lead has been designated red.
Now matching colors the load wire receiving current is red, and the supply wire charging the battery is also red.
All these conditions are met with a simple two terminal polarized connector. Most RC plane batteries I have encountered come either with a polarized connector on the load wires, or bare wires to allow user installation of appropriate connector. The second connector seen on many (but not all) RC batteries has low current connections to each internal cell for use in balancing the charge on the cells. The wiring on this connector cannot support normal charging current.
The only connectors that do not force correct orientation I have encountered in RC planes are the "Anderson Power Pole" connectors (which are polarized, but whose geometry allows a chain of connectors to result in crossed polarities) and those who do not use a unitized connector and use bullet connectors for everything. Those who choose to use the latter two connection styles must recognize that their choices require a high degree of care. The OP having had two failures should not choose to use either of these styles.
Even with a polarized connector on the battery, charger and load there are opportunities for mistakes. Many modelers wire their own connectors and can make mistakes. I have seen planes and batteries for sale that use the same style of connector but with different conventions. Many chargers use color coded banana pins to connect the charging cable, and these depend on the operator to follow the color code.
Most of these failure opportunities can be avoided with a one time careful inspection (and perhaps testing with a simple idiot light polarity detector) at time of purchase or manufacture, so the most dangerous of these failure modes is the banana connection to the charger. For those prone to careless mistakes it may be worthwhile to make this idiot resistant by gluing the charging cable in place, adding a mechanical interlock to prevent reverse connections (could be implemented with 3D printed parts glued to the charger and charging cables), or replacing the output banana jacks with a polarized connector.
EPAIII:
And yet the OP has apparently seen some situations where things were connected incorrectly. Perhaps some with dangerous consequences. Just because someone flies a RC aircraft does not mean they understand electricity and the possible dangerous consequences of the misuse of lithium batteries.
Some situations do call for measures that are as fool proof as possible.
CatalinaWOW:
--- Quote from: EPAIII on December 19, 2023, 06:28:45 am ---And yet the OP has apparently seen some situations where things were connected incorrectly. Perhaps some with dangerous consequences. Just because someone flies a RC aircraft does not mean they understand electricity and the possible dangerous consequences of the misuse of lithium batteries.
Some situations do call for measures that are as fool proof as possible.
--- End quote ---
Yes, all idiot proofing fails in the presence of a superior idiot. He apparently did not use polarized connectors, or did not verify that his polarized connections were wired properly
Similar omissions would cause the failure of any potential failure correction circuitry.
EPAIII:
I thought this thread was about how to ADD PROTECTION, not about the need or value of that protection vs. the potential stupidity of some users. I attempted to address the OP's question. Not start a debate on a different subject.
I believe I posted one possible way to do what the OP asked for.
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