Topic: Help Reversing Polarity

[ford prefect]

Beginner with power stuff as many of us are, so bear with me.   

I just picked up this battery pack for my R4:

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=1972

If you look at the picture, the battery cable has an adaptaplug end on it.  (Picture below is zoomed in showing this).  I'm a UA-5 owner and made my own hot-swappable battery cable using Radio-Shack's parts, so I am familiar with reversing polarity by just reversing the tip on the cable.  Easy Shmeezy.  Unfortunately, the adaptaplugs that come with this battery kit are designed to prevent reversing polarity - the prongs on the adaptaplugs are 2 different sizes.   

What I'm wondering is - how risky/difficult is it for me to cut the end off the battery cable and reverse polarity by swapping the internal cables and reconnecting them?  I know that I have to be careful not to let the cables touch while I do this - what else do I need to look out for?  Is this something I can tackle?

Any advice is much appreciated.

-Brad

[JasonSobel]

What I'm wondering is - how risky/difficult is it for me to cut the end off the battery cable and reverse polarity by swapping the internal cables and reconnecting them?  I know that I have to be careful not to let the cables touch while I do this - what else do I need to look out for?  Is this something I can tackle?

Any advice is much appreciated.

-Brad

Brad -
it's real easy to just hack the connector that is on the battery, reverse the wires, and solder the connections.  You are correct that you should be careful not to touch the two leads from the battery, as that will create a short and the juice will flow and it'll be bad.  but, on the other hand, even if they do touch briefly, it might spark a bit, but nothing catastrophic or anything.  so go for it.
- Jason

[Brian Skalinder]

It's easy.  And no soldering required if that makes you nervous.  My reply from the R-4 run-time thread in which you posted before starting this thread:

I just cut the wires, swapped (+) and (-) on the UA5/R-4 connector side, and spliced them back together with wire nuts (see pic, no soldering).  I folded the cable back on itself and secured it with tape on either side of the wire nuts to provide strain relief while the cable's in my bag.  No problems so far, been about 2 years, I guess.  And if I have a problem with the cable in the field, it's field-fixable with no tools: remove tape, re-fasten wire nuts, add new tape.

Pick up an inexpensive multimeter so you may check for proper polarity before hooking up your gear.

[ford prefect]

Cool, glad to read that there's nothing else I need to worry about while doing this.  After the battery has been reversed, will I also need to reverse the polarity on the charger?

Thanks Jason and Brian, +T

[Brian Skalinder]

After the battery has been reversed, will I also need to reverse the polarity on the charger?

My batt came with a separate charging cable and on-board connector, independent of the output connector, so I didn't need to re-wire anything on the charger side.  Looks like in this case there's a single cable connected to the battery for both charging and output.  So, yes, you would want to reverse the polarity on the charger, too.

Just remember to use the multimeter to confirm everything so you don't fry it.  Check the output's polarity with the multimeter, and ensure it matches the charger's polarity.

[ford prefect]

Thought so.  Thanks again Brian,

-Brad

[ford prefect]

Did the rewiring this morning, checked the voltage on the cable before and after and it remained constant at just below 10V.  Was really much easier than I thought it would be - took me no more than an hour to do 2 batteries and the charger, and only once did I accidently brush the cables together producing a small acidic smell from the rubber shielding, but the battery still seems to have a charge so I think it's ok.  I swapped the cables, twisted them together, added some solder, slid some heat shrink over them, shrunk it with a heat gun (borrowed from the old man), and then added some electrical tape on top of the heat shrink to give a little more insulation.

Thanks again Brian and Jason, looking forward to next weekend at Camp Bisco.