Electrical issue

[Rygar]

Checked on the fifth wheel in storage today. Batteries were dead. They are 5 years old so I knew I was on borrowed time with them anyway. Towed to my local battery store. Have two 6 volt batteries that tested at about 2 volts max. Had them replaced. Mechanic tells me after he installs them that something must be turned on because he got quite a spark putting in the new batteries. I checked all through the rv and everything was turned off. Anyone have any idea what could cause this? Could there be an electrical draw somewhere and how on earth could I find it?

[Rygar]

Thanks, I flopped the battery disconnect switch. Then I noticed Fiver was not quite level so hit the retract switch and it still worked. Maybe my battery disconnect switch didn't disconnect the battery. I'll just disconnect the black cables and be done with it.

[AllegroD]

In some rigs, flopping the 12v off switch may not disconnect all parasitic draws. I would disconnect the neg. from battery.

[Dave_H_M]

That is normal for me also.

But i ain't no technician. :h

[westend]

The mechanic may have connected a discharged battery to a fully charged one. In that instance, current will flow.

[Rygar]

Thanks guys for all your help. This time I did activate the battery disconnect. Hope I'm good now. Next time I go to the storage building, I'll try the spark test and see if I get more than one spark.

[RLS7201]

Chris Bryant wrote:
The way I do it is to brush the negative post with the cable- get a spark- immediately do it again. If it's a load, you will get sparks both time- a capacitor charging, you only get a spark the first time.

Why didn't I think of that? Thanks.

Richard

[Chris_Bryant]

The way I do it is to brush the negative post with the cable- get a spark- immediately do it again. If it's a load, you will get sparks both time- a capacitor charging, you only get a spark the first time.

[wa8yxm]

There is nearly ALWAYS "quite a spark" when installing batteries in an RV that is not connected to shore power, and sometimes even if it is..

Now, you need to ask why?

Well, first.. yes, there are things like the Explosive Gas (Propane) detector that may well never turn off, EVEN if you use the "Disconnect" in other cases they do.. But still

There is a device called a Converter (or the charger module of an Inverter) NOW. the older (last century older) Megneteks would not do this unless you installed a "Battery Simulator" but modern ones have a component called a "Filter capacitor" These devices are designed to store electricity.. for 1/60th of a second (or less) so that you get nice lean DC out instead of raw unfiltered reified A/C.

Side story: RVer told of installing a 12 volt (Dash type) radio in his RV and getting a horrible BUZZ when on shore power... He had an older (Last century) converter with no filters.. his new converter is filtered and works great.

The Spark your man saw was the cap re-charging Very normal and very short termed

IF you were to take a small (Say one ohm)_ resistor and an ammeter (15 amps peak,,, You could get by likely with 10 amps but may pin it) and put 'em in series liek this

Battery--Resistor--Meter--RV

You would see the meter initially PIN, at the max or at near 12.6 Amps, then slowly drop down.. Now you can put a mark on the meter fact (If you really need to knwo I can work out where) and time the amount of time it takes to fall to the mark.. and that.. And from that determine the size of the filter cap.. Believe it or not (have done it.... Used to have a calibrated meter)

But you have no need to do this.

[SoundGuy]

Rygar wrote:
Checked on the fifth wheel in storage today. Batteries were dead.

Your post reads like you don't disconnect your batteries whenever you're not using the rig ... if so, of course your batteries will be dead. And "dead" isn't 2 volts as you normally don't want to draw down any deep cycle battery more than ~ 50% which for a 6 volt battery is ~ 6 volts.



Now that you have new batteries either disconnect them physically when not in use or better still install a battery disconnect switch so parasitic draw in your rig doesn't kill these ones as well.

[JimInMich]

Don't forget the propane/carbon monoxide detectors ( the type that are hard wired ). Not a big draw, but a draw people dont think about. Also 3 way frig ( if you have one ).

[MrWizard]

most likely just the filter caps in the converter

UNless the emg break-a-way for the tt brakes is on check the pull pin for the break-a-way switch

[Cydog15]

Did he have it plugged into AC when he changed the batteries? Converter or inverter/charger would certainly do that.