converter evolution

[david craft]

i saw some earlier chats on converters styles ...thought i throw in some history. the earlier rvs had convection style heaters and no 12 volts appliances , just 12 volt lighting and 110 volt lighting. the next stage added forced air furnaces with a transformer and diodes to run a 12 volt motor but no provision to supply that power to the rest of the coach. then the first converters came on the scene. they would run the lights and furnace but you had to switch between the converter or the battery for the power source to the load. then they came out with a converter that had a relay to switch the load for you but still no provision to charge the battery. then a fully a fully automatic converter came next but it only had a 10 amp circuit for charging. thats the story for the "linear style" converter. there is the "ferro resonant" converter that came along in the 70s i believe...famous for noise, heat, but convenient for only having 2 wires to hook up. the latest generation is the "switch mode" ...quiet, efficient, high output for charging and loads, no ac ripple. they actually boost battery life. to see if your converter charges your battery, just plug in the coach and hook your volt meter to the posts. anything over 12.8 volts dc is charging current. fully automatic chargers started in about 1975. ive seen the ferro resonant in earlier travco and airstream models. hope you enjoyed the read.

[Lakota Wolf]

Very informative on the checking charging system, a.k.a. inverter/converter.

[Jim Stoltz]

Turns out it was filthy terminals. Battery is fine. Oops. Thanks for all the suggestions!

[Jim Stoltz]

So my "smart" battery charger is now saying "F03" when I try to charge the battery "Bad Cell or Open Circuit." Thinking the battery is no good, but I'm still charging through the battery posts. I'll check that first.

[david craft]

Wierd thing about bad battery connections...a heavy draw like cranking an engine burn a cood contact on the posts. Then a light current flow to recharge just doesnt make it. And the battery just marches down in charge accordingly. Another parasitic drain is the humidity swith on some norcolds. They pick up power before the on/off switch and power a heat strip between the freezer and the fridge. God bless the webmaster Gods...my sentences autocapitalize at the beginning now...so much for academia...sounds like a battery...lol

[Jim Stoltz]

Oh yeah - forgot to mention that my fridge doesn't have a DC option. Just gas and 120V. The 12V power supply is connected to the house batteries.

And...my step is vacuum actuated. BUT it does have a constant-hot door switch so it can decide whether to retract or extend the step. It's presumably attached to a vacuum solenoid under there. I'll check that for a draw.

I also haven't checked the connections at the battery terminals, but they *should* be okay. 

[John "T" Nordhoff]

  Yo David Craft,

  Good suggestions on the possibility of a faulty 3 way (Gas, 12 VDC, 120 VAC) Fridge as a possible high current draw on the engine battery. I never liked those because they were indeed a high current draw at 12 VDC and fed off the engine battery as the alternator charges it while driving.

 My electric steps are also (as typical) powered off the engine battery and regardless if the lock out switch by the door is on or off, if you start the engine the steps retract as a safety feature. I like that system.

  Of course, a trip to an auto store or Wal Mart etc for a free voltage and hydrometer and load test will show his battery condition

 John T

[Jim Stoltz]

Thanks for the suggestions. I really think it's just a bad battery. It's not holding a charge at all - when the charger thinks it's done the engine will barely turn over. BUT, with the charger in "jump start" mode it fires right up. It was fine all season until about a month ago but then the engine started cranking over slowly. I can't listen to the radio (just a small wattage, in-dash unit) for more than 15 minutes without killing it. I haven't changed anything that would suddenly cause a draw (but I'll check for one anyway). The chassis battery is completely isolated from the house batteries - all it needs to do is start the truck. It does have the isolation relay John spoke of. It's mounted above the radiator but it hadn't occurred to me that I can wire up a switch to it in order to connect the house batteries to the chassis in an emergency.

It's a Wal*Mart battery that got horrible reviews. It was cheap, but I guess you get what you pay for. It has a good warranty though.

[david craft]

Does the 84 have an dometic AES refrigerater in it? If so the 30 amp dc relay for the heat element is notorious for welding shut causing the element to just suck the battery down. They draw so much current that voltage to the refer is often low causing this condition. 3 way refers are pretty much passe due to this. I personally would just cut the power to this relay. Just operate on gas when traveling. Electric steps can be a parasitic drain as well. I take a battery lead loose and just touch it to the battery to see if a spark is present indicating a drain. I touch it a couple times because a capacitor in the system will cause a spark the first time as it charges. Disconnect the refer first and spark test...then try the step disconnect to see if its the source of the drain. Both of these loads are traditionally hooked up to the chassis battery for reasons I wont bother you with.

[david craft]

I was thinking...one of those knife switches that mount to the post of the battery could be used to just tie the chassis and coach batteries together. Then there is no solenoid constantly energized for what could be days or weeks on end. Just disconnect the switch when you disconnect shore power...

[John "T" Nordhoff]

  Yo Jim Stolz, you mentioned the RV Converter/Charger not also charging your truck battery.

 

 Such is the normal configuration. There is usually a mechanical/electrical Isolation relay (or a solid state device) that is normally open, but closes when the truck is running so the alternator can also charge the RV house battery. HOWEVER it doesn't usually close when your RV Converter/Charger is operating in order to also charge the truck engine battery. Its ONLY activated by the truck engine operation.

 HOWEVER that's a fairly easy function to wire up since that relay is 12 VDC operated. Some RV's even have an emergency switch that pulls that relay closed in case the engine battery is dead thus allowing the RV house to jump the truck battery so it starts.

 All you would need is to use a switch to close that relay if you want the RV Converter/Charger to also be connected up to the truck engine battery. HOWEVER I'm NOT recommending that. Sure it will work, but Id look into the truck battery or wiring problem versus having your RV Converter/Charger being coupled up to a problem or too much of a current load!!!

 NOTE those isolation relays may look like a normal Ford type of 12 volt starting solenoid BUT THEY ARE NOT as they (unlike Ford start solenoid) are 100 % duty cycle rated.

 John T