Author Topic: Charging deep cycle batteries  (Read 2735 times)

Offline raslenny

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  • Posts: 1
  • Member since: 2006
  • I own: a Motor Home
  • Year: 1969
  • Make: Winnebago
  • Model: D24
  • Chassis: Dodge
  • Engine: 318
Charging deep cycle batteries
« on: October 15, 2009, 05:01 AM »
Sent: 3/6/2006

Whats the proper way to charge deep cycle batteries with a charger? and what kind of charger do you use? it seems that the converter or the shoreline won't bring them up to full charge ,or I haven't left it plugged in long long does the shoreline take to recharge them? there's 3 batteries in the rig

Offline OldEdBrady

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  • Posts: 525
  • Doin' Nothin'
  • I own: a travel trailer
  • Year: 1976
  • Make: Alfa
  • Model: Class C 03
  • Chassis: 10 ton frame
Re: Charging deep cycle batteries
« Reply #1 on: October 15, 2009, 05:02 AM »
Sent: 3/7/2006

I use a Century charger that is made for RV, Marine, and other deep cycle batteries.  (I've had it so long, I have no idea what it cost me.)
For the main battery, I've wired in a small solar panel with a cutoff switch.  When the motor is off, I flip that switch on to keep the main up.
As to how long it takes to charge a deep cycle, the answer is:  It depends.
How far is it discharged?  What method are you using to charge it (charger, shore power, etc.)?
I had a coach battery that simply wouldn't take a full charge.  No doubt in my mind it was rapidly dying.  I got a new one for just under $100.

Offline DanD2Soon

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  • Posts: 83
  • I own: a Motor Home
  • Year: 1972
  • Make: Explorer
  • Model: 24 ft M300
  • Chassis: Dodge
  • Engine: 413
Re: Charging deep cycle batteries
« Reply #2 on: October 15, 2009, 05:03 AM »
Sent: 3/7/2006

Can't help you much personally as the inverter on our coach has a built-in 4 stage charger that's operating whenever the shoreline is plugged in or the generator is running and the solar charge controller does almost exactly the same thing when we're not plugged in so one or the other keeps the deep cycle battery bank fully charged all the time.
I did a message search with the search term "charg" and found several really good discussions here that have touched on the subject in the past - they might be a good place to start "boning up" on the subject while other members respond to your question. 
Good Luck,

Offline DaveVA78Chieftain

  • 16 year member
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  • Posts: 3592
  • Member since: 2003
  • I own: I don't own one but I'm a vintage RV enthusiast!
  • Year: 1978
  • Make: Winnebago
  • Model: Chieftain
  • Chassis: Dodge M400
  • Engine: 440-3
Re: Charging deep cycle batteries
« Reply #3 on: October 15, 2009, 05:05 AM »
Sent: 3/7/2006

The answer to that question is not as easy as one would like it to be.  It depends on what has been done to your rig.  The original 70's era converters that were installed only had a very small charge rate of around 3-6 amps.  Thats more of a maintenance charge today.   Additionally, the original converters have a big relay in them that switches between the battery and converter.  The relay is energized when 110VAC is available (shore power or generator source).  That is also when that small built in battery charger is working. 
Now todays converters work differently.  Essentially they are more like an alternator.  They are connected directly to the battery.  Converter output will depend on battery condition and the amount of house load currently being consumed.    The engine alternator circuit works the same way.  many have upgraded their rigs to a newer converter but it is not a straight forward change out.   
If you still have the original converter, then an external battery charger is a good addition.  You can get higher (ergo faster) charging rates.  Now the best modern charger is a staged charger.  First stage puts out high current until the battery achieves a certain level of charge.  Charging at that high rate beyond that point will burn up the battery.  It then becomes a voltage regulated charger to top off the battery.  Current ramps off while battery voltage ramps up during this stage.  Non staged chargers work this way (the chargers we have grown up with AND that alternator/regulator circuit on the engine). 
The last stage is a maintenance (trickle) charge.  The Progressive Dynamics site ( had good descriptions of the different charger types.  They still carry some of the parts (relays, charger board, etc.) for the older converters also.

Now recharging a battery can take a very long time.  It is a function of battery size, battery condition and charger capability.  Additionally, it takes longer to recharge a battery than it does to discharge one.   There is a good Boat/RV book that explains a lot about electrical systems at Camping World.  There are also several Internet descriptions about this stuff too.


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