Batteries charge very slow when running the generator

[jdquattros]

Sent: 10/16/2002

Hi- I have a 1979 Chieftain with Onan genset. The coach battery does not charge quickly at all when using genset. The on-board ac/dc battery charger may be designed as a trickle charger. Am I supposed to use the engine to recharge coach battery.
Thanks

[Dave1210]

Sent: 10/16/2002

I have noticed also that my 4kw gen does not seem to charge the battery very good, probably a trickle charge like you mentioned. Looks like (when I get the heat working) I will be in the same boat you are in.

Some things I have tried in the past w/ the old battery were a small solar panel, approx. 8 x 14, this seemed to help only when storing it. I also tried bringing a battery charger and leaving it hooked up so when I turned the gen. on it and then plugged in the charger it would charge. This seemed to help a bit but looks funny and it a pain to do. I guess from this message you know what not to try. Dave

[UluzYarx]

Sent: 2/17/2004

Hi Id

You say your generator doesn’t charge fast ~ your onboard charger may be a trickle charger ~ your coach battery goes flat over night.  Not much information for me to make a sensible guess so I'll give you some information instead of a dedicated answer.

Your coach battery needs charging at between 10% and 30% of its capacity.  More than 30% will shorten its life. Less than 10% will shorten its life.

If your charger stops charging at a low voltage it will shorten your battery life.  If your charger stops charging at a high voltage it will shorten your battery life.

Your battery ‘remembers’ being undercharged and being run down too far, and it says to itself “If he isn’t going to treat me nice’ I won’t take a charge and I won’t hold one either”.

Coach batteries have a short sad life.

You ask, are you supposed to use the engine to recharge the coach battery?  The shortsighted answer is, if it gets you out of trouble, do it.  The technical answer (based on my guess that you have a diode between your alternator and your coach battery and a long wire run) is ~ almost certainly not!


If your coach battery gets its charge via a long wire and a diode it will be lucky to get 13 volts out of a 14v alternator (I use simplified figures for voltages, you cannot take them as accurate ~ see the Adverc site).  If you have relay and a long wire, it will probably get 13.5v on a good day, and coach batteries don't get many of those.<o:p></o:p>

  I sixpence says ~   Run an automatic battery charger that will give you a charge rate of at least 10% from your generator to get your coach battery full.

·    Get your coach battery(ies) checked, and replace it (them) if doubtful.  Always replace all coach batteries if you need to replace one.

·    Fit a second alternator to your engine to charge the coach battery.

·    Got to www.adverc.co.uk where you will learn much more about batteries, charging, and the options open to you than you’ve got from my simple guff.

All the best Dave.