[C320-list] Batteries & Fridge

[wflowe3 at netscape.net]

 Thanks Jeff. I'll take my meter out this weekend and check readings at the battery terminals.

 

 

-----Original Message-----
From: Jeff Hare <catalina at thehares.com>
To: C320-List at Catalina320.com
Sent: Fri, Oct 30, 2009 8:15 pm
Subject: [C320-list] Batteries & Fridge










Hi fellow 320 folks. 

The argument in favor of leaving the refer on to protect the batteries, while 
leaving the charger on for extended periods doesn't make sense from an 
electrical engineering point of view.  Particularly with multistage chargers 
that serve up *constant-voltage* float mode.

No charger with a high a float voltage should be left on indefinitely. Period.
   
Measure your charger's float voltage at the battery terminals with a good volt 
meter and decide based on YOUR OWN charger whether long term float charging is 
safe for your batteries. 

13.3v max (13.8v Gel batts) or under is fine. 
 
If your float voltage is any higher than the above limits, or your batts require 
a lower float, Don't leave the charger on for extended periods. Just don't. 

Having a fridge or even a simple light bulb on WON'T affect the float voltage, 
since the charger's JOB is to hold that voltage constant in float mode 
regardless of the loads attached (within reason). 

So if the charger wants the voltage at 13.8v, the fridge's measley 4amp draw 
ain't going to affect that.  Turn on your fridge and prove to yourself that the 
voltage at your battery terminals remains the same.  

Some people claim *annecdotal* evidence that their batteries died once when left 
on shore power while the fridge was off at the time, and conclude that the 
fridge would have prevented this overcharging. 

That isn't proof that the batteries wouldn't have fried even if the fridge was 
on. 

Some people (myself included) have had their ProMariner die and either provide 
either too high or too low a voltage to the batteries.

In either case the batteries won't survive an extended spell like this. The 
fridge being on won't help with over-voltage and will ensure fast battery 
discharge in the low-voltage case.

So, leave the fridge on if you want cold beer and take comfort knowing that it 
doesn't detract or contribute anything to the charging equation...  At least in 
our physical universe.   :)

If you don't  believe me,  believe Georg Ohm.  ;)

Cheers!
-Jeff