BobS0327
I have a Generac Guardian 13KW, Model 005242.  Serial number is 4673568. It was installed in February 2007.  I replaced the battery this last September and the battery totally discharged to the point where it would not start the generator in less than a month.  So, I replaced this first battery with a brand new battery.  The same thing happened again , the second battery died within a month.  Now I'm on my third battery and it appears to be dying.  When I installed it about two weeks ago, the VDC read 12.6 now it's down to 12.1  All three batteries are type 26 batteries purchased from Walmart.  The Walmart techs checked the first two batteries and their test equipment indicated that both batteries should be replaced.

I'm a homeowner and not a Generac installer.   I don't have a clue on how to solve this issue. Thus, any assistance would be greatly appreciated
Quote
JoeL
your battery is not getting a charge from the charger, or the charger is bad, or the charge control relay is bad, or bad transformer. First check at the charger.. wire # 0 and 13 supplies charge to the battery and should be around 13.8 Volt DC, if no voltage there, check the input voltage to the charger, wire # 224B and 225B. you should have 16 Volts AC.   if you have low or no DC voltage at the output, and you have 16 volt AC at the input, then your charger is bad. If you find the charger is bad Please support this site and order part # 0A18010SRV from Ziller.
Quote
ZZZRSC
    Lead Acid batteries self discharge about 4%/week of its amperage capacity, even when nothing is connected to the terminals.  This is due to internal chemical reactions and is completely normal, even in Gel Cells and Deep Discharge batteries.
    You should not let a 12 VDC battery discharge to less than 11.6 volts or it can be damaged, less than 10.8 volts some damage is almost certain.  Most automatic chargers won't even attempt to charge a battery when it has dropped below 10.8 volts. 
    I would disconnect the battery and charge it fully with an 8 amp or larger "smart charger" at least overnight. Then I would make the checks that Joel describes above and order a new charger if necessary. Make sure your are using a good quality meter, and not a Harbor Freight model.
Quote
BobS0327
Thanx for the info.  Unfortunately, I'm having a difficult time locating the physical location of the battery charger.  The installation manual provides the wiring schematics etc. but there's no indication of where the battery charger is physically located.  I've checked the Automatic Transfer Switch and  what's visible within the generator enclosure but did not see anything resembling the battery charger.  So, I'm ASSUMING the battery charger is out of sight just below the control panel.  Is my ASSUMPTION correct?  I'm a homeowner not an installer.  So, please pardon my ignorance.

Also, the battery is currently reading 12.1 VDC.  So, I guess I'll have to invest in a quality trickle charger.  Any recommendations on a good "smart charger?  I'd also like to use it for my automotive batteries.

Yep, I do have a good Fluke multimeter. 
Quote
78buckshot
Hi BobSO, the factory charger is located under the control panel in the generator, two screws and plug-in wiring, easy to replace. The P/N is 0A18010SRV, Ziller will have it in stock and can ship it same day, call them in the morning and they'll get it right out to you. For general battery maintenance I like the Deltran Battery Tender series, I use several to keep my idle batteries in good shape. The 750ma model is too small to keep the generator running but will maintain the battery until you replace the factory charger.
Quote
BobS0327
I checked the voltages using a Fluke Multimeter and wire #0 and 13 had ZERO voltage whereas  wire #224B and 225B had  19 VAC at the input. Joel's post indicated that I should have 16VAC at these wires.  So, I'm assuming that my 19VAC reading is within normal parameters and have ordered the replacement 0A18010SRV Battery Charger from Ziller Electric.

Also, just want to say thanx again to all those who have helped me.
Quote