wopachop wrote:
I have two brand new 6v from costco. I pulled 20amp hours out of them a week ago and then fully charged with an automotive battery tender.
Today i put a 3.8a load on them and voltage is down at 12.15v after a few minutes.
Are they supposed to sag that much under a little 4amp load? Did a quick search and all im seeing is topics about voltage sag while under solar power. My batteries are on the garage floor.
edit: I should have checked early. My watt meter is saying 12.15v.
But 2 multimeters are saying 12.27v and 12.3.
What "tender" are you using??
Most battery Tenders are pretty darn wimpy on output, .5A-1.5A MAX.. Nothing more than a high priced glorified "trickle" charger.
At that rate it will take MONTHS to fully recharge your batteries..
From Battery Tenders manual for their 1.25A maintainer it says..
"TIME REQUIRED TO CHARGE A BATTERY:
The Battery Tender® charges at a rate of 1.25 Amps or 1¼ Amp-hours per hour. Therefore, a fully discharged 15 Amp-Hour battery will take approximately 9½ hours to recharge to 80% capacity. " You need to wallop them with a charger with considerably higher amperage capacity than a battery tender..
Battery tenders are not designed to "recharge" a DISCHARGED battery, they are only used to MAINTAIN A FULLY CHARGED BATTERY! In other words battery maintainers are there to prevent your battery from self discharging..
There are off brand "maintainers" which offer higher amperage capacity than the original "Battery Tender" but since you have a RV, why bother, your RV already HAS a high current charger built in (the converter), why not let your RV converter do the heavy work??
