no the maxx are 850 CCA ,, not 850 amp batteries.. they are around 600 amps but the construction is for short burst not long discharge like a heavy GC battery.. they quick discharge and quick recharge for the most part.. will have to check tomorrow when we good some good sun but think it might be closed to charged. either way it will get 4 days or better and we are expecting sun everyday and no clouds.. that should give it a good deep charge either bring them back or get the replaced.

 

The amp hour rating of a 850 CCA group 65 starting battery is roughly 86ah

 

Another recommendation to clean the cable ends. A little bit of crud can really compromise the system.

 

A week of the dongle being plugged in shouldn't zap 2 850 CCA batteries. I've left mine plugged in for 2-3 days w/ the exact same batteries and only saw a 0.1v drop at the batteries when it came time to start. That was also powering one of those power port volt meters displaying current voltage the whole time.

 

@bigb56 , I am glad you found the link useful. When shopping for an AGM battery, please keep in mind that not all batteries are created equally and this goes for AGM as well. "Pure lead" is the key when selecting an AGM battery that you will count on to be reliable and last for years to come. Don't be fooled by the discounted AGM batteries. There is nothing wrong with them and I have one in my vehicle and it does well, but it is not a set of 930 CCA batteries by any means.

 

that is different that what i was seeing on the rating.. but now when i search i see the Ah is only like 65 to 75 for a group 65- 850 cca battery.. that explains how in one good half a day my MPPT controller had already backed off the amps to like 5 and volt were around 15 in the afternoon.. we left to head to beach for a couple days for the wife's mental health in helping her deal with the lymphoma treatments going on so I just left it hooked up and let it push in amps at a slower pace and volts to top the battery off..

when we got back yesterday afternoon I unhooked the charger and let it settle over night and seems steady at 12.3v.. will let it sit a bit more as we have my brother in laws 2019 f-150 ecoboost as a spare which get like 22 mpg on regular vs 19 mpg on diesel fuel.

dongle was plugged in for over 2 weeks or more on first jump. off. they suck more than you think i hear plus the normal crap on truck that suck a little as well.. hope the battery issues are now done and not much damage to batteries.. easy enough now to keep a trickle charger on as we are plugged in to friend outlet so we have elec in the airstream abet 15 amp but elec.

I have looked into the pure lead AGM batteries but for me the up front cost is a bit more than i like and they will go like 5 -6 yrs or so and i get 6 yrs out of lead acid more or less as well.. the advance DieHard Platinum AGMwith 3 yr warranty,, ( same as walmart maxx ) is over 220 each. the odyssey brand is over 300 each and no mention of warranty, (which i find odd)

the walmart 65 maxx runs 100 each and 3 yr replacement warranty for me makes better sense.. just need to be more diligent about not allowing them to get down if not driving often enough..

anywho thanks for the help to all..

 

Are they sitting at 12.3V disconnected or connected with a load? If disconnected a resting voltage of 12.3V is pretty low, 12.7V would be ideal.

 

i was thinking the same thing.. they are hooked up to battery cables so just normal load stuff with truck not running.. I checked my other vehicle the mazda at it was at 12.3 volts as well.. 12.7 is a good sitting with no load voltage for sure.. I will keep checking throughout the day to see if volts float down more..

 

Hopefully hasnt been covered... but have you checked your battery cables? Turns out i was running my truck for almsot a year on 1 battery, because the passenger side, through lug... was completely oxidized inside, and that battery was just sitting there pretty, doing nothing. Not charging, not helping start. Nuthin.
if your on one battery... that could explain low voltage, and faster than expected drops.

 

I will just leave this here for you...

Also remember voltage is not the entire story on the health of the battery.