Thanks for the solid responses dwh.
No worries.
You confirmed what i thought with the dual battery system charging off of the alternator. I have just been getting conflicting information on this and various other forums.
Welcome to The InformationSuperInterWebsHighwayNet.
my manual toggle switch i added into the system outlined by Evil Dave just gives me the option of disconnecting the system when the truck is running, not connecting it when the truck is off. I just put it in so i could keep the house battery disconnected from the starter battery/alternator until after i start the truck and give it a minute before putting the extra load on the system.
No worries.
The alternator reading i gave of 14.17 volts was without the house battery hooked up.
Probably higher at above idle.
The charge controller is hooked to the battery with about 2 feet of 10awg wire.
Good enough.
the fridge is wired to the same battery terminals as the charge controller with about 10 feet of 10awg wire.
One way distance or is that the full length of the loop?
According to this:
http://www.calculator.net/voltage-d...ce=10&distanceunit=feet&eres=4.7&x=41&y=16
Even with a one way distance of 10' (20' loop) you should only see a 0.01% drop. Or 12.8v dropping to 12.7v under a 4.7a load.
Same if you started with 12.0v - so if the fridge is seeing 11.8v, then the battery is probably not any higher than 11.9v.
I tested the amp draw with a multi-meter at a fuse next to the fridge and got a fluctuating draw between 3 and 4.7 amps for the first 5 minutes after start up. This is an appropriate draw for the ratings given on the fridge and I would expect it not to get any higher.
Sounds about right. But a normal multi-meter can usually only test up to 10a before it blows its internal fuse. A clamp-on meter is highly recommended so that you can clamp it around the hot wires on your alternator, engine battery and aux battery to see how much power is really flowing.
The monitor i am using is an MT-5. it is designed to plug into the charge controller that i am using, which is a Tracer mppt 40A charge controller.
Found the manual for that online. More on this below.
I stated in a previous post that i talked to a renogy rep and was corrected in my miss use of the state of charge readings given on the display. The SOC reading are only accurate when plugged into the solar array and the array is in full sun. This is something that was not mentioned in the manual, so maybe it is common knowledge that i just didn't know.
No, it's common knowledge that CSR people are generally full of crap.
How can that charge controller know the state of charge? It needs two pieces of data: A) it knows the voltage on the charging loop (battery) side of the charge controller and B) it knows how many amps are flowing to the battery side.
So yea, it can't know anything without full power on the solar side.
What it cannot know, is what sort of loads are also on the battery side. Say the charge controller is set to "know" that the battery is full when the amp flow drops below 2a at absorb voltage. But your fridge is drawing 3a. Even if the battery is full, the charge controller thinks it isn't.
(This is actually a common problem. What it results in, is that even if the battery is full, the charge controller thinks it isn't, so it continues in absorb mode (elevated voltage) and ends up overcharging the battery. In most cases, it's not critical with a solar charge controller, because after a few hours of overcharge, the sun goes down and all is well. But if a shore powered multi-stage charger gets fooled that way, it can keep going for days and will cook the battery.)
At any rate, that charge controller's battery state of charge reading should be considered to be nothing more than a guess which might, if you're lucky, be half right.
In any case, I think I am beginning to have the same suspicions as you, that the battery is never actually full. I believe the charge controller may be giving me a "full" indicator and switching to "float stage" before the battery is actually as full as it could be. Going to keep reading through manufacturer websites to see if i can get a better understanding of how this might be happening/ how to check for it.
Manual:
http://www.renogy.com/template/files/Manuals/20A-30A-40A-MPPT-Solar-Charge-Controller-Manual.pdf
Profile graph on page 7.
Charge voltages on page 22:
Okay, first of all what they call "boost" stage is what everyone else calls absorb stage.
Also, it DOES have an equalization function, which it does automatically every 28 days.
So, when set to...
Flooded: Bulk (basically running wide open with current limited to no more than 40a) until the battery voltage reaches 14.8v, then enter "boost" (absorb) stage, where it holds a steady 14.8v for 2 hours then drops to float at 13.8v. Every 28 days, it cranks up EQ function, which pushes it up to 15.5v and hold for 2 hours.
That charge profile is kinda crappy. Normally an absorb stage is at a somewhat lower voltage, and lasts until the amps flowing has dropped below 2-3 amps. When the amp flow drops that far, it's because the internal resistance of the battery has risen so high, that hardly any amps flow. In other words, the battery is full.
Still...it's okay fo do absorb at the same voltage as bulk (that's even the recommended profile for Odyssey batteries). But that 2 hour timer...that's very arbitrary. Depending on the battery, it could maybe absorb enough to be full in 2 hours...or it might take 6 hours.
This would be the charge profile that I'd use for AGM - EXCEPT for that stupid EQ. You don't want to push any sealed battery up to 15.5v except if basically freezing conditions. So if you can't turn off the EQ (I don't see any way to do it in the manual), then you can't use that for your AGM.
Sealed: Bulk up to 14.4v, then hold in 14.4v absorb for two hours, then drop to 13.8v float. Push it up to 14.6v every 28 days for EQ.
That profile is really crappy. Bulking to 14.4v is fine. Absorbing at 14.4v is fine. But I highly - HIGHLY - doubt that after 2 hours in absorb your battery is actually full. And that EQ is useless. For an AGM, two hours at 14.6v is hardly enough to do anything - especially if the battery wasn't fully absorbed when you did it.
We can just ignore the GEL setting.
Unfortunately, I don't see any programming options for that unit, other than screwing around with the goofy night/day timers for the load circuit.
Dude...you need a real charge controller. That one is certain to prematurely kill your battery by constantly undercharging it.
