Charging battery while being used.

Yes, all that happens is the draw reduces the effective charge to the net amps. Say the charger is doing its rated 40amps and you have a 5 amp draw then you are charging at 35 amps so it takes longer than at 40.

Your equipment will be ok while the battery's voltage stays below 15v. Some chargers will climb to a higher voltage so monitor it to see what yours does.

And just so you know, if you had a converter made in the last 10 yrs, it works exactly the same way as BLF explained.
But one problem that you could encounter, is if you would load the system heavily, the smart charger could be really stupid, and see it as a defective battery, and go into a fault mode.

Hi qwerty,

My solar panels are putting out 11.4 amps. 2.9 amps are going into the battery bank. I'm using the rest.

Next question:

The battery's voltage reading is reduced when a load is being drawn. Could the battery charger over-charge the battery because of this? Would it read the lower voltage of the system and think "I need to charge this battery more?"

Hi,

No, it will not over charge the battery. What will happen is that the charger will help support the voltage--or even power the entire load.

I routinely use my converter (40 amp battery charger) while drawing 160 amps via my inverter to power the microwave.

Batteries essentially "push back" when they are over 85% charged and simply will not accept more amps. Old fashioned "manual" chargers, if left on long enough, may eventually destroy a battery, because the voltage will go high enough to cause them to "gas" and then the electrolyte levels may drop down to below the top of the "plates". Modern "smart" units will taper their charge down to nearly nothing.

But even the old fashioned chargers, if there is a draw on the battery that exceeds their maximum output would not damage the battery. Magnatec comes to mind--they only charge at 5 amps.

qwerty11 wrote:
Next question:
Would it read the lower voltage of the system and think "I need to charge this battery more?"

Yes, that's exactly what I want.

My ole electric center's power converter is not capable of battery charging so I just hook up a portable battery charger to shore power and start the charger. Use the lights and furnace at will. Hopefully by morning my battery is topped off and I can dry camp several more days, repeat!

How about post the charger model so it is not all guess work?

It would have to be a very rare and isolated case where you could draw perfectly the right amount of power to have the charger hold voltage over 14.4 volts for an extended period of 8+ hours after the battery is fully charged. Besides wet cell batteries are fairly tolerant of being charged a bit extra. Better overcharged a bit than chronically undercharged which might be a bigger issue.

smkettner wrote:
How about post the charger model so it is not all guess work?

This is the charger: http://www.batterychargers.com/ProductDetail.aspx?ProductName=94026806ACP

Picture it working just like your truck's battery. You run your radio, lights etc, while the alternator is charging the battery. It doesn't hurt it at all.
My 1969 Avion had a small trickle charger that came with it when it was new. I installed two batteries outside the camper and connected a Schumacher smart "ship n shore" charger to them. I've never had a problem. I also installed a battery isolation switch so I can pick "battery 1", "battery 2", "both" or "off".