Outline · [ Standard ] · Linear+ Off-grid electrical, Battery replenishing

[Slymer]

A question about having drained the battery while off-grid. When this happens will 12V things still work if the truck is running, or will I have to wait until the TC battery charges from the running truck. Most specifically I am concerned about the power jacks. Thanks.

[Spanky]

You won't get a blast of charge from the truck so i am sure you will have to wait. The truck really does not charge very fast. At idle it will take the truck quite some time to charge the battery even if you are not using anything inside.

[aqualung]

If you flaten the TC battery there will be a lot of voltage drop across the wiring between the truck's alternator and the TC's battery when the truck's running. It will take some time for the alternator to bring the TC's battery up to a reasonable charge level before you will see a good 12V in the TC's system so as Spanky said, you'll have to wait. Even when your TC's battery is mostly full you'll see voltage drop between the alternator and the TC's battery, enough that the TC's battery won't charge well at all.

If you look at the deep cycle battery specs, a proper charge level is well over 14 volts at the battery terminals. The Trojan batteries I have state a proper charge level of 14.8V, I never get that from the truck alternator. The alternator puts out 14.4V to charge the truck's battery, by the time that gets to the TC's battery its closer to 13V at best. Now with the Torjan batteries, 13V is the trickle charge or "float" charge level so its safe for the batteries but it means that getting a full battery charge will take forever if it gets there at all.

Even the typical 12V Converter in a TC doesn't provide proper charge levels for deep cycle batteries. They're really intended to run the TC's appliances and not there to charge the batteries.... at least not in a hurry. Adding a real 3-Stage battery charger takes care of that. The Converters will eventually charge the deep cycle batteries but since their voltage levels are low for charging (typically 13.5V) they also take a long time to charge the batteries, just like the alternator. I guess that's why they call them converters and not battery chargers....

[Oscar]

All the above.

One of the first things I install when I get a camper is a battery disconnect. I've had my TT sit for 5 months and the battery was 95% when I fired the thing up as it wasn't drained by the condition monitor, smoke and CO alarms etc etc.

[Mayday]

Another thing to be aware of: If you have a battery isolator between your TC and truck, it may limit your charging options. Many TC's use Blue Sea products and most have limitations. Sort of long winded but here goes: If your TC batteries fall below a certain (or threshold) voltage (typically 11.2 volts), the isolator will not let the truck feed charge the batteries. (it has to do with battery management). There are models of blue sea products that work at lower voltage levels (mine is 10 volts) and their model 7611 will allow current flow to your batteries (or if you have one, a "Battery Wizard" or charge management device) with no threshold voltage. ie: they will always charge once the vehicle is started. If you have a "Charge Wizard," it will manage the current flow to your batteries to avoid cooking them. (too much charge, too fast).

I ran into issues on my Lance with the dual batteries running low after a day or two of boondocking with minimal electrical use. Some of it was attributable to some of the devices that are always on (audio, refrigerator, antenna, sensors, etc.) I ended up installing manual shut offs to some of the devices and that seemed to help.