Not sure if I need this or not... so maybe someone can shed some light on it for me.

I am running a WVO set-up and have a bunch of electric gauges, interior lights, and soon a converted to power a lap-top and charge other devices. Should I put in a third batttery to power this stuff?

I know you can set it up so it is only charged when it drops below a certain amp. but I dont know how.

Thoughts?
Thanks,

if you do it, you get a battery isolater which ties into the alternator feed and it decides which battery gets what. available at parts stores, and used when tying into rv's charging system.
it is probably all unnessary, just gonna create more load on your alternator when they are low. having the most powerful altenator as the best solution, as it will keep all levels up when the load is high

Batteries are like banks, you can't take it out until you put some in! The alternator is responsible for putting the charge into the batteries so it must be large enough to exceed the normal load of the accessories.

The second consideration is the fact that most standard automotive batteries are designed for short duration drawdown. They like to maintain voltage and dislike being discharged and charged. The deep cycle marine type batteries are designed differently and will handle discharging and recharging better than the standard automotive battery.

If constant load is the goal, a deep cycle battery is a better choice but there is a drawback in their design, they won't normally handle heavy loads such as starter or glow plug load. They will power electronics and other accessories adequately. They tend to lose voltage when not in use faster than a standard lead-calcium battery.

If the uses of your vehicle are such that you need different batteries to handle the different jobs, perhaps a deep cycle battery for the accessories, along with the above-mentioned battery isolator is in order. A heavy duty alternator would also help.

Installed correctly, it should maintain the two truck batteries for starting and operating the vehicle while keeping the auxillary battery charged and able to operate the other accessories. The isolator will allow the aux battery to discharge without dropping voltage in the truck batteries. This allows you to start and run the truck, even if the aux battery is run down.

I am running a WVO set-up and have a bunch of electric gauges, interior lights, and soon a converted to power a lap-top and charge other devices. Should I put in a third batttery to power this stuff?


That depends on if you want to power all that for extended periods of time while the engine is not running, on how much power you are going to draw and on what capacity your batteries have. Without knowing more, it's impossible to tell.


Try to avoid plugging the converter into the cigarette lighter. The stock wiring is way too thin to draw much current. You need to consider how much current the converter will draw and to run wires from a battery to supply it.

Even these plugs are usually rated for only either 8 or 16 amps --- I couldn't find one rated for more. A 200W converter at 80% efficiency would already draw about 21 amps at full load if it would get 12V. But since the wiring is too thin, it might get about only 10.5 to 11V, so it could draw about 23 to 24 amps.

The problem is getting wires --- I still need to run some wires into the cabin to have a good power supply for a converter and other things, but 10 gauge is too thin to be able to draw at least 60 amps ...

First I would upgrade/clean/change the weak parts of the factory wiring. Then go for a better Alternator, a 100amp unit can be had at the parts store for cheep. Then go for some decent deep cycle batts.
Personally I wouldn't waste money on another battery, and an isolator. Unless you plan to run a lot of accessories with the motor not running.

The problem with the more powerful alternators is that you don't get them with a lifetime warranty which to have was more important to me than having a more powerful alternator.

And you don't need one unless the demand is really high. The truck itself doesn't need much power when it's running, only about 150W for the lights and a bit more for the fuel shutoff solenoid and eventually the A/C compressor clutch. That means it's drawing about 16 to 20amps, and that leaves you with at least 55 to 65amps at your disposal with the standard 75 or 85amp alternator.


The problem with deep cycle batteries is that they eventually need to be charged differently. Unfortunately, the manufacturers are not very clear about this because they want to sell their batteries which would be a lot harder if people had to buy special charging devices (like Sterling makes them) along with the battery.

Not sure if I need this or not... so maybe someone can shed some light on it for me.

I am running a WVO set-up and have a bunch of electric gauges, interior lights, and soon a converted to power a lap-top and charge other devices. Should I put in a third batttery to power this stuff?

I know you can set it up so it is only charged when it drops below a certain amp. but I dont know how.

Thoughts?
Thanks,


cusipata, you need to answer some of the questions raised in the responses above.

If you are going to use the extra power while the engine is running, you do not need an extra battery, only an alternator that supplies adequate amperage for your usage.

If you need power while the engine is off, get a deep cycle battery and and a battery isolator. You still need to determine if your alternator is sufficient for the battery recovery (charge). This will insure that your two regular batteries are always fully charged for your engine start.

FYI, here is a link to battery isolators, not necessarily the best brand:

http://www.pplmotorhomes.com/parts/rv-converters/rv-battery-isolator.htm

Do you know how these isolators work? If they use a diode, they create a voltage drop so that the auxiliary battery will never be fully charged.

To avoid the voltage drop, many people use a relay instead that connects the aux battery once the engine is running. The disadvantage is that suddenly a lot of current can start to flow between the batteries when they are connected --- but it seems to work pretty well.

However, the alternator with only its simple voltage regulator is not a good battery charger --- that's not it's main purpose anyway. If you need more battery capacity, the simplest setup would be to have all batteries wired in parallel, permanently, using identical batteries, as many as you need/want. The disadvantage is that you could still drain the batteries to the point where you can't start the engine. The next step is using a relay to separate supplying batteries from starter batteries. The best way to do it is probably to get a battery charger designed for the purpose like this one: http://www.sterling-power.com/products-altbatt.htm. The disadvantage is that it's rather expensive.