Generator vs Battery/Inverter/Solar

DiploStrat wrote:

HMS Beagle wrote:

It may be a little overboard, but I have considered adding the second alternator to the truck (an option on most 1T) but keep it off the truck electrical system, feeding only the camper house batteries through a good external 3 stage regulator. But in the sunny West, I find that 200W of solar on the roof is all that is every needed.

Some comments/observations, if I may.

-- I don't have a Ford shop manual, but I suspect that you will find that you already have a multistage regulator on your truck.

-- The "trick" to getting your truck's alternator to step up and do its share of the charging is to lower the resistance between your starter and camper batteries. Most RV's are wired with tiny 6AWG runs between the two batteries. (Worse, some also use diode isolators.) With a wire that small, you can drive all day and never really achieve a decent charge of your camper batteries.

-- You really need at least 50mm2 of copper (and a good ground) to make things start to happen. This means a minimum of 1/0 AWG cabling. I use a pair of 1/0 AWG cables, which comes out to 100mm2. Once you get the resistance low enough you will find that you start to get a significant bulk charge from your vehicle alternator, a charge that quickly (1 - 2 hours) gets you into the absorb stage where your solar controller can finish the job.

This voltage drop calculator is a nice tool. I have preloaded it with the following assumptions as a starting point:

-- 14v
-- 1/0 AWG
-- 100A alternator
-- 20 feet of cable from the alternator to the camper battery.

As you will see, the voltage drop is so such that you are actually starting to charge at a typical "float" voltage. That voltage will rise, however, as the amp flow decreases. (For giggles, reduce the wire size to 6AWG, a very common size, and the voltage drops to under 12.5v; essentially useless.)

Voltage Drop Calculator

Based on my experience, I would suggest that rather than spending money on a regulator to replace the one you already have, spend the money on good cabling, it will be expensive enough. If your camper is removable, you will have the additional cost of big Anderson Power Poles or similar detachable connectors.

Best wishes.

Nice calculator. Thanks for that link. Just remember it's not just the size of the cable. The thinner the strands the more resistance you will have. If you were to use welding cable because it is nice and flexible you will not get as much voltage as with a heavy stranded cable/wire. Sorry don't have a link to prove that.