Regulating Trailer Battery

[Ron S.]

I think my first post did not go, so I will ask my dumb questions again. My 1985 Scamp has neither Converter nor Inverter (nor much of anything else that I can locate). However, the trailer battery does receive a charge from the tow vehicle when connected. I use the trailer battery very little if at all (minimal lights). My questions: On a long trip, is the trailer battery regulated by the tow vehicle? Is there any danger of overcharging it, or affecting the tow vehicle battery in any way? Many thanks in advance. Ron S.

[Harry Young]

Ron,

These are a few thoughts on a subject that has many variations regarding charge needs and the many configurations different equipment may require.

If the tow is wired to charge the battery from the tug alternator its charge regulator will adjust to the needed charge in most cases (check equip. specs for vehicle)...if your wise, you will have in the least a battery isolator in the tug so the tow battery cannot drain the tug...they will charge together and drain separately. Battery isolators need to be matched to the vehicle charge circuit configuration.

Beyond this basic set up there are variations and gadgets aplenty.

If you choose not to use the battery isolator having the tug and tow share the charge circuit that is o.k. not best....but unplug the tow every time you stop any length of time.

In the case of the tow using a deep cycle only battery the advice is not to charge it faster than 10 amp hours...you need a gadget to limit the charge from the tow to that limit.

There are hybrid batteries that are deep cycle/start batteries... they can be charged over the 10 amp deep cycle rating and work around that limit not needing the gadget.

The real reason to consider wiring so the tow and tug share a common charge circuit is this...when the refrigerator is being powered 12v in transit...its 12v draw is significant needing a steady replenishment of charge as it operates.

Or in my case I run the long desert distances running the refrigerator on A/C using my inverter.

90% of the time I use the charge/converter to charge it at home the day before camping and do not worry about it...I run 5 days on battery then run my suburu/robin generator 2 hours and its done for another 5 days.

I prefer to leave the fuse out of the charge circuit thru the tug tow plug unless I really need it.

Others have habits different from mine with good reasons for them, when there are more responses I am sure it will be clearer how you want to do this.

Happy Camping, Safe Trails.

Harry

[Roy in TO]

I prefer to leave the fuse out of the charge circuit thru the tug tow plug unless I really need it.

I don't understand your logic. How does one predict when they will need a fuse?

[Harry Young]

The comment was meant to mean that though my tug is wired to charge the tow I rarely use it, unless the trip is very long, or the desert is many miles of hot highway making it a slog that pre-cooling the refrigerator does not work well.

I remove the fuse to the charge circuit disconnecting the charge power to the trailer plug 90% of the time, disconnecting the circuit for use later when I decide to replace the fuse then.

The reason I do this is I feel putting an additional load on the alternator is not worth it unless really needed, I run the A/C allot in the tug and its a power hog too, I also travel with my lights on, I do not want to shorten the cycle life of the expensive alternator by utilizing this axillary charge circuit unless its needed.

The modern solid state voltage regulators in some vehicles of the past were somewhat moody when heated up when nearing their capacity, I have had issues with some made, my feeling is they are rated too high in their stated amps that they claim to handle.

Its a habit I have developed based on my past camping trips, some where I was stuck changing an alternator in the hot boonies...

The comment was stating just a preference to not use the charge circuit unless I wanted too.

I re-read the post after your question and had to smile at myself, I can see where the question entered your head.

I only use the circuit when there is a draw on the battery when in transit...otherwise I choose to charge with the trailer converter which is more sensitive to the state of that particular battery.

Hope this explains it.

Harry

I don't understand your logic. How does one predict when they will need a fuse?

[CD Smith]

I am just the opposite of Harry.

I connect the 7-pin connector to the Escalade and never worry about the regulation of either battery. There is no isolator or relay in the Escalade and I never remove the fuse even though the Escalade is quite a current hog.

I have no doubts about the capability of the alternator to support both batterys, which by the way takes very little of the amps produced by the alternator after they are charged.

[Roy in TO]

I remove the fuse to the charge circuit disconnecting the charge power to the trailer plug 90% of the time, disconnecting the circuit for use later when I decide to replace the fuse then.

...

Hope this explains it.

That explains it, my brain was thinking the fuse was a fuse, not recognizing that the precence or abscence of the fuse is in essence a switch.