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Open Roads Forum  >  Travel Trailers  >  Modifications and Accessories

 > 2 12v batteries---Mallard TT help

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theoldwizard1

SE MI

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Joined: 09/07/2010

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Posted: 11/29/19 07:57pm Link  |  Quote  |  Print  |  Notify Moderator

RustyMacIntosh wrote:

1) Getting a charge to the house battery from the tow vehicle while traveling. I use a 99 Suburban. ... Or hardwire it from the pigtail connection at the trailer and Suburban.

opnspaces wrote:

I have run a charge wire from the front of my 1996 Suburban to the rear. The wire was already there from the factory, I just had to hook it up. And I have checked many times and it does recharge the batteries from 50% charge to full in the two hours it takes me to drive home from the desert.

OpenSpaces write up is pretty good regarding charging from a 12V power on a 7 pin connector, but you may or may not run into a problem.

Some time around 2000-2005 ALL cras and light trucks start using "smart charging systems". Various manufacturers do it differently and even the same manufacturer have made changes since they first started. These smart charging system put out the MINIMUM voltage to keep the starting battery charged, typically between 13.2V and 13.8V (about 2-5 minutes after the engine has started). This is NOT ENOUGH VOLTAGE TO CHARGE A HOUSE LEAD ACID BATTERY BANK ! Installing heavier wire will NOT improve this !!

What you need is a DC-DC battery charger. Renogy, Redarc and Ctek all make them. They actually boost the available voltage on 12V power pin in order to properly charge the house batteries.


RustyMacIntosh wrote:

2) Issue two that I need to solve is installing two 12v batteries rather than one at the outside front of the Mallard. I am thinking, if I got this right, that I can put two 12v batteries behind the propane tanks.

You would be much better off with TWO 6V golf cart batteries. They will give you more power, last longer and probably cost less.

NOCO does make a plastic battery box that will hold two 6V golf cart batteries, but it needs support rail underneath where it is mounted.

pianotuna

Regina, SK, Canada

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Posted: 11/29/19 08:55pm Link  |  Quote  |  Print  |  Notify Moderator

This is what is balanced and best for twin twelve volt batteries.

[image]

As it often doesn't cost a dime more to do this, I think it is worth the trouble.

If you wish to understand the "why" surf here:

correctly interconnecting multiple twelve volt batteries

Others may say it doesn't matter--but unless there is a compelling reason to not optimize charging and discharging why not do it the best possible way?


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

deltabravo

Spokane, WA

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Posted: 11/30/19 06:44am Link  |  Quote  |  Print  |  Notify Moderator

Lwiddis wrote:

You’ll get minimal recharging via the tow vehicle.


Not if you do heavy duty charge upgrade like I describe in this video

The same technique can be applied to a TT. I will probably do this to my TT soon.


2009 Silverado 3500HD Dually, D/A, CCLB 4x4 (bought new 8/30/09)
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pianotuna

Regina, SK, Canada

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Posted: 11/30/19 09:15am Link  |  Quote  |  Print  |  Notify Moderator

Hi,

I have dual #8 wire--capable of 140 amps of charging. I get almost none except when I run the inverter to power the microwave. The system does little or no charging.

If you wish to do serious charging beefing up the wire is not enough. Get a DC to DC voltage booster, and set the output to 14.6 (or what ever voltage below that floats your boat).

deltabravo wrote:

Lwiddis wrote:

You’ll get minimal recharging via the tow vehicle.


Not if you do heavy duty charge upgrade like I describe in this video

The same technique can be applied to a TT. I will probably do this to my TT soon.


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