This is a misconception. An ACR product like the 1314/5 has no real idea
how fully charged either battery is. It only sees a voltage. If the
voltage it sees is above a defined threshold it connects one side to the
other. Depending on the specifics of the wiring scheme used it can
switch to charging both batteries no matter how low the first battery is.

The way some companies promote their products seem designed to get
people to think they have more smarts than they really do.

Mark

Harold Teer wrote:
> Like Loren, I have the 1315 and have a built in battery charger.  When
> driving, the alternator first charges the starter battery and then charges
> my auxillary battery bank.  When plugged in to shore power, the battery
> charger first charges the auxillary bank and then once they are fully
> charged, the starting battery is topped of, although that really is never
> needed since I run the radio, etc off the auxillary batteries.  This setup
> has worked perfectly since 2009 for me.
>
> Harold
>
> Harold Teer
> 1991 Westy -- VANGAUX
> Harrisonburg, VA
>
>
> On Tue, Aug 25, 2015 at 2:03 PM, Loren Busch <starwagen@gmail.com> wrote:
>
>> ​RE: 1314 or 1315
>> 1314 is one way, engine battery to aux battery only.  1315 is two way.  If
>> charging the aux battery (solar?) then when aux battery reaches full charge
>> (13.3 v?) the charging source will also top off the engine battery.
>> But some have argued that this takes away from getting full charge going to
>> the aux battery.
>> I have been running with the 1315 for several years now (and with 120 watts
>> of solar) and have wondered about this issue.  But with the 1315 and solar
>> (plus a battery charger wired in for when I have shore power) I have the
>> assurance that my engine battery will start the engine when I need it.
>> YMMV
>>
>