Info on Automatic ("smart") Battery Charging Isolators and Relays

[PwrWgnWalt]

In trying to find the best modern alternative to my MH's old-style diode Battery Isolator (a Sure Power model 702, which seems to be dead or dying), thought I'd share my research into electronically controlled, automated relays in case someone else might benefit from it.

In years past, a MH might have either a manually activated solenoid with a "MOM" (momentary) or Dual/Norm/MOM switch, or, a simple diode-based battery isolator.  Others have written about these, so check out these posts for more on the OEM styles:

1. Dave has done a great job covering consatant duty solenoids in his reference (e.g., Winnebago)http://www.classicwinnebagos.com/forum/index.php/topic,1250.msg1285.html#msg1285 ; and

2. Here's one covering the diode isolators (e.g. Sure Power)
http://www.classicwinnebagos.com/forum/index.php/topic,3813.msg10220.html#msg10220


There seems to be a lot of variations of the newer 'automatic' Bi-directional Isolator Relays coming into the market in recent years, but the main thing I was interested in was a gizmo that would charge both the chassis and coach/house batteries when there was any source of charging (by an alternator, shore power, a stand-alone charger, or even solar) - this feature is why they are called "Bi-directional". And I wanted to see if there was some way to have it done automatically, so I didn't have to remember to flip this switch, or that one... or so someone else didn't inadvertently do something harmful. Although these all still use some sort of solenoid or relay to accomplish the switching tasks, they mostly remove the manual process of switching between 'combined' and 'separate' battery banks. Instead of a human flipping a switch, these use electronics to sense current and close/open a relay, but without the voltage loss associated with the diode method (which is why some MH mfr's used a constant duty solenoid and MOM switch, instead of the diode-isolator).

Some modern products have the solenoid built-in, others use a remote solenoid/relay.  The action of combining/isolating batteries is accomplished by electronic monitoring of the voltage in each battery bank; at certain levels the banks are automatically combined or separated.

Product Name & p/n              Amp Ratings           "Combine"    "Isolate"     web info   
_                                    (Continuous/Surge)        limits          limits                                                             .

1. Sure Power 1315-200        200A / 600A           >13.2v         <12.8v      http://www.waytekwire.com/datasheet/80003.pdf

2. Blue Sea ML-ACR 7622       500A / 1100A       >13.5v 30sec <12.35v 10sec
     [latching relay]                                        >13.0v 90sec <12.75v 30sec  http://www.bluesea.com/productdocs/7622

3. Samlex ARC-160                160A / 480A        >13.2v 7sec   <12.8v 60sec
                                                                                     http://www.donrowe.com/user_guides/samlex/arc_160.pdf
    {A company rep said the low surge rating was probably not conducive to high amperage draws in combined mode,
      like we might have when cranking a 440-3. The unit can be set to lock out this feature.}

4. Intellitec BIRD 00-00362-100   n/a                >13.1v 150sec   <12.6 60sec     http://www.randkproducts.com/bird-gas-wlow-threshold-p-232.html
     [requires a constant duty solenoid, e.g., Tekonsha 7000 or 7001, to attach the battery cables to and do the switching]

5. Blue Sea SI-ACR 7610        120A / 210A        >13.6v 30sec     <12.35v 10sec
                                                                 >13.0v 90sec     <12.75v 30sec  http://assets.bluesea.com/files/resources/instructions/990170140.pdf
     {the "SI" is short for Starting Isolation, this device can be set up so cranking amperage does not pass through it}

These are but a few, but look like they might work well in MH's (most seem to have high enough amperage ratings, but some need to be locked out of the engne cranking process manually - like the Blue Sea "SI" or Samlex ARC-160)

Feel free to add more to this thread...

- Walt

[DaveVA78Chieftain]

While the constant duty rating is important for these solenoids, the "intermittant" rating is also important. 

When you use the "AUX Start" feature you can be pulling over 400 amps of current for engine starting.

Most RV mfg's installed solenoids rated for 100 amp continuous duty.  These typically had a "intermittant" value of 450-600 amps.  This intermittant period is normally for 10 seconds max with a 30 minute cool down period.

Being the humans we are, if one has to use the "AUX Start" feature, we normally do not wait 30 minutes so that can shorten the life of the solenoid.   This high current make-and-break cycle can cause arcs in the internal relay contacts which can either weld them together or result in corroded contacts that do not conduct current well (high resistance).   

The reason I prefer a solenoid separate from the Bi-Directional controller is this commonly seen failure potential of the solenoids.  Not only does this failure mode apply to the cross-connect solenoids, it also applies to the coach or chassis battery disconnect solenoids. 

Many people with newer rigs (larger loads) are converting to solenoids with silver instead of brass internal contacts.

Dave

[PwrWgnWalt]

Got a package from Marine Parts Source today to help me on this weekend's project. Am beginning to clean up all the house 12 volt wiring and systems... (Note: the starter battery will get new cables, both + (to starter relay ) and - (direct to the engine block, with ground strap from there to frame)

Blue Seas SI-ACR 6710 (Starting-Isolation, Automatic Charging Relay)


and a couple of Blue Seas 2127 HD bus bars for the house batteries, to mostly eliminate the wires directly to the battery posts.  (the ink pen is for size reference - this stuff is beefy!)


Reports & pictures later, after installation...
- Walt