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What is this Black Box?

September 03, 2015, 10:40:12 am

I hate to post a really dumb question, but what is this (black box pictured in the attached photo)?

Given my present preoccupation about taking care of our new batteries — we replaced house and chassis — I'd like to know everything in-line, in the system, and what it does?

Thanks for your patience, all!  We're learning as fast as we can.  Hope to do some of this in person at GrandVention.  <smile>

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Re: What is this Black Box?

Reply #1 – September 03, 2015, 10:42:40 am

Obviously a battery isolator.  Must be an add on by P O as I have never seen this as OEM.  Try a google search, maybe you can get more in fo.  If it is working you might consider leaving it alone.
Do you also have a Device with three posts on it and heat sink fins located just in front of the LR wheel along with a pair of relays ? That is what the OEM Isolator is and where it is usually located.
Gary B

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Reply #2 – September 03, 2015, 11:32:05 am

Gary, I think (looking at the picture) that the isolator is right below the "Black Box"
JohnH

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Reply #3 – September 03, 2015, 11:46:14 am

Start your research here:
AOPEC Automotive Electronics - Products

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Reply #4 – September 03, 2015, 11:48:30 am

This may be the one.
http://www.aopec.cn/fac/en/htm-products/pro-show.asp?pro_id=20
I can't fathom any idea for this setup unless the PO simply installed as the old isolator quit and rather than rewire everything the PO just added this unit?

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Reply #5 – September 03, 2015, 11:55:11 am

Gary, John,

Thanks! I guess I should remember, "When in doubt, Google it."  This appears to be what is installed (minus the clear cover).  Thanks for the initial search Peter & Beth.  All I did was drill down to the model number.  http://www.aopec.cn/fac/en/htm-products/pro-show.asp?pro_id=21

Seeing that, however, I'm afraid I still have the question — "What is this?"  Sorry to be clueless on this and with thanks to you both (and anyone else who chimes in).  My memory of the long and good PDI the previous owner provided is that it is was installed to ensure the chassis batteries would always be able to start the coach (i.e., would draw off the house batteries, in the event chassis batteries went down, 120V pedestal was not available, and — I guess? — generator wouldn't run?).

Sorry to be so paranoid about taking care of the new batteries we installed, but they weren't inexpensive and I'm kind of working my way through the entire system, the inverter/charger dip switches, this "black box," and whatever else might threaten them. 

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Reply #6 – September 03, 2015, 12:06:26 pm

I have one on my coach, when engine is shut down, it allows house battery bank to charge start batteries
when voltage on house bank is above 12.8 v. Does not affect operation of regular isolator. It will disconnect if
house bank goes below 12.8v. Nice, because if house batteries are being charged, [either by solar, converter or
inverter/charger], start batteries are also charged. All solid state, no loss of voltage. or extra
battery draw.  AND  no need for dedicated charger for start batteries. Wire it and forget about it.

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Reply #7 – September 03, 2015, 12:08:34 pm

John, Your  right, was thrown by a different kind of isolator than I had seen in the past.
Gary B

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Reply #8 – September 03, 2015, 12:09:12 pm

There is already an OEM isolator that protects your start battery bank from being drawn down by the house battery bank. It is that large heat sink unit below the "black box". Unless someone has modified the system the (or you turn the "boost" switch (on the dash) on) the two battery banks are isolated from each other in such a way that the house side cannot draw current from the start side; and vice-versa.

It looks like someone has modified your system. Not necessarily a bad thing.

Out of the factory:

1. The engine alternator will charge both banks.

2. The generator will charge only the house bank.

3. Shore power (via the converter/charger) will charge only the house bank.

There are previous-owner installations of trickle-chargers for the start bank, solar panel charge controllers with a link to the start bank (normally solar panel systems only charge the house batteries), etc. This, as explained by jcus, is one of those.

The boost switch on the instrument panel pulls in a relay that connects the two banks together until you turn the switch off. However some owners have installed a "latching" relay that remains "energized" without drawing any electrical power and will keep the banks connected until it's "released". This looks like a niftier way of doing that.

Craig

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Reply #9 – September 03, 2015, 12:14:49 pm

That is similar to the yandina combiner I installed. Right now my alternator goes directly to the start batteries and the Yandina combiner then relays power to the house batteries from the alternator. It also allows the house charger to charge start batteries when parked. Anytime voltage is high, it combines the banks to allow charging. Much better than the old diode based isolator.

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Reply #10 – September 03, 2015, 12:27:38 pm

The trouble with removing the old isolator completely, is that the old 2 gauge wires on the isolator are often too big for convenient
connection to the new combiner. That size is necessary, because when boost switch is on, and engine is started, amp draw from both battery banks is very high. I put mine in parallel with isolator with 30 amp breaker in line. That way, isolator and big wiring handle starting duties, and small combiner and 8 or 10 gauge wiring handle charging duties when engine is off.

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Reply #11 – September 03, 2015, 03:08:39 pm

Richard..

I sent you the PDF owners guide for that unit.

Check your email.

Hans

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Reply #12 – September 03, 2015, 07:28:42 pm

This type of device is more properly called relay based Battery Bank COMBINER.
They use an electronic circuit board to measure voltage and combine banks when their preset voltage is reached and uses a lower preset voltage to stop combining.
Other battery combiner manufacturers use a user settable variable set points.  All of them have disadvantages and advantages when compared to diode based isolators.
We have tested several relay based combiners and find diode based better for our coach.

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Reply #13 – September 03, 2015, 10:35:21 pm

I use a similar product from BEP. It is a VSR (voltage sensing relay) and interconnects both sets of batteries for charging. It drops out of the circuit when the voltage parameters are too low thus keeping something from draining both sets of batteries.

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Reply #14 – September 03, 2015, 10:47:05 pm

Barry and Cindy,

Curious to what problems you had with combiner?

Jim

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Reply #15 – September 04, 2015, 08:55:20 pm

These are some of our battery bank combining options we tried going back several years, with latest first:

From one of the below links:

So we purchased, first a Magnum combiner, then BlueSea combiner. We ran each for several months. These smart combiners do not use diodes, so start battery was being charged at house battery voltage, which is a good thing. But because the smart part of the combiners have voltage sensing circuit boards to decide when to close & open relay they were disconnecting just under 13 volts, which did not charge our start battery during hot weather. So we were no better off than using simple diodes. We purchased Trik-L-Start and are back to doing fine again.

Magnum Inverter Install Accessories
Ultra TrikL-start install question.
Trickle charge and isolator options
Trik-L-Start start-battery charging combiner

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Reply #16 – September 04, 2015, 10:57:44 pm

Barry and Cindy,
Good info. Think I need to look at my start battery voltages in different situations.
Appreciate it.
Jim

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Reply #17 – September 05, 2015, 11:26:08 am

Thanks, everyone!  This has been really helpful.  Susan & I are sitting here this morning, "going to school" on your posts, as well as the battery specs for the new house and start batteries we installed, and our inverter manual.

Much appreciated!  This Forum is great thanks to all of you.

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