the white paper proves what I said about chattering in post #54
While some poorly designed "combiners" can actually
chatter, because they have no delays, there is a difference between
relay cycling and
relay chattering. While it may seem like semantics
chattering and
cycling are actually different.
A
chattering relay can actually cause damage to the contacts. Relay
cycling will just cause slower charging and cycle the relay
on and
off more than is necessary, and more than you would see in a properly wired system. The current Blue Sea ACR's have built in delay logic that prevent "
chattering" and help to
minimize relay cycling.
Unfortunately far too many ACR's etc., on cruising boats are incorrectly installed by feeding the smaller starting bank first. This is made even worse if solar or wind with low charge current are used, and also fed to the start bank first. In a case like this the house bank may take a much longer time before it can get charged due to
relay cycling. The higher the available charge current is the less cycling will occur but on a cruising boat feeding start first is not a solid choice.
Unfortunately Blue Sea provides no instructions with most of their ACR's, for
properly wiring cruising boats, unless you really dig for it. They show wiring for banks of similar sizes so DIY's often wire an ACR incorrectly on a cruisng boat because Blue Sea has failed them in the instructions department.
These are the only two
boiler plate statements in the 7610SI instructions that suggest doing anything other than the very poor, for a cruising boat, wiring choices they show in the instructions. I tried to be realistic about the "instructions" and tried to match the font size they use in the instructions..
Open/Close Cycling
• If your electrical system is configured with a charging source that cannot supply the full load current being drawn from the receiving batteries, an open/close cycling process can occur. If this cycling continues, the second battery bank could eventually discharge even though a charge source is present.
and
"These installation diagrams show typical applications only. Your application may differ. For further information, please go to www.bluesea.com and navigate to Resources/Application Briefs and Technical Briefs."
I don't have time to hit all the points or confusion in this thread but perhaps can cover a few of them.
#1 The Blue Sea ACR's use time delay logic for both combine and un-combine to avoid "relay
chatter" but this may not always stop "relay cycling", especially if the ACR is installed
incorrectly for the application and the source charge current is low.
#2 The Blue Sea ACR also monitors
voltage trends. It does this to help minimize relay cycling. For example if battery voltage sensed at either the A or B terminal should be pulled down to 12.35V
or below the relay logic looks at the voltage trend to determine what action to take. If it does not attain 12.35V within 10 seconds it unparallels the banks or "opens" the relay. If it detects a voltage rise above 12.35V and attains 12.75V within 30 seconds it will remain closed and keep the batteries in parallel. If still going down, after 12.35V or lower is detected, it will then open up fairly rapidly (within 10 seconds). If voltage is trending up but it does not attain 12.75V within 30 seconds it will open.
#3 Combine voltages of the Blue Sea ACR are
above the full charge resting voltage of a 12V battery. With 13.0V or 13.6V applied to the battery terminals current can only flow INTO the banks not out of the banks.
The Blue Sea ACR will combine / parallel the banks at 13.0V for 90 seconds or 13.6V for 30 seconds. Any time the battery terminal voltage is
above the batteries SOC voltage,
current can only flow in one direction, and that is
into the battery.
The idea that a start battery or house battery can drain into one another, with an ACR, is not possible other than for 10 seconds or 30 seconds maximum. It takes voltage differentials to move current between batteries and the the energy that can move between the batteries in 10 seconds at 12.35V or 30 seconds at 12.75V in beyond minuscule.
#4 In almost every installation, on a cruising boat with disparate sized battery banks, charge sources current should feed the house bank first & not the start bank. This prevents relay cycling because it allows the larger house bank to attain the combine voltage before combining with the much smaller, and almost always nearly fully charged, start battery.
#5 Feeding house first also results in faster charging & better voltage sense accuracy of the house bank. When you avoid relay cycling, the house bank charges faster. With less voltage drop between the charge source and the house battery pos terminal, that comes from not sticking a relay, multiple terminals and two more fuses it is path, the charge performance of the house bank is improved.
Why continually pass 100A to 400A+ of charge current across a relay, multiple terminals and two fuses when you only need to pass a
few amps across the relay it when you feed
house first. By feeding
house first the relay is combining with a nearly fully charged start bank that may need only a few amps. The voltage drop when feeding
a few amps is minimal to almost none compared to forcing all that charge current through the relay, terminals and fuses and then into the deeply discharged house bank.
#6 Attaining the combine/parallel voltage, even for AGM batteries, should not take a long time provided you are actually charging these batteries
properly (see link below
). Low current solar and wind will take slightly longer to attain combine voltage parameters (13.0V for 90 seconds) but your start battery, unless something is wrong, should already most likely be at 97-99% SOC, so a little slower combine time, with alternative energy, still beats a batteries self discharge rate and is really no big deal. If your engine has a
honking preheater this takes the whole start battery charging design down another path entirely.
For what it is worth a number of years ago I ran an experiment with a 55HP diesel where the alternator was disabled, on purpose. This was done to figure out how many starts one could achieve off the single G-31 "
deep cycle" battery. After starting that motor 42 times, I grew tired and gave up. The next morning the resting voltage of the single G-31 "deep cycle", after starting the motor 42 times, had rebounded to a resting OCV of 12.57V..
How Fast Can an AGM Battery Be Charged (LINK)
Think about this snap shot if you use or are considering a battery combining relay for charge management and are concerned or have been scared off by one of the many myths surrounding these effective and reliable charge management devices.
The myth goes something like this: By using a battery combiner, on AGM batteries, and feeding the alternator or battery chargers directly to the house battery bank
first, “
It will leave your start battery under charged“.
If you are practicing good battery management, and have even the minimum suggested charge current for an AGM battery (Lifeline recommends a bare minimum of 20% of Ah capacity or .2C) this is simply a non-issue.
In just 2 minutes of charging, at .2C / 20% of Ah capacity beginning from 50% SOC, the AGM battery voltage is already at the “combine level” for a Blue Sea ACR. Once at 13.0V the relay has a delay of 90 seconds before combining/paralleling the banks. So, from 50% SOC with a .2C charge rate, it will take approx 3:30 for the relay to combine with the start battery and begin charging it. 90 seconds of this 3:30 is a built in timer delay in the ACR logic. In other words in just 2 minutes you're house bank is already at the combine/parallel level if charging at .2C with AGM batteries. Bump the charge current to .25 -.4C (where it really should be for AGM's) and the bank is attaining combine voltage almost instantly.
Battery voltage in bulk will rise pretty slowly from the low 13's on but to get to an ACR’s “
combine level” is relatively quick and easy, especially if you have your system set up properly. The Echo Charger, Duo Charger and numerous other DC to DC chargers also turn on at similar voltages and those devices require
all charge sources to be fed to the house bank in order to work properly.
#7 The current Blue Sea ACR's are "dual sensing" meaning they sense the voltage of either bank and can combine or un-combine based on either the "A" or "B" terminal voltages and delay logic.
Only some the earliest ACR's (circa early 2000's) such as the CL-Link 7600 or 9112 etc., long ago discontinued, could be set up for single bank or dual bank sensing. Some of the earliest models only had a delay on the combine side and would not combine until 13.6V for 30 seconds, and they opened at 12.6V with no or minimal delays. These older models should not be compared to the significantly improved later models such as the ML-ACR or the 7610SI etc.. Current relays all sense both sides, hence the "dual sensing".
#8 The Blue Sea ACR's
do not provide a different
charge profile to another bank. This is another ACR
myth and I don't know where it started? These devices are nothing more than an electronic paralleling switch that combine/parallel banks when charging voltages are present and un-combine when charging voltages are no longer present. The key word here is "parallel". Batteries in parallel are seeing the same voltages minus any slight voltage drop.
#9 Only the larger and more expensive Blue Sea ML-ACR (latching relay capable of 500A continuous) can be used as a
manually activated parallel switch. The smaller ACR's such as the 7610SI or the m-ACR can't be used for
manually paralleling banks. If you have a 7610SI or an m-ACR keep your manual paralleling battery switch.
#10 Yes I coined the term premature
floatulation 
for use in my seminars and classes. Students or DIY's seem to really understand what I mean by the term and it has been effective at driving the point home about how critical is is to
properly absorb batteries.. Politically correct? probably not...! Dropping to float too early, or prematurefloatulation, is a chronic issue in the charging industry of not adequately absorbing a battery before dropping to a float voltage.
