Bad battery or bad charger?

[Maine Sail]

Originally Posted by MJH

With my Blue Sea Systems Automatic Charging Relay batteries are combined for charging until the starting battery is full and separated (thus full ready for starting), then the charging continues for the house battery until it is full.

This is not at all how an ACR works...

For banks that are differing sizes, as they are on cruising boats, Blue Sea recommends charging house first to minimize the issues of relay cycling.

[caleuche]

I didn't have much of a saying in the design of the setup I've got, but:

1. The house batteries charge the starter batteries, and never the other way around. To me that means the starter batteries have priority.

2. If the starter batteries need charge, they will have it (unless there's zero energy available on the boat, but that'd be entirely my fault, not the design's). The same cannot be said for the house batteries. To me that means the starter batteries have priority.

3. Because of the above, the starter batteries are always full. The home batteries instead are usually full only at the end of a sunny day. To me that means the starter batteries have priority.

Juan

Originally Posted by MJH

Start batteries have priority over house batteries. The ultimate test is which would you rather have working start or house?

~ ~ _/) ~ ~ MJH

[MJH]

Originally Posted by Maine Sail

This is not at all how an ACR works...

For banks that are differing sizes, as they are on cruising boats, Blue Sea recommends charging house first to minimize the issues of relay cycling.

I repost #7, the Blue Sea description below:

Blue Sea Systems words:
Manual Battery Management and ACR SubSystem

SI-ACR automatically combines batteries during charging, isolates batteries when discharging and when starting engines. The Dual Circuit Plus™ Battery Switch simplifies the switching of two batteries to OFF or ON while still providing battery isolation between the engine and auxiliary battery. The Combine function can be used to parallel the batteries in the event of a low engine battery.

I just got off the phone with a Blue Sea Tech. As stated above the ACR combines start and house banks after the stipulated time frame during charging. He said that the banks would work together to equalize the charge between them and this would mean that the more highly charged bank would give up some charge initially. After the stipulated time frame both banks would continue to register the same readings until both banks are fully charged. The banks are isolated when starting or discharging. Also, as stated above, this device "...simplifies the switching of two batteries [banks] to OFF or ON while still providing battery isolation..."; that's why I installed it...I never have to conduct this process as I did on my prior boat.

If you need more clarification call Blue Sea Systems, 360-738-8230.

~ ~ _/) ~ ~ MJH

[Sailmonkey]

Originally Posted by MJH

If you need more clarification call Blue Sea Systems, 360-738-8230.

~ ~ _/) ~ ~ MJH

Do you have any idea who you just told to call blue seas for ACR clarification?

[mitiempo]

Originally Posted by MJH

I repost #7, the Blue Sea description below:

Blue Sea Systems words:
Manual Battery Management and ACR SubSystem

SI-ACR automatically combines batteries during charging, isolates batteries when discharging and when starting engines. The Dual Circuit Plus™ Battery Switch simplifies the switching of two batteries to OFF or ON while still providing battery isolation between the engine and auxiliary battery. The Combine function can be used to parallel the batteries in the event of a low engine battery.

I just got off the phone with a Blue Sea Tech. As stated above the ACR combines start and house banks after the stipulated time frame during charging. He said that the banks would work together to equalize the charge between them and this would mean that the more highly charged bank would give up some charge initially. After the stipulated time frame both banks would continue to register the same readings until both banks are fully charged. The banks are isolated when starting or discharging. Also, as stated above, this device "...simplifies the switching of two batteries [banks] to OFF or ON while still providing battery isolation..."; that's why I installed it...I never have to conduct this process as I did on my prior boat.

If you need more clarification call Blue Sea Systems, 360-738-8230.

~ ~ _/) ~ ~ MJH

The above in incorrect as follows.

The set point on a Blue Seas SI ACR is 13.6 volts after 30 seconds and 13 volts for 90 seconds. This means that when the bank wired directly to the charge source reaches these voltages for the times stated it closes to combine the banks.

The house bank rarely charges the start battery. As long as the charge current is higher that the acceptance of the house bank and the small current that the start battery will accept the charge source - alternator or shore power charger - does the charging. I would think that a low output solar array could possible change this.

As posted by Maine above the charge sources should go directly to the larger bank, invariably the house bank, to avoid relay cycling. Relay cycling occurs when the start battery reaches combine voltage, ACR closes, house bank then accepts enough current to drop the voltage of the start battery below 12.75 volts for 30 seconds or 12.35 volts for 10 seconds. This repeats until the house bank slows down its acceptance.

It really doesn't make sense to run the large current the house needs through the start battery.

SI ACR details here https://www.bluesea.com/products/761...12_24V_DC_120A

[Marqus]

Originally Posted by mitiempo

The above in incorrect as follows.

The set point on a Blue Seas SI ACR is 13.6 volts after 30 seconds and 13 volts for 90 seconds. This means that when the bank wired directly to the charge source reaches these voltages for the times stated it closes to combine the banks.

.....snip

Great post Mitiempo, we needed the nitty gritty level here and you provided just that.

Now I'm being a bit lazy here not downloading the manual, but anyone here knows whether these Blue Seas set points (13.6v and 13.0v) are user adjustable ?
(Then I may buy one)

[john61ct]

They are not.

The devices that are, are not nearly as reliable.

[john61ct]

People keep writing

"Battery X is charged by Battery Y"

That is not what's happening.

The ACR /VSR closes / combines when voltage on either side reaches the setpoint condition.

That has little to do with a batt getting Full, or even "priority".

The relative resistance determines where the higher current flows, not "through" or "from" any battery. Since Starters can only accept a tiny current at any time, the current just flows around them, and flow to the House, which is the only one accepting high current, is limited by the VSR's ampacity.

With ML- 500A unit, hardly matters of course.

The vendors use words designed to appeal to, marketing to ignorant noobs, try to make very simple logic seem more sophisticated.

[john61ct]

MJH, you just need to accept the above, not just mine, but all there is a consensus there and by those know a lot more than me.

Maine Sail is as a god on this stuff, read his http://marinehowto.com and you will learn a lot.

[Maine Sail]

Originally Posted by MJH

I repost #7, the Blue Sea description below:

I just got off the phone with a Blue Sea Tech. As stated above the ACR combines start and house banks after the stipulated time frame

Absolutely true but this is not the operational manner you had described previously that I had quoted. Please understand I am not trying to pick on you at all, that is not my point, but there are lots of confusing theories about how an ACR works that can mislead folks. The statement I had quoted is one of many misunderstandings about how an ACR works that could mislead folks.

Originally Posted by MJH

during charging. He said that the banks would work together to equalize the charge between them and this would mean that the more highly charged bank would give up some charge initially.

The ACR can combine at either 13.0V (after 90 seconds) or 13.6V (after 30 seconds) with a bank at say 12.0V to 12.7V so there can be a very brief in-rush, (in-rush = a very, very short duration) to the lower bank.

Once the voltage of both banks is at parity, because the banks are now in parallel, the current can only flow into the batteries because the combine voltages are above the natural resting voltage of the bank. At this point each battery will simply take what it needs off the now parallel charge bus based on it's SOC and terminal voltage.

Originally Posted by MJH

After the stipulated time frame both banks would continue to register the same readings until both banks are fully charged.

"Readings" = Voltage

Because the banks are charging in parallel the voltage "readings" will essentially be equal on either bank. Blue Sea tech support was also correct on this point.

The only reason I am going through all of these points is to minimize confusion. Your statement is not uncommon and lots of folks think the ACR works like that but, it doesn't.

The start battery is not charged until full then separated and then the house bank is charged they are simply charged in parallel together so long as the bus voltage, measured at the "A" or "B" terminal (bi-sensing) remains above 12.75V for 30 seconds or 12.35V for 10 seconds. The ACR relays are also smart enough to detect a voltage trend upwards between 12.35V and 12.75V. If voltage is trending UP, and 12.35V is attained before 10 seconds, it will remain closed unless 30 seconds expires before it attains 12.75V. If wired incorrectly, for the application, the relay can still suffer from relay cycling despite the in-built logic to help minimize it..

Originally Posted by MJH

batteries are combined for charging until the starting battery is full and separated (thus full ready for starting), then the charging continues for the house battery until it is full

Originally Posted by MJH

The banks are isolated when starting or discharging.

So long as the owner has wired the SI (Start Isolation) feature, and many owners do not, this statement is also absolutely true. Start isolation is a very brief opening of the relay for as long as the start button is depressed. Once the starter is disengaged the relay picks up where it left off. For SI to work, the vessel needs to be wired for a dedicated starting bank. In other-words the SI feature would be of no use with a standard 1/2/BOTH where starting and house loads are shared by the bank selected..

Originally Posted by MJH

Also, as stated above, this device "...simplifies the switching of two batteries [banks] to OFF or ON while still providing battery isolation...";

What you are discussing is the "Add-A-Battery Kit", such as the Blue Sea 7650 that includes both an ACR and the Dual Circuit Plus battery switch. An ACR does not need the Dual Circuit Plus switch to work and can work with any dual bank system or charge source.

A draw back not mentioned with the DCP switch is that in the event of a bank failure, and these certainly can and do happen, your only option is to combine a perfectly good bank with a failed bank. Whenever I install a DCP switch on a cruising boat I also install two additional ON/OFF bank isolation switches so that either bank can be 100% isolated when the DCP is set to BOTH/COMBINE in an emergency situation.

I would also urge anyone reading this to take a few minutes to read the Blue Sea technical document on relay cycling. Most installers and DIY's miss this:

Blue Sea - Preventing Relay Cycling (LINK)

Think of an ACR/COMBINER/VSR as nothing more than an electronically voltage-change triggered BOTH/COMBINE switch and it will become much easier to understand.





This part of the installation instructions is also very often missed on cruising boats..

[john61ct]

Originally Posted by caleuche

An update to close this topic

The after party can be just as interesting as the main event!