Disabling the ACRs during battery charger operation

[DBBRanger]

Howard said in his post about his battery bank merge project (http://www.tugnuts.com/viewtopic.php?f=5&t=3665:

"... I will add a relay to disable the ACR when AC power is applied to the battery charger. The ProMariner has independent multi stage charge control for up to three battery banks, the ACR ties the banks together and eliminates this advantage..."

Additional information about that subject is here: (http://www.tugnuts.com/viewtopic.php?f=6&t=5439

I've decided to do that and thought I would post my method here in case others want to do the same. It's pretty basic wiring that anyone can do, although 110V is involved, so BE CAREFUL!

The ACR (Automatic Charge Relay, aka battery combiner) has a definite and noble job - it combines battery banks so that only one charge source (normally an alternator) is needed. If you instead attached each battery bank directly to the alternator, you would essentially have one battery bank since they would all be connected together. So the ACR's combine the battery banks together when the alternator is charging, but leaves them separate when the alternator is not charging. It does this by monitoring the voltages on each bank. The alternator is connected to one bank (the thruster bank in my case). When one bank is high, indicating it is getting charged, the ACR turns on and charges one other bank too. Since we generally have three banks, two ACRs are required. In my case, one ACR combines the thruster bank to the house bank and the other ACR combines the thruster bank to the engine bank. Ranger's wiring diagram says it is wired house to thruster and house to engine - but not mine.

So all that works well........except when using the boat battery charger. In that case, the charger increases the voltage on each bank separately (it's smart enough to do that internally without combining the banks together). That's good because the charge goes where it's needed. Unfortunately, the ACR's disable that feature by sensing the increased voltage on a bank and turns on ( i.e., combines) - negating the battery charger's independent charging feature.

So what can be done? The ACRs need to be disabled when the battery charger is in operation. Luckily there is an easy way to do that. Our ACRs have two features that are generally not used. One is an output that when connected to an LED will show the status of the combiners (which as Howard indicated has been wired incorrectly from the factory. Instead of connecting an LED, they connected 12V through a fuse to the LED pin output. In general, that doesn't hurt anything except that it did eventually blow out that feature on one of my ACRs but left the ACR's operation intact). The other feature generally not used is the start isolation feature. This is included in the product so that the combiner can be disabled during engine start when stray voltages may bother onboard electronics. It can be wired to the ignition so that when the starter is engaged, a voltage is sent to the ACR, disabling it - just what's needed for this project! In fact, the ACR manufacturer, Blue Seas, include in their battery chargers an output that is designed to be connected to the ACR exactly for this purpose. In our case, what is needed is a relay that is energized when the battery charger has 110V power that in turn sends a 12V signal to the ACRs' ignition isolation terminals which disables them.

My battery charger has basically an extension cord that the charger plugs into. That connection is covered with a plastic bag and cable tied to keep moisture out. It can be unplugged and then a device inserted that sends a signal to the ACR. What I did was to get male and female extension plugs from Home Depot, a relay from Radio Shack (#275-218), and a length of ABS pipe. I wired the male and female negatives from the plugs and one leg of the relay coil together and the two positives from the plugs wired to the other leg of the relay. The ground was wired directly from the male to the female connector. For the signal to the ACR, I used a 3 wire cable. At the ACR end I connected a female blade connector that fit the ACR ignition pin to each of two wires. On the 3rd wire, I connected a fuse holder and in turn, connected a round terminal to the other end of the fuse holder. The round terminal gets connected to a 12V buss bar - the house bus bar in my case. At the other end of the 3 wire cable, I connected the fuse wire to the common input of the relay (Pin #4 in my case) using a blade connector that fit the relay. The other two wires were connected to one blade connector that in turn was connected to the normally open pin (#6 in my case). The entire assembly fits into a 1 1/2" ABS (or PVC) pipe (if you get the correct sized plugs), with the control wire fed out through a hole in the pipe and with set screws holding the plugs in at either end. Now when the device is plugged into the power cord at one end and the battery charger at the other, the relay is energized when the battery charger is turned on and the contacts close, connecting 12 volts to the start isolation pin of the ACRs. As long as there is power to the battery charger, the ACRs are disabled.

Note that if you do connect an LED to the LED pin (Radio Shack #276-011 will work), the LEDs will flash when the ACRs are disabled, will be on steady when the batteries are combined or off when the batteries are not combined. I didn't think I would like that flashing all the time, especially since I mounted them on the battery meter panel where they would surely light up the whole cabin at night. So I put a 220K resistor in series with the LED in order to dim it considerably. If you do that, you may elect a smaller resistor or none at all for the brightest.

This is not a mandatory modification by any means, but it will save some charging time when using the battery charger powered by the Genset and may make your batteries last longer since they will not be overcharged while connected to shore power.

Let me know if anyone wants more details.

Doug

 

[HRowland]

Nice job Doug.

I still have not added a relay to my tug but it is on my list of late Winter projects before Spring launch.

Howard

 

[SGIDAVE]

The solution I used on my 21EC is not as elegant. I simply route the battery feed wires through a Blue Seas Dual circuit switch BEFORE they reach the ACR. Thus when the battery switch is OFF, they are 'isolated' from each other and charging from the 120VAC charger works well. But, I have just 2 banks...house and start.

/david

 

[Osprey]

Several posters have implied that the Promariner PronauticP series battery charger can provide automatic separate multi-stages to each output bank. That is, say one bank could be on the charge (bulk) phase while another on float. If this is the case, which voltage is being displayed by the charger? The manual states "...fully automatic and sequential multi-stage charging that provides electronically controlled charging, conditioning and maintenance of all batteries and or banks connected." To me this does not clearly indicate that there can be simultaneous bank to bank differences in voltage phase. I also note that the charging profile selected (to match the battery type(s)) being charged applies to all banks. So, no bank to bank applied voltage independence here.
There are true multi-output battery chargers available. These designs generally have a separate microprocessor for each bank and allow different profiles for each bank. i.e. they have complete bank to bank output independence. I rather think the PronauticP is a single microprocessor design that is not this capable.
Any comments or clarifications?

 

[DBBRanger]

Several posters have implied that the Promariner PronauticP series battery charger can provide automatic separate multi-stages to each output bank. That is, say one bank could be on the charge (bulk) phase while another on float. If this is the case, which voltage is being displayed by the charger? .........

There are true multi-output battery chargers available. These designs generally have a separate microprocessor for each bank and allow different profiles for each bank.

I didn't mean to imply that the charger applies SEPARATE multi-stage charging (ie Charging - Conditioning - Maintenance) phases. All banks are charged in the same phase. The charger does provide "Distributed-On Demand" charging which "automatically distribute(s) 100% of its available charging amps to any one battery or combination of batteries". I have a ProMarineer ProSport20Plus battery charger in my R25 which is a three bank charger. According to the manufacturer, this charger applies the same voltage to each bank (ie assumes the same phase for all banks) but provides only the current required by each battery bank. So it will not keep a fully charged battery in the maintenance phase of 13.4V if there is another bank that needs charging (which would be at the 14.6V level) - all banks get the same voltage applied. However, they are still independent in that they are not tied together as they would be if the ACR's were combining. The tech I talked to at ProMariner said he did not know of any charger that would allow the banks to be in different phases, however I was not impressed with his knowledge or attitude.

 

[Osprey]

DBBRanger, your post above confirms how I understood the operation of a Pronautic 3 bank, multi stage charger. It also confirms my view that defeating the action of the ACRs during charging may be doing more harm than good. I am particularly uncertain on which bank voltage triggers the charger to switch from bulk (constant I) mode to absorption (constant V) mode. If the charger waits until, say a significantly discharged pair of house batteries reaches the mode switch voltage threshold, then the other banks, say thruster and starter, which are often initially near full charge, will be subjected to the bulk voltage for an unnecessarily long time. I would expect gassing to occur in these batteries. If the charger mode switches when the highest bank voltage reaches the threshold, then the house would be slow to reach full capacity.
Further information can be found at www.chargingchargers.com. Try looking under the tutorial tab and the multi bank chargers tab. Note the Dual Pro PRO 15 amp Three Bank Battery Charger PS3 has true bank independence

 

[NorthernFocus]

...defeating the action of the ACRs during charging may be doing more harm than good. I am particularly uncertain on which bank voltage triggers the charger to switch from bulk (constant I) mode to absorption (constant V) mode. If the charger waits until, say a significantly discharged pair of house batteries reaches the mode switch voltage threshold, then the other banks, say thruster and starter, which are often initially near full charge, will be subjected to the bulk voltage for an unnecessarily long time. I would expect gassing to occur in these batteries...

I also have the ProSport20plus three bank charger. Without defeating the ACRs, gassing is exactly what occurs on all three banks. Apparently when all three banks are common it confuses the charger and causes it to continue supplying max amps in the "constant I" mode. However, as best as I can understand the design of the charger, if the banks are separated, even when in "constant I" mode, amps are regulated to each individual bank based on need. Therefore gassing should not occur on the batteries that are already charged if one bank is still low. So isolating the banks is necessary for he charger to work as designed. Of course that assumes that it does in fact function as advertised.

Until I get the time to install a fix to this design flaw in the electrical system, I'm manually managing battery condition and using an additional trickle charger rather than the on-board charger.

I've run across several design/installation problems with the electrical system. My boat is a 2008 so hopefully the factory has corrected most of the issues on newer boats.

 

[NorthernFocus]

...defeating the action of the ACRs during charging may be doing more harm than good. I am particularly uncertain on which bank voltage triggers the charger to switch from bulk (constant I) mode to absorption (constant V) mode. If the charger waits until, say a significantly discharged pair of house batteries reaches the mode switch voltage threshold, then the other banks, say thruster and starter, which are often initially near full charge, will be subjected to the bulk voltage for an unnecessarily long time. I would expect gassing to occur in these batteries....

After installing the signal to the ACRs to hold them open during charging, my ProSport20plus charger behaves exactly as stated above. The charger still stays in charge mode until the weakest bank comes up to full charge and provides enough amps to the fully charged banks to cause gassing. Presumably if left long enough the weakest bank would eventually reach a high enough state of charge for the charger to switch to float mode. But I haven't had the guts to wait long enough for that to happen. I did wait over an hour and that after I had pre-charged them individually. Still the charger would not switch modes. The only way I've seen it go into float is when I switch it on immediately after running the engine for a few minutes.

For now I guess it's manual battery management. Which makes the ACRs a PITA. Better off with the old tried and true switches that allow manual control.

 

[knotflying]

A question. Even though a charger may have the ability to charge separate banks, why not just hook up one charging lead to the ACR's and let them do the rest. Wouldn't this eliminate having to change all the electrical around?

 

[NorthernFocus]

A question. Even though a charger may have the ability to charge separate banks, why not just hook up one charging lead to the ACR's and let them do the rest. Wouldn't this eliminate having to change all the electrical around?

Tried that too. Even with a small six amp charger and starting with the batteries at full charge, when the ACRs close(i.e.connect banks)the charger stays maxed out and won't go into float so gassing occurs. One has to wonder what's going on when the engine is running. 🙁

 

[knotflying]

Interesting. I have not touched my configuration and I seem to be fine. I wonder if you have something else going on.

 

[NorthernFocus]

Interesting. I have not touched my configuration and I seem to be fine. I wonder if you have something else going on.

Most likely I'm just over-thinking the situation. I do have that propensity. I have a hard time trusting automation until I understand how/why it does what it does. Too many years working with it for a living I suppose.

The only reason I noticed that the batteries were off-gassing is because I was lying still in the bilge on a nice quiet morning looking at how to route wiring. I heard the batteries bubbling. Likely after a few hours they reach high enough charge and switch to float. But how long is too long? I've never been able to get an answer to that. All of the "experts" simply say that off-gassing is bad and don't go there.

Maybe there's no need to worry about it. Then again, historically I've gotten much longer battery life than most people report. So I have a hard time convincing myself to do things differently.

 

[knotflying]

I never really thought about it. I would assume if the situation was bad you would have to keep putting water in your cells. I check my cells every 6 months and add water. Probably 2.5 ounces in each cell. At 3 years I replace the batteries regardless of condition.

 

[LADYBUG TOO]

This is an interesting thread that has had some great ideas. Blue Sea Systems has several articles on their web page that makes the case for ACR's even with the multiple output chargers. Good reading but basically I am with Knotifying, check the cells and after three years chunk them and get new ones. Anything under $100 a piece is good enough for me. I am using Duracells from Batteries Plus. By the way, be sure to compare reserve capacities for your house batteries. I think for them reserve trumps cold crank amps. Usually I get about $15 for each old battery.

Pat
Ladybug, Too

 

[NorthernFocus]

I never really thought about it. I would assume if the situation was bad you would have to keep putting water in your cells. I check my cells every 6 months and add water. Probably 2.5 ounces in each cell. At 3 years I replace the batteries regardless of condition.

Yes that's what off-gassing does is to cook off the water. The bubbles are from H2O splitting into H and O. Unfortunately the prior owner installed "maintenance free" batteries so I can't maintain the water in them. Ergo the anality regarding gassing.

 

[knotflying]

There you go, a fine argument for good old fashioned flooded, inexpensive and seviceable.

 

[nzfisher]

I have no expertise whatsoever regarding batteries and charging systems. However, my system on a 2011 R25sc seems to be working with the gel batteries. My question is- "Is this something non engineers need to worry about? If so, what are the long term considerations? Obviously some bright people with considerable comprehension of these systems think it is worth writing about. I am looking to be made aware of problems before they might occur as I have discovered on many posts on this forum.

 

[knotflying]

Battery types are like religion, everyone has their own choices. As far as the charging system goes I would say it is pretty well engineered and if you are not an electrical efficinado then leave well enough alone. As far as batteries go, the most important thing is to make sure they stay charged. The second most important thing is to make sure they stay charged. After that it is a matter of choice and economics. The AGM's are great and can take some abuse as well as can be stored in any position. However at $275.00 a piece you want a good reason to buy them. Then from there you can go down to the old fashioned flooded of which I am a proponent. You can see when they need (distilled) water and replace them every three years for the break even point of hoping your AGM will last nine years. A simple technology that has been around for years.

I hope this helps with your question.

 

[NorthernFocus]

There you go, a fine argument for good old fashioned flooded, inexpensive and seviceable.

Indeed. Particularly on boats, simple is nearly always better in the long run.