ACR????

[adamsjstt]

Holy shysta i have spent about 3 hrs reading past post about the diode isolators and the acr and still dont understand the difference. Can someone simply explain the differences.

[chpthril]

ACR (Auto-Combiner Relay) or sometimes called and VSR (Voltage Sensing Relay) is just a large heavy-duty relay controlled by a small module that open/closes the relay contact based on the voltage level.

A Diode type Insulator is just a diode pack. A diode is nothing more then a 1-way electrical valve. It allows the charge from the alternator to go to each battery bank, but does not allow the current draw from off each bank to pull from the other battery bank.

[adamsjstt]

So if you use a ACR does your number 1 battery have to get a full charge before it swithes to the number 2 battery?

[ajholt7]

So if you use a ACR does your number 1 battery have to get a full charge before it swithes to the number 2 battery?

No, the ACR just has to see a certain voltage from the alternator to combine the batteries. I believe it is 12.8 volts. There is lots of good information on BlueSea's website.

[adamsjstt]

So the ACR automatically combines both batteries at a set voltage input from the alt, what about a isolator, Does a isolator ever combine both batteries?

[chpthril]

So the ACR automatically combines both batteries at a set voltage input from the alt, what about a isolator, Does a isolator ever combine both batteries?

Yes, both an ACR and a Diode type combine and isolate.

The ACR closes (combines the batteries) when the alternator is charging and opens (isolates) when battery voltage drops to a predetermined level. There are quite a few ACR's out there. Some are inexpensive and simple and some are pricey and the voltage thresholds are adjustable.

A diode is a 1-way electrical valve, so it always allows the charge from the battery to reach both battery banks, but will not let the load drawing from one bank draw from the other. The one down side of a diode type insulator is that there is a voltage drop across the diodes. In most cases, this is not an issue.

A multi-battery switch is a manual iso/combiner.

[philwsailz]

For a diode-based battery isolator, the voltage drop at charging is .7 volts. That doesn't seem like a lot but consider the ratio of .7/14.4 which is the ratio of diode-based voltage drop vs the IDEAL charging voltage. Your charging loss through a diode will be on average roughly 5%. If you have lots of load, tired wiring, bad connections, etc. the percentage can be a lot worse as voltage can be lower for the charging side of the house. The diode will ALWAYS eat .7 volts. Put 12 in and you only get 11.3 out...

The short factual statement is that with a diode-based battery isolator you will never fully charge your batteries...


Given the similarity of connection and operation, I would almost always recommend an ACR/VSR over a battery isolator.

Phil
Kicker

[Ewok]

Thanks for the explanations CHPthril and phill, I didn't realize with a diode the batteries will never get fully charged from the engine driven alternator. Another great reason to get an on-board battery charger.

[chpthril]

There is no arguing that having .7 volts less reaching the battery, IMPO, in most 2-battery systems with an average stereo system and used somewhat normally (on when running and some party-cove listening), that .7 will probably never be an issue.

On a typical 12V battery, 12.8 is fully charged and 12.0 is considered discharged. A typical alternator at idle speed will do at least 12.5, and 13.5-14.5 off idle and beyond. So, unless you only run at idle, the alternator will put out enough voltage to sufficiently top off the battery and keep up with an average load, even through a diode.

13.5
- .7
= 12.8

Now, here is another reason why dont believe that .7 voltage drop will be an issue. An alternator is not designed to actually recharge a discharged battery. Its job is to keep the battery(s) topped off and keep up with the typical electrical loads. Well, adding a 2K watt stereo is not a typical load So, if one has a big ACC battery bank ( 2 batteries or one big group 31) and a good size stereo, and they like to play it hard (loud and or for a long time with the engine off), then the battery will be heavily taxed. With or without a .7V drop across a diode, the alt will not bring that battery back up. Especially if you spend all day at the sandbar, then have a 15 minute run back to the dock at the end of the day.

So to sum it up, if you are building a system, go with a relay, no questions about. If you have a diode type already installed, then dont fret it unless you are building big system with a large dedicated battery bank. If this is the case, I would worry less about a .7 volt drop and more about not shocking the alternator when the engine is fired up and the alt is hit with a couple of big dead batteries. The flexibility of the relay type Iso's will let you turn off the relay that is placed between the batteries of the stereo bank so the alt only sees one dead battery upon starting. Once that battery recovers somewhat, the relay can be closed, combining the 2nd battery back with the 1st. This eases the load on the alt. At this point, an on-board charger is a must.

[adamsjstt]

There is no arguing that having .7 volts less reaching the battery, IMPO, in most 2-battery systems with an average stereo system and used somewhat normally (on when running and some party-cove listening), that .7 will probably never be an issue.

On a typical 12V battery, 12.8 is fully charged and 12.0 is considered discharged. A typical alternator at idle speed will do at least 12.5, and 13.5-14.5 off idle and beyond. So, unless you only run at idle, the alternator will put out enough voltage to sufficiently top off the battery and keep up with an average load, even through a diode.

13.5
- .7
= 12.8

Now, here is another reason why dont believe that .7 voltage drop will be an issue. An alternator is not designed to actually recharge a discharged battery. Its job is to keep the battery(s) topped off and keep up with the typical electrical loads. Well, adding a 2K watt stereo is not a typical load So, if one has a big ACC battery bank ( 2 batteries or one big group 31) and a good size stereo, and they like to play it hard (loud and or for a long time with the engine off), then the battery will be heavily taxed. With or without a .7V drop across a diode, the alt will not bring that battery back up. Especially if you spend all day at the sandbar, then have a 15 minute run back to the dock at the end of the day.

So to sum it up, if you are building a system, go with a relay, no questions about. If you have a diode type already installed, then dont fret it unless you are building big system with a large dedicated battery bank. If this is the case, I would worry less about a .7 volt drop and more about not shocking the alternator when the engine is fired up and the alt is hit with a couple of big dead batteries. The flexibility of the relay type Iso's will let you turn off the relay that is placed between the batteries of the stereo bank so the alt only sees one dead battery upon starting. Once that battery recovers somewhat, the relay can be closed, combining the 2nd battery back with the 1st. This eases the load on the alt. At this point, an on-board charger is a must.

Thanks that helps alot. Next question would be about the on board charger. How do you charge batteries with a on board charger without 120 volts ?Do you plug it in when you get the boat back in the garage? And is it hard wired to the batteries?

[ajholt7]

Thanks that helps alot. Next question would be about the on board charger. How do you charge batteries with a on board charger without 120 volts ?Do you plug it in when you get the boat back in the garage? And is it hard wired to the batteries?

Yes and yes

[dingleberry]

Thanks that helps alot. Next question would be about the on board charger. How do you charge batteries with a on board charger without 120 volts ?Do you plug it in when you get the boat back in the garage? And is it hard wired to the batteries?

Yes, you hardwire it to the batteries. When you park the boat for the night (at your house, storage unit, or slip), you plug the charger into an extention cord plugged into a 120V outlet. By the next morning, your batteries should be fully charged (depending on the level of depletion and the charger capacity).

[chpthril]

Thanks that helps alot. Next question would be about the on board charger. How do you charge batteries with a on board charger without 120 volts ?Do you plug it in when you get the boat back in the garage? And is it hard wired to the batteries?

Most marine on-board chargers just simply use a standard 120V receptacle. Either back in the garage or boat slip. I have heard of some people doing a solar charger for a trickle charger for a boat slip that does not have power.

I would recommend an on-board charger that will hard-wire to the batteries. This way the connections are always on, the charger is stowed away in a safe place and all you have to do is grab the plug and plug it up to your extension cord.

Guest, Pro Mariner, Ctek, Ship'n Shore are a few.

[jumphowhigh]

Or you go with a battery isolator that DOESN'T use diodes. I did an exhaustive search and came across this:

http://www.perfectswitch.com/home/blog/

Instead of .7 volt loss, .030 volt loss (thirty thousandths) It's MOSFET based instead of diode based. Far better. No heat sink needed. No moving parts like a relay. It just plain works (no affiliation, just a happy customer).


[QUOTE=chpthril;460348]There is no arguing that having .7 volts less reaching the battery, IMPO, in most 2-battery systems with an average stereo system and used somewhat normally (on when running and some party-cove listening), that .7 will probably never be an issue.

There is no arguing that having .7 volts less reaching the battery, IMPO, in most 2-battery systems with an average stereo system and used somewhat normally (on when running and some party-cove listening), that .7 will probably never be an issue.

On a typical 12V battery, 12.8 is fully charged and 12.0 is considered discharged. A typical alternator at idle speed will do at least 12.5, and 13.5-14.5 off idle and beyond. So, unless you only run at idle, the alternator will put out enough voltage to sufficiently top off the battery and keep up with an average load, even through a diode.

13.5
- .7
= 12.8

Now, here is another reason why dont believe that .7 voltage drop will be an issue. An alternator is not designed to actually recharge a discharged battery. Its job is to keep the battery(s) topped off and keep up with the typical electrical loads. Well, adding a 2K watt stereo is not a typical load So, if one has a big ACC battery bank ( 2 batteries or one big group 31) and a good size stereo, and they like to play it hard (loud and or for a long time with the engine off), then the battery will be heavily taxed. With or without a .7V drop across a diode, the alt will not bring that battery back up. Especially if you spend all day at the sandbar, then have a 15 minute run back to the dock at the end of the day.

So to sum it up, if you are building a system, go with a relay, no questions about. If you have a diode type already installed, then dont fret it unless you are building big system with a large dedicated battery bank. If this is the case, I would worry less about a .7 volt drop and more about not shocking the alternator when the engine is fired up and the alt is hit with a couple of big dead batteries. The flexibility of the relay type Iso's will let you turn off the relay that is placed between the batteries of the stereo bank so the alt only sees one dead battery upon starting. Once that battery recovers somewhat, the relay can be closed, combining the 2nd battery back with the 1st. This eases the load on the alt. At this point, an on-board charger is a must.

[adamsjstt]

Chpthril,
What do you think about the perfect switch? And correct me if I'm wrong but the acr combines both batteries so that you pull power from both and that would charge both( like wiring them parrell)at a set voltage from the alt.....and the diode type combines both just for charging and they never combine to supply power from both at the same time. ( they are always suppling power seperate from eachother)