1-2-Off vs 1-2-Off-Both switches

[Sunsetrider]

Originally Posted by Stu Jackson

Besides, your ACR should do both banks, so no need for a 2 lead charger.

No, the ACR is while running. The charger is while I have it plugged in dockside and home for the week. Both devices charge the batteries but under different conditions. I choose to trust the smart technology more than my bad memory.

[Dadrock33]

Please understand - the better MBSS (master battery selector switch) works as follows: "#1" (normally the starter batts), next is the "BOTH" selection(which combines both batt banks [assuming you have two]), #2 (again, normally the "house" bank) and "OFF". PLEASE DO NOT REVOLVE THE SWITCH THRU THE "OFF" SETTING WHILE THE ENGINE(S) IS RUNNING, you ruin the alternator. #1 and #2 cables can be exchanged to different batt banks if you want - the object is just to keep them separate at the switch (and other reasons too). If you're having an issue with charging either bank - simply install an ACR (automatic charging relay) and connect to the post for #1 and to the post for #2. Again, normally, you would want to always insure that the starting bank is fully charged; the ACR will then start charging the "house" batts when the voltage of the "start" bank reaches an appropriate level (some are settable, some aren't). It's as simple as it can be. You have the option of combining the batts if you need to or using them as separate entities but with the charging of each bank accomplished through the ACR and you don't have to do anything other than wire it up properly. Yes, before I get my hand slapped - I have left some available options out of this post because you need to read and hear more from others as well. I'm a firm believer in helping supply all the info I can and then let you take it from there. Ask any question you like and, if I can help, I will. Good luck and take care.

[Stu Jackson]

Originally Posted by Dadrock33

Please understand - the better MBSS (master battery selector switch) works as follows: "#1" (normally the starter batts), next is the "BOTH" selection(which combines both batt banks [assuming you have two]), #2 (again, normally the "house" bank) and "OFF". PLEASE DO NOT REVOLVE THE SWITCH THRU THE "OFF" SETTING WHILE THE ENGINE(S) IS RUNNING, you ruin the alternator.

But only if you are still using the switch as a charging selector as well as a use selector.

Get the alternator output off the switch to the house bank and you'll never ever have any issues with your alternator. You could even turn the darned switch OFF with no damage.

WADR, we've been writing this stuff for fifteen years and people still don't get it.

[john61ct]

Blue Seas has a couple switches - 9002 & 9004 - where turning Off, will first turn off the Alt's field current.

[Scott Berg]

After years of wiring boats all we use now are On/Off switches. One for each bank (starter batt to engine, house bank to house fuse block/panel, etc). Often we'll fit a charging relay from house to starter and parallel that with an on/off (paralleling) switch. Alternator is always connected to house bank in most cruising boat situations. We've never seen the need for a 'both' or multi position switch. Easy to explain to owner; it's on or off; parallel is automatic on charge and can be manually done' for starting assistance.

[44'cruisingcat]

Originally Posted by Bob666

Ok. I got young kids though.

Sent from my SGP511 using Cruisers Sailing Forum mobile app

If your kids are going to be playing with the battery selector, you need to lock it. If they switch it to "Off" while the motor is running you could seriously damage your alternator/regulator.

[mitiempo]

Originally Posted by Sunsetrider

No, the ACR is while running. The charger is while I have it plugged in dockside and home for the week. Both devices charge the batteries but under different conditions. I choose to trust the smart technology more than my bad memory.

An ACR wired between 2 battery banks operates on voltage - it does not care where the voltage comes from, alternator, shore power charger, or another source such as solar or a wind gen. They are fully automatic, connecting the banks when either battery bank reaches a specific charging voltage - 13+ depending on brand - and separating the banks when the charging stops and the voltage drops.

[Stu Jackson]

Originally Posted by 44'cruisingcat

If your kids are going to be playing with the battery selector, you need to lock it. If they switch it to "Off" while the motor is running you could seriously damage your alternator/regulator.

but...but...but

Originally Posted by Stu Jackson

But only if you are still using the switch as a charging selector as well as a use selector.

Get the alternator output off the switch to the house bank and you'll never ever have any issues with your alternator. You could even turn the darned switch OFF with no damage.

WADR, we've been writing this stuff for fifteen years and people still don't get it.

Please, please, please: learn how to do this and stop perpetuating this useless myth of alternator damage.

[undercutter]

The problem with VSR's is that the current rating for these devices must be at least as high as the potential loads on the battery banks that they may charge. Therefore if you run an VSR to your house and starter banks then they must be rated for at least as high as the highest potential loads. Usually this would be the starter on your engine but not always.

While we were in Phuket I had the electrical company at Boat Lagoon install a separate battery bank for the bow thruster as I did not want it running of the house bank. Primarily the reason is that the house batteries are not designed for high cranking loads which is what is required for a bow thruster. Also the cable run from the house bank to the thruster was over 25 feet one way so there was a lot of voltage drop over that distance doubled back to the house bank through the negative cable. They installed an ACR rated for 30 amps which fried the first time that I used the thruster with the genset running. The bow thruster can consume over 600 amps at 12 volts which it will try to draw from any available source. On top of that they also installed a physical blue sea switch at approximately 12' from the thruster interrupting the positive which of course resulted in a total run of 25' again.

In the end I had to rip out all the wiring that they installed and do it over again myself using a remote operated latching switch with the proper rating and installing a VSR with a capacity that met the load requirements.

The experts do not always know what they are doing!!!!!!

[bvander]

When we repowered we completely seperated engine and house systems, even going with two alternators, 120amp for house, 65 amp for start. Have just tow on-off switches and a seperate switch to allow emergancy parralleling.

[john61ct]

Originally Posted by undercutter

The problem with VSR's is that the current rating for these devices must be at least as high as the potential loads on the battery banks that they may charge. Therefore if you run an VSR to your house and starter banks then they must be rated for at least as high as the highest potential loads. Usually this would be the starter on your engine but not always.

No, this completely depends on your switch/wiring scheme.

And nothing to do with ACR/VCR specifically, but any combining tool.

The device must be able to handle the maximum load * that you will allow * across it.

Most such are not designed to handle cranking loads, for example the original one, Yandina from West Marine in 1993, is still very popular. Many thousands use devices like Echo Charger (15A) where the only current loads is the charging cycle.

If you want to be able to switch all loads to either bank, no need to use an ACR for that, combiners IMO should be about connecting for charging. I would suggest one of the Blue Sea switches, or if literally only for emergency cranking - which should almost never actually be required in a good setup - a set of jumper cables may suffice 8-)

Now some people may *want* to spend a lot more on a VSR that handles cranking loads (see short-spike peak capacity) or even one that is rated at 500A continuous.

I just want to point out it is a choice.

[Bob666]

I got a Sterling Alternator to Battery 80 A. The windlass will try to draw max 90 A from available sources= Max 50 A from its START output and amperage from the windlass battery = separate battery bank next to windlass connected with 35 mm2 cables.

About 15 m of 25 mm2 cables plus and minus, I e back and forth from START output to windlass battery. Cable will handle the load so ain't worried about that will fuse START output with 200 A fuse (for the cable).

Additionally the windlass and its battery is of course fused as well.

Cheers

Cheers

[44'cruisingcat]

Originally Posted by Stu Jackson

but...but...but



Please, please, please: learn how to do this and stop perpetuating this useless myth of alternator damage.

Yes, you can connect directly to the batteries. But I'm not assuming the OP's boat was wired this way.