advice needed...2 bank battery system working as one?

[twisted23]

a little back ground, i have just installed all new batteries, 4 group 31 s for the house and a single group 24 for the reserve .start side.....both sides are being charged by the alternator through the origional charging wire still hooked in at the starter....as it was origionally...my problem is ......both sides feed the cabin lights, ( bat 1 and bat 2) on the origonal off -bat 1 -both-bat 2 switch.....i have not tried every system's switch as i am not sure they all work properly yet.....no combiner is being used....i was going to use the single battery for a backup only... why are both banks connected together and where do i begin to find the problem?
as i understand the cabin lights should only work on the house ( Bat 1) side of the battery contol switch. correct?
thanks

[Stu Jackson]

Why not read this recent topic, should answer all your questions. http://www.sailnet.com/forums/electr...endations.html

[DelmarRey]

If your alt. wire is going to the starter then things need to be changed.

Different group of batt's will charge at a different rates. So the 31s mixed with a 24 will over charge the 24 with the system all hook together.

If all the 31's are the same age, that is good to start with, but as they get older they will too charge at different rates, but hooking batts in parallel has been going on for a long time with good results so it should be OK. You'll just have to test each battery occasionally to make sure one hasn't pooped out on you. Hopefully you have a high amp alt.

You'll need to run your alt. wire to a splitter with a sense wire to ignite the alt., or a pair of combiners. One to each side of the battery switch of 1 & 2.

In the BOTH position the system will charge at the lowest battery rate to all the batteries.
So, it's not recommended to run in the BOTH position except to start a motor especially if it has a low battery.

Your house batteries should be the ones running the lights. Sometimes one may want to connect the night running lights to the motor battery depending on their night sailing habits.

Hope this make sense to you!

Here's an actual drawing; http://www.yandina.com/acrobats/C100Data.pdf or with an inboard motor http://www.yandina.com/acrobats/C400Data.pdf figure #1

[mitiempo]

twisted.
If you mean the cabin lights work when you select either 1 or 2 on the main switch that is normal. The bank you select is the one you are using for everything, which is pretty standard.
As far as the alt output going to the starter that too is common. I think every Catalina left the factory that way and many others as well. The starter is powered from the common output on the 1/2/both switch. Because this heavy wire is already there it is more economical to connect the alt to the starter and the starter's feed wire continues the charge current to the common on the 1/2/both switch. The battery bank(s) you select will be charged when the engine is running.

As Delmar posted above this is not ideal. There are 3 reasons I don't like this system.
1. Charging is controlled by you so the switch has to be on both to charge both banks. If you start on 2 and leave it there 1 will not get a charge.

2. If you forget to switch it off both when the engine is stopped you will drain both banks with house loads.

3. If someone inadvertently switches it to off while the engine is running or switches it through the off position the alternator diodes will probably be fried.

There is one reason many boats were wired this way - and some still are. It is the least expensive way to charge 2 battery banks. But it is a totally manual system and a mistake can be costly or inconvenient.

The better way is to do the following:

1. Take the alternator output off of the starter and run a new heavy gauge wire to the house bank positive - with a fuse near the battery bank.

2. Take the shorepower charger's output off the start battery and leave it only on the house battery positive - again fused near the battery. If you have solar panels or a wind gen the output also goes direct to the house bank.

3. Buy either an Echo Cjharge or an ACR (automatic charge relay) and wire it to the house +, start + and ground. For a single start battery I prefer the Echo Charge. It passes up to 15 amps to the start (aux) battery when a charge current is sensed and stops when the charge current is no longer present. At no time does it parallel the batteries.

What this does is change your 1/2/both switch to a "use" switch and not a charge switch. It still lets you decide which battery to use for any load but the charging is automatic.

The easiest way to use this system is to use the house bank for everything and keep the auxiliary battery for emergency use. When you arrive on the boat turn the switch to 1 (house I assume) and turn it to off when you leave. Engine starting is easily accomplished by the house bank.

And there is no chance of error.

[rikhall]

wrong post - sorry

[Maine Sail]

Originally Posted by DelmarRey

If your alt. wire is going to the starter then things need to be changed.

Actually this is the most commonly wired system as boats come from the factory. The alt jumps over the the starter post were it then picks up the wire that goes to the output post of the 1/2/BOTH/OFF switch. Charging can then be assigned to either 1, 2 or BOTH. While not an ideal way to wire an alt the biggest issue is HEF or human error factor.

Originally Posted by DelmarRey

Different group of batt's will charge at a different rates. So the 31s mixed with a 24 will over charge the 24 with the system all hook together.

Completely untrue when the batts are being charged. You might want to read the excellent explanation of why this can't and does not happen in the Yandina site you linked to.

Originally Posted by DelmarRey

You'll need to run your alt. wire to a splitter with a sense wire to ignite the alt., or a pair of combiners. One to each side of the battery switch of 1 & 2.

The better method these days is a bleed charger like an Echo Charger or an ACR/VSR (automatic combining relay / voltage sensitive relay) from the likes of Blue Seas or Yandina, others make them too. Diode splitters are a outdated technology.

Originally Posted by DelmarRey

In the BOTH position the system will charge at the lowest battery rate to all the batteries.

In the both position the batteries act as one bank and no battery can be over or under charged. Again, Yandina has a very good explanation of this.

Originally Posted by DelmarRey

So, it's not recommended to run in the BOTH position except to start a motor especially if it has a low battery.

Actually it is just the opposite. It is very unwise to combine a perfectly charged battery with a bank of dead ones as the combining is bleeding off precious cranking amps. Connectiing a small start battery to a masive house bank can literally leave it very whacked in short order. I have physically watched 45+ amps flowing out of a 70 Ah start battery when it was combined with a dead house bank of just three group 27 batts. With AGM batts this can even be worse.

My buddy Tom killed his AGM bank when he thought he had flipped of refrigeration before going home. When he got back to the boat he found his bank flat dead. He fired it up on the start battery using the BOTH feature. He then proceeded to snag a lobster pot about 100 yards from his mooring. During the untangling the motor was shut down with it still in the BOTH position. When he went to start the motor, click, click.. If he had simply switched to the good battery he would never have had this issue.

Originally Posted by DelmarRey

Your house batteries should be the ones running the lights.

Agreed. I suspect he's flipping the switch from 1 to 2 and seeing that both banks will power everything depending upon the position of the switch and this is exactly how a 1/2BOTH/OFF switch works.

Originally Posted by DelmarRey

Sometimes one may want to connect the night running lights to the motor battery depending on their night sailing habits.

With a proper charging system there should be no need as both banks will charge automatically behind the scenes. With the system he has now he'd need to use the BOTH feature to charge both banks unless he has something he did not fill us in on.

[twisted23]

I have read the other thread , several times...it did not answer or address the question i asked.. plus there are so many different opions there it is hard to sort out the truth.......
what i have ...4 new 160 amp hr each deep cycle flooded batteries in the house bank..a deep cell-cranking, marine size 24 in bank 2 ,for the reserve or start ,.the alternator is a new 105 amp..... the boat has the normal lights, radio,gauges, gps plotter..and refrig......my goal is too be able to stay out for a period of 5 -7 days without having to recharge the house bank.....
now, somewhere in that other thread i read that a combiner was not needed if the start battery was use as a reserve, and the normal starting was done on the main house bank.....meaning that the reserve battery would remain fully charged for the time period in question...up to 1 week....because of this i added the fourth #31 battery to the house bank ...putting the amp hours over 600 total .......that should be enough to meet my reguirements off shore.....and i can still use the alternator to charge if i need to.
.....it is my under standing the act of any switching the battery control while the alternator is charging ,can burn out the diodes in the alternator.... this being the reason for installing a combiner......no switching means no combiner needed??????
i do have a spare alternator on board.....smaller but a good spare...again my intent is to use the main house bank for normal starting......not the reserve bank.....
my main concern was the house lights were being powered by both battery banks ....depending on the position of the switch....in my mind that means the banks are connected somewhere...thus the reserve battery would not be able to remain fully charged......and be usless when it was needed...my reasoning was this .......only one battery hooked up...only house lights on that switch position ....hooked up start battery and now have house lights on both positions...the starter also engages in both positions now .....both banks are being charged, but i shut down and restarted the motor to switch and check the charging ..so i am not sure if they are both charging at the same time or not...that i will have to verify... my question still remains....why are the two banks not seperate? it seems that they are bleeding together some place.....and how can a combiner make any differance in this situation?......and ...if both battery banks can feed the house lights ,what stops them from all being drained at the same time?.....
sorry i dont see this clearly ....and dont want to find out the hard way
so please bear with me....thanks

[sailingdog]

Originally Posted by twisted23

I have read the other thread , several times...it did not answer or address the question i asked.. plus there are so many different opions there it is hard to sort out the truth.......
what i have ...4 new 160 amp hr each deep cycle flooded batteries in the house bank..a deep cell-cranking, marine size 24 in bank 2 ,for the reserve or start ,.the alternator is a new 105 amp..... the boat has the normal lights, radio,gauges, gps plotter..and refrig......my goal is too be able to stay out for a period of 5 -7 days without having to recharge the house bank.....

Your house bank is 640 amp-hours. I seriously doubt you're going to be able to stay out for 5-7 days without recharging, since it only has about 320 amp-hours of usable capacity. If your refrigeration is 12 VDC based, you're really not going to be able to go for more than two days, given the other loads you've mentioned.

You really need to install a good battery monitor and get an idea of what your actual daily electrical usage is. That will give you a baseline to figure out how large a battery bank and what kind of charging sources you need. This is often one of the best upgrades you can do for your boat's electrical system.

now, somewhere in that other thread i read that a combiner was not needed if the start battery was use as a reserve, and the normal starting was done on the main house bank.....meaning that the reserve battery would remain fully charged for the time period in question...up to 1 week....because of this i added the fourth #31 battery to the house bank ...putting the amp hours over 600 total .......that should be enough to meet my reguirements off shore.....and i can still use the alternator to charge if i need to.

You really need to have a combiner--either an ACR, DuoCharge or Echocharger--of some sort. Lead-acid batteries self-discharge, faster in warm weather, and keeping the reserve battery topped off is key to having it in good condition when you need it. The reason you need the combiner is so that you can keep the reserve battery charged without having to put the 1/2/Both switch in the BOTH position.

.....it is my under standing the act of any switching the battery control while the alternator is charging ,can burn out the diodes in the alternator.... this being the reason for installing a combiner......no switching means no combiner needed??????

No, this is only the case if you have a non-"Make before break" type switch or you rotate the switch through the OFF position. Almost all of the rotary type battery switches available today are make-before-break designs. Of course, what you really should do is connect the alternator DIRECTLY TO THE HOUSE BANK, and that prevents the problem of disconnecting it from the battery and blowing the diodes from ever occurring. All your charging sources--alternator, AC-shorepower charger, solar, and wind--should be connected to the house bank.

i do have a spare alternator on board.....smaller but a good spare...again my intent is to use the main house bank for normal starting......not the reserve bank.....
my main concern was the house lights were being powered by both battery banks ....depending on the position of the switch....in my mind that means the banks are connected somewhere...thus the reserve battery would not be able to remain fully charged......and be usless when it was needed...my reasoning was this .......only one battery hooked up...only house lights on that switch position ....hooked up start battery and now have house lights on both positions...the starter also engages in both positions now .....both banks are being charged, but i shut down and restarted the motor to switch and check the charging ..so i am not sure if they are both charging at the same time or not...that i will have to verify... my question still remains....why are the two banks not seperate? it seems that they are bleeding together some place.....and how can a combiner make any differance in this situation?......and ...if both battery banks can feed the house lights ,what stops them from all being drained at the same time?.....
sorry i dont see this clearly ....and dont want to find out the hard way
so please bear with me....thanks

If the 1/2/Both switch is wired properly, and the DC panel and starter are wired properly, then UNLESS THE SWITCH IS IN THE BOTH position, the house loads and starter are only going to be on the house bank.

[Maine Sail]

Originally Posted by twisted23

I have read the other thread , several times...it did not answer or address the question i asked.. plus there are so many different opions there it is hard to sort out the truth.......

There is no one "truth" it's lots of reading and then a decision as to which wiring design you prefer once you have a full understanding of the pluses & minuses of each system design.

Originally Posted by twisted23

what i have ...4 new 160 amp hr each deep cycle flooded batteries in the house bank..a deep cell-cranking, marine size 24 in bank 2 ,for the reserve or start ,

Please check your battery rating again. In many years of this type of stuff I have not seen a deep cycle group 31 with 160 Ah's. You may be mistaking RC or reserve capacity with amp hours. If your battery is not rated in Ah's with a "20 Hour Rating" then you may not even have deep cycle batteries. RC and Ah's are NOT the same thing. Most group 31's range from a low of about 100 Ah's to a high of about 125 Ah's.

Originally Posted by twisted23

.the alternator is a new 105 amp..... the boat has the normal lights, radio,gauges, gps plotter..and refrig......my goal is too be able to stay out for a period of 5 -7 days without having to recharge the house bank.....

Do you have a battery monitor or have you done an energy budget? Let's do some simple math.

The average 12V fridge uses roughly 40 & 80 Ah's/day/24 hours..

The life of batteries is directly proportional to the number of discharges as well as the DOD or depth of discharge.

Cycling the batteries to a 50% DOD is the generally accepted low you want to regularly discharge to. If you can keep your state of charge to 60% or 70% you're doing even better and your batteries will last longer and give a longer cycle life.

One other thing that is often overlooked, is that when away from shore power, and charging off an alternator, you will rarely get back to any more than 80-85% of capacity so your real usable Ah's from a 200 amp hour bank quickly become 80-85 amp hours of usable battery life before you hit 50% DOD..


Here's some math:

The generally accepted max discharge depth for deep cycle batts is 50% of the 20 hour rated Ah capacity.

If we use the West Marine/Deka group 31 as an example it has only 105 Ah's per battery. With four @ 105 Ah you will get a max of 210 Ah of usable capacity for four batteries in parallel before hitting the 50% threshold. BUT this is from a full charge after leaving the dock at 100% full.

Four Group 31's

105 X 4 = 420 Ah's (Based on WM Grp 31)

210 Ah's use @ a 50% DOD = 210 Ah's left

210 Ah - This is your usable capacity if you can guarantee a 100% charge every day.

If recharging while away from the dock, with an alternator, the best you can usually get back to is about 80% SOC due to battery acceptance.

80% SOC of a 420 Ah bank = 336 Ah's of usable capacity

336 Ah's (80%) - 210 Ah's (to a 50% SOC) = 126 usable Ah's while out cruising!

126 Ah's - This is your usable Ah capacity while away from the dock and only using the alternator to re-charge!

And you thought you started with a 600 Ah bank!!!!

An AB fridge alone can draw 5+/- amps. If you figure it runs for 50% of the 24 hour day, on our well insulated boat it often ran a lot more than 50%, you've burned about 60 Ah's with just the fridge or 47.6% of your total usable bank capacity while away from the dock using the 80% charge rule.

Keep in mid that is 47% of your total usable capacity burned up by just a fridge in just one 24 hour period!

Ideally you should do an energy budget to know what your other draws total. It seems that you can do perhaps a day and a half without charging at this point if you want to follow the 50% - 80% well accepted cruisers guideline.

As I mentioned before consider a battery monitor as it will tell you how efficient your fridge really is. Some fridges cycle as low as 25% and some as high as 80% of the time. That can be a big difference and could be a costly mistake if it is a high cycler vs. a low cycler. Add to that a mistake like figuring you have 600 Ah's vs. considerably less and you could severely shorten the life of your bank.

A Victron BMV-600 Battery Monitor (LINK) will be the best $158.10 you've spent..

Based on four very popular group 31's you certainly can run your fridge over night depending upon your other consumption needs. Other needs might include anchor light, cabin lights, plotter, radar, stereo, VHF, depth, wind speed, water pressure etc. etc. etc.. Going for multiple days, and I'm not even considering 5-7 days here, will lead to short battery life as the math above shows..

Originally Posted by twisted23

now, somewhere in that other thread i read that a combiner was not needed if the start battery was use as a reserve, and the normal starting was done on the main house bank.....meaning that the reserve battery would remain fully charged for the time period in question...up to 1 week....because of this i added the fourth #31 battery to the house bank ...putting the amp hours over 600 total .......that should be enough to meet my reguirements off shore.....and i can still use the alternator to charge if i need to.

You don't "need" a combiner or Echo but if off cruising it is a very good idea rather than using the BOTH function to re-charge both banks. If sailing off the dock everyday then a simple re-wire of the alt directly to the house bank is sufficient. Wet cell batts can lose up to 13% of capacity per month in self discharge and this is worse the warmer it gets so you'll want to charge the starter battery at least once or twice epr month if it is not actually being used.

It seems you are simply shooting from the hip on this rather than doing the actual calculations."putting the amp hours over 600 total .......that should be enough to meet my reguirements off shore"

You're planning to go off shore so I would suggest more critical calculations than "that should be enough"..

Originally Posted by twisted23

.....it is my under standing the act of any switching the battery control while the alternator is charging ,can burn out the diodes in the alternator.... this being the reason for installing a combiner......no switching means no combiner needed??????

No the switching does not fry the diodes unless the switch is a very old break-before-make design. All new switches are make-before-break and have been for a long while. The only thing that will fry diodes is passing through the OFF position with the motor running. It is the act of disconnecting the "load" or in this case the battery from the alternator that frys the diodes.

A combiner or Echo Charger will do absolutely NOTHING to prevent frying diodes. The re-wiring of the alternator directly to the house bank is one of the only ways to guarantee that the load will never be disconnected. Zap Stops generally only really work once. I have seen a number of examples where owners have installed them then fried the alternator on the second pass through OFF cause they killed the ZapStop on the first "ooops"...

Originally Posted by twisted23

i do have a spare alternator on board.....smaller but a good spare...again my intent is to use the main house bank for normal starting......not the reserve bank.....

This is fine but do get your calculations right or your bank will be a lot more depleted than you thought.

Originally Posted by twisted23

my main concern was the house lights were being powered by both battery banks ....depending on the position of the switch....in my mind that means the banks are connected somewhere...thus the reserve battery would not be able to remain fully charged......and be usless when it was needed...

With a 1/2/BOTH/OFF switch it designates where power comes from. It can either come from bank 1, bank 2 or a combination of BOTH banks. Your switch is acting just as it should. Switch to bank 2 and bank 2 now becomes your sole source of energy. Switch to bank 1 and it now becomes your sole source of energy. Switch to BOTH and both batteries are now feeding the system.

Disconnect bank 1 and turn the switch to bank 1 you should get no power. Now disconnect bank 2 and switch to bank 2 and you should get no power. Now reconnect bank 1 and switch to bank 1 and you should have power. Etc. etc.

Originally Posted by twisted23

my reasoning was this .......only one battery hooked up...only house lights on that switch position ....hooked up start battery and now have house lights on both positions...the starter also engages in both positions now .....

Yes that is how a 1/2/BOTH/OFF switch works. Do the test above to re-confirm. These switces have two input/source posts a #1 & #2 and ONE common output post for your starter and all your house loads. The switch position determines which bank will be connected to the OUTPUT post of the switch.

During charging the OUTPUT post or COMMON post of the switch is supplying your charge current. If #1 is selected bank #1 gets charged. If #2 is selected then #2 gets charged. If BOTH is selected then both banks get charged. This is how most builders wired it because it was cheap & dirty.

Originally Posted by twisted23

both banks are being charged, but i shut down and restarted the motor to switch and check the charging ..so i am not sure if they are both charging at the same time or not...that i will have to verify...

Select bank #1 start the motor. Use a volt meter on the battery post of bank #1. You should see 13+ volts on bank #1 and less than 13 volts on bank 2 or a different and lower voltage. Do the same for bank #2. If both banks are being charged then you have A) wired it wrong B) have a charge splitter or combienr installed that you don't know about.

Originally Posted by twisted23

my question still remains....why are the two banks not seperate? it seems that they are bleeding together some place.....

Read above....

Originally Posted by twisted23

and how can a combiner make any differance in this situation?......and ...if both battery banks can feed the house lights ,what stops them from all being drained at the same time?.....

The only way both banks can feed the system SIMULTANEOUSLY is in the BOTH position. If they are both feeding it then you've wired it wrong. Do the tests above..

Originally Posted by twisted23

sorry i dont see this clearly ....and dont want to find out the hard way
so please bear with me....thanks

You're asking the right questions but need to apply yourself and do some more reading to gain an understanding of BASIC marine wiring, switches etc. etc.

[Stu Jackson]

The key to these very long answers is this:

Get the alternator output OFF the C (common) post of the 1-2-B switch, and run it to your house bank.

Then the switch does not EVER decide which bank to charge. The echo charger or the ACR chargers the reserve bank when any charger source is present.

Brian's post about changing the 1-2-B switch to only determine OUTPUT of the bank to be used is the key to understanding this.

Another common misconception is this: there are three posts on the switch: 1, 2 and C, there are four positions: 1,2 B, Off. Get your head around this, too.

Why'd the factory do this? Read the link I provided in Reply #14 in the other topic.

These two topics have included just about every meaningful discussion about this subject that I've ever seen and Maine Sail and I and others have been working this concept for the past 13 years if not more.

I agree, do some more homework with the tremendous amount of information you have in front of you. Once you understand how the switch used to work when wired incorrectly by the factory, you'll begin to understand it. Believe me, you're not the first. Many of us have helped others, offline, with their electrical system designs for many years. It's tried and true, and it works.

Good luck.

Stu