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.
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.
.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..
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"
.....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"...
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.
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.
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.
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.
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?.....
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..
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.