Battery Replacement/Rewire

[P69]

Ok, so I'm getting new batteries and have to redo some of the old wire. Both 4D batteries are shot, but the starter battery is still good.

Batteries will be four US Battery US2200 XC 6v batteries @ 232 AH.
Two of them wired in series, the two pair wired parallel.
Here is the diagram.

1. Is this going to work?
2. What am I missing
3. What meter do I need (current meter is analog volt meter)
I want to measure volts coming out of alternator and I don't know what I want to measure on the house bank, any recommendations on amp/volt/AH meters?
4. I suppose I need to have some kind of measure on the start battery to keep an eye on that. A meter that shows the voltage of the starter battery?

5. When wiring  alternator output directly to the house battery, does the wire have to be wired directly to the battery's positive terminal or can it go through a bus bar, as shown in diagram?  Same question for the echo charger lead to the house bank. Dashed lines indicate input cable going directly to the positive terminal, rather than through a bus bar.

The diagram is drawn in normal operating position, where the 1-both-2-off switch is on 1, connecting house bank with DC panel and ON/Off set for On so starter pulls from starter battery.

alternator is wired to house and echo charger sends excess to starter.
110volt battery charger connected directly to both banks  (starter and house).

If starter battery fails, I change it Both and use house bank to start engine.
If house bank fails, I change to 2 and use start for house (hope I don't do that accidentally!).

Thanks,
Craig

[PeteW]

Craig,
OMG, I don't know where to begin. You say your house batteries failed? I'm not surprised. But listen carefully.

My Rule#1.  Never permanently connect batteries in parallel. 1 dead 6 v house battery will guarantee 4 dead house batteries if not also fire with your schematic.

You actually show a system with 3 battery banks. House 1 (2 6v bats in series) and house 2 (the other 2 6 v bats in series) and battery 3 is the start battery. Note: do not connect the 6 volt batteries in parallel either as your schematic shows. Remove those links across the middle. Series connect batteries only.

Connect HB1 series pair and HB2 series pair (through separate fuse links) the 1,2 or both switch. The common goes to the DC panel as shown. When the boat is unattended select 1 or 2 only. Never leave the switch in both position unattended. Before selecting both always measure the voltage on HB1 and HB2 to ensure both are good.

Connect the start battery to the starter. You can use a series switch if you want but do fuse within 11" of the battery terminal.

Now you can install another switch I call the "jump start" switch that connects the start battery to the 1,2,both switch common (to the DC panel) This will allow the house batteries to be used for starting the motor if the start battery fails. Always leave this switch off unless you need it. (you will also need it to facilitate charging. Unless you go with the smart isolator described below)

Charging the 3 banks equally will be a constant problem. To only way to ensure a full charge on each bank is to select them one at a time to be connected to the alternator. The voltage drops are unpredictable so I can't say what will occur if you try to charge all 3 banks simultaneously. Based on voltage IR drops, one battery will always charge fuller than the others.

A better solution is to invest in a Sterling Pro split R zero drop- battery isolator. Alternator goes to one input and 3 high current charge wire  outputs go the each of the three banks. The splitter is zero voltage drop and smart so it will favor the battery that needs charging the most and then move on to the other 2 banks. Current will not flow between batteries though the isolator.

I am installing one right now in conjunction with a smart external regulator. The smart regulator has a sense wire that goes to the battery terminal and provides charge and float voltage per battery chemistry.

A 3 position switch with a wire to each bank will allow you to monitor all 3 battery voltages with a volt meter. This voltage alone will tell the state of each bank and if it is charging when the motor is running. A alternator current meter and shunt is a nice feature also. But I use my current meter shunt at the DC panel feed to show house drain in amps so I can calculate AH usage over time. Perhaps more useful.

With a little trickery a single pro split R can be used with the alternator and the shore power charger together.

I building out my boat with the system described above. The only other difference is my batteries are all AGM. No acid, fumes or explosive gas. AGMs will deep cycle forever it seems.

Pay equal attention to the return (Neg) cable. They carry the same current as the + cables.

Redo your schematic and I'll be happy to review it for you.    Pete W

[Dale Tanski]

Pete offers some excellent advice and well worth incorporating into the revised schematic. In respect to charging multiple battery banks, the Echo charger as shown manufactured by Xantrex is similar to the Sterling Pro but designed for a second battery only.  The Echo monitors the main (house) bank as they are being recharged either form the ships alternator, shore power charger, generator or solar system.  As the main batteries reach a level of around 80% of charge, the echo begins to transfer power to the 2nd connected battery, in your case the start battery.  As the main batteries reach a higher and higher level of charge the echo transfers more and more of the power to the start battery automatically.  The amperage that the Echo will transfer is limited to a maximum of 15 amps but that is more than sufficient for a top off charge to the start battery.

Having the Sterling or the Echo eliminates the requirement for a human to manually shift the available recharge power to the desired batteries and both units assure the most efficient method of recharging all the ships batteries.

While we are talking electrical systems and their associated components, I would like to reinforce that a ships electrical system design is only as good as its design, installation methods and the components that it is made up of.  Having used Blue Seas components many times in the past, I would like to suggest reviewing what they have to offer.  Even something as standard as the 1/2/both main switch, Blue Seas has several in different power connection configurations.  The last one I purchased even  offers a glow in the dark dial.  This simple but effective idea is a wonderfull thing when walking aboard in the dark of night.

One last thing... do not underestimate the importance of installing fusing at the batteries.

Dale

[P69]

I suspected I had to make some modifications.
Dale and Pete,  thanks for the recommendations.

1. Fuses: one on each positive battery cable, where else?
2. Battery charger output: To the Alt In on the Sterling SplitProR or to the pos terminal of each bank?
3. Sense wire from smart regulator (existing Aqualine regulator): Does it go to one or both house batteries or to the Sense terminal on the SplitProR, or somewhere else?

Here is the modified schematic.
Thanks again for your help.
Craig

[slokat]

Actually, it is better to wire the 4 six volt batteries they way you had them.

You have more usable Amp hrs available by combining 4 six volt batteries in a common bank (via parallel and series wiring) than you do by setting them up in 2 separate banks.

The one battery goes dead scenario is a red herring fluke, but easily overcome by switching one wire, until you buy a replacement.

I have a similar wiring/battery set up to yours, but the alternator charges the starter battery first then starts on the house bank.

Shore Power and the solar system charge the house bank first then top up the starter battery.

This is accomplished through an ACR that is bidirectional.

I use MRCB breakers instead of fuses at the battery connections.

And a Blue Sea Main Panel that switches both banks on, plus lets me combine them for starting if needed.

http://slokat.com/Wind%20Tamer/pics/panels1.jpg

[P69]

Well, I'm a little confused.

Slokat, I understand what you are saying about the combined bank and more usable amps. That is why I set up the first diagram.

Pete, if I understood you correctly, when I switch my 1-2-both-off switch to Both, I parallel the two banks and achieve the same as wiring the two series banks in parallel, creating a single bank of 464 AH. You implied that this is what should be done  when out on the boat, but when leaving the boat alone The switch should be switched to 1 or 2 to preserve one bank. 

Setting the charging aside for the moment and examining the "use" aspect of this, with Slokat's wiring, I get max AH all the time and don't have to worry about manually paralleling the batteries, but if one batteries fails, I can't unparallel the banks.

With Pete's recommendation, I have the advantage of paralleled banks and can manually unparallel in the event of battery failure; however, I have to remember to parallel them with the switch and to not parallel them unless both banks are at same charge level.

Is that the only differences in the two diagrams, from a "use" aspect?

[Dale Tanski]

Batteries are designed and rated to have a certain number of available amp hours.  Each manufacture publishes those numbers so the consumer can make an intelligent decision on the selection and purchase of such a battery.  Some publish them in such a way that hides or misleads the reality of their product but most are quite forth coming. 

One such number is CCA which stands for cold cranking amps.  This is the number of amps that a battery will provide over a 30 second period of time at 32 degrees F.  This number pertains more to automotive applications and starting your car on a cold morning.  Marine battery manufactures modify that number somewhat and refer to the MCA or marine cranking amps as most boats will not be used in 32 degree weather.  The higher the number the more power the battery will provide. The CCA and the MCA are most usefull in start battery applications.

Another number that is usefull when selecting a battery is the Amp-Hour rating.  This is the ratio of amps over a period of time that the battery will supply.  A battery that is rated at 100 AH's will provide 100 amps of power for a period of 1 hour or 1 amp for a period of 100 hours or any ratio in between.  This is a much more usable number for our house batteries.  If your total connected load is 10 amps (lights, autopilot etc.) and you have a 100 AH battery, that stuff will run satisfactorily for 10 hours. 

Same goes for recharging, sort of.  When the time comes to replace that energy, you would have to put back 100 amp hours either at 10 amps for 10 hours, 5 amps for 20 hours and so on.  Remember, amps are like dollars.  If you have 100 dollars and running a light bulb costs $1/hr you could run that light for 100 hours before you run out of power. 

I said all of this because if you have four batteries that each contained 100 amp hours a piece, their total combined amp hour rating would be 400. It matters not how they are connected, 4 x 100 = 400 period.  Parallel, series or the big circle route, the numbers are the numbers.

Now we will address the red herring issue.  Everything in this world has a tax associated with it. Cars do not roll forever when the engine is shut off. There is a tax between the tires and the road surface and the skin of the body and the surrounding air. This tax is known as friction.  Batteries have the same taxation going on internally.  Energy is lost from resistance of the materials that the battery is made of.  The electrolyte has a resistance and the sulfides you hear of are big tax collectors. The bottom line is all batteries will go dead just from their own internal resistance (taxation) all by themselves.  They all do and each does at it own rate of taxation with some faster than others.  If you connect several batteries together that internal taxation will drain the others at the same rate it drains itself.  The single weakest link of a chain limits the overall chains strength.  Same with batteries and it happens everyday, every hour, every second and it is not a fluke.  Like taxation it is a fact of life. 

Like taxation, the people that think ahead and learn form the past make better decisions and minimize their tax burdon.  Connecting batteries are much the same exercise.  Connect them in a way that the takers (entitlement types) benefit from and even the best most powerful battery will die a slow and agonizing death.  Connect them in a way that the takers are on their own and the best batteries live on long after the slackers are gone.  Sometimes you have to "loose" a cow to save the heard. Such is the case with batteries, redistribute the wealth and flush the country... um... I mean the lights.

Dale

[Jim S]

Phantom has a battery system similar to your diagram.  The house bank is four wet cell 6v batteries wired to create one 12 v unit .  The starter battery is a single wet cell 12v unit.  The house bank is wired to a off/1/both/2 battery switch.  The starter is wired to an on/off battery switch.  The house bank "1" setting goes to house loads and the "2" setting goes to the engine starter.  The starter battery switch goes to the engine starter.  The batteries are connected by a battery combiner that is bi-directional.  Placing the starter battery switch to "on" and setting the house switch to "both" will make the starter battery available to house loads.  The alternator connects to the house bank.

I chose to create a single large house bank to help prevent a frequent deep discharge potential.  I also realize the eventual problem with a single battery in the bank becoming a problem.  A good rule of thumb is keep all batteries the same type and replace them at the same time. 

I use digital voltmeters from Datel to monitor each battery bank.  I institute a charging cycle when the house bank shows a low of 12.2v.   

I would strongly recommend reading and digesting this topic in publications like Nigel Calder's "Mechanical and Electrical Manual" to see the various ways to create a battery system.

[PeteW]

Craig,
Your new schematic is much better IMO. To simplify further you could run the "jump start switch" directly to the lower start battery +12 bus. The engine shut off switch would connect directly to starter with one single cable.

I have been trying to get a look at the ABYC regs in section E-10 on storage devices. But its not available without $50 first. But in my search I could not find any expert (something I am not)with enough liability insurance perhaps to recommend connecting two 225 AH battery 12V banks in parallel. They all recommend the 1,2, both switch for mutilple battery systems on a boat.

I found this article from the Boston Whaler Co. that does a nice job of explaining the disadvantages of connecting battery banks in parallel.

http://continuouswave.com/whaler/reference/dualBattery.html

To paraphrase it says "connecting two batteries in parallel guarantees the battery bank will perform no better then the weaker of the two batteries in the bank." I believe that is similar to the lesson of Dale's analogy. Batteries in parallel do not share current equally meaning one of the 2 will supply the bulk of the load current.

Basically they give 2 times when you "switch" the banks in parallel. 1. to get max current for starting the motor and 2. to fast charge the banks simultaneously.

In regards to 1. (start current) I cannot image that you ever need 4,000 amps to start your motor. Having that much energy at your disposal is frightening. But you have this option with the schematic you have.  In regards to 2., The Pro R split (or blue Ocean) smart isolator will eliminate connecting batteries banks in parallel in order to charge.

The Boston Whaler article does say that failure of one of the parallel batteries in a parallel connection could result in a fire. They also warn against switching a good battery in parallel to a dead battery. This is where to volt meter should always be looked at first.

On my boat I did not use a 1,2 or both switch I used 3 SPST battery switches. It allows for all combinations. 

Pete

[P69]

Thanks Pete and Phantom
I'll follow that link and look it over and get a copy of Calder's book. It looks like I'll need that book.
I appreciate your info.

[slokat]

This link and my experience with house solar systems are why I use one combined bank.

http://www.smartgauge.co.uk/splitting.html

Batteries are more like sled dogs that are pulling Peukert's sled, you don't let two of the dogs ride the sled, while the other two pull.

Plus, it's pretty easy to tell if one is not pulling it's load...

[Dale Tanski]

How does one determine which individual battery in a combined bank of batteries is not pulling its load?

Dale

[PeteW]

Dale, You asked the right question. After 30 years designing electronics, the aspect of  serviceability and testability are critical parameters. There is only one answer to your question. You disconnect the parallel banks and evaluate each banks performance under load individually. Manually switching banks in and out makes your system test simple and routine.

I've also spent 30 years learning how things explode and catch fire. Disconnecting battery banks from each other when not in use is a safety measure. A 100 Amp fuse on your battery banks may not prevent a fire in your absence. The same smart battery isolator on the alternator can be used for charging/floating from your shore power charger or solar charger. So you're covered.

Look, I think we all get the concept that capacity (total AH) of batteries connected in parallel add. If you are going for 16 hours between charge cycles you may need all that capacity. There are 2 ways to provide that. You can run one bank for 8 hours and the other for 8 hours  or connect them in parallel and do nothing for 16 hours.  The 8 hours each procedure has the added advantage. Assuming both batteries started with the same charge, the one with the lower voltage after 8 hours would be the weaker battery.

The solar industry is making conventional storage battery technology obsolete . The marine industry should take notice. The hot setup for a house bank IMO would be 6  Rolles Surrette 2 volt single cell AGM batteries connected in series (satisfying rule #1) . The smallest 2V battery they offer is 590 AH (68 lbs.) . This gives you 590 AH at 12V in one battery.  Pete

[Dale Tanski]

Pete,
Actually, I knew the answer to the question.  The point being is that it is not that easy to tell which battery in a bank or offending cell in a battery is bad and why design a system that suffers accordingly.

Didn't the telephone company of old use mega banks of low voltage batteries for their backup systems? As I recall they lasted forever as well.

Dale

[slokat]

Did either of you read the article I linked?