Two Banks used as one.

[Charlie]

Hello All:

I am about to purchase a new (to us) boat. It has 4-6volt batteries and a starting batterey. The boat has alot of electronics on it: radar, GPS, three different 12v refer/freezers, and a 110v washer dryer that can --I've been told -- run off the inverter. I've been told that their are 400 ah of power.

should I calculate all the power consumption ( I don't have all the info to do that so it will be a guess) or go with the more is better routine and put in another 400 ah of power as a second bank. From there I would leave the batterey switch on all and have an effective 800 ah system. By putting this system in place I would be able to use the middle 300 ah of the batteries and keep the charging system to its most effective charging reigem(sp?).

[Alan Wheeler]

I personly reckon you can never have too much battery reserve. My opinion is that the higher the charge you can maintain in your banks, the longer they last. So if your cycle rate on 400Ahrs allow the bank to discharge to 50% and the cycle rate of the 800Ahr means only a 30% discharge, then the banls are going to last longer.
The negatives are, you need a high capacity charger to cope with that load demand. Once batteries get some years of age on them, if you replace one, you shopuld replace them all. So the cost of replacement is a big hit to the pocket.
If you are adding 400Ahr of new battery banks to a set of rather old ones, you may run into problems with banks not equalizing correctly.

6 volt banks usually give the best amp/hr for the cubic foot. A second bank of 6 volt batteries should work well for you, but 400 amp/hrs is not allot of capacity for all of the systems you mentioned. Also keep in mind that the inverter is only 90% efficient or less. Also consider that the inverter draws even when it is not under load. Often as much as an amp, so you will be using more power than the basic numbers on the components. Electric motors also require 3 times their operating amperage to start up until they get up to speed. This includes refer compressors that start and stop numerous times each day.
Running both banks when the engine is running is fine, but it is easy to get false readings when running both banks with the engine off, and you have to be careful not to run your starting bank too low.

[btrayfors]

Charlie,

With the kind of load all those devices will put on your batteries, 400AH just isn't enough. That washer/dryer working off the inverter has gotta draw a mighty lot of juice, along with the 3 reefer/freezer units. I'd certainly add another 400AH bank.

Re: running them together as one big 800AH bank, this is indeed the preferred thing to do. HOWEVER, it's highly desirable to have all batteries in the bank be of the same type and manufacturing date if at all possible. Presumably, you'd be adding new batteries to an old battery setup...this isn't a good thing to do. You'd probably want to take an antacid, stop your hand from trembling over the checkbook, and buy 8 new batteries. (I know these feelings because I just bought 8 new T-105s for my boat; prices have gone up and are going up further very soon). Heaven forfend if you're thinking of AGMs...you might need a bank loan.

You will wanna keep the engine battery completely separate from the house bank. One easy way to keep it charged is to use a little device called an EchoCharger. It will put up to 15 amps into the starting battery whenever it senses a charge on the house batteries...from the engine alternator, an onboard battery charger, solar panels, generator, etc. Works like a charm and takes away any concern you might have about keeping the engine battery charged.

How do you plan to charge that humongous 800AH battery bank? You'll need a very hefty charger....over 100 amps at least. How about the engine's alternator? Big enough? Work thru a smart marine regulator?

Bill

[Charlie]

I guess I have to look at the whole system. It is hard b/c the boat is so far away. I think that the alternator is going to be the first step. I'll have to look into it somemore next time I go up to visit the boat.

Depends if the boat is at your departure point. Remember, even though you might not be able to use all of the toys right now, doesn't mean the boat can't travel.

[Rick]

First let us examine the philosophy of using a single house battery bank for everything, including engine and generator starting. (this discussion is the result of many hours and meetings with various companies interested in system engineering solutions applied to various markets),

Because battery monitors exist which are reasonably accurate and reliable to determine (for a given system) if sufficient energy remains at any time to be able to reasonably and reliably start a particular engine the economic impetus for single battery bank design is compelling when used in conjunction with an automatic generator start/stop device.

Because the chance for doing some kind of damage or create a safety problem at sea which is unrecoverable is high in the marine market it was determined that a single battery bank system is NOT acceptable in that case. It is acceptable in the RV markets when used in conjunction with an automatic load-shedding and warning system which is necessary for generator start/stop algorithms written to prevent starting during requisite "quiet" times as well as when the vehicle is parked inside a structure or in the atmosphere having elevated CO partial pressures.

Remote power applications are the best for such a battery system design.

Next consider a single battery bank for power in addition to a separate start-only start battery for either a generator or other prime mover having the ability to completely recover the battery bank losses. The additional battery could either be a dry-charged one or otherwise. Again, existing monitors (such as the Link 1000) are capable of measuring the start battery voltage (this parameter is sufficient to monitor for start-only battery use in temperatures ranging between zero and below 44 deg C).

Because a charge source can be brought "on line" at a moment's notice under the supervision of a capable observer safety is not a liability issue. The single battery bank provides the best economic, volumetric, and mass solution, especially considering that the start-only start battery can be chosen to provide a minimum reliable package for a given engine (CCA parameter equal to or greater than the stall current rating of the starter motor).

Now let's get to the myth-breaker. It is a myth that a single battery bank should only consist of similar batteries in age, type and model. After much conjecture along this line of thinking for years, it has been shown using multiple chains of batteries and monitors in various configurations not to be true, in general. In general, it is true tha the battery elements in a single series chain should be of the same age and battery type yet not necessarily model. They must, however, exhibit closely similar internal resistances and terminal voltage versus state of capacity and charge (yes, there is a difference).

As long as each series string in the bank (the bank consisting of multiple parallel elements, each parallel element having multiple cells in series) exhibits similar terminal volage versus state of charge (not necessarily state of capacity) then it matters NOT if they have different internal resistances, age, or model.

What happens, in practice, is that each series unit charge accepts and contributes as source current ratiometrically the same as is the ratio of the internal resistances ratioed, series element compared to other series elements. This might be referred to as "tracking". Each series element must track other series elements regarding their contribution of current versus state of charge or charge acceptance during charging. This DOES happen automatically more easily than one might imagine at first thought.

So, do not be so afraid to make more "complex" configurations of battery elements distributed around the boat in a manner convenient to you. You may have some golf-cart batteries and some 8-D as well as group 31 or 27 batteries. Yes, you may "feel" better if you have a monitor for each series string, or not. For sure, have at least one monitor on at least one string. If the strings are normally never separated (even thought you should provide some mechanical means of disconnecting each series string from the bank, such as using Anderson disconnects at the least) you actually only need to provide one monitor for one of the series strings, not necessarily one shunt for the combination of all.

I anticipate much debate over some of these points.
Regards,
Rick

[Charlie]

Hi Rick:

I was hoping that this thread would attract your attention. Upon reading it though I can see it is going to take me awhile to digest all this. There was a recent thread where a fellow said he checked each cell of his 6v batteries on a regular basis, allowing them 24 hours after charging to settle before checking. He would take the batteries that were not working well and rotate them out to a less critical place (his off grid cabin in the Ozarks). He mentioned that the ones he rotated out were not always the oldest batteries. Also there was another post by Hello Sailor who mentioned fork lift batteries which are sold by the individual cell. When I added these to threads together it seems to me that its like that old rule "Never cleat off a spinnaker sheet" I've steered to the kite for hours with the sheet cleated off. You just have to know what you are doing. I figure it must be the same with batteries. I had a truck battery that was 15 years old before it missed a start. The next one only lasted 18 months and the third one went 5 years. Some components must come together to make that magic 15 year old batterey perform. I am of the belief that if you monitor the individual cells you can mix and match batteries. Keeping to the same size and age is much easier(not to mention more profitable for the battery maker) but I can't see that if you have some batteries that aren't that old.

As for the monitoring and shunts. I'll have to digest that some more before I respond.

[Alan Wheeler]

Rick mate, who could debate with your knowledge. That is simply awesome. Thank-you

[btrayfors]

Rick,

You make some interesting points. Can you please provide any published references to support your contention that it really doesn't matter if you connect old and new batteries, different type and capacity batteries, etc.??

I'd be more likely to accept the theories posited IF we were talking about pulse chargers like the Iota. Batteries will accept what they will accept. Some pulse chargers, like the Iota, provide a relatively high voltage pulse for a short time (I think it's about 3 minutes), then lower the voltage. This is how they can be used with flooded, AGM, and gel batteries without fear of cooking or boiling the electrolyte.

One problem I'd see with combining old and new batteries has to do with the sensing circuits in the charger (i.e., most marine battery chargers). Old batteries which have lost a lot of their capacity due to 3rd stage lead sulphate crystalization on the plates exhibit a HIGHER than normal voltage early on in their charging. I think another post referred to this. It is therefore possible that the combined battery bank, with old and new batteries, would exhibit a higher voltage early in the charging stage which could result in the charger reducing or misinterpreting the state of charge. Net result would be (good) batteries never fully charged.

There are other technical concerns, but I've an open mind and would really like to see the evidence for your contentions.

Bill

[Rick]

Should you carefully read the wording you might surmise that much of what I have "revealed" has been from being a participant to various meetings, the minutes of which are not documented for public dissemenation. I have been very careful to not tread on any wording which might place me in a position of having revealed anything which might bring me to defend myself in a court of law, much of which I discuss is from my own work, albeit as an employee. As you might surmise, most companies are zealous in protecting their unpublished bodies of knowledge.

I CAN speak to the concepts of multiple battery bank performance without fear, however, since that body of work has been done in my own lab as an independent consultant following any contractual obligations with any particular company. Although I have not published such results, I can tell you that one result is that so-called "pulsed charging" does not appear to either equal or exceed the results of an ordinary "Amp-hour Law" charging regimen which I have discussed in previous threads. It DOES exceed what I call "ordinary" charging methods which do not reach published acceptance voltages recommended for various battery types and temperatures promulgated by the so-called "three-step charging" technology. Big deal. Keep in mind that the three-step charging regimen is a crude implementation of the Amp-hour law which has been published since 1924-1930 (Storage BAtteries by Vinal) and not practically realizeable until recently due to the development of the battery monitor and charger control (none of which has been implemeted commercially, one reason due to potential burn-out of incandescent bulbs when using the initial charge voltages which may be as high as 15.5V). Keep in mind that the Amp-hour law may be exceeded yet when adhered to guarantees no excessive gassing or temperature rise.

By the way, your reference to higher-than-normal terminal voltage of a battery which is sulphated is not due to some rare phenenomen it is because the battery exhibits itself as one of a much smaller capacity which develops a surface charge in addition to the normal cell voltage, that is all. Charger "sensing circuits" are all primitive unless they are interfaced to a true battery monitor (for example the newer Li-ion technology essentially demands a monitor in order to control a charger without causing potentially explosive results).

There is no such thing as so-called "third-stage sulphation" of a lead-acid battery. Such a term is much like what management training traveling sailes seminars use to re-invent terminology in order to pass a seminar off as being "new" when, in fact, little has been truly "discovered or invented" since the late 60's. When it comes to lead-acid battery technology little has been added since the '30's, in fact. To note such a documentation, virtually all of the definitive information has been compiled in textbooks written before the end of WW2 with later editions containing little more than what solid-state technology has facilitated towards the earlier knowledge base. Regarding sulphation: There are two types only, reversible sulphatation and irreversible, which is referred to as sulphatation (a little known term)..note the spelling difference.

As a final note voltage is not a valid indication of state of charge although most people assume that is so. Voltage is merely an indirect indicator, not a definitive one.

[btrayfors]

Lemme see if I understand this right.

Much of what you "have 'revealed' has been from being a participant to various meetings, the minutes of which are not documented for public dissemenation" because "most companies are zealous in protecting their unpublished bodies of knowledge."

You have to be "very careful to not tread on any wording which might place[you] in a position of having revealed anything which might bring [you] to defend [your]self in a court of law".

Additionally, much of what you discuss is the result of a "body of work [which] has been done in [your] own lab". It has not been published anywhere.

My friend, you may indeed be the world's greatest authority on flooded batteries and their care, and I don't doubt that someone pays you a bunch of money to consult on this or that, but you've gotta admit that based on your own statements above this isn't very convincing.

By the way, sulphatation is a PROCESS, not an end state. As in any process, it's quite legitimate to identify waypoints and stages. Three stages have been identified which are of practical significance to the cruising community:

1. stage one...begins immediately when batteries are left to sit without a charge....lead plates begin to lightly sulphate (you can see this if you shine a flashlight into the battery); normal charging causes the sulphate to dissipate back into solution;

2. stage two...small PbO2 crystals begin forming on the plates. Over time, these become resistant to breakup through normal charging, but "equalization", i.e., a high enough voltage applied for a time will cause them to break up either back into solution or drop to the bottom; and

3. stage three...PbO2 crystallization becomes more acute, bigger crystals form and become more closely attached to the lead plates; this stage is generally NOT reversable through normal charging or equalization. However, there is some evidence....and a whole slew of products coming to market and in use by, e.g., the Defense establishment, aircraft, trucking companies, etc......which purport to be able to break up these big crystals and cause them to return to solution through RF pulsing of the right timing, amplitude, and frequency. There are at least two published studies from recognized universities which tend to support these claims.

Note that the pulse charging mentioned above is not the same as pulse chargers I referred to in an earlier post. Automobile manufacturers have long tried to find ways to make electric cars more practical and efficient. The key to this, obviously, is to make batteries more capable of accepting a charge and discharging when needed. The bottom line of these studies has been the discovery that pulse charging is the most effective way to charge and maintain storage batteries.

OK, this is a bit off the main subject which was, I believe, whether or not to combine batteries of different type, age, condition, capacity, etc.

For the present, I'm gonna stick with conventional wisdom which says that this really ain't a good idea!

Bill

[btrayfors]

Oops...

Please substitute "PbSO4" for PbO2 in the above post. PbO2 is part of the problem, too, but that's for another day.

Sorry for typos.

Bill

[Alan Wheeler]

Bill, the reason why Rick has to be careful what he says, is that althjough he may have helped formulate many of the industries ideas of today, those ideas are intelectual property of the company and for him to state too much can get him in trouble.
The "3 stages" part I think is purely a misunderstanding of what you meant by three stages. It's not really 3 stages, that is three distinct forms of Sulfation. I think Rick thought you meant something different.
And finally, I think you need to do a search and go back over some of Rick's history before standing against this guy. You have no idea about him and can not judge him based on one topic. I realise you are also quite knowlegable. So am I, if I may be so bold, but I have also learn't a great deal from Rick and happy to take a back seat in this field of expertese. I don't believe you need to take a back seat, I think you can foot it with Rick just fine, but I think you need to know who you are dealing with here before you critisize.

Welcome by the way, I look forward to your posts and no one cares about typos. I'm one of the worst.

[btrayfors]

Hi, Wheels...

Thanks for the welcome, and for the advice re: Rick's earlier posts. I've seen some, and value his expertise. Didn't really mean to seem as combative as my post sounded (on re-reading); I was merely trying to elicit some "harder" data in the form of published data re: Rick's contention that you can happily mix and match battery sizes, types, etc. so long as batteries in each series string are of the same type/size/etc.

As a businessman myself dealing with intellectual property, I understand well the problem of proprietary info. But, we're not talking about rocket science here. You'd expect that by now someone....government, university, independent researcher, private company....would have published on this topic.

Re: the term, "stage", you're right...this can be misunderstood. Perhaps "degree" might be a better term. Sort of like "1st degree, 2nd degree, 3rd degree" burns. Three degrees of sulphation (or sulphatation if you prefer) could be described: (1) easily reversible through normal charging; (2) reversible through "equalization", but not normal charging; and (3) not reversible through "equalization" but perhaps reversible through RF pulse charging or other technique.

Anyway, great subject. Fun Board.

No harm meant, Rick. Look forward to your posts.

Bill