Battery charging

[mjmercer19248]

I have an engine battery and 3 "running" batteries ganged together (parallel 12vdc, higer current capability).

My charger has multiple outputs. Can I connect one output to the engine battery and the other to the entire bank? or do I need to connect to each battery individually?

 

[Stu Jackson]

Your running batteries are called the house bank. When you gang batteries together each is called a "bank." You have a house bank and a start or reserve bank. One charger output to each bank, not individual batteries.

 

[Don S/V ILLusion]

yes, you can treat the 3 battery bank as one battery for that purpose

 

[rardiH36]

... I have an engine battery and 3 "running" batteries ganged together (parallel 12vdc, higer current capability).

You haven't given a complete description of your system such as size/type of the three batteries. Great that you have a separate engine starting battery, but my first thought when I read your message is why three batteries are all ganged together for just one house bank. Assuming that the batteries are something like group 27 deep cycle or dual purpose type, wouldn't two batteries as one bank cover your needs? Then the third as your house bank number #2 to switch over to in case the primary bank some how becomes depleted? I would be more comfortable anyway. In which case, one of your charger outputs to #1; another to #2 and the third to the engine battery.

 

[H33CRich]

I have an engine battery and 3 "running" batteries ganged together (parallel 12vdc, higer current capability).

My charger has multiple outputs. Can I connect one output to the engine battery and the other to the entire bank? or do I need to connect to each battery individually?

Depending on your charger, you can terminate the other leads at the charger and have only one charge line going to the bank. I recommend a Blue Sea ACR (Automatic Charge Relay - http://bluesea.com/category/2/productline/overview/387) so that when you are plugged in, you can charge both house and starting banks. Likewise, when you are running your engine, you can charge the house bank once the starting bank is topped off. They are reasonably prices (about $100).

 

[DianaOfBurlington]

Battery banks-- keep it simple, silly.

[quote Assuming that the batteries are something like group 27 deep cycle or dual purpose type, wouldn't two batteries as one bank cover your needs? Then the third as your house bank number #2 to switch over to in case the primary bank some how becomes depleted?[/quote]

Simpler is better, on so many levels. My cousin Lee and I just had this conversation the other day and both of us concurred that one single bank is the best way to go. This goes even for electric/hybrid propulsion drive-- just let everything but the generator (in your case the primary engine) crank off the single house bank. There is both more voltage (should you go to 24v or 48v) and more amperage available for all needs. The individual batteries of the bank are spared the deep depletion that contributes to their premature demise.

And you spare yourself the hassle of worrying about the varying charge states of all the separate banks-- for, unless you want to kill your batteries quickly, they should NEVER be ganged together for charging and discharging (they can only ever be charged and discharged separately).

I would leave the three house batteries wired together as one bank (keep the connecting cabling short!) and have only one separate battery with which to start the engine. A two-legged charging system is more than ample for this system. I cannot think of any reason you would want multiple house banks; every normal situation would benefit from having one big one.

 

[rardiH36]

-- for, unless you want to kill your batteries quickly, they should NEVER be ganged together for charging and discharging (they can only ever be charged and discharged separately).

I would leave the three house batteries wired together as one bank (keep the connecting cabling short!) and have only one separate battery with which to start the engine. A two-legged charging system is more than ample for this system. I cannot think of any reason you would want multiple house banks; every normal situation would benefit from having one big one.

Hello John:

Want to learn from the thread. But sorry I'm confused with the first and second paragraphs copied here from your post.

First one: "they (that would be the three batteries?) should NEVER be ganged together" for charging and discharging.

Second one: ".. all three house batteries should be wired together as one bank".

Maybe I haven't understood the difference between the terms ganged and wired?

Say if I come back to my boat that has not been on the AC charger a few days or weeks later than anticipated and find I've inadvertently left a bilge pump switch on the always on position and the refrigerator door was left open, and I find that the voltage on my three battery one house bank (which might have three several year old batteries no longer in prime condition) is only 9V. Or I am out on the longer cruise without AC charging and I didn't notice that the alternator had stopped charging the bank as normal. Recovery from that would take a while if ever. I'm thinking that I would like to have that third house battery even if it is only one Group 27 as the second bank backup still at healthy 12.7-12.8V to run the critical systems while everything else is shut down. Instead of having only the starting battery to get me through.

If I have separate house banks, I can always "gang/wire" them together with the off/1/2/both switch. But I still have the option to charge and deplete them independently. The original poster says that he has a multiple battery charger.

Can you give more description of your rational? I would like to understand as I've got two Group 27's. Each is wired independent to charge for solar, alternator or AC and independent to deplete for the DC demand unless I combine with the off/1/2/both switch. I also have an AGM battery for starting backup. It's a small one. CCA's are enough to start the engine. But not robust enough to sustain the DC demand for long as well. Since AGM's self-discharge at a fraction of the rate as a normal wet-cell lead acid, I solar top it off only for a few days every month. Before top-off, the voltage generally reads about 12.8-12.85V.

Should I combine the two Group 27's into one bank? My DC demand is low. I don't have a refrigerator, or AC. Never depleted any battery below about 12.5 volts. (Except when my previous batteries inherited from the PO which registered 10.5 volts when I took possession of the boat finally began to get worryingly dogdy four years later.) I really only day sail 99% of the time and depleting any battery is a long shot. So this topic is more for understanding than dire need.

Sorry for the doubt and questions. Thanks.

rardi

 

[H33CRich]

Another case for simplicity: http://www.vonwentzel.net/Battery/03.Banks/index.html

That is why I use an ACR. However, JCII's statement of never discharging/charging as a bank does not make sence and I don't buy it. Nigel Calder gives a very convincing argument for why "large bank of cells will always outperform the constituent batteries by themselves".

 

[Jim Legere]

There are as many different ways to wire a boat's batteries as there are ways to set up ground tackle (the subject of another thread here). I have a "house battery bank" of three Gp. 24 deep discharge lead acid batteries under the cabin sole. I have a single Gp. 27 deep discharge lead acid "engine starting battery" in the original starboard cockpit locker location. The "house battery bank" is in the "1" position on the battery switch and the "starting battery" is on the "2" position on the switch. I usually only use the "1" position for everything (starting, electronics, refridgeration, etc.) and the "2" position is the Gp. 27 for emergencies (like Rardi describes...). I do monitor the "2" battery voltage and occasionally charge it while motoring by flipping the battery switch to the "All" position. Not high tech perhaps, but it works for me and I get 5 to 7 years life from a set of 4 standard deep discharge lead acid batteries. BTW, while I have no issues combining different numbers and sizes of batteries of the same type (eg lead acid) for charging and discharging, I would not advocate mixing different types of batteries like AGM and lead acid.

 

[Maine Sail]

- for, unless you want to kill your batteries quickly, they should NEVER be ganged together for charging and discharging (they can only ever be charged and discharged separately).

Batteries can certainly be ganged together or paralleled for charging and the advice to "NEVER" gang them together during charging is simply incorrect. It is safe, efficient and easier to parallel during charging. You can also automate paralleling with an ACR/VSR (automatic combining relay or voltage sensitive relay) to make it fully automated and require no human intervention to do so. It can also be done with a battery switch, though you run the risk of the HEF factor, or "Human Error Factor", and may forget to uncombine during discharge..

You do want to make sure the house & start banks are isolated during discharge so your thin plate reserve or starting battery is not cycled or so you would not potentially wind up with all the banks on-board depleted so deeply you could not start the motor..

Having one single, hard wired, large house bank is better and more efficient than having two separate house banks. This is so for many reasons, which would take another entire thread to explain things such as Peukert, acceptance, DOD, charge efficiency etc. etc.. Nigel Calder explains it well in his book, but there has also been much written about it here.

Perhaps the most simple and elegant solution is to run the charger as a single output to the house bank and then use an ACR/VSR to combine the banks and charge them both or use a B2B charger (battery to battery charger) such as an Echo Charger or Duo Charger to charge the start battery. The alternator, & solar or wind if added later, would do the same and use the same combiner or B2B charger to keep the start or reserve battery charged.

With many chargers you can also run one charger output to the house bank and one to the start bank, though they still only get one charge profile. Don't forget fuses within 7" of the + battery post in the chargers positive leads.

It would also help to know which charger the OP has. Some multi-voltage chargers require very specific wiring to work properly on a 12V bank and really may not be the best choice for large deep cycle 12V banks.

 

[rardiH36]

Maine Sail: Thanks for the explanations/insights. Still not sure if I want to wire my two independent G27's instead into one house bank of two batteries. Will have to read Nigel Calder's book and decide. As I included in my previous question post, I'm a 99% only day sailor with little typical demand on the batteries. So drawing down just one of them to damaging levels is probably not much different than another boat with two or three batteries in a bank, but fully decked out with AC and Frig and Television and Navigation and Computer and Microwave etc. And my starter battery is just a backup if I've killed both of the other batteries situation.

Again thanks. Always get me thinking.

 

[Stu Jackson]

Here's Calder's explanation:

IS IT BETTER TO HAVE ONE OR TWO BATTERY BANKS FOR HOUSE USE?
(By Nigel Calder - I DIDN’T write this!!!)

The popular arrangement of having two house banks alternated in use needs scrutiny before I go any further.

LIFE CYCLES: As we have seen, the life expectancy of a battery in cycling service is directly related to the depth to which it is discharged at each cycle - the greater the depth of discharge, the shorter the battery’s life.

This relationship between depth of discharge and battery life is NOT linear. As the depth of discharge increases, a battery’s life expectancy is disproportionately shortened. A given battery may cycle through 10% of its capacity 2,000 times, 50% of its capacity 300 times and 100% of its capacity around 100 times.

Let’s say, for arguments sake, that a boat has two 200-ah battery banks, alternated from day to day, with a daily load of 80 Ah. Each bank will be discharged by 40% (80 Ah of one of the two 200 Ah banks) of its capacity before being recharged. The batteries will fail after 380 cycles, which is 760 days (since each is used every other day). If the two banks had been wired in parallel, to make a single 400 Ah battery bank, this bank would have been discharged by 20% of capacity every day, with a life expectancy of 800 days, a 5% increase in life expectancy using exactly the same batteries!

But now let’s double the capacity of the batteries, so that the boat has either two 400 Ah banks, or a single 800 Ah bank, but with the same 80 Ah daily load. The two separate banks will be cycling through 20% of capacity every other day, resulting in a total life expectancy of 1,600 days. Doubling the size of the battery banks in relation to the load has produced a 210% increase in life expectancy. The single 800 Ah bank will be cycling through 10% of capacity every day, resulting in a life expectancy of 2,000 days - a 25% increase in life expectancy over the two (400 Ah) banks, and a 250% increase in life expectancy over the single 400 Ah battery bank!

There are two immediate conclusions to be drawn from these figures:

1. For a given total battery capacity, wiring the (house) batteries into a single high capacity bank, rather than having them divided into two alternating banks, will result in a longer overall life expectancy for the batteries.

2. All other things being equal, any increase in the overall capacity of a battery bank will produce a disproportionate increase in its life expectancy (through reducing the depth of discharge at each cycle).

FOR BATTERY LONGEVITY, A SINGLE LARGE (HOUSE) BANK, THE LARGER THE BETTER, IS PREFERABLE TO DIVIDED (HOUSE) BANKS.

 

[rardiH36]

Stu:

Thanks for the cut-and-paste of the Nigel Callder essay about more parallel batteries in a bank better than fewer. Yes, I understand. But I will maintain my existing arrangement. Since the amp demand on my boat is so low, I am unlikely to draw my one battery bank any further down than a high demand boat with say three batteries in a bank. So each battery on my boat will last a long time. And if I make a mistake on one bank (= one battery), I've got only one battery to replace.

rardi

 

[DianaOfBurlington]

JC = twit.

Sorry for the confusion-- I used the wrong term :cry:. A 'bank' is ganged together and charged/discharged as one. What I said made no sense the way it appeared.

My point was that two banks should never be discharged and charged as one, together (at the 'both' setting on the switch). An intelligent charger like the ProSport series will 'feel' the separate banks' needs and dole out to them appropriately. But just turning a switch in order to charge them all together is a mess waiting to happen. This is what those motorboaters do who would come into my WM store and ask about charging their deep-cycle house battery and their starting battery together with the switch set on 'both'. I don't know why those switches exist, and that is what Lee was saying. If you have two similar banks with similar batteries, why would you have the switch? Just put all the similar batteries (all the size-27 deep-cycle ones, for example) as one bank. If you have 8Ds too, call them another bank-- but you wouldn't have the switch with 'both' between those two banks, right? If they're starting batteries, keep them all as a separate bank and, again, don't rig them to a 'both' switch. But keeping similar banks separate just to have them 'in reserve' doesn't appear to have any benefit.

I am sorry I misused the term; because I get the feeling we're all pretty much on the same wave here otherwise.

I am a bubblehead sometimes when it counts the most. :dance:

 

[DianaOfBurlington]

Re: what Nigel Calder said--

Yes.

 

[DianaOfBurlington]

BTW if you have two engines (which mot many of us here do) or a generator and an engine, each should have it's own starting battery/bank independent of everything else. Then it will really depend on your charger to get it right!

 

[Maine Sail]

My point was that two banks should never be discharged and charged as one, together (at the 'both' setting on the switch).

This is untrue on the "charging" side of that statement.

An intelligent charger like the ProSport series will 'feel' the separate banks' needs and dole out to them appropriately.

Batteries combined will get charged the same way the ProSport does and the only difference is that the charger uses diodes on the output channels to prevet cross flow between banks,. With combined banks each battery will accept only the current it needs and the voltage across the new "combined" bank will be the same so "over charging" of one bank vs. the other is not possible.

This is a popular misconception people often have about batteries charging "combined"..

But just turning a switch in order to charge them all together is a mess waiting to happen.

As long as both banks are the same chemistry eg: AGM & AGM or WET & WET or GEL & GEL than there is absolutely no problem doing this. In fact companies such as Blue Sea, Victron, BEP, Yandina, Sterling Power, Newmar, ProMariner and many others offer automatic COMBINING relays that only combine during charging and then automatically disconnect when under discharge. They do exactly the same thing as the BOTH position.

Yandina invented this type of device and have sold over 20,000 of them all with an unconditional guarantee. They are one of the more reliable devices used on boat.s These devices are simple, eloquent and work all without the voltage drops associated with diode type splitters..

Yandina Automatic Battery Combiner (LINK)

Blue Sea Automatic Battery Combiner (LINK)

Victron Automatic Battery Combiner (LINK)

BEP Automatic Battery Combiner (LINK)

Sterling Power Battery Combiner (LINK)

ProMariner Battery Combiner (LINK)

Newmar Battery Combiner (LINK)

All of the above devices COMBINE batteries, just like the BOTH setting. The difference is they don't forget to un-combine during discharge, like a human can...

This is what those motorboaters do who would come into my WM store and ask about charging their deep-cycle house battery and their starting battery together with the switch set on 'both'. I don't know why those switches exist, and that is what Lee was saying. If you have two similar banks with similar batteries, why would you have the switch? Just put all the similar batteries (all the size-27 deep-cycle ones, for example) as one bank. If you have 8Ds too, call them another bank-- but you wouldn't have the switch with 'both' between those two banks, right?

Actually, not right..

If they're starting batteries, keep them all as a separate bank

Does not matter so long as the chemistry is the same and the charging voltages (float & absorption) are in the same range. You would never combine a GEL with anything because they can't ever take more than 14.1V but if your starter batt was also GEL then combining causes no ill effects.

and, again, don't rig them to a 'both' switch. But keeping similar banks separate just to have them 'in reserve' doesn't appear to have any benefit.

Actually there can be many benefits to a 1/2/BOTH switch. If properly used they are, and can be, an excellent switch and seeing as most boaters already have one why rip it out. There are as many ways to wire banks as there are boats and there are options. Combining batteries is but one of the many oiptions to charge multiple banks. Many builders, Hunter being one of them, ship from the factory with automated battery bank combining...

Musing Regarding The 1/2/BOTH Switch (LINK)

I am sorry I misused the term; because I get the feeling we're all pretty much on the same wave here otherwise.

I understood where you were going and addressed it in my first response. You have a common but misguided understanding of how batteries charge and this is why you incorrectly assume charging by combining is bad. It is not.

Combining batteries during charging is perfectly acceptable UNLESS the charging voltages of each battery are drastically differing. With wet/wet, gel/gel or agm/agm this won't be the case and a combiner or BOTH is a very good and efficient way to get both banks charged.

 

[DianaOfBurlington]

MaineSail--

My point is that I don't see any reason to have the 'both' setting on the switch at all. An intelligent battery charger metes out to each bank as it needs to; and separate types of batteries should never be ganged together for discharge (i.e., starting and deep-cycle). Calder-- and my cousin Lee-- both make the point that one big bank of house batteries (the deep-cycle ones) makes much more sense than having multiple separate banks of deep-cycle batteries on separate points of the battery switch. I think we've all agreed there is no necessity for that, and that the one big bank makes sense.

I think you misread my (probably badly-worded) statement about the separate types being charged together; I too was counting on a ProSport or other intelligent charger. I have a ProSport 12 that charges a pair of house batteries, as one bank, and one engine-starting battery. Both banks have separate on-off switches; they are not connected at all except via the (intelligent) charger. This is also the way we have wired Cherubini 44s for over 30 years-- no '1-Both-2-Off' switches there at all.

As for the motorboaters at West Marine, I can only go by what they tell me, that they do indeed charge (and discharge) different types of batteries wired together at the 'both' setting on the switch as a matter of 'convenience'. And, as at that time I was the guy who sold them their replacement batteries, I can attest that they were not, in generally, getting the full 3 years' worth of life that WM intends for them to get out of either their starting or deep-cycle batteries. This-- and only this-- is the reason WM, like others, came out with the 'dual-purpose' battery, which does neither job as well as either a starting or deep-cycle battery. But, you see, this is what their clientele call for, as this clientele misunderstand the fundamental points we've all been debating here and seek 'convenience' at the expense of enlightenment and their wallets.

 

[J Hunter]

I have the "simple" set up of 1 house bank (one deep cycle battery) and one emergency engine bank (one starting battery) switch always left on house bank, Yandina combiner across them both, which parallels them whenever it senses alternator voltage.

I have had limited issues and only two battery replacements over the 12 years since I've gone to this set up, but I remember seeing what I thought might be an issue that I thought I'd share and ask for comment on.

It was more than a year ago so I don't have perfect memory of it but I think I remember running down my house bank after being on the water for a couple long days with the radio and other stuff going and only limited motoring. When I looked at the voltmeter it was very low, like 10.8 I think (I know, for shame), and when I went to swap to my emergency bank I noticed the LED on the Yandina combiner (which is right next to my switch) was lit, even though the motor had been off for hours. I was lucky and the motor started that day, but I remember thinking that maybe I had exposed a scary feature of the combiner. Will the combiner parallel my batteries based on a certain differential of voltage between the two banks it's hooked to on a net difference basis or does it only combine when the high voltage sensed is both different and higher than 13 volts? Could it have paralleled a dying battery with my one remaining good one with no charging voltage present by design?

 

[J Hunter]

After reading the mild controversy between Main and JC, I'd have to say that Maine's technical explanations seem absolutely simple and correct from what I've read and experimented with. Also though in defending the utility of the "both" switch, Maine seems to be assuming as fact that the only time the switch will be in that position is when there is charging voltage present, do I have that right Maine?

While that may not make the "both" position totally useless (festidious use of it would allow one to keep an emergency starting bank charged and isolated while the house bank is being used without the extra cost of the combining relay) it does make it rather unforgiving of forgetting to un-combine when you turn off the motor, right Maine?

Once you add a combiner, the utility of the both position goes way down. Maybe when both banks are very low and you've got the best chance of cranking the motor with them both paralleled, but even that is questionable I think. The Yandina site at least when I read it years ago steered readers to separate on off switches for each bank (that set up with no combiner is just as easy to leave in the combined position if you are using them as manual charging combiner/ dis charge isolation switches BTW). I know I have a big note near my previously installed and still in use 1/2/both switch to NOT put it in the both position- which neighbors, brothers, and sons who may like the idea of meddling and going for more power have a tendency to want to use.