Paralleling Battery Banks

[Noname]

OK. Now I understand. Having just viewed your profile page, I see you are a marine electrician. You didn't have a question. You were warning us about bad advice. Advice is worth what you pay for it, and for those of us DIYer's we are on our own. After all, it makes no sense to consult a forum to learn how do a triple bypass surgery, when we can just go to a professional. So why are we all on here trying to figure out how to charge a boat battery?? I have 15 or 20 marinas handy here that could do the job for me. Well, my boats 26 years old and my social security hasn't gone up for 2 years. On a positive note, I think your boat is a classic. Got any more pictures of it??

[Maine Sail]

Originally Posted by FlyingCloud1937

It doesn't matter the charge source, to properly charge, the charger needs to sense the bank its charging. It should be a smart charger, with bulk, absorption, and float to maintain the bat at optimum health, so as to achieve the designed life.

Lloyd

When you properly wire, many do not, and combine you have created one bank.. Andina Marie explained this quite well.

I have many customers with just the type of layout you describe, all boats are a compromise, and when wired properly the problems you suggest will happen just do not. I test these banks with multiple types of testers, capacitance, pulsed load, load and SG and they perform no worse than any other banks I work on when I see them wired appropriately.

The problem is that you can create intrabank imbalances by wiring the pos and neg connections to the bank incorrectly. Ideally they should come off opposite ends of the banks to balance the charge and discharge loads through the bank better than just connecting to one end or side. Most battery manufacturers shows this in their lit for wiring banks in parallel or series / parallel yet people still don't do it as they suggest.

Take one of my customers boat for example that has two T105's on port and two T105's on starboard. The pos supply cable is on the port side and the neg return is on starboard. Done this way, this is my customers exact layout, that is at 9+ years old it apparently works quite well... His bank is still going. Have not tested them yet this fall but in the spring they were in excellent shape and the cells SG was well balanced.

There is simply no excuse for putting batteries in an engine space, other than all boats are a compromise, but still that is just plain bad practice. The additional heat regardless of temp compensation will lead to shorter life, but that should not be blamed on a combiner.

Sometimes the engien room is the only place, I know, but it is still NOT a good spot for batteries. Neither is in a compartment next to a flag blue hull that sees sun. I have a customer with a J Boat and I have measured 134 degrees in his battery compartment behind the settee WITHOUT the batteries being charged and only the sun heating the hull. Ouch!!!

Our own boat had a Yandina Combiner 150 installed back in 1999/2000 at the beginning of a five year 24/7 live-aboard cruise. The batteries were nothing special and were deep cycle 12V wets. The alternator was left stock and dumb regulated (set point is 14.4V) and all that supplemented this was an 80W solar panel.

These batteries sustained all five years of the 24/7 95% on the hook cruise, and six total years by the time I bought the boat from my friend. They were still performing ok at year six, not bad for a $225.00 bank.

The start battery was just retired from starting my brothers Mako with a 225 HP outboard in August 2011. It had been combined daily for over six years via a combiner and charged with either solar or a dumb regulated alternator with a single voltage set point during those years. The batteries were kept topped up with distilled water, clean and properly wired but other than that nothing special. By the average boaters "use" those engine hours alone = 27 years of "average use" and I can't imagine what the solar charging "combined time" was but was a lot..

I consider nearly 11 years on a cheap deep cycle battery used as a reserve or start battery to be pretty darn good. While it had been in pretty miserable shape for the last few years it still started the Mako just fine and I wanted to see how long it would last so we kept pushing it. I equalized it once per year since taking ownership in 2006...

I have many, many more stories like this were combiners have been used. They are not a "new" product and solenoids have been used in this fashion for a long while just as the "ALL" position of battery switches has. All that has changed is they are now automatic based on voltage.

Our current bank is just nearing the end of year 5 and they are performing beautifully. Bank just put up 2486 CCA two days ago which is still well above what they are even rated for. Still dumb regulated, supplemented by solar and combined with a combining relay for charging.

Someone please tell my batteries they are dead because the combiner killed them..

[FlyingCloud1937]

Originally Posted by cal40john

Didn't think this is where your original post was going. To me you're making the case that if you're stuck in this scenario that you shouldn't use a smart charger and put up with the extra time charging your batteries in a constant voltage system.

Hunh....not

I disagree with your statement that if you don't have a smart charger you're killing your batteries. Sure you're getting the batteries charged faster, but unless you were close to getting the batteries charged under your old charging system it's unlikely you're going to completely charge the batteries with a smart charger.

Old charge technology both lovingly known as constant cookers, can do the job if you are using digital volt amp, meters, and in constant village..but I have never seen this happen

3 stage is far superior even if your goal isn't the shortest time of recharge, especially if they are setup w/temp comp. And the installer took the time to program the absorption time to meet the bat needs.

Or you could go the echo charge route.

John

I don't love the echo charger bc it's not a smart charger, but I do love the Balmar Digital Duo charge, it's selectable for bat type as well as programable to meet any bat needs, as well as temp compensated.

Lloyd

[Rick]

FlyingCloud is correct as to how a SINGLE battery charger with multiple outlets (claiming two or three battery charging) can overcharge one (or two) batteries when in the acceptance mode. If I encounter a multiple battery charger I use ONLY one output and then use programmable battery combiners to automatically connect other start-only-start batteries when the charger goes to float.

If one uses all AGM or gel-cell batteries for starting and house use then one can use Optima or FullRiver batteries without having to fear overcharging them when combined in the acceptance mode because those brands (and some others) will tolerate 15 Volts without charge accepting a damaging current when "full". When these batteries are full I have tested them to over 16V demonstrating less than 0.1 A per 100A-hr rating. In fact, this is one good indication that the batteries ARE full and recovered.

I have configured distributed batteries in parallel as a single bank successfully by making the parasitic cable and connector resistances insignificant compared to the internal resistance (the resistance when full, which is the lowest) of the battery at any location. This way the single charge source will source share an appropriate current to each remote battery. Have verified that each battery tracks both load sharing and source sharing current when being charged or discharged. For example, a 100A-hr battery in a bank will accept and deliver half of the current value that a 200A-hr battery in the bank located at a different location.

Make sense?
Rick

[FlyingCloud1937]

Originally Posted by Seaduction

OK. Now I understand. Having just viewed your profile page, I see you are a marine electrician. You didn't have a question. You were warning us about bad advice. Advice is worth what you pay for it, and for those of us DIYer's we are on our own. After all, it makes no sense to consult a forum to learn how do a triple bypass surgery, when we can just go to a professional. So why are we all on here trying to figure out how to charge a boat battery?? I have 15 or 20 marinas handy here that could do the job for me. Well, my boats 26 years old and my social security hasn't gone up for 2 years. On a positive note, I think your boat is a classic. Got any more pictures of it??

Well I'm here to learn, as well as help.

Certainly not start arguments, but I read many topics that are far off point at maintaining bats well. Especially some of the suggested ways to wire parallel banks.

Lloyd

In The Yard 09

[cal40john]

Hmm, every single car on the road is destroying their batteries according to you.

John

Originally Posted by FlyingCloud1937

Hunh....not




Old charge technology both lovingly known as constant cookers, can do the job if you are using digital volt amp, meters, and in constant village..but I have never seen this happen

3 stage is far superior even if your goal isn't the shortest time of recharge, especially if they are setup w/temp comp. And the installer took the time to program the absorption time to meet the bat needs.





I don't love the echo charger bc it's not a smart charger, but I do love the Balmar Digital Duo charge, it's selectable for bat type as well as programable to meet any bat needs, as well as temp compensated.

Lloyd

[callmecrazy]

Originally Posted by FlyingCloud1937

Sorry all, For starting this topic, and not staying to participate, had to run to a job.

First lets talk about batteries. Most bats don't die of old age. Most bats are murdered long before their design useful life.

Anyone that maintains a battery bank, is a "BANK MANAGER"

But to be a Professional Bank Manger, you have to manage the bank right.

Number one cause of premature death is Sulfation, caused by chronic undercharging. Next cause is chronic overcharging, aka positive grid plate corrosion.

A battery can suffer from sulfation in one cell of a multi-cell battery, as well as suffer from one cell being overcharged, while all other cells appear to be normal.

Battery banks built as series, parallel and or series/parallel can also suffer single cell, as well as individual battery sulfation/corrosion. It's called cell balance, that's why we use a hydrometer to measure the health of a battery.

To proper charge a battery/bank you have to charge proper, which means the charge has to sense the battery it's charging, then apply the proper charge regime to the bank.

That means a proper controlled bulk charge, then a controlled absorption charge with proper votage, current and time, ending in float stage...if the battery remains out of service.

Lets take one example to which I'm talking about, we have battery bank 1 servicing the house loads, and battery bank 2 serving the starter loads. Typically these are two different types of batteries, as well as 2 different sizes, the house bank being heavily used 50% SOC, while the start bank is lightly used 95% SOC.

Both banks are isolated from each other, as they should be. You only have one charge source, and somebody convinces you to install one of the fancy new combiner relay/solenoids. It's job is to combine the banks when the bank with the charger reaches above a certain voltage say 13.2.

What do you think is going to happen....yes, the charger when turned on sensing the house bank is going to go into bulk charge mode as it should. Once the house bank reaches 13.3 volts, it's going to parallel the much smaller bank that already is at 95% SOC, and overcharge it, until at some point the charger thinks that the house bank is charged.

But really happens in time, is it confuses the charger into thinking that the house bank is already at absorption when its not, cut back on the bulk, and time out on the absorption phase and leave the house bank under charged, while it overcharged the start bank.

This is one issue I find on a regular basis.

Lloyd

The charger I have (which isn't all that smart), prevents overcharging by knowing how long it should take to charge the bank. If the charger has been working too long, it shuts off or goes into maintenance mode. It's whole purpose is to prevent what you are describing, which also occurs when there's any load at all, on the bank that's being charged. This happens all day on most boats plugged into a dock, or with solar power.

[FlyingCloud1937]

Originally Posted by cal40john

Hmm, every single car on the road is destroying their batteries according to you.

John

There are a number of studies that show just that, I'll see if I can find the link to the last one I read. But it stated the average car bat lasted 3 years, some longer some shorter. Here's a link by MIT addressing the need for greater on-board power. http://student.fnu.ac.fj:82/Electric...alternator.pdf

But be sure a bat bank doing House loads is not the same as a car bat.

An alternator charging a car is designed, to replace the short amount of current used to start the auto, then it quickly goes into the mode of providing on-board power for the accessory loads. Its design use is not a battery charger, that's the by product

Lloyd

[Marqus]

Originally Posted by FlyingCloud1937

... if you take 2 identical cables say 5 feet in length, one runs in a straight line to the bats 2 in a cool space, the other has to go through the engine room and it's temps, to bats 1, but also has to make a couple or three 90 degree turns. Will in fact effect the charge and load in and out of each bank, and cause cell balance issues.
Lloyd

Must say I never thought about how a 90deg bend in a copper cable could affect it's DC resistance (can it?).

However, in respect of temperature affecting the cable run (not the battery itself), I did a small calculation on resistance for a 10ft AWG2 cable (5ft out plus 5ft return; rounding out a bit):

Resistance at temp 20C: 0.0015ohm
Resistance at temp 60C: 0.0017ohm

So, if we're running a 100A current through this 10ft cable, the voltage drops would be:

At 20C a drop of 150mV
At 60C a drop of 170mV

You wouldn't think that a 20mV differential could make such a big difference in battery survival, or would you?

By the way, pls verify my calcs because I've been known to (gulp) make mistakes.

[FlyingCloud1937]

Originally Posted by callmecrazy

The charger I have (which isn't all that smart), prevents overcharging by knowing how long it should take to charge the bank. If the charger has been working too long, it shuts off or goes into maintenance mode. It's whole purpose is to prevent what you are describing, which also occurs when there's any load at all, on the bank that's being charged. This happens all day on most boats plugged into a dock, or with solar power.

I'm not arguing, bc I don't know of what charger you speak....But how does it know how long to charge?

Lloyd

[FlyingCloud1937]

Originally Posted by Marqus

Must say I never thought about how a 90deg bend in a copper cable could affect it's DC resistance (can it?).

However, in respect of temperature affecting the cable run (not the battery itself), I did a small calculation on resistance for a 10ft AWG2 cable (5ft out plus 5ft return; rounding out a bit):

Resistance at temp 20C: 0.0015ohm
Resistance at temp 60C: 0.0017ohm

So, if we're running a 100A current through this 10ft cable, the voltage drops would be:

At 20C a drop of 150mV
At 60C a drop of 170mV

You wouldn't think that a 20mV differential could make such a big difference in battery survival, or would you?

By the way, pls verify my calcs because I've been known to (gulp) make mistakes.

Without checking your math..bc I'm not the teacher.

Bends in the cable will not impact low amperage to cable size, but when we are talking high amp loads, a 90 will create resistance, remember current flows, and like anything restrictions show up as heat. Take a look at any wire that has been over-amped, it will be very hard and brittle at any and all bends, especially tight bends

But it boils down to a time value, along with a compounding issue. If we are just taking trickle charge/discharge then balance may not be the issue, especially if we are talking currents passing through well oversized cables, but just as you suggested, we have ohms law, and associated losses to heat bc of R.

The higher the current, the bigger the issue...That's why some do an equalize cycle once a month...I don't go to that school either.

But choose EQ when the patient symptoms say so.

Lloyd

[callmecrazy]

Originally Posted by FlyingCloud1937

I'm not arguing, bc I don't know of what charger you speak....But how does it know how long to charge?

Lloyd

I have a cheap schumacher charger.

I don't know the mechanics of it, but I presume that as a 'smart' charger, it has some way of knowing the state of charge. Otherwise, it would never switch through the different charge phases... So it knows the state of charge is not consistent with charge rate, and it shuts off. I've watched it happen, by charging for a few hours with a small load on the bank. It's just knows that it can't 'complete' the charge process, by whatever means, and gives an error and stops charging.

I would assume most modern chargers have similar functionality.

[Maine Sail]

Originally Posted by callmecrazy

I have a cheap schumacher charger.

I don't know the mechanics of it, but I presume that as a 'smart' charger, it has some way of knowing the state of charge. Otherwise, it would never switch through the different charge phases... So it knows the state of charge is not consistent with charge rate, and it shuts off. I've watched it happen, by charging for a few hours with a small load on the bank. It's just knows that it can't 'complete' the charge process, by whatever means, and gives an error and stops charging.

I would assume most modern chargers have similar functionality.

Don't know which Schumacher but PLEASE do be careful with their stuff. I have had two customers in the last three years kill their banks over the winter by plugging them into the Schumacher "Ship n Shore" chargers.

They claim "smart" charging, suckered my customers in, but they will charge your batts at basically unregulated voltages at times going over 16 volts. The one I have on my bench, which Schumacher tech support says is working correctly, puts out 16.4V into a wet cell deep cycle battery and 15.2 volts into a GEL battery on the GEL setting.

These chargers are beyond just unsafe for the batteries they are flat out dangerous especially with the gassing they could create in a small space.. The particular customer that gave me the Schumacher ruined over $1400.00 worth of GEL batteries with it. He pressed GEL and trusted it was working correctly. I have tested three of the Ship n Shores now and they all do the same thing.. The older Schumachers were better but the new ones scare me.. As near as I can tell they have virtually no voltage regulation but I have not opened one up to see what's inside.?

[Jd1]

A couple points that have been forgotten in this discussion:
1) Just because something is called a 'smart charger' means nothing. You can get a 'smart charger' for a few dollars and you can pay hundreds. Do your research and don't take the label as gospel!
2) Don't mix and match batteries. Don't combine different makes/models/capacity/technology or ages. All of this will invariably result in a reduced life. You will find that even the same make/model varies over batches and if you want to do things really right you order the batteries for a bank specifically to be from the same batch.

[callmecrazy]

Originally Posted by Maine Sail

Don't know which Schumacher but PLEASE do be careful with their stuff. I have had two customers in the last three years kill their banks over the winter by plugging them into the Schumacher "Ship n Shore" chargers.

They claim "smart" charging, suckered my customers in, but they will charge your batts at basically unregulated voltages at times going over 16 volts. The one I have on my bench, which Schumacher tech support says is working correctly, puts out 16.4V into a wet cell deep cycle battery and 15.2 volts into a GEL battery on the GEL setting.

These chargers are beyond just unsafe for the batteries they are flat out dangerous especially with the gassing they could create in a small space.. The particular customer that gave me the Schumacher ruined over $1400.00 worth of GEL batteries with it. He pressed GEL and trusted it was working correctly. I have tested three of the Ship n Shores now and they all do the same thing.. The older Schumachers were better but the new ones scare me.. As near as I can tell they have virtually no voltage regulation but I have not opened one up to see what's inside.?

Those claims are ridiculous. These chargers are in no way 'unsafe' or dangerous. Maybe your customer didn't know how to push the little button that selects AGM,GEL,STD. It's not the smartest charger out there, but I'm quite sure the voltage is regulated... they do exactly what they're designed to do. They have sold millions chargers and have been in business for something like 50 years... show me one case (other than hearsay)? Just because they sell them at walmart doesn't mean it's going to break everything that touches it.



And I don't even like the charger....