Maintaining battery health

[Snotter]

My boat has 3 battery banks, all consisting of wet-cell batteries. Bank one has 2 4D batteries that are about 2 years old. Bank 2 has 3 group 27 deep-cycle batteries that are less than 1 year old. Bank 3 consists of a single 4D battery that is about 4 years old. The specific gravity measurements I've taken recently indicate all good cells. All three banks give me approximately 700 AH.

I live on my boat (Morgan OI 415) at a dock with shore power. The batteries are continuously charged through a Dolphin Battery Charger (60 amps, 3 banks, 3-stage charger controlled by a CPU). The battery charger is one year old. When selecting the wire sizes I consulted this forum and the appropriate wire-capacity and sizing tables. The batteries are left in parallel and the battery isolator is turned off. I use mostly 110 VAC lighting but my refrigeration runs off of 12V DC. I am in the process of putting in a 13.8 V power supply to run the refrigeration off of AC while tethered to the dock.

I've be watching my Link 10 battery monitor over the past year. Last year the Link 10 indicated a steady-state charge of 0.3 to 0.6 amps, which I attributed to internal battery resistance. However, this year the steady state charge has rised to ~1.2 amps.

Can some one tell me if these currents are normal and what is causing the current to go up? Is it sulfation? I never put my charger on equalize mode because I don't want to risk the high voltage. However, I am willing to disconect a bank at a time to do what is necessary. But, I would have to buy another charger with an equalization mode if I wanted to equalize the batteries because my existing battery charger is needed elsewhere. Would I be better off buying a nano pulser to hook up for a couple of weeks on one disconnected battery bank at a time? What do you all recommend?

 

[Bill Roosa]

Couple of questions Snotter

You say your batteries are charged in parallel and the isolator is turned off.???? If you wired the charger in parallel to all the batteries you don't really have an isolated setup. Draw a diagram and confirm for yourself.

If you have shore power and a battery charger you don't need a power supply. Just leave the battery charger on and it will keep the batteries charged as the reefer cycles on and off.

I'm assuming your steady state charge is with everything turned off and the batteries fully charged for some large number of hours on trickle charge. If you added some equipment or left equipment on it would show up in the "charging" as the charger is just supplying the average current to support it. A refer that draws 5 amps for 20 minutes has a 0.50 duty cycle (20 on, 20 off in 40 minutes) or 2.5 amps continuous as seen by the battery charger. You need to make sure the charger is not trying to support a piece of equipment to make an apples to apples comparison. It could be that your bilge pump is cycling more often due to a prop shaft gland that is just leaking a bit more (or a host of other things to include terminal corrosion)(99.44% of all electrical problems are corrosion related)

With all that said, a current flow of 1.2 amps on a 700 AH bank is only (1.2/700= 0.001) 0.001C which is well within the range of maintenance currents when on float charge.

The only way to tell if you have sulfidation is to put the individual batteries under a heavy load and note the voltage drop across the terminals with a volt meter. the inverter or an electric winch or windlass can put a 70+ amp load (0.1C) for 15 seconds is sufficient. I'd not use the engine starter as cranking it that long can damage it not to mention flood the exhaust. A good battery will show an initial rapid voltage drop (3-5 secs) then "flatten out" then only show a very slow drop (<0.1 volts/10 secs). If you see a rapid drop, a flat spot and then an increasingly faster voltage drop that bat needs attention, is not fully charged or is going to go bad soon. I can't give specific voltages to look for due to the lack of knowledge of temp, recent usage history, terminal corrosion, .... you are looking for the pattern of rapid drop then the bat holding up under the load. If it "can't take it" then that should tell you something.

 

[Snotter]

You say your batteries are charged in parallel and the isolator is turned off.???? If you wired the charger in parallel to all the batteries you don't really have an isolated setup.

This makes complete sense. You don't need an isolator when charging from a 3-bank charger. An isolator is only needed for charging from an alternator or a charger that supports only one bank. Moreover, since I always keep the battery switch(s) to all, I don't need to keep the coil of my combiner energized. When I go cruising and have to worry about keeping a starter battery charged, I'll start using the isolator.

I have no doubt my batteries are far from being kaput. My questions were designed to keep my batteries as healthy as possible. I don't understand how the steady-state charge is affected by sulfation (or whatever the correct term is) or if nano pulsers are just another form of snake oil. Also, I don't know if I should go through the hassle of equilizing my batteries on occassion.

 

[Bill Roosa]

A simple test if you need equlization

This assumes you have vented wet cells
Measure the voltage of each cell by sticking the volt meter probe into the electrolyte. Don't touch the plates. You can measure the "end" cells by touching one probe to the battery terminal over that cell the other probe to the electrolyte.
You should get very consistent cell voltages. If you get one cell of a single bat or one bat in a bank that reads low or high you need to equalize the bank.
This does not happen much BTW

Battery health is maintained by keeping them charged but not overcharging them, not discharging them deeply keeping the tops and terminals clean, and maintaining the fluid level in the cell. a good charger will do this automagically

 

[Bill Roosa]

battery switches

Hey Snotter
You must have a pretty weird setup on your battery switch. Most folks have a house bank and a starter bank.
If I understand you correctly you have 3 house banks and a starter battery. Not sure why you would want to divide the house bank up or why you would want to limit the alternator output to just the house or start with an isolator.
My take is put all the house batteries on one bank to maximize the AH and minimize the % discharged for the house batteries (for long life). Two house banks used separately will be discharged more deeply than one large bank. Use the battery switch to select where your charger/alternator supplies current (to direct the full output to the discharged bank) and to isolate the starter bat when on the hook overnight or sailing for more than a short while.
FWIW

 

[Snotter]

I do have a weird setup because I designed it ;-). The boat originally came with 2 banks connected through a single 0-1-2-B switch and a dedicated starter battery that could not be switched. When I rewired, I chose to add an on-off switch to the starter battery and feed it to the B side of the 0-1-2-B switch. I posted a diagram of my design last year at about this time. Roger Long was kind enough to add some modifications to my diagram before I committed it to reality.

Concerning the post about measuring the end cells: I've never heard of that being done. I am looking forward to trying it.

 

[John Nantz]

12V "Battery Minder" with desulfating

This is just to speak to one area: Desulfating, or, keeping the batteries desulfated.

We've got two banks of golf carts, and a start battery (all flooded types) and use a BatteryMINDer which has a patented desulfating system. It sends out pings at various frequencies to help keep the sulfate off of the plates. I've used one now for about two years.

http://www.batteryminders.com/batte...-8-Amp-Charger-Maintainer-Desulf-p-16133.html

Note: I'm not positive this is the one I've got but I think so. Just wanted to provide a link with a picture of what it looks like.

Our batteries are quite old and are due for replacement. Actually, a better world would be overdue. I'm guessing somewhere around 8 to 10 years without looking it up.

I noticed the AH capacity seemed to be declining so that's why I bought this in the hope of extending their life and seeing how it works. So far, so good. It seems to be working okay. At least the batteries are holding up but since we haven't used the boat much in the last couple years I can't say for sure.

Is this something like your "nano pulser"?

 

[Snotter]

Is this something like your "nano pulser"?

I think it is, though it isn't the one sold at the sbo store. The literature at sbo states it is only good for one bank. If my battery selector(s) were set for parallel, does anyone know if one pulser would accomodate 700 AHs of batteries? If I were to use one pulser on one bank at a time (disconnected from the house charger and any other circuits) would 2 weeks be sufficient time to desulfate a bank?

 

[Stu Jackson]

Also, I don't know if I should go through the hassle of equilizing my batteries on occassion.

www.amplepower.com, tech tab, download the Ample Power Primer. Answers most of your questions (unless I've linked you to it before and you've already read it).

 

[Seattle Scott]

Snotter, shouldn't you be monitoring each bank separatly to see what is going on, rather than monitor the banks when combined?

 

[Snotter]

Snotter, shouldn't you be monitoring each bank separatly to see what is going on, rather than monitor the banks when combined?

Since I am not cruising right now, and since I anchor out only occassionaly for an over-nighter, there is no reason to not leave my batteries in parallel. It is convenient to have one gauge displaying the state-of-charge for all the batteries. However, it would be nice having 3 monitors to watch how the banks degrade with time.

 

[Snotter]

I downloaded the primer from Ample Power and started reading it. It will be a while before I finish digesting it, but I think it will answer some of my questions.