Tips on Choosing the Best Battery for Your Trawler

[marinetrader]

The most popular kind of battery in marine use today is the standard lead acid battery. Using an electrolyte consisting of sulphuric acid, these cells can store large amounts of electrical energy in a relatively small space. The energy is stored in lead grids that are inside the battery. The lead explains the massive weight of lead-acid batteries.

The battery selection is further spread along the lines of battery construction. Presently, there are three common battery technologies: Wet-cell, Gel, and AGM.

Wet Cells are the most common lead-acid battery-type in use today. They provide the most size and design options and are developed for many different uses. Wet-celled batteies have a grid of lead plates that is used with the acid. Since the grid is not supported except at the edges, flooded lead-acid batteries are mechanically the weakest batteries. Since the container is not sealed, great care has to be taken to ensure that the electrolyte does not come into contact with you (burns!) or seawater (chlorine gas!), or an explosion from the hydrogen produced. Batteries should always be stored in a spill-proof box.

Gel cell batteries use a thickened electrolyte . So if the container is broken, the cell will continue to perform as normal. Furthermore, the thickening agent prevents stratification by forestalling the movement of electrolyte. As gel cells are sealed and cannot be re-filled with electrolyte, controlling the rate of charge is very important or the battery will be finished in short order.

AGM or Absorbed Glass Mat batteries are the latest generation of batteries.* Instead of a gel, fiberglass mats hold the cells and electrolyte in place. The bond between the fiberglass mats, the lead plates and the battery housing makes them spill impervious and the most impact resistant batteries on the market today. They were originally designed to be used in aircraft.* I have 4 of them on my personal trawler.

An AGM battery can do anything a gell-cell can do, but only better. However, since they are also sealed, charging has to be controlled cautiously or they too can be ruined in short order.

Absorbed Glass Mat batteries are relatively new but are rapidly winning acceptance. There are some good reasons to use them:

1 - Absorbed Glass Mat (AGM) batteries can dispense a charge at a higher rate than flooded cells.

2 - No gassing under normal conditions: AGM batteries are sealed under pressure to recombine oxygen and hydrogen into water during the charging process. You find AGM batteries on high-end new yachts such as Hinckley and Broward.

The ability to put AGMs in the bilges (they can even function under water) also lengthens their lives; Remember that for every 15 degrees over 77F, a battery's life will be cut in half*

AGM batteries will even operate upside down and even if a container is crushed, it will not leak. This should be of particular importance to blue-water cruisers that could find themselves tossed around; you would not want sulfuric acid in your boat. And as always, appropriate tie-downs are always recommended.

AGMs require no maintenance once the charging system has been properly set up.

There is one issue that must be considered however and that is the price of an AGM battery:

Let's review prices

-*** Wet cell 8-D - $150.00
-*** Gel - 8-D - $250.00
-*** AGM - 8-D $365.00 (Marine centers have them for $501.00)

So choose the battery you feel is best for you and have fun with your trawler.

 

[FF]

The biggest difference is the RATE st which they will accept a charge.

Anything but cheap old wet batts is of virtually no interest for dockside folks or those without a DC noisemaker with 300+A of charging ability.

An inverter with 100A or 2 -100A alternators is not anywhere large enough to recharge at a high enough rate to be worth extra bucks.

If you want to pay 3X as much just to not water them , its your minibucks.

 

[Bendit]

Our Sonnenschein gel batteries, house and start 800AH in total, are now 16 years old and perform as new!

 

[FF]

are now 16 years old and perform as new!


How do you measure the total capacity now aviliable?

 

[RickB]

FF wrote: How do you measure the total capacity now aviliable?

What some gauge or test says about the capacity is immaterial and by the sound of it doesn't need measurement.


The*poster said they work the same for him as when they were new, that says it all. He has not seen any loss of performance or utility in the 16 years he has had them.

Their capacity has not dropped below what he needs or uses. That's the bottom line.


*


-- Edited by RickB on Tuesday 11th of May 2010 08:01:51 AM

 

[artwork]

"Their capacity has not dropped below what he needs or uses. That's the bottom line."

Point taken - but. . .* if we want to compare this battery set-up fo ruse by another boater, we need a common measuring point.* "It works for me" is not much* of a yardstick.

Gel cells 16 years old, wow. When were they first on the market?* My memory does not go back that far.*

 

[C lectric]

Bendit,
You are not alone. Not all my gels are that old. I slowly changed as money permitted. I have two for the engine that are '94, the remainder for the house are about 2001.

I won't say that they haven't lost capacity overall but they still do the job well I ask of them.

When it comes to change time I'll look again.

 

[Bendit]

They are 1994 vintage. I have a SOC meter which measures amp hours remaining.

While I have only had this meter for six years, there has been no measurable deterioration in this time. Reserve capacity appears unchanged, in other words the usual drop in available AH during the day (or night) and charging times, either main engine or DC genset, are also the same as ever.

Six years ago, they were reconditioned (desulphated), checked and accurately measured (20-hour capacity) - they met the original specs.

I know several fellow boaters with gel cells equally as old.
I expect that a cell will fail one day!
Cheers,

 

[Delfin]

Bendit, thanks for the report. I switched from Gel to AGM because the gel cell I put on a prior sailboat seemed to take forever to accept a charge. The AGM I have now (Northstar) are able to handle easily the 200 plus amps @ 24volts for quite awhile my current boat can put out. Do you feel that the Gel have an acceptance rate that is ok? I presume so, but am curious if you feel you have to run the charger a long time to restore charge.

Thanks!

 

[Bendit]

Hi Delphin,
Our systems can't deliver 200amps, so I don't know if the gels would accept that rate of charge or not.

I said 800ah above for the sake of convenience, but actually it's configured as 400ah at 24V,
200 for house and 200 for start. Start doesn't need this much and I could rearrange to 300 house and 100 start, but 200 house is all we need - even with 2 x 24V fridges and a 24V freezer.

When charging with the DC genset, I limit the current to 90A at 24V or else the little Kubota stalls! The alternator on the genset is rated at 120 amps.
I have set the rpm at only 1500 so that there is still a reasonable load on the engine when the charge curve drops off. Maximum power (12hp) is at 3600rpm so I'm only using about 4hp at 1500.

Anyway, at 90A max recharge from 150ah remaining (typically in the morning after anchoring overnight) to 190ah takes about 50 mins.

The main engine alternator is also rated at 120amps 24V hot. The shore power charger is 20amps and we have two 80W solar panels on the pilothouse roof.

Both the main engine alternator and the genset alternator are controlled by Amplepower SAR V3 regulators set to the gel "higher voltage option".

Works for us, but may not be ideal for everyone.


-- Edited by Bendit on Sunday 16th of May 2010 02:56:14 PM

 

[FF]

150ah remaining (typically in the morning after anchoring overnight) to 190ah takes about 50 mins.

Sounds like you have it right , you are working on just the top 1/3 or 1/4 of the batt set , which insures good long life.

 

[bobfnbw]

Recently went from 800 AH of Golf cart 6 volt batteries to 600AH of TPPL AGM batteries on our Endeavour 40 sailboat.
The TPPL are agm batteries made by Odyssey for Sears, sold under the diehard platinum name. This are 100 ah batteries group 31 size at 250 bucks each. They will accept a high charge and can hold a charge for a long time if not used.
They can be used on the side, or even under water. They will not off gas or release acid.
They have a nice warranty.
They must be set up with a smart charger and can never be equalized.
Highly recomended. And at 65 lbs or so each, can be carried by one man.

It seems to me that trawlers have a different electrical need than sailboaters.
Just remember that a battery may have 100 ah in it, but there is a big difference between what is avialable and what should be used.
Since running a battery down to nothing is killing it, a battery should not be discharged below 50% charge. And since it takes a lot of power to fully charge a battery (although on a trawler running for a long time it should not be a problem) most batteries are there for cycled between 50-90% SOC.
So for a 100 ah battery, that means you have about 40-50 ah available.
If your daily needs are 200 ah, then you would need 5 of them. Since there are inifinicies in charging you would have to put back more than you took out.
I often see power boats with a lot less battery charging capability that what I am used to on a sailing yacht. Smaller alternators, smaller charging systems and less batteries.
Why is that ?

 

[Marin]

Probably depends on how the boat is used by the owner. Our boat was built with a pretty minimal battery system--- 2 8Ds. The stock alternators (which we still have) are 45 amp Motorolas (or maybe 50, I'm not sure).

As built the boat had minimal electrical needs. A bit of instrumentation and lights was all plus the anchor windlass. As previous owners and we added more electrical demands--- AC/DC refrigerator to replace the original ice box, more and newer navigation equipment, radar, etc,---- it began to require some fairly conscientious electricity management to make sure the batteries weren't drawn down too much.

The batteries would be charged back full after a day and a night at anchor and engine starting in about three hours or less of the engines running at cruise power.

However, the boat has always had a 7.5 kw generator. This, first through the boat's original switchable but "dumb" charger and now through the inverter/"smart" charger we had installed, will charge the batteries up in pretty short order. Usually an hour a day when we're cruising is all that's needed, which also heats water for the rest of the day at the same time. The generator has its own 4D which, other than being charged by the alternators or the charger, is independent of the boat's electrical system.

A few weeks ago we finally got around to having our electrical shop change the whole battery system from the two 8Ds to six 6v golf cart batteries. This doubled our house power capability while the so-called start battery capability stayed the same. I say so-called because our boat combines every battery on the boat (other than the 4D) whenever an engine start button is engaged. So whichever battery (or battery combination) is not being used for house power becomes the "start battery" simply because it's not being drawn down by house loads.

But even with the two 8Ds, only one of which would be used as the house battery we never drew anything down even to 50 percent according to the volt meter. But we were very judicial with our use of power.

By today's standards our boat has a pretty minimal electrical system, even with the new golf cart battery setup. But for the way we use the boat, it's proven to work very well for us.

-- Edited by Marin on Saturday 22nd of May 2010 12:12:08 PM

 

[Fotoman]

marinetrader wrote:
Let's review prices

-*** Wet cell 8-D - $150.00
-*** Gel - 8-D - $250.00
-*** AGM - 8-D $365.00 (Marine centers have them for $501.00)

So choose the battery you feel is best for you and have fun with your trawler.

Interesting article but the prices don't look right to me. Just bought 2 4D wet cell and couldn't find anything under $225 each. So $150 for 8D is highly unlikely. Not sure about the other types but that looks pretty low as well.

*

 

[FF]

So $150 for 8D is highly unlikely

NAPA or Sam's Club.

The problem is the size " 8D " (only a size like size 9W shoes) does not equate to a deep cycle batt or a start batt.

You have to select which type you need for your service.

However we use BIG deep cycle batts and have no problem starting with them , but most operation is above freezing , where starts would be better in really cold soaked engines..