Ok, until you know what your needs are going to be I would go with two Group 27, deep cycle, wet cell batteries with around 100 ah each. These connected to a (1,2,both,Off) switch will give you the alternative of having two separate 100ah banks or one larger 200ah bank. The recommended mode of use is to alternate the use of battery #1 and battery #2 leaving the other in reserve on each different outing. This way both batteries get exercised but you always have one for backup. Understand that the battery selected at the switch will carry the electrical loads and receive the charge from the alternator. If the battery in use gets low in charge you can always combine with the other one by switching to "Both" or "All". When the engine is running and you need to move the battery selector make sure you do not pass or set at "Off" as you may damage the alternator. A boat without refrigeration and any other large electrical load should not use more than 20a in a day so you should be fine operating with just one battery. Now if you anchor out and run an anchor and cabin lights then you might use a little more but you always have the 2nd battery in reserve to provide a boost to start the engine the following day. As soon as the engine starts go back to the original battery in use so that it may charge. To maintain the batteries charged an inboard electrical charger that can operate with shorepower rounds out the system. Lots of sailors operate with such a setup and should serve you well until you pin down your needs. You could write a whole big book about batteries, charging and electrical systems to meet a variety of boater needs.
Battery Size
- Thread starter lehighsail
- Start date
Can I Connect diferrent Batteries together?
Bingo, bingo, bingo we have two winners!!!!
* Batteries should match if put into one bank. Match battery brand, battery model and date code!
I have a trolling motor (marine battery) for a dinghy that I was thinking of connecting to my boats engine battery to keep it charged with the engine and/or charger. My thinking is that this way I can have 2 engine batteries (which i do not need) and keep the trolling motor charged till I need it for the dinghy.
My house batteries are 3 batteries connected together and the charger and alternator appears to keep them charged good. I have 2 chargers one for house and one for the engine battery. The are just alike (guest) see photo.
The 3 house batteries are exactly alike. I read that connected batteries in one bank have to be alike. So my question is, do they really need to be alike or is it prefered. Will it hurt anything If I connect 2 different brand deep cell batteries together both 12V?
Also I would have to store the additional engine battery about 10 ft away from the original battery. Therefore' I would have to run 10ft of wire. Will this affect the charging. I have some 6 gauge wire I can use.
Thanks Mike
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It was mentioned that running the battery down to %50 is OK. I and many friends have golf carts and want maximum life from the batteries. All manufacturers info I have read say allowing the total charge to drop below %80 will shorten the battery life. I have installed meters on mine and others so we know the state of charge. At $600 minimum a set, we want them to last.
Voltage - 12V @ 100% = 12.7v - 75% =12.4v
* Sulfation of Batteries starts when specific gravity falls below 1.225 or voltage measures less than 12.4 (12v Battery) or 6.2 (6 volt battery). Sulfation hardens the battery plates reducing and eventually destroying the ability of the battery to generate Volts and Amps.
Voltage - 12V @ 100% = 12.7v - 75% =12.4v
* Sulfation of Batteries starts when specific gravity falls below 1.225 or voltage measures less than 12.4 (12v Battery) or 6.2 (6 volt battery). Sulfation hardens the battery plates reducing and eventually destroying the ability of the battery to generate Volts and Amps.
I've never heard battery manufacturers push an 80% level.
Any use will shorten the life of the battery to some extent. Falling below 50% accelerates the wear.
Calder's book has charts from a major wet cell battery manufacturer illustrating the life cycles predicted at different discharge levels.
Calder also rejects the idea of alternating house banks. One big house bank is much better than 2 small ones.
Any use will shorten the life of the battery to some extent. Falling below 50% accelerates the wear.
Calder's book has charts from a major wet cell battery manufacturer illustrating the life cycles predicted at different discharge levels.
Calder also rejects the idea of alternating house banks. One big house bank is much better than 2 small ones.
I've never heard battery manufacturers push an 80% level.
Any use will shorten the life of the battery to some extent. Falling below 50% accelerates the wear.
I've never heard battery manufacturers push an 80% level.
Any use will shorten the life of the battery to some extent. Falling below 50% accelerates the wear.
From Trojan guide tips
1. Shallow discharges will result in a longer battery life.
While they say you CAN discharge to %50 after this statement, as many do, they want to sell batteries. No, it's not the manufacturers that say to charge when drop is below %80, it is the independent tech sites that make that claim. In addition to the earlier post.
"One key point to understand is that the process of sulfation starts when the specific gravity of batteries falls below 1.225 or voltage measures less then 12.4 (12 volt battery) or 6.2 (6 volt battery). The management of specific gravity is the single most important factor in reducing sulfation. It is also the most important variable in determining how long the battery can yield effective energy as it discharges and the overall longevity of a battery"
Thanks for making me review stuff I studied more than 2 years ago. While it may be IDEAL to stay above %80, A discharge of %50 gives so much more useable power, it is what I will use on the boat. SO glad to know now that the extra drop in battery life is negligible. I was thinking to add another, you saved me $140.
Upon reflection, I will split the difference and only drop to %65
Batteries can sulfate at any SOC below 100% and can also sulfate and suffer under long term low voltage float charging. One of the fastest ways to kill batteries on a sail boat is to only charge with an alternator.From Trojan guide tips
1. Shallow discharges will result in a longer battery life.
While they say you CAN discharge to %50 after this statement, as many do, they want to sell batteries. No, it's not the manufacturers that say to charge when drop is below %80, it is the independent tech sites that make that claim. In addition to the earlier post.
"One key point to understand is that the process of sulfation starts when the specific gravity of batteries falls below 1.225 or voltage measures less then 12.4 (12 volt battery) or 6.2 (6 volt battery). The management of specific gravity is the single most important factor in reducing sulfation. It is also the most important variable in determining how long the battery can yield effective energy as it discharges and the overall longevity of a battery"
Thanks for making me review stuff I studied more than 2 years ago. While it may be IDEAL to stay above %80, A discharge of %50 gives so much more useable power, it is what I will use on the boat. SO glad to know now that the extra drop in battery life is negligible. I was thinking to add another, you saved me $140.
Upon reflection, I will split the difference and only drop to %65
Deep cycle batteries, as in golf cart, industrial and motive batteries, are usually rated for X number of cycles to 80% depth of discharge or 20% State of charge. Despite the batteries being able to discharge to 80% DOD repeatedly they are suffering more to do so than stopping at 50% DOD.. The bottom line is the shallower the discharge cycle, and the more complete the recharge cycle, along with proper voltages, the longer the batteries will last.
As can be seen below the shallower the cycles the longer the batteries last. The top line are true deep cycle batteries such as 6V golf cart and industrial batteries. The tan line are 12V "marine" type batteries group 24, 27 & 31. There is a HUGE difference in cycle life between batteries intended and specifically built for deep cycling and pseudo deep cycle batteries such as the 12V marine batteries most boaters use that are really only "labeled" for deep cycling....
You seem to be confirming my original post. While it is easy to set my cart on the charger any time it drops below %80, it's not so easy on the boat, using solar and controller. I specifically bought the Wally world group 29 marine battery because of the warranty. ANY failure within two years, they replace with new. I don't race, nor require much daily amps as my goal is to cut my time spent with tech stuff and READ this stack of history and science books I have bought and saved, but still want to take reasonable care of the battery, I did plenty of research on high dollar batteries and repeatedly found one year limited warranties. I also found that many batteries coming out of China now-- most all do, do not last like the same models did years ago. They are lighter, less lead, and less lifespan. I buy a lot of electrical devices, and constantly see a %10 DOA from reviewers. So the warranty is my top priority. Thanks for pitching in, any advise is welcome.