House batteries - Catalina 36 MkI

[drdanj]

I have two standard size house batteries under the rear starboard settee, and one starter battery under the forward settee. I've seen several comments about having three or four house batteries and wonder about adding more. Where have people placed them? Is the primary advantage simply being able to run more electricity longer without shore power? Is there any disadvantage in terms of getting batteries charged back up (I would assume it takes longer).

Dan
S/V Tao
1983 Catalina 36

 

[Benny17441]

Yes and yes. Additional batteries occupy space, add weight and cost money. No upside really unless you really need the additional capacity. A battery bank upgrade may require a resize of the battery charger.

 

[jssailem]

As Benny shared. More batteries more available juice. 200 amp hours of battery power, when discharged 50% 100 amp hours will take a 10 amp charger approx 10 hours to fully recharge. 20 amp charger about half the time. Then there is solar charging. Money for equipment free sun power. Also you can run the engine enroute to help charge recharge the batteries. All depends on what you want.

 

[Benny17441]

One thing about batteries is that their ability to accept charge diminishes the closer they get to full charge. When a battery is over 30% discharged any smart charger will be delivering bulk rate or full rated power but gradually as the battery continues to charge the charging rate is reduced by the charger to match the acceptance rate of the battery. In this phase of the charging task a 40A charger may be putting out the same charging current as that of smaller chargers. On the other side of the coin a set amount of Ah usage may represent 35% discharge to a small battery while only perhaps 20% discharge to a larger battery. You can see how the smaller battery may be charging at bulk rate while the larger one is only charging at a reduced rate. When the smaller one reaches 20% it will have less Ah to replace than the larger one. There is also usage of the battery, it has been said that in order to extend a deep cycle battery life it is good to give them a good deep discharge (45-50%) every once in awhile then followed by a full charge. Too large a battery will seldom see a discharge of over 20% and that means the battery is not exercised enough. It is always good to have extra capacity but not excessive. To double the size of the bank without first knowing your usage and your needs may be a costly yet not a productive endeavor. There are different types of batteries and charger combinations but the above generally holds true for wet cell batteries coupled to a regular three cycle charger.

 

[Stu Jackson]

Dan,

What are you intending to do with your boat?, as Bennie asked. If you marina hop, whatever you have now is most likely adequate.

If you intend to go further afield and anchor out, you will need to investigate the options you have to upgrade your electrical system, not just the number of batteries.

But based on your basic issues type of question, the guys have started to retype what you'll find in any good boat electrical book. Charlie Wing's is a good one.

You might want to wander around here, too:

Electrical Systems 101 http://c34.org/bbs/index.php/topic,5977.0.html

Don't know if you are aware of these good guys, too --- www.c36ia.org

Good luck.

 

[Calif. Ted]

The standard size batteries on my 270 were Group 27, the size of a car battery ~45 lbs. Standard size on my 320 was 4D, 95 lbs. takes two people to get in or out of the boat. Many people replace with multiple 6 volt batteries to increase AH capacity and ease replacement, some just add an additional starter battery and devote the others to a house bank.

 

[Joe]

You need to analyze your AH needs and wants. Become aware of what devices are the most power hungry... and things you absolutely have to have running when separated from shore power. Make a chart.... comparing system consumption with battery capacity and re charging rate. Does this sound confusing? .... if it does there are many sources for your enlightenment. Try "The 12 Volt Bible for Boats" . It is a fundamental read for any boat owner.

 

[jviss]

There's a lot of incorrect and distorted information in this thread. For example, the recommendation that "it has been said that in order to extend a deep cycle battery life it is good to give them a good deep discharge (45-50%) every once in awhile then followed by a full charge." For most lead-acid, deep cycle batteries this is completely incorrect, and will shorten the life of the batteries. This is true for older NiCad batteries. On the contrary, a periodic equalization charge, which is like an over-charge, will extend the life of flooded lead-acid, deep cycle batteries. Whether that's good for AGM or gelled-electrolyte batteries is debatable; contact the manufacturer.

If you are not an electrical system expert it's best to stay with the size and type of battery your system was designed for. It could well be your current batteries are at end of life. This can be presumed to be the case if hey are old, and it can be determined via appropriate test equipment, and/or electrolyte specific gravity measurements (for a flooded battery). Good, flooded, deep-cycle batteries are not very expensive; best are the freshest. Walmart or Sam's Club are a great source for economical, recently manufactured, flooded, deep cycle batteries. If you can afford it, and your charging systems, i.e., engine charging system and shore charger can be adjusted for them, AGM (absorbed glass mat) lead-acid are probably the best performing, in my opinion. They are about double the price of equivalent flooded, but require much less maintenance, and have a deeper usable capacity.

There's a lot to this. For battery expertise, google "Battery University." For systems, see some of the books mentioned above. If you're not an engineer, or think or act like one, seek expert help.

 

[LeslieTroyer]

Dan on my MK1 I have 6 batteries - 2 6V house same location as your house, 2 6V house under the nav seat, 1 starting battery just aft of the stuffing box, and one on the starboard side of the V birth (dedicated to the windlass).

 

[Justin_NSA]

Maybe look at less consumption I.e. get rid of your incandescent lights. older power hungry equipment etc. Solar or wind might be a more diverse option too. Just my $.02

 

[jviss]

Justin makes good points. LED lights in the cabin, and for anchor light save us a lot. Solar keeps my batteries topped up on the mooring during the week. If you can afford 100+ Watts of solar you could probably leave your fridge on always.

 

[drdanj]

Thanks for all the feedback. I've changed most (not all) lights to LED including the anchor, and I have some solar lights. I also have one group 31 windlass battery (yes I know the debates about whether to have a separate windlass battery or not, it's there, fine). Stu, you're right, mostly marina hopping, some weekends out, at this stage, I doubt I'll invest in solar, not likely to get enough pay back to do so. A life regret -- wish I'd started sailing 30 years earlier! Who knew?

 

[jssailem]

not likely to get enough pay back to do so.

Dr Dan, in looking at the solar payback, a small 85-140 watt system appears to be able to keep the batteries charged while away from the boat. Ido not sail every day ( I wish). While not at the boat I dislike leaving the boat wired to the dock and the charger chugging away. I'm thinking a solar setup would provide the charge needed to keep batteries healthy. Thoughts?

 

[drdanj]

John, I know little about solar, but know the technology is advancing swiftly. I wonder if a flexible panel on top of the dodger would be big enough to be an improvement. I'm in So Cal, so get a lot of sunshine (Except when Catalina Eddy visits). Would that be enough to run the fridge? One thing that's interesting is our energy needs have gone down so much. We all have small solar light. I'm perfectly happy with my cell phone and a Bluetooth speaker (or even headphones) both of which can be charged easily, rather than having to run a big stereo system. Little solar lights scattered around do a lot. I have a solar string light around the inside of the dodger for night light.

 

[LeoLambert310]

Just a note, I have 2 65 watt flex panels and this will keep my batteries charged.

 

[William Jacobs]

I don't think there is any disadvantage.