Deep cycle battery options...

LeeandRick · Sep 10, 2017

ArkadiyS said:
We currently have 2 new group 27 batteries, with a new 50w solar panel. We have a great (new) refrigerator that does not eat too much power at all, and the solar panel which is able to get both batteries to 13.7-13.9 in a few hours. We do not travel that much when not plugged-in, but do have a LED tv/AppleTV, laptops, and phones. I was thinking of adding a 35 AH 12v battery with a 4 position switch after the solar panel controller to divert to the batteries. Would would you recommend: a single 35AH battery, 2 of them, or a just one with a higher capacity of 50 AH, or 100 AH? Thanks!

How do you know how much power the refrigerator uses? Why exactly do you want to add two small batteries? Do not travel much????? I'm not trying to be an ass here but be a little more specific on what you are trying to accomplish may garner a few more answers. Keep it simple (KISS) and add more batteries to the house bank (keeping starting batteries separated) and understand that 50 watt solar ,where you live. will probably (IMO) never keep up with the load of a Hunter 35 . You could spend the money and do a power assessment with all of the expense of the required monitoring equipment or just wing it like many people do. Go out for the number of days you like and see how the batteries held up and if they got low add another one or two. Just be careful about adding new batteries to real old ones in a bank.

dlochner · Sep 11, 2017

For a variety of reasons, if you are going to add battery capacity, larger batteries are more efficient up to the point at which they are a challenge to move.

You may find this article helpful as well as others on Musings with MaineSail forum. https://forums.sailboatowners.com/index.php?threads/multiple-house-banks-vs-one-house-bank.184137/

Chief RA · Sep 11, 2017

For your reference: I have a 25' Catalina and use 2ea size 24 batteries with 160 watts of solar. A reefer, TV,etc will eat your 50w panel! No more batteries......you need 200w solar and go from there. Chief

Sumner · Sep 11, 2017

Chief RA said:
... A reefer, TV,etc will eat your 50w panel! No more batteries......you need 200w solar and go from there. Chief

Agree....

http://purplesagetradingpost.com/sumner/macgregor2/inside-22.html

200 is probably about minimum for a fridge if you are out for more than 3-4 days at a time. At least that is what I found using the compressor fridge on the Mac above. I have over twice that now (560 watts of Solar and 4 batteries).

http://purplesagetradingpost.com/sumner/endeavour-inside-mods/inside-index.html

The fridge/freezer on the Endeavour is about twice the size but get by with less amperage due to a lot more insulation, so it will depend on how long you want to be out and how good the fridge is,

Sumner
===============================================================================
1300 miles to The Bahamas and Back in the Mac...
Endeavour 37 Mods...
MacGregor 26-S Mods...
Mac Trips to Utah, Idaho, Wyoming, Canada, Florida, Bahamas

dlochner · Sep 11, 2017

ArkadiyS said:
I am also a big follower of KISS principle, and was hoping that this would be a simple dedicated add (through a separate 4-position battery switch). The new battery switch is to be able to toggle between where the solar charging will be directed toward, either the "house" battery, or to the main 2 batteries.

What you are proposing is not at all KISS.

The simplest system consists of a dedicated start battery and a large house bank. Each bank has a simple on/off switch and connects to a third switch like this Blue Sea Model. The alternator, charger, and solar all lead to a positive bus bar that is between the switch for the house battery and the Blue Sea switch. The start and house battery are combined with an ACR. In words this sounds more complicated than it really is. Somewhere MaineSail has posted a nice easy to understand schematic.

The value to this system is that
1) it keeps house and start batteries isolated,

2) with the turn of 2 switches the electric system can be run from either bank with the remaining bank isolated,

3) when any charge source is present, both banks will be charged as needed,

4) with proper placement of the isolation switches the system is pretty foolproof, the alternator cannot be disconnected while the alternator is running, preserving the alternator diodes.

The schematic I mentioned is posted on this forum, I just can't find it quickly.

Stu Jackson · Sep 11, 2017

ArkadiyS said:
The new battery switch is to be able to toggle between where the solar charging will be directed toward, either the "house" battery, or to the main 2 batteries.

This is the part that makes no sense.

You want the solar to go to the house bank.

You want the biggest house bank you can "make."

What is the difference in your mind between the "house" battery, or to the main 2 batteries?

These might help:

OEM 1-2-B Switch Wiring History http://c34.org/bbs/index.php/topic,4949.msg30101.html#msg30101

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615

This is a newer primer for boat system wiring design with a thorough digram: Building a Good Foundation (October 2016)
http://forums.sailboatowners.com/in...dc-electrical-foundation.181929/#post-1332240

The Short Version of the 1-2-B Switch Stuff: http://c34.org/bbs/index.php/topic,5977.msg38552.html#msg38552 This is a link to the Electrical Systems 101 Topic, reply #2

What are ACRs, Combiners & Echo Chargers? (by Maine Sail) [scroll to the top]
http://forums.catalina.sailboatowners.com/showthread.php?p=742417 and http://c34.org/bbs/index.php/topic,9404.msg70131.html#msg70131