Isolator for batteries

[Jim Seamans]

Hi Guys,Praying for warm weather!I'm planning in the month of Feburary to install a new bank of batteries for my H356. Currently there are two group 27 batteries which I'm going to parallel and make the starter bank. The second bank will be made up of four Trojan T105 6 volt in series, paralleled to give me 450 Ahrs, these will be the house batteries.After reading out on the net, I get the feeling I need a isolator for the two banks to insure they get charged correctly and don't cross feed each other. What is the wisdom from the group about this?JimS/V Java

 

[Les Blackwell]

I've done almost the same thing on my boat

You're on the right track. First, a deep discharge group 27 will be more than ample for your motor battery. You don't need two--that's overkill. I use one on my Yanmar which is bigger than yours.You are correct, four 6 Volt batteries in a series will give you about 420 amps which should be enough for your refrig and freezer and the electronics. Not enough for the microwave.The next step is to add a combiner which acts as an isolator but also allows your engine alternator and battery charger to charge both at once. A good combiner is made by West Marine and is not expensive.I would also put in your engine room a smart regulator (disable the one on your alternator) which will make better use of the alternator's output when under way with the engine. You don't need a high output alternator when you make maximum use of the one that came with your engine which is about 55 amps at full cruising speed.Another thing that I would do is to toss the battery charger and get a Truecharge 20 plus (made by Statpower) which is a state of the art battery charger. It does everything but make your coffee in the morning.I would do one more thing and that is add a Link 20 two bank battery monitor. Expensive but a great peace of mind.I have this system on my Hunter 380 and I can go out on the hook for three to four days without starting the engine. The Link tells me what the status of my batteries at all times. I've used this system now for four plus years and have not had any problems. It is well worth the expense and trouble to install everything.

 

[Fred Ficarra]

Consider only ONE bank

We run the golf carts you are planning and they are wonderful. Read the West Marine advisor on batteries. We had done, in the 80's, what they are now recommending and that is to use only one bank, the house bank! As you review Les' recommendations, see how much less complicated your system would be with only one bank. If you are worried about the engine starting with low batteries, it would only fail to start on the bank you are planning to install, if you walked (swam) away from the boat for an extended period of time and left everything on. Forget about it! And if you do commit that sin, open the compression releases and fire it up on one cylinder. I cranked my 3gm30f all the way to the Panama Canal with this setup because of bad fuel and the house bank never slowed down. There is more on our H34 Epitome' Rebuild web page at http://members.tscnet.com/pages/ss427/Epitome's%20Rebuild.html. We have 30+ snaps there but not too much about the battery bank because it is so simple. I agree with Les about a good charger. We went with the Prosine 2.0. It has a 100amp charger built in plus a bunch of other neat stuff, like every function you need for monitoring your dc the way the 'Link' does. Of course it's a 2KW true sine wave inverter too. And simple? It's working automatically, except for equalizing. You have to tell it to do that. Mail me at ss472@tscnet.com and we'll talk about it. Good Luck. Fred

 

[Kenneth Pfaff]

Posted a similar question a couple of weeks ago

on both this forum and on the cwbb. I received and excelent response on CWBB, from the owner of the company that makes the battery combiner for West Marine.  From his response I made the decsion not to go with the isolator but to go with a battery combiner. There web site has a lot of documentation and info on this and related topics. I don't have the web address with me, but if you do an archive search on the CWBB for the last two week, I am sure that you will find it.

 

[Scott]

Same boat

JIm, I'm in the same boat as you, pun intended. I have a lot to learn about the electrical system on the boat and have read a lot. I have the Group 27s too and am thinking of leaving one on a starter bank and buying one or two more for a house bank. I'm not sure what I "need" and what is "nice to have". For instance, it seems I read a lot about chucking the charger but no one says what's wrong with it. The owners manual seems to meet any requirements I've read.I do like and plan to stick with West Marine's 24 recommendations. See the link.

 

[Jim Seamans]

More Questions than Answers

This electrical stuff is causing more questions than answers and wondering if it is worth the hassle. I was speaking to a installer yesterday late and he stated that to get 1 amp AC you will pull 11 amps of DC, so it better be worth it. Will need to purchase a new alternator to replenish the DC.My wife and I stay out on the hook all weekend, slips and marina's are not for us. We sail and explore. But a bag of popcorn would be nice!!!Scott we will need to get together this year, I'm at Cobb Island.JimS/V Java

 

[David Dick]

information

You can get a lot of information and answers to your questions from Jack Rabbit Marine, see the following link:http://www.jackrabbitmarine.com/reference/dialogs_list.html

 

[Ed Schenck]

Why Jim?

What will you be using that is cause for concern? Yes, a one amp AC appliance will use about eleven amps of DC. And a hair dryer will use about 200 amps(2000 watts/110x11), but only for a few minutes. You stated you will have 450 amp/hours, that's a bunch. You can run a lot of stuff for a weekend on 225 amps(not to exceed 50% of battery supply). And your Yanmar should put back at least 50 an hour.Do you have a spreadsheet for calculating usage. I have a really good one(at home). But you can easily make your own. A good start is over on Sailnet, see Related Link.I am still undecided about recharging at anchor. Solar panels seem so limited except for keeping the starter battery topped off. I generate more watts on an exercycle in an hour than an $800. panel does in a day. What good is 20 amps if your refrigeration uses 50? And wind generators are only slightly better.

 

[Bob Allne]

Don't discount gas

Before adding a microwave to Kailani, a casual poll of neighboring boat owners revealed that their 600 to 800 watt units (.5-.7 cu. ft.) where almost exclusively used to zap popcorn, reheat coffee and exhibit time. Not enough space or power (via inverter) to cook much else. We decided to save the space for dry goods. Microwave popcorn requires 3-5+ minutes in a ~700 watt unit. Jiffypop on the stove will use a tiny fracton of an LP or CNG tank. Besides, wou'll want to eat the popcorn while watching your battery consuming TV and DVD player.CAJUN POPCORN SEASONING RECIPE2 tbsp. paprika1 tbsp. dried thyme2 tsp. freshly ground pepper2 tsp. dry mustard2 tbsp. dehydrated minced garlic2 tsp. salt2 tsp. crushed caraway seeds1 tsp. cayenne pepper, or to tasteThoroughly combine all ingredients and store in airtight glass jar.Note: To flavor popcorn, mix 2 tbsp. seasoning with 2 tbsp. melted butter and 2 tbsp. hot water, drizzle over popcorn and mix.

 

[John]

US Navy Electronic Technician say so!

In US Navy Electronic Technician training material, it says do not parallel connect two batteries.However, this technical aspect are very much overlooked by many sailors. I will not having this kind of system for my boat. There is way to wire the system which would select one battery only at any moment, regardless the number of battries you have.

 

[Bill Bell]

Dual Output Alternator

Jim,The 4 golf cart batteries are the start. I started that way and several hundred dollars later had the system done.A good way to isolate the house and engine batteries is to go with a duel output balmar alternater and a good 3 stage regulator. I did that and it works great.Also consider a Heart inverter with built in 100 amp charger (trickle 15 amps to start battery. Link 1000 or 2000 monitor.Bill