Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 14-10-2015, 14:22   #16
Registered User
 
frozenhawaiian's Avatar

Join Date: Dec 2014
Location: Portland, Maine
Boat: 1970 hinckley 38
Posts: 150
Re: Help Me calculate How Big My House Banks Should Be.

thankf for all the input guys, I'll spend some more time working on the usage worksheet. the reason the boat only has a start battery at the moment is because it came with no batteries and I'm in my midst of a refit. boat has yet to be in the water under my ownership. fortunately I have very easy access to my battery bank box. it's quite deep as well. so I'm lucky in that regard.
__________________

__________________
frozenhawaiian is offline   Reply With Quote
Old 14-10-2015, 16:26   #17
Registered User

Join Date: Sep 2014
Posts: 112
Re: Help Me calculate How Big My House Banks Should Be.

1. get nigel calder's maintenance guide.
2. read it.

the short answer to your question is as big as you have space for. then as much free charging, solar, wind that you can. and be very conservative using power.

you got a lot of good advice but Nigel's book is a must and will pay for itself.
__________________

__________________
AlwaysFORSAIL is offline   Reply With Quote
Old 14-10-2015, 21:24   #18
cruiser

Join Date: Jan 2012
Location: Lake Ontario
Boat: Douglas 32 Mk II
Posts: 1,921
Re: Help Me calculate How Big My House Banks Should Be.

Quote:
Originally Posted by a64pilot View Post
My example is straight out of Lifeline's battery manual, and your trying to use total amp hours drawn out, which wasn't the point, number of cycles is.
Now I assume those numbers are essentially un-obtainable outside of a lab, but they do illustrate the point.
Regularly discharge to 50% SOC and you are doing good to get much over two years out of a bank, shallower discharges will mean the bank lasts longer. Plus it's tougher to recharge a smaller bank to full capacity as the acceptance rate is lower.

I'm new and just getting a handle on this myself, but if you discharge a bank to 50% on a cruising boat not on shore power, how are you going to fully re-charge it?
Actually, total amp-hours should be the point. If you add enough battery bank that you only draw down 10%, you will need to raise your water line and tow provisions in the dinghy.

The best plan is to size the bank so that you discharge to about 50% and recharge (engine at anchor) to 80%. If you have solar and wind that will eliminate the engine and perhaps charge higher on optimum days, TERRIFIC.

For days that you are on shore power, there is no discharge cycle. For days that the engine runs underway, your discharge will be much less. So a simple lead-acid deep cycle bank should last about 5 years if treated this way.

I would far sooner replace 4 batteries every 5 years, instead of 8 batteries every 10.

Ramblin Rod
www.sheenmarine.com
__________________
ramblinrod is offline   Reply With Quote
Old 14-10-2015, 22:26   #19
Registered User

Join Date: Sep 2014
Posts: 112
Re: Help Me calculate How Big My House Banks Should Be.

Get Nigel Calder's maintenance guide, read it. The shart answer to
__________________
AlwaysFORSAIL is offline   Reply With Quote
Old 15-10-2015, 00:18   #20
Registered User

Join Date: Apr 2013
Posts: 4,871
Re: Help Me calculate How Big My House Banks Should Be.

Quote:
Originally Posted by a64pilot View Post
My example is straight out of Lifeline's battery manual, and your trying to use total amp hours drawn out, which wasn't the point, number of cycles is.
Now I assume those numbers are essentially un-obtainable outside of a lab, but they do illustrate the point.
Regularly discharge to 50% SOC and you are doing good to get much over two years out of a bank, shallower discharges will mean the bank lasts longer. Plus it's tougher to recharge a smaller bank to full capacity as the acceptance rate is lower.

I'm new and just getting a handle on this myself, but if you discharge a bank to 50% on a cruising boat not on shore power, how are you going to

fully re-charge it?
The point is if you only allow 10% discharge, you need a battery bank that is 5 times the size.

So if we calculated 8 batteries will give us a 500 usable amp-hrs at 50% discharge, we would need 40 of the same batteries to limit the discharge to 10%. There are a number of problems with that:
- That is a huge volume and weight to be putting on a typical 35-45' cruising boat.
- While I've heard stories of longer lives, I've never seen a battery that lasts more than 7-10yrs. 5000cycles (assuming 1 cycle/day) is a little shy of 14yrs. Odds are they die anyway. Anything goes wrong (say a dead cell not caught while you are away from the boat) and you could trash the system far earlier.
- 1000cycles is a little shy of 3yrs. You can have a brand new bank every 3yrs and pocket any unused money if you sell before 14yrs.
- If you only discharge 10%, that means you are always working in the hard to replace last 10%. Where as if you take it down to 50% most of your charging is in the easy part where you can dump lots of amps in so it charges quickly.
- Theoretically, you have to buy the same number of batteries over 14yrs but with the smaller bank, you can earn interest on the money from the batteries you didn't buy.

Reality is I lean more towards the 30% range and if you look at the example I gave, I suggested 50% only if you have a multiday storage which means it would only cycle down by maybe 25-30% most days. with rare cycles down to 50% (probably will happen a handful of days per year).

Now if you talk about something crazy like 90% discharge, you may only get 100cycles, so the theoretical 100amp-hr battery will only have a life cycle of 10,000amp-hrs which is drastically less over the life of the battery compared to the other two.
__________________
valhalla360 is offline   Reply With Quote
Old 15-10-2015, 10:36   #21
Registered User

Join Date: Aug 2015
Location: Marina del Rey Los Angeles, CA
Boat: Liberty 458 46' sail
Posts: 36
Re: Help Me calculate How Big My House Banks Should Be.

We spent about 15 years cruising in the south pacific and west coast of US on a Liberty 458. We have been very happy with 8 Trojan 105s. We never made an effort to skinny things down to within a few amps of what we really need because things are constantly changing. We like having margin and not being dependent on charging every day. You need that. There will be times when you cannot run an engine/generator to charge. Or something won't run and you cannot fix it right away.


A bigger bank will last longer before you have to replace the batteries. Trying to get down to the minimum means you have not margin for any future changes or things that go wrong. We do not panic when the alternator fails. We can change it "tomorrow"


A number of folks have pointed out that you mixed running and anchor stuff together. You do need to separate this. Biggest consumer for most cruisers is the refer. Put some effort into measuring consumption there. Insulate well
One big thing that is missing is fans.
In Mexico up in the sea, we used a LOT of


Definitely invest in some form of battery monitor. Your consumption will change over time and you are blind without something to measure total consumption.


power on the fans.
__________________
svseawitch is offline   Reply With Quote
Old 15-10-2015, 21:28   #22
Registered User

Join Date: Jun 2013
Location: canada
Posts: 1,695
Re: Help Me calculate How Big My House Banks Should Be.

Quote:
Originally Posted by svseawitch View Post

A number of folks have pointed out that you mixed running and anchor stuff together..
do you not leave your depth and wind on 24/7?
__________________
smac999 is online now   Reply With Quote
Old 16-10-2015, 02:11   #23
Registered User

Join Date: Apr 2013
Posts: 4,871
Re: Help Me calculate How Big My House Banks Should Be.

Quote:
Originally Posted by smac999 View Post
do you not leave your depth and wind on 24/7?
The proper technique is immediately after signing the purchase paperwork, you go onboard and turn every switch to the ON position.

About an hour before selling, you switch them to the OFF position so the new owner gets the full experience.

OP: Just kidding. It's a simple mistake but easily rectified at this point in the process.

The hard part for people to grasp is you won't come up with an exact number. You have to balance a little capacity to spare to account for new devices being added, old batteries that may only have 90% of thier original capacity and the like vs needing to find room for and pay for 2 tons of batteries to cover every possible eventuality.

It's still well worth the trouble to run the estimates but don't expect to be accurate to the nearest amp-hr.
__________________
valhalla360 is offline   Reply With Quote
Old 16-10-2015, 17:23   #24
Registered User

Join Date: Aug 2015
Location: Marina del Rey Los Angeles, CA
Boat: Liberty 458 46' sail
Posts: 36
Re: Help Me calculate How Big My House Banks Should Be.

On Sea Witch, we do leave our wind and depth on while at anchor. Raymarine instruments all power up from the same buss. We almost always have a shallow alarm setup on the depth finder. I sleep better. Total consumption of the 3 instruments are trivial.
__________________

__________________
svseawitch is offline   Reply With Quote
Reply

Tags
cal

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks sytaniwha Electrical: Batteries, Generators & Solar 5945 01-11-2017 07:57



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 00:35.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.