battery system upgrade question - Page 3 - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance
 Not a Member? 
  #21  
Old 11-16-2007
Member
 
Join Date: Jan 2003
Posts: 74
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 12
scosch is on a distinguished road
I understand most of your points. Thanks!
Oooops. Me bad. I meant to convey that I probably use 5-10 A/hr at night, not 5-10 AHr. Two nights on the hook with lights and fridge and I can see Im at 50%.
I can see that more AHr are necessary, especially if sailing at night.
You mentioned a couple of things that I dont understand though.
You said I can keep my existing 50A internally regulated alternator if I switch to wet cells for the house (and eventually to the start bank too after Ive killed the AGM that you suggested putting over there to replace the GEL)
Why is that? Are you suggesting that for cost effectiveness? I thought wet cells benefited too from a more sophisticated multistage charger. And wouldnt a larger alternator get it done quicker? Or are suggesting to keep the old alternator only if I add a gas generator (which isnt immediately appealing on my 30' boat, storage for generator and gas is limited and they are quiet but still kinda annoying).
Thanks again and Ill check back in this evening.
Reply With Quote Share with Facebook
  #22  
Old 11-16-2007
sailingdog's Avatar
Telstar 28
 
Join Date: Mar 2006
Location: New England
Posts: 43,291
Thanks: 0
Thanked 10 Times in 10 Posts
Rep Power: 13
sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice
All batteries, AGM, Wet Cell or Gel, will benefit from a three-stage intelligent charger, provided it is set for their chemistry type. This is why mixing different types of batteries is a really bad idea.

Unless you run your refrigerator only at night, which I kind of doubt, the fact is that you're probably over using the house bank you've got currently. The problem is even worse if you've been sailing with the radar on, since that increases the daily amp-hour usage from the estimated 50-75 amp-hours to probably 100-125 amp hours, given a full day of sailing.

Unless you've got AGM house bank batteries or get a larger house bank, going to a larger alternator isn't going to help much. Wet cells can only accept a maximum of about 25% of their amp-hour rating in amps... so a 200 amp-hour bank, like the one you have will only accept 50 amps maximum or so... and only during the bulk charging phase. Batteries basically charge in three stages... BTW, charging wet cell batteries at more than C/10 (their amp-hour capacity divided by ten) for any significant period of time will boil off electrolyte and is not really a good idea.

The first is bulk charging, where the charge acceptance (amperage) is fairly high, and the batteries provide little resistance to the charging process. Going any larger on the alternator will cause the batteries to boil off electrolyte during this phase, and increase the amount of water you need to add to the cells.

The second is the absorbtion charge phase, where the charge acceptance rate drops considerably. This phase starts at about the 80% charge level and continues until the battery is fully charged.

The third is the float or maintenance charge phase. This occurs after the battery is fully charged and basically is to offset the self-discharge that normally occurs in rechargeable batteries.

I hope this helps.
__________________
Sailingdog

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
.

Still—DON'T READ THAT POST AGAIN.

Last edited by sailingdog; 11-16-2007 at 01:11 PM.
Reply With Quote Share with Facebook
  #23  
Old 11-16-2007
camaraderie's Avatar
moderate?
 
Join Date: May 2002
Location: East Coast
Posts: 13,877
Thanks: 0
Thanked 3 Times in 3 Posts
Rep Power: 15
camaraderie is a jewel in the rough camaraderie is a jewel in the rough camaraderie is a jewel in the rough
Scoche..you said:
You said I can keep my existing 50A internally regulated alternator if I switch to wet cells for the house (and eventually to the start bank too after Ive killed the AGM that you suggested putting over there to replace the GEL)
Why is that? Are you suggesting that for cost effectiveness?
YES and because you are not full time cruising and don't need to spend another $7-800 bucks + install for a week or two of extended cruising a year. Your charger at the dock will maintain your batteries properly.


I thought wet cells benefited too from a more sophisticated multistage charger. And wouldnt a larger alternator get it done quicker? Or are suggesting to keep the old alternator only if I add a gas generator (which isnt immediately appealing on my 30' boat, storage for generator and gas is limited and they are quiet but still kinda annoying).
All batteries benefit from a 3 stage but they don't need one 100% of the time. Your alternator is DESIGNED to work with wet cells without damaging them and as long as you do a lot of dockside charging normally...motoring and using your alternator is no problem.
I suggest adding a gas generator cause using a diesel to charge your batteries is BAD BAD BAD for your engine if it is not in gear....AND because that will allow you to use your 3 stage charger at anchor.

The only reason to add a larger alternator and separate regulator in your circumstance is if you are going to stay with AGM's which can take a higher charge rate AND need 3 stage regulation underway AND if you will be motoring a lot.
Reply With Quote Share with Facebook
  #24  
Old 11-16-2007
ralphmacey's Avatar
Member
 
Join Date: Nov 2006
Posts: 31
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
ralphmacey is on a distinguished road
You guys are great, thanks for all the help. The last question I have is what Battery Monitor would be best taking into consideration I'll have a house bank and a starting battery?
Reply With Quote Share with Facebook
  #25  
Old 11-16-2007
sailingdog's Avatar
Telstar 28
 
Join Date: Mar 2006
Location: New England
Posts: 43,291
Thanks: 0
Thanked 10 Times in 10 Posts
Rep Power: 13
sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice
If you want to monitor both banks,, get a Xantrex Link20. See this thread regarding battery monitors.
__________________
Sailingdog

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
.

Still—DON'T READ THAT POST AGAIN.
Reply With Quote Share with Facebook
  #26  
Old 11-16-2007
GeorgeB's Avatar
Senior Member
 
Join Date: Dec 2004
Location: Alameda, San Francisco Bay
Posts: 1,487
Thanks: 1
Thanked 36 Times in 35 Posts
Rep Power: 10
GeorgeB is on a distinguished road
“Magic” Explained. (Warning: I am not a licensed electrician, nor do I play one on TV. I do not have access to my notes and I’m posting from memory. I did however, use the services of a licensed engineer when I did my installation.) The stock alternator on practically all marine diesels are the standard automotive alternators (“Motorola”) that have output of around 40-50 Amps. They are internally switched (regulated) by a series of diodes. Designed to replace the relatively few amps used during the starting process, they step down to a float charge rather quickly (I recall something like 15 minutes? I think it is determined by the temperature of the alternator case?). They also use a relatively low charging voltage which is inefficient when you are charging deep cycle batteries.


The external regulator allows you to adjust both the charging voltage and the cycle time to float. For example, my Xantrex regulator is set for bulk charging at 14.5 volts and cycles over to “float” after 50 minutes. I have a temp sensor on the alternator that protects against overheating. I can even equalize (@15.5volts) my batteries using the alternator only! Gels, AGMs and deep cycle batteries all are charged using different voltages which can be programmed into the unit (that is why you do not want to mix battery types!)


Before external regulators, the mantra was to buy the largest alternator that would fit on your engine. As you can see, you can improve your charging immensely just by upping to the proper charging voltage and extending the bulk charging cycle. Big alternators are going to rob HP off of small engines. I’ve noticed a measurable increase in fuel consumption when I installed a 105 Amp alternator on my 35 HP engine. I do have a “cut off” switch on the Xantrax that can completely shut off the alternator (and let it freewheel) when I need to put all of the HP to the shaft.


One more thing… The positive wire off of the alternator to the Batts is woefully undersized. You need to up it several gauges in order improve your recharging efficiency.


I have seen people at anchorages using a Honda generator plugged into their shore power to recharge their batteries. The Achilles’ heel is their shore charger. A 20 Amp shore charger is great at your berth when you have all the time in the world to recharge. But, on the hook, you will be running that Honda for at least several hours.
Reply With Quote Share with Facebook
  #27  
Old 11-16-2007
HoffaLives's Avatar
Senior Member
 
Join Date: Feb 2007
Location: my mother's basement
Posts: 531
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
HoffaLives is on a distinguished road
A few points...If you have a proper regulator, you can't really have excessive alternator capacity. While it is true that batteries have a finite rate that they will accept a charge due to inherit aspects of their chemistry, boiling of the electrolyte occurs as a function of voltage. Excessive voltage will cause this (such as during equalisation) but a good regulator will feed the battery it's upper limit of voltage, and the battery itself determines the current draw.

The thing about battery bank size (and corresponding alternators) is that paper will show you have say 200 Ah of capacity, that is theoretical only. Batteries have internal resistance, they quickly lose max efficiencies, and there are always resistances in the circuits. In terms of actual available power to run appliances, your 200Ah bank may only be able to provide 160Ah. divide that by the 50% rule and you can see there isn't a lot there.

As for alternators, again you have resistances and power losses in the circuits, and the concern is that while motoring you won't be able to supply power at the max rate that the battery bank is able to absorb it, which isn't good for the batteries, and you can end up with an only partially charged bank when you shut down.
A good alternator means running the engine less. It's true you can't force more power into the battery than it will accept without doing damage, but most stock alternators were designed to charge the shallow-cycle starter battery only. One engineer I refer to often recommends an alternator rated about 1/3 the bank capacity. 300 Ah bank = 100amp alternator.

The circuit configuration you have now puts your alternator at risk. Use a diode isolator and connect the alternator output directly to the batteries , and switch the output of the batteries to house/start that sort of thing. Right now if someone changes the switch while motoring, you will fry your alternator. If something goes wrong with the switch (very common) you will fry your alternator.
Shows how poorly these systems are designed.
__________________
red peril
severodvinsk class russian submarine
1993
364 feet

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

our life afloat:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Share with Facebook
  #28  
Old 11-16-2007
Member
 
Join Date: Jan 2003
Posts: 74
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 12
scosch is on a distinguished road
I second the thank you for all your help. Lots of things for me to think about.
My last question. Can anyone make a real world comparison between the Micrologic (sailor's solutions) and the Link 20 battery monitors?
And, BTW, I think Jack Rabbit has the Link 20 for $305.
Reply With Quote Share with Facebook
  #29  
Old 11-17-2007
camaraderie's Avatar
moderate?
 
Join Date: May 2002
Location: East Coast
Posts: 13,877
Thanks: 0
Thanked 3 Times in 3 Posts
Rep Power: 15
camaraderie is a jewel in the rough camaraderie is a jewel in the rough camaraderie is a jewel in the rough
I just read the microlog blurb and it appears to have no ability to acually tell you amp HOUR usage and amp HOURS remaining in your battery bank....only real time use of AMPS.
If what I am reading is true...then it is missing THE most important part of the LINK systems IMHO....the ability to say " On my 500AH battery system I have now used 200 AH and at my present rate of discharge I will need to re-charge in 6 hours. "
Simple voltage and amp readings do NOT let you do this. You need an ability to tell the instrument how big your battery bank is in amp hours and it needs to provide you with a contiuous reading of how many AH's you have left and your present rate of use.
Reply With Quote Share with Facebook
  #30  
Old 11-17-2007
Here .. Pull this
 
Join Date: Jan 2007
Posts: 2,031
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
Sailormann will become famous soon enough
Quote:
So many choices, you can spend a fortune, how do you get what you need for the least cost?
It's been my experience that you just can't stop upgrading, and eventually you will own just about everything that has ever been made for a boat. So don't worry too much about what order you buy things in. Sooner or later you'll own one of each.
Reply With Quote Share with Facebook
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
battery system upgrade maestro Gear & Maintenance 3 03-01-2006 05:35 PM
Battery Bank Design Kevin Jeffrey Gear and Maintenance Articles 0 05-12-2003 08:00 PM
Battery Bank Design Kevin Jeffrey Cruising Articles 0 05-12-2003 08:00 PM
Installing a New Battery Bank Sue & Larry Gear and Maintenance Articles 0 09-26-2002 08:00 PM
Boat Battery Power East Penn Manufr. Gear and Maintenance Articles 0 01-18-1999 07:00 PM


All times are GMT -4. The time now is 04:49 PM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.