Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 18-09-2015, 15:52   #16
Registered User

Join Date: Sep 2013
Location: Auckland
Boat: Logan 33
Posts: 73
Re: current opinion on mixing FLA/AGM

So I accept that AGMs like to be recharged before next cycle or as soon as possible, otherwise you get less cycles in their lifetime. But, it is often quoted that you never get back to 100% while at sea. So if you realistically only get to 80-85%, are AGMs always going to perform to less than their potential? Are AGMs maybe better suited to a solar powered continual charging application like a solar powered road sign?


Sent from my iPad using Cruisers Sailing Forum
__________________

__________________
daveNZ is offline   Reply With Quote
Old 18-09-2015, 15:58   #17
Registered User

Join Date: Sep 2013
Location: Auckland
Boat: Logan 33
Posts: 73
Re: current opinion on mixing FLA/AGM

Svlamorocha, no I haven't checked the whole engine loop; but I have got a small (.2 ?) drop from alternator +ve to battery +ve so will add a direct cable (or two) soon.


Sent from my iPad using Cruisers Sailing Forum
__________________

__________________
daveNZ is offline   Reply With Quote
Old 18-09-2015, 16:07   #18
Registered User

Join Date: Jun 2009
Location: still in a roll of fiberglass around Cape Town
Boat: Leopard 40 (new model)
Posts: 1,201
Re: current opinion on mixing FLA/AGM

Quote:
Originally Posted by daveNZ View Post
But, it is often quoted that you never get back to 100% while at sea. So if you realistically only get to 80-85%, are AGMs always going to perform to less than their potential? Are AGMs maybe better suited to a solar powered continual charging application like a solar powered road sign?
You will never get to 100% if you do not have enough "surplus" between available charging Ah and consumption, but that "if" is up to you. If you have that surplus then AGMS work great with solar. You may need to run genset or engine early in the morning (when batteries are low, hence tey can accept a lot and not waste your engine/genny time) and then use solar for the tail end of the charge plus the draw during the day. The trick is that it is only in the afternoon that you will reach 100% and if you don´t then you learn that you should have run the genny/engine for longer early in the day. if your days are all the same then it is easy to work out how long to run the engine/genset in the morning.

Another point that most owners get wrong is that most chargers will switch from absorption to float based on an algorithm that is far from the real deal, which is manufacturers specified current absorbed at absorption (not float) voltage. For some AGMs this means about rated Ah capacity divided by 200 hours, or 1A for a 200Ah battery. If your charger kicks to float at capacity divided by 25 hours (ie the usual "4%" in many algorithms) then those AGMs will not last long.

By the way, FLA also get murdered that way, they are just cheaper.
__________________
svlamorocha is offline   Reply With Quote
Old 18-09-2015, 16:20   #19
Registered User

Join Date: Jun 2009
Location: still in a roll of fiberglass around Cape Town
Boat: Leopard 40 (new model)
Posts: 1,201
Re: current opinion on mixing FLA/AGM

Quote:
Originally Posted by daveNZ View Post
Svlamorocha, no I haven't checked the whole engine loop; but I have got a small (.2 ?) drop from alternator +ve to battery +ve so will add a direct cable (or two) soon.
That is not bad on the positive side (assuming you are measuring from house battery, which is what matters) but IMHO the killer is usually the negative.

In the average BVI bareboat with Yanmar/Hitachi setup the drop between alternator negative and battery negative is more than 1V (just the negative) when the alternator is pushing only 25 or 35 amps. Consider all the steps:

- Drop in wire from battery negative to negative battery switch (not bad in carter boats because this wire is fat).

- Drop across terminals negative battery switch. I have measured 0.3V once, but it got better after "exercising" the switch.

- Undersized wire from switch to Common Ground Point bolt in engine with associated rust, grease, etc.

- Terribly undersized wire between Common Ground Point and alternator.

This sounds bad and kills batteries but saves alternators. With the usual machine sensed alternator, the additional drop keeps battery voltage down , which then limits current that in turn saves the alternator from burning.

I bet that MarkJ´s alternator would not have lasted that long if he had cleaned all the connections, upgraded the wiring and connected AO direct to the house battery positive (instead of going through the cheapo relay they have in those Moorings boats, which can have 0.2V drop when old)and alt negative with fat wire direct to the switch or battery negative.

If you have one of those cheap Hitachi lookalikes without the Hitachi thermal cutback be prepared because after you improve the wiring you will increase the absorption current and that may fry the alternator. Have an extinguisher ready!
__________________
svlamorocha is offline   Reply With Quote
Old 03-10-2015, 18:54   #20
Registered User
 
BobH260's Avatar

Join Date: Aug 2009
Posts: 160
Re: current opinion on mixing FLA/AGM

We have 4 Deka AGMs (420 Ahr) in our house bank for the past 4 years and have been happy with them. We use a 5th one for a start battery on an Echo charger. Our alternator is a 140A Electromaxx with Balmar ext. regulator temp. comp., and serpentine belt kit. A Kyocera 325W Solar panel with a Rogue MPPT controller with temp. comp. A Victron battery monitor usually indicates 100% SOC by about noon each day if any sun at all. With an energy budget of about 100Ahr per day living aboard. Once we hit 100% we plug in computers etc. to capture the extra solar power.

Bob
__________________

__________________
BobH260 is offline   Reply With Quote
Reply

Tags
agm, current

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
Mixing AGM and Lead Acid batteries CSY Man Electrical: Batteries, Generators & Solar 24 17-04-2015 19:26
Switch from AGM to FLA batteries Utahsailor Electrical: Batteries, Generators & Solar 8 03-04-2015 09:03
East Coast of Fla to West Coast Fla ub1 Navigation 6 24-08-2013 19:33
Mixing Signals to External Speaker Cadence10m Marine Electronics 30 24-09-2009 13:13
Mixing 'types' of AGM batts?? John Drake Electrical: Batteries, Generators & Solar 18 13-12-2006 18:47



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 00:06.


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.