Reply
 
Thread Tools Search this Thread Display Modes
 
Old 12-07-2018, 04:25 PM   #21
Guru
 
psneeld's Avatar
 
City: AICW
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 20,119
My "lesser" start battery, which I parallel with my 6 golf carts (675 amp hours) died before the big bank, but it was a Walmart special that lasted 6.5 years.
__________________
Advertisement

psneeld is offline   Reply With Quote
Old 12-07-2018, 04:49 PM   #22
Guru
 
kchace's Avatar
 
City: Brookline, NH
Country: USA
Vessel Name: Blue Heaven
Vessel Model: Albin 43 classic double cabin, twin 135 Lehmans
Join Date: Sep 2013
Posts: 1,629
If 2 higher capacity batteries are paralleled with 2 lower capacity batteries but of the exact same chemistry, the batteries will not know the difference. Since all 4 batteries should share the load equally the lower capacity batteries will "run out" of power before the higher capacity batteries. The numbers will not be exact since the lower capacity batteries will have lower output voltage before the higher capacity batteries so the higher capacity batteries will slowly share more of the load as the drawdown continues. But the net result will still be that the lower cap batteries will end up getting drawn down more deeply than the higher cap ones. As long as the higher cap batteries are in parallel with the lower cap batteries the charging will happen correctly, though if combined, the lower cap batteries will likely be charged sooner.

If possible, you could use a 1, 2 battery switch and split the charging with a multi bank charger for more efficiency during charge.

Frankly, I wouldn't bother with the L16s because you would not be able to realize the full amount of their increased capacity.

Ken
__________________

kchace is offline   Reply With Quote
Old 12-07-2018, 04:52 PM   #23
Senior Member
 
Ka_sea_ta's Avatar
 
City: Puget Sound
Country: USA
Join Date: Jun 2016
Posts: 443
Quote:
Originally Posted by ben2go View Post
The lesser batteries will bring all other batteries down to their charge capacity. When recharging, the lower capacity batteries will stop the higher capacity batteries from reaching a full charge.

I believe that to be wrong unless there is a temperature sensor on the charger. As the internal resistance of the smaller capacity battery rises as it accepts a charge, ohms laws states that the voltage will increase meaning that the smaller capacity battery will be at a higher potential than the larger bank.... However since the smaller bank and the larger bank are parallel the smaller bank will actually assist in charging the larger bank until the internal resistance of the banks are in equilibrium...



If there is temperature feedback on the charge circuit I could understand how the smaller bank could limit the charge current to the larger bank resulting in a less then complete charge...


another question is what happens if you increase the number of GCs to equal the ampacity of the l16s so effectively you have 2 450 amp hour banks in parallel
Ka_sea_ta is offline   Reply With Quote
Old 12-07-2018, 09:46 PM   #24
Guru
 
City: Fairport
Country: United States
Join Date: Jan 2017
Posts: 1,716
Quote:
Originally Posted by Ka_sea_ta View Post
I believe that to be wrong unless there is a temperature sensor on the charger. As the internal resistance of the smaller capacity battery rises as it accepts a charge, ohms laws states that the voltage will increase meaning that the smaller capacity battery will be at a higher potential than the larger bank....l
Internal R reduces as the charge state increases.

Ohms law?? It is not the R, which is increasing with charge, it is the Voltage "source" of the cell that is increasing. This can be proven by these so-called "SoC" charts that simply use open circuit voltage to drive a % of charge meter. The Amperage thru the cells need to be close to zero to make this sorta-valid. If I = zero, then the internal R is a non-player, since no V drop occurs.

But, somehow, your assessment of the original assumption is true.

The "big battery" and the "small battery" don't see each other. They see the charger voltage. If there is some thermal sensor, which reduces V at the charger output, all batteries are equally affected, with the charge current thru each proportional to their respective sizes. "Sizes" not being the size/weight, but their internal R.
diver dave is offline   Reply With Quote
Old 12-08-2018, 12:04 AM   #25
Guru
 
ben2go's Avatar
 
City: Upstate,SC
Country: USA
Vessel Name: Dutch Barge Caroliner
Vessel Model: Selway-Fisher 45' Teign Luxe Motor
Join Date: May 2012
Posts: 2,625
Quote:
Originally Posted by Ka_sea_ta View Post
I believe that to be wrong unless there is a temperature sensor on the charger. As the internal resistance of the smaller capacity battery rises as it accepts a charge, ohms laws states that the voltage will increase meaning that the smaller capacity battery will be at a higher potential than the larger bank.... However since the smaller bank and the larger bank are parallel the smaller bank will actually assist in charging the larger bank until the internal resistance of the banks are in equilibrium...



If there is temperature feedback on the charge circuit I could understand how the smaller bank could limit the charge current to the larger bank resulting in a less then complete charge...


another question is what happens if you increase the number of GCs to equal the ampacity of the l16s so effectively you have 2 450 amp hour banks in parallel
You may be right. When we would add newer higher capacity batteries into our equipment, they would get pulled down to the level of the old batteries. I have seen new batteries hold 13.5 to 13.8 volts and after being paired with older lesser capacity batteries at 12.5 to 12.8 volts, it didn't take long before the batteries developed a set and wouldn't full charge. All I have ever dealt with for any extended length of time (years) were flooded Trojan brand with paired charger. I have dealt with other batteries in vehicles, aircaft, and boats but not like I did in our equipment. I had my hands on those batteries multiple times a day for over five years. I saved many of them by swapping them around and matching capacities and voltages. I usually did that when one or more battery would go dead. It kept the new ones from dying faster. The place I worked for was cheap and didn't want to take care of the equipment.
__________________
What a pain in the transom.

ben2go is offline   Reply With Quote
Old 12-08-2018, 09:30 AM   #26
Veteran Member
 
Nepidae's Avatar
 
City: Essington, PA.
Country: USA
Vessel Name: Nepidae
Vessel Model: Albin 43 Sundeck
Join Date: Jul 2013
Posts: 79
Giving you a complete answer is difficult as you didn't provide any additional info as to how you plan on charging, maintaining and monitoring your new system.

I'm not sure and don't know if the L16's you are planning on are wet cell or AGM. GC batteries are usually wet cell.

You also don't provide any info on your boat size.

And you don't mention your charging and inverter setup.

I had a house bank put in our boat in '16. Previous to that we had 2 4D wet cell batteries which we used, not very well, for house & engine with a 3 way switch to utilize the batteries.

The new house bank is 6 L16 6V AGM batteries. These batteries are very heavy and I was able to remove a set of 'day tanks' that were in the bottom of the bilge and put the batteries there, low center of gravity. After these were put in I also needed to upgrade the charging system. The OEM alternators (alts) did not have the output to handle this new load. New Balmar alts 120A were put in. This also required 2 (twin engines) new regulators, duo-chargers and a centerfielder (all Balmar). The centerfielder controls where the power goes. Whether to the house or engine bank.

As I said I also kept the 2 4D wet cell batteries, which were utilized as an engine bank.

Our Xantrex, SW3012 charger/inverter has a 3 way charging system which is very important in properly maintaining your new intended battery banks. I set the charging profile to AGM as they were the most valuable part of the system of batteries. This meant that the wet cells were not being charged properly. In this instance I knew that and knew I would be swapping out the wet cell shortly, which I did at the beginning of this year.

Any charger you have should be able to Bulk, Absorb & Float charge your batteries.

A good inverter should be part of your setup. An expenditure on a good battery bank can only be utilized with a good inverter. Our Xantrex also has a control panel which enables us to 'see' exactly what's going on with the charging and discharging of our house (L16) battery bank. I am adding a separate monitoring system for the engine bank.

I would agree, with some of the posters, that combining, in a single bank, is NOT a good idea.

So, if you'd like to contact me off-forum I'd be glad to further discuss what I've done and how it could be applicable to you.
Nepidae is offline   Reply With Quote
Old 12-08-2018, 10:04 AM   #27
Guru
 
twistedtree's Avatar
 
City: Gloucester, MA
Country: USA
Join Date: Jan 2013
Posts: 4,961
I agree with Ski.


- Batteries in series need to be of the same type AND capacity.


- Batteries in parallel need to be of the same type so that the charging parameters are the same.


The only issue I can see is that once the battery voltage reaches the bulk/absorb voltage, I think the smaller cells may reach full charge and minimal acceptance current sooner than the larger cells. Then the smaller cells will be held at bulk/accept voltage until the larger cells reach full charge. The result is that the smaller cells might be held at accept voltage longer than necessary. That said, I don't think it's a big deal.


So given the choice of


1) a smaller bank made up of one size cell


2) two separate banks that need to be managed


3) Once larger combined bank


I'd pick #3.
__________________
www.MVTanglewood.com
twistedtree is offline   Reply With Quote
Old 12-08-2018, 01:07 PM   #28
Guru
 
djmarchand's Avatar
 
City: Litchfield, Ct/Punta Gorda, Fl
Country: USA
Vessel Model: Atlas Pompano 23
Join Date: Aug 2012
Posts: 4,884
This has been an interesting and unfortunately typical thread. I stopped following it a week ago and just now checked on it.

What you have are five sources of information:

1. Pure unadulterated dock talk. Frankly in my experience it is at least half wrong.

2. Opinions, supported by the poster's own experience. But one or two samples does not make a trend. In many of these one off samples, there were other just as likely causes.

3. Opinions, supported by some engineering reasoning but based on a misunderstanding of the scientific or engineering principles which makes it worthless.

4. Opinions, supported by sound engineering and reasoning.

5. Opinions, by a a recognized expert like Steve D'Antonio or Nigel Calder.

I tend to pay attention to the last two and ignore the rest.

How do you separate fact from fiction if you ask a question and are basing how you operate your boat or buy a new piece of equipment on the answer?

David
__________________

djmarchand is online now   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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





All times are GMT -5. The time now is 07:05 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012
×