Reply
 
Thread Tools Search this Thread Display Modes
 
Old 09-21-2016, 06:39 AM   #1
4 Rivet Member
 
trekerboy's Avatar
 
1979 31' Excella 500
Charlevoix , Michigan
Join Date: Aug 2014
Posts: 286
Using 24v to get better 12v load performance?

DISCLAIMER: I'm not an electrician or an electrical engineer.

QUESTION: Can I somehow "regulate" a 24v battery bank to produce constant 12v (while keeping the bank in a 24v configuration) even under load?

BACKGROUND: In in our renovated AS we have a 4x6v battery bank wired in series-parallel for 12v. I am finding that the components I have on the 12v system are too much of a draw. For example, with 3 Fantastic Ceiling Fans going at the same time (and maybe a few other things like LED lights) the 12v system is drawn down to the 10v range which triggers low-voltage alarms on the fridge, inverter and other devices. I would just ignore the low voltage alarms but the beeping drives me crazy and I can't turn it off!

My thought was that maybe there is a device that could be between a 24v battery bank (my 6v's re-wired in series) and the 12v system that could just "add" voltage to the 12v system (from the 24v bank) as needed to maintain a set voltage whatever the load.

I think what I'm looking for is a "voltage regulator" but I've never heard or someone using one in an RV application.

Is this a bad idea for some reason?
__________________

__________________
trekerboy is offline   Reply With Quote
Old 09-21-2016, 07:18 AM   #2
4 Rivet Member
 
trekerboy's Avatar
 
1979 31' Excella 500
Charlevoix , Michigan
Join Date: Aug 2014
Posts: 286
This may be a moot point as I plan to swap my current battery bank for Lithium in the near future, but the discussion is one from which I'd still benefit.
__________________

__________________
trekerboy is offline   Reply With Quote
Old 09-21-2016, 07:27 AM   #3
2 Rivet Member
 
1974 25' Tradewind
Calgary , Alberta
Join Date: Jul 2015
Posts: 67
Quote:
Originally Posted by trekerboy View Post

Is this a bad idea for some reason?
It's a valid idea but with a 4x6 battery setup (presumably the 6v batteries are each pretty large?) you should not have a problem maintaining 12 volts. When your batteries are run down to 10 volts, they are down below about 10% charge, and you're doing them permanent damage. Lead acid batteries should not be discharged below 50% of their capacity for best life.

If you don't have one, get something like the Bogart Tri-Metric battery monitor and, after you've fully charged your batteries, measure the amp-hours that your batteries can deliver, until the system is at 12 volts. That will tell you what the available battery capacity is. You might find that it's far below what the name-plate rating of the batteries should suggest; in that case the batteries are either low on water, not sufficiently charged, and/or extended use at low charge has permanently sulfated the cells and they need to be replaced.
__________________
Alumineer is offline   Reply With Quote
Old 09-21-2016, 07:29 AM   #4
2 Rivet Member
 
1974 25' Tradewind
Calgary , Alberta
Join Date: Jul 2015
Posts: 67
Quote:
Originally Posted by trekerboy View Post
This may be a moot point as I plan to swap my current battery bank for Lithium in the near future, but the discussion is one from which I'd still benefit.
If you're planning to go with lithium then you definitely need to be aware of the system state of charge and make sure you have a properly programmed charger.
__________________
Alumineer is offline   Reply With Quote
Old 09-21-2016, 07:48 AM   #5
Rivet Master
 
lsbrodsky's Avatar
 
2012 25' FB International
Trent Woods , North Carolina
Join Date: May 2013
Posts: 1,420
There is no free lunch. Your fans and other loads require the same amount of energy whether the voltage is 12 or 24. The current is lower at 24v though. If you have taken enough energy out of the batteries to drop voltage that much, you won't change that by running the batteries in series.
But, there are dc-dc converters that take 24v and output regulated 12v although I do not see why you would want that. The advantage to your 6v batteries is that they have more amp-hour capacity than standard 12v batteries so you have something squirrely with your batteries if you have been fully charging them.
You will have a host of other issues with a Lithium system. I have just bought the hardware for the conversion and am noodling my way through that now.

Larry
__________________
lsbrodsky is online now   Reply With Quote
Old 09-21-2016, 07:59 AM   #6
4 Rivet Member
 
trekerboy's Avatar
 
1979 31' Excella 500
Charlevoix , Michigan
Join Date: Aug 2014
Posts: 286
Quote:
Originally Posted by Alumineer View Post
When your batteries are run down to 10 volts, they are down below about 10% charge, and you're doing them permanent damage. Lead acid batteries should not be discharged below 50% of their capacity for best life.
Sorry, should have been clearer... my batteries are at 100% state of charge in this scenario... For example, after I charge them with no load on the 12v system they stable voltage is around 12.8. Immediately after I turn on the fans, the system voltage drops down to something like 10.8 due to the draw of each component.

I have a Victron BMS that monitors Amps in/out to give me Percent state of charge. I can run these fans all day and night and it takes about 10% out of the battery bank every 8 hours or so.
__________________
trekerboy is offline   Reply With Quote
Old 09-21-2016, 08:00 AM   #7
Rivet Master
 
tjdonahoe's Avatar
 
2013 31' Classic
billings , Montana
Join Date: Feb 2010
Posts: 1,667
Even the reducer will use power, I am going to watch this...
__________________
tjdonahoe is offline   Reply With Quote
Old 09-21-2016, 08:00 AM   #8
4 Rivet Member
 
trekerboy's Avatar
 
1979 31' Excella 500
Charlevoix , Michigan
Join Date: Aug 2014
Posts: 286
Quote:
Originally Posted by lsbrodsky View Post
There is no free lunch. Your fans and other loads require the same amount of energy whether the voltage is 12 or 24.
I get that amps in/out don't change if you switch from 12v to 24v, I'm just talking about maintaining a higher current (i.e. 12.8v) even under load to avoid the low voltage alarms going off.

Am I missing something? Ready and waiting to learn...
__________________
trekerboy is offline   Reply With Quote
Old 09-21-2016, 08:03 AM   #9
Rivet Master
 
AnnArborBob's Avatar
 
2014 27' FB Eddie Bauer
Chelsea , Michigan
Join Date: May 2010
Posts: 1,705
Images: 12
If the little bit of load you report (i.e., three FF and a few LEDs) brings your indicated voltage down to 10 volts while under load (from presumably 12.5 to 12.7 volts resting,) your batteries themselves are likely essentially shot. With reasonably fully charged batteries, you should be able to run those devices and show a minimal voltage drop on your volt meter from the reading you get at a resting state.

Note, In my comment above, I'm not talking about reading 10 volts from your batteries in a resting state and I assume you are not as well, but rather what your voltmeter shows while the batteries are under load.
__________________
Bob Martel
WBCCI# 5766
AnnArborBob is offline   Reply With Quote
Old 09-21-2016, 08:12 AM   #10
4 Rivet Member
 
trekerboy's Avatar
 
1979 31' Excella 500
Charlevoix , Michigan
Join Date: Aug 2014
Posts: 286
Quote:
Originally Posted by AnnArborBob View Post
If the little bit of load you report (i.e., three FF and a few LEDs) brings your indicated voltage down to 10 volts while under load (from presumably 12.5 to 12.7 volts resting,) your batteries themselves are likely essentially shot. With reasonably fully charged batteries, you should be able to run those devices and show a minimal voltage drop on your volt meter from the reading you get at a resting state.
Argh, I suspected this could be the case as well (batteries shot). Had another case where the voltage drop was unexpectedly high too (see this thread). How can I confirm this? Using a hydrometer? These batteries are only 2 years old; they've been kept at full charge since I've had them (except once).
__________________
trekerboy is offline   Reply With Quote
Old 09-21-2016, 08:48 AM   #11
Full Time Adventurer
 
BoldAdventure's Avatar
 
2007 27' International CCD FB
Nomadic , USA
Join Date: Jul 2013
Posts: 2,743
If you switch to lithiums you won't have voltage drops. We have 400ah of lithiums, I can have both fans going, my computer and monitor running and still run the blender, with no dip in voltage.

This is just another reason why I skipped lead acid.

Would 24V handle loads better? Yes. But then you have to down regulate everything, so what's the point of all that effort.
__________________
Family of 4 living, working & exploring the USA in our Airstream.
OUR BLOG | FACEBOOK | INSTAGRAM
BoldAdventure is offline   Reply With Quote
Old 09-21-2016, 09:34 AM   #12
Rivet Master
 
lsbrodsky's Avatar
 
2012 25' FB International
Trent Woods , North Carolina
Join Date: May 2013
Posts: 1,420
Normally the only way you are going to be able to check battery parameters is when the battery has been resting a while. Whether you are checking voltage or specific gravity, parameters available refer to "at rest". Specific gravities are good if you have wet cells because you can check each cell and verify that they are essentially identical. Any gross variation with a cell would clearly point to a bad battery.
But, you have a lot of capacity and the kind of voltage drop you are seeing, if it is at rest, indicates bad batteries. It is meaningless to look at voltage under load. A battery shop can do a load test on your batteries, which is a way to confirm good or bad, but you have to drag the batteries over to the shop.
Larry
__________________
lsbrodsky is online now   Reply With Quote
Old 09-21-2016, 10:00 AM   #13
3 Rivet Member
 
1977 31' Sovereign
2005 30' Safari
North Port , Florida
Join Date: Mar 2007
Posts: 190
To me it also sounds like you have dead batteries. Get yourself a simple load tester. You can generally find these at any auto parts store or walmarts

https://www.walmart.com/ip/Schumache...ester/21642133
__________________
cliffcharb is offline   Reply With Quote
Old 09-21-2016, 10:51 AM   #14
4 Rivet Member
 
trekerboy's Avatar
 
1979 31' Excella 500
Charlevoix , Michigan
Join Date: Aug 2014
Posts: 286
Quote:
Originally Posted by cliffcharb View Post
To me it also sounds like you have dead batteries. Get yourself a simple load tester. You can generally find these at any auto parts store or walmarts

https://www.walmart.com/ip/Schumache...ester/21642133
Just ordered one. Thanks! I'll report back with results.
__________________

__________________
trekerboy is offline   Reply With Quote
Reply

Tags
12v


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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Which would you rather? Better brakes, better hitch, or better wheels/tires? bjmckernan General Repair Forum 30 07-17-2016 06:47 AM
24V panel and 12V battery? timzog Generators & Solar Power 10 03-14-2012 01:44 PM
Need to convert 24V DC to 12V DC for fridge igniter bacevedo Refrigerators 6 03-12-2011 07:34 PM
12V or 24V outlet for tv John and Anne General Motorhome Topics 3 05-16-2005 12:09 PM
Thermostat - 24V or 12V Larry71 Electrical - Systems, Generators, Batteries & Solar 2 08-27-2004 06:02 PM


Virginia Campgrounds

Reviews provided by



Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 03:41 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.