Reply
 
Thread Tools Display Modes
 
Old 05-04-2009, 05:36 PM   #1
Senior Member
 
mjeffrey's Avatar
 
Join Date: Feb 2009
Location: Monroe, WA
Posts: 310
Battery separators: uni-directional or bi-directional?

Hello!

(Funnily enough, searching for 'uni-directional' tells me that the term searched for is too common, and is thus ignored! So apologies if this has been gone over before.)

Wondering whether a battery separator should be uni- or bi-directional. A quick overview, as we would use them:

- uni-directional will charge the house battery from the alternator, once the starting battery is charged
- bi-directional will do the above, and also charge the vehicle battery from any other charging source (ie. solar) once the house battery is charged

My concern about bi-directional - when the house battery is charged, the separator will parallelize it with the starting battery. Is there any chance of damaging the house battery when doing this (such as sudden discharge of house battery into starting battery, if the starting battery is low)? Will having these two batteries in parallel confuse a charger, so that it sends too much current into the house battery? I don't have a perfect understanding of how chargers read battery state when there are 2+ charging sources and/or 2+ batteries!! I do know that any authority on batteries recommends against hooking up 2 different batteries in parallel, but this is usually relating to permanent battery bank connections.

SMB seems to use a bi-directional, btw. The Sure Power 1315, I believe.

The advantage of bi-directional, for my purposes, is that I wouldn't have to rewire the stereo and accessory sockets to run off of the house battery.

Cheers!
Mike.
__________________

mjeffrey is offline   Reply With Quote
Old 05-04-2009, 08:53 PM   #2
Site Team
 
Ford_6L_E350's Avatar
 
Join Date: May 2007
Location: Washington - Ridgefield
Posts: 4,725
Re: Battery separators: uni-directional or bi-directional?

Yes, our battery separators are bi-directional. But, don't worry about it. The losses in the wiring and separator will prevent battery damage, even if you ran the starting battery down trying to start the engine. Or, even if you ran down the house batteries with the microwave and then started the engine to recharge.

Charging batteries in parallel is no big deal. All the 6.0 diesel vans have two (parallel) starting batteries and many have two (parallel) house batteries. The only time parallel batteries are an issue is when one is much better than the other. Then the bad battery will pull down the good one, never the other way around.

Mike
__________________

__________________
SOLD04 EB350 Custom Floorplan
6.0 PSD 4.10 Posi
Salem Kroger coil spring 4wd
SMB Trailer w/AT Air Suspension
Alaska to Key West, Labrador and more
130685 miles 16.65 mpg average

Prostate cancer survivor. viewtopic.php?f=8&t=11099
2015 VW GTI
Leaving CA for WA
Ford_6L_E350 is offline   Reply With Quote
Old 05-05-2009, 01:05 PM   #3
Senior Member
 
mjeffrey's Avatar
 
Join Date: Feb 2009
Location: Monroe, WA
Posts: 310
Re: Battery separators: uni-directional or bi-directional?

Quote:
Originally Posted by Ford_6L_E350
Charging batteries in parallel is no big deal. All the 6.0 diesel vans have two (parallel) starting batteries and many have two (parallel) house batteries. The only time parallel batteries are an issue is when one is much better than the other. Then the bad battery will pull down the good one, never the other way around.
But starting batteries and house batteries are always the same type and size and age of battery - they're never mixed. I'm concerned about the starting battery being older, and weaker, and pulling down the (good) house battery when the separator hooks them up in parallel. With a one-way separator, they'll only be connected when the house battery is the weaker one (I'm not so concerned about my starting battery - it costs much less ).

During my searches, I pulled up the Optima site, who had this to say about separators:

"If you are using an Optima and a conventional battery, your system must charge each battery independently."

Maybe some sort of relay? Seems too complicated for me!

Cheers,
Mike.
mjeffrey is offline   Reply With Quote
Old 05-05-2009, 09:46 PM   #4
Senior Member
 
jage's Avatar
 
Join Date: Apr 2007
Location: Franktown, CO
Posts: 7,600
Re: Battery separators: uni-directional or bi-directional?

The separator only hooks them up when the voltage level reaches a certain point in the charged battery (or battery set) at which they're nearly or fully charged. You can force the separator to hook them up (manual override) for things like jump-starting the van off the house batteries for dead starters or (I can't imagine doing this) powering your microwave off the starter batteries.

The way SMB wires the separator it manual overrides whenever the key is in the Start position, that's both Diesels and Gassers, so you can effectively completely hide trashed starter batteries because they're jumped with the house each and every time... which is what happened to me.

I know my starter batteries charge when the house batteries are topped off, and the house charge while driving (you can watch the blueSky voltmeter jump when the starters are topped off), and I'm pretty sure that was true even when the starter batts were toast (of course I didn't know that until I pulled them and I wasn't putting them back after they tested bad!)

Anyway, I guess what I'm saying is I don't see where the concern is. Changing the start wire over to a manual switch solves the "always-jump-on-start" problem. Unless you're saying putting good, fully charged batteries with bad ones to be charged, during charging, ruins the good ones... is that it?

And I'd be much more concerned when the starter is the weak one... popcorn won't get you out of Death Valley.
__________________
and then
everything changed
jage is offline   Reply With Quote
Old 05-05-2009, 10:15 PM   #5
Site Team
 
daveb's Avatar
 
Join Date: May 2007
Location: Turlock Ca
Posts: 9,838
Garage
Re: Battery separators: uni-directional or bi-directional?

Mike this has come up before. I'll send you a PM on this issue. Not that I know what's correct but it's my view. Check your messages. There are several links that might be of value. If you feel it helps go ahead and post it.

Dave
__________________
2006 Ford 6.0PSD EB-50/E-PH SMB 4X4 Rock Crawler Trailer

Sportsmobile 4X4 Adventures..........On and off road adventures
daveb is offline   Reply With Quote
Old 05-06-2009, 10:03 AM   #6
Site Team
 
Ford_6L_E350's Avatar
 
Join Date: May 2007
Location: Washington - Ridgefield
Posts: 4,725
Re: Battery separators: uni-directional or bi-directional?

My SMB doesn't have the 'Connect on Start' hooked up. I've never needed it and don't plan to hook it up.

Before one set of batteries could pull down the other set, the seperator would disconnect. It only connects when one set is charge fully, and disconnects when the voltage comes down. Unless it fails in the 'connected' position, no damage to the good batteries could occur.

Mike
__________________
SOLD04 EB350 Custom Floorplan
6.0 PSD 4.10 Posi
Salem Kroger coil spring 4wd
SMB Trailer w/AT Air Suspension
Alaska to Key West, Labrador and more
130685 miles 16.65 mpg average

Prostate cancer survivor. viewtopic.php?f=8&t=11099
2015 VW GTI
Leaving CA for WA
Ford_6L_E350 is offline   Reply With Quote
Old 05-06-2009, 11:52 AM   #7
Senior Member
 
mjeffrey's Avatar
 
Join Date: Feb 2009
Location: Monroe, WA
Posts: 310
Re: Battery separators: uni-directional or bi-directional?

Quote:
Originally Posted by Ford_6L_E350
Before one set of batteries could pull down the other set, the seperator would disconnect. It only connects when one set is charge fully, and disconnects when the voltage comes down. Unless it fails in the 'connected' position, no damage to the good batteries could occur.
That seems to be the part I overlooked - like you say, it would prevent what I'm worried about, which is the pulling down of the good battery by the bad. Thank you!

Dave's message to me had a lot of good information, which is also contained in his blog post, here:

http://autoramblings.com/blog/?p=386

Thanks Dave for passing it along!

Cheers,
Mike.
__________________

mjeffrey is offline   Reply With Quote
Reply

Thread Tools
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

Powered by vBadvanced CMPS v3.2.3
Disclaimer:

This website is not affiliated with or endorsed by Sportsmobile SIP or any of its affiliates. This is an independent, unofficial site.


All times are GMT -6. The time now is 08:28 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
×