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Old 07-26-2016, 09:12 PM   #1
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How are your batteries connected?

This was originally in a thread "Introductions sub-forum....Hi from Oregon". As sometimes happens with advice, getting off topic or hijacking a thread can easily occur.

Part of the discussion was in regards to advice on dis-connecting your battery to stop parasitic draws.


Please start at my OP #13

http://www.airforums.com/forums/f368...on-154090.html

for background. My question is how is your batter connected..i.e.

Paste from # 20
As you can see in the image the OEM install was POS to street side batt and the NEG to the curb site batt.

....They had connected both POS and NEG to the street side battery and jumps to the CS batt..



the discussion and questions 1-3 from that thread is as follows.

I don't want to hijack this thread and can move to the 20 footers which allows for a wider range of discussion. Just let me know.

I realized when I started to connect my neg connection that the dealer When the dealer swamped out the jack last week, when I was disconnecting the neg as usual, I realized they had connected it differently.

As you can see in the image the OEM install was POS to street side batt and the NEG to the curb site batt.

They had connected both POS and NEG to the street side battery and jumps to the CS batt..

So questions are:
#1) is how are you all connected
#2) Is there an electrical engineering reason to connect POS & NEG to the same batt and utilize jumps to the other batt or is it better to connect POS and NEG to opposite batts, still using the jumps.
#3) does it matter as long as you don't need/want to cut off all power from the batts and so all associated parasitic draws.

I disconnected the one jumper and realized, I need to do both. Then for GP, I moved the NEG to the CS post.

I've been considering (assuming I have elevation room in the box) of adding batt disconnect...I presume at the NEG post

Thanks everyone.

bob
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Old 07-26-2016, 09:32 PM   #2
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Greetings from Oregon too!

I will take a try at question #2

It sounds as if your batteries are connected in parallel.

https://www.etrailer.com/question-21011.html

A parallel connection is ideal for an RV because it keeps the whole system at 12v. Thus drawing 12v from each battery and not turning it into a 24v system as would happen if connected in series.

https://www.reference.com/home-garde...7692ae60e1f68d

I can not speak to the shut off sylonoid or any way of getting a true "battery disconnect" system for an Airstream. I have heard other member express such a system factory wired though. Maybe they will be able to help you if they have done it themselves.

For my old SOB the only real battery killer when stored was the CO2 sensor. I managed that by pulling its fuse when stored and replacing when the trailer was in use. For my Airstream there isn't one in the factory set-up, so I have a stand alone sensor running on its own batteries

Looking at your picture, if you pulled the positive cable from the curb side battery, you would shut off your whole sytem while stored. However, you would have to reconnect to use your jack and then you also have to reset anything that required power to store info, like pre sets on a radio. I don't know if this would be the best solution, but you would have fresh batteries.
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Old 07-26-2016, 09:41 PM   #3
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Hi - here's mine. 2012 27FB Flying Cloud. I'm standing curbside taking this pic.

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Old 07-26-2016, 09:45 PM   #4
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I think both our pics have the same exact setup except for one wire. There's a wire with a yellow crimp on both of our pics - I believe that's the electric jack wired to the positive terminal. On the negative side, I have a wire with a blue crimp that isn't showing in your pic. I have to admit, I don't know where that wore goes but it is the only difference I see in our setups.
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Old 07-26-2016, 09:57 PM   #5
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How are your batteries connected?

The original pic is how a parallel battery setup should be done. Positive to #1 battery and negative to #2 battery with a cable running POS to POS and NEG to NEG. This doubles the amperage while leaving the voltage at 12VDC nominal.

My only issue with Airstream's wiring is the gauge used for both parallel cables. They use a meager 6AWG.

I NEVER use smaller than 2/0 for inter battery connections. I can assure you that even inside the lowly Interstate batteries, the individual cell inter-connect busses are far heavier than a measly 6 AWG!!!
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Old 07-26-2016, 10:20 PM   #6
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So, if the positive going to the trailer is disconnected (red in upper left of both pictures), the jack works, but the parasitic loads in the trailer have no power to drain. Correct or wishful thinking?

Lewster - Just the two parallel connects would be changed to 2/0 and not the cable to the trailer. Correct or wishful thinking?

Thanks for the help. Pat
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Old 07-26-2016, 10:33 PM   #7
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Quote:
Originally Posted by PKI View Post
So, if the positive going to the trailer is disconnected (red in upper left of both pictures), the jack works, but the parasitic loads in the trailer have no power to drain. Correct or wishful thinking?
Probably correct. I didn't catch that the first time.
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Old 07-26-2016, 11:27 PM   #8
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Following this thread.

Mike
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Old 07-26-2016, 11:36 PM   #9
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Quote:
Originally Posted by PKI View Post
So, if the positive going to the trailer is disconnected (red in upper left of both pictures), the jack works, but the parasitic loads in the trailer have no power to drain. Correct or wishful thinking?

Lewster - Just the two parallel connects would be changed to 2/0 and not the cable to the trailer. Correct or wishful thinking?

Thanks for the help. Pat
When I do battery upgrades, I also upgrade the size of the cables entering the trailer. Again, 6AWG is not what I consider appropriate for anything over a 40-50 amp DC draw.

Batteries can short and carry far more current than that, and I have had to re-wire trailers where the circuit breakers fused after shorting, making the 8 or 6AWG cabling essentially a welding rod!

I'm not a fan of Airstream's cheap DC breakers found in the DC positive bus bar either, as I prefer that an MRBF (Marine Rated Battery Fuse) be placed on the positive battery terminal with the amperage rating to match the cabling used. https://www.bluesea.com/products/519...k_-_30_to_300A.

In essence, you can leave the 6AWG cabling in place unless you are doing a bunch of re-wiring thru the floor hole located just below your bus bars inside the front of the trailer, as the great majority of your internal DC loads are far less than that value. I would definitely place a 50 amp MRBF on the positive battery terminal though!
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Old 07-26-2016, 11:46 PM   #10
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Lewster, that clarifies a bunch. Installing fuse protection is the ticket. Thanks! Pat
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Old 07-27-2016, 02:14 AM   #11
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Lewster, if you have time, could you also confirm that disconnecting the NEG to NEG #6 cable will take the batteries off-line for all draws, including the parasitic ones? I believe you have also recommended an aftermarket marine hard disconnect to accomplish this. [Noted from other threads, however, that even a hard disconnect will not prevent battery discharge over the long term.]

Thanks for the MRBF link also. Looks easy enough to install.

Thanks,

Peter
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Old 07-27-2016, 06:54 AM   #12
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There's some great info in tnis thread! Thanks.
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Old 07-27-2016, 09:09 AM   #13
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I don't believe it matters electrically to which battery each of the two load cables are connected so long as the two batteries are paralleled and the paralleling jumpers are at least the size of the load cables. The addition of fuse protection at the positive battery per Lewster is a good idea.
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Old 07-27-2016, 09:42 AM   #14
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Quote:
Originally Posted by SteveSueMac View Post
I think both our pics have the same exact setup except for one wire. There's a wire with a yellow crimp on both of our pics - I believe that's the electric jack wired to the positive terminal. On the negative side, I have a wire with a blue crimp that isn't showing in your pic. I have to admit, I don't know where that wore goes but it is the only difference I see in our setups.
SteveSueMac, I agree other than your blue wire off the curbside POS our are the same.

Thanks

Bob
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