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Old 07-27-2016, 11:59 AM   #21
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When I re-did my system, I added an easy-to-find big knife switch, as a fast way to disconnect all batteries (4 Trojan T-105s). I also like to use those big fuses that the car stereo enthusiasts prefer.
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Old 07-27-2016, 12:34 PM   #22
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Quote:
Originally Posted by lewster View Post
......

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!!!
Lewster, so I understand this correctly, your referring to the two batt to batt jumper cables not the POS & NEG battery post to the converter (or what ever is under our bed before the converter) cables, is that correct.

AS as it stands now, I need to have a fuse sized to the 6AWG capacity and when I upgrade to the 2/0 the size fused to that capacity.

It finally kicked in...the 30-300A is the terminal that accepts 30A to 300A sized blade(?) fuses.

Thanks

Bob
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Old 07-27-2016, 12:41 PM   #23
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How are your batteries connected?

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Originally Posted by CruizinDux View Post
Lewster, so I understand this correctly, your referring to the two batt to batt jumper cables not the POS & NEG battery post to the converter (or what ever is under our bed before the converter) cables, is that correct.

AS as it stands now, I need to have a fuse sized to the 6AWG capacity and when I upgrade to the 2/0 the size fused to that capacity.

It finally kicked in...the 30-300A is the terminal that accepts 30A to 300A sized blade(?) fuses.

Thanks

Bob

CORRECT!!!

You can always use a smaller capacity fuse (like a 50A MRBF on a 2/0 cable but not a larger fuse on a smaller capacity cable (200A MRBF on a 6AWG cable).
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Old 07-27-2016, 01:59 PM   #24
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All battery manufacturers recommend wiring the load cables at opposing ends of any battery bank that includes multiple units.

This assures that all of the cells participate EVENLY in both charge ad discharge cycles.
Wiring other than your recommendation must cause one battery to recognize a different resistance to the load than the other, although I wouldn't think it significant unless one battery was some distance from the other. I think I would need to be a designer of batteries to fully understand the charge/discharge differences that are said to occur, but I don't want to go that deep The differing opinions and useful information that turn up on the Forum are what make it so interesting. Thanks for the insight.
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Old 07-27-2016, 05:31 PM   #25
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Originally Posted by lewster View Post
CORRECT!!!

You can always use a smaller capacity fuse (like a 50A MRBF on a 2/0 cable but not a larger fuse on a smaller capacity cable (200A MRBF on a 6AWG cable).

Thanks!


Lewster if this is your business, I'd be glad to call directly as a customer.

One last question. This winter I'm dropping the bottom of the batt box so I'll be ready for the new 2X6v's when the 2x12v's become terminal.

Can I stay with the 2 new 2/0' jumpers or should I plan for the future. And carrying that forward, you recommend up sizing the cables entering the trailer (to the bus bar?). I presume they should match the 2/0 (or higher depending on the answer prior) jumpers?

I have a 30 a service line & 1 ac and think my panel is 30A
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Old 07-27-2016, 08:38 PM   #26
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Lewster has it right. As an electrical engineer, I can add a little insight into this. Battery interconnects, whether the size of the main feeds or not, provide some resistance to current. That resistance causes voltage drop when current is passed through it.

If the feeds are connected to battery #1, some power sourced by battery #2 will be lost due to that resistance. Thus battery #1 will support more of the load. And during charging phase, battery #2 will see less voltage, and possibly less charge.

Thus, over time, battery #1 will be doing more of the work to provide power to the rig.

Arranging the feeds so that positive goes to one end of the parallel bank, and negative to the other end of the bank, equalizes the interconnect resistances seen by each battery in the bank, thus equalizing the voltage drops in the bank. Then, each battery contributes equally to satisfying current demand.


Quote:
Originally Posted by WGreg View Post
Wiring other than your recommendation must cause one battery to recognize a different resistance to the load than the other, although I wouldn't think it significant unless one battery was some distance from the other. I think I would need to be a designer of batteries to fully understand the charge/discharge differences that are said to occur, but I don't want to go that deep The differing opinions and useful information that turn up on the Forum are what make it so interesting. Thanks for the insight.
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Old 07-27-2016, 11:58 PM   #27
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Thanks everyone, This has been a great education and has been very helpful.

I truly appreciate the depth of the knowledge.

Bob
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Old 07-28-2016, 04:18 AM   #28
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. . .
Arranging the feeds so that positive goes to one end of the parallel bank, and negative to the other end of the bank, equalizes the interconnect resistances seen by each battery in the bank, thus equalizing the voltage drops in the bank. Then, each battery contributes equally to satisfying current demand.
Thanks steverino. To clarify one further aspect of this set up -- if one removes the Negative-to-Negative jumper cable between the two batteries, does this isolate the batteries from all loads, including:

-- the tongue jack motor connected directly to a Positive terminal, and grounded to the chassis;
-- the parasitic loads like the propane detector and sub-woofer which some folks have; and
-- storage area lights which might have been left on accidentally?

It seems to this lay mind that the missing negative jumper would prevent any 12-volt use. Or have I missed something?

Thanks,

Peter
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Old 08-04-2016, 04:37 PM   #29
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Ice cube fuse connection

Lewster is recommending a MRFB Ice cube fuse on the hot to the trailer. My question is it acceptable to cut off the regular Battery connection that connects to the post and use the bolt connection?

Dave
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Old 08-04-2016, 07:36 PM   #30
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Quote:
Originally Posted by steverino View Post
Lewster has it right. As an electrical engineer, I can add a little insight into this. Battery interconnects, whether the size of the main feeds or not, provide some resistance to current. That resistance causes voltage drop when current is passed through it.

If the feeds are connected to battery #1, some power sourced by battery #2 will be lost due to that resistance. Thus battery #1 will support more of the load. And during charging phase, battery #2 will see less voltage, and possibly less charge.

Thus, over time, battery #1 will be doing more of the work to provide power to the rig.

Arranging the feeds so that positive goes to one end of the parallel bank, and negative to the other end of the bank, equalizes the interconnect resistances seen by each battery in the bank, thus equalizing the voltage drops in the bank. Then, each battery contributes equally to satisfying current demand.

steverino, I missed this earlier. Great explanation...thanks! Now I understand the upsizing need for the interconnects.

Bob
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Old 08-04-2016, 10:53 PM   #31
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Lewster is recommending a MRFB Ice cube fuse on the hot to the trailer. My question is it acceptable to cut off the regular Battery connection that connects to the post and use the bolt connection?

Dave
No problem!!!

The batteries that I use never have an automotive style post on them, so all of my battery connections are made to either a mounting stud protruding from the battery or in almost all cases, with a bolt provided by the battery manufacturers that connects a solid copper battery lug to the terminals.

And remember.......NO WING NUTS!!!!

ABYC will not allow the use of any wing nut with the exception of trolling motor use and then, a wire size limit of 8AWG.
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Old 08-04-2016, 11:59 PM   #32
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Yeah, I've never seen a torque wrench that fits a wing nut....


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Old 08-07-2016, 01:40 AM   #33
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How are your batteries connected?

Lew, how do you keep the MRBF fuse terminal from corroding from acid seepage on golf cart flooded batteries? Just got them today. No instructions of course. 😀

Grease? The red battery terminal waxy spray stuff? Or something else.

Or are these things acid proof?


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Old 08-07-2016, 07:20 PM   #34
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Lew, how do you keep the MRBF fuse terminal from corroding from acid seepage on golf cart flooded batteries? Just got them today. No instructions of course. 😀

Grease? The red battery terminal waxy spray stuff? Or something else.

Or are these things acid proof?


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I don't usually use flooded batteries, but back when I did many battery service jobs, I would use Boeshield T-9 as a vapor resistant covering. I really HATE that red stuff!! It doesn't do the job and gets all over anything it touches.

T-9 dries to a waxy finish that does a much better job. Once your connections are made.....saturate the area, wait 15 minutes and do it again. Should form a nice corrosion shield

The other product that I use is called.....Corrosion Block. Got it at NAPA. It is made to protect items in a marine environment from corrosion, and I have used that successfully as well. It stays sort of sticky, until T-9 but also works!
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Old 08-07-2016, 09:38 PM   #35
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Thanks Lew. Only thing I had was the red stuff. It's a total mess, and didn't do the job. I was half-tempted to break out the Vaseline or axle grease. We both know what a mess they make.

Didn't think of the Boeshield T-9. Which is really dumb. Retired from Boeing a couple years ago, but didn't build airplanes....

I get to replace a nicely boiled set of batteries soon. Yes, the new convertor is going in FIRST. Grumble. Plus a battery watering system to make it easier, a disconnect switch, better cables, etc.

Yes, I have been listening to you! And I greatly appreciate the knowledge you freely share.


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Old 08-07-2016, 10:00 PM   #36
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Originally Posted by rmkrum View Post
Thanks Lew. Only thing I had was the red stuff. It's a total mess, and didn't do the job. I was half-tempted to break out the Vaseline or axle grease. We both know what a mess they make.

Didn't think of the Boeshield T-9. Which is really dumb. Retired from Boeing a couple years ago, but didn't build airplanes....

I get to replace a nicely boiled set of batteries soon. Yes, the new convertor is going in FIRST. Grumble. Plus a battery watering system to make it easier, a disconnect switch, better cables, etc.

Yes, I have been listening to you! And I greatly appreciate the knowledge you freely share.


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Old 08-14-2016, 02:22 PM   #37
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Thanks steverino. To clarify one further aspect of this set up -- if one removes the Negative-to-Negative jumper cable between the two batteries, does this isolate the batteries from all loads, including:

-- the tongue jack motor connected directly to a Positive terminal, and grounded to the chassis;
-- the parasitic loads like the propane detector and sub-woofer which some folks have; and
-- storage area lights which might have been left on accidentally?

It seems to this lay mind that the missing negative jumper would prevent any 12-volt use. Or have I missed something?

Thanks,

Peter

Peter, not sure if you saw this or not, but it appears that you're well grounded...


http://www.airforums.com/forums/f449...ml#post1835202

I may rethink my planned disc switch as the not is a much easier solution

B
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Old 08-14-2016, 02:49 PM   #38
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Thanks Bob.
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Old 08-15-2016, 09:25 PM   #39
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I may rethink my planned disc switch as the not is a much easier solution

B

ooops...as the NUT is a much easier solution.

Man I'm tired.
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