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Topic: Heavy Duty Battery Disconnect (Read 1452 times) previous topic - next topic

Re: Heavy Duty Battery Disconnect

Reply #25 –
Quote from: Barry & Cindy –
You are probably ok, but there are bus bar amp web pages if you need rating info.

I think switch is ok for house battery bank as 100 amps is a lot of draw for house bank, except when starting with boost switch on.

But start bank is different story when hundreds of amps are needed to start with a cold battery.

But as long as you don't have a starting problem with the switch installed, you are ok.

I found this rating chart, but it was for copper. Electrical Bus Bar Ampacity Chart
Copper Busbar Ampacity Tables
Barry,
The model Cole Hersee battery disconnect is rated for 2,000 amps intermittent (30 seconds), 300 amp continuous.
Battery-Related Products | Master Disconnect Switches | Single Pole Master
Peter & Beth Martin
No Forrest? What have you done?
MC# 15890 until Dec 2016; FMCA #F329677
Cincinnati, OH

Re: Heavy Duty Battery Disconnect

Reply #26 –
Peter, I read the chart that Barry added, you would need the 3/8" X 1 " bar to get the needed MCM rating, I would go with a wider bar like 1.25" if that would fit your setup.
Need to mention, make real sure nothing can get to it as a short, you will have more excitement than you ever had.
Good Luck
Dave M

Re: Heavy Duty Battery Disconnect

Reply #27 –
Dave, I hear you about the excitement part.  I was thinking of going with a 1/2" by 1" bar 2" long.  That should more than cover it for both battery banks.

Here's the stock & price for the minimum 12" length:

Copper Bar Alloy C11000 for Electrical Bus Bar Applications

Peter & Beth Martin
No Forrest? What have you done?
MC# 15890 until Dec 2016; FMCA #F329677
Cincinnati, OH

Re: Heavy Duty Battery Disconnect

Reply #28 –
Buy a 1-0 or 0-0 crimp-able connector and whack the crimp-able end flat with a hammer. It will already have a hole in one end, drill one in the other. If it won't overheat as a cable end, it won't overheat as a bus bar. If you want to be certain, buy two, whack 'em and stack 'em...
The selected media item is not currently available. Dave Head & Megan Westbrook
Titusville, FL - The Great Outdoors
'98 270 buying this month
Toad is a 2018 F150 XLT

Re: Heavy Duty Battery Disconnect

Reply #30 –
Peter,

The obvious issue is starter inrush amperage. 

Were it me, I would consider determining if there is any "at rest" draw from the large-gauge wire to the starter.  If not, leave that wire in place and use your switch for all other circuits.  That would give you the "no draw" you desire, but not run that huge in rush amperage through the  switch/bar.

If you coach is not presently wired for the above, consider doing it!

Brett
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Heavy Duty Battery Disconnect

Reply #31 –
Quote from: wolfe10 –
Peter,

The obvious issue is starter inrush amperage. 

Were it me, I would consider determining if there is any "at rest" draw from the large-gauge wire to the starter.  If not, leave that wire in place and use your switch for all other circuits.  That would give you the "no draw" you desire, but not run that huge in rush amperage through the  switch/bar.

If you coach is not presently wired for the above, consider doing it!

Brett
Brett,
I think the wiring from the positive side of the battery is wired that way.  I was thinking of installing the switch at the negative ground post.  Does it make any difference where the disconnect is installed?
Peter & Beth Martin
No Forrest? What have you done?
MC# 15890 until Dec 2016; FMCA #F329677
Cincinnati, OH

Re: Heavy Duty Battery Disconnect

Reply #32 –
Peter,

Makes no difference whether positive or ground is disconnected in terms of sparing the battery from discharging.

But my thought was to install the disconnect on the positive for all BUT the engine start cable.  That should remove all the loads (again confirm) but NOT run the high amp start load through the switch.

Brett
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Heavy Duty Battery Disconnect

Reply #33 –
Great idea to isolate the start cable and not switch it.

Our starter solenoid battery cable post is a common connection point with other positive cables maybe leading to isolator, boost solenoid and other stuff.

In our case, a battery positive switch that did not cut off starter would also not cut off some draining loads.

Re: Heavy Duty Battery Disconnect

Reply #34 –
Quote from: wolfe10 –
Peter,

Makes no difference whether positive or ground is disconnected in terms of sparing the battery from discharging.

But my thought was to install the disconnect on the positive for all BUT the engine start cable.  That should remove all the loads (again confirm) but NOT run the high amp start load through the switch.

Brett
Understood...The Cole Hersee 75908 switch is rated for 2000 amps for 30 sec. & 300 amps continuous.  I think I'm safe with that switch (I only have two 800 CCA start batteries & two 8D8G Deka's for the coach).  I'm thinking of the 1/2" x 1" copper bus bar to fabricate the connector to the battery terminal from the switch.

Am I still in jeopardy for a melt down?  I don't know how high the amp draw can really get under weird circumstances?
Peter & Beth Martin
No Forrest? What have you done?
MC# 15890 until Dec 2016; FMCA #F329677
Cincinnati, OH

Re: Heavy Duty Battery Disconnect

Reply #35 –
Quote from: Barry & Cindy –
Great idea to isolate the start cable and not switch it.

Our starter solenoid battery cable post is a common connection point with other positive cables maybe leading to isolator, boost solenoid and other stuff.

In our case, a battery positive switch that did not cut off starter would also not cut off some draining loads.
Barry,
For edification, you do have parasitic loads from your positive cable to the starter when ignition is off?
Peter
Peter & Beth Martin
No Forrest? What have you done?
MC# 15890 until Dec 2016; FMCA #F329677
Cincinnati, OH

Re: Heavy Duty Battery Disconnect

Reply #36 –
If the starter is the common point for other circuits, can you relocate that/those wires to the new battery disconnect switch-- really shouldn't be that tough to leave the positive start cable and isolate the other circuits (assuming no draw when only the starter cable is connected and others relocated to your new switch).
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Heavy Duty Battery Disconnect

Reply #38 –
We probably have some small drains on our start battery when ignition is off, Peter.

We now use a BlueSea smart battery combiner that connects start & house banks together when house is being charged by solar or battery charger. The combiner disconnects when ignition is on and when battery voltage drops below 13 volts.

We are very happy using the BlueSea to keep our start battery bank under charge. It even has a LED inside our coach that tells us combiner status.

Our docking lights are factory wired to our start battery bank and use many amps when on.

Last year we switched our rectangular sealed docking lamps to LED versions that use fewer amps, but still draw a bunch.

Even though our Cummins C-8.3 engine does not need it, we still added a 3rd RedTop start battery because there was space in the battery tray. Nothing like a little reserve starting power to help make our day.

Barry