It's not a real pain to physically disconnect the ground terminals from the start & coach batteries every time I go to the coach storage facility. But, it's getting to me after 8 years. I need some input on the selection and installation of two heavy duty battery disconnects, one for the two start (Optima Red Top Group 34's) and another for the two coach batteries (Deka Gel 8D's).
Can the attached link's disconnect be mounted to the battery's terminal? Or, does it have to be mounted to a wall, then route the ground cable to the unit & from the unit to the battery negative ground terminal?
Amazon.com: Moroso 74101 Heavy-Duty Battery Disconnect Switch: Automotive (http://www.amazon.com/gp/product/B000CON4MA/ref=pd_lpo_k2_dp_sr_1?pf_rd_p=486539851&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B001BONXGM&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=1JK8NWMXPDBZA4F5M2P9)
Thanks,
Peter
I have found the Cole Hersey products for battery disconnect to work fine, so here is the general catalog, just scroll down to battery products. They seem to be the only disconnects used on fire trucks, a manual rotary type.
Part # 75908 is rated 2000 A / 300 A continuous.
Catalogs | Cole Hersee - Littelfuse (http://www.colehersee.com/home/catalogs/)
Dave M
I second that. We would only use Cole Hersey products when I was in the municipal fleet world. Put them on all emergency and marine equipment and anything else that needed their items. Cannot remember any of their switches failing.
Keith
See below. I got these at Camping World. They have several models, so be sure to get the right one if you go this route. They have worked fine for the house batteries. I only needed one, but ended up with three.... it took me awhile to figure out how to install them. But with three I can isolate each battery if need be. I think they cost in the $25 range.
Thanks for the input. I located the switch with the rating I think will work well for the start & house batteries, although I think it may be overkill for the house batteries. But what the heck. Here they are:
Master Disconnect Switch, 75908, Cole Hersee (http://www.ryderfleetproducts.com/ryder/af/ryder/core/content/product/srm/key/V30%2075908/pn/Master-Disconnect-Switch/erm/productDetail.do)
Now all I need is to figure out how to mount these things in the battery bay and the engine compartment.
Peter
Peter,
Remember that the engine must not be running when you disconnect the batteries. Disconnecting with the alternator charging will immediately damage the alternator diodes.
Keith
Yes indeed. My shutdown procedure once in the storage slip won't be altered much. It will just be faster without having to get out the wrench and removing the ground terminals from the battery banks.
Peter
Peter,
Assume you have no 120 VAC where you store it and that you are indoors so solar panels won't work.
Those are choices #1 and #2 with complete disconnect being #3.
Brett
Brett,
I have no available AC power other than the 8Kw coach generator. And yes, the roof does kill the idea of a solar charger (which would be my personal preference). I have not encountered any problems with the disconnect process. The Cummins C8.3 is a mechanical engine. And, I don't really know how the disconnect affects the Allison transmission. So far (knock on wood) there have been no transmission issues either.
I usually run the generator (20 to 40 minutes usually) and take a current reading at the batteries to ensure the alternator doesn't need to work too hard on start-up.
Peter
ps Should I be reading the current at the alternator?
Peter,
No need to read amps at alternator. Your idea of exercising the generator BEFORE starting the engine is a good one. That will get the batteries back to a reasonable level of charge before starting.
Brett
I have been thinking about installing disconnects since we do not have access to AC power in our covered storage area and we do not have solar.
We have 2 red top batteries for the chassis batteries and 2 flooded 8Ds for house batteries. Do I need to install a disconnect on the negative terminal of each battery or on only 1 negative terminal in each set? If only on 1 negative terminal, how can I determine which negative terminal I should install it on for each set?
Thank you.
I was told by FT a long time ago not to put one inline. That disconnecting is the better alternative.
In fact the tech told me he would be fired for installing one.
As to installing battery disconnect inline, Foretravel Motorcoach would neither confirm nor deny. This would be the owner's choice.
Isn't there a battery disconnect at entry step for DCV to certain coach circuits? However, if there is reliance on 12VDC for critical circuits (the 1997 U270 does not have any installed from the factory). Then one would have to be certain the coach can take such a break in these circuits.
In the U270, the Coach 12VDC circuits which feed even with the entry step switch in the off position are the propane detector and the refrigerator (I think).
Peter
I don't think that I would install a blade type disconnect near any flooded battery. Sparks and the hydrogen that off gasses when charging make a bad combination. JMHO
Gary B
Gary,
You're right about the possibility of sparking when using the blade disconnects. I believe that George's picture shows AGM's not liquid acid flooded batteries.
George, I would only use one of those disconnects at the ground wire to the batteries. With that ground disconnected, the circiut is broken to all batteries.
Peter
p.s. Use the other disconnects elsewhere. e.g. One may be used for the toad while towing...
Today I installed one of the Cole Hersee battery disconnects. I did the house batteries first. Tomorrow I'll do the start batteries.
I had to fabricate a connecting bar for the terminal to accept the switch. A couple pictures follow:
Nice installation. I can't tell from you photo if the aluminum mount also carries electric amps, if so there is a lot of current that will flow through the aluminum bar and single mounting battery clamp bolt.
I think start battery cables are 4/0 (0000) which are pretty big and can carry about 300 amps, some of which are needed for engine starter.
Barry,
I used steel stock to fabricate the bar. It is a 3/4 in. by 3/16 in. bar. I thought it would carry the current well...but not 100% sure.
Peter
Ideal would be silver clad copper bar,
Dave M
Dave,
Thanks for the input. Now I just have to find the silver clad copper bar x 2. And I thought I was finished... :help:
I've never made any calculation to determine the size bar that would be needed for this project. Does this make sense:
4/0 copper wire cross section area must equal the cross section of copper bar????
Thoughts?
Oh, I can't locate any silver coated copper bar. This is as close as I get:
110 Copper Rectangular Bar | Cut 2 Size Metals - ESMW (http://www.cut2sizemetals.com/copper/rectangular-bar/kbr/)
That bus bar stock would be fine, and cross-sectional area provides the correct equivalence. Just wire brush before connecting and use dielectric grease.
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 (http://www.stormcopper.com/design/ampacity.htm)
Peter, I would first need to know the length of the needed bar, then one of our EE members should simply be able to tell you the correct size bar for the inrush current of approx. 1200 amp during initial starter engagement. I am certain the small bars in your pix would not make it.
Also, I would consider using the 4/0 copper welding cable (It is very flexible), would get the 4/0 ends that have the same size hole as your switch, then crimp and rosin solder correctly for a very fine connection.
A few ways of skinning the ole cat.
Cheers
Dave M
Dave, I only need a 2" long bar to make the connections. Then, at either end of this bar would be one 3/8" ID hole and a 1/2" ID hole to hook to the battery terminal on one end and the Cole Hersee battery disconnect at the other end.
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 (http://www.colehersee.com/home/item/cat/208/75908/)
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
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 (http://store.electrical-insulators-and-copper-ground-bars.com/b-916-500-100-012.html)
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...
Grote Industries: Starter Ground Lugs (Product #84-9204) (http://www.grote.com/cgi-bin/goc/goc.cgi?product_number=84-9204)
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,
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
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.
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?
Barry,
For edification, you do have parasitic loads from your positive cable to the starter when ignition is off?
Peter
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).
Here is an ampacity chart for copper bus bars http://www.stormcopper/design/ampacity.htm (http://www.stormcopper.com/design/ampacity.htm).
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