TheSamba.com :: View topic - Bus Depot split charge relay

Tue Jul 15, 2014 6:07 pm

I installed the bus depot split relay and cannot keep a fuse in it. Fuse will blow when I start the engine. This is what I have done:

30 to starter battery
86 to trigger wire (piggy backed at generator dash light tab on volt. reg.)
85 to ground
87 to Aux battery

All I have done to troubleshoot is double check all the above connections and verified it is well grounded.

I have a new lead acid deep cycle battery(my starter battery is also new) and have an auxillary fuse box off it that runs the stereo, a small amp and I moved the interior lights to it. The battery currently reads 11.80 across the tabs, with no load (I forgot to measure with some accessories running.)

Any thing jumping out that I am missing? I don't want to be too quick to jump that it is the cheap relay failing. Maybe I should have spent a bit more for something greater than 15 amp?

Thank you for any advice or ideas!

Tue Jul 15, 2014 6:10 pm

How discharged is the aux battery?

Tue Jul 15, 2014 6:12 pm

Anything over here help any?

http://itinerant-air-cooled.com/viewtopic.php?t=54...highlight=

Tue Jul 15, 2014 8:30 pm

Open this pic up.

http://www.busdepot.com/catalog/product/gallery/id/152359/image/287024/

30= Primary Battery Positive +
86= Minus ground -
85= Start contact
87= Auxiliary Battery Positive +

30 to starter battery
86 to trigger wire (piggy backed at generator dash light tab on volt. reg.)
85 to ground
87 to Aux battery

Wed Jul 16, 2014 5:05 am

Busdaddy: 11.80 across the posts with no accessories on. I will turn the interior lights and radio on and see what I get when I get home from work. Are you thinking that maybe it is run down too much and trying to pull too much juice through the relay?

Randy, that is a great write up. I need to read it again.

TCash, thank you for the link. I have the small blue cube relay, looks much cheaper than the one pictured in your link. The directions that came with mine def. show 85 to ground....now I wonder if my directions are miss printed?

Wed Jul 16, 2014 9:41 am

On your basic Bosch/Hella style cube relays the post designations should be like this. Post #85 & 86 are for the relay coil #85 is 12v to the relay coil and #86 to ground the relay coil. Post #30 and 87 are the contact side of the relay. when power is provided to the #85 wire it closes the relay contacts and allows voltage to flow across #30 and #87. So from what I see in the above pic it should work.

Wed Jul 16, 2014 10:06 am

RunningRough wrote: Busdaddy: 11.80 across the posts with no accessories on. I will turn the interior lights and radio on and see what I get when I get home from work. Are you thinking that maybe it is run down too much and trying to pull too much juice through the relay?
That's what I'm thinking, as other have said it sounds like you have it connected properly.

Wed Jul 16, 2014 10:43 am

How about posting a link to the relay you are using?

Wed Jul 16, 2014 11:14 am

You are wired correctly.

And that's your problem.

As mentioned in other posts, in a correctly wired auxiliary battery relay installation, there's nothing to limit the current flow from one battery to the other - except wiring and relay contact resistance. If you use big wire (like you should), the problem gets worse.

Small Bosch relays WON'T WORK reliably for this application. You need a big-assed continuous duty contactor from a golf cart or fork lift. Something that can handle 100's of amps.

[The only problem is that this method is a bit hard on the flat battery. Batteries really need a controlled charging method to keep them alive - a smart current-limiting charge controller of some kind. Think: expensive.]

The relay method is really only usable if (1) you use a heavy duty contactor, and/or (2) you don't let the auxiliary battery get too flat.

Wed Jul 16, 2014 11:14 am

This is the one:

http://www.busdepot.com/1738

Wed Jul 16, 2014 11:32 am

Hi Telford,
That makes sense. I didn't think I had run my deep cycle down at all really, but it is an absolute possibility that the kids have run the lights more than I am aware of. I have not load tested the battery yet. I am going to put it on the trickle charger when I get home tonight.

When I first installed the relay I did beef up the wire from the starter battery to the relay and the wire from the aux battery to the relay. When I discovered my fuse issue, I thought maybe that was my mistake. I then replaced those two wires with the wires that came with the relay......just to see....of course that did not solve the problem.

Looks like my next step is to charge up my deep cycle, then see if it keeps the fuse or not. This must be the issue.

Wed Jul 16, 2014 11:47 am

Most likely.

One thing to keep in mind: with the stock kit wiring, the wire itself is the current limiting resistor, and thus a short term dissipater of heat. Don't tightly bind these wires to anything which is temperature sensitive or would limit airflow around them (e.g. don't make a neat harness out of them - leave them a bit loose.) I know - this goes against the sensibilities of a neat installation and is annoying, but necessary...

Wed Jul 16, 2014 12:22 pm

I once owned a 1979 westy deluxe. it came with the factory camper battery set up. It used a Bosch cube relay and was wired with 16 or 18 gauge wire as well. That being said using a good constant duty solonoid and a nice beefy wires for the load side of things would not steer you wrong. Notice I said "constant duty solonoid" instead of relay here? that's because though simmilar thay are not quite the same.

Constant duty solinoids are made for higher amp loads. Like telford said. Most RV supply stores carry them. here is a little info for you.
http://www.colehersee.com/home/special_solenoid_applications/

Wed Jul 16, 2014 12:39 pm

http://www.colehersee.com/home/compare_products/cat/169/products=480,491,480,491,

Wed Jul 16, 2014 1:44 pm

Sodbuster and Tcash, thank you for the links! I have book marked that site.....looks like they carry some rugged products.

Great thread, a lot of good information! I found plenty of threads on this relay, but none having to do with a fuse blowing issue.

Wed Jul 16, 2014 1:50 pm

i'm using exact relay and same instructions and mine is working fine for a year now in my 71 westy 1600 dp

Wed Jul 16, 2014 2:11 pm

rugost wrote: i'm using exact relay and same instructions and mine is working fine for a year now in my 71 westy 1600 dp

That is good to hear. I haven't found too many posts, or any that I can recall right now, that have negative reviews with this relay.

I am going to top my battery off and give it another shot. But after that, if it acts up one more time I will def. be going the constant duty solenoid route.

Thu Jul 17, 2014 6:36 pm

The battery was very low. I charged it over night, hooked it back up, started the engine and all is good.

I will be more aware of its use and hopefully find that I can get a good amount of time out of the deep cycle without having to worry if I went beyond the tipping point. Time will tell!

Thank you for all of your help!

Thu Jul 17, 2014 6:59 pm

I don't know what kind of fuse that relay uses but if it's a blade style one of these may be the answer: http://www.autozone.com/autozone/accessories/Dural...59436_0_0_
Pick your own amperage, there's also ones with studs that you could wire inline and put a huge fuse in the relay.

Fri Jul 18, 2014 2:49 pm

Be very careful modifying the fuse on your unit. The fuse helps keep high current surges from welding the small relay contacts together. If they weld, you could, thinking it disconnected, unknowingly run your starting battery flat, leaving you in a fix...