Truck to Camper Electrical

[Clark]

Ok. So is that Blue Seas SI ACR bad news? Someone told me that is not an isolator, and if I use it, when the truck and camper are connected the batterys will slowly drain each other b/c they are constantly trying to average out the voltages. Basically it was stated that with all four batterys tied together in this way, if the camper is at 9volts and I start the truck, and my truck bateries are at 12 volts, the alternator actually averages them and sees 10.5 volts, so it will output max amperage to all four batterys, this will lead to the truck batteries being cooked as they are fully charged and do not need max amperage.

IS this correct? If so, is it better to due away wit the ACR and go with something like this?

http://www.amazon.com/NOCO-IGD140HP-High-Performance-Battery-Isolator/dp/B001DKRF2M/ref=sr_1_1?ie=UTF8&qid=1366851003&sr=8-1&keywords=battery+isolator

 

[pods8]

No it's not true and battery isolators suck, in short.

 

[Clark]

So, the alternator will not see both banks, and average the voltage? It will charge one bank fully first, then the next? Just trying to figure out how they work..Thanks again for all the advice.

 

[Clark]

As I read on the Blue seas website for the SI-ACR, both batteries are combined during charging. What would happen if I used the camper batteries a fair amount and they were low, and my truck batteries were basically fully charged? Would the truck batteries receive to much amperage?

I do see the benefit of these is when discharging, the load will only come off one battery bank. I am wondering if it also can "sense" that the truck OR house battery for that matter, is fully charged and will someone regulate the flow as to not "cook" the battery.

I see that those isolators drop a fair amount of voltage and are older technology.

Just want to make sure when I install of this, I am not overlooking something. It would really suck if my truck batteries got harmed b/c the ACR kept sending it to much amperage...

 

[Clark]

Actually it seems that when one battery (the truck one hopefully) is above a certain voltage (13.v) the ACR will close the switch to that battery and the charge will go to the other bank (camper). When the voltage drops to a certain level (12v) the switch to that battery will re-open and charging will commence (truck battey I hope).

http://www.bluesea.com/articles/58


Am I understanding this right?

 

[ntsqd]

You are close.
The premise of the voltage sensing relays and automatic charge relays is to first bring the starting batteries up to full charge, and then connect the camper/house battery(ies) to the charging system. Electrons are lazy, they always, always, always take the easiest, least resistive path. A full battery is not the easy path, so when combined most or all of the charge will go to the lowest state of charge battery(ies).
Then when the engine is turned off the relay will sense that the charge voltage has dropped below the programmed minimum acceptable and it will open, separating the starting battery(ies) from the camper/house battery(ies).
The truck battery(ies) is/are always in the charging circuit. The camper/house battery(ies) are only in the charging circuit when the relay is closed. So when the relay is closed the regulator will see an average of the two voltages, but that isn't too big of a deal. At most it simply prolongs the charge time for the camper/house battery(ies).

There are marine charging systems capable of charging two separate battery banks without combining them. I've looked into this. The alternators to do this start at about $400 and the regulators start at around $350 or so. Then, such an alternator will not necessarily fit in the stock location, so you're probably looking at fabrication of unknown proportions to get such an alternator mounted on your engine. Alternately you could put a second alternator on the engine. That will likely be a lot of fabrication.

 

[Clark]

Sounds like the ACR is an okay approach. Just to double check, the alternator is connected to the truck batteries, and the ACR is connected between the battery banks, therefore I do not need to mess with the alternator wiring, to get it to wire into the ACR. The charge essentailly goes to the starting battery first, then once the proper voltage is reached the ACR senses this, and closes the circuit allowing the electrons to flow to the camper battery. I assume a small amount of electrons will still go to the truck battery, but it wont be significant enough to ruin them?

 

[pods8]

I didn't feel like typing on my mobile last night.

1) The alternator won't cook your battery bank (assuming its regulator is working properly and that has nothing to do with the ACR) as it functions on maintaining a voltage, if there are higher draws the voltage falls and it will try to output more but its still voltage based not forcing current.

2) The voltage will not strictly average between the banks since things don't magically equalize (as a strict average) when connected up due to resistances in the batteries/wiring/etc. What will happen when the drained camper batteries get connected up to the truck battery is that current will start flowing to them. This will lower the voltage of the truck batteries which will be sensed by the alternator regulator which ideally increases output to match that current flowing back to the camper batteries, if it is able to do so the truck batteries are generally on the sidelines as the easiest path will be taken (ie it will go from the alt to the truck battery post but then head down the wire to the ACR rather than into the truck battery as that is where the draw is). If the draw is too big for the altenator it will actually pull down the truck battery voltage but that is where the low voltage cutout on the ACR comes in as well and will disconnect things.

3) Batteries have internal resistance to them and it takes a higher voltage than they are to push amps into them. As long as the voltage regulator doesn't exceed its normal settings it shouldn't push more amps into any battery than the battery willingly takes.

 

[Clark]

Sounds like I am good to go with the previous configuration yall helped me come up with.

Truck Battery --> Breaker ---> PowerPole Connector ---> ACR ---> Breaker ----> Camper Battery.


I guess the only part of the above configuration that I may change is the location of the ACR. Maybe it should be inline somewhere before the connector? Maybe in the engine compartment? Or maybe it is best to have it in the camper next to the batteries and the breaker?

 

[pods8]

Shouldn't matter for charging. I'll likely put on the truck side. I'll have a switch on the ground for it so I can over ride it and keep it off when there is no camper on the truck so the pigtail won't be "hot", it may auto sense that feature (can't recall off hand) but I'll have an override switch regardless for other reasons.

 

[ntsqd]

The camp off scenario is why I put my VSR in the camper. My though was to simply turn off the breaker under the hood. I've since defeated myself by deciding to tap into that battery hot to run heavy gauge power to the rear bumper. It is a good thing that I don't really ever expect the camper to come off. If it does it is not like I have an exposed live battery hot, the contacts in the Anderson connector are fairly well protected. And there are plugs made for them if it becomes a concern for some reason.

 

[Clark]

Well I have some news. I think the 50amp breakers are to small, atleast for my 99 Dodge Diesel. The alternator puts out atleast 120 so I am going with 120amp breakers. Also, it seems to me the 6 gage might be a little small, it would be better to go with 4 gage. A marine electrician was telling all about it. He had some simple equation.

I am going to test things out with 6gage, as I am to lazy to re run the cable. But I will be buying new breakers. That being said, anyone that is in the market for some Blue Seas 7100 (http://www.jamestowndistributors.com/userportal/product.do?part=220488&engine=adwords!6456&keyword=product_ad_2281&type=pla) that I would sell for cheaper than you can buy them for.

Picking up the camper Monday morning. I hope I have all the required parts and cable to make the run from camper battery to breaker to VSR to powerpole.

Also, FYI you are supposed to have a fuse in your ground line fore the VSR. I did not know that....

 

[camelracer]

Well I have some news. I think the 50amp breakers are to small, atleast for my 99 Dodge Diesel. The alternator puts out atleast 120 so I am going with 120amp breakers. Also, it seems to me the 6 gage might be a little small, it would be better to go with 4 gage. A marine electrician was telling all about it. He had some simple equation.

I am going to test things out with 6gage, as I am to lazy to re run the cable. But I will be buying new breakers. That being said, anyone that is in the market for some Blue Seas 7100 (http://www.jamestowndistributors.com/userportal/product.do?part=220488&engine=adwords!6456&keyword=product_ad_2281&type=pla) that I would sell for cheaper than you can buy them for.

Picking up the camper Monday morning. I hope I have all the required parts and cable to make the run from camper battery to breaker to VSR to powerpole.

Also, FYI you are supposed to have a fuse in your ground line fore the VSR. I did not know that....

Your Dodge's alternator is CAPABLE of putting out 120 amps. That doesn't mean the load in your camper is going to use that much power. Size your breakers and wire according to the required load not the alternator capacity. What you're proposing is a waste of money.

 

[Clark]

Your Dodge's alternator is CAPABLE of putting out 120 amps. That doesn't mean the load in your camper is going to use that much power. Size your breakers and wire according to the required load not the alternator capacity. What you're proposing is a waste of money.



What do you mean by required load? My batteries (two) are 94 ah. IS this what you are referring to? It seems like these batteries re big enough to take the full load from the alternator. I am most likely not understanding this...

 

[pods8]

What do you mean by required load? My batteries (two) are 94 ah. IS this what you are referring to? It seems like these batteries re big enough to take the full load from the alternator. I am most likely not understanding this...


1) Batteries have resistance to them, they don't want to take a charge. That is why you have to provide a higher voltage to push the charge into the batteries. I don't feel like running the numbers but you're not going to push 120amps I can guarantee.

2) Your breaker size is based on your WIRING, its there to protect your wiring.

3) This is the second time you've taken outside information and ran with it w/o understanding/verifying it. Slow down. If you hear something contrary to the advice we've given you come ask. Don't come in arms flying saying its all wrong, its sorta insulting. We're not perfect and new knowledge is always available but we're also not completely misguided either.

 

[camelracer]

The load is the amount of current required when everything in the camper is turned on plus the current required to charge the batteries. As pods8 said batteries have internal resistance which will limit the current unless you have a shorted battery. If you do have a shorted battery you don't want to be dumping 120 amps into it.

If you're protecting the camper wiring with a 120 amp breaker you need to upgrade all your wiring from the the breaker to the camper fuse box with wire capable of carrying 120 amps. This also includes all the connectors in the truck and camper.

My truck has a 136 amp alternator and the camper has 2 Optima blue tops. I'm using a 30 amp breaker with #10 wire and have never had a problem.

 

[craig333]

You want to run the smallest size breaker that will do the job. Larger just means its likely to not open soon enough to protect your circuit. Four gauge is serious overkill unless you're planning on doing some welding not to mention what a pain it would be to run wire that size. I've also found the factory 10 gauge wiring to be adequate for my needs.

 

[pods8]

You want to run the smallest size breaker that will do the job. Larger just means its likely to not open soon enough to protect your circuit. Four gauge is serious overkill unless you're planning on doing some welding not to mention what a pain it would be to run wire that size. I've also found the factory 10 gauge wiring to be adequate for my needs.


I believe we were talking 6ga, and I wouldn't necessarily call it serious overkill. With the source I linked before we're talking less that $20 more in wiring costs and it still fits connectors like the SB50. In return your voltage losses will be less than half that of 10ga. On a long drive it won't make a hoot of difference I will grant you. But it will work better for short period charging, esp. with a larger battery bank that can take the amps available.

I spoke that I was planning on 6ga. In my case I run a dual bank for a combined 210ah. Normally I'll have solar going in addition keeping everything happy. The situation in my head were 6ga wire to the truck would be handy is say I'm camping at a ski slope, solar is covered by snow and heater/lights are running a lot. If I wanted to fire up the truck and dump an amp load into the batteries it would be nice to do it in the fastest time possible. One of my gauges has an idle control to bump things up to 2500rpm on demand as well to actually get said amps flowing verse the normal 800-900rpm idle. So for $20 why not cover my bases?

10ga wire with the batteries 20' away and an altenator putting out 14.1V: at 10amps the voltage at batteries would be 13.67, at 20amps its 13.23 (though I doubt 20amps would be flowing with the voltage low like that), conversely with 6ga 20amps you'd still be at 13.75V.

 

[Clark]

Well, I got the camper and am back at home getting ready to finish up the wiring. I know you guys are not misguided, this is why I came here to ask questions and learn. But when a maritime electrician fills my head with a bunch of stuff, I tend to get a little worried. I think he was used to over-building systems for marine applications and was trying to do so with my setup.

Anyway, my bad if it came off as rude or accusatory. The Alaskan is awesome! I have the truck side of the wiring all done. When I picked up the Alaskan the wires I have coming through the bed to the powerpole were actually in the wrong spot and the camper sat on them. So I removed the camper a few days ago (which was a project in itself) and have since relocated the wires and powerpole. I think I figured out where I want the breaker and ACR for the camper and only need to mount them then crimp the last few terminal connectors and I am done. I sure hope it works!

So when I leave home, the camper batteries will be full charged, would it be best to flip one of my breakers (one at the truck batteries) so current does not flow to the camper batteries during the drive?

THANKS FOR ALL THE HELP AND ADVICE.

 

[ntsqd]

I have 6 ga. wire (power & ground) and I used that gauge because of the voltage drop that pods8 mentions ("HandyBob" influence). I use an 80A breaker, which is appropriate for the wire size, but overkill for charging the camper batteries. I did that because there are other things drawing off that breaker (VSR is in the camper, not under the hood) and fully expect to pull 80A (OBA, 2M, etc.) though likely only on a very few occasions and very short periods. Any lower amperage tap will have it's own fuse or breaker appropriate for the wiring used. Were it not for the additional demands on that primary breaker I suspect that a 30A-50A would be about what I'd have gone with.