Automatic Charge Relay - How to Improve your battery isolator

DrJ

Senior Member
Joined
May 3, 2013
Messages
514
Location
Southern Idaho
There have been several topics and frustrations about charging our camper batteries from the truck.
I researched a few different options and came up with this mod which I thought might be helpful to share.
A special thanks to Ntsqd - his several great posts gave me the idea.

My FWC had been ordered with a compressor fridge that uses a fair amount of power. One of the sources to replenish the camper's batteries is charging directly from the truck's alternator. The stock system for this by FWC does provide some charging ability but has a few drawbacks. The stock system charges through a sure power 1314a battery isolator. This provides power to the camper but as a battery isolator has three main drawbacks:
1- loss of voltage to heat through the isolator
2- the isolator will not turn on if your voltage in the camper is too low (like 12.5 volts or lower). So when you need the power the very most from your truck you cannot get it.
3- No power could ever been transferred from the camper to the truck batteries in an emergency.

I replaced the Sure Power 1314a battery isolator with a Blue Sea ML-ACR with manual control.
First I had to remove the old battery isolator and label the connections for the new system. The Blue Sea ML-ACR was installed in the same position as the Sure Power isolator. It has an addition manual control that needed to be wired to the ML-ACR along with the negative and positive terminals of the camper battery. The wiring did require custom lengths of wire, modifying the wire ends and shrink wrapping the ends for protection. Then I had to pull the wiring and cut a hole for the switch into my camper's power center. Finally, since my Blue Sea ML-ACR was much larger than the prior Sure Power, I had to build a wood box around it to protect it while it was in a storage area of my camper.

The new system is a big improvement from the prior stock setup up. Overall I am very happy with the setup.
Here are some of the benefits of the system:
1- Enhanced charging capacity from the truck. I was able to charge 3-4 amps/hour faster with the new Blue Sea equipment. There is very little loss of energy to heat.
2- I am aware and in control of charging from my truck to camper. I can override the automatic system and connect the batteries to allow charge no matter how low my camper batteries are. The monitor switch always lets me know when the systems are connected. No more suprises when I show up at my camping spot thinking that the truck is charging the camper.
3- My camper's solar system can charge my camper batteries and truck batteries if I want it to. If I only want to charge the camper batteries I can do just that too.
4- If my truck batteries were ever too low to start the truck I could charge them from the camper batteries. This is a great safety feature.
5- A manual switch on the ACR allows you to work on the camper electronics without any power source from the truck if you need to do repairs.
6- In the automatic mode the system functions just like the stock FWC system was meant to. It allows charging of the truck camper batteries from the truck without discharging the truck batteries unless you override the system. It's just better. :)

prior stock setup with battery isolator
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New Blue Sea in place and connected
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Wiring that needs to be feed for the manual switch and monitor
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New switch in place by the trimetric monitor
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Blue sea switch is on indicating the batteries are connected
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New box to protect the electronics and wiring
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Box completed. Now I can still store my stuff under the front dinette seat.
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The cost of the modification was about $240. Most of this is the cost of the Blue Sea equipment - $210 for just that.

You could improve your system with just using the Blue Sea SI-ACR. It would be a direct replacement for your battery isolator and the cost of it is only about $75. However you would not get the cool switch to know when you batteries are connected and the ability to override the automatic system if you wanted.
This was a huge positive for me and worth the extra expense.
 
Nice! I was thinking about the same thing for the indication. The 1314 says that it will only not connect below 10V, but it would still be nice to have the peace of mind to know that it's connected. Do you know off hand what the load is on circuit when the batteries are connected?

Don

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Don,

I am not sure that I know how to answer your question but this reference might be helpful:

http://assets.bluesea.com/files/resources/instructions/990180180.pdf

I have noticed that the sure power isolator struggles to connect under 12.5 volts. I believe below a certain voltage it may not connect at all.

Truth be told on the automatic settings the Blue Sea ACR does a similar thing.

I turned on my fridge, rear flood lights and heater to draw 11-12 amps and lower the voltage to 12.2. The ACR would switch on and off while on automatic mode just like the sure power would. But the difference was I was able to override this setting while the truck was running to connect them. That part is one of the reasons I wanted to do this.
 
Great job making the system the way it should be.

Please refer to what you are calling "Sure Power 1314a battery isolator" properly as a "battery separator"

A isolator has a diode to prevent the camper battery every seeing the truck battery. There is some voltage drop because of the diode, but I prefer using a isolator over the separator.

Once again great work having control over what and when charging batteries.
 
It could be a lot cheaper to buy a couple of waterproof digital voltmeters. Attach one to the camper batteries and the other upstream of the isolator/separator relay.

When the relay connects the truck to the camper batteries, there will be very little difference between the meters. When the relay disconnects the circuit, the voltage difference will be larger.

Looking at the two meters, you will be able to tell if the two circuits are connected and for less than $20, (maybe less than $10).

Paul
 
Pvstoy,

I believe you are correct on the Sure Power isolator vs separator. I pulled up the information from the company and it is labeled as a battery separator.
Thanks for the correction.
 
Great post and write up. I have also read with interest what ntsqd has written about the marine ACRs. A couple of things:

-I'm not sure if my Hawk is wired like your camper, but the Sure Power separator in my camper disconnects if the truck battery drops below a set voltage, and will not re-connect until the truck battery comes up to that voltage again (when the alternator is charging it). I found this out this winter when I was hoping to keep my truck and camper battery charged off of the 160 W panel on the camper. At night, the truck electronics would draw the batteries down to the disconnect point. The next day, the camper would come back up to 100% (Trimetric), but the battery separator would not re-connect to charge the truck battery. I eventually got frustrated with this and connected the camper and truck battery together in the camper. After that, on a sunny day, the truck and camper would both come back to 100% each day. I should mention that when I say truck battery, it is an aux battery in the truck which is separated from the starting battery with a smart separator under the hood. If I want to disconnect the camper from the truck (aux) battery now, I have to pull the fuse under the hood.

-I noticed from your photos that the original Sure Power separator was mounted in a mesh box. Your new ACR is mounted in an enclosed wood box. Are there any concerns about ventilation and heat dissipation from the new ACR in the enclosed wood box?

Thanks again for your post. Your system is the gold standard, and how FWC should wire them from the factory.
 
If an ACR (or VSR) is making heat then something is wrong. Heat from an electrical item means current is flowing thru a resistance. There is a little resistance in the coil holding the contacts closed (assuming its not a solid state circuit), but it should be on the order of milli-amps or nearly so and that heat would be undectectable or very close to it. Some of these units employ a PWM circuit to hold the contacts closed, so they use even less current.
 
Enjoying the discussion, I understand why FWC uses the sure power separator. It is plug and play for the buyer, however as this thread point out not always the best. I noticed that sometimes my camper batteries were not all the way charged after driving. My truck still had the old solenoid under the hood from my 2002 Hawk. I just removed the sure power separator and use the solenoid. I know if my truck is running I am charging the camper.


Any down side to this? Also I like the idea of the two gages to be sure your are connected. I might put them in my truck cab. I would thing this is a better location. If you are driving down the road and for some reason the sure power disconnects you could not see the indicator in the camper until you arrived at your camp.
 
Bill,

I do like your current setup as you would always know that your camper is getting power when you are driving. I am assuming that your solenoid allows charging even if your camper batteries are depleted?

I originally thought about putting the monitor in the truck instead of the camper. I decided that in the camper it would be easier to install and use for me.

But I do believe there is a LED output from the Blue Sea System that would allow you to have another additional LED monitor on the system. This way you could have one in the camper with the switch and another one in your truck. That would be pretty neat and the best of both worlds.
 
In case you were interested, here are a couple of videos that describe the system a little better.


 
This mod was entered into the Truck Camper Magazine competition.
It has worked out really well for me in the last several months.

I always know exactly how my batteries are being charged with this system. No more problems with the battery separator cutting out when the voltage is low.

It has even charged my truck batteries when the truck is parked somewhere for a week while we camp.

I'd highly recommend it if you want more control over the stock system.

Here's the link to truck camper magazine if you are interested:

http://www.truckcampermagazine.com/camper-mods/contests/july-mod-contest-medium-mods/
 
DrJ, I read your post with interest. Thanks for posting!

Interesting, FWC is now installing the Blue Sea Systems separator in new campers. The BS unit has a 12.25V low voltage lock out.

The ML-ACR 7622, applicable to FWCs even though I prefer Deutsch DTM connectors as in the 7622100B unit, is a superb unit and have been using it on my flats boat for many years. I have a 12V crank battery and a 24V (2x 12V batteries) trolling motor batteries on my boat. I use the Blue Sea battery selector allowing me to use any battery for any purpose, in an emergency.

However, one important thing to remember, an alternator is not a battery charger, at best it is a battery maintainer. While I would certainly manually override the lockout on the ML-ACR in an emergency situation, I would not routinely manually override the low voltage lockout to charge the camper batteries.

There are many good articles from subject matter experts why an alternator is not a battery charger. Here is one from Optima.

On the road and camping, I try to maximize solar charging to the maximum extent possible. But, nothing replaces shore or generator supplied electrical power to restore camper batteries to full capacity.
 
DrJ

Thanks so much for the dissertation on the separator. When I was running my three way fridge on DC it was running my batteries down within an hour. I thought someone way smarter than me has had this problem and posted the solution on WTW forums. I did your mod on my 2015 Hawk and what a improvement. Now when fridge is on DC the solar panel and
hard link to the alternator keeps batteries fully charged.
Peter K
 
Advmoto 18,

That's for the kind feedback. I was not aware that FWC had made that switch. It would be a good one that would positively impact a lot of their customers.

Peter K,
I'm glad this has been helpful to you. I've really liked it and I use it all the time when I camp. It also keeps my diesel truck batteries well charged if I'm camping for an extended period.

As far as an emergency backup, I agree that it would be a challenge to jump the batteries from the camper. Rather I would allow power to be transfered either directly from the camper or solar charge over time to get enough charge. Not a fast solution but if I didn't have any other option it would work.
 
Cool DrJ, this is a mod I am interested in. So it's (except of the switch) pretty much a direct replacement for the SurePower - no additional connections to the truck? Also, are you still using the 10ga wire from the alternator or did you upgrade that too?

Thanks.
 
Charlie,
It is a direct replacement and fairly easy to do.
The switch adds a lot to the system and I'd recommend it, but you can certainly run the system without it.

The switch takes a lot more time (and wiring) to make it work.

I have been thinking a lot about upgrading my truck wiring to the camper. It is still the original 10 gauge wire that FWC installs.
Maybe that's my next mod.
 
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