Under-the-hood dual battery setup and FWC shell

[specjoe]

I'm all set to get an IBS dual battery setup in my '08 Tacoma Access Cab with an Odyssey 1500 from Sierra Expeditions on Friday. The Odyssey will go in a battery tray on the driver's side under the hood, after the ABS module is moved, I guess. I recently bought an ARB fridge freezer that I've got strapped down in the extended cab, so I'm hoping to finish the summer camping season without hot beer and/or a dead starting battery.

So here's the twist from everything else I've read about 05+ Tacoma dual battery installs - I'm hoping to wire a new FWC Finch shell I'll be ordering soon to this setup. I really considered just going with FWC's aux battery option instead (great price compared to what I'm about to drop!), but finally decided I like the idea of keeping the batteries (and as much as possible) out of the pop-up camper - as I know it's going to get cramped in there quick. So has anybody wired their FWC of ATC off of an aux battery under the hood? I'll primarily be just running the lights and furnace fan, but want to keep options open for other electrical wants back there in the future. I realize I might get a volt drop with the wire distance, but plan on running heavy guage wire directly off the aux battery when I get the Finch.

Any other concerns/thoughts are really welcome - just need to know I'm not following the wrong rabbit hole!

-joe D.

 

[AZHawk]

I haven't put the aux battery in the engine compartment but know someone who did. He just found a place for it and installed the battery isolator in the engine compartment as well, then ran the wires back to a trolling motor electrical plug to connect to the camper wiring. You need to fuse the positive side at the Main battery.

 

[davinski]

I have a Hawk shell and have 2 batteries under the hood. Currently, I run 10g wire to the camper from the spare and backup marine battery. The main starter battery never gets touched. I have the heavy duty Dodge ram alternator and the dual battery charging via a diode system (name escapes me now) I have been doing this for 8+ years no problem. If I need to jump, i use jumper cables under the hood and just hook + to + as they are both grounded to the truck. Makes the wiring easier as I have only jumped myself once. i like the idea of keeping the battery out of the camper. Space is a premium in there.

Also, if I had to do it over again, I would replace the stock connector for the FWC with a much more robust system. Probably powerpole connectors as all my gear has powerpoles. I can run the ARB fridge in the back or in the extended cab depending on how many people I am with. Saves more space in the camper. When in the back seat, I can reach it via the pass through window. This also keeps the noise down in the camper. I used to have a knife switch on the second battery so that I could take it out of the system if need be. But, this switch was not all that greatly constructed and the screws came undone one day off road. was wondering why my voltage on the battery would never go up and charge......Took the switch out and never put it back in. KISS still rules. Everything is fused and I have a large circuit breaker on it. A breakout box is a nice way to keep it neat.

Whatever truck I get next probably won't have space to put a second battery under the hood. Or, the space might not fit a big group 31. I would probably fab a mount and place it underneath the truck. Keep it out of the way, save space.

Good luck and hope it all works out well.

dave

 

[ntsqd]

My personal choice is to use a "Voltage Sensing Relay" or "Automatic Charge Relay" (VSR/ACR) in parallel with a marine battery bank combiner switch. It won't have the display that the IBS unit has, and I'm not all that sure that I'd miss that. I rarely stay in one spot long enough to need to know how much battery I have left. A simple volt meter will work for me. The VSR that I have for the FJ is a BEP Marine product, though I looked pretty hard at the Blue Seas products first. I went with the BEP part mostly on the recommendation of "whatcharterboat" (on that other site) as John deals with these systems nearly every day.

What is the current limit of the trolling motor connectors?

My only concern with the lower amperage Anderson products is a lack of knowledge. Is it possible to connect a black connector to a red connector? If so than I'd advise using the 175 amp polarized connectors, just for the IP ("idiot-proofness). If they can not be connected across colors, then I'd say those are a superior choice.

 

[specjoe]

Currently, I run 10g wire to the camper from the spare and backup marine battery.

I talked to Stan the other day, and it sounds like they run reinforced 10g wire to the campers, too. I've read all this about a voltage drop with the length of wire, so I'm wondering if I should invest some more in getting a 0g connection to the camper. Probably not much of an issue with the lights (which I'm planning on changing out for LED), furnace fan, and 12V plug (for accessories)I plan on running in the camper, but I was thinking of the versatility of moving the ARB fridge back there (from the extended cab) from time to time and maybe connecting an inverter. That might require another battery, though, as I'm seeing about a 36-hour fridge running time before I dive below 12v. Gotta account for the multi-day hikes and base camping.
I like the idea of keeping the battery out of the camper. Space is a premium in there.
I can run the ARB fridge in the back or in the extended cab depending on how many people I am with. Saves more space in the camper. When in the back seat, I can reach it via the pass through window. This also keeps the noise down in the camper.

Glad to have this concern validated with someone's experience!

Also, if I had to do it over again, I would replace the stock connector for the FWC with a much more robust system. Probably powerpole connectors as all my gear has powerpoles.

Will check with FWC on this.

I used to have a knife switch on the second battery so that I could take it out of the system if need be. But, this switch was not all that greatly constructed and the screws came undone one day off road. was wondering why my voltage on the battery would never go up and charge......Took the switch out and never put it back in. KISS still rules. Everything is fused and I have a large circuit breaker on it. A breakout box is a nice way to keep it neat.

Whatever truck I get next probably won't have space to put a second battery under the hood. Or, the space might not fit a big group 31. I would probably fab a mount and place it underneath the truck. Keep it out of the way, save space.

Good luck and hope it all works out well.

dave



Thanks for the really helpful and in-depth replies - this forum really is THE place!

-joe D.

 

[pods8]

Nothing really special about connecting the batteries into the camper wiring harness with them in the engine bay verse in the camper in my mind. In the camper I ran 10ga with inline fuses and that is exactly what I'd do from the engine bay back to the camper as well. Voltage drop is mainly a concern with higher amperage flowing in the lines relative to the wire gauge which in our scenarios should really only be a charging concern (ie if you're pulling a bunch of amps into the camper from those batteries such that voltage drop on a 10ga wire was a concern I'd start looking at what you're trying to run in there! ).

Edit: I for your size camper I'd definately explore them in the truck as well. For my camper I finally settled on putting them in the camper along with my AC shore power charger and DC-DC charger all wired in such that its all contained in one spot and the setup just requires one connection to the vehicle battery (and remote input to the DC-DC charger control if desired). Doing it the other way I'd have to move the DC-DC charger to the truck (or add two more sets of +/- lines) and run lines from the AC charger to the batteries (or back feed through the supply lines). As you can see that would get complicated and if I ever change trucks or sell the camper the whole package is all in one rather than having to move batteries/lines/charger and figure out mounting on the next rig etc (or confuse a future owner ).

 

[Eldough]

Definitely benefits to both options. If your only charging source for the aux battery is the alternator, and you want to charge the aux battery as fast as possible, I would think under the hood would be the best option...shorter wire run and larger wire. We have an '09 tacoma with the aux battery in the FWC separated with a surepower isolator and connected by about 15' of 10AWG wire. When the truck is started, I see ~15 amps into the camper battery and after about 5 minutes that tapers off and settles around ~4-5 amps...could be the alternator putting out less amps or the voltage increasing in the aux battery. You can also run larger gauge wire to the camper, but it gets $$. On the other hand, like Pods8 said, if you sell the truck, then there's more work in rearranging.

From the items you listed, it seems that 10AWG would be fine...the fridge should pull few amps...unless you want to run an inverter.

 

[brett13]

Does this sort of setup mean the camper battery is staying charged every time you drive even when the camper is off? Does that extra 'cycling' kill the battery faster?

 

[pods8]

Does this sort of setup mean the camper battery is staying charged every time you drive even when the camper is off? Does that extra 'cycling' kill the battery faster?


A battery doesn't cycle unless its been pulled down (or self discharged). Keeping a float charge on a battery is actually a good thing. However that doesn't automatically mean you are good to go, the main thing to consider what kind of battery you have and how its connected into the vehicle charge system. If you're set up for a bulk charge voltage only (which might be the case if you're taking direct alt. input depending on how the vehicle's alternator regulates voltage) and couple that with a battery that doesn't tolerate over charging excessively and you'll cook it if its a sealed battery. Flooded cell deep cycles will likely need to be topped off more with water otherwise they'll cook too. Its one of the reasons I put that DC-DC charger with stage charging in mine, I get bulk charge voltage when its needed for charging then it steps down to a float charge voltage to maintain the battery the rest of the time.

 

[brett13]

A battery doesn't cycle unless its been pulled down (or self discharged). Keeping a float charge on a battery is actually a good thing. However that doesn't automatically mean you are good to go, the main thing to consider what kind of battery you have and how its connected into the vehicle charge system. If you're set up for a bulk charge voltage only (which might be the case if you're taking direct alt. input depending on how the vehicle's alternator regulates voltage) and couple that with a battery that doesn't tolerate over charging excessively and you'll cook it if its a sealed battery. Flooded cell deep cycles will likely need to be topped off more with water otherwise they'll cook too. Its one of the reasons I put that DC-DC charger with stage charging in mine, I get bulk charge voltage when its needed for charging then it steps down to a float charge voltage to maintain the battery the rest of the time.

Whoa. This is greek to me. I was only thinking about moving the camper battery and the isolator to the engine bay. Basically just moving its location, not its charging method. Why would you have to change anything from the current setup (aside from simply moving it)?

 

[pods8]

Whoa. This is greek to me. I was only thinking about moving the camper battery and the isolator to the engine bay. Basically just moving its location, not its charging method. Why would you have to change anything from the current setup (aside from simply moving it)?


You asked if having it connected to the truck all the time would harm it from cycles. No it will not because its not cycling.

Having it connected to the truck (ie charge source) all the time with an improper charge setup for the battery can harm it though, similarly lots of driving with the same setup in the camper would do the same (you can boil out a battery basically). Physical location does not matter, its whether the current setup is even right for the batteries. Batteries aren't all the same and have pros/cons in different areas. Some tolerate different charging better than others.

If you're running lower cost batteries and just replace them regularly when they start loosing capacity then I wouldn't worry much about it. It starts mattering when you have more invested in the batteries that can last many years if properly maintained.

 

[brett13]

You asked if having it connected to the truck all the time would harm it from cycles. No it will not because its not cycling.

Having it connected to the truck (ie charge source) all the time with an improper charge setup for the battery can harm it though, similarly lots of driving with the same setup in the camper would do the same (you can boil out a battery basically). Physical location does not matter, its whether the current setup is even right for the batteries. Batteries aren't all the same and have pros/cons in different areas. Some tolerate different charging better than others.

If you're running lower cost batteries and just replace them regularly when they start loosing capacity then I wouldn't worry much about it. It starts mattering when you have more invested in the batteries that can last many years if properly maintained.

I see, thanks. I'm still curious though, why "whether the current setup is even right for the batteries"? Do you think the current setup is "that" bad for the batts or just that it can be improved?

 

[pods8]

I see, thanks. I'm still curious though, why "whether the current setup is even right for the batteries"? Do you think the current setup is "that" bad for the batts or just that it can be improved?


The stock setup is a single charge voltage, yes that can definately be improved. However different people put different merit in charging batteries since it can get a little complicated when you first glance at it but eventually comes into focus better. If you're in the "it seems to work good enough" camp and don't really want to dive into it, run cheaper batteries, don't care about reduced lifespan/capacity, etc. then the stock setup works (and just fine for certain batteries).

Assuming you're running the standard setup, its not my preferred setup for the batteries I'm running (different batteries would take different consideration). Since nothing came with my camper I got to pick what I wanted to use from the get go. I've got AGM (adsorbent glass mat) batteries which are sealed and can be kept in the camper without venting concerns, have longer life expectancy (assuming you treat them right), etc. However a proper charge profile is recommended for them as well.

Real quick battery 101 (taking some simplistic liberties): If you compare a battery to a water hose then voltage is the pressure forcing the water through the system and amperage is the flow rate. A battery likes a "bulk" charge at an increased voltage and moderate flow rate to fill it up most of the way. Then an "overcharge" at an increased voltage and lower flow rate to pack in the rest of the charge and make sure things are topped off. Finally a "float" charge that is a slightly higher voltage than the battery would normally rest at which keeps it full without trying to pack in more charge (actively trying to charge at this point can vent off the battery, which means you have to top off a flooded cell battery with water or if you have a sealed battery you've just taken life off your battery because you can't replenish the water that boiled out).

Trying to speak simply (I have two 6volt deep cycle batteries in series which makes the voltage cumulative to a 12V system). My batteries have this profile:
Bulk/Overcharge voltage ideal is 7.2-7.35V (thus 14.4-14.7V in a 12V system).
Float charge voltage is 6.75-6.9V (thus 13.5-13.8V in a 12V system).

My truck alternator puts out 14.1V which isn't ideal for either charging, weak for the actual charging and too high for the float charge. Thus the stock system wouldn't be ideal for best care of my batteries.

 

[Barko1]

if you have a sealed battery you've just taken life off your battery because you can't replenish the water that boiled out).





Question: How does the water boil out if the battery is sealed?

 

[pods8]

Question: How does the water boil out if the battery is sealed?


They call them "sealed" because there aren't water refill ports. They still have an ability to vent otherwise you'd have a bomb.

AGM/GEL batteries don't have liquid sloshing around in them like flooeded cell batteries (in GEL batteries the liquid is in GEL state and in AGM batteries its adsorbed into the glass mat - tricky naming ). Which is why they can be installed on their side and not leak (do not confuse this with a sealed flooded cell battery, such as the one under the hood off your car, though as those will leak on their side). However assuming I'm recalling correctly these can vent under certain circumstances as well, but what usually happens first in an overcharge scenario is burning out a portion of the battery (gel batteries are supposedly the most sensitive and get burnt out bubbles/pockets in the gel).

 

[Barko1]

They call them "sealed" because there aren't water refill ports. They still have an ability to vent otherwise you'd have a bomb.

AGM/GEL batteries don't have liquid sloshing around in them like flooeded cell batteries (in GEL batteries the liquid is in GEL state and in AGM batteries its adsorbed into the glass mat - tricky naming ). Which is why they can be installed on their side and not leak (do not confuse this with a sealed flooded cell battery, such as the one under the hood off your car, though as those will leak on their side). However assuming I'm recalling correctly these can vent under certain circumstances as well, but what usually happens first in an overcharge scenario is burning out a portion of the battery (gel batteries are supposedly the most sensitive and get burnt out bubbles/pockets in the gel).



Thanks! Don't need bombs in the FWC.