Auxiliary battery location talking point (1 Viewer)

[r2m]

Okay, this is a talking point for all my friends out here in MUD.
As (most of) you know I have dual Odyssey PC1200 batteries. Since Odyssey batteries are a little smaller, I have two of them stuffed in the factory location as seen in my build thread here: Builds - R2M 2013 GX460 Overland Build starting at post #53
I also have a 3000 watt inverter in the back of my rig mounted on a Victory MOLLE rear quarter panel (Builds - R2M 2013 GX460 Overland Build post #89)
So, what I'm thinking is putting one large battery (read: huge amp hours) in place of the dual batteries up front and then mounting a second, even larger (RV or marine) battery up under, in the spare tire cavity.

Here are the talking points:

1. I already have huge 1/0 gauge AWG wire running all the way back for my inverter, so I don't need to add any wiring.
2. Odyssey batteries can be mounted on their side, providing easier access to battery posts.
3. There should be enough depth to stuff a massive RV or marine battery up there.
4. Batteries don't need to be weather shielded.
5. I can add a "skid" plate for worst case scenario.
6. I don't/try not to get into situations of rock crawling, thus the previous comment being just a precaution.
7. I don't have any other plans for anything going up there, especially since California is not friendly to after market fuel tanks.

Am I off my rocker???
Reasons to do it?
Reasons not to?
What do you all think??

 

[giovanni]

My "pros / cons" engineering mind starts to think about weight vs battery capacity. Assume you're talking AGM batteries - which are heavy, vs running your truck every day for a bit to charge a smaller / lighter battery set.

You're already protected by the dual battery setup from over discharging and being unable to start, so what you gain is ability to go longer without any charge cycle. Is that worth the weight?

 

[r2m]

My "pros / cons" engineering mind starts to think about weight vs battery capacity. Assume you're talking AGM batteries - which are heavy, vs running your truck every day for a bit to charge a smaller / lighter battery set.

You're already protected by the dual battery setup from over discharging and being unable to start, so what you gain is ability to go longer without any charge cycle. Is that worth the weight?

Ahhh! Another engineer! Great!! Yes Odyssey batteries are AGM and yes they ARE heavy and I have two of them up front. So replacing the two up front with one larger one will reduce some front end weight. I'm not too worried about how heavy the second rear battery is since it will be located at about the very lowest point on the vehicle and also just behind the rear axle, so if anything the CG will be minutely lower.
And in general, the added weight of adding larger batteries is pretty much a non-issue since I run with so much overland gear as it is.
I'd prefer to have a much longer discharge time while using my 100 Watt solar panels. I have a couple of refrigerators, one small one for weekends and a large 85 qt for long (week long plus) camping.

Also, a little off topic, what field of engineering?

 

[giovanni]

I'm a nuclear engineer, but have worked in aerospace my whole career.

Your approach to weight makes sense. I think AGMs are only dischargeable to ~50% of capacity before voltage droops too much, so a 200Ah batter will give you roughly 15 - 18 hours powering a fridge (~6A draw), which could be offset completely under ideal daylight conditions with solar.

 

[r2m]

Bump...
I was really hoping for some input and thoughts this battery relocations.
Anyone have any warnings, suggestions, etc.???

 

[Washingtontaco]

Bump...
I was really hoping for some input and thoughts this battery relocations.
Anyone have any warnings, suggestions, etc.???

This is what I did. I made cardboard (CAD) mock ups of different battery group sizes *FROM the manufacture you will be using. Start positioning where you think you would like them to be. I found that the spare tire area for me was not a viable location and this was with the spare tire winch removed.

That is why my second (house) battery is mounted dead center of my storage drawer/box/platform. No heavy battery aft of the rear axle.

 

[r2m]

This is what I did. I made cardboard (CAD) mock ups of different battery group sizes *FROM the manufacture you will be using. Start positioning where you think you would like them to be. I found that the spare tire area for me was not a viable location and this was with the spare tire winch removed.

That is why my second (house) battery is mounted dead center of my storage drawer/box/platform. No heavy battery aft of the rear axle.

View attachment 2466381

I wish I could commit to having my 2nd and 3rd seats down and do something similar to what you have, but my daughter and 3 year old granddaughter live with us and I often need the 2nd row seats and sometimes even the 3rd row.
But, on to your other comment, you said you considered using the spare tire location (I too have the winch removed) but opted not to.
Reason/s?
I haven't done any hard measurements to see how deep I can go, I'm just spit-wadding the depth by how wide a stock spare tire is and guessing that it's about the same width of a battery.
BTY, great idea making cardboard mock-ups of possible batteries! I should've thought of that!!

 

[Washingtontaco]

I wish I could commit to having my 2nd and 3rd seats down and do something similar to what you have, but my daughter and 3 year old granddaughter live with us and I often need the 2nd row seats and sometimes even the 3rd row.
But, on to your other comment, you said you considered using the spare tire location (I too have the winch removed) but opted not to.
Reason/s?
I haven't done any hard measurements to see how deep I can go, I'm just spit-wadding the depth by how wide a stock spare tire is and guessing that it's about the same width of a battery.
BTY, great idea making cardboard mock-ups of possible batteries! I should've thought of that!!

I settled on a group 27F Northstar battery. Similar in size to stock but 12 amp hours more reserve and a bit more cold cranking amps (75?). This is in both locations, factory tray and house. I did this as the house could back up the start in a damaged start battery replacement, IE trail collision, in Baja front end damage etc.

 

[Washingtontaco]

BTY, great idea making cardboard mock-ups of possible batteries! I should've thought of that!!

This is why there are technicians, keep you engineer types on track.

 

[ducktapeguy]

Just curious but what is the purpose for the batteries? I do have a second battery strapped down in the back of my GX to power my fridge with a 100W solar panel. Even that I think is overkill as I have run the fridge from the start battery many times with no issues and some of the more expensive fridges don't draw a whole lot of power. It was more for my own piece of mind than anything else, plus I just wanted to do something to do on the car. Other than the fridge I don't have that many electrical needs so my opinion is limited to my own experience.

At some point a generator makes a lot more sense than batteries, it can run longer, provide more power, and takes up less room, and is probably cheaper overall. If I had the space under the car I'd probably go with a larger aux tank or even a water tank before batteries. As long as there's gas in the tank you pretty much have an unlimited supply of electricity from the alternator, and a solar panel or two can keep up with most demands if you don't want to run the engine. The only time I can see having large battery capacity is to run something like an air conditioner at night, a large load for long periods of time where you can't run a generator and there's no sun.

 

[Washingtontaco]

Just curious but what is the purpose for the batteries? I do have a second battery strapped down in the back of my GX to power my fridge with a 100W solar panel. Even that I think is overkill as I have run the fridge from the start battery many times with no issues and some of the more expensive fridges don't draw a whole lot of power. It was more for my own piece of mind than anything else, plus I just wanted to do something to do on the car. Other than the fridge I don't have that many electrical needs so my opinion is limited to my own experience.

At some point a generator makes a lot more sense than batteries, it can run longer, provide more power, and takes up less room, and is probably cheaper overall. If I had the space under the car I'd probably go with a larger aux tank or even a water tank before batteries. As long as there's gas in the tank you pretty much have an unlimited supply of electricity from the alternator, and a solar panel or two can keep up with most demands if you don't want to run the engine. The only time I can see having large battery capacity is to run something like an air conditioner at night, a large load for long periods of time where you can't run a generator and there's no sun.

Well a lot of reasons. A house battery runs everything on my vehicle short of what the start battery was designed for. In other words all of my aftermarket electrical draw such as offroad lights, USB ports (high amperage), fridge, Jerry can water spigot, additional interior lights, HAM radio, eventually a inverter and any other item I may add. I have a 100 watt fixed solar panel and 120 watt foldable panel. As long as I camp near water running out of food and beer are my only limitations.

 

[r2m]

Well a lot of reasons. A house battery runs everything on my vehicle short of what the start battery was designed for. In other words all of my aftermarket electrical draw such as offroad lights, USB ports (high amperage), fridge, Jerry can water spigot, additional interior lights, HAM radio, eventually a inverter and any other item I may add. I have a 100 watt fixed solar panel and 120 watt foldable panel. As long as I camp near water running out of food and beer are my only limitations.

Have to agree with your points.
I have a 3000 watt pure sine inverter (I used to have a gas chainsaw, got tired of smell, mixed gas, leaks, and the constant pull, pull, pull to start. Now I have an electric one, so I need the juice but it is always instant on). Although I do have to have the car running to use it since it draws so much current. But when I'm stationary for a long time, there are two fridges, a large and small, albeit, I only ever use one or the other, not both. Plus the HAM radio will sometimes stay on for hours monitoring communications with our offroad club members or when I use it as a TOC for Army COMM's during training exercises. Also proximity lights, charging tablets, computers, phones. In short I can put quite a drain on my current batteries and electrical system, hence why I'd like to go with some seriously large amp hour batteries.

 

[ducktapeguy]

I completely understand the need for dual batteries, as I said I have a setup in my own car. for constant small loads they make complete sense, stuff like fridges, charging electronics, and stuff like that

What I was trying to get at was that for larger electrical loads, which is what it sounds like you have, there is a point where energy storage (I.e battery capacity), becomes less practical and the need for energy generation makes more sense. And once you have the ability to generate power, through solar panels, generator, or in your case the cars alternator, the need for large amounts of energy storage becomes even less important.

For example, in the case of using a 3000 watt inverter, it would take a huge battery bank to power it for any significant length of time. That’s pretty close to the power a winch would draw, so a single automotive size battery is going to last for maybe 30 minutes? Plus it’ll have limited lifespan. You can go with the large deep cycle golf cart batteries which would last longer, but would weigh hundreds of pounds and take up a lot of space. For the similar space and weight as a large battery, a small generator like a Honda could power those loads for hours at a time and do it indefinitely. Or, since you have the car running to recharge the battery as your using it, the need for a large battery capacity doesn’t seems as critical.

I don’t know about Ham Radios, i only use the handheld which consume very little power, but in how much power does it use? And how do you fit 2 fridges in a GX? I have one small one and it takes up most of the room in the back even with d row removed.

 

[r2m]

Very good points! When I'm drawing heavy loads, I am idling my engine to keep up with the draw, like my chainsaw, compressor, inverter. It just seems that I'm having to recharge (idle engine) my batteries more often when I run my small fridge for a day or so (as an example). Maybe my batteries are getting tired?? I may have drained them too much too often, not paying attention to how low the voltage was when I was leaving things plugged in.
I'll probably have to just do more research on batteries.
But you did make a point, that although I can't add a second fuel cell in the spare location, I could tuck up a water supply. Only issue is that I'd have to fabricate something like that since there is nothing on the market (that I know of). It would be nice to take some that weight to be mounted lower and off the back of my tire carrier!

 

[giovanni]

Trailed 6-Gallon "Spare" Tank Overview & DIY Guide For 5th Gen 4Runner

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And I think they are stackable, so you could carry multiples...

 

[r2m]

Trailed 6-Gallon "Spare" Tank Overview & DIY Guide For 5th Gen 4Runner

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And I think they are stackable, so you could carry multiples...

AWESOME!!
except the price... A three pack is $450.00!
It looks like one has to take if off, in order to use it. I don't think you can just leave it mounted and fill and drain.
I'd be nice if there's a way to fill and drain without having to take it down off the spare.

This may take a little cajoling of my wife to let me get some of these.

 

[ducktapeguy]

Trailed 6-Gallon "Spare" Tank Overview & DIY Guide For 5th Gen 4Runner

Trailed 6-Gallon “Spare” Tank Overview & DIY Guide For the 5th Gen 4Runner Traveling into the backcountry by vehicle can be a safe and rewarding adventure if properly prepared. However,...

trail4runner.com

And I think they are stackable, so you could carry multiples...

I saw this before and was really considering it, I was under the GX looking at any areas I can stash a spare fuel can. Although I love the aux tank in my FJ40, in the GX I really don’t need an extra 35 gallons of the long range tank. All I want is a enough fuel just in case I am running low, so 6 gallons is more than enough and should be plenty to get me to a gas station no matter where I am. But after seeing some of the reviews the only thing stopping me was how much it decreases your ground clearance, I’m not sure I’d want to sacrifice that. I’d even be happy with slimmer 3 gallon version if it tucked away more.

 

[Tquiroz]

I am moving the spare to a rear swing arm. Is there anything wrong with fabricating a steel carrier plate to hold the batteries in that void? I was thinking of 1/4 inch steel.

 

[giovanni]

I saw this before and was really considering it, I was under the GX looking at any areas I can stash a spare fuel can. Although I love the aux tank in my FJ40, in the GX I really don’t need an extra 35 gallons of the long range tank. All I want is a enough fuel just in case I am running low, so 6 gallons is more than enough and should be plenty to get me to a gas station no matter where I am. But after seeing some of the reviews the only thing stopping me was how much it decreases your ground clearance, I’m not sure I’d want to sacrifice that. I’d even be happy with slimmer 3 gallon version if it tucked away more.

It only decreases ground clearance if you stack enough of them together to be thicker than the spare tire. You could just carry 1 (6 gallons) and it would tuck up much higher than the spare tire.

 

[giovanni]

It looks like one has to take if off, in order to use it. I don't think you can just leave it mounted and fill and drain.
I'd be nice if there's a way to fill and drain without having to take it down off the spare.

I think that would be called an aux fuel tank.