Anyone Carry a Spare Battery?

ScottG

I'm curious if anyone takes the simple approach of carrying a spare charged deep cycle to swap out when there's not enough sun to keep up the charge.

Not only would the spare double your off-grid camping time without a charge, the discharged battery could be moved into the sun, brought someplace where it could be plugged into a charger, or--if you had an appropriate vehicle--even carted around and recharged from your T/V's generator.

Of course, swapping out the battery would be a pain, but this could be a low tech/low cost solution for those who only have room for one battery and tend to camp a lot in the trees.

Photomom

Interesting idea, an extra battery would take less space than a generator or solar panels. 

Verna

Yes, it does sound like a good idea for those shaded areas. 

I’ve been thinking about purchasing two extra 6V golf cart batteries and an inverter for my woodworking while camping, @ScottG.  In a pinch, the power cable could be moved to connect them to the “house cables” instead. Flexible solar panels sound good to charge them. No, I haven’t quite figured out the placement yet. Obviously, this is still in the thinking, not planning stage. 

There are heavy duty battery cables with a plug that you could purchase so that you could just unplug from one battery to the other, rather than disconnecting the wiring from one battery to another. 

pthomas745

I carry a small 35AH AGM in a battery box as an "extra" battery.  I charge little things like camera batteries, the laptop, phones, and even a small fan while outside.  It is easy to move around and has a small footprint on the floor inside the trailer.  At one shady campsite I was able to move this small battery and the panel into better sun to charge it up. 

Is there an easy way to plug a recharged battery into the Tab's power system without having to remove the battery in the propane tub?  I'm thinking something like a Y-connector.  If there was, I think carrying a larger spare battery would be useful.

ScottG

@Photomom, I still plan to carry and use my 100W solar panels. So far they have worked well for me, but I have a trip coming up that's over a week and the site may have poor exposure (not to mention poor weather). I'm  thinking a little insurance policy might be in order. I've no interest in the bulk, noise, and fuel required to run a generator.

@Verna, good idea--I'll have to ponder a convenient cable switch-a-roo set up if this idea comes to fruition. The spare battery would need to ride in my truck bed, as there's currently no room on the T@B. I'm thinking of creating a cable that plugs into the 7-pin trailer connector and runs up into the bed to charge the spare while I'm out driving around. (A fancier approach would be to install an inverter and outlets in the truck bed so I could use a 120V charger. Don't some Tacomas come with those as an installed option?)

ScottG

Thanks, @pthomas745. I didn't figure I was the first person to think about this, so somebody had to be doing it.  :-)

I'd also like to avoid having to switch the heavy batteries (I have a 100AH group 27), though my current idea (admittedly not very thoroughly thought out at this point) would involve having to remove the discharged battery anyway for external charging. I do like the idea of some kind of quick disconnect, though.

Verna

@ScottG, search on “battery quick disconnect” on Amazon. That’s the type of a connection I already have for the inverter I plan to use (I’ve gotten that far in my pre-planning).  It takes a 6 to 10 gauge wire, so you should be able to fit the two or three positive wires into the positive side. 

Sharon_is_SAM

We ran into a Canadian couple with a Tada out in Utah.  They had a spare battery that they switched out as needed.

Tabster

Yes .I have a 155 ah deep cycle battery in my truck bed. It is identical to the battery in my t@b.  I have a 120 w solar panel mounted on the truck cab that feeds the battery. I have a 10 guage cable with an SAE connector attached to the battery  I can plug it into the zamp jack and have 2 155 ah batteries in parallel  

Verna

@ScottG, my 100/400 inverter in my truck bed is off when the engine is off....at least that is my understanding. I’ve never tried it. 

rfuss928

I thought this was a slick set up.  The battery box had a 7-pin socket that allowed the trailer to be plugged into it.  A special double ended cord was made to allow it to be plugged into the TV when charging was needed.  The female 7-pin connector and a disconnect switch were built into a basic plastic marine battery box.

Basically you can put it in the rear of you TV while running around and put by the trailer when needed using the wiring that already exists in your TV and T@B.

jkjenn

I have my Goal Zero Yeti 1000 which could be used to provide a little juice, in a pinch. I have never needed anything more than the 2, 6 volt batteries with my 200watts of solar. I am sure it is possible that I would need it, but that is part of the reason I went with an MPPT controller. 

ScottG

No argument that two 6V GC batteries are the optimal solution. I've definitely got that in mind for a future upgrade. It's a bigger mod than I'm interested in tackling right now, as creative solutions would be called for to get the batteries to fit.

Right now I'm just looking for lazy man's insurance policy. Not that there's anything "lazy" about moving those batteries around!  :-)

Dalehelman

@ScottG
I just double stacked a second battery on top of the stock one. Then added a duel battery disconnect switch.

ScottG

@rfuss928, that's a far more elegant version of exactly what I was thinking. Am I correct in assuming when you plug in to the T@B's pigtail you would want to disconnect the other battery as it would be in a different state of charge?

@Dalehelman, thanks for the tip. I'll have to check and see if I have room to stack a second box in my current configuration. It would be good if I could fit them both in the tub, though I still would want to maintain the portable charging option.

On a tangential note, if you don't plant to remove the batteries is there an advantage to not just wiring them in parallel so you you can get the extended amp hours without having to actually switch the batteries with the disconnect? That's another approach I've considered down the road if I can't get the larger 6V units to fit.

rfuss928

ScottG said:

@rfuss928, that's a far more elegant version of exactly what I was thinking. Am I correct in assuming when you plug in to the T@B's pigtail you would want to disconnect the other battery as it would be in a different state of charge?

ScottG - This question could easily trigger long discussions.

Basically, if two batteries of different state of charge are connected in parallel, they will equalize over time.  The greater state of charge will charge the lesser.  No harm will be done to either battery.  Probably not the most efficient use of available energy but many other variables will influence what is best practice in any given situation.  I would probably leave both connected hoping to leave the on board battery in a better state after disconnecting the portable.

ScottG said:

On a tangential note, if you don't plant to remove the batteries is there an advantage to not just wiring them in parallel so you you can get the extended amp hours without having to actually switch the batteries with the disconnect? That's another approach I've considered down the road if I can't get the larger 6V units to fit.

I have two 12v AGM batteries in parallel on board.  They are wired through a selector switch which allows both, either or none to be connected to the trailer.  I very rarely have moved the switch from the "both" position.

Have fun!!

Bob

rcuomo

Interesting that a six year old (3/12) battery is still in use. Another reason to use AGM. 👍🏻

ScottG

Thanks, @rfuss928. That a long enough discussion to confirm my understanding of the setup.  :-)

Another thing I recall about using two batteries in parallel is that they should be the same model and in the same state of age/health, so I'll be looking at two new batteries when/if I go that route. 

rfuss928

rcuomo said:

Interesting that a six year old (3/12) battery is still in use. Another reason to use AGM. 👍🏻

The second battery is 18 months older!

I had them both performance tested at the beginning of last season and they still exceeded the original specifications.  I am very satisfied with this choice!

ScottG

Here's my prototype. It's very similar to what rfuss928 posted above, minus the battery box with integrated connector.

I appropriated a spare 10g electric dryer pigtail for the main cable. Only the 12V and ground lines are hooked up at the trailer connector. This is long enough to sneak from the 7-pin plug, behind the bumper and under the tailgate into the truck bed where ring terminals connect it to the battery needing a charge.  Add in a 30A fuse on the positive line, and this is identical to the T@B's battery charging circuit, minus the T@B.

Yanking the battery so I can drive around with it is a bit of a pain, but at least I have this as a last resort for charging if solar just isn't cutting it on longer trips.

rfuss928

ScottG

That's kind of interesting/funny!!  I have sort of the opposite/complimentary part.

I carry this "adapter" that gives me access to the T@B's batteries from the pigtail.

I just plug the trailer in and I can connect a charger or solar or even a 12v accessory.

It came to exist on a trip when the converter failed.  This plus a 12v auto battery charger clipped to the black and white wire kept things running smooth for the rest of the trip.  The 2 pin SAE was recently added for use with a maintainer.

My batteries are in sealed boxes in the bottom of my closet.  This is a much easier path to connect.

Have Fun!

Bob

Ratkity

Since your vehicle can only trickle charge a battery, it would take a long time to sufficiently charge a battery. Even 8 hours wouldn't be enough. I sometimes carry a spare battery, but it's fully charged. Even the generators that come with a battery charger are very inefficient (but necessary to run sometimes when on private property and it's been cloudy and rainy).

rfuss928

Ratkity said:

Since your vehicle can only trickle charge a battery, it would take a long time to sufficiently charge a battery. Even 8 hours wouldn't be enough.

Auto alternators/charging systems are powerful and capable of 30 or more amps - many much more!  The wiring to the 7-pin connector is usually fused some where between 15 and 30 amps depending on the vehicle and the installation.  A couple hours of driving can easily recover a deeply depleted battery to 80-90% capacity.  Way more than a "trickle charge"!

Sharon_is_SAM

@Ratkity, our Tab battery took at least 10 hours to charge while driving.  There must have been voltage drop due to the distance of the wiring from the TV to the Tab battery.  I think Scott and Bob’s set up with a short wire is the difference in charging ability.

ScottG

I guess I'll need to rely on empirical testing to determine if this is a viable charging method or not. Deciphering the fuse box in my truck is challenging, but I agree with rfuss928 that the current capacity of the charge line is certainly more than a trickle charge (typically <2A). How this translates into actual charging ability remains to be seen.

A bigger confounding issue may be the voltage regulation built into modern automotive generators. If the generator output is stepped down to 13V or less, charging capacity will be reduced. Prior discussions here suggest that this may be at the root of inadequate power to run the fridge on DC. I've yet to find a reliable way on my vehicle to lock the generator into a constant 14.4V.

Coming back to my original post, this was really part of a larger idea to incorporate a second battery that could be swapped out while the dead battery gets charged remotely.

Regardless, if all goes well on my next week+ trip, solar will do it's job and the new cable will stay untested!

rkj__

My tow vehicle, a 2008 GMC Canyon does not give a lot of charge to the battery.  While I have not made any effort to gather solid data, what I can tell you is this.  I've verified that the wiring is connected. Plugging into the tow vehicle does raise the voltage displayed on my battery meter plugged into the T@b.  But, after driving home for around 3 hours after a trip that nearly depletes the battery to 50% charge, it is nowhere near fully charged after the drive home. 

rfuss928

rkj__

Something is wrong!!!

It would take an 8 to 10 amp constant draw to deplete a std T@B battery to 50% in three hours even if you did not have a charge line. 

Where is all that power going?

Sharon_is_SAM

Well, if rkj had a 320s with the three way frig, I would say the frig on DC can draw 11 amps.  But he has the CS and tge frig on DC is more efficient.

ScottG

I think he meant he started with a depleted battery, drove three hours home, and found the battery was still not fully recharged.

rkj__

ScottG said:

I think he meant he started with a depleted battery, drove three hours home, and found the battery was still not fully recharged.

Yes, that is what I was trying to say.  I drain the battery to ~50% charge, while camping, disconnected from all power sources.  Then, I connect to the truck, drive for three hours, and arrive home, with a battery that is definitely not fully charged.  I've not paid close enough attention to give exact voltages before and after the drive. 

This qualitative anecdote is probably not too helpful, but I thought I would share anyway.  Your results may vary, based on tow vehicle, alternator, wiring, battery health, battery capacity, loads while traveling, etc.

Ratkity

The dynamics of batteries are that they can't charge any faster no matter how much power you have, well, not without exploding.

On a regular battery charger, with no loads, a 50% depleted battery needs an overnight charge to come as close to 100% as feasibly possible. You can easily get to 85-90% in a much shorter period of time, but the last 10-15% is squished into the battery at a much slower rate. 

Continue to run your battery to 50% and then doing a short charge to 85% will drop the life of your battery by years. Not a big deal if you have generic deep cycle that you haven't invested a lot of money in, but it's a big deal when you have invested a lot of money in 2x 6V batteries or the 400's battery type (I don't know the group number, but it weighs a lot!). Well, the 6V's are heavy too. Ok.. well, heavy to meeee! LOL.