Adding A Second Battery

Randy

Randy

Ranger
Donating Member
It will be obvious from my questions that I know nothing about electricity so please forgive me. How does a second battery work? Do they function as one battery? That is, does the camper draw from both evenly and do they run down at the same rate?

Will the CampInn battery charge indicator reflect the status of both batteries together?

What about charging? Will my solar panel with built-in controller (I have a 130 watt panel) charge both batteries? (I don't have the CampInn controller but do plug my panel into the solar CampInn solar receptacle) When plugged in or towing, will both batteries charge?

What's the best way to wire them, series or parallel?

Finally, where do your store the second battery and how do you secure it?

Thanks,

Randy
 
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You have opened a big subject with lots of nuanced items. If you want to have two batteries simultaneously connected, the first thing is that they both have to be very similar, if not identical. If not, the charging and discharging will be uneven, one battery may not charge, and it may even damage one of the batteries. Given that both batteries are of the same type and capacity, they should be connected in parallel. This way they will both charge and discharge together and your capacity will be doubled, your charge indicator will be good. All systems will perform as before, just more capacity.

However, in order for this to work well, they should be permanently connected. If you connect a fully charged battery to a discharged one, there will be a lot of current that starts immediately that could damage wiring and connectors so anything other than a permanent connection can be dangerous. In order to do this, you need a permanent place to add the second battery and wire it up, and the Camp Inn is so efficiently and compactly designed, there really is no easy place to put the second battery; the best place that I can think of is to dedicate the bottom of the galley counter storage bin next to the existing battery. You could build a false bottom into that compartment and put your battery there but you would lose a significant amount of galley storage. If you don't have water tanks it would be possible to build a tray for batteries under the galley where the tanks would normally be.

An alternative to this is to have a completely external battery; there are some on the forum who have done this, search around and you can get some ideas. The external battery will have to be maintained and charged separately from the internal battery.
 
There are many ways to approach this; I obsessed about it during the long wait for our trailer to be built. The first thing is to ask yourself is what problem you are trying to solve. What consumers of electricity to you have, what is your camp situation, length of stay, etc.? Is there a specific problem, or simply range anxiety?

For us, the only significant consumer is the fridge, I replaced all of our lights to LEDs and so the only other thing that uses a measurable amount is the fan. Our solution is to keep the fridge in the TV. While the trailer may sit in camp for days at a time, we usually go somewhere in the tow which charges up it's battery. I installed a battery protection device to insure the ability to start (at the expense of the fridge) if the charge is not soon enough. This happened to us only once and the fridge is well enough insulated that our food was fine. The other advantage is we have our lunch with us! Our trailer battery has kept a very high charge level even after a week's stay without any charging.

Once the problem is defined, an approach can be developed for your situation with appropriate design trade-offs.

(Please excuse the engineer speak, it's in my blood.)
 
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I also have the engineer disease so my solution was to get more data. To that end I installed a Trimetric battery monitor so I always know the battery state-of-charge. I keep the dometic plugged into the trailer. On a month-long trip last October through some hot areas we had no problem with running the battery down too far. In Death Valley it was actually kind of fun to watch the solar panel (85 watt) try to keep up with the dometic. It did very well but convinced me that a 120 watt panel would offer useful headroom and generally faster charging.

Rotus8, where'd you get your LED bulbs? We've got the xenon fixtures and it would be nice to cut that power consumption down.

thanks,

r dickson
550 #645
137 nights, 30,946 miles
 
We switched all of our lights to LED bulbs. The white cabin lights are advertised as dimmable, the red is listed as non-dimmable, but they dim just fine with no flicker or noise. The cabin lights are about the same brightness as the original Xenon bulbs. The running lights however are crazy-bright bright making for an awesome porch light and hopefully better visibility on the road.

Running Lights

Red Cabin Lights

White Cabin Lights
 
I believe Ted (Rotus8) covered it perfectly. One must first determine the load needs and decide why they would need to expand their battery capacity. Most people would never need more capacity, especially given that their tow vehicle charges when driving. However some loads like electric fridges and CPAP machines will shorten the run time considerably and could cause a need for more battery capacity. This is typically why a solar panel is being put to use by some users.

As for adding a second battery there can sometimes be a need but generally we would try to dissuade people from this. Short bio here, I worked for 13 years as an engineer for a power back up company designing battery strings and cabinets prior to Camp-Inn. This is an area that I have some knowledge on. Here is a hard fast rule of battery strings that must be followed. Batteries in a string must be not only the same size but should be the same manufacturer, part number, age and even if possible same batch code. Introducing a battery into a string that is not identical will create a great load on all that will shorten the life of all batteries rather shockingly fast. Adding a second battery would be doing exactly that which is why we would frown on the ideal, even if you could find a place to put it. The correct way of accomplishing this would be to replace the factory battery with an identical one to the one you are adding. So, if considering some sort of second battery solution I would hold off until your current battery is due for replacement.

For a couple people who have found a need for an extended run battery solution the external pony battery carried in a marine battery box Ted suggested is exactly what was done and what we would suggest also. The catch to that is being careful about the strings again. If doing a external battery my suggestion would be to make it so it switches from one battery to the other, kind of like dual fuel tanks, so the two batteries never get strung together. Then the second pony battery would need to get charged separately with a bench style charger or other charging means other than the trailer's charger. I believe Frank P has a great thread on here on installing an external pony battery.

Cary
 
this brings up another issue that I had to deal with, which is that my TV (VW cheater diesel Jetta wagon) doesn't put out high enough voltage to fully charge an AGM battery. These batteries need a specific charging profile to get *fully* charged. This includes a voltage of 14.6 or so. I doubt most cars do this. A solar panel will, however, as well as the charger built into our trailers.

If you repeatedly fail to fully charge your battery it will decrease its capacity over time. I managed to decrease the capacity of the original AGM battery so that it wasn't useful with the dometic in not much more than a year.

r dickson
 
Thanks for chiming in Cary. I think it's good advice to wait until I have to replace the original battery which is still working great and buy two identical ones.

Randy
 
fernlane said:
this brings up another issue that I had to deal with, which is that my TV (VW cheater diesel Jetta wagon) doesn't put out high enough voltage to fully charge an AGM battery. These batteries need a specific charging profile to get *fully* charged. This includes a voltage of 14.6 or so. I doubt most cars do this. A solar panel will, however, as well as the charger built into our trailers.

If you repeatedly fail to fully charge your battery it will decrease its capacity over time. I managed to decrease the capacity of the original AGM battery so that it wasn't useful with the dometic in not much more than a year.

r dickson
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This is sounding somewhat familiar to us. When we are traveling, we generally only tow about 50 miles per day, so we don't get the sort of charging from the tow vehicle that most people experience. If our Ford Transit Connect also doesn't put out a high enough charging voltage, then we've got a couple of things working against us. We've struggled to keep the battery charged on solar power when using the Dometic, and this may point at the reason. Thanks for sharing!

We are contemplating adding 200 watts of solar to our van, which potentially could help both our trailer battery charging (and eliminate the need to set up and secure a portable solar panel at each campsite) and a separate issue with our van battery discharging too much (because the running lights, including those on the camper when the 7 pin plug is connected, come on whenever any door is opened). We suspect this is a safety feature for min-vans (to alert traffic to a clueless person getting ready to exit the vehicle), which is what our cargo van was before it landed in the United States. We've checked with Ford, it can't be altered - we are stuck with the way it works.

So....
Can anyone tell me how to go about tying the solar panel wiring into the charging line that comes from van's battery (is there some sort of special controller necessary, aside from the controllers on the panels)? And whether doing so will allow the van's battery to also be charged (or would the battery isolator prevent that)?

Any help would be greatly appreciated, especially any specific recommendations for necessary equipment.
 
while traveling in the southwest last fall I started contemplating mounting flexible PV panels on the trailer. We'd drive hours through bright sun and get to the campsite with less than a fully charged battery. If I could charge the battery from solar panels while driving that would solve most of my charging problems.
I found some 50 watt panels that would fit nicely on either side of the vent fan. Pricey, but so is replacing group 24 AGM batteries. Solar Flex Kits | Go Power!

[I saw an Alto (very cool - if you haven't seen one check out Safari Condo) with big solar panels a couple of years ago. The owner said they did a great job keeping his batteries charged.]

Then there's the problem of wiring the panels into the charging system. I expect it would have to be an either/or situation where I'd charge from the TV or the roof panels while towing. I'd still likely carry a freestanding panel for extended campground use.

Something to think about anyway.

r dickson
 
The flex panels are interesting, but after visiting Go Power, I'm thinking the Overlander might be more in tune with our needs. We can go with a single 160W panel, rather than two 100W panels. And it is possible to charge two battery banks, which sounds like it might be capable of charging the camper battery and the van battery (that would really be cool if it could give priority to the camper battery). Now if I can just figure out a way to get some degree of comfort that it will work the way we want it to, and we'll be ready to pull the trigger in the spring.

We aren't interested in mounting panels on the camper. There are advantages to that, but I'm not interested in introducing any potential new leaks. It is simpler to avoid leaks in the van, and with no headliner it is real clear what is going on if a leak does develop.
 
Cary and team installed a solar inlet when we had our trailer made.

We have recently added Solar to our Raindrop kit. We opted for a commercial grade 120 watt, 24-volt panel. This panel is coupled to a SunSaver MPPT solar controller that can handel either 12, 24 or 36 volts panels. The increased voltage allows for small gauge wires and reduced $$$ savings over retail 12 volts panel systems. My buddy who is a solar expert has helped us with the purchase, technology and install of the whole setup. Our rig nets us about 9-amps per hour on a sunny day and since we are using only about 25 amps on a busy battery day, we are more than covered for our electrical demands. Our panel is on a 30-foot, 12 gauge extension power cord. This allows us to park camper in shade while placing solar panels in the sun. Since the setup is completely mobile and portable, I can use it for a second function of powering my HAM radio setup, completely separate or in conjunction with the Teardrop.

Hope this helps those those thinking about solar.

IMG_1064.webp
 
I like the way you kept the original cigarette plug socket, and use it for the meter. I've never liked having to use an adapter in order to have both the meter and our Dometic on the socket in the galley.

What is the brand of 24v panel?
 
re solar panel to charge battery while driving:
I understand the trepidation re mounting panels on the roof of the TD, but what about mounting to the roof of the TV? Seems that the issue would be how to run the charging cable. And perhaps solar panels aren't engineered to be driven down the road at 60 mph.....
 
AlCat said:
What about mounting to the roof of the TV?
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Why would you want to do this? If it is just because of limited storage other places, it might be OK, especially if the panels are protected in a box, cover, or self storing (folding). If you are thinking having panels on your TV and actually charging, it is silly. The vehicle has a fine charging system connected to the motor. Any power generated by panels on the roof would be insignificant compared to the loss in gas mileage from having a big wind blocker on the top of the vehicle.
 
Rotus8 - This thread suggests a possible reason why on newer vehicles you might want to consider adding solar on the TV - obviously it isn't an issue on your classic pick up.

AlCat - We have been hemming and hawing on whether to add solar to our TV. Cary and Craig have been hugely helpful in explaining how to do this. Basically you tie into the charge line going to the camper. But there is a potential issue with connecting to mismatched batteries if you die directly into the line. They provided me with a part number for a $3 relay switch that would solve that problem, complete with a schematic of how the relay would be wired. It connects the panel to the charge line with the ignition off, and connects the generator to the charge line with the ignition on. If we had installed that and had any experience with it, I'd post the specifics on the forum. But if you want to send me a PM I'd be happy to share.

Also, nearly every RV nowadays has solar mounted on the roof. So flying down the highway at 80 miles an hour shouldn't be a concern. They are only mounted a few inches above the roof deck, so I suspect the extra drag would be fairly minimal. At any rate, we haven't seen any canned solutions for fairing the leading edge to reduce drag, though we've looked for them...
 
rotus8 said:
Why would you want to do this? If it is just because of limited storage other places, it might be OK, especially if the panels are protected in a box, cover, or self storing (folding). If you are thinking having panels on your TV and actually charging, it is silly. The vehicle has a fine charging system connected to the motor. Any power generated by panels on the roof would be insignificant compared to the loss in gas mileage from having a big wind blocker on the top of the vehicle.
Click to expand...

My batteries do not charge well from the TV, and some other folks have the same issue. One member has postulated that it relates to some TVs putting out too little juice to effectively charge the AGM battery, and, as a result, the AGM battery develops a "memory" that is lower and lower each time, diminishing the output of the battery. See this thread for the description of the TV outputt angle: Battery And Tv (tow Vehicle) Output

I agree that mounting panels on the TV roof would damage MPG, but I'd be willing to do that if it meant that I had a full battery when I got to the next campsite.
 
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