Solar & batteries ...

[jornvango]

The house battery in our Livin Lite truck camper has died after about 3.5 years of frequent use. Lots of boondocking during which it kept the fridge, LED lights, water pump, ... running for about 3-4 days before we needed to run the generator.

Now that we are considering another long trip (Europe possibly), we are wanting to upgrade our system. The goal is to be able to still do a lot of boondocking but with the added luxury of being able to charge the 110V appliances (camera batteries, laptop, ipad, cell phone) from the RV house batteries.

Being illiterate when it comes to anything electrical related, I've been researching and created the following list to show all (I think) we want to be able to run on a given day. Granted, this is definitely an extreme day so more than likely our actual usage will be less. In the list, the amps are DC amps. (=AC amps x 10)

1) iPad = 3A x 4 hours of charging or use daily = 12AH
2) Cell phone = 1.5A x 4 = 6AH
3) Laptop = 16A x 4 = 64AH
4) Dometic 3-way fridge running on propane = 3.5A x 24 = 84AH
5) RV water pump = 7.5A x 0.3 = 2.25AH
6) RV furnace = 12A x 3 = 12A x 3 = 36AH
7) LED lights = 10A x 4 = 40AH
😎 Camera = 4A x 4 = 16AH
9) RV radio = 4A x 2 = 8AH
10) Shaver = .67A x .3 = .2AH
11) Gas detector = 1A x 24 = 24AH
12) Inverter = .5A x 24 = 12AH

Total (extreme) expected AH needed per 24 hours = 305

Some questions ...

- First of all, does the above make sense on calculating what I think we need the batteries to provide every day (24h)?

- We are considering going with AGM batteries or golf-cart batteries. If we are not to use more than 50%, that means we need enough batteries to provide 305 x 2 = 600AH?

- If we are to consider installing solar, am I correct that we need about 6 panels providing 125W each? (our roof space is limited; definitely not enough room for 6)

- To charge our 110-120V appliances (iPad, laptop, ...) in the RV, we need an inverter. Will an inverter make the existing outlets in the RV work, or does an inverter have its own outlets where you need to plugin?
Any idea how many Watts the inverter needs to be?

Thank you!

[jornvango]

Thanks. If the solar will charge the batteries, it sounds like it's better to not turn the disconnect switch to OFF since the only item using battery is the gas detector. Although that may mean every morning the alarm will go off ...?

[time2roll]

jornvango wrote:
Thanks. So turning the battery disconnect to OFF will not prevent the solar from charging the batteries?

Solar should be direct on the battery and unaffected by the switch.

Solar controller generally should have the panels disconnected before you remove the battery. For some controllers this is critical.

[jornvango]

Thanks. So turning the battery disconnect to OFF will not prevent the solar from charging the batteries?

[996Pilot]

Check the T-105's -- open the caps and take a look at the acid (and level). If you're boiling them, that will set off the gas detector. Are you plugged in and charging off the charger (in addition to the controller)?

The literature for your charge controller states that for the first hour of the day it will default to Bulk/Absorption charge of 14.4V so it sounds like that's what's happening. I'm not sure I like that profile as it assumes the batteries are down and require bulk charging (even if they don't).

14.4V is fine for the T-105's for bulk and absorption rates. Make sure your water levels are always topped off. Look HERE for Trojans User Guide. It's very informative and helpful.

Lastly, it's much, much better to have a solar controller that allows battery temperature input in order to adjust charge profile for battery temps. Sounds like that ship has sailed and you've got what you got (never scrimp on the solar charge controller - batteries are expensive). Also, do you have a panel breaker installed? If so, you can turn it off as necessary to defeat the charge program in your controller. Not optimum but anything to treat the batteries right.

Top off the batteries, if you have the room, look at installing recovery caps on the batteries. Take care of those gems 🙂

[jornvango]

We went boondocking with the new setup this past weekend. We charged the laptop and ipad during the day time and the solar kept the batteries full. By the time we went to bed each day, the battery level; as indicated on the solar controller; showed 12.7V.

This morning, with the camper parked at our house and nothing being in use, the gas detector started beeping. (we heard it from inside the house so went to check it out)
Since nothing was turned on, I thought perhaps battery fumes being responsible? Is this possible?

I checked the solar controller and it showed the solar charging the batteries at 14.4V. This sounds high?

Thanks.

[JimK-NY]

jornvango wrote:
..
1) iPad = 3A x 4 hours of charging or use daily = 12AH
2) Cell phone = 1.5A x 4 = 6AH
3) Laptop = 16A x 4 = 64AH
4) Dometic 3-way fridge running on propane = 3.5A x 24 = 84AH
5) RV water pump = 7.5A x 0.3 = 2.25AH
6) RV furnace = 12A x 3 = 12A x 3 = 36AH
7) LED lights = 10A x 4 = 40AH
😎 Camera = 4A x 4 = 16AH
9) RV radio = 4A x 2 = 8AH
10) Shaver = .67A x .3 = .2AH
11) Gas detector = 1A x 24 = 24AH
12) Inverter = .5A x 24 = 12AH

.....

Most of these estimates are WAY WAY off.

1. ipad will run for hours and hours on a 4 AH battery
2. cell phone runs all day on 2 AH
3. laptop will run for hours on 4 AH
4. Cannot provide any info. I run a full compressor refrigerator on about 30 to 50 AH.
5. My water pump pulls about 3 amp and runs maybe 10 minutes a day.
6. RV furnace mine pulls 5 amps and I rarely use it more than a few minutes a day.
7. LED lights. I usually run about 1 amp of lighting. If I turn on lots of lights I might hit 2 amps.
8. camera?? I charge my DSLR batteries daily for way less than 1 AH.
9. RV radio most radios will be closer to 1 or 2 amps.
10. Shaver. don't own one. don't know.
11. Propane detector pulls about 1.5 AH per day.
12. Inverter...inverters waste at least 10% of the power provided. I try to stick with 12 volt appliances and rarely use anything but a very small inverter.

Not counting the shaver and refrigerator, I typically run all my devices for less than 20 AH per day. That includes a lot of laptop time and topping off the charge on several camera batteries.

[EsoxLucius]

Voltage meter? I don't want no stinking voltage meter. A real battery monitor tells you more about the condition of your battery(ies) than reading voltage conveniently and improperly.

[jornvango]

Correct, and it displays battery level so no need for an extra voltage meter.

[Bobbo]

The Overlander comes with a 30amp PWM controller.

http://gpelectric.com/products/overlander-solar-kit

[TexasChaps]

jornvango wrote:
Thanks everyone!

TO provide an update, we have taken the plunge and installed the following upgrades (for now):

- replaced 12V house battery with 2x Trojan T105
- 1x GoPower "overlander" solar panel 160W (we have room for one more if needed)
- 1700W GoPower inverter (the 1000W was out of stock)
- battery disconnect
- surge gard protector for when we hookup to shore power
- replaced Smittybilt tow bar with Blue Ox Alpha tow bar (to tow the Jeep)

We intend to keep an eye on the battery level by using our radios hack meter, but would like something hardwired.. not sure which one to get.

Anyway, many thanks for the great advice!

no mention of a charge controller.. ?

[jornvango]

Thanks everyone!

TO provide an update, we have taken the plunge and installed the following upgrades (for now):

- replaced 12V house battery with 2x Trojan T105
- 1x GoPower "overlander" solar panel 160W (we have room for one more if needed)
- 1700W GoPower inverter (the 1000W was out of stock)
- battery disconnect
- surge gard protector for when we hookup to shore power
- replaced Smittybilt tow bar with Blue Ox Alpha tow bar (to tow the Jeep)

We intend to keep an eye on the battery level by using our radios hack meter, but would like something hardwired.. not sure which one to get.

Anyway, many thanks for the great advice!

[LifeInsideJack]

Depending on your roof space and what you find "on-sale" there are larger panels out there. We ended up with three - 250w panels on a barter. These fit up there but they eat up the real estate quickly.



As for batteries we went with AGMs because these are in our cargo box which is accessible from inside. AGMs are sealed and do not require ventilation. In order to keep the wiring under control the batteries are very close to the charge controller (Schneider Electric, another barter item) and all that taps into the coach without long wire runs.

We purchased additional 12v outlets and have them wired in the back room where our desks are. We went online and purchased 12v power adapters for our computers, scanner and printer and my camera battery charger.

My girlfriend being an Electrical Engineer has this thing wired tight and well over-designed. The good news is that panels are out there on the used market as well as the rest of the equipment needed to get up and running. We're currently trying to barter for a new Outback inverter. Inverters are everywhere but true sine wave inverters seem to be a little more difficult to obtain for "free".

Get an idea of what you would like and then start looking around at what's available. It'll all come together nicely.

[996Pilot]

jornvango wrote:


Being illiterate when it comes to anything electrical related, I've been researching and created the following list to show all (I think) we want to be able to run on a given day.......

Funny calling yourself illiterate regarding electrical. You've done a great job of approaching this problem using the absolute most practical method you could use (although your amp draws may be a bit inaccurate). Sizing a system is ALWAYS about calculating the DRAW first, then sizing the battery bank second and finally sizing the solar panels for replenishment last. I used to have a spreadsheet I used for sizing systems used for off-grid living in Mexico and it worked perfectly. Don't forget to add inefficiency in wiring losses, charge controller, panel cleanliness/angle, etc. I used the panel wattage X 80% as a rule of thumb. You need to look at higher voltage panels (rather than 12V) and using an MPPT controller in order to get the power density necessary in a small(er) footprint. Also, if using multiple higher voltage panels, you can run them in series (for even higher voltage) and reduce the wire gauge size.

I'd recalc your draws (as others have suggested) and also look at "time of use" of those draws (daytime during recharging or nightime as a pure draw) in order to get a more accurate DoD of batteries. Don't forget to crank in a bit of inefficiency in DC wiring and general wear of appliances over time. If you have room for Trojan T-105's then you may have room for T-145's (just a bit taller) and get a bit more storage (if that's the way you're leaning).

You're on the absolute right track for "right sizing" a solar system - don't let anyone say any different with your approach. It is a practical, solid approach that just needs a little tweaking on the numbers. Please keep us appraised of your results.

[MrWizard]

if you look close
i think the RE version has a different warranty, than the GC version

example your OFF GRID and have solar, you buy the RE version, and get a better warranty because the batteries are always getting some charge every day and less likely to be dragged down to ZERO and damaged