Any suggestions for this setup?

Howdy,

My wife, child and I love to camp – we generally base out of a Minivan (brand new 2014 Dodge Grand Caravan) and love primitive camp-sites. We were using ice-chests to keep food cool, but they are terrible and messy. Over the last year I’ve been acquiring items to help us eliminate that.

So here is my setup:

* CTEK D250S DUAL from starting battery (only running the positive and grounding on the frame – should I run negative back?).

* 110AH 12V Deep Cycle AGM battery.

* 12/24V Whytner Fridge (ran at 12V – I believe 6 amp draw?). The thing is pretty well insulated and I have yet to monitor its daily draw.

* CPAP DC battery that will need charged (not sure on specs).

* Rechargable AA’s and D cells using an AC charger (we have a 100W inverter available as needed).

* LED Christmas lights (my kid loves them at night – probably ran for 6 hours).

I was planning on adding a “Kyocera KD255GX-LFB2” panel to the mix also. Ideally we would never have to run the van. We also like to do overnight and two-day hikes while out camping, so I am hoping my setup would allow us to not have to worry about the deep-cycle dropping down below 50%.

Just wanted to throw this out there and get opinions.

Thanks!

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,601 admin
    Welcome to the forum Tesen!

    This is going to be a zero to 60 set of answers--Please ask for clarification where I do not make sense to you. I don't know your background in electricity/electronics--And I am probably taking some guesses too.
    Tesen wrote: »
    * CTEK D250S DUAL from starting battery (only running the positive and grounding on the frame – should I run negative back?).

    Frame grounding is very common in automotive world. You cannot (for example) buy a simple automotive radio that has + (red) and - (black) power wires... They assume that the radio is mounted to a metal frame and that is the negative/return wire (modern cars do have a lot of plastic--So that may have changed in the decades since I worked on cars).

    So--Running your return path through the sheet metal can work, but it is usually a poor idea. The use of plastics, rubber isolators, etc. can make for poor/unreliable connections. Most solar equipment you purchase should have two wire (+12 and - or battery return). It is usually best to bring all the return wires to a "bus bar" or battery negative connection.

    And for wires that go to each device (radio, fridge, lights, etc.) there should be a fuse or circuit breaker rated for the current capacity of the wire (i.e., 14 AWG wire would have 15 amp breaker/fuse if you follow the NEC--National Electric Code--There are other standards too).
    * 110AH 12V Deep Cycle AGM battery.

    Read the battery manual on proper charging voltage. ~14.4 volts at 75F is typical for AGM batteries.

    AGM's do not do well if over charged. And lead acid batteries do not like to be over discharged (avoid discharging too often below 50% State of charge, avoid ever discharging below 20% state of charge--That can ruin the battery).
    * 12/24V Whytner Fridge (ran at 12V – I believe 6 amp draw?). The thing is pretty well insulated and I have yet to monitor its daily draw.

    If you assume a 50% duty cycle:

    12 volts * 6 amps * 0.50 duty cycle * 24 hours per day = 864 WH per day

    That is a pretty heavy load for a small RV power system to run just from batteries/solar panels. If your 6 amps is wrong, or my 50% duty cycle is wrong--Then my guesses are wrong.

    Amp*Hour draw would be:

    6 amps * 0.50 duty cycle * 24 hours = 72 AH

    That is already drawing a 110 AH battery bank down to:

    (110 AH - 72 AH) / 110 AH = 35% State of charge for a single 110 AH battery

    The battery (if my guesses are near correct) could support the fridge for over night--But you would need lots of sun and possibly Aux Generator or Driving to help keep up. Or a larger battery bank (2x 110 AH batteries as an example).

    Refrigerator/freezers are highly variable in their power requirements. Hot vs cold weather, temperature of interior, insulation, amount of air flow around the condenser, how often it is opened, if there is warm food put inside, etc.).
    * CPAP DC battery that will need charged (not sure on specs).

    If you have a CPAP designed for battery use and don't use the humidifier, it may draw around 1.5 amps at 12 volts:

    1.5 amps * 8 hours per night = 12 AH

    If you have to recharge the CPAP battery from your solar/battery system, it may take 1.5x that amount of energy (AH) from your 12 volt battery bank (or ~18 AH).
    * Rechargable AA’s and D cells using an AC charger (we have a 100W inverter available as needed).

    If you use a 120 VAC charger, you can use a Kill-a-Watt type meter to measure the energy used.

    If you use a 12 VDC powered charger, you can get a Doc Watson type DC Watt*Hour/Amp*Hour meter.
    * LED Christmas lights (my kid loves them at night – probably ran for 6 hours).

    You can find some pretty low power LED Christmas lights. AC versions if you are running the inverter (inverter just turned "on" may draw more power than the lights) or look around for 12 VDC Christmas Lights (maybe 0.1 amps per string).
    I was planning on adding a “Kyocera KD255GX-LFB2” panel to the mix also. Ideally we would never have to run the van. We also like to do overnight and two-day hikes while out camping, so I am hoping my setup would allow us to not have to worry about the deep-cycle dropping down below 50%.

    To give you an idea of how much solar panel you would need for a reasonably sunny area (assuming no winter camping) in the south west US:

    110 AH battery * 12 volt * 0.50 discharge = 660 WH per day
    660 WH per day * 1/0.61 off grid DC system eff * 1/4 hours of sun per day = 270 Watt nominal solar panel

    So--You have a sort of close match to 50% discharge of your battery bank--But your loads (first guess) exceed the capability of a single 110 AH 12 volt battery. Refrigerators are a difficult load for small off grid power systems. Do some testing and see how much power it really does draw. Perhaps it is better than I guessed.

    Your thoughts?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • AudiomakerAudiomaker Solar Expert Posts: 100 ✭✭
    I wanted to weigh in on the OP"s question but changed my mind. The reason is that my answers didn't really answer his question.

    Ultimately my own experience brought something I had been through (and still go through) to the table.

    What that is... is how much effort and time am I spending to protect X amount of $ in food?

    My own solution... just for a day or two of camping... would be to re-write the menu to non-perishables.
  • scrubjaysnestscrubjaysnest Solar Expert Posts: 175 ✭✭✭
    Audiomaker wrote: »
    I wanted to weigh in on the OP"s question but changed my mind. The reason is that my answers didn't really answer his question.

    Ultimately my own experience brought something I had been through (and still go through) to the table.

    What that is... is how much effort and time am I spending to protect X amount of $ in food?

    My own solution... just for a day or two of camping... would be to re-write the menu to non-perishables.

    I have to agree, the new 110 volt ac/12 volt dc compressor refrigs claim a 2 amp draw but are $1000 plus through RV dealers.
  • littleharbor2littleharbor2 Solar Expert Posts: 1,692 ✭✭✭✭
    Couple things I might add from experience are 1, For charging rechargeable batteries use a pure sine wave inverter as a modified sine wave version will generally ruin your rechargeable batteries.
    2 these work surprisingly well, http://www.ebay.com/itm/30M-200-LED-RGB-Solar-Fairy-String-Light-Xmas-Wedding-Party-Garden-Decor-Lights-/381330756219?pt=LH_DefaultDomain_0&hash=item58c915927b. One small approx. 4" x 6" solar panel charges the battery pack for ALL night of nice light. Various twinkling patterns as well as full time on with the push of a button.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Couple things I might add from experience are 1, For charging rechargeable batteries use a pure sine wave inverter as a modified sine wave version will generally ruin your rechargeable batteries.
    2 these work surprisingly well, http://www.ebay.com/itm/30M-200-LED-...item58c915927b. One small approx. 4" x 6" solar panel charges the battery pack for ALL night of nice light. Various twinkling patterns as well as full time on with the push of a button.
    Flor those who ask "Why?"
    Many battery charges, instead of using a transformer to reduce the incoming voltage to the range needed for battery charging, use a series capacitor or electronic equivalent as a current limiter and voltage divider. The impedance of a capacitor to a sharp edge is far lower than its impedance to sine wave at 60 Hz.
    Result is high current or voltage spikes that can kill either the battery or the charger.
    Motors at least have an internal inductance to smooth out the current And except for filament vibration, incandescent lights do not care much.
    SMA SB 3000, old BP panels.
Sign In or Register to comment.