Small system for tent camping

[Ikk]

I am working on a small system for tent camping. I currently have a 68 watt unisolar flexable panel. and a Duracell 600 powerpack 28 amp hour battery. I am trying to decide two things will this type of system be sufficient for my purpose and what inexpensive solar controller to include with this system. I may want to add another 68 watt panel in the future or something a bit larger if I find it at a good price. I plan on currently using 4 goal zero led lights that take 1/4 amp each and a 12 volt shower (not sure of energy consumption). I assume the lights will be used for around 4 hours per night and the shower 1 hour a day 6 showers, at 10 min, being conservative. I usually camp a week at a time in woody areas in central California for but can usually find sunny areas within camp. I would like to be able to top off my battery daily. There will be times I will be able to charge the battery while driving and connected to the car.

I am not sure if I should go with a PWM or an MPPT. From what I have read PWM makes more sense with how small my system is. At the sametime, I don't want to spend a lot for something I will use a few times a year and maybe for emergency purposes if the power goes out to light the house at night. but MPPT has its advantages as well. Any advice will be appreciated.

[thastinger]

You'll first need to determine exactly what your loads are in watt hours before the folks here can help you design your system. The unisolar "panel" you have will likely operate significantly below peak power if you lay it flat on the ground so if that is your plan you will want several more of them. How do you lug that battery around in the woods? If you just camp and don't need to pack up the battery to hike someplace with it, once I figured out my loads, I would just buy enough batteries to get me thru the week and charge them at home before I left each time.

To partially answer your question though, you wouldn't have to have a charge controller to charge a 12V battery from that panel but you would have to manually monitor the battery for state of charge.

[Sunking]

I am not sure if I should go with a PWM or an MPPT. From what I have read PWM makes more sense with how small my system is.

First thing is look at the specs of the panel particularly Vmp and Voc. If Voc is greather than 18 volts you are going to have top use MPPT. Sounds like you have a thin film panel which operates at higher voltages.

[thastinger]

I think the voltage of those film panels he has is in the 16V range and a little more than 4 amps? He could hook that directly to the battery no? Especially if the panel is flat on the ground and won't be producing at peak.

[Ikk]

I would be camping close to the car. As for the panel, I would hang it from my EZ up canopy, truck, or my tent to give it the best angle to the sun. As for the solar panel it's a pvl-68. VMP=16.5V Voc=23.1V. As I would be away hiking, kayaking during the day I would not have time to watch the battery. I basically want to plug it in and have it charge until I need to use it.

[PNjunction]

I do much the same thing for convenience with Sears Diehard and Stanley jump starters that have a ups-style AGM inside. All you need is a controller.

YES, you will need a controller. I suggest that for your existing panel, a Morningstar Sunguard 4.5A pwm charge controller. It is totally potted, yet still has temp-comp and is high quality. The absorb voltage is about 14.2 volts, and although I like it a bit higher for agm's like 14.7v, this will do fine for a non-critical setup. Keep the charge controller very close to the battery pack.

I suggest charging via the cigarette-lighter jack, rather than the dc input jack, which has a current limitation. Panel > Morningstar CC > Duracell cig lighter jack.

I also run the Goal Zero led lights. Yep, about 250ma each (3 watt). You want to run 4 at a time, so that's a nice even 1ah draw. Most people don't want to draw down the battery beyond 50% capacity, so that would mean with 4 lights running you could run for 14 hours. Since nightime isn't that long, that leaves you a little bit left over for your shower (unknown current draw), and would suggest opportunity charging during the day.

If you want to live like a king, instead of the bluish led lighting, consider a portable light that will accept a 10 watt CFL bulb and run that from the msw inverter!

Just be sure to take into account your solar insolation hours while camping depending on location, season, and obstructions. With your current setup, if you drew down to 50% SOC, you would be able to just barely make it back to 95-100% charge IF you had a full 4 hours of strong direct sunlight. Solar insolation is different from visible daylight, so if reaching a full charge is important, be sure to see solar-insolation hour charts for your destination. Also take a decent portable digital voltmeter with you if you want to keep track of the resting OCV of that agm to get a ballpark figure of what the state of charge is - since you don't want to just kill that internal battery.

The age of the agm's sitting inside the jump packs can be questionable, so if possible, you may want to look into replacing the internal agm (if accessible) with a fresh one from a reputable manufacturer and dealer. I suspect that the usb outlets (high power 2.1a - nice!) have their own switch - so just like the inverter, do not leave them active when not actually using them.

[thastinger]

I do much the same thing for convenience with Sears Diehard and Stanley jump starters that have a ups-style AGM inside. All you need is a controller.

YES, you will need a controller. I suggest that for your existing panel, a Morningstar Sunguard 4.5A pwm charge controller. It is totally potted, yet still has temp-comp and is high quality. The absorb voltage is about 14.2 volts, and although I like it a bit higher for agm's like 14.7v, this will do fine for a non-critical setup. Keep the charge controller very close to the battery pack.

I suggest charging via the cigarette-lighter jack, rather than the dc input jack, which has a current limitation. Panel > Morningstar CC > Duracell cig lighter jack.

I also run the Goal Zero led lights. Yep, about 250ma each (3 watt). You want to run 4 at a time, so that's a nice even 1ah draw. Most people don't want to draw down the battery beyond 50% capacity, so that would mean with 4 lights running you could run for 14 hours. Since nightime isn't that long, that leaves you a little bit left over for your shower (unknown current draw), and would suggest opportunity charging during the day.

If you want to live like a king, instead of the bluish led lighting, consider a portable light that will accept a 10 watt CFL bulb and run that from the msw inverter!

Just be sure to take into account your solar insolation hours while camping depending on location, season, and obstructions. With your current setup, if you drew down to 50% SOC, you would be able to just barely make it back to 95-100% charge IF you had a full 4 hours of strong direct sunlight. Solar insolation is different from visible daylight, so if reaching a full charge is important, be sure to see solar-insolation hour charts for your destination. Also take a decent portable digital voltmeter with you if you want to keep track of the resting OCV of that agm to get a ballpark figure of what the state of charge is - since you don't want to just kill that internal battery.

The age of the agm's sitting inside the jump packs can be questionable, so if possible, you may want to look into replacing the internal agm (if accessible) with a fresh one from a reputable manufacturer and dealer. I suspect that the usb outlets (high power 2.1a - nice!) have their own switch - so just like the inverter, do not leave them active when not actually using them.

Not to jack the thread but I use one of the portable power stations for races. I think the wall charger adapter lists 18V and 1A as the charging input, I'm wondering if I could make an adapter and plug the panel into the charger, assuming the internal regulating CCA of the charger could handle something higher than 1A.

[Sunking]

I would be camping close to the car.

You have no reason to even use a solar panel. Just buy a good deep cycle battery properly sized to run your loads a few days and a plain ole float charger to keep the battery charged up at home. If you get in a pinch at camp site use jumper cables to charge the battery. Your vehicle alternator can generate more power in 10 minutes than a 70 watt panel can generate in a week.

[Ikk]

Not to jack the thread but I use one of the portable power stations for races. I think the wall charger adapter lists 18V and 1A as the charging input, I'm wondering if I could make an adapter and plug the panel into the charger, assuming the internal regulating CCA of the charger could handle something higher than 1A.

You can connect up to a 30 panel through the cig lighter port. No charge controller needed.

I would supplement car charging when out and about if needed. Since I already have a panel and battery why not use it. I am trying to use this for experimental purposes as well. I am thinking of this as a great learning tool for myself and 6 yo son. As I learn more, if possible i may expand my system and purchase a 12 volt fridge in the future.

[PNjunction]

You can connect up to a 30 panel through the cig lighter port. No charge controller needed.

Nope. The Xantrex manual (makers of the Duracell 600) states that a maximum 30w panel (2.5a) can be connected to the ac charger input socket. It will then use the internal charge controller already in it to keep voltages below 15v, which agm's do not like exceeding.

For example, despite having an 18v wall cube (either internal or external), my Diehard's internal controller runs 14.7v bulk/absorb, and then drops to 13.8v float. The Stanley units also limit voltage to under 15v, and in fact are just float-chargers running at 13.8v all the time.

Should you use your 68w panel, (approx 4a under best conditions), you'll need to go through the cigarette lighter jack. Low-voltage Unisolar or not, I would still heartily recommend a charge controller for use with a connection through the cigarette lighter jack. Xantrex makes them. I use a C12 myself for one of my projects. I think the Morningstar 4.5a Sunguard would also be a great way to start.

Experimentation is great and without a controller (if using the cigarette lighter jack) it is likely you'll be able to charge that battery - for awhile at least even though you are stressing it out. But if you want some life out of it, you'll want to know your battery specs - especially if that unit does not have a user-replaceable battery option. I noted that this model is discontinued, and that the copyright on the manual is from about 2007, so I have my doubts about the age of the internal agm which could have been sitting on the shelf discharging for years.

You can find the specs for your battery usually printed on it's side. If it isn't there, Xantrex may be able to help. Even then, these units all use basically the same ups-style general purpose agm's inside. I heartily recommend getting the technical manual from Power-Sonic:

http://www.power-sonic.com/technical.php

Even if your duracell does not directly use a power-sonic internally, this manual is very very close to nearly all the other small scale agm ups-style batteries out there. You'll find that charging above 15v is generally not liked very well, and hence the need for a controller - either internal, or if your panel exceeds the internal current limit, then you'll want to go directly through the cigarette port, but you'll want an external controller.

[Ikk]

Has anyone heard of or used a Genasun mppt charge controller. For an mppt controller they are inexpensive, small, and made in the USA.
http://genasun.com/all-products/solar-charge-controllers/for-lithium/gv-10-li-lithium-10a-solar-charge-controller/

This would fit nicely with my system. A little more then I wanted to spend but if its a true mppt it may be worth it.