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Have 160W Solar- Think I need More

solar zamp fwc hawk batteries

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#1 cloudzrest



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Posted 24 October 2019 - 01:41 AM

Hi Everyone, I'm new to the forum and need some help with my FWC Hawk.  


I bought a 2017 Hawk about 6 months ago, it has 160W solar and two AGM 79amp/hr batteries with the 30amp Zamp charge controller.  When I'm camping off the grid, the solar can't keep the batteries fully charged, and progressively the batteries end up low after 3-5 days, voltage has gotten as low as 10.8 on the batteries.   I have a 2 way fridge and LED lights and water pump and do some phone USB charging.  


I'm thinking I need to add another panel up on the top of the camper, mounted to the racks, or possibly get a portable panel to plug in to the rear of the camp at the solar plug.  I'm not sure about mixing different brands of panels (ie OEM hawk solar panel and a Renogy), or if I can just "plug and play" a portable solar panel to the rear of the camper without any other modifications.  


I'd appreciate any advice or insight. I want my batteries to stay charged up for at least 5+ days.  Many thanks !  


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#2 ckent323


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Posted 24 October 2019 - 08:55 AM

Chronic undercharging of batteries leads to premature failure.  Deeply discharging batteries or leaving them undercharged for weeks will lead to sulfation.



In general, sulfation starts when a battery’s state of charge drops below 80%, or 12.4 volts. Recharging a battery in a timely manner helps prevent sulfation.


A properly sized and designed system should provide sufficient power to fully recharge your battery bank everyday.  That may be a combination of solar, alternator or grid power depending on your particular use habits.  If you occasionally draw down your battery bank over successive days for some reason (weather, heavier than normal use, etc) it is not as big of a concern as if you frequently draw down your battery bank over successive days.    


Never let a 12 volt battery discharge below 12 volts.  A fully charged battery is 12.7 volts. When a battery reads below 12.2 volts it is at or below a 50% state of charge.    A 12 volt battery is essentially fully discharged below 11.9 volt

The following chart is conservative




Here is another chart that is less conservative





Reducing the batteries depth-of-discharge increases the life of the battery. A battery discharged to 50% everyday will last twice as long as a battery cycled down to 20% everyday. The following table is for Concord high quality deep cycle batteries (Rolls-Surrette, Crown and other high quality batteries will be similar).  Note that these are best case numbers based on lab testing.  It is reasonable to assume actual performance may be 2x worse (i.e. only 500 cycles at 50% SOC).




Also it is very important to fully recharge your battery bank between trips or before storing your camper.


In summary, Yes I think you need to increase your solar capacity. 

I recommend that you create a power usage table. Use your battery monitor (Victron BVM, or equivalent) to determine the power draw from each item in your camper.  Determine how long you use each item and calculate your typical daily power needs.  Then size your system (Solar, or combination ) to provide at least that much power so that your batteries can be fully recharged everyday.








Edited by ckent323, 24 October 2019 - 09:07 AM.

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#3 Happyjax


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Posted 24 October 2019 - 11:46 AM

Excellent info Craig!


May I suggest an external portable panel to supplement your rooftop :)I remember reading about Zamp wiring their plug backwards from industry standard.....??? You would want to check polarity before plugging in but I think as long as that matches and you are using the same voltage you can use any panel.....


Someone correct me if I'm wrong!

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#4 Advmoto18


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Posted 24 October 2019 - 12:01 PM

Craig has posted a lot of great info!


There are hundreds of posts here to help you sort things out.


Indeed, avoid discharging your batteries below 12.2V. 


Sadly, it only takes a few deep discharges below 12.2V to dramatically reduce the useful longevity of the batteries.  10.8V is dead as a door nail and will be very difficult to get batteries to 100% capacity after such a deep state of discharge (except LiFePO4).


I suggest learning as much as you can about the components in your system (to include wiring).  You will then be able to identify weaknesses and either upgrade components or learn to live within the system parameters.


I then suggest learning how to use your system to maximum effectiveness.  Avoid shade (trees, Fantastic fan pop-up cover, etc) on even a single cell on the panel;  depending on the panel, shading a single cell can dramatically reduce the panel's effectiveness.  


Don't leave lights on when not needed.


The frig will have a huge draw on stored energy.  I discovered the difference between the cold setting of 2 and 3 to have a significant impact on the state of charge of the camper batteries.  As such, I rarely have the frig (2 way) set colder than setting #2.



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#5 roverjohn


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Posted 24 October 2019 - 01:13 PM

Does "2-way fridge" automatically mean 110v/12v now? I ask because I always thought it meant 110v/propane in which case he should have plenty of solar.


If I were the OP I would look at trying a MPPT controller and then think about 'aiming' the panel.

A lot of people get by just fine with a 160 watt panel but they are likely optimizing better than this guy.

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#6 Beach


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Posted 24 October 2019 - 02:19 PM

Another issue that has a huge affect on charging is shading of your panel. Most of us like to find a nice shady spot when camping which directly impacts the amount/rate of charge. Hook up a volt meter to your panel output and just shadow the panel with your hand or a sheet of paper, you be surprised at the drop in output.

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#7 Bigfoot Dave

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Posted 24 October 2019 - 06:10 PM

Having a battery/solar system without good metering is like driving in the dark without lights on. Your panel could be failing, your battery is probably failing, your wiring is probably undersized, You might have corroded connections and you don't know whats wrong. I would really recomend reading up on the articles on this site. Before I found WTW I found "Handy Bob RV". His articles are an interesting read but he is spot on on his advise. I installed a Trimetric meter and solar charger with properly sized wire. Even in northern Minnesota my batteries are back up to 100% by noon every day and show decent charge on rainy days. There are other options for meters and solar controllers. Some are good and some not so good. 

Good luck, Bigfoot Dave

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#8 rando


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Posted 24 October 2019 - 06:51 PM

I will second what others have said. - you really need a better picture of what is going on through a real battery monitor.


I have a 160w panel. and it keeps up for me in the Sunny rockies, but depending on where you camp and how much sun you get this may definitely not be the case for everyone.     Adding a second panel (with similar specs) in parallel with the first should get you where you need to be and your current charge controller can handle it. 



PS I have said this before, but there are better resources out there than 'HandyBob'.   Much of his advice is seriously out of date (he doesn't believe in MPPT or Lithium) and his screeds are painful to read. 

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#9 Stokeme


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Posted 24 October 2019 - 07:26 PM

Consider this battery monitor. Got this recently for my son (budget alternative to Victron). He seems to like it so far & is much closer to an electrical guru than myself. 2nd Rando’s recommend to add a portable panel, brand does not matter, impt w/similar specs, through your back wall solar plug. Plug & play as long as your are running things parallel in 12V. Get some 10awg solar cable to run your panel. Forgive me if I am repeating too much of any of the above info. Very impt. to check Zamp polarity (& in general) as I have read similar.
Screeds! My new vocabulary word of the week .....


Edited by Stokeme, 24 October 2019 - 11:03 PM.

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#10 pvstoy


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Posted 24 October 2019 - 08:34 PM

No time to get into the weeds, But, you do need a good battery monitor to know what is going on in your system.


I suspect your battery voltage is dropping too low that the installed battery separator will not kick in to have the truck alternator help charge your batteries when it is needed the most.  Your 160 watt panel should keep up and you can suspect the charge controller, battery health, and how much you are using to effect overall performance.


This where knowing your system and what to expect out of each part is going to pay off and a battery monitor will help collect these values.


Until then use a volt meter and check voltage when the truck is running, when the panels are generating power.  Amps in and out are something that is important to note in your system, A battery monitor is a easy way to record this.  Something is failing be it battery or charge controller, as your camper is 2017 it must have worked fine until you noticed it was not.

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