# Solar panel help.....



## Mike Jones (Jul 25, 2017)

Hello all, this is my first time posting and asking for assistance, so please be patient. Recently i purchased a used solar panel that I'd like to use to keep my rv batteries charged while camping for 10+ days. It is a HYM-90 panel that has a black box and cord attached to back. At the end of the cord is a FEMALE 20 amp plug. The maximum power voltage is 17.9V and the maximum power Current is 5.03A. I'm thinking that I will need a charge regulator or something so the batteries don't over charge, but honestly don't know much. Please help......


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## Al Yaz (Jun 13, 2017)

yes a small charge controller will do the job. something like or similar to this... you can just cut off that end and wire directly to the charge controller.


https://www.morningstarcorp.com/products/sunsaver-mppt/

i have several of these on the property. i pair them to a 50 watt solar panel and then use them to keep the vehicle battery charged.
https://www.solar-electric.com/ss-6.html


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## Mike Jones (Jul 25, 2017)

Al Yaz said:


> yes a small charge controller will do the job. something like or similar to this...
> 
> 
> https://www.morningstarcorp.com/products/sunsaver-mppt/


Thank you Al Yaz! One more question.... do i.just cut the plug off to expose the wires needed to connect to the charge controller, and then connect from the controller to the batteries?


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## Al Yaz (Jun 13, 2017)

yes sir. that’s what i have done on all of mine. i have four of them spaced out around the property. one keeps my diesel generator battery charged. one keeps my utv battery charged, one keeps the batteries on my boat charged and one is sitting idle right now cause... well long story 

i use ‘battery tender’ style plugs to and from the vehicle battery to the charge controller. makes for easy plugging and un-plugging.

if you have an ac/dc meter you can make sense of everything and check everything before plugging in. imho, spend a few extra cents on a fuse on the hot line coming off the battery, just to be safe.


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## Mike Jones (Jul 25, 2017)

Al Yaz said:


> yes sir. that’s what i have done on all of mine. i have four of them spaced out around the property. one keeps my diesel generator battery charged. one keeps my utv battery charged, one keeps the batteries on my boat charged and one is sitting idle right now cause... well long story
> 
> i use ‘battery tender’ style plugs to and from the vehicle battery to the charge controller. makes for easy plugging and un-plugging.
> 
> if you have an ac/dc meter you can make sense of everything and check everything before plugging in. imho, spend a few extra cents on a fuse on the hot line coming off the battery, just to be safe.


Again, thanks so much for your help! I appreciate it man!!


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## wy_white_wolf (Oct 14, 2004)

If you cut the cord off the solar panel it will void the warrantee. 

Don't forget to add a fuse as close to the battery as possible. 7 to 10 amp should handle it. A single panel doesn't require one between the panel and charge controller.

WWW


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## Meinecke (Jun 30, 2017)

I think those panels are out of warranty already for a while...
But love the project...
Doing similar stuff with my off grid chicken coop as learning project


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## Murby (May 24, 2016)

Charge controllers are nice but not absolutely required for small setups like this... If you're attaching this to a full size deep cycle battery and using the battery all the time, the charge controller will probably be a waste of money as your panel might not be big enough to even keep the battery fully charged.. again, depending on how much you use the battery I guess.


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## Mike Jones (Jul 25, 2017)

Thank you all for your input. This project is really just to top off my batteries in my rv while up hunting for 10+ days. If this will work, I will be happy with the results!!


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## wy_white_wolf (Oct 14, 2004)

Murby said:


> Charge controllers are nice but not absolutely required for small setups like this... If you're attaching this to a full size deep cycle battery and using the battery all the time, the charge controller will probably be a waste of money as your panel might not be big enough to even keep the battery fully charged.. again, depending on how much you use the battery I guess.


IMHO Very bad advise.

There is only 2 times one can get away without using a charge controller.

1. Panel voltage is below the maximum charge voltage of the battery. With a Vmp of 17.9 it is well above the maximum charge voltage of any lead based 12V battery.

or

2. The panel amperage is low enough as to never off gas "boil" the battery. That rate is somewhere around C/50 to C/75 depending on the manufacturer and type of battery with GEL and AGMs always requiring one. C/50 would put that battery size at @250AH and C/75 being 375AH.

With small PWM charge controllers only costing in the $20 or less there is no reason to go without one. They not only protect your battery but also all equipment connected to it from over voltage.

WWW


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## Murby (May 24, 2016)

wy_white_wolf said:


> IMHO Very bad advise.
> 
> There is only 2 times one can get away without using a charge controller.
> 
> 1. Panel voltage is below the maximum charge voltage of the battery. *With a Vmp of 17.9 it is well above the maximum charge voltage of any lead based 12V battery. *


That makes little difference.. the battery is going to drag down the panel voltage to whatever the battery voltage is.



> or
> 
> 2. The panel amperage is low enough as to never off gas "boil" the battery. That rate is somewhere around C/50 to C/75 depending on the manufacturer and type of battery with GEL and AGMs always requiring one. C/50 would put that battery size at @250AH and C/75 being 375AH.
> 
> ...


This is why I said "if you're using a full size deep cycle battery".. The panel current is only 5 amps and that would be the rating he would get IF he's located at the equator of the planet, at noon, under full sun, with the panel perfectly positioned. (Like that's ever going to happen)
In reality, the panel will probably produce around 3 amps, maybe 4 amps and it will only do that when the sun is perfectly positioned for an hour or two.. the rest of the day will probably show current flows at 3 amps or less.

A 3amp charge on a full size deep cycle battery can be left on all day long and it won't boil anything away.. Even a full 5 amp charge on a deep cycle battery would take hours and hours assuming the battery was already at a full charge.

On the other side of the coin, a charge controller, while they sound cool and allows one to have more gadgets hooked up, is going to waste energy on its own just doing its thing.. it also adds more stuff to bring with you, and more connections, more wire, and more things to go wrong.

If he's not hooking up a 200 watt panel to a motorcycle battery, he has nothing to worry about...


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## Mike Jones (Jul 25, 2017)

Thank you all or the advice. IF I were to get a charge controller, what size? Is a 10amp 12/24V enough?


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## wy_white_wolf (Oct 14, 2004)

Mike Jones said:


> Thank you all or the advice. IF I were to get a charge controller, what size? Is a 10amp 12/24V enough?


Yes. Just needs to be 125% of the panel ISC rating with PWM.


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## Mike Jones (Jul 25, 2017)

Perfect! Thank you so much! I have purchased a 10 amp 12 / 24 volt charge controller that I will hook up. What size of inline fuse do I use before the battery?


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## Al Yaz (Jun 13, 2017)

I use 7.5 amp fuses on my set-ups, without any issues. Hopefully someone will suggest if that is suitable for your purpose.


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## Mike Jones (Jul 25, 2017)

And do I only use one inline fuse on the hot lead only between the charge controller and the batteries?


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## Al Yaz (Jun 13, 2017)

if you are really concerned about protecting the charge controller i guess you could put an inline fuse between the solar panel and the controller and one between the controller and battery, just on the hot lines. i have mine wired to an off/on rocker switch so i never have to connect/disconnect my battery when the controller is under load. murby or wy white wolf will know a lot more than i do so hopefully they chime in.


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## Murby (May 24, 2016)

1 fuse is all that's needed. Once you break the path, its broken.. period.. 

I still say the charge controller is a waste for what you're doing.... I think its going to rob you of precious energy from your small panel and create a lot of things to go wrong. More connections + more wire = more failure points and more resistance.


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## wy_white_wolf (Oct 14, 2004)

Mike Jones said:


> Perfect! Thank you so much! I have purchased a 10 amp 12 / 24 volt charge controller that I will hook up. What size of inline fuse do I use before the battery?


Fuse between the charge controller would be 125% of the controller. So 10A * 1.25 = 12.5A. You can get by with smaller since your panel only puts out 5 amps so that would be 6.25A min. You wiring also needs to handle 125% of the fuse so if you put in a 12.5A fuse you wiring needs to handle 15.6A.

Battery is the only power source large enough to do damage so that's the only place a fuse is needed. As close to it as possible. Any loads should have a fuse mounted there too sized to handle them.

WWW


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