Solar Panel Volt & Amp Help

[cantgetaround]

hi, i have been using a 4.5w solar panel to keep my deep cycles topped up but i have just noticed it does not keep them up but there slowly getting flat, they were at 10.8v on a half sunny day.. my problem is what to buy, on ebay i have noticed a couple of panels....

my dad has this panel and it works great , ebay Item number: 271000758353
Max Power 50W
Max Power Voltage 18.00V
Max Power Current 2.78A
Open Circuit Voltage 21.60V
Short Circuit Current 2.99A
Nominal Operating Cell Temp -45 to 80 ºC
Max System Voltage DC600V
Max Series Fuse 9A
.............................

ebay Item number: 270853022237
Max Power: 60w
Max Power Voltage: 25V
Open Circuit: 23.2V
Open Circuit Current 2.41A
Max Power Current: 2.4A
Max System Voltage 1000V
Cell Technology: Mono-Si Application Class 10A

my system is 12v x 2 deep clycle batterys, sometimes 1 when i disconnect the box for more room in the back of 4wd, im thinking the 60w would be better due to the higher voltage i dont know.. any help to choose the best one would be great thankyou...

[Tiny]

Either of those 2 panels will do the job.

You will need a small regulator or controller to prevent overcharging.

Assuming your batteries are connected into the charging system of the 4WD with an isolation diode, if your batteries are reading 10.8v on a half sunny day with no load draw on them, then they are dead flat & shouldn't be.

If they have been slowly getting worse, they are probably dying.
The 4.5W solar panel you have been using to keep them topped up may be far too small for their capacity & your usage.

The first thing I'd do is charge them up fully with what ever charger you have, then see how they test up.
If they are still in good shape after fully charging, they should have an OCV of 12.6V or slightly higher for some types of cell.
OCV = Open circuit voltage, means no load or charging device connected & should be measured no sooner than 30 min after disconnection of charger &/or load.
The cells may need an equalisation charge to recover them if they have been tortured.

Another thing to look into is that a lot of deep cycle batteries are manufactured as stationary batteries & not intended for vehicle use as the constant movement will damage them.

If you need more help, some more info would be helpful.

What size are the batteries?
What age are they?
Are they connected into the vehicle charging system?
If so, are they correctly isolated by a diode?
What type & size of load are they used for? ie; fridge (constant draw) or camp lighting (occasional draw).?

[cantgetaround]

hi tiny,
#both batteries are 130amp agm
#both 8 months old from new when i got them
#yes i am charging them from the 4wd via a 140amp isolator that connects and charges when the main battery is charged and disconnects once all batteries ( main,2xdeep cycle) are level
#i have a 140amp isolator for charging the deep cycles
#i do have a engle eclips fridge freezer, it run till cold then starts and stops when need to keep temp at where i set it, these used around 2 times a month >> 3x10" led lights a 26" led tv/dvd and 12v antenna.

i will try the charger on them and see if they hold.. my charger can be charged at 2/6/10/12/15 amp, it is a ACDleco l-7012 with maintance function

i got a solar regulator from ebay that is as follows:

Rated charging current 10A
Rated load current 10A
Work voltage 12V;24V auto switch
Over load, short circuit protection Over load protection action: 1.25times rated load current in 60-sec, 1.5 times rated load current in 5-sec; Short circuit protection action: >=3times rated load current
No load current <=6mA
Charging circuit voltage drop <=0.26V
Load circuit voltage drop <=0.15V
Over voltage protection 17V, x2/24V
Work temperature Industry stage: -35℃ to +55℃
Boost charge voltage 14.6V; x2/24V(keep 10-min) (Only applied when overdischarge appears)
Direct charge voltage 14.4V; x2/24V(keep 10-min)
Float charge voltage 13.6V; x2/24V(keep working until drop to the point of charge return voltage action)
Charge return voltage 13.2V; x2/24V
Temperature compensation -5mv/℃/2V(Boost charge, Direct charge, Float charge, charge return voltage)
Lower voltage indicate 12.0V; x2/24V
Over discharge voltage 11.1V no load-real-time modified voltag

this solar regulator is same as mine.. ebay Item number: 261020276556

[Tiny]

All of that sounds like a great setup.
You won't get a better camping fridge than an Engle.

My only concern is the 10.8v reading you got.
Was that under load or charge?
May be worth checking out if the charging system from the vehicle is operating correctly as well.

So go ahead & charge the batteries up, check your manufacturers specs for boost & equalisation charging as AGM's are different to flooded cell batteries.
Usually a tad lower on the boost & equalise.

See if they test out OK.

The reg sounds good as long as your battery specs are close to those preset charging voltages.

Had a look at those ebay panels both look OK, the small amount of extra input from the 60w may be beneficial for the extra $5.