Derek from Affordable Batteries & Radiators replied:

You will be about 30 amps short per day. This would be around 2 hours with the generator and a good smart charger. I would also recommend a 2nd battery if you are using 85 amps per day.

I have not seen a 123W folding panel.

Have you got details.

Regards

Derek.

mowing replied:

Sayo, I am no expert but this is how I see it.
Your solar panels will give you around 50 amps of power provided you have them in the sun for the whole time (ie facing the sun track) . You get 80% approx out of the battery ie 96 amps so on day one you start with 96amps + 50 amps - 85 amps = 61 amps remaining. Day two- 61 amps + 50 amps - 85 amps = 26 amps. End of Day two/ start of Day 3 hook up a quality charger ie smart charger and the gennie as you are about flat. Don't forget that the solar panels are charging in sunlight hours where your drain may be at night. In short you are behind by 35 amps a day.
As I say I am no expert just my humble view.

Regards

Mark

Member - Mike DID replied:

"solar panels to use 85amps a day with a 120amp agm battery "

this is like saying you will use 85litres-per-hour per day from a 120litres-per-hour tank.

Amps is a measure of instantaneous power flow.

If you want to avoid mistakes, it would help to use the correct units.

I assume what you mean is 85 amphours per day from a 120 amphour agm battery.

Member - John and Val W (ACT) replied:

Sayo,

As others have said, your question isn't as clear as it might be! As I understand it, you have a load of 85 amphours (Ah) per day, 120 Ah battery and 123watt (W) solar panels.

My comments - 85 Ah seems very high. My rig uses about 35Ah and that's mainly the fridge. Are you perhaps assuming that the fridge will pull current continuously?

Your battery - although it may be rated at 120Ah it will have a very short life if you routinely use more than about 2/3 of that. In any case, if you try to extract the last few Ah out of it, the available voltage will be too low to run a fridge. In a real world situation you will probably not get more than 100 Ah from your 120Ah battery.

The solar panels - These are rated at their maximum power level, which occurs at about 17 - 20 volts. For battery charging we can't use such high voltages - I could start an argument here, but very few batteries should be charged using more than about 14.4V. The maximum current is still available from the solar panel, but the battery will load the panel so the voltage (and hence the power) is reduced. When the battery is fully charged and it's loading on the panel diminishes, the panel voltage rises and your controller operates to limit/stop the charging current. Because you can only use about 14V (average), not the 17-20V where maximum power occurs, you won't get the 123W from the panel, maybe 100 under optimum conditions. The panel should deliver about 7 amps tops, for perhaps 6 hours per day if you keep it aimed roughly at the sun.

That's 42 Ah you can harvest on good days, about half your 85 Ah load. With this input, a fully charged battery should hold things together for 2 days.

Options - reduce the load, fit an extra battery to extend your capacity, extra panel might provide 100% of power, run a generator with a good (3 stage) big charger every couple of days.

Suggest check your load and find ways of economising. (If you can halve your load you can be 100% solar while the sun shines.)

HTH

John

Member - sayo(NSW) replied:

hi guys
thanks for input bit the bullet after much deliberation and bought 80 watt sharp panel for van roof and another battery, with a folding solar panel on order,whats money if not for spending

Member - sayo(NSW) replied:

ah yes another question
have heard of a lot of different discussions on brands still undecided