I've owned a 60L fridge/freezer for some years and have done extensive power consumption testing on it; set at -12C/+2C it uses between 25Ah and 60Ah per day depending upon ambient temperature. My modern laptop consumes about 1A so say 4Ah per day. Sundry other stuff, lighting, water pump, charging etc say 10Ah per day. So worst case is:

60 + 4 + 10 = 74Ah x 13V = 962Wh

Therefore your 120W panel will need 8 hours of perfect sunshine per day - not going to happen.

In reality (say) 300W of panel will put out about 250W in good sunshine so you would need 4 hours of sun to meet your worst case needs - and that's 4 hours of good sun with no shade and the panels being regularly rotated.

 I am in the process of upgrading my solar and have come to the conclusion I am always going to need a generator for top-ups here in Victoria where I spend most of my time.

Note: run the freezer at -12C not -18C this is good enough to keep food safe for three months or more and uses a lot less energy.

As said above, you can't have too much solar & batteries for inclement weather.

The limiting factor is payload & or room. We are in a car only. So our opinion was to make our fridge as efficient as possible, with additional insulation & increasing wire thickness within the fridge to reduce resistance. Up to 15AH per 24 hours.

If needed we can run the car engine to charge up the batteries, but as we tend to move after 4 days maximum, charging happens by default.

Our 12O watt setup typically puts out 9amps into the batteries via Victron MPPT & up to 11.3amps under perfect conditions. We built quality instead of the cheap Chinese rubbish. Who wants to be remote with third rate rubbish.

We have also built in redundancy, multiple everything & 6awg & 4awg wiring. It's overkill, but it is the easiest way to squeeze blood out of a stone.

Welcome mate,

The more the better combined with a quality solar charger as amplified here so far.

There is lots of info on this topic here.

Good luck!

Use a short section of lighter cable that will fit into the terminal blocks. It will have more resistance but it's not an issue being a short length. Better to have the bulk of the run heavy enough.

iana wrote:

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Just remember any weight added to the roof of a van particularly full height vans will have the effect of raising the center of gravity, and hence will effect stability.

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 I don't think that will be an issue with my camper trailer and free standing panels, but good point,

Hi all; After camping for a week in south Tasmania over the queens birthday weekend and with 240 watts of solar, 440 Ah of agm batteries i found that i was running out of power. The weather was rain, drizzle and fog that did not lift for several days and bloody cold as well. I also have a 20 Amp DC to DC charger, but you need that connected to the car to be able to charge. Ended up borrowing one of the other campers gen set and 15Ah smart charger. This helped a lot.

On returning home i ended up purchasing a smart 30 Amp charger and wiring that into the house batteries. This put in just over 300 Amps over around 10 ~12 Hours, so the house batteries were probably down in charge because of insufficient charge for the week away. The batteries are just on 2 years old at the moment. My van is now connected to mains power while at home and so the smart charger is on but with full batteries the charger now is in sleep mode with the batteries at 100% fully charged. I also purchased a smart bridge that monitors the charge/ discharge of the batteries and also gives a readout like a fuel gauge as to the capacity of the batteries.

So charging the house batteries at home is not a problem , but free camping, that is were i now also have a 2Kw generator that plugs into the mains input of the caravan. That will only be used if and when the house batteries get down a bit to far and require charging during the day. I just plug the generator into the mains input on the caravan and the battery charger takes over and starts charging if needed.

I have the usual things in my caravan, led lighting, tv and sat receiver, diesel heater and more led lighting outside, and finally a 40 ltr Engel fridge. A small inverter ( 300 Watts ) for recharging the computer or my for my electric shaver. Gas for the fridge when camping and hot water/cooking.

The smart charger and smart current bridge are also able to be bluetoothed to my phone and i can check on the state of the batteries and the action that i may need to take. So looking forward to our next trip away and free camping and further testing on my set up.

peatop wrote:

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I think the sooner I change to lithium the better the system will cope with the problematic discharge amounts created by extended low input of cloudy or shaded days. and also the use of a solar blanket and or one of those flexible panels as your backup.

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Lithium batteries will not provide better support than lead acid; unless energy in equals or exceeds energy out you are going to run out of power.

I looked at solar blankets long and hard and decided not to buy one; they appear to be always significantly over-speced and, it seems, most (all?) are not waterproof!

Isn't the idea behind Lithium about usable power more than the amount you use? meaning that if I have 2 x 100ah batteries my estimated usable amps before recharge is 100 amps before damage occurs to the batteries, where if I have the same in Lithium then I have up to 160 amps usable amps (still not sure on the correct figures), this give you some protection for low solar output during extended periods, ofc you still need the capacity to fully charge them but you have more usable amps therefore longer time to wait for the weather to clear, shade change or you move locations charging your batteries via your dc to dc charger ect.

I guess the heading give the wrong idea my bad, It should perhaps read "solar, building in redundancies" I'm just trying to limit issues with power created buy unseen circumstances (gotta keep that beer cold).

peatop wrote:

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Isn't the idea behind Lithium about usable power more than the amount you use? meaning that if I have 2 x 100ah batteries my estimated usable amps before recharge is 100 amps before damage occurs to the batteries, where if I have the same in Lithium then I have up to 160 amps usable amps (still not sure on the correct figures), this give you some protection for low solar output during extended periods, ofc you still need the capacity to fully charge them but you have more usable amps therefore longer time to wait for the weather to clear, shade change or you move locations charging your batteries via your dc to dc charger ect.

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 This fallacy of only being able to discharge an AGM (or other lead acid battery) to 50% of its rated capacity is rubbish. You can safely discharge AGM batteries to zero rated capacity (10.5V) without damage.

The life of AGM batteries is best measured in total power in and out, not by depth of discharge or cycles.

The lithium will hold a higher voltage for deep discharges and that may be useful if you are running high power appliances.

Cheers,

Peter

Look at the battery data sheet for the battery. The total life watt hours of the battery is not a great deal different to whether you discharge 30%, 50%, 80%.

Peter_n_Margaret wrote:

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laurieoz wrote:

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 Hi

Where do you get the technical data from that you can safely discharge AGM batteries to zero without damage?

Why is 50% always (from what i see) quoted

I would like to read technical papers

Laurie

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 Multiply cycles  x Ahrs per cycle to find total life in Ahrs.

Cheers,

Peter

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 Thanks

I seem to read all the time you should not take battery below 50%