Redarc Solenoid & solar charging.

Guys,

I have a 110 amp auxiliary battery under the bonnet, and an another in a portable battery box that I use occasionally, which plugs in the back, and used if I'm camping for more than a couple of days. The Radarc solenoid is simply and works well isolating the start battery, while the alternator keeps them all charged.

Question : I'm thinking of adding a 300w solar to keep the auxiliary batteries topped up while camping for longer periods. People have suggested changing my charging system to a DC-DC charger to keep everything fully charged, and to have the advantage of the in-built solar controller.

I like simple, so the solenoid seems the best method for me, but I do like the idea of a solar panel. In my case, would it be as simple as connecting a solar panel, via a controller, to the auxiliary under the bonnet and only switching it on when camped? I don't see the need to have to working all the time, as the alternator is keeping the batteries charged.

The only disadvantage I can see is that most solar controllers need to be connected to the battery/s first so it can determine the voltage ( 12v or 24v ) before the panel is connected. So if I put a switch on the solar controller I would need to go through this procedure every time I wished to connect it.

Does this all sound right & workable?

I agree, the simple solenoid is simple, but the DCDC charger isn't much more complex. A couple of extra wires, and it's a set and forget setup.

The inbuilt MPPT function of a Redarc (example) BCDC charger, is above and beyond any controller that comes with the solar panels... It sucks any possible "Raw" volts out of the panels and boosts them up to keep the batteries charged / topped up.

Also, some dcdc chargers, for example I have a CTEK D250S, and when i have a solar panel plugged into it, and the AUX battery is charged , it will also back-charge my Main battery too. DCDC chargers have come a long way and honestly they are a good investment.

Yeah, I have the CTEK 250 system with the panel inlut, permanently wired so its pinging the batteries when sitting around, and the hardware has the charging smarts as well to look after the health of the batteries with multi stage charging.

If it ain't broke don't fix it...

You obviously have enough camping power at the moment without the Cranker so leave the Redarc

I would add a connector (if it doesn't already have one you can use) to the Battery Pack and connect the Solar there.
That will top up the Aux and the Pack.... aaand... if you use a common style connector to what you use for plugging in the pack then just plug in the Solar to charge the Aux when the Pack isn't in place.

300 watts is a lot of solar so you will need at least a 25 amp MPPT Reg or 20 Amp PWM (300 watts is on the cusp of 20 amps for MMPT).
If the Reg that comes with the panels is a reasonable one just use that (at the Battery end tho not mounted at the Panels).
True MPPT Regs are expensive and in 90 % of camping use don't add all that much charging power (the theoretical figure is up to 30% BUT you won't see anything like that outside the lab).

MPPT (under about 1,000 watt systems) is the ducks guts if you have high voltage panels (32 volts or more) or don't track the sun like roof installs on houses/vans etc.

PWM is fine if you only use 12 volt panels (18 to 20 volts or so) in parallel and track the sun a couple of times

DC DC Charging, expensive but has its place, note that it will not have much effect on your solar (just saves you having an external Reg) and as you are getting sufficient performance already is not necessary. Certainly a consideration if you want to upgrade or need to buy an MPPT.

From Victron
PWM

The PWM charge controller is a good low cost solution for small systems only, when solar cell temperature is moderate to high (between 45°C and 75°C).

MPPT

To fully exploit the potential of the MPPT controller, the array voltage should be substantially higher than the battery voltage. The MPPT controller is the solution of choice for higher power systems (because of the lowest overall system cost due to smaller cable cross sectional areas). The MPPT controller will also harvest substantially more power when the solar cell temperature is low (below 45°C), or very high (above 75°C), or when irradiance is very low.

FWIW... I use MPPT (usually Victron) on my fixed array sites where for whatever reason I am limited for panel size and need to milk as much juice as I can.
Whenever I can use larger panel capacity I use PWM (usually Morningstar).

The MPPT sites are good for maybe 10% possibly 15% more juice... hard to put a figure on it as it differs from month to month... MPPT is def better in the south of WA tho, but PWM closes the gap the further North you go esp Kimberley/Pilbara

Wot @ET said .

Quote:

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Originally Posted by the evil twin

If it ain't broke don't fix it...

You obviously have enough camping power at the moment without the Cranker so leave the Redarc

I would add a connector (if it doesn't already have one you can use) to the Battery Pack and connect the Solar there.
That will top up the Aux and the Pack.... aaand... if you use a common style connector to what you use for plugging in the pack then just plug in the Solar to charge the Aux when the Pack isn't in place.

300 watts is a lot of solar so you will need at least a 25 amp MPPT Reg or 20 Amp PWM (300 watts is on the cusp of 20 amps for MMPT).
If the Reg that comes with the panels is a reasonable one just use that (at the Battery end tho not mounted at the Panels).
True MPPT Regs are expensive and in 90 % of camping use don't add all that much charging power (the theoretical figure is up to 30% BUT you won't see anything like that outside the lab).

MPPT (under about 1,000 watt systems) is the ducks guts if you have high voltage panels (32 volts or more) or don't track the sun like roof installs on houses/vans etc.

PWM is fine if you only use 12 volt panels (18 to 20 volts or so) in parallel and track the sun a couple of times

DC DC Charging, expensive but has its place, note that it will not have much effect on your solar (just saves you having an external Reg) and as you are getting sufficient performance already is not necessary. Certainly a consideration if you want to upgrade or need to buy an MPPT.

From Victron
PWM

The PWM charge controller is a good low cost solution for small systems only, when solar cell temperature is moderate to high (between 45°C and 75°C).

MPPT

To fully exploit the potential of the MPPT controller, the array voltage should be substantially higher than the battery voltage. The MPPT controller is the solution of choice for higher power systems (because of the lowest overall system cost due to smaller cable cross sectional areas). The MPPT controller will also harvest substantially more power when the solar cell temperature is low (below 45°C), or very high (above 75°C), or when irradiance is very low.

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Thanks for that, it's great help. I've already fitted a red Anderson plug from the auxiliary battery under the bonnet to the bull bar, for a future solar panel connection. As for the panel, I happen to have a good price deal on a single 300w Mono unit, but I could go smaller if too big. Both auxiliary batteries can be joined via an Anderson plug. It's not a "kit", so I'll be buying cables, connections, and regulator separately. I was thinking of getting a Redarc regulator. They have a couple already fitted with Anderson plugs, but I will look at the Victron units, as you've suggested.

Redarc will be just as good as Victron I reckon, prob cheaper (and aussie owned, Victron is Dutch or something)
I've never used one of their Regs is all but all their other stuff is extremely reliable.