Solar panel battery charger

[rar110]

I’m looking at buying a small solar panel, probably about 10w, to keep the 110’s cranking battery and Tvan camper batteries topped up.

There are lots of options on eBay.

Does anyone have a recommendation on specs/features, a model or supplier?

Thanks.

[Dorian]

Hi,
If it's for float voltage maintenance, You only want about 5 watts per battery, So if they are not connected then get 2 x 5 watts, but any 12v panel will do
Remember to lift the 0Vdc (earth / ground) on any dual battery isolator (VSR) that you have, so they are not drawing any current and then connect the positives together.
On my boat, I've got a dual pole switch, one pole lifts the earth to the 2 x VSRs and the other pole connects the two batteries together.

Cheers Glen

[Red90]

IME you need to be at least 15 Watts with a decent panel to keep up. 25 is better. You want to make sure it has a charge controller of some sort. This prevents overcharge and overnight discharge.

[Slunnie]

IME you need to be at least 15 Watts with a decent panel to keep up. 25 is better. You want to make sure it has a charge controller of some sort. This prevents overcharge and overnight discharge.

Solar panels and the controller discharge batteries?

[DeanoH]

Solar panels and the controller discharge batteries?

Used to be a problem once upon a time, especially for those who think it's a good idea to connect a solar panel directly to the battery with no controller. Some solar panels come with a series connected forward biased diode in the connector box on the back of the panel. This solves any potential 'nightime discharge' issues and protects the panel from inadvertent reverse connection. :)

An issue with constant float 'set and forget' connection is that float voltage is usually set at 13.5 - 13.8 volts depending on the battery/controller which is above the gassing voltage for many lead acid batterys. Ultimately this can wear the battery out as electrolyte may be slowly depleted, re-combination type battery or not. Leaving a battery on constant float can also aid sulphation (where insoluble lead sulphate forms on the plates reducing battery efficiency).

To overcome this some quality controller manufacturers eg. Victron can have a maintenance mode in their charging profile which drops the float voltage from say 13.5 V to 13.2 V which is below the electrolyte gassing voltage so holds the battery fully charged without gassing. To prevent sulphation and electrolyte stratification in a flooded cell (where electrolyte becomes layered with different levels of specific gravity) every so often the charger goes into charge mode and stirs things up. This is probably the 'gold standard' and can be relatively expensive to set up as these controllers aren't cheap.

Another potential hazard of the 'set and forget' maintenance mode is that when cheap controllers fail it's often the output voltage regulation that fails leading to overcharging and eventual destruction of the battery(s). It may be cheaper and more reliable in the long run to buy a 240 volt battery maintenance charger instead.

Deano :)

[Gav 110]

Used to be a problem once upon a time, especially for those who think it's a good idea to connect a solar panel directly to the battery with no controller. Some solar panels come with a series connected forward biased diode in the connector box on the back of the panel. This solves any potential 'nightime discharge' issues and protects the panel from inadvertent reverse connection. :)

An issue with constant float 'set and forget' connection is that float voltage is usually set at 13.5 - 13.8 volts depending on the battery/controller which is above the gassing voltage for many lead acid batterys. Ultimately this can wear the battery out as electrolyte may be slowly depleted, re-combination type battery or not. Leaving a battery on constant float can also aid sulphation (where insoluble lead sulphate forms on the plates reducing battery efficiency).

To overcome this some quality controller manufacturers eg. Victron can have a maintenance mode in their charging profile which drops the float voltage from say 13.5 V to 13.2 V which is below the electrolyte gassing voltage so holds the battery fully charged without gassing. To prevent sulphation and electrolyte stratification in a flooded cell (where electrolyte becomes layered with different levels of specific gravity) every so often the charger goes into charge mode and stirs things up. This is probably the 'gold standard' and can be relatively expensive to set up as these controllers aren't cheap.

Another potential hazard of the 'set and forget' maintenance mode is that when cheap controllers fail it's often the output voltage regulation that fails leading to overcharging and eventual destruction of the battery(s). It may be cheaper and more reliable in the long run to buy a 240 volt battery maintenance charger instead.

Deano :)

Or safer to buy a good quality solar regulator such as a victron
If you have extension leads running out to your vehicle (especially exposed to the weather) you have a potential hazard
[emoji1531][emoji1531]

[Don 130]

I recently fitted a solar panel to a horse float to maintain the breakaway braking system battery which is 12volts, but only 5 watts. I consulted the local auto electrician about the panel capacity. He suggested 40watts for that job.

40W 12V Solar Panel Kit Caravan Camping Power Battery Charging | eBay (https://www.ebay.com.au/itm/323583599374)

Edit. I'm pretty sure the regulator is NOT an mppt type, but it works.

Don.

[Tombie]

I’ve maintained the batteries on my Catamaran outboards using 2x 10w panels (1 for each battery) - direct clip connection and no issues in 7 years.

[Red90]

Solar panels and the controller discharge batteries?

A plain panel will reverse feed current when no light is on it. Most panels have diodes built in to prevent this. However...when you are buying cheap, small panels, this is not guaranteed.

[rar110]

Thanks for the replies everyone.

I’ve ended up just buying a Ctek quick connector with LED indicator for the 110’s battery. The voltage only gets low after about a month or so. I’ll keep an eye on the indicator and put the Ctek on it as required.

I probably should just rotate the Ctek around all the vehicles (incl camper) every month or so. All will now have quick connectors.