Solar panel power for motorcycle battery chargers?


Active Member

Apologies if in the wrong thread. I am moving house and have a dedicated bike garage that I will dismantle and take with me. Currently I have power supplied to it via an exterior 13a wall outlet in order to power two trickle battery chargers/tenders (Optimate type thing which states max 900ma p/hr, usually 200ma for float charging) This will not be an option at the new place, so I was thinking about solar power, like motorhomes may use. Or a long extension cable from the kitchen window... haha.

My research leads me to believe that I need a solar panel, leisure battery and inverter (12v to 240v). Is this correct? As these are trickle chargers to 12v motorcycle batteries I think a small panel would be OK? Do I just connect the panel’s output to the battery and the battery to the inverter and plug in my devices? I see there are panels to 12v batteries available but I have two bikes and Optimate fly leads so I don’t have to remove seats and fairings. I see some panels ending in USB sockets but there is no battery tenders that have USB power into them, only standard 3 pin plugs.

Really trying to not spend a huge amount as moving isn’t cheap!

The products I have been looking at are:


It would be great if anyone has experience (who am I kidding, the people on here are superb 😎) and guidance on how these things fit together and advice on what would work.




Distinguished Member
Converting from 12V to 240V and back to 12V is very inefficient and will likely deplete the storage battery quite quickly. The inverter will pull power the whole time - plus the charger itself. If this adds up to about 0.5A, then the battery will probably last about 7-10 hours before it is discharged to a point the inverter will cut out.

A 25W solar cell will probably deliver an average of more like 8W - which is about 600mA @ 12V. Therefore, if your system is pulling about 500mA, your charging is only 100mA per hour, so it will not recharge the battery enough to last through the the dark hours.

I think you will need at least 100W of solar panels and a larger battery - 25Ah or so for both bikes. You may still occasionally need to top up the battery from a mains source.

Can you not get the Optimate solar system, as that uses the bike connections?


Active Member
Many thanks Noiseboy! Now why didn’t that show up in any searches 🥺 I am actually using an Oxford 900 with the old Opimate type cables, but a small job to change the fly leads... at least on one. As usual it will be a major job on the Italian one. A small inconvenience in that I will have to buy 2 though. I do love these forums!


Active Member
If it were me I would get a small panel -maybe 20w (Cost about £25) and a solar charge controller with dual battery outputs (cost about £10) and charge the batteries directly without the (better) optimate charger.

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