Ask Bill

Welcome to Ask Bill! If you have a question about our products or need some help and guidance with an off-grid power or lighting project please use our contact form to ask Bill.

You may also find answers to your questions in the numerous Help and Info articles available via this page.


Customer question (received via email 17th June 2020):

Hi, Please can you advise me if you have a solar charger suitable for charging the battery on my tipper trailer, it is left in an open barn with no electricity so would need to be waterproof and also would need to be left unattended for long periods. Many thanks

Willgen Reply (Email from Bill 17th June 2020):

Hi Nick,

Many thanks for getting in touch.

As the battery may be quite depleted after use the Optimate 20 would be well suited to your requirements.

If you need to recharge the battery quickly due to regular use of the tipper battery you may want to use a larger...

Customer question (received via email 13th June 2020):

Which solar panel would be suitable to charge an electric ignition on a sit on lawn mower please?


Willgen Reply (Email from Bill 15th June 2020):

Hi Kim,

Many thanks for getting in touch.

If you can get the solar panel in a good position (outdoors, South facing, un-shaded) an Optimate 10 will be ideal for a lawn tractor battery. If the solar panel is less than perfect go for a larger Optimate 20. This will ensure that the battery is kept topped up when the tractor is not in use and the battery will always be fully charged ready to start the engine when...

Customer question (received via email 12th June 2020):

Good afternoon.  I have a Land Rover Defender with a twin battery set-up (main and leisure).  Which trickle charger would you recommend please?  Thank you, Nick.

Willgen Reply (Email from Bill 15th June 2020):

Hi Nick,

Many thanks for getting in touch.

Assuming that you want to charge both batteries I would either go for one solar charger and swap it between batteries, two separate solar chargers with one solar charger dedicated to each battery or for a single larger solar panel wired back to a dual battery charge controller.

Single Solar Charger

I highly...

Customer question (received via email 30th May 2020):

My Motorhome has 2 x 110ah leisure batteries fitted in parallel and a 90ah vehicle battery. What would be a suitable solar trickle charger to keep these topped up during storage with no drain from the leisure batteries and an alarm/tracker/radio drain from the vehicle battery - I intend to alternate the charging regime between leisure and vehicle during storage. I can mount the panel in unshaded south facing location outside of the vehicle. 


Willgen Reply (Email from Bill 1st June 2020):

Hi Paul,

Many thanks for getting in touch.

For the situation you describe I...

Posted by in Ask Bill, Boats and Campers on Jun 01, 2020 .

Customer question (received via email 10th May 2020):

Hi. Looking for a small solar panel to maintain a charge on a 110Ah rib battery. Need to mount on the stern A frame as boat will have cover on it when not in use, may need 6m of cable or so. The panel will be out in the elements all year. Smallest would be best and I'm guessing I may have to make some sort of backing/mounting plate. Could you let me know what my best options are please.

Kind regards

Willgen Reply (Email from Bill 11th May 2020):

Hi Derek,

Many thanks for getting in touch.

To maintain a 110Ah battery throughout the year (ie through winter as...

Posted by in Ask Bill, Solar Lights and Chargers on May 20, 2020 .

Customer question (received via email 10th May 2020):

I am looking for advice on what type, size and cost I need to install a solar system to keep a car battery topped up when the car is not in use. The panel would have to be left outside as the car lives under a cover when the power would be required.

Any advice would be helpful


Willgen Reply (Email from Bill 10th May 2020):

Hi Jim,

Many thanks for getting in touch.

You need to be looking at the Optimate range of solar chargers for your car.

The size of solar charger required depends on the drain on the battery when the car is parked (i.e alarm etc) and the...

Customer question (received via email 11th May 2020):

Please advise best trickle charger to keep my motor home vehicle 90ah battery topped up while in longterm storage. Thanks Gerry

Willgen Reply (Email from Bill 11th May 2020):

Hi Gerry,

Many thanks for getting in touch.

The size of solar charger you require depends on the parasitic load on your battery (i.e drains on the battery when the motor home is parked up - alarm etc) and how good a position you can get your solar panel in.

If the parasitic load is just an alarm, and you can get the solar panel outside, in an un-shaded South facing position I would suggest an...

Customer question (received via email 27th April 2020):


I am looking to purchase the OptiMate 20W Solar Charger and the OptiMate OBDII to SAE Adapter for a smart fortwo.  I would like to place the solar charger on the dashboard and connect via the obd port.  Car is a 2013 plate.  If all this is OK I will order as soon as I have your reply, also how soon is delivery Thanks Arthur

Willgen Reply (Email from Bill 27th April 2020):

Hi Arthur,

Many thanks for getting in touch.

The solution you suggest will work absolutely fine to keep your car battery charged. You may want to consider purchasing suction cups as well so the...

Willgen, Church Farm, Wartnaby, Melton Mowbray, Leicestershire, LE14 3HU
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