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Q & A

Trickle Charging Batteries

I read in your Q & A section that someone has 5 x 110 AH and 1 X 50 AH batteries which they want to leave on trickle charge unattended over the winter months. It was suggested that a 60 W panel would be ideal. I have a 150 W panel, can I use this and what sort of controller woulkd I need. I also have a 1 x 110 AH bow- thruster battery which I would like to keep charged. Thanks for any advice.

Asked by: Alan Denney  | 3.32pm, Monday 24 September


WW says:

A good split-charge solar charger can be used, though normally there isn't a three- way output, usually just dual output- however, you could possibly add the bow thruster battery to the engine starter circuit- though the long length of charging cable might cause such voltage drop that it wouldn't charge enough.
A large solar panel is fine- excess charge is dumped often to a bulb load, so the batteries shouldn't overcharge!
For ease of fitting, a cheap separate 10W panel might be the cheapest way to keep the bow thruster battery topped up. Mounted close to the battery (on top of a cratch, on the forepeak locker lid, etc.) a simple 10W panel would only need blocking diodes and should keep it well maintained.

Mark Langley  | 11.50PM, Monday 24 September

I agree with Mark that a separate panel will be needed for the bow thruster battery. Often the charging of the bow battery is combined with the starter battery when the engine is running, either with a second split charge relay or a diode; neither of these systems will work with the solar panels. A 10W panel (usually with the blocking diode built in) can be directly connected to you bow battery, but do not use crocodile clips and fit an inline fuse (5A should provide ample protection) close to the positive battery connection.

Rupert Smedley  | 9.26AM, Tuesday 25 September

Most of the solar panel controllers are not made in the UK: for instance, the Victron Duo controller is made in China, and identical ones can be found for about 30% of the price on Ebay (I know, as I purchased one) and they work fine.
There are some US and UK branded controllers, but most, like many electronic devices, are actually produced abroad, often in China.
Generally, they work well- and tend to fail "safe". "you get what you pay for" isn't always the right mantra!

Mark Langley  | 11.18AM, Tuesday 25 September

The solar panels themselves are also made in the far east.

Rupert Smedley  | 6.22PM, Tuesday 25 September


Readers say:

Hello Mark, Thank you very much for your answer, I will certainly give your suggestions a go so watch this this space for results. Thanks again, Alan

Alan Denney  | 12.48AM, Tuesday 25 September

Hello Rupert, do you have any particular suggestions as to which make of controller I should consider? Must be reliable and made in UK if possible. Many thanks for your reply, Alan

Alan Denney  | 11.14AM, Tuesday 25 September

Thanks again Rupert, Alan

Alan Denney  | 12.16AM, Wednesday 26 September

I just use the inexpensive so called 'brief case' solar panels rated at 12 watts to keep my batteries topped up. They only need blocking diodes which are already fitted. I hang the panels up inside the boat against a window which seems to provide enough light. They are sufficiently inexpensive to allow the luxury of one panel per battery bank.

Roy Harris  | 2.59PM, Sunday 3 February

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