What wattage for a solar trickle charger?

[Breezin]

My bike only gets out once a week max these days, due to lockdown/winter etc., and yesterday the battery light was staying on longer than I'd like. So thinking of a trickle charger - solar, as the shed has no power.

Looking at the options, they range from 3w to 10 or so. Any clue as to what it needs, or what might be too much?

[husoi]

I'm trying to equip my new trailer (see my other post) with a solar panel to charge phone, camera, sat-nav, etc.

After some investigation I realise that not only the suppliers of solar kits are anything but reliable they lie as much as an MP.

Some facts:

Sun energy at sea level on a bright day at noon will give something around 800W / m2

The best solar panels currently can convert around 20 to 23% energy which will give you no more than 184W . m2.

The best way for you to measure how much power you will get from a given solar panel is to multiply the max voltage by the current.

(W = V x I Power is the voltage times the current)

Depending on the battery condition you will need around 1A to recover a battery with low voltage (around 8 to 10V) for a few hours.

Also, it depends on your location. Further north the variation is greater both between summer / winter but also further north you are less sunlight you will get.

A trickle charger usually will have a top current of 0.8A (800mA) to 1A as this will mimic the current of the alternator of the bike.

Ireland (by your location) will have short days reducing substantially the output of a solar panel.

I would assume you may get around 250W / m2 average.

Thinking that you will need it more in the winter as it is when the bike will probably be stationary for longer you are looking at 2Kw panels to make sure you have the battery fully charged at all times.

With the 2Kw panels you would need to get a controller to make sure it stops charging once the battery is full.

[dynax]

I'm trying to equip my new trailer (see my other post) with a solar panel to charge phone, camera, sat-nav, etc.

After some investigation I realise that not only the suppliers of solar kits are anything but reliable they lie as much as an MP.

Some facts:

Sun energy at sea level on a bright day at noon will give something around 800W / m2

The best solar panels currently can convert around 20 to 23% energy which will give you no more than 184W . m2.

The best way for you to measure how much power you will get from a given solar panel is to multiply the max voltage by the current.

(W = V x I Power is the voltage times the current)

Depending on the battery condition you will need around 1A to recover a battery with low voltage (around 8 to 10V) for a few hours.

Also, it depends on your location. Further north the variation is greater both between summer / winter but also further north you are less sunlight you will get.

A trickle charger usually will have a top current of 0.8A (800mA) to 1A as this will mimic the current of the alternator of the bike.

Ireland (by your location) will have short days reducing substantially the output of a solar panel.

I would assume you may get around 250W / m2 average.

Thinking that you will need it more in the winter as it is when the bike will probably be stationary for longer you are looking at 2Kw panels to make sure you have the battery fully charged at all times.

With the 2Kw panels you would need to get a controller to make sure it stops charging once the battery is full.

 

In short it would be more practical to install a power supply to the shed

use an arctic cable extension lead as a temporary solution, you can fit external plugs and sockets to make a simple plug and play solution

[Mississippi Bullfrog]

From past experience, chuck a 10W solar panel on it and providing the battery is healthy it will keep it charged sufficiently. They don't put out enough juice to overdo the battery.

[dynax]

If you go solar option use a controller i have a couple of solar chargers and on a bright day in full sun can chuck out in excess of 25v

[onesea]

Once a week should be enough to keep battery fit IMHO how old is the battery?

Unless you have alarm or parasitic draw. have you considered just replacing battery?

https://batteryclerk.co.uk/products/royal-enfield-bullet-electra-efi-500cc-motorcycle-replacement-battery-2011-2014?variant=31755284152363&utm_source=googleshopping&utm_medium=cse&gclid=Cj0KCQjw2or8BRCNARIsAC_ppyZPKTdZbQ6XBhnRuwWRAYEsn6zsDr_3D_B7wQ85qcipxZ01jYilK_IaAvtJEALw_wcB

[husoi]

One thing you will get with a more powerful solar panel set is that by adding a battery you can store the unused power to lighting in the shed/garage with no running cost

[Copycat73]

or you could just take off the battery and charge it in the house.

[Breezin]

Thanks for those helpful responses - lots to think about there!

Good point about higher output to compensate for lack of sun. Might go that route.

Taking the battery out is a pain on the Interceptor. Not something I want to do on a regular basis. Longer term, will wire the shed for power so I can also use a shed heater. That's bit of a project though!

[husoi]

or you could just take off the battery and charge it in the house.

 

Where's the fun in that??

[dynax]

If you get a decent sized panel you could use a leisure battery to power lights and an inverter so you could use a low powered tube heater or oiled filled radiator, but having a seperate battery would mean you could make up some jump leads with quick connectors to maintain the bike battery

[Mississippi Bullfrog]

I guess you need to make a decision between a proper hig spec solar panel that would provide much more power than just needed to trickle charge a battery, or just get a cheap one that with winter light is just going to keep the battery topped up. I've only ever done the latter - the solar panel is currently on our daughter's car as she's working from home at the moment. The car hasn't moved since March and the battery is over 20 years old but it fires up when I need to move it.

[Breezin]

Cheapo option for me -- habit of a lifetime and not going to change now!

If I can get away with the quick and dirty solar panel just for trickle purposes, I'll do that.

Bigger panels might be a bit of a hurdle with the neighbours -- some are a bit precious about my having a shed in front of the house as it is, so I'm keeping things on the down-low as far as possible.

PS: Battery is about 15 months old. Only accessory is Oxford grip heaters (and the occasional phone charge), but very rarely on of late...

[Stu]

Seen as though no one has picked up on it or questioned it what do you mean your battery light stayed on longer than you like?

Do you mean the one on the bike on the dash?

[Breezin]

Seen as though no one has picked up on it or questioned it what do you mean your battery light stayed on longer than you like?

Do you mean the one on the bike on the dash?

 

Yep... red battery light just stayed on for a few seconds after starting the engine the other day, when I hadn't noticed that before with the engine running. No other draw at the time.

No problem turning the starter, but if I'm guessing it was maybe at the limit.

[Stu]

Seen as though no one has picked up on it or questioned it what do you mean your battery light stayed on longer than you like?

Do you mean the one on the bike on the dash?

 

Yep... red battery light just stayed on for a few seconds after starting the engine the other day, when I hadn't noticed that before with the engine running. No other draw at the time.

No problem turning the starter, but if I'm guessing it was maybe at the limit.

 

The red battery light is purely to tell you if the bike is charging or not and nothing actually to do with the battery as such.

I would just double check to see if the bike is charging fine and if so don't worry about the charger if you're using the bike at least once a week

[Breezin]

Seen as though no one has picked up on it or questioned it what do you mean your battery light stayed on longer than you like?

Do you mean the one on the bike on the dash?

 

Yep... red battery light just stayed on for a few seconds after starting the engine the other day, when I hadn't noticed that before with the engine running. No other draw at the time.

No problem turning the starter, but if I'm guessing it was maybe at the limit.

 

The red battery light is purely to tell you if the bike is charging or not and nothing actually to do with the battery as such.

I would just double check to see if the bike is charging fine and if so don't worry about the charger if you're using the bike at least once a week

 

Right... stop worrying! I'll go with that solution for now!

[Stu]

Yep... red battery light just stayed on for a few seconds after starting the engine the other day, when I hadn't noticed that before with the engine running. No other draw at the time.

No problem turning the starter, but if I'm guessing it was maybe at the limit.

 

The red battery light is purely to tell you if the bike is charging or not and nothing actually to do with the battery as such.

I would just double check to see if the bike is charging fine and if so don't worry about the charger if you're using the bike at least once a week

 

Right... stop worrying! I'll go with that solution for now!

 

If anything just get a multimeter across the battery terminals to make sure you have plenty of charge

[onesea]

PS: Battery is about 15 months old. Only accessory is Oxford grip heaters (and the occasional phone charge), but very rarely on of late...

The change charge is that a reducer to 5v for usb?

Does it isolate when bike turned off? Even with nothing plugged in they can take a little current.

[Breezin]

The red battery light is purely to tell you if the bike is charging or not and nothing actually to do with the battery as such.

I would just double check to see if the bike is charging fine and if so don't worry about the charger if you're using the bike at least once a week

 

Right... stop worrying! I'll go with that solution for now!

 

If anything just get a multimeter across the battery terminals to make sure you have plenty of charge

You're ahead of me... can't find my old one, last used maybe 10-15 years ago, and buying one today!

[husoi]

Several years ago I bought a wee solar cell trickle charger from Maplin.

I think was something 30cm X 10cm but only give around 5W on sunny days. But for a tenner I was happy.

As I said earlier, only good in the summer with plenty sunshine(ish) in winter months is worthless.

But if the battery is fully charged then what you maybe need is an isolator switch to the battery cable so it doesn't get drained and the solar cell will keep it charged.

[Breezin]

PS: Battery is about 15 months old. Only accessory is Oxford grip heaters (and the occasional phone charge), but very rarely on of late...

The change charge is that a reducer to 5v for usb?

Does it isolate when bike turned off? Even with nothing plugged in they can take a little current.

 

Yes, 3 amp or so usb charger. I didn't realise it would draw when not in use! I can disconnect at the sae connector. I assume that would do the trick?

I'd put it on the switched circuit but it's been great to have when camping and charging the power bank. Usually, camping goes with longish runs, so the charge should be ok.

[husoi]

You can always use one of them

https://www.amazon.com/LotFancy-Battery-Switch-Disconnect-Isolator/dp/B082W24S4F/ref=sr_1_7?dchild=1&keywords=motorcycle+battery+disconnect+switch&qid=1602516707&sr=8-7

[onesea]

Yes, 3 amp or so usb charger. I didn't realise it would draw when not in use! I can disconnect at the sae connector. I assume that would do the trick?

As I understand the draw is normally only minimal when it's not charging.

Then I am paranoid about flat batteries, when bike is off everything should be off...