Sailboat Diaries: Minimum Amperage For Trickle Charge?

A trickle charge is 2 amps...I use a similar setup but with a 20 watt panel....it'll charge a car battery up in about 4 or 5 days...still it should work over time....must be wired wrong, or you have a defective unit...LED's will light with almost nothing....

https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=solar+panel+trickle+charger+12v+20+watts&rh=i%3Aaps%2Ck%3Asolar+panel+trickle+charger+12v+20+watts

Thanks. I checked the polarity and it seems correct. I think it is broken.

I figured that even though it is less than 0.5 A, it should be enough to trickle charge as long as the voltage is higher than the battery. The panel has a diode to prevent the reverse.

This is like the one I have...

Thanks for your thoughts...

Ah of the battery is 109. I hope to actually recharge the battery, not just maintain a charge. I expect the battery could get to around 50%, as this would provide me with roughly two days of power considering appliances draws and a ballpark usage estimate. Although, it would be ideal to be able to us the panel while sailing as well to extend travel range and cycle life.

The charge controller has an overvoltage of 14 V (±0.5 V) and undervoltage of 11 V (± 0.3 V). Notably, when the panel was supplying up to 15+ V, the overvoltage LED indicator did not light up. (Other LEDs indicated charging and undervoltage.) It does not appear to be an MPPT type. I always try to remember to connect the battery side first. There does not appear to be a short or burn on the regulator board and there is no diode in the controller.

On a good day, the panel could see 10 hours of useful sun On a June or July day. The boat will be left on a mooring in a large lake where the it will be a north wind about 60% of the time, south wind 30% of the time. So on a day with a south wind the boat will point right into the sun.

I will investigate point #5 and #7 this evening...

I think you are confusing standard auto batteries with marine deep cycle batteries....

..."a deep cycle battery can withstand several hundred total discharge/recharge cycles, while a car battery is not designed to be totally discharged."...

https://www.solar-electric.com/learning-center/batteries-and-charging/deep-cycle-battery-faq.html

There is no minimum amperage for a trickle charger. That is why it is called a trickle charger. However, the voltage of the PV Panel should be above that of the battery, whatever be the type.

if the voltage is much higher than the Panel, as it sometimes happen, you need a charge controller, which will reduce the voltage suitably. If it is 18 or even 15 no worry with trickle charging. The battery will not GE overcharged.

any appliance, be it a motor, or any device that has an initial torque cannot be started with a PV panel, even if it is of a higher wattage. A battery, which supplies a higher push for starting the motor, is a must, as I learnt, bitterly. It needs four to five times the wattage.

if the battery is not getting charged satisfactorily, the wattage developed must have been much lower, because of poor exposure to sun. The problem would get solved, if the panel is placed on the top of whatever structure your boat has, and see that full sun impinges on it.

Good luck.

Impressing any voltage higher than about 13.5V for any length of time once a 12V battery is fully charged will eventually cook it, this is why trickle chargers are limited to that value. There are solar panels available that have a lesser number of series connected cells - and a resulting lower voltage - that can be used to directly charge a battery, but a standard 36 cell pv should never be used without a regulator for battery charging.

There are many instances of electric motors being driven directly from solar panels, The advent of MPPT controllers has made this a common practice.

I suggest you investigate that further.

I hear you regarding the LiFePo4 battery, but there doesn't seem to be an affordable solution below ~$350, compared to the lead acid which was $100. Its just not in the boat budget right now.

The idea is to have a portable solar solution that I can deploy as needed, either when the boat is left behind or when we are out on the beat for a full day or so. In either case 50% discharge would probably be unlikely, and never for very long. As is, its a new battery that has been left on a tender since purchase.

In the end, I decidedly to massively upgrade the solar system to a 50 W foldable panel and different charge controller. It's a little big, but at least it is stowable.

Good Move! The 10000W building system I know [fixed due south at optimum angle to vertical, 98% inverter efficiency to 415V 3 phase] delivers 950Wh/annum for each watt of capacity. For 50W panel @14V (100% efficient), that is 0.75A mean during daylight hours - the peak summer months are about 1.5 times that mean, but worst winter month is only 0.25 of mean, say 0.2 Amp [only 0.1A mean over 24 hours, latitude 52 degrees here, Gotham City unknown]. Your mooring wind swing will reduce output significantly - prevailing wind may suggest seasonal change of panel position.

Watch out for a controller that loads the battery - will those pretty LEDs drain the battery at night?

A 50W panel is only about 3 amps max, this is well within continuous overcharge current for sealed 100 Ah LA batteries, as I commented before, a regulator may be unnecessary.

Your solar panel is maxing out at 5 watts. I suspect after voltage reductions for the diodes and any line losses, there might not be enough left to power the charge controller and change the batteries.

The smallest solar panel the charge controller seems to be paired with on the internet (for whatever that is worth) appears to be a 15 watt panel.

For a 12V, 5W panel, 1/3 amp x 12V = 4W is about what you'd expect, whatever the controller is rated at. Others have commented whether that's enough to trickle charge your battery.

With such a small panel, you do not need a regulator, just connect the panel to the battery, to make-up self-discharge, at least until you sort out what panel/regulator you need.

You could feed the regulator from a car battery in series with 3 cell D size alkaline primary cells to see what it does.

Thanks. We are still on the hard for the next two weeks, so I still have a normal battery tender available. This is one of the last projects to finish up. Without this, I will need to take the battery off the boat to charge each time I leave it for a week or so.

Will be launched by/for Memorial day.

I've used different panels in the 1W to 50W range and have steered away from the smallest panels for this very reason. (15W or better is ..better)

I found some excellent monocrystaline flexible panels on ebay for a song.

Flexible, light, durable, weather proof and bonded to thin aluminum instead of stiff heavy glass. Perfect for boating.

No, however it will take as an absolute minimum [the amp-hour capacity of the battery] divided by [<...1/3 of an amp...>] of time to charge-up the battery from flat, however as the voltage on the terminals begins to rise as the battery charges, the current will start to drop, so it is going to end up taking somewhat longer than that.

From the plot so far it seems as though the <...charge controller...> is malfunctioning. One might suggest beg/steal/borrow another one to prove that suspicion or otherwise, then, if proven to be true, look for a replacement.