In article , "Dennis Pogson" wrote:
John wrote:
I purchased a small flexible solar panel from Silicon Solar Inc.
Their web site advises that the panel is "perfectly suited as a 12V
battery charging solar solution." Just what I need for trickling the
12 volt starting battery for my dinghy. The solar panel produces 7.2v
100 mA.



A friend, who is an engineer, informed me that I am wasting my time.
He says I need 12Volts from the solar panel to charge a 12 volt
battery. Thus the
7.2V will not do it.



Who's right, the manufacturer or my friend?

Must be the pocket version. You need something around 3 foot by 5 foot,
shoving out 13 volts min.@ 1AH.

Dennis

1 amp is certainly not trickel charging. That may even boil the battery too
much. A Harbor Freight 120 ma. 3 inch by 12 inch panel would work, but is this
salt water ??

greg

In article , wrote:
On Mon, 21 Apr 2008 12:58:24 GMT, (GregS)
wrote:

In article , "Dennis Pogson"
wrote:
John wrote:
I purchased a small flexible solar panel from Silicon Solar Inc.
Their web site advises that the panel is "perfectly suited as a 12V
battery charging solar solution." Just what I need for trickling the
12 volt starting battery for my dinghy. The solar panel produces 7.2v
100 mA.



A friend, who is an engineer, informed me that I am wasting my time.
He says I need 12Volts from the solar panel to charge a 12 volt
battery. Thus the
7.2V will not do it.



Who's right, the manufacturer or my friend?

Must be the pocket version. You need something around 3 foot by 5 foot,
shoving out 13 volts min.@ 1AH.

Dennis

1 amp is certainly not trickel charging. That may even boil the battery too
much. A Harbor Freight 120 ma. 3 inch by 12 inch panel would work, but is this
salt water ??

greg

True trickle charging is only to maintain the battery at full charge
by compensating for the battery's own rate of self-discharge. A true
trickle charge rate will not recharge a battery.

A solar panel for charging AND maintaining a typical marine battery
will need substantially more available power, and a smart regulator.
There is no $100 "magic pill" for this job. The 1 AH panel Dennis
mentions will hardly ever, if at all, put out it's full rated output
for more than a few minutes under perfect conditions. Most solar
panels are rated VERY optimistcally. In any case, you need a
regulator.

I call trickel charging on the order of 5-10 ma. 100 ma. will cause bubbling of
cells, and is absolutely the max I would use without a smart
controller. It would take at least 8 hours to replenish a 5 second 600
amp starting current @ 100ma. Plus some.

greg