Electricians: will this solar panel work with my charger?

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Arno:
So I am looking forward to providing EmComm to a mountain hiking area (TERT.org) and would like to use an existing solar panel to charge the 1400 and 2100 mAh NiMH batteries of my HT (Yaesu FT-60).

The rapid charger I intend to use is the EMS-57-83 by Batteries America.
Input to the charger is 15.8V @ 960mA.

My solar panel has these data:
Max power 3.2W
V at max pwr: 18.8V
Current at max pwr: 170mA

Measuring a bit, I found a lot less current:
putting the panel (in sun) directly against the battery, I read only 20mA.

Connecting the panel with the charger and having a battery in the charger, I get even less current, and the red LED (signaling charging) pulses. FYI: when that charger normally goes into trickle charge, the LED goes solid green.

Will this panel be able to charge one of my batteries during a long, sunny day without damage to battery or charger?
Should I connect it directly with the battery, or should I go through the charger?
Is it likely to fully charge those batteries or only partially (for the 2100mAh one)?

Thank you for your expert advice!

73,
Arno

Dale Hunt:
Quote from: KG7BJM


...The rapid charger I intend to use is the EMS-57-83 by Batteries America.
Input to the charger is 15.8V @ 960mA.

My solar panel has these data:
V at max pwr: 18.8V
Current at max pwr: 170mA





So, even if the voltages were in the acceptable range, the solar panel only puts
out 170mA max, while the charger requires 960mA to operate.

I'd say that your solar panel doesn't have enough current capacity to operate
the charger.


That's not to say that the solar panel couldn't be used, but it doesn't provide enough
current to fast charge the battery.  For this to work, you'll need NOT to use fast-charge
mode.  (If it tries to use fast-charge mode it probably won't just charge at lower current:
the voltage will drop too low to run the charger properly, and it may give an error indication
saying it thinks the battery is defective.)


Just looking at the current capabilities of the batteries, the 2100mA battery would have
to charge for a minimum of ( 2100 mA-h / 170mA )  >12 hours to fully charge the battery
from empty.  (And typically an extra couple of hours, since charging isn't 100% efficient.)

To fast charge the batteries requires a solar panel with a rated current of at least 1 amp,
or (since most will have a maximum voltage of 16 - 18V) something close to 20 watts.

Mark Brueggemann:
WB6BYU addressed the source side of the question but there's an issue with the load side here:

Quote

putting the panel (in sun) directly against the battery, I read only 20mA.

How were you connecting the panel to the battery?  Was it direct to the radio side + and - contacts or somewhere else?  That battery will present a low Z load to a panel and you should get pretty close to rated panel current in full sun.  Since you're not, then something is up with the panel or how you've connected it.

Per BYU's response above it would take a good 12 hours of full noon sun to charge a depleted battery from dead, which translates to probably 2-3 sunny days total depending on your insolation.  If that's a not acceptable your only option is using more panels or only having whatever power your one panel will provide any given day.


Mark K5LXP
Albuquerque, NM

Ed Gallup:

  think of it this way,  you're trying to operate a 15Watt charger with a 3Watt solar panel.  That's somewhat akin to trying to supply a fully operational fire truck pump with your garden hose.

Ed   K7AAT

Arno:
Thanks all for telling me so politely that my idea cannot work. I understand.

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