ktmrfs wrote:
NinerBikes wrote:
Salvo wrote:
You shouldn't have that large of a voltage drop. Did you actually measure 14.40V at the charge controller and then 14.15V at the battery?
How many panels do you have?
Sal
Sal, one basic 120w kit as shown here by Solar Blvd.
Solar Blvd 120W portable folding solar panel kit.
It comes with connectors, and some, what I would call "lampcord" type wire with SAE connectors. Add in all the connectors, the RC controller type charger meter I installed with a shunt of sorts in line, and the battery connector clamps, and yes, with a digital voltmeter, that was the voltage loss. I've no idea truly what gauge wire they are running in the lampcord, but being Chinesium, it is probably a cost cutting gesture, you can see pretty much the same $8.00 kit available at Harbor Freight. One end is a cigarette female with SAE connector, one end is an electrical eyelet connector, then 5 meters with SAE connectors on each end, then a battery and a power source connector on the Charge Controller. Not very heavy gauge wire, even by 14.4v x 6.5 Amp standards. I substituted a 6 foot section of some 10 gauge 2 wire 17 wire strand romex type stuff from a scrap of an electrician buddy of mine, and tested the voltage drop with that, and it wasn't but a 0.1v to 0.0v drop on the volt meter, it fluctuated. So 10 gauge at 6 feet, the loss was minimal, but the stuff in the kit that ties in after the charge controller does it's step down at the back of the panel with the zip cord lamp cord stuff is bad juju for battery charging.
I have the 100w kit, Best I can determine the extension cable that comes with the kit is #14 possibly #16. a 15' section of #16 wire with 7A will have a resistance of about 0.06ohms for a voltage drop of about 0.4V. If it is #14, resistance would be about 0.04 ohms and a voltage drop of about 0.25V
Since about 0.25V is what your seeing, it may be #14.
First thing I did was remove this cord and put on a 10' section of SJ #10/3 using my trick mentioned above.
Yup, got my feet wet in solar, got dicked by buying a kit thinking it's "good enough" and with you are barely in triple digits with watts and power, at 21 volts, every little bit, and little trick helps in making it all add up in getting those batteries truly topped off at 100%, daily, if possible. I will get there, bit by bit. Pretty sure I will go 10 gauge, maybe 8, since I have read various theories... one guy says you need 3% output by your panels of your battery ampere hours, another says a watt of solar panel per ampere hour. 6.67 rated amps is 3% of 225 amp hours on a Trojan 6v t105 pair of batteries. It's almost 4.5% if I get the Trojan T1275 for free.
Slowly, surely, I will get 'er done with an efficient wiring and programable of sorts PWM charge controller. Copper is cheap to control losses.
