Posted by New Guy on May 16, 2015, 4:21 pm
I have a HF 45 W solar setup charging 3 35AH batteries and a 2000/4000
W inverter. I was hoping to power an air compressor which is rated for 14
amps. As it is now it won't. How can I beef up my setup to do so.? I am
new to PV and have trouble understanding electric talk. What do I need to
add ? And can someone point me to a link which might help me to understand
a little about electricals associated with PV.
Posted by Vaughn on May 16, 2015, 5:16 pm
On 5/16/2015 12:21 PM, New Guy wrote:
Where do I start?
First, your 45 watt HF solar setup is likely barely good for 20 watts of
actual charging in full sunlight. Assuming no load, it will barely be
enough to deal with the leakage current from those three batteries to
keep them topped off. Also, I would not trust the charging regulator
that comes with that set. If it under or overcharges your batteries, it
WILL ruin them over time.
Second, you are trying to run a nominal 1700-watt load from a nominal
2000 watt inverter. Even if you can believe ratings, that leaves
virtually no cushion for the unexpected. There are lots of reasons why
that might not work! The inverter may not be heavy enough to handle the
motor starting load, and/or the compressor motor may not like the
(likely square wave) waveform from the inverter.
Are your battery cables short? Are they heavy enough to handle the
starting load of that compressor, which will be at least 300 amps on the
Honestly, to do what you want to do with solar power you need to start
all over. You need far more and better solar panels with an appropriate
charge controller, you need a much better inverter, and likely you need
heavier batteries and cables.
Posted by New Guy on May 16, 2015, 7:38 pm
On Sat, 16 May 2015 13:16:00 -0400, Vaughn wrote:
I hadn't considered waveform factor.
Cables are 2 ga. and approx 12" ( from terminal to terminal ). The 2 ga.
cables to the inverter are about 24" to keep a little distance from the
Originally I purchased the above to get lights in my barn and a possble
powertool from time to time. I had 1 35ah battery which I bought at
Northern Tool. I guess I figured that more batteries meant more available
power. So I added a couple more of the same batteries.
I do intend to purchase better panels some day. I was just hoping to
get the most out of what I already had.
Posted by Jim Wilkins on May 18, 2015, 10:13 pm
What is your experience / evidence for that?
"Generally, gel and AGM batteries have about 20% less capacity, cost
about two times more, and have a shorter cycle life than comparable
flooded lead acid batteries."
I've had better luck desulfating and equalizing old flooded batteries,
as old as 2000 and 2002, than with 5 - 6 year old VRLAs.
Posted by clare on May 18, 2015, 10:53 pm
On Mon, 18 May 2015 18:13:16 -0400, "Jim Wilkins"
Much better go buy the biggest 6 volt batteries you can buy and
connect in series for your required voltage. I'd be going at least 24
volts for that kind of load to reduce the primary current required.
2 big sixes in series for 12 is a lot better than 2 big twelvess in