50W off-grid testing unit

Re: 50W off-grid testing unit

Ken's right; the 20W panel is probably not contributing any real power.

However, a 46 Watt panel ought to charge a 33 Amp hour battery:
46 @ 77% = 35/14.2 = 2.4 Amps = 7% charge rate.

You may have the Steca programmed wrong. Unfortunately it's hard to tell the actual SOC with an AGM battery - can't stick a hydrometer in it!

What have you got the charge Voltage set at, and how long is it staying there? And what is the resting Voltage of the battery fully charged?

If you're charging from a conventional automotive battery charger, that may not be providing the necessary Voltage for proper charging so it may not actually ever be fully charged. It should charge from the panel. Try leaving it connect a for a couple of days without discharge and see if it comes up.

BTW: 18 Watts for 16 hours is 288 Watt hours. At 12 Volts that's approximately 24 Amp hours, or 72% of your battery's capacity. These numbers don't add up to 62% SOC and may add up to "destroyed battery", especially as it doesn't include any power lost to the system (are you using an inverter or is this a DC CFL?)

Re: 50W off-grid testing unit

bctps55 wrote: »

Hi Aka,

Let me explain what I did. Due to the sun radiation is not strong these few days. I connected the battery to charge controller then connect the regulator to the solar panel input hole of the charge controller.

I have to ask: what is this "regulator" you refer to? The normal connection for a solar power set-up runs like this:

Solar Panel(s) ---> Charge Controller ---> Battery

If you're charging the battery from another source (such as a battery charger) it should connect directly to the battery, not through the charge controller. It could damage it.

I charged for around 6hrs and the Volt of the battery reached 12.92V. I have the battery rested for 1day and it return to 12.72V.

Yes that is a good, fully-charged "at rest" Voltage.

I then reset the charge controller, it SOC show 80% charged.

The charge controller have auto switch off when battery drop to 30%, but due to the charge controller read 62%, so it never switch off itself.

I am using a 12DC CFL.

I ask Steca support, they said it normal as the SOC need 1wk to learn and save the data in order to have accurate reading... Is that true?

Btw, when recharge and charge controller said 64%, I continue to discharge with the CFL bulb for 16hrs as it drop to 44%. I check it with the voltmeter, it show only 11.16V left on the battery. So, I reset the charge controller and it now show 0% left.

Did I screwed up my charge controller??

Maybe, maybe not. Depends on the answer to my first question regarding the "regulator". I think Steca's answer about the controller needing to "learn" SOC is no doubt accurate. Most battery meters and the like have to be told "this battery is fully charged and has a capacity of 'X' Amp hours" in order for them to keep track of the SOC. Apparently the Steca figures it out for itself, given enough time.

You are still drawing a lot out of that battery using 18 Watts for 16 hours. Reduce the discharge time to 10 hours; that bulb draws approximately 1.5 Amps @ 12 Volts. In ten hours that's 15 Amp hours - nearly half the capacity of your battery. You should not draw a battery down below 50% - it can kill it very quickly.

Re: 50W off-grid testing unit

Niel;

I know. I wouldn't recommend it either.
Just worried someone might feed the not-quite-fully-rectified DC of a cheap battery charger into a charge controller which might not like it. The panels might not like it either. You just never know 'til you get all the details.