2 solar panels to one battery bank, but at different states

[jbinbi]

So I have 2 285 w solar panels adjacent to each other each going to a separate eco worthy mppt controller ( manual if you want to see it http://eco-worthy.com/catalog/download/20AMPPT.pdf ).

From each controller I go to a 3 blade fuse holder to the pos terminal of my battery bank. So each controller should be reading the same battery voltage.

Yet when I checked yesterday (under a berth, so not so easy to see all the time), one was in float, the other was not, one was at 14V the other at 13.7V. Both are programmed for the same voltages per stage, so this is very confusing to me. Since the panels are right next to each other, I would think they should be getting close to the same sun (they are both over the dinghy davits), they should be putting out the same V. Am I wrong in assuming this?

[john61ct]

Should be based on battery state and absorb time, not panel state.

Not exactly top tier SC, maybe variability. Same wiring? Make sure programming the same?

And why those voltages? What model battery?

[jbinbi]

same wiring, same programming.

exide dual wet cells, bulk at 14.8, float at 13.5-8.

[john61ct]

Not really deep cycle, how old?

I wouldn't worry much, but if you want to diagnose, try one at a time.

Bring float a bit lower so it's more clear. You really should be able to hit that Bulk setting.

Also, what are you using to monitor volts, and ideally amps? Don't trust the SCs, or really any charge source.

[jbinbi]

thanks for the input. Not sure why you think not deep cycle? stock house battery from lagoon. 2 years old.

the controller tells V and I; I also have put a voltmeter on it, and the battery.Since it is under the berth , a pita to see. Don't monitor amps continously yet, have ammeters, but not yet installed between controller and battery yet.

[john61ct]

Originally Posted by jbinbi

Not sure why you think not deep cycle? stock house battery from lagoon. 2 years old.

Exactly. Manufacturers cut corners, cater to the bottom line.

True deep cycle are not available in consumer retail big box channels, at least not in 12V. The term is widely used fraudulently.

http://www.pbase.com/mainecruising/deep_cycle_battery

Learn more about the topic before you buy your next bank, in the end they are consumables. If your bank has been worked hard, and not brought up to 100% full most cycles, that may be sooner rather than later.

Originally Posted by jbinbi

the controller tells V and I; I also have put a voltmeter on it, and the battery.Since it is under the berth , a pita to see. Don't monitor amps continously yet, have ammeters, but not yet installed between controller and battery yet.

I would do that, ignore the SC readings in the meantime, and confirm/calibrate your instrument's accuracy with a pro's tools.

[smac999]

Obvisuily if both controllers are connected to the same fuse block. The v out will be identical. Even though it says they are not. Unless you have a bad connection at the fuse block. Measure the voltage direct at output of controller and at fuse block.

[CaptWil]

HI
May I ask why you simply did not use 1 solar controller instead with higher amps rating?
I have the same capacity wattage from 2 solar panels directly to 1 solar controller 40 A and it works well recharging my 300 Amps trojan T31 house bank in less than 3 hours on a sunny day, about 6 hours on a cloudy day. Probably will increase the house bank to 400 A soon
Cheers
William

[Mr O]

You are wise to install 2 MPPT controllers so that if one panel is shaded, the other one will have full output. This is what I plan to install on my boat. Regarding the difference in voltages, maybe one controller is seeing voltage from the other and I am curious as to how the 2 controllers work together to charge the batteries at the proper rate.

[john61ct]

As long as they have the same or similar setpoints, no problem.

And no major issues even if they don't.

[jbinbi]

Originally Posted by CaptWil

HI
May I ask why you simply did not use 1 solar controller instead with higher amps rating?
I have the same capacity wattage from 2 solar panels directly to 1 solar controller 40 A and it works well recharging my 300 Amps trojan T31 house bank in less than 3 hours on a sunny day, about 6 hours on a cloudy day. Probably will increase the house bank to 400 A soon
Cheers
William

Redundancy. I also went with an inexpensive controller, $99 each for 20A. In theory I can get a bit more than 20A from a 285 W panel , though not very much and I need perfect conditions. I had considered a victron high quality controller, but to get 40A, it became much more expensive than I thought I needed. But maybe not....

[john61ct]

If you are willing to experiment, and have a way to accurately and independently measure charging amps, a Victron 75/15 is under $100. It will self-limit to ~220w in peak conditions, but I wouldn't be surprised if the better quality circuitry didn't get you greater overall output.

Perfect conditions for an A/B test keeping all other variables constant. And you could purchase from a vendor with a NQA returns policy, just cost you the return shipping.

[jbinbi]

Originally Posted by john61ct

If you are willing to experiment, and have a way to accurately and independently measure charging amps, a Victron 75/15 is under $100. It will self-limit to ~220w in peak conditions, but I wouldn't be surprised if the better quality circuitry didn't get you greater overall output.

Perfect conditions for an A/B test keeping all other variables constant. And you could purchase from a vendor with a NQA returns policy, just cost you the return shipping.

Not a bad idea. Actually, just looked at victron controllers, for $300, they have a 50A controller. Now thinking about using just a single controller for both panels. Their 20A are $200 each, so it would be $400.

[john61ct]

Redundancy rules.

Plus I've seen the 75/15 for as low as $85

But really I want to see the results of that experiment 8-)