Do I need a diode?

4 Posts

Dec 29, 2006 04:39 pm

Do I need a diode?

PV system consists of 5 Solarex 60 watt panels in parallel to a Trace C35 controller charging 6 6VDC 220AH golf cart batteries tied into three 12VDC banks.

The Solarex panels were acquired as military surplus and all show ~ 20 VDC in full sunlight.

Location is in the Olympic Mountains in Washington State.

The array will not bring the batteries up to full charge, but if I use a genset and charger, they will charge up fine. The Trace is set up OK.

I am wondering if the panels are drawing power from the batteries, if I should re-wire into series or???

All advice is welcomed.

Thanks,

Jan Nelson

351 Posts

Dec 29, 2006 07:23 pm

Re: Do I need a diode?

You need a lot more than a diode.

Depending exactly where you are, you can expect about 2 hours of full sun at this time of year. That is about 600 watthours of solar generation a day. (it will jump to about 1300 watthours in the summer)

You did not say what your loads are, but my guess is that your electrical usage probably exceeds the 600 watt hours a day, probably by quite a margin.

You are trying to fill 7920 watt hours worth of batteries with about 600 watt hours.
When you discharge that bank more than 7.5 percent, you just don’t have the generation to fill it.

I could be wrong, but without any load data, I think you just don’t have enough solar panels (especially for this time of year).

Ken

4 Posts

Dec 29, 2006 07:52 pm

Re: Do I need a diode?

Thanks for the reply Ken. In fact, I have zero demand on the system this time of year and only on weekends in the Summer with demand being a few CF bulbs for a few hours in the evening.

So is it not possible to use a small PV array to charge a battery bank that is otherwise sitting there doing nothing?

Thanks,

Jan

351 Posts

Dec 30, 2006 01:51 am

Re: Do I need a diode?

With zero demand on the system, the panels should be keeping the batteries topped off. Or if you did disharge it about 20 percent, it should bring them back up full in about 3 days or so.

The C-35 does have an automatic PV night disconnect in it, when in charge control mode, so you should not need a diode.

Perhaps you should give us more details. When did you install the system, when did you first notice a problem, did you ever measure amperage between the controller and the batteries, what color of LED do you have, and is it solid or blinking (what is the blink count), do you have the optional display ?

The more info you provide, the more likely one of us is like to see something.

Ken

4 Posts

Dec 30, 2006 11:25 am

Re: Do I need a diode?

The array has never topped off the batteries, the C35 is always in a blinking green status unless I actually use the system to the lower threshold of getting an alarm and the led then goes red.

I have created a small microhydro prototype that I also connected using a C40 in parallel to the PV arrray/C35 wit hthe C40 set to diversion into a heat element. The batteries would fully charge with this system running and the C35 would show a solid green.

The hydro generator was prototype and is out of service while I refine it, but I am still concerned about the fact that the PV array will not bring the batteries up. The highest voltage I have measured on the batteries using the array only is 12.3

I have not yet checked for amps between the array and batteries, only volts. The open circuit volts at the array circuit breaker is 19.3 typical in the sun, the volts when connected to the batteries is, well, the voltage the batteries are charged to.

351 Posts

Dec 30, 2006 02:32 pm

Re: Do I need a diode?

Jan:

The 19.3 open circuit voltage bothers me. Most Solarex Panels should have a OCV of 21.1 volts. Did you test the OCV of the panels individually before installing ? It would probably be worth the effort to do it again.

A weak panel could be dragging down the whole array. Having equal voltage readings somewhere close to 21 volts is more important than hitting the exact number.

You could also put a test load directly on each panel and see what the voltage drops to.

If you have a panel that is substandard to the group, try wiring up the remaining 4 to see how the array works without the weakling.

Ken

4 Posts

Jan 4, 2007 11:18 am

Re: Do I need a diode?

That is what I'll do on my next trip out to the site. Thanks for the advice.

Disclaimer and Disclosure

The Alternative Energy Store, Inc reserves the right, within its sole discretion, to refuse or delete any posting or portion thereof, or terminate or block the access to this forum.

The opinions and statements posted on this forum are the opinions and statements of the person posting same, and do not constitute the opinion or act of the Alternative Energy Store, Inc (AltE). The Alternative Energy Store, Inc does not endorse or subscribe to any particular posting. No posting shall be construed as the act or opinion of the Alternative Energy Store, Inc.

Click here for BBB Business Review

Desktop Website | Mobile Website

Share

Click on an icon to share! If you don't see the method you want, hover over the orange "+".

Feedback

What can we do to help you?

Sorry, the copyright must be in the template.
Please notify this forum's administrator that this site is using an ILLEGAL copy of SMF!

Copyright removed!!