Solar That Really Works

[Wetboy5776]

Originally Posted by computerguy

Wet boy,
Where you going to be?
I could use a trip...

I'm in Central Florida till Spring Break...then I'll be working my to Vegas in March. C'mon down! The weather's fine!

BTW...if anyone in FLA is looking for a like new 190 watt Sun Elec panel, I'm looking to sell mine at same cost I got it...$345. Save $70 on shipping! It puts out 11-12 amps in full sun. I'm going to be making a smaller folding system with two smaller 100 watt panels when I sell this one.

Here is the web link......
http://sunelec.com/index.php?main_pa...53881770a65e06

[HandyBob]

Originally Posted by SpursMVP

Question guys. How often do you equalize your batteries?

Never or only when the batteries get old, just as it says in my blog. Golf cart batteries that are properly charged with temperature compensated solar charging rarely need equalizing. I have a lot of friends who will attest to this as true. L-16's are a whole different kettle of fish, but they don't belong in RV's.

I may have to test them in a few days though, because we are currently breaking the longest number of cloudy days in a row down here in southern AZ and we have not been charged for that long. Eight days & counting. Undercharging is what causes batteries to need equalizing. Not having a generator has put a crimp in our style, now in severe conserve mode, not using anything big except Mr. Coffee and limiting TV use. However, we do have one of the noisiest back-up chargers there is and we used it yesterday to get us back up over 60%.... A Ford 7.3L diesel hooked up the the trailer batteries with booster cables, which puts over 30 amps in. I wouldn't recommend idling one of these things all the time but this is only the third time in about seven years. Right now with the small inverter running the lap top & the sewing machine and in light rain we are seeing -2 to 3 amps (at 60%). We can do that all day long no problem. The sun will come up tomorrow.

[KJINTF]

Bob

Up here in NW Montana we are seeing clear, cold and sunny skies for the past several days. Perfect weather for the PV panels. No issues with the batteries getting charged up poroperly and no need for the large diesel generator.

However as we all know things change

Ken

[Bob/Becky D - VA]

Reading through this series of posts, I noted that much of the post has been related to the relative merits of Handy Bob's recommendations. I have viewed his site numerous times over the last year and agree with most of what he has posted. However, I don't recall seeing in these posts any discussion of other RV'rs who also have considerable experience in this area and provide it in a reasoned manner. One such individual is Jack Mayer and I have found his site to be just as informative. Some of you may also find his recommendations a good source of information as well.

RV Electrical

Not trying to say one is better than the other, but I find both to be useful.

Happy travels.

[SpursMVP]

Originally Posted by HandyBob

Never or only when the batteries get old, just as it says in my blog. Golf cart batteries that are properly charged with temperature compensated solar charging rarely need equalizing. I have a lot of friends who will attest to this as true. L-16's are a whole different kettle of fish, but they don't belong in RV's.

Thanks for the input Bob. I've got our charge controller set up to do this automatically every 30 days so I figure I'll turn off this function.

Man...these panels rock. As Handy Bob's webpage points out many people are suffering from undercharged batteries and this was our problem.

Our 400 watt solar system keeps everything topped off very nicely. Our RV has a 7.5kw diesel generator and now it only gets used in the summer months to run the A/C units while boondocking. It gets WAY too hot down here in Texas to try and gut it out w/o A/C

[WheelingIt]

Originally Posted by WheelingIt

Thanks RocketDork and Handybob - I was worried about the higher 15.5V absorbtion charge esp. for our internal electronics. It just seemed really high (!) and I couldn't figure out the right balance between that and the 14.4 bulk charge they mention on the website. I will try calling them too and see what they say...just for fun. They'll probably say exactly what's on the website, but you never know. I'll write back if they give me anything useful.

Just want to ping back on this. I didn't get anything useful from calling the Interstate battery manufacturer other than what they have on their website so seems handybob's 14.8V suggestion is the best out there. In the end we decided to change out our batteries...partially because we were able and also because hubby's dad managed to fry his own batteries (running them completely dry no less) so our old ones had a good home.

Although I've not commented much on the thread, it's really helped us w/ our own solar installation, so appreciate everyone who kept it going.

[ralper]

Since I made this original post there have been 10,631 views. This is many more views than any other subject here. That tells me there is a very great need for accurate solar system information and I am happy I could do this for all of you that have viewed it.

[Midniteoyl]

Some of those are people who got 189 'replies' in thier email

[computerguy]

Originally Posted by Wetboy5776

I'm in Central Florida till Spring Break...then I'll be working my to Vegas in March. C'mon down! The weather's fine!

BTW...if anyone in FLA is looking for a like new 190 watt Sun Elec panel, I'm looking to sell mine at same cost I got it...$345. Save $70 on shipping! It puts out 11-12 amps in full sun. I'm going to be making a smaller folding system with two smaller 100 watt panels when I sell this one.

Here is the web link......
http://sunelec.com/index.php?main_pa...53881770a65e06

If you're still going to be in Vegas in March? Maybe we can meet up and get my solar install done. Sent you a pm

[jimbo16720]

Originally Posted by RocketDork

I've been reading this stuff and HandyBob's page. I'm scratching my head a little bit here.

When we charge a battery, we are putting in power. Power is measured in Watts. We don't care about volts, or amps. Power is what we use to make all the electrical stuff function in our coaches.

When I start doing the math behind changing wire size in a hypothetical situation of a 25 amp panel setup, I can't make it all work out the way that Bob says it should...

When using 10 AWG I get a loss of ~40 watts, 6 AWG has a loss of ~15 watts and 1/0 has a loss of ~4 watts.

Total system power at a 17.5V Max power point would be 437.5 watts

So, when I make an assumption of using a perfect charger (energy in equals energy out), the total number of watts delivered in a typical day (4.5 hours full power equivalent) where I live would be;

10 gauge - 1788 watt/hours
6 gauge - 1901 watt/hours
1/0 gauge - 1951 watt/hours
Superconductor, no losses - 1968.75 watt/hours

So, the dramatic difference that Bob notes is likely not ONLY due to wire size changes. The math doesn't add up. Delivered energy isn't different enough to explain it.

So, what else does he do?

1. Controller close to batteries
2. Adjust controller to deliver 14.8 V to the batteries
3. Maintain 14.8V for an hour prior to switching to 13.5V float.

So, taking a look at those changes to standard, I think this is where the magic is.

1. Charger closer to batteries will make the voltage delivered to the batteries closer to what the controller believes it should be. The voltage drop between the charger and battery will definitely have an effect on the state of charge of the battery at the conclusion of charging. This can be partially compensated for by having a voltage sense connection on the controller.

2. Adjust the controller to 14.8 V at the batteries. The standard line is 14.4V...14.8V is going to allow for more charging at a constant current mode than 14.4V. During the bulk charging stage of a three stage charger, this is where the real power is delivered. So terminating the bulk stage at a higher voltage is going to deliver more power to the battery prior to moving to acceptance charging. Power is what we are after...not volts, not amps, but the combination of those...power.

3. Maintain 14.8V for an hour prior to switching to a 13.5V float charge. I'm not sure why he's doing it this way, an hour isn't long enough for an acceptance charge to complete. However, 13.5V will continue to charge the battery at a lower rate and get it to a full state of charge, if there are enough hours to do it.

I've spend a significant amount of time studying battery charging techniques. I've talked to the experts in batteries at my job...I've arrived at what I think is making the difference in Solar Bob's system...

To charge a battery fast, our experts say...

1. Set the bulk charge voltage at as high a voltage as you can. The limiting factor is the out gassing of the electrolyte. The battery MFG's will usually tell you where this is. Flooded cell Lead/Acid only. AGM and SLA's are a totally different game.

2. Once you hit a predetermined voltage in bulk charge mode, maintain that voltage until the charge current drops to a small value...typically around 3% of the 20hour Ah rating.

3. Once you've hit the small current value, drop to a float charge voltage.

This is the typical 3 stage charger "algorithm". Step 2 is the hard one and is where virtually all of the chargers that I'm aware of make compromises. The issue is this, the chargers aren't aware of what current is going to charging the battery and what current is going to other loads (lights, water pumps, etc). The chargers are also unaware of what the 20 hour Ah rating of the battery bank they are charging.

If they aren't aware of these two things, they can't accurately determine when the acceptance phase of charging is complete. They MUST make a decision of when to stop this phase of charging or the charger will damage the battery. Most chargers make the decision to terminate acceptance charging after a specified time.

The acceptance charging part of the cycle is really only responsible for about 10% of the state of charge, so if you make compromises here, you aren't likely to really effect things significantly.

So, I think the magic in HandyBob's techniques come down to this.

1. Try to eliminate power losses in wiring. No reason to throw the extra away as heat. Depending on how things are wired, you could get 10% more power in a typical day.

2. Change the bulk charge termination voltage at the battery terminals from 14.4V to 14.8V. -THIS- is the magic. It allows the constant current mode of charging to continue for a longer time. More power is delivered, therefore, more power is available.

I need to devise an experiment to see if my idea is even close to reality.

So, after I made this post too long, what do you think?

Amps is what charges not watts, a 100 amp charger will charge your battery faster than a 1 amp trickle charger.

[ralper]

Yes but you need good voltage (14.8 volts) to push the amps into the battery. Voltage is the pressure and amperage is the volumn.

[RocketDork]

Originally Posted by jimbo16720

Amps is what charges not watts, a 100 amp charger will charge your battery faster than a 1 amp trickle charger.

-Power- (measured in Watts) is what charges a battery.

Not enough volts, no charge.

Not enough amps, no charge.

Just to beat the horse and make sure it's fully dead.

A 100 amp 6 volt charger will never charge a 12V battery, while a 1A 12V charger will.

You simply can not charge a battery to any level of charge without delivering -POWER-, a combination of Volts AND Amps.

[mfire1339]

Are we just trying to get to 200? I'm in.


Mike

[w6pea]

I need more Coffee & Old Bushmills......all I know for sure that the system I have on my RV works for what I need. 6 battery's 300w in panels and a 200w inverter. Have not had to run my generator in months.