is it okay to leave panel disconnected while in sun?

[Sunking]

Yeah, you're right. I didn't know until I joined all you great guys (yeah, I'm gettin' a little choked up too, right now.... sniffle..) that aviation batteries use stronger acid(1.285 S.G vs 1.260S.G.) and thus the voltages are a little different. Back to the Gill Battery FAQ page...

The next thing is the Morning Star unit. I have two questions:
1. How much are they?
2. Can they be adapted for my battery switching unit?

I am just about to the point of simply doing the whole thing with a microprocessor anyway. The first cut would simply be a Ping-Pong style unit to keep the batteries all topped off, on at 13 and off at 14 volts for a regular battery, 12.8 and 13.4 or so for the airplane battery. Something like that.
I know it isn't the theoretical ideal, but it's way better than simply letting the batteries run dead, then charging them off my generator just enough to get the plane going, or jump starting it then hoping it got enough for next time.
I could then refine the design to include a PWM charging feature.
Another good thing about this would be the fact that I could use different charging levels for different battery chemistries, aviation vs. automotive, or even NiCad. I could even add a Lipo charge controller IC, which go for a buck or two at the IC level.

But I know, talk is cheap.. gotta get to work.

No need for a processor to make a FLOAT charger. Just a simple LM-317 shunt regulator will work better than and cheaper than a processor. Only takes 5 parts you can solder together.

[Mike90250]

...

The next thing is the Morning Star unit. I have two questions:
1. How much are they?
2. Can they be adapted for my battery switching unit? ...

http://www.morningstarcorp.com/products/sunsaver-duo/

....DIP Switch 4
–
Custom Setpoints
If the standard battery type settings are not suitable, custom charging setpoints
can be programmed using a PC and a Morningstar Serial to Meterbus adapter
(not included).
See Morningstar’s website
for more information.
DIP Switch 4 OFF: Factory settings (factory pre-set)
DIP Switch 4ON:Custom programmed settings

peek into the manual, see if the factory setpoints would work. About $150 bucks, Be sure it's the Duo model.

[rug_burn]

No need for a processor to make a FLOAT charger. Just a simple LM-317 shunt regulator will work better than and cheaper than a processor. Only takes 5 parts you can solder together.

I like that LM317, that's perfect for the job. What does one do, just set it for the desired float voltage, like maybe 13.4 volts, and let the natural behavior of batteries do the rest? Keep in mind my panel is putting out less than an half an amp in that situation. Just set it up like you would for supplying a specific voltage to any circuit?

[inetdog]

What does one do, just set it for the desired float voltage, like maybe 13.4 volts, and let the natural behavior of batteries do the rest? Keep in mind my panel is putting out less than an half an amp in that situation. Just set it up like you would for supplying a specific voltage to any circuit?

Yes. With the caveat that if the battery temperature will vary over a wide range then setting a single constant FLOAT voltage without temperature compensation may not be good enough.

[Sunking]

Yes. With the caveat that if the battery temperature will vary over a wide range then setting a single constant FLOAT voltage without temperature compensation may not be good enough.

Well if it is a flooded battery of no real concern. If AGM and only using a panel with enough current to be just a Trickle Float Charger say at C/40 to C/100 would be of no concern as it would be impossible for thermal runaway. Kind of like trying to warm up a house with a candle.

If one really wanted some minimum temp comp can easily be done by using a resistive voltage divider using either positive or negative coefficient resistor as one of the divider resistors.

Anyway I was just trying to help the guy do this as inexpensively as possible. Shunt and Series regulators like the LM 317 are dirt cheap. Old tech but still very effective if efficiency is not the main concern, and in this application efficiency is of no concern. His plane Magneto/Alternator will be doing all the real work. The panel is just a Maintainer or Trickle Charger. Heck get the right size panel all one would need is just a simple diode. If you really wanted to go cheap you can still find some ole school panels with only 32 cells that require no controller at all, just a diode. I think Shell Oil was one of the first to make them and still around here and there. Oil companies had thousands of them for telemetry and still in use today on pipe lines and remote weather stations.

[rug_burn]

Well if it is a flooded battery of no real concern. If AGM and only using a panel with enough current to be just a Trickle Float Charger say at C/40 to C/100 would be of no concern as it would be impossible for thermal runaway. Kind of like trying to warm up a house with a candle.

If one really wanted some minimum temp comp can easily be done by using a resistive voltage divider using either positive or negative coefficient resistor as one of the divider resistors.

Anyway I was just trying to help the guy do this as inexpensively as possible. Shunt and Series regulators like the LM 317 are dirt cheap. Old tech but still very effective if efficiency is not the main concern, and in this application efficiency is of no concern. His plane Magneto/Alternator will be doing all the real work. The panel is just a Maintainer or Trickle Charger. Heck get the right size panel all one would need is just a simple diode. If you really wanted to go cheap you can still find some ole school panels with only 32 cells that require no controller at all, just a diode. I think Shell Oil was one of the first to make them and still around here and there. Oil companies had thousands of them for telemetry and still in use today on pipe lines and remote weather stations.

With the size of my panel in this application, overcharging isn't going to be a big problem, but the regulator is a perfect solution.

I figure if the battery naturally discharges about 1% of its charge per day, that's about .350 A-hour for a 35 Ah battery. So if charging is 50% efficient, and we have perhaps 7 hours of usable sunshine per day that works out to .1 Amp charging current just to keep it topped off. So I set up the LM317 with an adjustable pot, and dial in 100mA current to a fully charged battery and it stays topped off. I can do that. Gotta work that into my multi-charger plan, but for now, it's good for a set-and-forget battery maintainer.
Thanks for the idea, SunKing.

So what about the temp compensating voltage divider? What type of resistors are positive and which are negative coefficient?

[rug_burn]

or maybe just set the LM317 voltage for the float voltage of the battery, better yet...

[Sunking]

No do not use the LM317 as a current source. You do that by panel wattage selection. However if you use the 317 as a voltage regulator, you can use as large of a panel as you want because you are controlling the voltage. Battery will control the current assuming the panel wattage does not exceed a C/8 charge current.

If your battery is 35 amp hours you can use a panel wattage as low as 5 watts up to 50 watts. The only thin gI would worry about is I think you said it was a Thin Film panel? If so the voltages could be too high to work with using a simple LM-317.

On the other hand if you want to make it super simple is to just by say a 5 watt with a Imp of .2 to .3 amps and just connect it directly to the battery via a Blocking Diode so the panel cannot discharge the battery at night. Use 4 or 5 Blocking Diodes in series to make a super simple voltage regulator to prevent over charge if setting for months.

Lot of ways you can skin this cat. Only issue I would have is the fact being used in a plane where you want the best reliable obtainable. Having said that I assume all the battery has to be able to do is start the engine while on the ground. If it can do that then you know the battery should be good to go for flight.

[PNjunction]

Yeah, you're right. I didn't know until I joined all you great guys (yeah, I'm gettin' a little choked up too, right now.... sniffle..) that aviation batteries use stronger acid(1.285 S.G vs 1.260S.G.) and thus the voltages are a little different. Back to the Gill Battery FAQ page...

I know you've moved on to the DIY approach knowing this but still as a warning to lurkers...

This is one major reason that there is a very specific line of Battery-Minder chargers for aviation, closely tied to specific batteries, like Gill, Concorde, Enersys etc. Choose wisely.

Quick note about the "desulphation" - they DON'T use high-voltage spikes like most of the junk desulphators out there, but sweep a range of freqs under the strict voltage limits. However, when was the last time you got from a manufacturer the sense they are hiding nothing, provide full docs on what they do, and even go into great detail on making hydrometer measurements with voltage/soc charts/gravity charts for flooded batts - with aviation in mind for their aviation specific line!

Even if this doesn't interest you, it may be useful to read the easily-downloaded manuals for the products just to get an overview to see if your diy project is in the ballpark.

[Sunking]

I know you've moved on to the DIY approach knowing this but still as a warning to lurkers....

When I was part owner of a Mooney, nothing less than a Concorde for our plane. Concorde is default for all military and commercial aircraft and for good reason. Besides Concorde invented the AGM battery.

[rug_burn]

When I was part owner of a Mooney, nothing less than a Concorde for our plane. Concorde is default for all military and commercial aircraft and for good reason. Besides Concorde invented the AGM battery.

Well, the Gills are made locally, or almost so, and they work fine.
I made an LM317 based regulator, and it seems to be doing the job just fine. I have the voltage set to about 13.6 volts. When I check the battery voltage an hour or two after the sun goes down, it's always right around 12.8 volts. This is a huge improvement over letting it simply discharge and having only 11.8 volts or something, and hoping it'll start, and then flying at $50/hour gas cost just to charge it up a little...
However, I think I'll ramp up the regulated voltage over the course of a couple weeks, to bump up the evening voltage up above 13 volts. Lead acid batteries start boiling out the electrolyte over 14 volts, if I'm not mistaken, so I'll keep it no more than 14 volts.

[Jnadeau]

I would Just like to verify this threads information.... I'm installing a new system, (for which I've chosen the L16 batteries based on this websites advice) but I will be waiting two weeks for the batteries to come in....

So my question is this: can i safely install my new panels and leave all of the individual leads diaconneted for the next two weeks before my batteries arrive without damaging the panels? From what I understand the answer is Yes, but I just want to be sure.

[bcroe]

So my question is this: can i safely install my new panels and leave all of the individual leads diaconneted for the next two weeks before my batteries arrive without damaging the panels? From what I understand the answer is Yes, but I just want to be sure.

Yes. Bruce Roe