I have this solar charger:



http://www.harborfreight.com/cpi/cta...emnumber=44768

I cut-off the cigarette lighter adaptor, and put a pair of alligator clips to go straight to the battery.

With my meter, it is putting-out 21 volts, and it is supposed to do. It is rated at 1.5 amps. During the day, in sun, it keeps the battery nicely charged. But, come the morning, I get more of a loss then if the charger were not connected, so I'm guessing that I'm losing the charge by it going outward...

That being the case, what could I use to prevent this? I believe a voltage regulator would work, but there might be something else as well. Is there something like a photo-sensitive switch that turns-on or off depending upon light? Curious to hear of any ideas, as opposed to connecing and disconnecting every day...

Thanks for your ideas!

 

I'm not sure a voltage regulator is going to help with the drain but I think you should get one anyway. 21 volts is way too high to be pumping into the battery. It should be like 14.5 or 15 volts max.

 

A 1N400x or 1N540x series diode is all you need to prevent drain in the dark.

Like this

Just wire it in series with the + wire.

That panel is rated 1.5 Watts, that is 107 mA (aprox. 1/10 Amp) @ 14 Volts. No need for a regulator with so little current.

 

Thanks for the fast replies guys!

I was a bit worried when I saw that it had an out of 21+ volts. I realize that the MINI charges it at 15 or so... But, this unit was designed to charge 12 v batteries, ie, for automative applicaitons. Will I damage the battery by charging it with this set-up? I might add, it this battery (Braille):

 

Honestly, I really don't know if it'll harm the battery. If it's designed to charge 12V batteries, I'd suspect it's ok. As Possum said, the current is so low, it shouldn't be able to push enough current into the battery to harm it.

 

My dad seems to think the same also. Thanks for the confirmation.

Well, I got the diode on the way home, from Radio Shack. I almost got a 1 amp one, but got the one you refrenced though. The price delta was less than a buck...

Last question: What is the proper orientation to "install" this diode? If the opposite of what I want, it will not allow the solar panel to charge the battery, and only drain the battery. Not sure of the polarity basically.

I suppose I can get out my meter and figure it out though.... Thanks much for sharing your knowledge.

 

White stripe goes towards the battery.

 

You guys are awesome! I'll solder it in tomorrow. Thanks much, I really appreciate the information.

 

I feel compelled to provide an update as the diode did not work as hoped with the stripe toward the battery. It was not allowing the solar panel's voltage to regsiter on my voltmeter, past the diode. Before it, I got the usual 21 or so volts. I should have checked first prior to soldering and shrink wrapping though...

I reveresed it such that the stripe was on the solar panel side, and it worked. I have it charging now...

In case others need to do the same, I'd recommend to test it first to make sure what way it should go...

 

may i ask why you need to charge the battery so often?

 

Update: Just spoke with my dad, and he's convinced that the stripe should go as mentioned in this thread, on the battery side, positive lead. After telling him my situation, he actually bought a couple of these diodes to experiment with, and it worked fine for him...

I cut the ends of the diodes down a good bit as I didn't need for them to be that long, so I wonder if that is why it didn't work properly. Or, maybe upon soldering, I got it too hot, and damaged it?

I just measured my battery's voltage, and it had dropped a little, so I'm covinced that something is wrong. I'm going to try the other diode (two are in the package).

Ken, I just returned from a two week biz trip, and the battery was dead. I typically only drive my MINI one to maybe two days a week. If I go beyond 7 days, she's dead. Again, I don't have a normal battery. But, FWIW, even folks with stock and stock-like batteries have been complaining about losing charges when not driving daily or fairly often.

Back to the drawing board...

 

With everything wired up, the voltage on the solar panel side of the diode should be about 700 mV higher than the battery side of the diode. For example, if the battery is 13.5 Volts, the solar panel should be about 14.2 Volts.

You will only see 20+ Volts from the solar panel when there is no load connected to it.

 

You may also want to find out what's draining the battery while the car is stopped....

 

With this battery's float and possibly age/condition, I'm not certain that it's being drained excessively, or beyond that of any other MINI. A few other MINI guys with these SLA batteries, including Dr Obnxs, have experienced the same. And as I said earlier, even with normal type batteries, there have been complaints (threads) about quicker than expected battery drain. That all said, I might have an additional drain that is the culprit, and how to pinpoint that is something not so easy to do... I heard things about keeping the car key too near might somehow do so.

If I can get the solar charger to work properly, I'm perfectly fine with that "solution." I currently have the diode removed, and the panel is charging the battery, which registered 11.89 v this morning .

I'm going to bring this set-up to my pop's house as he wants to do some experimenitation with me. I'll report back any findings...

 

Do you have an alarm system? My factor alarm will drain my Denka battery in less than two weeks flat if I don't run the car. Leave the car unlocked and it lasts longer (not sure of how long, haven't had the time to find out).

 

Thanks for your input. No, no alarm. And, I actually left it unlocked last night thinking that this might help; so I'm glad to hear that it might. I live in a canyon, a very rural area, with a fair amount of land, and with no real neighbors or folks, leaving her unlocked is no big deal. Thanks.

 

Met with my dad, and he showed me that the diode needs to be used as described earlier. He did so with different "experiments" using a fully charged 12v battery as the source...

I then took-out the solar panel, and showed him how it generates 21+ volts with no diode (panel connected directly to voltmeter). With the diode in place, stripe side toward the battery (if connected), it read nothing. He thought since the current is so low, that maybe that was the reason... Reversing the diode, the voltmeter, showed 21 volts, and that was the reason I installed it in the manner that I did orginally. He said for the heck of it, go ahead and put the diode as it should be and monitor the battery. I did so, and after a couple of hours, it dropped a tad.

I measured the amperage, and got from 25-37 miliamps, depending upon sun exposure. I'm contemplating a more potent solar panel, so if anyone else has any ideas, please share. Thank you.

 

Measure the idle current draw of the car to determine how big the solar panel should be. Wait an hour after closing the doors and hatch so the car will be sleeping. Should be around 50 mA. If it is 100+ mA, something may be wrong.

Get a panel that is at least 6 times what the idle current draw is. (Sun for 8 hr/day, real output = half of rated power)

5 Watt (275 mA) solar panel with charge controller

 

oPossum, thanks for chiming-in again...

I have a 4.8w panel on order, and it should be here by Tue or Wed. It has a built-in diode...

After seeing how low the amp output was on the panel, there was concern. That said, after putting the panel in good sunlight, perpendicular to it, I saw about 90 miliamps. But, nothing near the 125... and most of the time (conditions) it generates in the 20-30 range, so not much umph.

My pop thinks that maybe the panel got damaged by the battery discharging into the panel; and that could be why it is low on current production. That is why I placed an order for a new solar charger...

Of interest, I noticed in the instructions for my current panel, it states that it will not drain the battery when there is no sun. So, I'm guessing that it must already have a diode, and if so, I sort of wonder if adding another, like I was doing, somehow gave me those goofy results. Oh well...

Idle current draw? I'm not sure I follow the logic. When the car is running, idle, or under load (the engine), the battery is being charged at 14.5v. I have a voltmeter gauge, so this has never been a concern. Don't I want to know the draw when the car is at rest? You know, after reading your post, I think that is what you are saying. Not idle as in engine idle...

Makes sense alright. I wonder if my voltmeter can handle such a measurement? I'll check it out... Thanks again for your assistance.

 

I was thinking idle electronics, not idle engine. Poor choice of words. Should have said sleeping current draw. Don't attempt to measure current with the car running! Could be 100+ Amps! Connect the meter between the negative battery terminal and negative battery cable. That way if something shorts to the car body, nothing bad happens.

Solar panels rarely produce full rated power. 20% to 50% is typical. I don't think your panel is damaged. The diode may be in the panel or in the cig ligher plug that you cut off. If it is in the panel, then the voltage drop from two diodes (one in panel, one external) would be 1.4 Volts - still should be able to charge the battery. A current meter between the solar panel and battery (no external diode!) would tell you if it has an internal diode. Current flow in sunlight and dark = no diode, current in sunlight but not dark = has diode in panel. If you still have the cig lighter plug, it could be disassembled to check for a diode.

 

My car has sat for weeks at a time with alarm set. If your battery is draining in only 2 weeks, IT IS BAD. Replace it, or at least have a garage do a load test on it.

If the battery is ok, then you have to track down a short somewhere in the elctrical system upstream of the ignition relays.

A charger, if needed at all, should only be required in extreme cold.

 

I appreciate the info guys. oPossum, you were clear, I just rushed in reading it, and replying... I will do more testing tomorrow, as you suggested. I'll report back what I find...

With these batteries, extreme heat is more of a culprit (compared to the cold), at least from what I've read. Either way, from the few of us that have them, they drain faster than the typical battery. It's a compromise that I'm willing to live with as it has paved the way for my straight exhaust system (battery box removal), and extra weight loss...

I'm curious to see if my MINI's idle current draw is normal, assuming I/we have such a baseline! Thanks again for your input...

 

I don't think you've mentioned what type of battery you are running. Gel Cell?

 

In the 4th post I mentioned that I use a Braille battery:

http://www.brailleauto.com/ProductCa...=2&idproduct=1

Disregard the price listed as it can be had for 1/2 of that, or even less...

These are sealed lead acid batteries (SLA). I learned a fair amount about these types of batteries here:

http://www.stealth316.com/2-dynabatt.htm

A search here on NAM will reveal a few threads on these batteries, if interested.

 

Engine off for a while, rear boot open, internal lights on = 1.95A (seemed pretty high). After a bit of time, something happened to where it dropped to 1.62A...

After closing the rear boot, it once again registered 1.95A. A minute or so later, it dropped to around 470 miliamps (lights had gone off). A little later, 150 miliamps, then 90, and after about 5 or so minutes it dropped further, and toggled back and forth bethween 10 and 20 miliamps! This was with the doors unlocked. I did the same with the doors locked, and got the same, actually it seemed closer to 10 miliamps. I was using the 10A scale, so not the best increments to discern these smaller current draws...

So, I'm pleasantly surprised to see an "idle" current draw of between 10-20 miliamps. It's amazing that when hitting the automatic door locks, open or close, makes for some rather high spikes at 6A mininum. I saw 9, and even a spike around 12 or so...

Just wanted to report back what my MINI's BMR (Basil metabolic rate) is... The new panel should arrive by the end of the week.