Testing the voltage of a battery being charged

[spectralcanine]

I don't need extreme efficiency or anything right now, I am not planning on going off-grid any time soon.
This is just a project I am doing for fun, and the result should be lighting a couple of power leds at night over our dark stairs.

When I started working I pretty much knew nothing about electronics, but I am learning, so the next one will probably have better components, but for now I want to make this one work, even if not very efficiently.

[PNjunction]

Hyperion fun

Just a quick note about the Hyperion charger -

I think a visit to a racer/wheelchair driver that builds his own chairs, (NO sales, just personal use) charger setups, and is not afraid to slap an AGM hard (and also has a part in the SLA algorithm that Hyperion uses) can be seen here in both the site and the forum:

http://www.wheelchairdriver.com/

It truly is inspiring, and I think a pretty neat resource even if you are not in a chair. We're talking absolutely blasting agm's and not just tooling around the yard like grandma. And moving forward with LiFePo of course! (apologies to grandma's everywhere!)

[PNjunction]

I am not enthusiastic about getting another battery, because they cost a bunch.

Well, unfortunately during testing, you performed a high-voltage EQ on it AND surpassed the initial inrush current. Not good, and no longer trustworthy. Since you are looking at a battery replacement now anyway, might as well spend the extra bucks for a 10a agm, which will handle your panel current.

so I somehow need to dissipate any current above 2A.

Unless you are doing windmills, normally one doesn't want to do a dump-load with solar for spec-matching. Fine to prove a point, but one of the guiding principles of solar is to maximize efficiency.

I am using the Arduino to control relays (that act as electronic switches in this case, with one output being open circuit) and light simple leds (charging / charged) based on the readings.

Right on - about the only thing you can do is the 1970's style ping-pong regulation of choosing a high voltage point to disconnect the panel, and a low voltage to reconnect it. During the bulk stage, the battery will just gobble up as much as it can until the terminal voltage reaches 14.7 (or whatever you choose) and the panel is disconnected. The battery will then slowly drop down to your low voltage set point, the panel is reattached, and the ping-ponging begins.

Thing is, for about $10 you can buy a pre-made ping-pong solar charge controller and use the arduino for other stuff.

Here's a quick test of your existing battery. Assuming you have some way of fully charging it (ac charger etc), can you run your 300ma led load for 8 hours, and having 12.2V as measured on your battery terminals? This is a 50% DOD for the agm. If your voltage is much lower then either your battery is toasted, or you were never able to achieve a full charge in the first place. Hopefully you've got a quality multimeter around.

[Sunking]

I am not enthusiastic about getting another battery, because they cost a bunch.

That is an odd thing to say. Did you not know anything you take off-grid will cost you about 10 times more than buying it from the power company the rest of your life? Batteries need constant replacement. Battery replacement never ends, just gets more expensive each time you replace it.

My guess is you are in charging deficit. Meaning you need much larger panels and bigger battery.

[thastinger]

My bad, I thought it was Electric Bike, not a gasser. You did good shaving 9 pounds.

Why not eliminate the battery all together using magneto and external battery to start engine? Fuel pump and ECM?

A123 is gone.

I have a couple of buddies with remote start carts etc and that would really shave some weight off the bike but I usually go to the races by myself, or the wife reluctantly goes and the 6Yo and 3YO but none of them are going to be able to lug a remote start cart to the starting line for me so it's just easier to hit the start button and realy on my Ti and CF parts to get that other weight off lol

[spectralcanine]

The simplest way to limit the current is to size the panel to your battery. When the panel gets attached to your discharged 5a battery, it will gobble up as much current as it can. Since you have a panel capable of 3.6A output, this is too much initially for the battery. You can either modify your panel, or even easier, use a larger battery, such as a 10A agm which can now handle your panel's maximum output.

The "C" rate is typically the amp-hour rating of a battery under a 20-hour load. That is, your 5ah battery should sustain 250 milliamp load for 20 hours until the battery is considered fully discharged. Note that fully-discharged does NOT equal zero volts. We're talking 10.75 - 11v for the most part. Going below that voltage is going "past" dead.

This tells you right there that with your 300 milliamp load you should be able to get into the ballpark of 5 / .3 = 16 hours until totally discharged. BUT you don't want to use up more than 50% of your battery capacity, so cut that figure in half to 8 hours. In other words, you essentially only have a 2.5ah capacity to cycle with if you want long life. Use your load for less time, and the cycle life improves. (less depth of discharge)

But you are exceeding the initial current rating with your existing panel. Again, the easiest mod here is to upgrade to a 10ah battery. Guess what? Now you CAN go 16 hours with your 300ma led lights and only reach a 50% DOD state for cyclic use.

Sounds like your Arduino is only measuring things, and not controlling them. You need some sort of control. Current control without hacking up your panel is as simple as upgrading to a larger battery that can handle the current. But now you need VOLTAGE control to not exceed 14.7 volts as measured at the battery terminals. In a solar application, leaving it at 14.7 for the rest of the day until the sun goes down or dropping to a float voltage is a decision you'll want to make depending on how you want to handle it.

With no voltage control, I suppose the best you can do is fire off a klaxon-alarm warning you to pull the clamps.

I am not enthusiastic about getting another battery, because they cost a bunch.
Like I said, I ordered a DC-DC converter to regulate the voltage at 14.7, so I should be fine on that front, but the 3.6A scares me, since neither the battery nor the converter likes it.
In fact, the converter specifically states that it should operate to a maximum of 2A, and up to 3A with a heasink, so I somehow need to dissipate any current above 2A.
Is there some obvious way to do this that I am missing?

I am using the Arduino to control relays (that act as electronic switches in this case, with one output being open circuit) and light simple leds (charging / charged) based on the readings.

Thanks for the C rate explanation, it seems to make more sense now.

[Sunking]

Well, it is for drag racing so it only needs to go a couple of rounds and then I get some time in the pits to charge it back up. I did it for the weight savings of going from a 13.5Lb YB20 battery to a 4S4P A123 setup weighing in at 3 Lbs.

My bad, I thought it was Electric Bike, not a gasser. You did good shaving 9 pounds.

Why not eliminate the battery all together using magneto and external battery to start engine? Fuel pump and ECM?

A123 is gone.

[PNjunction]

I ordered a DC-DC converter to regulate the voltage, but I am not sure how to limit the current..........The datasheet says the battery should not get over 2A "initially", what does initially mean in this context?

The simplest way to limit the current is to size the panel to your battery. When the panel gets attached to your discharged 5a battery, it will gobble up as much current as it can. Since you have a panel capable of 3.6A output, this is too much initially for the battery. You can either modify your panel, or even easier, use a larger battery, such as a 10A agm which can now handle your panel's maximum output.

The "C" rate is typically the amp-hour rating of a battery under a 20-hour load. That is, your 5ah battery should sustain 250 milliamp load for 20 hours until the battery is considered fully discharged. Note that fully-discharged does NOT equal zero volts. We're talking 10.75 - 11v for the most part. Going below that voltage is going "past" dead.

This tells you right there that with your 300 milliamp load you should be able to get into the ballpark of 5 / .3 = 16 hours until totally discharged. BUT you don't want to use up more than 50% of your battery capacity, so cut that figure in half to 8 hours. In other words, you essentially only have a 2.5ah capacity to cycle with if you want long life. Use your load for less time, and the cycle life improves. (less depth of discharge)

But you are exceeding the initial current rating with your existing panel. Again, the easiest mod here is to upgrade to a 10ah battery. Guess what? Now you CAN go 16 hours with your 300ma led lights and only reach a 50% DOD state for cyclic use.

Sounds like your Arduino is only measuring things, and not controlling them. You need some sort of control. Current control without hacking up your panel is as simple as upgrading to a larger battery that can handle the current. But now you need VOLTAGE control to not exceed 14.7 volts as measured at the battery terminals. In a solar application, leaving it at 14.7 for the rest of the day until the sun goes down or dropping to a float voltage is a decision you'll want to make depending on how you want to handle it.

With no voltage control, I suppose the best you can do is fire off a klaxon-alarm warning you to pull the clamps.

[SunEagle]

$12? WTF that is 1/10 or retail of a EFlite AS3X. Something strange going on. I mean heck you cannot even build a 3-axis gyro that goes inside the RX for that.

No the orange rx for $12 is just a basic 6 channel receiver. The one with the stabilization is around $35. There are others that range in between with different capabilities but most are either Spectrum or other transmitters compatible.

Just google orangerx 3-axis and you will find it.

[thastinger]

Dude racing is another story. For racing you want the best batteries money can buy with the highest discharge C rate you can get. You would also want to cram every AH possible into the battery which will shorten battery life. Money is no object with racing, you buy the best money can buy. I would also assume the battery pack is replaced frequently as racing conditions would put a heavy toll on the batteries and capacity would degrade after 10 to 20 races.

Well, it is for drag racing so it only needs to go a couple of rounds and then I get some time in the pits to charge it back up. I did it for the weight savings of going from a 13.5Lb YB20 battery to a 4S4P A123 setup weighing in at 3 Lbs. It can start the motor 30 times before it needs to be recharged, the draw from the nitrous and fuel solenoids is the big power draw on it. It doesn't get alot of run time on it, probably 15 races a year or about 100 passes, it has held up much better than I expected, very impressed with the quality of these cells but its my understanding that A123 is going under.

[Sunking]

I currently use a knockoff Spectrum orange Rx which has yet to give me problems and only cost about $12 each.

$12? WTF that is 1/10 or retail of a EFlite AS3X. Something strange going on. I mean heck you cannot even build a 3-axis gyro that goes inside the RX for that.

[SunEagle]

No found it on Classifieds at RCG with the Programming USB Stick for $80. Have not installed it in the plane yet. Bought it because of wind in TX and can use the help. It is like the Apprentice SAFE RX with 3 axis stabilization with 2 modes of normal and 3D/Aerobatic modes. So far flew it with instructor on Buddy Box as it is a little above my skill level. Instructor can fly slow in semi-3D (knife edge, hanging on prop, tail down landing like a bird) Right now have to get use to the higher landing speeds. Have not set up the EXPO mode for aerobatics yet, just dual rates operating at Low for now. It is different, goes right where you point it like a bat out of he!! real fast.

No crashes yet.

Yeah prices are good and for the quality it is a good deal. Time will tell. Got two for the Apprentice and two for the EXTRA. Apprentice I get about 20 minutes hard flying, 30 minutes casual. Extra about 10 to 15 minutes.

I would imagine less time with the Extra since you are standing on your tail.

There is a new Orange Rx that has 3D stabilization. Cost is well below name brand types like the AS3X.

I currently use a knockoff Spectrum orange Rx which has yet to give me problems and only cost about $12 each.

[Sunking]

10-4 on the Extra 300. She looks fast. The spectrum AS3X is a nice 6 channel receiver. Did that come with the Extra 300?

No found it on Classifieds at RCG with the Programming USB Stick for $80. Have not installed it in the plane yet. Bought it because of wind in TX and can use the help. It is like the Apprentice SAFE RX with 3 axis stabilization with 2 modes of normal and 3D/Aerobatic modes. So far flew it with instructor on Buddy Box as it is a little above my skill level. Instructor can fly slow in semi-3D (knife edge, hanging on prop, tail down landing like a bird) Right now have to get use to the higher landing speeds. Have not set up the EXPO mode for aerobatics yet, just dual rates operating at Low for now. It is different, goes right where you point it like a bat out of he!! real fast.

No crashes yet.

I guess you found the batteries you were looking for at the site that sells Hyperion. Looks like the prices are pretty good for a US site.

Yeah prices are good and for the quality it is a good deal. Time will tell. Got two for the Apprentice and two for the EXTRA. Apprentice I get about 20 minutes hard flying, 30 minutes casual. Extra about 10 to 15 minutes.

[SunEagle]

Well I am new to RC chargers. I have the I-Charger 1010b and I can program all the set points to customize any battery. I assume yours can too from my research, but not certain. Its all about trade-offs, you cannot have your cake and eat it to. Want max performance, gotta sacrifice some some cycle life and mo money.

FWIW I found a pretty good LiPo by a company called Hyperion. They make LiPo for military and medical. Above average and prices are not bad. Should yield up around 1000 cycles. Best place I have found to get them at is All E RC. Check it out. You can get 45C discharge and 5C charge without degration. I use the 25/5 C models for my Park Flyers.

EDIT NOTE:

Did I tell you I bought my second plane? PKZ Extra 300 BNF. Even got my hands on a AS3X receiver.

10-4 on the Extra 300. She looks fast. The spectrum AS3X is a nice 6 channel receiver. Did that come with the Extra 300?

I guess you found the batteries you were looking for at the site that sells Hyperion. Looks like the prices are pretty good for a US site.

[Sunking]

I went back and checked all of my charge records and the majority of them had the same 12.3v end results. There was one time that I charged one in the field on the "fast" charge setup and that one got my battery to 12.6v. I didn't pay attention to it before but I will research to see if the "slow" charge setup has limited the voltage for some reason. Maybe to extend the battery life.

Well I am new to RC chargers. I have the I-Charger 1010b and I can program all the set points to customize any battery. I assume yours can too from my research, but not certain. Its all about trade-offs, you cannot have your cake and eat it to. Want max performance, gotta sacrifice some some cycle life and mo money.

FWIW I found a pretty good LiPo by a company called Hyperion. They make LiPo for military and medical. Above average and prices are not bad. Should yield up around 1000 cycles. Best place I have found to get them at is All E RC. Check it out. You can get 45C discharge and 5C charge without degration. I use the 25/5 C models for my Park Flyers.

EDIT NOTE:

Did I tell you I bought my second plane? PKZ Extra 300 BNF. Even got my hands on a AS3X receiver.