Charging deep cycle battery

I run lots of devices while Parked. Even when I am not in the car, my metro mile (insurance mileage tracking) device is running GPS and cellular radio all the time. I think this help kill the battery. While Parked, I sometim es idle the engine just to charge the battery. A generator might be more e fficient and cheaper to replace due to wear and tear on the car engine.

Why is your Metromile radio running when the car is sitting still? There's no mileage being accumulated? I'm not familiar with such systems, but it seems odd that it would be running with the engine off.

I suggest you get some current drain numbers from the various boxes and a guess as to how many hours per day they were running solely on battery. Offhand, I don't think they're going to suck that much power. For example, todays GPS spends most of its time turned off. If the vehicle hasn't moved, it's going to lock in a few seconds, find that it hasn't moved, and turn off immediately. The "cellular radio" is probably a GPRS cellular data transceiver. Peak current can be as high as 2A, but then it doesn't transmit very often. The rest of the time, the rx draw is much less. It varies by the type of system and technology used: Since you haven't supplied any hardware specifics, I can't supply my usual guess(tm).

Unless you're driving an antique automobile, I don't think you have a generator. More likely an alternator, which does fairly well at charging a battery at low RPMs (i.e. idle).

I don't think you have to worry about wear and tear on the engine. One horesepower is 746 watts. At idle, your unspecified car is probably using about 5-10 horsepower to spin the wheels and heat the engine. That about 7kW. Your alternator might be charging your battery at

Unfortunately, you're probably correct about your method of operation killing the battery. Starter batteries are not really "deep cycle" batteries, which means you can drain them very far before they start to deteriorate. Drain too far down and recharge too fast, and you'll soon have a premature battery failure. The problem is that starter batteries don't make very good batteries for electronics. Instead of finding the ultimate starter battery, I suggest you run your electronics off a 2nd auxillary battery. A big AGM battery should do the trick and do well on deep discharges. Running the starter battery and the AGM battery in parallel is not a good idea, so a 2nd alternator or the existing alternator driving a DC-to-DC inverter which drives a charge controller, might be better.

I'm not convinced by this recurring sugestion of an AGM battery. They requi re lower charge voltage, which means much slower charging, and means it can 't simply be connected straight on to the existing system via a switch. 2 s ignificant drawbacks there. I don't see any reason to think the OP needs SL A, AFAICS they only offer disadvantages for this app.

OP needs to supply more detail about the problem before anyone can know whi ch of the various guesses offered is correct.

NT

The problem is simple, find a way to run my laptop for hours or days withou t running the car engine. Car engine charge well at freeway speed, but not so well at idle. The solution may or may not involve the car, although I am running the equipments in there.

How about a generator feeding supercaps? Running the generator in short bu rst.

how about plugging in solar panel into the system?

that's just a battery capacity issue

either its a very old vehicle or something isn't quite right

I'd look first at how you could reduce the load.

very low capacity & high price. Short bursts is an inefficient way to run an engine.

NT

Like police and fire vehicles, maybe you should install a larger alternator. Or you could always try a smaller diameter pully on the Alt to increase idle current.

Is your idle RPM set correctly?

Cheers

You can also run a generator with short bursts feeding the car battery.

If it really has to work for days without the car engine running, then I think a separate battery/generator set with automatic electric starter on the generator's engine. But not inside the garage, so a CO sensor would be good. All maybe controlled by a Raspberry Pi?

joe

Police and fire vehicles do use a larger alternator, but it's not because they need more amps. It's because they need a larger diameter alternator to be able to raise the charge current at idle.

A smaller pulley will slip at high RPM's. The pulley and belt on most vehicles is fairly well matched for "normal" service. Shrink the pulley diameter and my guess(tm) is a double pulley, toothed belt, or wider belt will be required.

100 amps. It will only be able to put out this 100 amps at about 1200 RPM or higher. At idle speeds of about 650 RPM it can only produce 50 amps or so. The RPM is the engine RPM, not the alternator RPM. At idle, there should be plenty of amps to balance the load of the eStuff, even if idle were RPM was low.

Most batteries that are called "gel cells" are now AGM. They have their limitations but methinks are a good match for the purpose. They do will in applications that require a steady low current draw, as opposed to an automobile, where the main draw is a huge burst of power starting the engine, and then nothing as the alternator both recharges the starting battery and runs the various low current loads.

If you read what I scribbled, you might notice that I suggested a separate charging system. You can't mix battery chemistry or battery size on the same charge controller by putting the batteries in parallel. If the OP is going to add a 2nd battery, I suggest he use either a completely separate charging system, or he builds a DC-to-DC converter, to raise the 12v (nominal) voltage of the existing alternator to a level where a conventional gel type battery charge controller will function.

Think of them as challenges.

You might actually be correct. The OP has declined to provide detailed system information, measurements, and proposed usage. I would hesitate to draw a conclusion until I had enough information to offer a workable solution or recommendation. For all we know now, the problem might be nothing more than a slipping fan belt, ancient battery, or defective alternator. I try to do the math first, then offer solutions.

Yep. Adding a 2nd battery and separate electrical system is most certainly more complex and more expensive than just repairing the vehicle in the first place. While I'm also guilty of offering advice here based on grossly insufficient evidence, I've always prefaced it on the assumption that what the OP offered is true and accurate, which I doubt.

Drivel: I was in the 2-way radio business for a few years, and had to deal with power sucking vibrator and dynamotor power supplies in commercial vehicles running 50 lb tube radios. Same with marine radios on vessels with chronically marginal electrical systems. Running a laptop and few electronic gadgets in an automobile is a trivial exercise by comparison.

they're certainly able to discharge to greater depth happily, so it's a cho ice between so many SLA amphours or much more extra main starting battery a mphours.

which is an excessive complication and expense unless it's really needed. A bigger main battery is way simpler, quicker & cheaper.

I think of them as rather large downsides

Quite, or the other prime suspect unnecessary power draw. SSDs & netbooks a ren't expensive.

though this time we can't

I've still got a vibrator PSU tucked away somewhere. 12v in, vibrator, tran sformer and perhaps synchronous rectifier vibrator contacts for around 240v out.

I'm tempted to resurrect vibrator supplies for one of my low cost projects. 12v in, self oscillating relay, transformer, 240 out. The big upside is it s suitability for the many constructors for whom semiconductor electronics are a step too far for their abilities. Regulation would be awful, but good enough for CFLs, smpsu chargers etc.

NT

That's an expensive lesson that needs to be learned the hard way. The problem of not being able to start the vehicle after an evenings session of partially draining the battery running the laptop by watching Netflix is the downside of your "simpler, quicker and cheaper" solution. Yes, a bigger battery will do the job, if you don't mind a battery that can only be minimally discharged. However, the big surprise of not being able to start the vehicle will probably make the OP reconsider that approach. I've been there in emergency vehicles, marine electronics, and mobile homes. If you look at the wiring of a recreational vehicle supplied by John DeArmond: You'll notice that the batteries are NOT in parallel when the engine is NOT running. Therefore, the "house load" only discharges the "house battery", and not the "chassis battery". With such an arrangement, you can kill the "house battery" watching NetFlix, and still be able to start the vehicle in the morning. It's a common problem in emergency vehicles and DC solar power systems , which are usually equipped with an LVD (low voltage disconnect).

I don't. Both problems can be solved. For example, to save copper and allow for higher power electric devices such as electric power steering, some vehicles are equipped with 36 or 42VDC electrical systems:

Netbooks are dead, replaced by Ultrabooks and Chromebooks.

Compared to a dual alternator charging system, a low power laptop is probably a better investment. However, even the lowest power laptop can still effectively kill the battery if left on and running full time. I just did that with a Raspberry Pi 2 plus weather station running on a big AGM battery when I stupidly forgot to reconnect the charger. Fortunately, I had an LVD on the battery so I didn't totally discharge it.

Yep. Garbage in, garbage out. Nothing in, nothing out.

For a time, I designed and sold plug in transistorized vibrators for Motorola, GE, and RCA land mobile radios. Genuine germanium power transistors. They weren't very reliable, and were easily blown up by starter induced transients on the vehicle electrical system, but were still better (and quieter) than vibrators, which required occasional contact cleaning. The nice part is both the vibrators and switchers produced an audible buzz that could be heard on every transmission. I was eventually able to recognize my products, and those of my competitors (for marketing purposes).

Ah nostalgia. I still remember cleaning the contacts and adjusting Delco-Remy automotive regulators: Unfortunately, most of my memories were from doing it while stuck in the rain, mud, or desert with a discharged battery. However, you're welcome to repeat about a 60 year learning curve in the name of saving a few pennies. hmmm... I don't think the sparking will pass FCC Part

There are various adages suggesting that we leave the dead undisturbed. Methinks that might be good advice for your proposed project.

Well, I'm not suggesting one sizes battery & load to result in likelihood of a breakdown. Of course a voltage monitor/disconnect is a good thing for such a setup.

If an 11w intel atom device eats 15w that's nearly an hour's use per Ah. The OP forgot to mention how many hours use wanted, or what battery capacity would fit the vehicle.

that's not the prime reason. And it's not for vehicle use. Like everything there are situations it's not so good for.

It's not intended to be used in North America.

biscuit tin & caps, then see if it's quietable from there. It may not be.

Regulator, that's fancy.

Probably. I might try it some day to see if it can be made workable, but not with high hopes.

NT