Anyone here has used alternator to charge battery?

[New Comer]

I have another question for you guys. After looking for ways to charge my battery, I found that the most practical way for me to charge my battery is through alternator of the car. I found information here on how to do that without draining the car battery. However, I want to know from those who have done it. What is your experience?

 

[WheelEstate USA]

I depend on solar totally, but I know lots who use the alternator to charge while driving.
It requires a fairly easy installation of a continous duty solenoid.

 

[WheelEstate USA]

I might add that driving, even for hours, will not kee batteries happy and healthy by itself. You still need another source, like solar or battery charger/shore power to completely finish the job.

 

[Reducto]

The alternator is good as a backup and supplement but it's not very good as a lone source unless you drive a lot and don't use much power. Batteries take a long time to charge fully.

I occasionally leave my van running to charge while I'm in the back but only when I'm out of other options. It's inefficient and not great for the engine.

 

[Tele]

I use a red arc isolater with dual batteries. I only have a minimal setup.

 

[LeeRevell]

I have read here and elsewhere that an idling car/van engine doesn't provide enough amps for good battery charging.  It takes the higher revs of actually driving to provide the power needed for efficient charging....?
I have just ordered a dual battery kit via Amazon, to install a second chassis battery in my E150.  I have just enough space on the driver's side for the second battery - Group 24 size.
Wish that were possible for my minivan, but it is much tighter under the hood.
Since the E150 goes extended times parked, I will use a plug-in or solar 'battery maintainer' to keep the batteries charged.  Have not installed the big solar panels yet.

 

[New Comer]

I have read here and elsewhere that an idling car/van engine doesn't provide enough amps for good battery charging.  It takes the higher revs of actually driving to provide the power needed for efficient charging....?
I have just ordered a dual battery kit via Amazon, to install a second chassis battery in my E150.  I have just enough space on the driver's side for the second battery - Group 24 size.
Wish that were possible for my minivan, but it is much tighter under the hood.
Since the E150 goes extended times parked, I will use a plug-in or solar 'battery maintainer' to keep the batteries charged.  Have not installed the big solar panels yet.

I also have an E-150. I am wondering if you have to draw a hole to have your cable come through the front of the car to inside the car. Also, I assume that you can use one kit to do this, without having to do connection with continous duty solenoid. Right? If that is true, this will be great. By the way, which kit did you buy. I have no knowledge about any of this. Thanks for the reply to my question.

 

[LeeRevell]

I also have an E-150. I am wondering if you have to draw a hole to have your cable come through the front of the car to inside the car. Thanks for the reply to my question.

My second battery is going into the engine bay, on the driver's side.  I have measured, and a Group 24 will just fit, with some minor rerouting of a wire bundle and relocation of the left horn.  There is already a shelf for the battery tray to sit on, with mounting holes.  I expect the Gen Three E150 (1988) had an option for a second battery here.  So with the switch and isolation unit mounted centrally, the cable run will be short.
I don't know if any of this applies to the Gen Four (1993 up).

 

[New Comer]

My second battery is going into the engine bay, on the driver's side.  I have measured, and a Group 24 will just fit, with some minor rerouting of a wire bundle and relocation of the left horn.  There is already a shelf for the battery tray to sit on, with mounting holes.  I expect the Gen Three E150 (1988) had an option for a second battery here.  So with the switch and isolation unit mounted centrally, the cable run will be short.
I don't know if any of this applies to the Gen Four (1993 up).

I guess, I have a Gen Four (1996) E-150. When you say that you have a second battery, do you mean that you have second battery for the car or for your electrical needs inside the van. Please forgive me if I seem to have no clue for what you are talking about. I am quite new to this.

 

[WheelEstate USA]

The solenoid method might be cheaper and just as easy.
I think that group 24 is gonna take a beating, especially without a way to top off after driving.
The alternater takes a toll too.

For my part, I want each system to stand alone for several reasons, including simplicity...another reason I'm glad we got out of the RV.

 

[LeeRevell]

I guess, I have a Gen Four (1996) E-150. When you say that you have a second battery, do you mean that you have second battery for the car or for your electrical needs inside the van. Please forgive me if I seem to have no clue for what you are talking about. I am quite new to this.

This is a second chassis battery.  The house batteries (12V marine type) are in the back of the living area - a totally separate system.  This second battery will provide a backup if/when the primary fails to start the van.  It can power certain accessories to prevent draining down the primary battery.  I like the idea of redundency when possible.
I am also strongly considering installing a second alternator where the AC compressor should be (currently missing and replaced with a simple pulley).

 

[SoulRaven]

I have read here and elsewhere that an idling car/van engine doesn't provide enough amps for good battery charging.  It takes the higher revs of actually driving to provide the power needed for efficient charging....?

I have always thought that an alternator charges pretty efficiently even at an idle. Now, when cars used generators (how long ago was that????) it was true that to get the batteries charged good you had to drive the car or set it up on high idle to charge the battery at a good rate. Alternators are just that, an alternator. They use alternating current and convert that to direct current with diodes, which gives double the charge rate than just a generator. I guess it is the difference between ac and dc operation of electric. An alternator is more efficient than a one way generator. That's the reason we have ac in our houses instead of dc.

I know that when I have had to jump start my car that has an alternator, it recovers very quickly just idling. After a couple minutes of just idling after jumping it, I can shut it down and restart it 5 or 6 times with no problem. So I would think that it would charge up a spare battery pretty quickly the same way.

 

[SternWake]

An alternator, wired with thick copper between alternator and house battery, can be an excellent bulk charger.

It can get a 50% charged battery to 80% in an hour or less.

IF the voltage regulator is allowing voltages in the mid 14 volts range to be held for that duration

To get from 80% to 100%, requires about 4 more hours, no matter how powerful the charging source might be

If the battery is not regularly brought upto 100%, it will be an unhappy battery.

How much any vehicles alternator is going to be able to provide at idle speed, vs higher rpms is going to be HIGHLY platform specific.

Some vehicles might be able to make 80 amps at idle speed when hot, others might struggle to make 10.

What my system makes at idle, og going to be a lot different from another vehicle.

Get a Clamp on DC ammeter. Very enlightening tool.

 

[ascii_man]

Alternators do not produce rated output at idle. An Honda Accord would actually run down the battery if you ran the headlights, defroster, blower fan, and radio too long while sitting in traffic due to a snowstorm.

Police cars usually have a high-output alternator instead of, or in addition to the stock alternator so they can power all their gear while idling.

Here is some discussion: https://www.dcpowerinc.com/articles/truth-about-idle

 

[SternWake]

Good link.

 

[flying kurbmaster]

on my poptop minivan the alternator charges the house battery it is high output alternator, seems to work ok, I power a comprssor fridge and lights, I usually shut the fridge off at night, I keep those gel packs in the freezer they freeze during the driving and keep the fridge cool at night when shut off, I use this vehicle for road trips so not lived in, in my Stepvan I have a switch that I can either charge my house battery on the alternator or not, I also have a 40 watt solar panel that seems to keep the battery charged, I have used this for two years now, I usually recharge the house battery every three/four months with shore power if I get a chance. With the switch I can also boost my engine battery if need be or use the engine battery for house if I had to. I don't run a fridge when parked, I use ice, I sometimes run the fridge while driving. I run a tv, vcr, charge my cell and computer, led lights, heater fan and extractor fan when needed

 

[ascii_man]

Another consideration that I rarely see addressed is making sure that the house battery doesn't deep-cycle your SLI (starting, lighting, ignition) battery when both are connected to the alternator.

I haven't done deep analysis, but you could possibly achieve this by using deliberately undersized wiring between the alternator and house battery: not so small as to be dangerous, but deliberately creating a voltage drop at high currents. Of course, this also defeats the purpose of having a high-output alternator.

So perhaps the best option is to have two isolators (need to read up on which is best: relay, solid-state relay, solenoid, etc., as some have a significant continuous power drop): one between the SLI's positive terminal and the vehicle and another between the house battery and the vehicle. I'd need to think a little more about how to handle the switchover gracefully (probably a large capacitor).

 

[Optimistic Paranoid]

Another consideration that I rarely see addressed is making sure that the house battery doesn't deep-cycle your SLI (starting, lighting, ignition) battery when both are connected to the alternator.

Can't happen if the engine is running.  Remember, voltage is pressure.  Electricity always flows from the higher voltage to the lower. With the alternator putting 14 or more volts of pressure on the system, current CAN'T flow out of the SLI battery against the greater pressure the alternator is providing.

Regards
John

 

[ascii_man]

Can't happen if the engine is running.  Remember, voltage is pressure.  Electricity always flows from the higher voltage to the lower. With the alternator putting 14 or more volts of pressure on the system, current CAN'T flow out of the SLI battery against the greater pressure the alternator is providing.

Regards
John

You are correct for an alternator with infinite output and zero output resistance https://en.wikipedia.org/wiki/Thévenin's_theorem. If you find one, send a link because I'll buy a dozen!

But, back in the real world, if you connect a SLI battery, an alternator, and a huge discharged battery to a common terminal, If you have both battery wires connected to a common point (the alternator output terminal), the current will take the path of least resistance from the high voltage to the lower voltage.

The good news is that the difference between a 100% charged battery (12.7 V) and a 0% charged (10.5 V) is only 2.2 V. So assuming a 100 A alternator, 22 mOhms in your house battery lead would be enough (actually, 22 mOhms total between the SLI battery and house battery terminal). Keeping above 50% depth of discharge reduces the total resistance to only 6.4 mOhms. But that's actually pretty high for a battery lead.

 

[ascii_man]

Here's a discussion about engineering considerations on battery wires at GM in the 1960's: http://www.madelectrical.com/electricaltech/chevymain1.shtml