Charging batteries with alternator?

[Astrosport]

I'm trying to charge my starting battery and 2 golf cart batteries.
How do I get my alternator to output a higher voltage to charge the batterys better?
My alternator output is only 13.7
A solar guy told me you need 14.8 volts and bigger guage wire to charge your batteries good.
Take a long time to charge with the lower voltage output and may not top out

[Lumpy]

I don't think you can.

Alternator is meant to only top off a battery that is just slightly discharged (from starting). Buy a little battery charger at WallyWorld or wherever. I've used mine more than I ever thought I would. Not expensive. They've got computers in them so even Maher can make them work.


Lump

[97cargocrawler]

I monitor my charging voltage. Seems when i start the van the voltage is above 14.5v for a while and slowly comes down to maybe 13.5v. I thought these vans have a variable voltage regulator? Anyway, I charge my start battery and FOUR golf cart batteries with my alternator. Yeah I have solar as well. The cart batteries are only charging when the van is running through an SSR. Higher voltage often gives a faster charge but can shorten the lifespan. Anything over nominal voltage will charge a battery. Slightly above nominal is like trickle charge and does it better but takes longer. You shouldn't have any issues. It's how they charge on boats. Good enough for a boat..good enough for my van.

I should note that my alternator is a custom 300A unit from DCPOWER.

[Astrosport]

Could I benefit from a high output alternator considering my vehicle is stock except for now I'm using the alternator to charge the golf batteries?

[Lumpy]

Perhaps let's define what you mean by "charging my batteries". Are they dead? Are they in use normally and just discharged a bit? Are they in use and discharged a LOT etc.

I guess I pictured you trying to charge discharged batteries with your parked, running van.


Lump

[97cargocrawler]

If the batteries are seriously discharged they will draw a lot of current while charging. Stock alternators are typically designed to run the stock gear and not much else. I would upgrade the alternator and the wiring. I don't think you will need a 300A but perhaps upgrade to like a 120A. 300A alts cost like $600 or more. I suggest running at the very least 4ga. wire, preferably 1/0. The further the batteries are away from the alt the larger diameter wire you will require.

Do you already have something setup or????

[Sailing_Faith]

The charging voltage is a very poor indicator of what is happening with the charge rate of your batteries.

Typically, the voltage one would expect to see in a typical charging system is about what you are seeing,,, 13.8vdc is fine.

What are your loads? What are you doing? What are the golf cart batteries being used to power...

Tell me more.

[Lumpy]

I'm pretty sure a higher amp capacity alternator wouldn't be a factor in charging. Your typical solar array is capable of something like 17 amps. Typical tricle charger is ~2A. Typical "fast charge" on a battery charger is 25A. All are quite a bit less than an automobile alternator.

If you squeeze scorpion blood into the battery cells, they won't recharge any faster. But I'll buy you a burrito.


Lump

[97cargocrawler]

I'm pretty sure a higher amp capacity alternator wouldn't be a factor in charging. Your typical solar array is capable of something like 17 amps. Typical tricle charger is ~2A. Typical "fast charge" on a battery charger is 25A. All are quite a bit less than an automobile alternator.

If you squeeze scorpion blood into the battery cells, they won't recharge any faster. But I'll buy you a burrito.


Lump

If you're pushing the limits of the alternator running stock onboard gear and then add the huge initial draw of some highly discharged batteries....you don't think that could max out the alternators current capacity? Maybe not but I'd personally not want to find out when I'm parked in the middle of no mans land. Best to have some overhead.

[Lumpy]

If you're pushing the limits of the alternator running stock onboard gear and then add the huge initial draw of some highly discharged batteries....you don't think that could max out the alternators current capacity?...

No, I don't think it will. If anything you'd probably want current limiting. That's exactly what a battery charger does. It doesn't just pump in all the amps it can. It limits the amount of current that can be drawn from the source (the charger) so that the battery being charged doesn't overheat. That's why car alternators don't make good chargers for moderate to severely discharged batteries (anything below about 9v).

Battery charger = Current regulated device, like TIG welder
Car Alternator = Voltage regulated device, like MIG welder

Our high amperage capable alternators are capable of powering MORE loads, but all at that same nominal 12 volts. Each added load, of course, adds more current draw.

Car batteries are there to start the car. After that initial current draw of the starter motor, the alternator takes over and runs all the loads and tops off the battery. That's nothing new. But run that battery down far enough and either the alt won't recharge it OR it will damage the cells and give it a surface charge that will draw off so fast that it makes the charge pretty useless.

Now that scorpion thing, on the other hand...


Lump

[chevymaher]

If you look into it. I don't think it is so much which you are using to charge. Either a charger or the alternator do fine.

But it is what you are charging. Batteries have a chemical reaction that store the charge. And this generally takes over 24 hours to complete, if it is extremely low. So an alternator would charge fine if you were driving for the next 24 hours. Chargers don't do great either of you just leave them on for 20 minutes.

[Astrosport]

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[Astrosport]

Perhaps let's define what you mean by "charging my batteries". Are they dead? Are they in use normally and just discharged a bit? Are they in use and discharged a LOT etc.

I guess I pictured you trying to charge discharged batteries with your parked, running van.


Lump

Good question , l don't know because I've never used my equipment much for me to know how much my batteries are going to be drained.
I have completly stock vehicle except 2 golf cart batteries 220amphrs available and a battery isolater,
Lots of l.e.d lights about 7 amps
I have a fridge that draws about 3.5 amps and that's what I'm worried about because the only way my batteries get charged right now is my alternator.
I drive about a hour a day.
I think you guys already answered my question , I think a alternator with slightly more amp output and plus a solar panel that should do it , plus I'll keep a battery charger near by so I can give it a little help maybe once every couple of weeks.
Can I be using/powering lights, fridge stereo and tv while the battery charger is charging?
If so I'll probably hard wire the battery charger to the golf batterys so I can just pull up , plug in and charge

[Lumpy]

I think current technology solar panels are the greatest thing in the world to charge batteries. No longer are they very low output for huge size, they put out tons of charging and even operating power under nearly any lighting condition. The panel on our RV provides 17+v at up to 17A from dawn to dusk.

Alternators as chargers...Consider fire trucks and ambulances. Very high output alternator capability. Heavy current draw (sirens, lights, radios, other equipment). Driven and engine continuously running for at least an hour at a time (run at high idle when on scene). But when they get back to the barn they plug in a trickle charger.

Running accessories while charging...Gazillions of radio stations do exactly that. Every automobile does exactly that. Modern battery chargers are "clean" without AC or square wave noise that might bother sensitive equipment. And modern "sensitive equipment" isn't that sensitive. There's probably not a TV, radio or other appliance that doesn't have it's own internal voltage regulator which converts the incoming voltage to whatever is appropriate and smoothes out any ripple or spikes.


Lump

[JaxSPL]

Do not try charging dead batteries with the alternator. It'll cause a shorter life span of the alternator
A higher output alternator (with good batteries) will do good. Use at least 1/0 wiring to go from battery (or alternator) under the hood to the batteries in the back of the van (where I assume the golf cart batteries are). Make the ground wire, also 1/0, as short as possible, but try mounting it to the frame. Don't use self tape screws to mount the ground wire. Drill a hole, clean the area to get good bare metal, use a bolt and nut, with a lock washer, to tighten the wire.
Also,even though things are stock, I recommend doing the Big 3 upgrade. It's pretty much the first things I do on a new (to me) vehicle, or one that comes to me for an install of some type. Plenty of info about the Big 3 upgrade on the internet.
I've said this a couple times in the past. You might be able to install an AD-244 alternator from one of the newer Chevy trucks. They come at higher outputs than the CS-130 and CS-130d alternators that are in these vans. I've seen them up to 175amps. You will, more than likely, need a belt that is aprox 1" longer than the one on the Astro. The AD-244 alternators also run cooler than the stock alternators for these vans.

[Meterpig]

The charging circuit from the alternator, at least on my van, has one customer and that is the battery. All electronics run off the battery full time. Of course the battery can fail to hold a charge, but still allow voltage to pass through. When this happens, it can look like dimming headlights at idle.

You can charge a battery faster with higher amperage which can look like higher voltage on the voltmeter. I have a little powerwheels battery that can be charged at a faster rate. I usually leave it on at 2 amps or the battery gets pretty warm, boils..etc. Remember the 80/20 rule. A battery can in theory accept higher amperage up to 80%. The last 20% is when it needs a more optimal charging amperage. I don't know if our vans do this or not. I am guessing not given that the battery is a technology from 1880.

To the OP's question, you need more amperage which will translate into higher voltage on the meter in theory. If you alternator is producing a true 100-120 amps at 1000rpms, that should be more than enough to charge a few batteries from a 50% charge. The real issue is how you have the wired together. Are they isolated? Is the current being sent only one direction under charge? There are a bunch of write ups out there how to do this. The bottom line is...you need a larger alternator. There is no free lunch. It's either a $600 alternator or a $900 generator.

On a side note, my experience is a factory AC delco will produce higher voltage all the time. My aftermarket 120amp alternator from the parts store fluctuated much better with load. After a long drive with no load, the voltage would drop to an even 13.5. The Declo would run 14.2 no matter what. Which..I think...fried my Interstate and costco battery nicely. Warranties are great.

[Astrosport]

The charging circuit from the alternator, at least on my van, has one customer and that is the battery. All electronics run off the battery full time. Of course the battery can fail to hold a charge, but still allow voltage to pass through. When this happens, it can look like dimming headlights at idle.

You can charge a battery faster with higher amperage which can look like higher voltage on the voltmeter. I have a little powerwheels battery that can be charged at a faster rate. I usually leave it on at 2 amps or the battery gets pretty warm, boils..etc. Remember the 80/20 rule. A battery can in theory accept higher amperage up to 80%. The last 20% is when it needs a more optimal charging amperage. I don't know if our vans do this or not. I am guessing not given that the battery is a technology from 1880.

To the OP's question, you need more amperage which will translate into higher voltage on the meter in theory. If you alternator is producing a true 100-120 amps at 1000rpms, that should be more than enough to charge a few batteries from a 50% charge. The real issue is how you have the wired together. Are they isolated? Is the current being sent only one direction under charge? There are a bunch of write ups out there how to do this. The bottom line is...you need a larger alternator. There is no free lunch. It's either a $600 alternator or a $900 generator.

On a side note, my experience is a factory AC delco will produce higher voltage all the time. My aftermarket 120amp alternator from the parts store fluctuated much better with load. After a long drive with no load, the voltage would drop to an even 13.5. The Declo would run 14.2 no matter what. Which..I think...fried my Interstate and costco battery nicely. Warranties are great.

You contradicted yourself , You typed that my stock alternator would be more than enough to charge a few batteries from 50% but then you typed I need a bigger alternator .
I'm glad you brought up your Delco cooking the batterys because it was constantly running 14.2 volts , because it made me realize I left something out of my first post .
I typed that a solar guy told me that I needed 14.8 volts to get the batterys to charge good , I left out that the charge controller would only apply the 14.8 volts for a certain amount of time and then back off.
If the charge controller wasn't on this guys solar system he probably would have cooked his batteries too.

[Lumpy]

The charging circuit from the alternator, at least on my van, has one customer and that is the battery. All electronics run off the battery full time...

...To the OP's question, you need more amperage which will translate into higher voltage on the meter in theory. If you alternator is producing a true 100-120 amps at 1000rpms, that should be more than enough to charge a few batteries from a 50% charge...

Oh my!

Yours would be the only non-electric automobile in existance that runs it's electronics from the battery and not the alternator. It's not possible to wire your system so that the alt charges the battery (only). And if your van ran off the battery (only) it wouldn't run for more than a few minutes.


2nd point is confusing and just plain wrong. Amperage doesn't "translate into voltage". Alternators don't "produce" amperage. They are capable of delivering amperage up to a certain point, based on what the load draws. Just like your house current. If you have a 15A house circuit, and plug in a light bulb that draws 1A, the load (bulb) will only draw 1A from the wall. If a battery had such a draw that it was causing an alternator to output 100 amps, it would be essentially welding the internals of the battery together (or exploding them). Every battery and alternator manufacturer in the world will tell you that alternators don't charge dead batteries and that batteries at only 50% of their charge are nearly or essentially dead or at least severely damaged.


High output alternators - Are for when you run a lot of accessories while the engine is on.

High capacity or multiple batteries - Are for when you run a lot of accessories while the engine is off.

That's RV and big truck electrical 101.

Sorry if I'm being a PITA about this. But I just hear the same old very incorrect assumptions being posted again and again. There's wrong and there's right. It's not a matter of opinion.


Lump

[Meterpig]

We found your passion lump. Translate to me means what the average person sees on the dash. We can debate what a "dead" battery will draw amperage wise. Funny that people jump "dead" batteries all the time and drive away and then the battery charges. What is dead in your mind lump?

How would one charge batteries at 11.5 volts if not with an alternator? Magic?
You wanna chat about bad internet info? I once googled running a wire straight from the alt to the battery. Whoah boy...all the dire predictions of electrical melt down out there.

[Meterpig]

Wow...glad I could be of help to you. Yes..I did say both. You can keep your stock and wait a looooong time to charge your additional batteries or buy an upgrade and wait less time with the appropriate hardware. But... Sounds like you got it all figured out anyway. Good luck!

The charging circuit from the alternator, at least on my van, has one customer and that is the battery. All electronics run off the battery full time. Of course the battery can fail to hold a charge, but still allow voltage to pass through. When this happens, it can look like dimming headlights at idle.

You can charge a battery faster with higher amperage which can look like higher voltage on the voltmeter. I have a little powerwheels battery that can be charged at a faster rate. I usually leave it on at 2 amps or the battery gets pretty warm, boils..etc. Remember the 80/20 rule. A battery can in theory accept higher amperage up to 80%. The last 20% is when it needs a more optimal charging amperage. I don't know if our vans do this or not. I am guessing not given that the battery is a technology from 1880.

To the OP's question, you need more amperage which will translate into higher voltage on the meter in theory. If you alternator is producing a true 100-120 amps at 1000rpms, that should be more than enough to charge a few batteries from a 50% charge. The real issue is how you have the wired together. Are they isolated? Is the current being sent only one direction under charge? There are a bunch of write ups out there how to do this. The bottom line is...you need a larger alternator. There is no free lunch. It's either a $600 alternator or a $900 generator.

On a side note, my experience is a factory AC delco will produce higher voltage all the time. My aftermarket 120amp alternator from the parts store fluctuated much better with load. After a long drive with no load, the voltage would drop to an even 13.5. The Declo would run 14.2 no matter what. Which..I think...fried my Interstate and costco battery nicely. Warranties are great.

You contradicted yourself , You typed that my stock alternator would be more than enough to charge a few batteries from 50% but then you typed I need a bigger alternator .
I'm glad you brought up your Delco cooking the batterys because it was constantly running 14.2 volts , because it made me realize I left something out of my first post .
I typed that a solar guy told me that I needed 14.8 volts to get the batterys to charge good , I left out that the charge controller would only apply the 14.8 volts for a certain amount of time and then back off.
If the charge controller wasn't on this guys solar system he probably would have cooked his batteries too.