Has anybody modified their charging system?

[BrooklynBay]

My stock 7750 3G alternator in my 1995 van is rated at 95 amps which is low compared to more modern vehicles which use 130 to 160 amp alternators. I've looked into 350 to 370 amp alternators but they cost almost $500 which is a huge investment in a 25 year old vehicle.

The reason why I'm doing this is because I've recently installed a 2,500 watt true sine wave inverter which runs a 12,000 BTU air conditioner. The system puts a load on the electrical system until the voltage drops to a low enough level to shut down the low voltage safety in the inverter. It doesn't happen right away but it always happens. Here are my options which I've thought about to boost the efficiency of the stock low current system:

1. Install an external adjustable Chrysler voltage regulator to boost the voltage during the time the compressor is off. The fan in the A/C doesn't place a huge load on the electrical system.

2. Run a 4 gauge wire from the positive post of the alternator to the battery or the starter relay on the fender wall. The voltage at the alternator is always a half a volt higher than what the battery reads so the thin factory wiring isn't sufficient.

3. This is the tricky part. I thought about adding a DC to DC boost converter to supply a steady 15 volts to the internal voltage regulator which is powering the rotor. As the voltage is slowly dropping due to a load, the rotor will still get the same or higher voltage to compensate. It won't get the same amperage but it might work since it will get a steady regulated voltage. The internal regulator isn't capable of boosting voltage. It only acts like a voltage controlled switch just like a linear regulator. The DC to DC PWM switching power supply is what is used in computers. Here's a link to that part: https://www.amazon.com/gp/product/B01KF56FM6/ref=ox_sc_act_title_2?smid=A32CQEYJ1PIFSX&psc=1

4. Install a smaller 48 mm 6 groove pulley to replace the stock 58 mm pulley. This will enable the alternator to turn faster at idle, and provide a little more power while sitting in traffic.

I don't think that the external adjustable regulator will work with this part but it might be possible. Has anybody on the forum tinkered with any of these things? I have a 4 gauge battery cable with the external voltage regulator modification in my 1988 van with a high current alternator so I know that those parts work. I haven't experimented with the DC to DC boost converter. Let's hear some of your thoughts, opinions, and advice.

 

[imp]

@BrooklynBay You did not say (unless I missed it) what current level you are expecting to drag out of the alternator. 12000 btu is roughly equivalent to 3000 watts (btu are measured per hour, but no matter, 3000 watts for an hour). 3000 watts delivered by a 12 volt system works out to pulling 250 amps to do it. 250 amps is typical of a fairly heavy arc-welding current; welding cables handling such current are FAR bigger than #4, more like the diameter of my little finger, perhaps 1-O or even 2-O (two-ought). Also important is the Distance. Length needed to carry the current without incurring much cable voltage drop.

Beyond knowing more about WTH you're doing, there's just a few thoughts. imp

 

[gmanpaint]

12k btu is a lot to ask on a single battery setup. But a 130 amp alternator can work with 4 ga, except for the inverter.

Dual group 31 agm batteries, with one being a house battery only, DC to DC converter, and 140 amp smart charge switch, with 2-0 wire from secondary battery to 3k steady, 6k startup inverter. 200w solar with mptt charger for when engine off, and finally a 20 amp shore charger for 10amp per bank. That's 3 ways to charge those batteries that are going to be drained fairly quick with that size ac unit.

Phew.... that's a lot of stuff for a 12k btu ac.

If you used two good 6 volt golf cart batteries, you can get a higher amp hour rating out of them, 4 would be even better.

 

[BrooklynBay]

My battery is a large AGM platinum series from Sears which is really a relabeled Odyssey, and was discontinued a few years ago. The inverter has 2 gauge wire which is 8 feet long. The air conditioner might draw around 8 or more amps at maximum. I wanted to get a 5,000 BTU portable A/C but every place I've looked indicates that it's discontinued. I already had the 12K BTU so this is what I'm using. I have a 10K BTU which seems to be a little more powerful but isn't as energy efficient. It requires about 10 amps at 1,000 watts so that's why I was using the 12K BTU. It doesn't seem to get as cold but it's more efficient, and is only cooling a small van (not a large room).

According to a review, one person said that he was able to run a 14K BTU on the same inverter without any difficulty. He didn't say what kind of alternator or batteries he has.

 

[BrooklynBay]

When I mentioned the amp draw & wattage of the air conditioners, it's on 120 volts A/C at the output of the inverter, not the current draw at the DC battery cables.

 

[BrooklynBay]

I forgot to say that the 4 gauge cable from the battery to the alternator is 5 feet.

 

[BKennedy]

Are the Explorer alternators and the Aerostar alternators interchangeable? If so, I have been running a 130 amp alternator in Explorer that came with a 95 amp unit for several years with no issues.

Or, how about something like this.....

 

[CDW6212R]

I'd start with the alternator, the 3G series was one of the most varied in sizes and outputs. There should be some model which can be easily installed which has 130+ amps in stock condition. I have a stock 95 Taurus 130 amp unit in my 91 Lincoln, which came with a 1G 100 amp(had to cut the one ear down a little).

The 3G has a lot of aftermarket support, there are different internal guts that can upgrade most of them. I'd do that first, upgrade the 3G alternator, and then upgrade the wiring with the rest of the system.

It sounds like you will require one or more extra batteries too. It's a shame the FePo4 batteries haven't dropped enough in price yet. Those all run over $500 for a typical car capable size. They are slowly being made in versions that will bolt into stock trays, and most are safe for use with OEM alternators. Hopefully those prices keep creeping down, as common lead batteries are still going up.

 

[BrooklynBay]

I emailed one guy selling high current alternators on EBay. He has 130 amp to 350 amp 3G models, and claims that I need a 350 or 370 amp version. That model has a modified case which is larger than the stock 3G, and I don't know if it will fit in the cramped engine compartment. The price on an over sized 350 amp is almost 3 times the price of a 300 amp with a standard size case. The same seller has that one but he recommends the larger one. I don't know if I really need it or he just wants to make 3 times the price.

 

[CDW6212R]

I'd suggest finding an alternator shop that has more choices, anything in the 150-250 amp range should cost no more than about $1 per amp. Skip any special alternator housing, it's not needed unless you truly do need wild amps like 300+ etc.

I've got a 170amp 4G model and a 200amp from the same company, about $175 each years ago when I tried that company. I bought the latest 250amp from Summit a while ago, a 4G also, and it was about $230 on sale.

The 3G alternator may be 20+ years old tech, but the shops I've spoken with loved them. There should be something you can work out that will gain you a lot of current, in the same space, for a modest cost.

 

[BrooklynBay]

This is the 300 amp version: 300 AMP 7750 Alternator Ford Mazda Mercury High Output Performance HD NEW USA | eBay. The seller from this 300 amp version wanted me to buy the 350 over sized version.

Getting back to the DC to DC boost converter, could that regulate the rotor voltage to provide sufficient current out of my stock alternator?

 

[CDW6212R]

If that will fit your Aerostar, and it'll last a long while, that would be a great deal for under $200.

 

[BrooklynBay]

EBay has a 10% back in EBay bucks offer so I took a chance & ordered it. The seller didn't recommend it since he felt that the 350 amp alternator would be the correct one. I hope that it's good. My stock alternator is 95 amps, and this alternator is 300 amps so it's like running 3 alternators. This alternator is new, and not rebuilt or remanufactured.

 

[imp]

12k btu is a lot to ask on a single battery setup. But a 130 amp alternator can work with 4 ga, except for the inverter.

Dual agm batteries with one being a house battery only, DC to DC converter, and 140 amp smart charge switch, with 2-0 wire from secondary battery to 3k steady, 6k startup inverter. 200w solar with mptt charger for when engine off, and finally a 20 amp shore charger for 10amp per bank. That's 3 ways to charge those batteries that are going to be drained fairly quick with that size ac unit.

Phew.... that's a lot of stuff for a 12k btu ac.

If you used two good 6 volt golf cart batteries, you can get a higher amp hour rating out of them, 4 would be even better.

@gmanpaint
And connect them together using BIG heavy cable. Now, what about the typical lead-acid battery connectors? What type can handle sustained boo-coo high current? The square lead type burn brown around the post.....I'm thinking the area available on a typical battery post determines the long-term heavy-current capability. Reason is, something they call "current density", current per square inch of contact area. Getting close to space-age needs here/...., imp

 

[imp]

My battery is a large AGM platinum series from Sears which is really a relabeled Odyssey, and was discontinued a few years ago. The inverter has 2 gauge wire which is 8 feet long. The air conditioner might draw around 8 or more amps at maximum. I wanted to get a 5,000 BTU portable A/C but every place I've looked indicates that it's discontinued. I already had the 12K BTU so this is what I'm using. I have a 10K BTU which seems to be a little more powerful but isn't as energy efficient. It requires about 10 amps at 1,000 watts so that's why I was using the 12K BTU. It doesn't seem to get as cold but it's more efficient, and is only cooling a small van (not a large room).

According to a review, one person said that he was able to run a 14K BTU on the same inverter without any difficulty. He didn't say what kind of alternator or batteries he has.

@BrooklynBay
8 feet of copper wire size 2/0 has a resistance of 0.0006 Ohms. Thus, 250 amps passing through it will drop (lose) about 0.2 volts, double that because there are two current paths (if both 2/0, if engine block, neglect that drop). As I said, LENGTH is very important.

You might want to convert the comparisons between the A-C unit at 120 volts usage and the alternator feed at say 14 volts to Watts. Easy to work with Watts Produced = Watts Delivered minus Watts lost in getting the juice there.

A.C. Watts = Volts X Amps, as is D.C. Watts. The A.C. is "fudged" for you already, so that Watts, or heating effect is the same for A.C. and D.C. The TRUE VOLTAGE using 120 volts A.C. is actually 164 volts, which gives the same WATTAGE as 120 Volts D.C.

All the world's measuring meters for A.C. already take that into consideration, indicating 120 volts when the Peak of the sine wave is actually 164. This simple fact eludes a lot of folks. imp

 

[BrooklynBay]

The 2 gauge cables are connected directly to the bolts on the battery terminals. The inverter came with 2 foot cables. I had to purchase 6 foot cables separately, so I combined them to make 8 foot cables.

 

[imp]

The 2 gauge cables are connected directly to the bolts on the battery terminals. The inverter came with 2 foot cables. I had to purchase 6 foot cables separately, so I combined them to make 8 foot cables.

@BrooklynBay
Reality underhood is that most high-current stuff is fairly short-route, couple of feet. #2 should be no problem at all, if connections are solid of course. imp

 

[BrooklynBay]

The 300 amp alternator came in the mail today. I want to upgrade the main cable on the alternator to 4 gauge, and install this alternator. I hope that it will solve the low current issue to keep the battery charged while using the inverter.

 

[gmanpaint]

Intrested to see how this turns out for you.

I have a dual 210 Ah agm battery setup on my trailer. I currently run a 140 amp smart charge switch on the tow rig that charges them while driving. This is just a bit more than a trickle charge tho. Works fine on the road for hours at a time. But I want something more than that.

Plan is to install a 40 amp 500 watt DC to DC converter near those batteries on the trailer. This unit will put out a true 40 amp charge, running off a simple 4 awg cable. The distance is a bit long, and more than likely I will use 2awg.

Now what's cool about these converters, is they automatically adjust for power fluctuations with surge or loss in that line. They connect to both the vehicle battery, and the alternator. They only engage to the house batteries when the ignition is on, and a charge is being sent out from the alternator. This way, the starting battery won't ever be drained. 40 amps of charging is plenty to keep all 3 batteries charged for my needs.

I watched a video where a 15k btu ac unit was ran off an inverter, and battery power only. The ac drained both high dollar lithium 200 ah batteries in 1.5 hours. For agm, they lasted half that.

They used a 2000w pure sine xantrax (4k start) which is considered top of the line. To get the ac started, they started the fan only first for 2 minutes, then ac on low, and it barely kicked the compressor on. This is why I said a 6000w startup inverter.

A 5k btu ac unit would be much better as they can draw as little as 4 amps.

Either way, I hope your wants for your application works out. I'm just shooting the breeze here, talking random stuff. Lol

 

[BrooklynBay]

Was the DC to DC converter wired in the same way as a diode style isolator to charge a second battery?