AGM or not AGM (1 Viewer)

[Msc01by]

Tons of info on battery choices in here but I’m hoping someone can give me a definitive answer.
Just did a dual battery setup and I have OEM alternator which I believe is 80 or 90a.

Does this alternator have enough to adequately keep both batteries charged or do I need to go to a bigger alternator?

 

[Malleus]

That depends entirely on how much you drain your batteries. And how fast you do it.

 

[Msc01by]

That depends entirely on how much you drain your batteries. And how fast you do it.

Currently just standard OE with the addition of a WARN 103251 VR EVO 8-S Electric 12V DC winch. However, like everyone else I’m sure I’ll be adding multiple items as I go.

 

[Malleus]

This is sort of like asking "can I use a pressure washer with my well?" The answer is maybe. If your pressure washer needs 8gpm, and your well flows at 6gpm, no. Maybe. You can flow at 6gpm, keep up with the pump for a couple of seconds and let it rest, and probably not see a problem. If your well flows at 4gpm, then no. If your well flows at 12gpm, all day long.

You need to add up how much you use to find how much you need. I've never met anyone who can look at an electrical system and judge, by eye, how much current draw there is.

For example, say you have one battery. You start the engine once or twice a day, several hours apart, and operate the engine for hours at a time in between. Since the alternator has sufficient current development to supply all the current the electrical system needs, and charge the battery, which has lost X in Y time, you'll be fine. Then compare that with the same truck, with a low battery and 20 starts in an hour, with 5 min run time in between. There's a high likelihood that the alternator won't have enough juice to recharge the battery before it fails to provide enough current to energize the solenoid and start the engine.

You may find someone who says. "I have done this with that". But you don't know what their needs are compared to their resources. You need to do the math and then you'll know.

 

[aclos3]

I have an X2 power (Northstar) AGM battery and I really love the capacity for running my fridge or DC to DC charging my LiFePO4 battery. I also still have the stock alternator and it seems to charge it just fine, but it does take a long time to bring it back up if the battery is low. So far this has not been a problem so I have not felt the need to upgrade the alternator and wiring to something larger.

I've read that AGM batteries like to be charged at a slightly higher voltage than a normal alternator puts out, but when I am home, my Landcruiser is parked in a garage and I plug it into a CTEK charger that has an AGM mode, so the battery regularly gets the full voltage it needs.

 

[USMCDocJ]

I run dual AGM Optima yellowtops in my 91 with a 90a alternator. I also have a lensun 100w solar panel on my hood, feeding the house battery. Never had any issues. If you want a parts breakdown of my entire system, let me know either here or in DM.

 

[jht3]

i'm running a single AGM, with no extra loads other than a cell phone. Stock alternator has been fine. Only issue is when I had malfunctioning headlights, which would turn themselves on overnight, draining the battery. Now that has been fixed and confirmed I have no parasitic draws, plugging my 10A Noco AGM charger in results in the green ready light turning on within a minute. This is after the truck sitting for 7+ days and only quick drives around town under 5mi. I also switched the interior overhead and door lamps to LED.

add a 2nd battery in, and I believe you'll have the same experience. Unless you have many items drawing on the batteries like alarms, fridges, inverters, etc. Add up the items you have installed or intend to install. A big inverter can easily put the hurt on the stock alternator if you have a huge load on it.

 

[LandLocked93]

Short answer, yes. But wouldn't attempt it w/o at least refreshing the brushes and confirming the bearings and regulator are good (easy to do).
I'm running dual D4 Interstate AGMs, 200aH each (cabin 24v bank).
Plus dual Interstate deep cycles, 108aH each (engine room).
No issues charging them all at one time (which is super rare) on the vintage OEM alt because of the way I can decide which battery(s) are being charged (outside the crank batt) at any given time.
Really boils down to how you design and use the system.

 

[Msc01by]

I appreciate all the feedback, and this forum in general. First Land Cruiser, and first 4 x 4 that will be used for actual off-road use.

Cheers

 

[Obrokoff]

Dual LTO will be better choice

 

[slow95z]

i went with a much bigger alt and very glad i did. i found when using the winch for long periods plus all the updated and modern stuff in the vehicle that the old one couldnt keep up.

 

[LandLocked93]

Dual LTO will be better choice

For the money, I'd trade for your double winch setup.
Cool. And more useful imo.

 

[landtank]

If you increase the draw on the electrical system it stands to reason you should also increase the ability of the electrical system.

Adding a second battery only extends the time to a dead situation.

The thing about winches is that the most inept moron at the controls can easily debilitate the most robust system known to man.

The first question I have is “how much wire or line do have on the winch?