Agm battery charging..

I have had a Duracell AGM battery from Batteries Plus in my bay boat for 8 years and it still starts reliably. Charges on a MinnKota digital precision charger with interstate trolling motors. I have to replace the interstate flooded batteries every 3 years. My 2011 Tundra has been running in an X2 from Batteries Plus for 6 years. I had it tested this last weekend, still at 870 cranking amps, the battery is still in good condition. I have not done any mods to my truck, just put it in. This AGM has easily out lasted the other 2 Toyota flooded batteries. Tundra has 230,000 miles. I have a topper on the back finished out for camping. Run my led lights and fan from the single battery under the hood. Never had an issue starting on this battery.

 

I'm about to get the same battery here for my 2016 (still on the OEM!) as it's leaking a bit at the top now. Surprised it lasted this long in WI/MN!

 

That's gotta be some kinda record for an OEM juice box!

 

I put an AutoZone AGM in my Champion Bay this past spring. The Mercury Optimax requires a lot of CCAs so I got the biggest one they had. Also have a MinnKota Precision on board charger. I run wet cells for trolling motor and have a MinnKota alternator charger that charges them when big motor is running. I am switching to Lithiums next year for the trolling motor.

 

I run a giant 100amp hour 24v lithium on my bass boat for the Garmin trolling motor and live scope. It charges quick, it’s powerful, and runs longer than I need.

 

Those stock Tundra batteries always had so much corrosion buildup around the terminals. They corroded through the clamps that connect the battery. I tried every corrosion prevention out there. Switching to AGM did the trick. No corrosion since.

 

Thank you for reminding me to get new lead terminals! I have the nice hydraulic crimper and everything

 

I've had an agm battery for a couple years now, no diodes, just top it off once or twice a month.

 

I was noticing some corrosion and checked my water level and it was low, since i filled it, no more corrosion.

 

What size is your x2?

 

Has anyone thought about adding a diode inline the wire coming from the alternator? that way were not messing with the fuse in the fuse box.

 

I'm in a debate about this with one of my buddies right now. According Interstate and Optima, they claim you need lower voltage to maintain AGM battery? So why is everyone increasing voltage on their vehicles to maintain AGM batteries.

I've been to the Voltage Pro website and read their information, but it seems to contradict what the actual battery manufacturers are saying about charging system requirements

 

Are you talking maintenance or charge voltage. All of the charge voltages I found here a couple 10ths higher. They may need a lower maintenance charge due to less self-discharge.

 

Im talking about whatever you call the vehicle's charging system. People would buy AGM battery and then add a diode to fool the alternator to increase voltage output. Then Voltage Booster Pro came up with a more robust product to get this done.

Our Tundras seem to have a lower Voltage output from charging system than what I remember always being the standard of ~14.5V. I've read this was done to reduce load on the charging system to increase fuel efficiency but not sure how true or how much difference that makes.

So I see people in here claiming that with our lower vehicle alternator Voltage output, we must periodically top off charge the the AGM Batteries to increase life. My understanding (could be wrong) is that folks install the diode hack, or buy the Voltage Booster Pro product to increase vehicle charging system output to better maintain the life of the AGM battery.

However, there is conflicting information from battery manufactures who say optimal vehicle charging system voltage should be in a lower range for their AGM battery solutions.

Also, on Voltage Pro website, they clearly state to refer to your battery manufacturer for charging system requirements.

I already understand there are AGM specific battery chargers that should be used.

Maybe I've absorbed some of this information wrong, but it seems everyone is trying to increase the charging system voltage output as a result of fitting the AGM battery.

 

Post #2 from here https://www.eevblog.com/forum/beginners/charging-agm-battery-with-constant-voltage-14-4-volt/ :

AGM batteries generally charge at 14.6-14.8V, not the 13.6 - 14.4 of standard lead acid. Charging at 14.4v will undercharge the battery- not a terrible thing but it has to have some kind of termination mechanism, you don't want to float charge it at 14.4v if its full. You don't necessarily need a 3 phase MPPT charger but you do need some kind of charger/battery management, you want to terminate and have under-voltage that won't let the battery go below 12.5v or so for longevity. The nice thing about a 14.4v output cell is you can use it without a battery. A bare solar cell into a light load can go up to 20V. I've built remote systems with solar chargers for biology research and field cameras- it takes a bit of care to not ruin batteries and get something like their full capacity and life.

 

Hello! I did the same I purchased a brand new AGM Battery (Group 31m) put it in my tundra charging at 13.6/13.3 and similar with no issues and no top ups needed. This round of information is because it depends how and what you are asking, AGM batteries have different charging ranges. When they are low they want that 14.6+ (like AGM Battery Charger provides) but just topping up and maintenance charging during normal use in a truck the 13.3+ is actually fine and the recommendation for many AGM batteries. Heres the 3rd layer not every AGM battery is the same, some manufactures like energizer (2021 Costco era) design their battery controller and battery to be direct replacement for lead acid and be just fine as a drop in replacement.

The issue most don't see with bumping the voltages, is the stress on everything else inside the truck, the electronics are all made to operate inside a range usually like 9-19v or 6-24, 12-24 etc... and we just don't know the long term effects of running the tundras stock computer and wiring at this 15v+ some people are putting, for the cost and pain of some of these addons, sometimes in the $120+ range, it's not even a money savings vs just buying a whole new battery in 5 years which you will likely do anyways.

 

I've always read closer to 14.4 in my German cars that came with AGM batteries from the factory, also my Raptors had AGM and were also 14v. I'm not sure why the manuals are stating the lower voltage. I wouldn't worry too much about the electronics, everything besides the cigarette lighter ports probably goes through the ECU or some other module of a sort that puts out specific voltages. Generally higher voltage means less current draw demand.

 

Yeah, I haven't ever seen any evidence that Voltage Pro goes over 15 but I could be wrong.

With Voltage Pro in my truck, I see 14.2-14.6 with the two settings.

I stupidly mentioned the VBP to a friend/coworker who said he planned to install an AGM battery in his FJ which has a winch and several off-road lights. I started a conversation
about what I had read here and talking with Taylor Tuning who will modify your tune on Tacoma/FJ if you plan to install an AGM battery in order to change Alternator Output to battery.

He saw there was an option on VBP webpage for his FJ and he installed it. Asked me what his target output should be and I was always taught ideal voltage at Battery while running is 14.5. So he did all this, and also tapped into the 12V circuit for his OEM 120V transformer to pull power for an Amplifier.

Then he noticed that his 120V outlet kept shutting off. He switched the VBP to low and the outlet would stay on. I'm assuming the outlet is sensitive to voltage input.

The. He went to Interstate webpage (brand of his AGM) and read info about battery charging his AGM and is ignoring the part where it says your vehicles charging system should be below 15V. So he's decided that his Interstate Battery will fail if he has more than 14V.

He is convinced that voltage is voltage regardless of an external charger vs. his vehicles charging system maintaining his battery. I have given up the discussion. He has an email out to Voltage Pro to get their response and demand money back...

 

I've been using the Interstate AGM's from Costco on all my vehicles including the Tundra and never had an issue. The batteries always lasted between 4-7 years, easily. But that's Texas where is not that cold in the winter.

 

I got the voltage booster pro on the recommendation of a few here; made sense the way it was explained to me. I haven’t had an issue and it definitely has boosted the voltage (stays well under 15v). I can read the actual battery voltage on my head unit and it definitely increased. The truck has run fine since; although it ran fine before. Hoping it extends the battery life.

 

So this makes me wonder what advantage are you getting from increased price of AGM? I have a 2006 Tacoma with over 300K miles and my standard non AGM batteries have lasted 6-7 years each, with zero maintenance.

 

I bought mine for camping; apparently (what I read) when you are running multiple outlets and such it is a cleaner and longer lasting power. We would have the battery charge the trailer while underway and then run chargers and mattress pumps, etc at various times

 

I never looked at the AGM's from a pricing perspective. I know the Interstate brand is solid and Costco saves me a lot of money. The Interstates sales anywhere for $180 and at Costco I get it for like $110, huge price difference. That's the primary reason I go for Interstates at Costco.

 

After having a side terminal come off on my wife’s car and a post leak out acid in my vintage Porsche, I’m sold on AGMs. I put an Advance Auto 24F AGM in my 2018 and no diode and it’s been doing fine. Granted I just do regular driving and don’t off-road camp and drain it down.

added benefit is I don’t have to worry about destroying @Coupe ’s awesome battery holder.

 

Put an Interstate MTZ-34R AGM battery in my 2008 about 3 years ago, only times the truck hasn’t started until recently is when it’s been left outside in temperatures below 0 (maybe twice). But it didn’t start last weekend, but did after being jumped and started without issue after that. I did have dirty terminals, so I got them cleaned up. Could the lack of diode being causing my issues?

 

I have 2 x Bosh AGMs in my V12 BMW M8 and they lasted me 10 years. I am on my second set of AGMs since I purchased this beast in 1997.

 

You need to measure the surface voltage of your Battery and then watch voltage drop when cranking using a meter, not dash gauge.

If your surface voltage is below 12.5 ish volts, then I would charge the battery. As a matter of fact, it I had to be jump started, I would definitely pull that battery off and stand alone charge it back to full with an AGM rated charger. I wouldn't rely on your charging system to recharge a low battery. Its job is to maintain voltage and load from your vehicles components.

You could also take it into an auto parts store that does free load testing. They are able to pull a specific load in your battery based on its claimed cold cranking amps.

Dirty, corroded, or loose terminals could also be the culprit.

Running a battery with higher than OEM CCA is definitely warranted when you live in cold climate. Where I live, it rarely even hits 30's.

 

Batteries need maintenance like any other part of the vehicle. Usually put every vehicle I own on the charger on a regular basis. With the AGM in the Tundra it goes on the charger monthly since the Tundra charges at a lower voltage than the AGM needs. It's just good practice to take care of the battery and will save you money in the long run. Especially if your vehicle sits a lot. Also gives you a chance to look under the hood and address any issues should they need addressing. YMMV.

 

I have read that heat is as hard on flooded cells as cold temps. Not sure about AGMs.

 

Can anyone explain how the gm diode works. Ive done this after losing 2 odyssey AGM batteries. Im ready to go back to lead acid. A diode is an electrical equivalent to a check valve, limiting current flow in one direction. How does this boost voltage? I believe it works somehow, but dont understand how. thx.