Dual AGM battery questions

So I’ve checked everything I can in the main fuse box under the hood and can’t find anything triggered w the ignition on. Next is trying to find a source under the dash and run a wire to under the hood.

looking through threads here I don’t see a clear answer for a ignition source wire either. still searching.

 

No clean ignition in the engine bay. INJ is the closest but will be on for emissions checks while truck is off and that’s sub optimal for charging.

Poutlet 1 or 2 in the cab is my pick.

 

thank you, I will look for that.

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I have good reason to disagree with Some of what has been stated with regard to the need or benefit of increasing charge voltage for AGM batteries.

Yes, totally correct that in order to realize (store) the entirety of the Rated CCA of the battery, the higher charge voltage is necessary. But consider that rated CCA is only accurate when the battery is near new, and that actual max CCA diminishes over the life of the battery. So for me the bigger question is will the battery adequately perform the duties that I require, plus an acceptable margin? Do we replace our batteries after two years because it no longer has the rated capacity? Or do we really not care about max capacity so much as it still having Adequate Capacity for our needs? For those that do not replace a battery until the actual battery performance disappoints us, you may be interested in the following (in depth information and opinion).

Battery performance: this is much more than just CCA and length of usable life. AGM batteries, as compared to typical Flooded Cell Batteries; have tremendously less internal resistance and therefore supply heavy loads with higher sustained amperage (think starter or electric snow-plow loads). AGMs Charge incredibly fast (cars that turn off at stop lights, commonly use AGM batteries, flooded cell batteries do not charge quick enough to sustain city driving), and AGMs retain high amperage output capacity at tremendously colder temperatures (at about-40f, a flooded cell battery will barely make an incandescent interior dome glow yellow, but an AGM will still crank that frozen engine with relative ease.)

AGM's trait of lower internal resistance, means that the chemical reaction in the battery, is less restricted, and the reaction happens VERY FAST. The strength of your starter motor is a function of both Voltage and Available Amperage. Therefore the greater available amperage from an AGM can more than make up for situations of reduced available voltage, to a point. The point here is that your starter does not need those few tenths of a volt (read topped off, full charge), to still perform well. The starter will perform well even when shy a few volts. In fact, if the useful life of a battery is defined simply by the affirmative for 'does it still start my truck when I need it?' then the AGM battery will start the truck at a lower static voltage (nearer end of life) than a flooded cell, again due to the lower internal resistance to provide cranking amps.

Now for the question of overall useful life of the battery, to be clear I am speaking to the number of years of service life; There is some logic and evidence, that the useful life of a battery, is a function of how stressful the life of the battery has been. It is a well documented fact for Lead Acid batteries, that the useful life of the battery is shortened every time the battery is discharged lower than about half its total capacity (from the off grid, solar battery storage circles). Discharging a battery below half capacity, increases the stress imposed on the battery. There is also evidence, that fully charging a lead acid battery, above about 95%, causes the battery (largely) unnecessary stress. This might be evidenced by, that injecting the last 10% of charge into the battery takes a greater amount of time than the preceding 10%. Might also be evidenced by the increase in temperature during that last 10% of charging. Also can be evidenced by that I have a 2009 Tacoma, that I put a snowplow on when new, and still use for plowing snow and as my winter vehicle. During the summer, this truck is only run about once every two weeks, and never fails to start. This truck came factory with a flooded cell battery, but with the high amps necessary for plow hydraulics, I replaced the flooded cell in March 2016 (i just looked this up, to be sure. I think I may have mis-stated in a separate TW string) with AGM, and without changing anything of the trucks charging system. As I recall, that AGM battery has only been on a charger twice in it's life, once from me leaving the ign on, and once when the truck had not been run for consecutive months. Of note: Without the proper increased charging voltage; this battery has already outlived the original flooded cell battery by 1-1/2 years and still going. (with this announcement, it is certain to die tomorrow)

I may get bashed a bit here, but the vast majority of my opinion and information is developed from airplane builders, with input from many engineers and backed up by their testing; where the conversation is all about defining the intended mission for when things fail (in this case I was researching redundancy for charging system failure); and designing in enough redundancy to meet the requirements of that mission; WITHOUT over building or over compensating! Because in an airplane, you cannot ignore the costs of added redundancy, added weight, or added complexity; Lives are at stake; but only if the airplane is built light enough to be able to carry the intended passengers.

I hope to never put a plow on my 2020 Tacoma, but when the time comes, I will not hesitate to install an AGM battery, and I am not convinced that flashing for a higher charge voltage is enough advantage; The higher charge voltage does not impact the batteries ability to perform my intended function, and appears the battery may serve my purposes longer with using the slightly lower charge voltage. If your intended function, requires more energy storage than to run the radio (and amplifiers) for an hour and still crank the engine; then at some point higher charge voltage may become of value.

 

I really liked your post. ^^^^^

As a second battery I plan on maybe using a AGM battery, but some here say there will be an issue w charging. Over the past 30 years I’ve had flooded batteries w a secondary being a deep cell. My thought is they are isolated anyhow and has worked this long for me. I use all this is my work vehicle w the secondary battery running a HD 12V compressor and mainly for a converter to run heat guns, vacuums etc. My biggest thing at the minute is finding an AGM w a nice reserve to it? If I go deep cycle again I can get 105 mins or more reserve but w a longer lasting (supposedly) AGM I can only find 70 min reserves in reasonably priced. Guessing AGM just don’t have good reserve times and will have to start up my vehicle more often to charge…which in reality isn’t an issue.

 

Thanks for the comment, I hate when my postings get so long, but happy some appreciate the info.

I do not have any solid information to share on the dual battery charging issue that others express. Logically; dual batteries in parallel, would simply be seen by the computer as a single battery, that at times has a larger charging load, so I do not see why there should be any issue; but with infusion of computer monitoring, and the very fast charging rate possible with AGM batteries, it certainly seems possible for the computer to see it as a fault. With regard to dual batteries on a 3rd gen, I will be leaning on the knowledge of fellow members, already in the know.

 

Great post @Pinchaser.

I did not fret about swapping to an AGM (Optima, even, still going strong) when my new-to-me ‘16 rolled off the transfer truck with a dead battery (think the cargo switch got bumped on during loading, though I would have expected that might time out over days). Since then I’ve added a RedArc BCDC and repurposed the AGM to aux duty with a lead acid for the starter (for now, because my ‘05 came with a brand new lead acid battery). Eventually I’ll get some form of solar going since the BCDC has direct solar input. I think roof of the can is probably ideal for that but perhaps on my Leer shell, can’t decide.

Such a big difference between 2nd and 3rd gen for adjusting charging voltage. I run a stock tune on the 3rd gen and don’t have compelling reasons to change that. But with my ‘02 Tundra and ‘05 Tacoma, the HKB booster is cheap and ridiculously easy to employ. I run x2 27F’s for those older trucks, planning dual 27’s for the tundra eventually, trying to keep the ‘05 as light as possible and may swap to a 35 or lithium to reduce weight.

 

Thanks!

I hadn't heard of the HKB Booster, had to look that up.

One small thing, AGM (Absorbent Glass Mat) batteries are also Lead Acid. The common car battery is Flooded Cell. The difference is that the flooded cell, uses a liquid bridge between the plates, that is a pool of acid. The AGM battery has the space between the plates filled with a glass mat material, which is soaked with the same acid, but there is only a precise amount of acid added, just enough to saturate the glass. You can mount these batteries in any position, even upside down (SkiDoo snowmobile has it laying on its side), and they will not spill. In fact it is reported that you can drive a nail in it, pull the nail out and run the battery with a hole; with the exception of the slight plate damage, and that the hole will eventually allow that cell to dry out.

I can't help but wonder if the initiator of the AGM type battery was just making a battery spill proof, or if they already knew that reducing the volume of acid had all those other benefits too?

Since I have such a huge audience (2 is more than my typical). One additional benefit of the AGM over the Flooded Cell; is the static loss of charge while sitting dormant, is WAY less with an AGM. I cannot remember the numbers, but something like after sitting for 6 months, the flooded cell is about 1/2 dead, and the AGM is still at better than 80%. I no longer trickle charge my AGM seasonal batteries, because trickle charging has ruined two of them at only 1 year old. I find it safer to sit disconnected for 6 months in a cool environment, and then charge with a proper AGM charger.

 

No disagreement or argument with this. You have researched this topic much more than I have - I am an engineer, but not an electrical one.

My understanding of AGM battery usage is by not charging them at the higher voltage, the battery will never be at full capacity - 90 - 95%. Continued discharge from this level will shorten the lifespan of the battery. I took that at face value - I probably should have done some more research.

That said, I ran 2 Optima batteries in one of my Rangers, and 1 in the other - both at nominal charge voltage, with no issues. So, my experience agrees with yours, contrary to what I "learned" about AGMs.

For what it's worth, the CTEK DC/DC charger I currently use to charge my 2nd battery has an AGM setting, which ups the charge voltage. I do use this setting (however, I also killed a battery by many repeated discharges powering my fridge in the heat of summer - but that's another discussion...)