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I searched the forums but now I am just looking for a consensus -- if I can get away without going to Mazda and spending $500+, can someone suggest a battery that will meet my needs? Is I Eloop all that important?

Thanks,

Nick
 

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Get a decent AGM battery from any box store. I went with O'Reilly's Platinum it was $200.

I-eloop is only like 1mpg advantage, but it caused my flooded battery to swell and leak since i-eloop can surge up to 16v. Just remember to unplug the negative cable plug off the post before removal to avoid errors.


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FYI: Go AGM even if you don't have i-Eloop because these cars are meant to run off one.
 

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AGM is about double the money and you CANNOT top the electrolyte level off with distilled water. It's the "right tool" if you have I-Eloop, but otherwise it's a matter of whether you wish to spend the money and PROBABLY not get any longer service life out of it than a flooded battery.

The reason AGM is the right tool is that it can accept charge at ridiculous rates without damage, where a flooded battery simply cannot.
 

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Wifey’s is a 2015 w/ I-Eloop and when the Mazda battery died I just replaced it with a flooded lead acid from Walmart for $45. Works fine. AGM is still a lead acid technology, it’s just absorbed into a fiberglass mat (hence the AGM). Do not confuse it with gel cell, that’s different.

Here in the Mojave even premium batteries last only 2-3 years. No point spending crazy money on batteries.
 

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The point of the AGM isn't that it's a different chemistry -- it's that it can accept charge at a MUCH higher rate without damage, and it can also discharge far deeper and not be destroyed.
 

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The point of the AGM isn't that it's a different chemistry -- it's that it can accept charge at a MUCH higher rate without damage, and it can also discharge far deeper and not be destroyed.
How much the battery can take in a charge has to do with the plate design. I-eloop stores energy to the capacitor, not the battery.
The Q85 battery speced by Mazda is a flooded design.

AGM batteries will suffer deep discharge damage just like folded designs do. How much damage again goes back to plate design. 10.5V is a practical cutoff voltage for 12V batteries as that brings individual cell voltage down to 1.75V/cell. Given that there are 6 cells in the battery this gives you 10.5V. AGM batteries are actually more sensitive to over and under discharge.
 

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Overcharge, yes, for one specific reason -- they cannot have electrolyte replaced, and when a L/A chemistry battery is overcharged hydrogen is released at a rate that cannot be re-combined by the catalyst in the cells -- and thus the battery will vent. Once it does there's nothing you can do about it.

Charge acceptance in an AGM is MUCH higher; you can safely charge an AGM at up to five times that of a flooded cell, as electron exchange is MUCH more efficient in the glass mat than liquid electrolyte. You can also go to 80% DOD with an AGM with the same impact on life as a 50% DOD for a flooded battery. In addition they're quite resistant to sulfation, which is a significant problem with flooded cells.

The biggest problems with AGMs is that they're expensive and, if ever overcharged will be severely and irrevocably damaged. In addition there is a potential heat issue related to all lead-acid cells in that they tend to gas when charged hot and again, with an AGM once that happens you can't do anything about it (unlike a flooded battery that can have its electrolyte topped off with distilled water.) This can be a problem in a car where the battery is in the engine compartment for obvious reasons and I'm not aware of any factory car alternators with a remote temperature probe (which could be set to terminate charging at ~120F and thus prevent that issue from arising.)
 

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Where are you coming up with 80% depth of discharge for AGM? Sure when AGM was new they were somewhat optimistic about their capabilities. But in standard deep cycle application testing I’ve read and implemented over the past couple years in off-grid activities they don’t want more than 50% like others. Sure you can go lower but you will get drastically reduced lifespan from them. This brings in a cost per Ah study that is beyond the scope of what we are looking at here.
Besides deep cycling isn’t truly relevant in this case as we are looking at starting batteries in the case of automotive use. I’ve been through 3 automotive AGM batteries over the years and can’t say they gave any better performance than FLA batteries. One was an Optima Redtop that lasted about 1.5 years longer than FLA but given the cost it was still more expensive than two FLAs.
Yes AGM batteries have advantages over FLAs, but for the OP’s purpose, a simple automotive battery, those advantages are otherwise unrealized.
 

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Well if you got 1.5 years more out of an Optima RedTop then you really can't complain in any way; the "spiral cell" design batteries have materially lower amp-hours simply because the actual space consumed by plates and electrolyte is quite a lot less.

The primary advantage of an AGM cell (other than being non-spillable) in an automotive application is that it can accept charge at a much higher rate than a standard flooded battery. In an application where significant capacity is drawn down AND the charging source can deliver energy at that higher rate this means it is far more likely that the battery charge will be fully restored before the vehicle is shut down. That is a good thing from a standpoint of service life. Standard car "starting" batteries do not like to be drawn down at all -- and while "deep cycle" L/A flooded batteries are ok down to a 50% DOD on a regular basis they typically cannot deliver the cranking amps you want -- especially in below-zero temperatures. If you regularly cycle a standard "starting" battery down to 50% DOD you'll be replacing it much more frequently than you'd like.

Now whether this sort of cycling comes into play with the i-Eloop system I do not know in detail; if the computer is happy with a "standard' battery than fine and well, but whether you'll be happy with its service life is an open question. This much is certain: Mazda wants crazy money for an OE replacement, far more than a third-party branded AGM that will fit, and will also certainly work just fine.

My point is simply that for any vehicle application where material depth-of-discharge is part of the operating envelope an AGM is worth consideration since you can materially draw it down without damage -- you cannot do that with a standard flooded starting battery. Further, unlike a deep-cycle design battery suitable for a reasonable depth-of-discharge, but which can't deliver the cranking amps required in very cold conditions the AGM can deliver the amps and it also can be recharged from that lower state-of-charge much faster than a flooded battery, provided your alternator is up to the job. This latter requirement also may come into play if you, for example, like to sit with your car not running and the stereo blasting away for any material length of time.
 

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The charging system on most vehicles won’t come anywhere near to taxing what the battery can accept. In my truck I run a 200 amp alternator and FLA batteries have so far given the best service life running about two and one half to three years. AGM two years. In the application with the red top in another vehicle with a standard 60ish amp charger it experienced some extra life, however, that 150% extra life vs FLA did not meet its extra cost of being about 250% the price of the FLA.

Where I am in t Mojave desert Underwood temperatures can easily hit 150 degrees in the summer then in four months time be subjected to freezing temperatures. Somewhere like Hawai’i where it’s a much more stable temperature would probably see a longer life span for either case. Enough to offset the cost of the AGMI don’t know.

AGM is good in applications where the sealed design is needed. The non-venting design is critical for use indoors (e.g. UPS or stored solar power) to avoid hydrogen gassing that occurs with FLAs. Hindenburg anyone?

And again, to circle back around, the battery used my Mazda for the I-Eloop is an FLA. you are welcome to use an AGM, it won’t hurt anything, but unless it delivers 250% (or whatever your actual cost difference works out to) the lifespan of the FLA there’s no point in this application. Ots like driving a hybrid. If you don’t own the vehicle long enough to recoup the extra expense of the hybrid option in terms of long term fuel savings, it’s all a waste of money.
 

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The charging system on most vehicles won’t come anywhere near to taxing what the battery can accept. In my truck I run a 200 amp alternator and FLA batteries have so far given the best service life running about two and one half to three years. AGM two years. In the application with the red top in another vehicle with a standard 60ish amp charger it experienced some extra life, however, that 150% extra life vs FLA did not meet its extra cost of being about 250% the price of the FLA.

Where I am in t Mojave desert Underwood temperatures can easily hit 150 degrees in the summer then in four months time be subjected to freezing temperatures. Somewhere like Hawai’i where it’s a much more stable temperature would probably see a longer life span for either case. Enough to offset the cost of the AGMI don’t know.

AGM is good in applications where the sealed design is needed. The non-venting design is critical for use indoors (e.g. UPS or stored solar power) to avoid hydrogen gassing that occurs with FLAs. Hindenburg anyone?

And again, to circle back around, the battery used my Mazda for the I-Eloop is an FLA. you are welcome to use an AGM, it won’t hurt anything, but unless it delivers 250% (or whatever your actual cost difference works out to) the lifespan of the FLA there’s no point in this application. Ots like driving a hybrid. If you don’t own the vehicle long enough to recoup the extra expense of the hybrid option in terms of long term fuel savings, it’s all a waste of money.
I searched the forums but now I am just looking for a consensus -- if I can get away without going to Mazda and spending $500+, can someone suggest a battery that will meet my needs? Is I Eloop all that important?

Thanks,

Nick
Yuasa have a battery recommended for these cars and are reasonably priced, part number YBX7005 (Q55/Q85) 12V 65Ah 620A Yuasa EFB Start Stop Battery
 

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Now that's interesting -- Yuasa is recommending one that they rate for start/stop service. The only listings I see for it here is in the UK.... Varta, interestingly enough, recommends AGM cells for that service (go figure, eh? :))
 
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