Question to Battery Gurus... (1 Viewer)

[Markuson]

Any reason to NOT SWAP MY 31P AGM7 interstate in my dual battery system...with an Interstate 31M AGM 2-in-1 Marine with the same cranking power?

My 31P AGM7 is defective, and will take two weeks to order from interstate.
Interstate distribution manager claims there is no reason not to (save for the extra terminals I don't need). He will also do a straight warranty swap despite the 31M costing more than my existing battery.

I know some of you have used 31M batteries as main in dual setups...so looking for any reason why I should avoid the switch (assuming posts fit, etc.). Thanks!

 

[9780LC]

I don't see any reason not to. Especially since the marine battery is advertised as a 2 in 1.

 

[mcgaskins]

I have the same battery you do 31P-AGM7, and it’s been great so far. The 31M doesn’t seem to have any glaring downsides, so I don’t see why it wouldn’t work. Any idea on what caused the failure? Hopefully it’s an isolated incident because these batteries are expensive!

 

[Markuson]

I have the same battery you do 31P-AGM7, and it’s been great so far. The 31M doesn’t seem to have any glaring downsides, so I don’t see why it wouldn’t work. Any idea on what caused the failure? Hopefully it’s an isolated incident because these batteries are expensive!

The Interstate guys tested mine...and were speculating it may have been some sort of internal defect...possibly including some kind of internal short. They didn’t know...but even without load testing, it was only about 1/10th the power it should read after charging...and I had just charged it over night.

It is only about 17 months old, and will be fully replaced with a new one by Interstate. They offered the 2-in-1 AGM 31M in its place because the 31P AGM7 is an unusual battery and not even stocked at the San Didgo distribution point Interstate runs here.

Since their offer was a battery even more expensive than the 31P, it’s not a lowball offerr. He said the benefit would be its ability to crank the starter even in a depleted state due to its deep cycle characteristics...while still attaining the same CCA number as the 31P. -The 31P failing to crank in a depleted state.

This is what they offered...normally about $325:

 

[gaijin]

Shouldn't the positive and negative terminals be on opposite sides? I mean shouldn't the positive be where the negative is in your pic?



You are planning on using this as your main battery, right?

 

[Markuson]

Shouldn't the positive and negative terminals be on opposite sides? I mean shouldn't the positive be where the negative is in your pic?



You are planning on using this as your main battery, right?

Yes, as main. And no, the placement should not be a problem. The smaller terminals would actually fit underneath the extensions from Slee...or so we think. If not...of course that would mean waiting for my same battery. In any case, I'm asking if there's any OTHER reason (assuming fitment) why this 31M shouldn't supplant my 31P.

 

[gaijin]

Yes, as main. And no, the placement should not be a problem. The smaller terminals would actually fit underneath the extensions from Slee...or so we think. If not...of course that would mean waiting for my same battery. In any case, I'm asking if there's any OTHER reason (assuming fitment) why this 31M shouldn't supplant my 31P.

OK, then the answer's easy - other than fitment, looks like it should be fine.

 

[ekberger]

Unfortunately I am not the battery guru you are looking for but there is something in the back of my mind telling me that these deep cycle marine batteries are not what you want for a vehicle. I think it had to do with the fact that they are designed to be deeply discharged followed by full charge. That repeated short up and down charges like what you would have in your vehicle isn't what you want for battery longevity. I may be all washed up on this point and if so discount everything I said but the it's worth asking the question. If I do stand corrected then we all learn something.

 

[Markuson]

Unfortunately I am not the battery guru you are looking for but there is something in the back of my mind telling me that these deep cycle marine batteries are not what you want for a vehicle. I think it had to do with the fact that they are designed to be deeply discharged followed by full charge. That repeated short up and down charges like what you would have in your vehicle isn't what you want for battery longevity. I may be all washed up on this point and if so discount everything I said but the it's worth asking the question. If I do stand corrected then we all learn something.

That’s the exact same thought I had in the back of my mind...and the reason I ask. I’m not sure of how significant the “2-in-1 aspect of this battery is and how it might change what you mention. It's described as for both cranking and deep cycle. The Interstate manager thinks it’s fine, and said the benefit is that if you DO deplete the battery, it will still be able to pull a heavy crank for start-up...but I didn't want to decide in the 10 minutes I had before they closed for the day. Meanwhile, they loaned me a used battery so I didn't have to decide immediately.

 

[TeCKis300]

In general, marine anything, including battery equivalents are built to a higher standard. More lead, thicker plates, and thus the ability to handle more abuse. The deeper cycle ability means that you'll effectively have more usable Ah capacity, even if it's rated the same.

If it physically fits, I can't see how this wouldn't be an upgrade.

Sounds like your current battery had a cell internally short, hence the lower voltage reading at full charge.

Digging deeper, what are the comparable specs between the two batts? Curious about weight.

 

[fireball]

I am not a battery expert either although I do read the Internet a lot!

Everyone and their brother went out and bought the diehard platinum marine batteries for their hundred series dual battery set up's and when they started dying some folks who sound much smarter than me theorized that the issue was not necessarily with the battery itself but more so with the Land Cruiser's lack of ability to fully charge the marine battery, or the battery not seeing the larger swing in depletion and recharge.

I don't know the right answer, but will sign on to hopefully hear from someone with more knowledge and experience.

 

[TeCKis300]

Ah, and this gets into one of the significant differences between flooded lead acid vs AGM.

AGMs require a lower full charge voltage. Cars are setup for flooded batts, with a target of 14.4V. AGMs are also slightly more sensitive to high temps. So combine a non-ideal higher target voltage, with high underhood temps... I can certainly see why they may die prematurely.

After playing with numerous very high quality, light weight AGM batts on my sports cars, and having multiple ones fail prematurely, I'm back to flooded lead acid batts on all my cars. Never bothered to check/fill with distilled water, and they've given me trouble-free long term performance.

 

[mcgaskins]

I also think the 200 is hard on batteries in general. When I was searching for mine, more often than not I'd show up at a dealer's lot to find the battery was totally dead and needed a jump. I noticed in service histories many 200s needed a new battery after 24-36 months from new, and the prior owner on my truck had to get the battery replaced after only about 2 years as well. I've had the same 31P-AGM7 that Mark had since about March with nothing but good performance, but I always keep an AntiGravity XP10 AND a second backup jumper pack in the drawers at all times just in case (also keep old fashion jumper cables).

 

[Malleus]

I continually amazed at the timeliness of posts on this forum. I just replaced the 8 month old "Lexus" branded battery in my LX570 two weeks ago. It died unexpectedly. ( I'm blaming Malleus the Younger) It did start the engine after a few seconds on the jumper cables and had no trouble restarting after five minutes, but...

Good news was the dealership replaced it for free. I was given the choice between waiting five hours for full recharge, or 30 minutes for a new battery. (I felt like Dudley Moore)

 

[surfingpl]

Hi Markuson, agree with Malleus on timeliness as I was just talking to Interstate yesterday about ordering the 31P-AGM7, and just emailed Slee about their group 31 kit today. (after some reading on the subject though, I'm on the fence about switching to group 31 agm). I'm not an expert, and I can't answer your original question, but I think Tim at Interstate told me they have the 31-AGM7 (threaded posts) in stock http://www.interstatebatteries.com/Products/RT/PID-31-AGM7(Commercial).aspx? , but the model with the sae posts was about 2 weeks out. If that's true, maybe get the one with the threaded posts and use a threaded to sae adapter?

 

[linuxgod]

I'm suspect that any battery can offer deep cycle and high CCA. In my experience the best marine batteries are basically a compromise between a starting battery and a true deep cycle battery. Any deep cycle battery can be used to start a vehicle, but the amount of CCA you get out of a deep cycle is lower than the comparable weight starting battery. The problem is the only way to really confirm this is to cut the battery open and examine the plates.

AGM and gel batteries do require different charging rates. I actually thought the voltage rate was similar for flooded and AGM at ~14.7V (+/-0.1V) but Trojan says otherwise:

I have a 100Ah AGM battery on my sump pump and another on my travel trailer (https://www.amazon.com/gp/product/B01ACKDGPS/ref=oh_aui_search_detailpage?ie=UTF8&psc=1). Both get fully topped off, though - the sump has a battery charger on it, and the trailer has a pair of solar panels that ensure it gets fully charged and stays topped off. But I wouldn't use one of these as a spare battery in my LC unless I needed a deep cycle (i.e. if you run a fridge/camp lights/etc off it independently) and had a way to fully recharge it (either by plugging the battery into a charger, or via a solar panel and good charge controller. I did use my trailer battery to jump start my vehicle once when my kids left a light on inside it last spring and it worked fine. It's probably the equivalent of a 550-600 CCA battery - good for a jump if fully charged but you wouldn't want to rely on it long term in the cold.

Keep in mind starting batteries are designed for high amps but not a very deep discharge, so it doesn't take that long for the alternator to get them recharged after you start the truck. OTOH AGM (and true flooded deep cycle) batteries are designed to be discharged down to 30-40%, and then recharged typically at a lower rate (the exact rate depends on the battery size and composition but IIRC you want to charge at 5A/hr or maybe 10A/hr). If the alternator is trying to charge at a faster rate like 20A/hr (which a flooded starting battery can accept) it will potentially boil the fluid and cook the AGM battery.

In general I wouldn't trust the alternator to fully and properly charge an AGM battery unless:

• You deep cycle the battery before letting the alternator charge it (since AGM and gelled batteries are designed to last longer when regularly cycled)
• You are confident the alternator isn't charging at too high a rate (to avoid boiling the battery)
• You are confident the alternator won't apply too high a float charge once the battery is full (to avoid premature battery failure)
• You were driving for at least a day, possibly longer, to ensure it gets fully charged (since if the battery never gets fully charged you'll only get 80 or 90% of the rated capacity out of it).

 

[Reckless]

Coming from owning 4 V12 german cars, I miss having 2 monster batteries in my cars. The batteries would last forever, my dad's S550 stock battery is going great after 11 years.

With my 100, I have to replace batteries every 2 years on the dot. My 200 has had 1 new battery installed in the 1 year I have owned it. I feel this is one area where Toyota can improve.

 

[Markuson]

Thanks, all, for excellent input. Pros and cons- Thumbs up, down and in between. There are so many factors that figure into the equation, so it’s no wonder there is no simple answer...

 

[Sandroad]

Lots of good advice and ideas so far. To cut to the chase and offer a simple answer to your original question: The swap is fine, assuming you can get the 31M to fit. If you were happy with the 31P, you'll be happy with the 31M.

 

[OregonLC]

Has anyone seen any Lead Crystal products used in Highway/Overland vehicles? Looks like great technology, just problematic on cost, form factor, and availability...

Performance