AGM Charge Rates and Times

Politics, cars, wimmen, music, tires, beer, tools, haircut, once a guy makes up his mind there is no way in hell somone else is going to argue him into changing his decision. The harder you try the deeper he digs his hooves, I mean feet, into the ground.

I'd LOVE to see lead disappear. Then I peek at my emaciated bank balance. I would be estatic to have a Mercedes 600, Christian Dior, Armani, Rolex lifestyle but instead of Mum's I have to settle for, (as Redd Foxx put it) "Champipple".

A person's gotta do the best he can with what he's got.

jrnymn7 wrote:
Yep, at u.s prices, though. Right now we're getting killed on the exchange. Today I spent $10.44u.s. on EBay... came out to $12.99can!

I totally forgot you're from Canada.

Yep, at u.s prices, though. Right now we're getting killed on the exchange. Today I spent $10.44u.s. on EBay... came out to $12.99can!

jrnymn7 wrote:
200Ah LiFePo4... $2400 (complete with BMS)

Just under $2000 for THIS ONE.

LandYacht said;

"Once Lifepo4 is only 2x the price of a top tier AGM, then I'll consider them"

I find AGM prices are all over the place, but from what I can tell, the prices (in canadian) for decent quality batteries are as such:

440Ah GC-2 Flooded... $600

440Ah GC-2 AGM... $1200

200Ah LiFePo4... $2400 (complete with BMS)

The future is now!

(Keep in mind, 50% dod's reduce cycles considerably. So, if doing 30% dod's, a 440Ah bank only provides 132Ah's, while a 200Ah LFP provides 160Ah's with no peukert effect)

jrnymn7 wrote:

I've noticed a few come with a 15a charger. How weird is that???

I find it weird too. And I haven't seen any large amp LI chargers either. You would think high amps chargers would be more common with LI.

Hey Landyacht! For me, the big deal with LI is 80% DOD, lighter weight per amp-hour (even lighter because you don't need as large a batt bank), flat discharge curves and zero maintenance (actual zero maintenance not the don't choose to do any maintenance, zero maintenance). The rest falls in the techie neato category (which I have no problems talking about all day long :B).

I took 30 AH from my 90 AH AGM last night, not really enough to see bulk stage, and my MW can only do 41 amps anyway.

By 9 AM the solar had this battery to 13.0V
I plugged in the MW, set it to 13.9v then plugged it into the battery.

Battery was accepting 22 amps total and amps started tapering instantly.

I then bumped up voltage to 14.8v, and amps jumped upto 32, and started tapering.

Usually, I see about 1 to 4 more amps into the battery over the AH from full screen ( at ABSV) on my monitor with the flooded, when amps begin tapering.

The AGM exhibited nearly the same behavior.

If one cannot take advantage of the initial higher bulk rate many AGMs can accept, then I believe flooded will still easily win the overall $ per Cycle equation. While likely measurable, the quicker acceptance stage is likely not profound, certainly not enough to warrant spending double over flooded

Also not all AGMs say they can do Extreme recharge rates like Lifeline or Odyssey or NorthStar. Some say no more than 30 amps per 100AH of storage, which is well less than a flooded can accept. Seems these limited amp AGMs are the lower $$ AGM. Perhaps these less $$ AGM are better for low and slow all day solar, but they tend to not have the high CCA ratings, which would support large inverter loads better, nor the low self discharge rates, and are limited in bulk charging amps.

I like my AGM for its insane ability to crank my engine starter violently fast, and the higher voltages held during deeper cycling, but in the end, these mean very little, as my Flooded can still start my engine easily even when 50% discharged, and supports my maximum loads, and I consider my AGM to be an expensive 'bragging rights' battery that means little to one who does not feel the need to brag.

I could really use that 165$ extra I spent on the AGM right now versus a flooded marine battery which could perform the same tasks I ask of this AGM.

I do like the no/low maintenance aspect, as it is located in a difficult to access spot in my rig which contributed to the failures of my previous flooded banks.

Once Lifepo4 is only 2x the price of a top tier AGM, then I'll consider them, but initial outlay is the painful part for me, and for many I believe. I also want to see more data from those cycling them in RV usage. I somewhat follow the marine based Lifepo4 threads, but not so closely that I have confidence in 2000+ cycles.

Adapters of a new technology tend to want it to be superior and justify the extra expense, and perhaps this desire is enough to skew the results, if what is posted online actually represents actual results, instead of the human tendency to get others to agree with them to justify their own opinion.

I think AGM's made many similar claims over flooded back when they started becoming commonplace in boats and RV's a while back, and for the most part those 'advantages' in cycle life have not turned out to be true.

So, on the sidelines I wait for more real world testing/cycling of liFePo4, and for prices to drop, which will likely take a new latest and greatest anode/cathode technology to come to market, making Lifepo4 or LiCo as antiquated as Asphalt jarred lead acid.

How long before this happens?

mena661 wrote:
You can get LFP pre-packaged for $10 per amp hour. Less if you DIY it.

http://elitepowersolutions.com/products/product_info.php?cPath=27_49&products_id=241

And that system comes with a charger too.

I've noticed a few come with a 15a charger. How weird is that???

If comparing FLA to LiFePo4, one must consider the fact that way less Ah Capacity is required for LFP. I can be better served with 200Ah's of LFP, than I am with 430Ah's of FLA. That's a comparison of $2400can vs. $600can., so 4X the initial cost. But I have calculated I would actually save money over the long haul, even if LFP doesn't live up to the purported number of cycles; something I doubt any battery type does.

If comparing FLA to AGM, (at say 2X the initial cost), could I get the same service, or better, with less Ah capacity? And could AGM end up cheaper than FLA in the long haul?

As Mex often says, one's genset is the lynch pin. So, in many cases, even though AGM's CAN be charged at a higher rate, they simply are not. I am limited to ~60a non pfc, and 75a pfc, with my eu2000i. If I had a sweet set up like christopherglenn, I could certainly charge a set of AGM's in a timely manner. But at the same Charge Current, say 75a, how do 400Ah's of AGM's compare to 400Ah's of FLA's? Do AGM's really save that much generator run time? Do they stay in bulk that much longer?

And do they handle large loads, like a microwave, better than FLA, when comparing similar constructions, such as group size to group size, or 12v to 12v, or 6v deep cycle to 6v deep cycle?