Progressive Dynamics converter and AGM batteries

BFL13 wrote:
I don't understand where all this talk of AGMs charging faster comes from.

It's rooted in a misunderstanding of the AGM battery. You would not belive how many people assume AGM automatically means true "Deep Cycle". So a person buying one of those dual purpose "marine/rv" battery that happens to be AGM mistakenly assumes it's an actual true deep cycle battery. Many do not realize that an AGM can be a regular starting battery, a dual purpose battery or a deep cycle battery. Just like a Flooded Lead Acid can also come in all three varieties. And, we can to forget that there are some who got taken in by slick adverting where they belive their AGM is more like a lithium ion needing special charging and all sorts of stuff when reality is it's just a cousin of the flooded lead acid battery.

Sure there are some charging differences and speeds, but in the real world, that difference is only meaningful when comparing a true deep cycle AGM to a regular flooded lead acid car battery. Otherwise, the difference between a marine/rv AGM and a marine/rv flooded lead acid isn't even worth the energy to compute any minor difference.

I read that the AGM charge up to 5 times faster, but I have an Intelli-power 55 amp converter charger. If the AGM's charge twice as fast, that's enough for me to buy it.
You both can't be right!

Ed_Gee wrote:
You overlook the substantially lower internal resistance of the AGM battery. The charging process is essentially the conversion of electrons ( current ) back into chemical storage. In a wet cell much of the current is wasted as heat due to that higher resistance. In an AGM less heat and faster conversion process.

That seems legit. However, the heat does not really get going until you are over 80% SOC, so you won't notice any time saving doing a 50-80.

I just did a measured recharge on my AGMs with a 75 amper on 400AH of "ordinary" AGMs, and amps started to taper at 72.5% SOC. Same as with Floodeds at that charging rate.

It all sounds good, but I have done it both ways several times, measuring, and can't tell any difference in speed of a recharge.

You overlook the substantially lower internal resistance of the AGM battery. The charging process is essentially the conversion of electrons ( current ) back into chemical storage. In a wet cell much of the current is wasted as heat due to that higher resistance. In an AGM less heat and faster conversion process.

I also want to point out that the greater efficiency applies to all AGMs, not just LifeLines.

Ed_Gee wrote:
From Battery University:

AGM has very low internal resistance, is capable to deliver high currents on demand and offers a relatively long service life, even when deep cycled. AGM is maintenance free, provides good electrical reliability and is lighter than the flooded lead acid type. While regular lead acid batteries need a topping charge every six months to prevent the buildup of sulfation, AGM batteries are less prone to sulfation and can sit in storage for longer before a charge becomes necessary. The battery stands up well to low temperatures and has a low self-discharge.

The leading advantages of AGM are a charge that is up to five times faster than the flooded version, and the ability to deep cycle. AGM offers a depth-of-discharge of 80 percent; the flooded, on the other hand, is specified at 50 percent DoD to attain the same cycle life. The negatives are slightly lower specific energy and higher manufacturing costs than the flooded, but cheaper than the gel battery.

Yes a Lifeline AGM can accept the 5 x as many amps on Bulk. (My ordinary AGMs won't) But your 55 amp charger can't do 5 x 55 = 275 amps

And you would need a pretty big generator to run it at those kind of amps too! :)

It is a bogus claim. An AH is an AH and you can't speed up the hours while having the same amps. The charger can't "go" any faster.

From Battery University:

AGM has very low internal resistance, is capable to deliver high currents on demand and offers a relatively long service life, even when deep cycled. AGM is maintenance free, provides good electrical reliability and is lighter than the flooded lead acid type. While regular lead acid batteries need a topping charge every six months to prevent the buildup of sulfation, AGM batteries are less prone to sulfation and can sit in storage for longer before a charge becomes necessary. The battery stands up well to low temperatures and has a low self-discharge.

The leading advantages of AGM are a charge that is up to five times faster than the flooded version, and the ability to deep cycle. AGM offers a depth-of-discharge of 80 percent; the flooded, on the other hand, is specified at 50 percent DoD to attain the same cycle life. The negatives are slightly lower specific energy and higher manufacturing costs than the flooded, but cheaper than the gel battery.

I don't understand where all this talk of AGMs charging faster comes from. My AGMs charge the same speed as my previous Flooded ones did. IMO this is a bogus claim from measurements doing both.

It is true you can use way higher charging rates with Lifelines, but not with most of the other brands. My AGMs spec is to limit them to 27 amps per 100 AH, so a 55 amper on a pair comes out just right.

You can't speed up your charger doing its max rating.

Another story is you can get a better time to full charge because the AGM stays in Bulk longer so Absorption is shorter. Not with my AGMs.
And even if true (doubt it) who cares? You don't go to full on generator time so no time saving while camping. If on shore power who cares if you save a little time--time does not usually matter on shore power.

Mex says AGMs need to be recharged at a 20% or better charging rate during the Bulk stage. So that means on a bank of 200AH, you need at least 40 amps and not more than 54 (two 27s) I use my 55 amp for that.

I’d go with Renogy 104AH 12V AGM batteries.....Group 31 size. Available on Amazon for $199. and free shipping for Prime members. I am extremely pleased with mine.

Renogy AGM battery on Amazon

Checking with PD intelli-power and says it works with AGM's. Looking at Duracell Utra Platinum Group 27 AGM's. $220 each less 10% ordering online and picking up. Not too bad. Just the 92ah I don't care for. I was hoping for 100ah but if it recharges 5 times faster, it shouldn't make a difference. I was using my generator for and hour in the morning and 2 hours in the evening and still down 10 accumulating amps per day. Solar only kept it from dropping any further in daytime. But by third day I was down 30 amps on the third evening after charging. I'm hoping that the AGM's will get it charged back closer to full. I know part of the issue is the PD Intelli converter chgarger claiming to get the batteries up to 90% within 2-3 hours and another 15 hours to fully charge.

I have had two of these for a couple years now (except mine are branded as "Stark") They are pretty good for RV deep cycling work.

Their charging spec is 14.5 to 14.9 so 14.4 will be "close enough"

http://www.bestconverter.com/UB121000-100-AH-Deep-Cycle-_p_293.html#.XAR6i1KWxLM