Battery charger for AGM batteries

The flooded lead acid batteries have been replaced with Lifeline AGMs on my 30 foot trawler. The start battery is a 4D. The house bank has a pair of 8Ds connected in parallel. The existing 15 amp battery charger was not designed to charge AGM batteries. I am searching for a charger for the new batteries. The marine electrician who installed the batteries has recommended a Pro Mariner Pro Nautic 1250 charger. A Lifeline Battery support tech recommended a Victron 50 amp charger yesterday. A different Lifeline Battery support tech recommended a Pro Nautic 1250 charger today. An Amazon review of the Pro Nautic charger by Aphrael does not recommend it to charge AGM batteries.
I have the following comments/questions:
1. Why should the battery charger need to be 50 amps? I could understand the recommendation, if the vessel was a sailboat. A 30 amp charger would double the output of the existing charger.
2. The Amazon review on 10/17/16 by Aphrael states that the Pro Nautic chargers should not be used to charge AGM batteries. In addition, he states that the output is the same to all battery banks. Is this a problem? I do not have the training or expertise to properly evaluate the review by Aphrael.
3. What other brands of battery chargers should I consider?
Thanks

I’m not familiar with Lifeline batteries but I was under the impression that AGMs could be charged with any quality multi-stage FLA charger. The voltage set points just need to be adjusted as per battery manufacturer’s recommendations. The main thing is the battery charger needs to be big enough to fully charge your batteries preferably every day.
My Chinese AGMs are charged mainly by solar with a Citek 15 amp mains charger as a backup. 4 years old and still like new.

DLETF said:

The flooded lead acid batteries have been replaced with Lifeline AGMs on my 30 foot trawler. The start battery is a 4D. The house bank has a pair of 8Ds connected in parallel. The existing 15 amp battery charger was not designed to charge AGM batteries. I am searching for a charger for the new batteries. The marine electrician who installed the batteries has recommended a Pro Mariner Pro Nautic 1250 charger. A Lifeline Battery support tech recommended a Victron 50 amp charger yesterday. A different Lifeline Battery support tech recommended a Pro Nautic 1250 charger today. An Amazon review of the Pro Nautic charger by Aphrael does not recommend it to charge AGM batteries.
I have the following comments/questions:
1. Why should the battery charger need to be 50 amps? I could understand the recommendation, if the vessel was a sailboat. A 30 amp charger would double the output of the existing charger.
2. The Amazon review on 10/17/16 by Aphrael states that the Pro Nautic chargers should not be used to charge AGM batteries. In addition, he states that the output is the same to all battery banks. Is this a problem? I do not have the training or expertise to properly evaluate the review by Aphrael.
3. What other brands of battery chargers should I consider?
Thanks

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If you go to the ProMariner website and download the manual for their ProNautic line of chargers, you'll see they DO have pre-set charging profiles for several different battery types, including AGM.

The output is NOT the same to all banks. The potential output might be the same -- for example, the charger COULD charge three equal banks at equal voltage rates -- but each battery bank gets a vote... and each bank will accept whatever it will accept (within the total capabilities of the charger's maximum output).

If you check the manual for your existing charger, you may find that it WILL charge AGM batteries just fine. Ours, for example, is old enough that it doesn't provide any pre-set AGM charge voltage profile... but the manual also clearly directs using the "flooded lead acid" profile for AGMs. (Ours happens to be an older ProMariner model.)

If you go to the Lifeline website and download their AGM manual for your batteries (if you haven't already) you'll see their specific charge profile recommendations. Then you may find that a given charger's best pre-set profile for your Lifeline batteries is maybe labeled for FLA; the batteries won't really care what the label says, they only care about the voltages. If you're unsure, Lifeline customer support is excellent and they'll likely be happy to help you chose which of the avialable pre-profiles is best. That said, IIRC the ProNautic line gives you a custom option, and that could let you set the charge rates exactly at Lifeline's recommendations... even better than pre-sets. (In other words, you'll likely find your info from Lifeline is more accurate than a review on Amazon.)

AGMs will usually accept a charge faster than a FLA battery of the same BCI group and type, and that's maybe why you're hearing recommendations for 50 amps. Could mean more bulk charge with less generator time will on the hook, etc.

-Chris

DLETF said:

An Amazon review of the Pro Nautic charger by Aphrael does not recommend it to charge AGM batteries.

Click to expand...

Gotta love Amazon reviews. Perhaps Alphrael is unaware that some of us have had our hands on these chargers since about 2009 (they won the 2010 Pittman award). Our first installation with one of these chargers was a boat that has a bank of Lifeline batteries. The batteries were installed at the same time we installed the Sterling ProCharge Ultra, in about 2009. Those Lifelines are still going in 2019. But hey an Amazon reviewer says they are bad for AGM...

DLETF said:

I have the following comments/questions:
1. Why should the battery charger need to be 50 amps?I could understand the recommendation, if the vessel was a sailboat. A 30 amp charger would double the output of the existing charger.

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Because good quality AGM batteries such as Lifeline, Northstar, Odyssey etc. all benefit from high current charging. Charging AGM batteries at higher rates actually helps prolong the life and is just one piece of the cycle life / longevity puzzle with AGM batteries. For example Lifeline wants to see a minimum of .2C (20% of Ah capacity in charge current) and Odyssey wants to see a minimum charge current of .4C or 40% of Ah capacity, for optimal cycle life..

DLETF said:

2. The Amazon review on 10/17/16 by Aphrael states that the Pro Nautic chargers should not be used to charge AGM batteries.

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An yet here in the real world we have piles of these chargers out there (Sterling ProCharge Ultra) charging AGM & GEL batteries with excellent cycle life, a number of these banks are now exceeding 8 years old. When you consider many AGM's are murdered in just 2-4 years this is pretty good cycle life..

DLETF said:

In addition, he states that the output is the same to all battery banks. Is this a problem? I do not have the training or expertise to properly evaluate the review by Aphrael.

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This is pretty standard for any "multi-output" charger and Sterling and Pro-Mariner are not alone in this, they all do it. There are very, very few battery chargers out there that are actually two or three complete chargers in one box. This would require three seperate power supplies and three seperate voltage regulators and can get really, really expensive.

Xantrex used to build one, so did Charles (now defunct), but the failure rate of the Xantrex was off the charts and they dropped it.

If you want to charge a different chemistry you could invest in a Sterling Power battery chemistry module (works with any charger not just Sterling) or a battery to battery charger such as the Sterling Power BB1230, again works with any charger not just Sterling..

You may want to give this a read to better understand the installation process: https://marinehowto.com/installing-a-marine-battery-charger/

CMS said:

The batteries were installed at the same time we installed the Sterling ProCharge Ultra, in about 2009. Those Lifelines are still going in 2019. But hey an Amazon reviewer says they are bad for AGM...

An yet here in the real world we have piles of these chargers out there (Sterling ProCharge Ultra) charging AGM & GEL batteries with excellent cycle life, a number of these banks are now exceeding 8 years old. When you consider many AGM's are murdered in just 2-4 years this is pretty good cycle life..

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And for OP's benefit, 1) CMS is really expert, and 2) the Sterling ProCharge Ultra and ProMariner's ProNautic are the same product.

-Chris

I have 2 Promariner chargers on board. One is charging my AGM bank and another chartes the flooded house bank. They are great chargers and they will charge AGMs just fine. Don’t get your boating facts off Amazon reviews.

There is no reason to have different voltage outputs if all of your batteries are same chemistry/same manufacturer.

The reason not to use an old flooded battery charger with AGMs is primarily the float voltage will be too low. Around 13.8 for AGM, 13.2 for flooded.

Buy a good 3 stage with a battery temp sensor, there are many available.

The main reason the manufacturers want high voltage chargers is because that is how AGM batteries desulfate(equalize). THey do it by a fast heavy charge. Like someone said above, it is good for them every now and then. I don't know how pressed you are for cash, but a good charger, like Magnum, allows you some some heavy amperage as well as customizing the charging profile. Magnum talks about their chargers as "four stage" chargers. THey have an idle stage that keeps the charge off of the batteries if it is not needed. Anyway, firm believer here. 6 year old Odyssey AGMs and not a hiccup!!!

DDW said:

The reason not to use an old flooded battery charger with AGMs is primarily the float voltage will be too low. Around 13.8 for AGM, 13.2 for flooded.

Buy a good 3 stage with a battery temp sensor, there are many available.

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Maybe: Unless the "old flooded battery charger" is already a 3-stage model that offers useful charging profiles.

Our older charger only has two pre-sets: Flooded, and Gel. The manual says to use Flooded pre-set for AGMs. The charger's float voltage is 13.5V.

Our older Odyssey batteries, per their manual, want a float voltage between 13.5-13.8V. so the older charger works for that. (Their manual also says for longest life, keep fully charged. We do. Our first bank lasted about 12 seasons. the current bank was installed in 2009, still seems fine.)

Our newer Lifeline batteries, per their manual, want a float voltage of 13.3 +/- .1V (so 13.2-13.4V). I suspect the older charger would probably be OK for that... but either way, it's not "too low." (In our case, that battery bank is on a separate charger/inverter anyway, with it's own float setting.)

SOME old chargers may not be the right thing to use. ALL old chargers aren't necessarily wrong for the task at hand.

-Chris

First, Lifeline are EXCELLENT batteries and their support is great. They are made by Concord, maker of high quality aircraft batteries. I use them in our aircraft and just installed the third set in one plane that has 23 year since the first set and over 700K miles on it.

One thing about Lifeline support, you can talk to a REAL tech person that knows his Sxxx.

I have the Lifelines on my boat and have the Magnum 2812 inverter/charger which works great. If you need an inverter too, that's a nice one! I've had the Ppronautic 12.50p 50amp charger which has been an excellent one, too, but the Magnum is better for my needs.

A lot of good posts on this thread.

Ordered battery charger for AGM batteries

After exchanging several emails and participating in phone conservations with 3 different Lifeline Battery support techs, I have ordered a Pronautic 1230 30 amp charger. One of the support techs told me that the recommendation for a charger that will produce a current of 0.2 to 0.4 % of the battery capacity is based on the assumption that the battery is 100% discharged. I have never even tried to charge a battery that is 100% discharged. The way we currently use our trawler in Puget Sound does not include spending several days anchored while drawing down the house bank. The battery banks typically read 13.2 VDC when we are back our slip. Only time will tell if I have made the correct decision. I appreciate the advice and comments of the TF community.