AGM/Gel/Wet Cell Lead Acid Charger

Four Suns

Four Suns

Not a pot stirrer
TECHNICAL Contributor
Oct 4, 2006
10,533
Williamsburg, VA
Boat Info
2003 480 DB
Engines
QSM-11 Diesels
I replaced four 8D batteries this year with Deka AGM batteries (about 150 freekin' pounds per battery). I bring this up because people always confuse AGM and Gel batteries and I was doing some poking around this morning in technical manuals. I actually am replacing an alternator on my port engine today and was reading up on battery charges, etc.

The Deka website has a good discussion on the difference between AGM and Gel cell batteries here:

http://www.eastpenn-deka.com/assets/base/0139.pdf

If you go to page 11 of that document, they give two charts for battery charge values for AGM and Gel over various temperature ranges. Note that the AGM batteries are charged higher than the Gel batteries and the AGM batteries are more closely aligned with regular wet cell values.

So here's the issue...

My boat has a PD2050 charger:

http://www.progressivedyn.com/prod_details/marine_conv/marine_conv_pd2050_1.html

It's a 900 watt smart charger and can handle 3 batteries. It is currently hooked to two Deka 8D batteries and the generator battery (a West Marine AGM). My other two 8D's are only for the bow thruster and hooked in series for a 24 volt configuration and have their own charger.

In looking at this charger, I noticed it was discontinued and they've come out with the "PD2100 Series" and it's a link on the top of that page.

http://www.progressivedyn.com/prod_details/marine_conv/marine_chargers_pd2100.html

The updated charger now has charge cycles for Gel, AGM, and regular wet cell whereas the old PD2000 series only handled regular wet cell. The voltage values for AGM, however, do NOT match what Deka recommends for AGM and the PD2100 series appears to charge AGM and Gel the same way..

So what's the poop with that? At first blush, it appears the charger company got it wrong.... Based on the values and profile Deka says to use, my old PD2050 for regular lead acid wet cells is more aligned correctly than the newer PD2100 and the AGM setting...
 
Back in the good old days when I had my/Dom's 410DA I switched from wet cell to AGM. I also chose Deka AGMs although based on the electrical needs of the vessel I used 5 group 31s. I can't recall the make and model of the charger, but it worked just fine. I believe that this is one of the advantages of AGM batteries - that they have very similar charging profiles to wet cells.

I can't wait for my current set of 6 8D batteries plus one group 27 to crap out so I can get AGMs.
 
One more thing on the PD2100 series of chargers. If you go to the Deka document I pointed out above on page 14, they make the following statement:

What is a safe charge rate or voltage
setting for outdoor applications with wide
temperature fluctuations if a temperature-
sensing charger is not available?

NONE! As the chart on page 11 (Effect of Temperature on
Recharge Voltage) shows, charging voltage varies widely with
temperature. There is no fixed voltage setting or current that
will work. A temperature-sensing, voltage-regulated charger
must be used. Anything else will damage any battery and cause
premature failure!

Heck.. I can't find anything on the PD2100 series or PD2000 series that shows how temperature is accounted for on the charging profiles... Hmmm... My engine room temps vary from 40 degrees to 120 degrees.

Jeff: Just wait until you try and lift the AGM 8D's and wedge them in front of your engines... they are double the weight of the regular lead acid ones.
 
I think the key is how battery people define maximum performance. Key criteria for batteries include things like how long they hold a charge, cranking amps, long duration amps, total capacity and stuff like that. If you are building a UPS bank for a data center, you also care about cycle time. Not only do you want to draw the maximum number of amps over the longest duration of time, but you also want to get the batteries back up to 100% as quickly as possible. Therefore, to optimize cycle time, you want to charge at the highest rate possible. In order to do that, the charger must monitor voltage, current, and temperature.

On the other hand, if you don't care how long it takes to recharge the batteries, charge them at a lower voltage and current, which makes monitoring temperature nearly immaterial since the lower charge rate does not stress the batteries.

Best regards,
Frank

BTW, I hate batteries. They're a pain in the
 
Xantrex seems to be a little more serious about their charging technology though. If you look at their marine chargers, they have temp sensors that mount to the battery terminals and adjust the charging profiles based on battery temp.

http://www.xantrex.com/web/id/180/p/docs/pt/7/product.asp

You can also put in custom charging profiles to align with the battery manufacturer's recommendations if the "AGM" or whatever setting doesn't match....

Just an FYI.
 
Skipping to the end of the technical discussion, while I do understand the theory involved, when I first changed to AGM's in 1999, the charger/converter makers didn't provide us with user settable conditions, so we just put 'em in and went boating. Our boat is a 1996 and we've had great success with AGM's in Florida's temperature and environment so I'm wondering just how important cycle times and temperature variables really are.
 
I guess I'm just a little paranoid because the 8D AGM's are not cheap by any means... I got off easy with a $2K bill... some versions of these 8D's are over $1K a piece.
 
Four Suns said:
Xantrex seems to be a little more serious about their charging technology though. If you look at their marine chargers, they have temp sensors that mount to the battery terminals and adjust the charging profiles based on battery temp.

http://www.xantrex.com/web/id/180/p/docs/pt/7/product.asp

You can also put in custom charging profiles to align with the battery manufacturer's recommendations if the "AGM" or whatever setting doesn't match....

Just an FYI.
Click to expand...


Ive got that charger installed in the armored vehicle at work. I really believe xantrex makes the best charger out there. Not only does this unit allow charging of three banks, independent of each-other with pre-sets for Lead Acid, AGM and Gel... It also has settings for Li-On and I believe mercury based batteries. Plus as stated, it has a user settable custom option. Along with all of this, it has the ability to have three temp sensors hooked up; one of these sensors can also be a shunt. What this shunt does is monitor the battery usage so when it's time to charge, the charger knows exactly how much power was used out of the battery and charge it as required instead of using voltage, resistance and amperage as a way to determine about how much of a charge it needs.

Only downside to this charger (and any multi-bank charger I've ever seen) is, you have to get it in 12v or 24v. You can't run two banks on 12v and one on 24v. All must be the same. There for requiring two chargers if running banks of different voltage.
 
Robski97 said:
Gary,
U got some tab runing between a/c , the refrig and now batteries... ID be a witts end...

Rob
Click to expand...

You are forgetting the port engine alternator, the polished stainless raw water tube on the port engine, front gear oil seals on both engines and new fuel coolers on both engines. I did have a private discussion with the boat yesterday as I pulled off the AC fan.
 
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Gary,
I'm really happy with the ProMariner Pronautic 1240i I recently installed. It has the remote display reporting temp and adjusting the charge rate accordingly.
FinalChargerinstall5-4-088.jpg

FinalChargerinstall5-4-084.jpg


Also, it will charge 3 banks (I'm using two) and has settings for AGM, GEL, and Wet Lead. I think it's overkill for my boat, but do like the remote display and how fast this thing bring my batts back to full charge.
Here's the 24v version
ProNautic 2430
 
Looked at your battery document. It looks like all of the other ones that I have read that pertain to AGMs. The voltages and temperatures might be different, but the curves look about the same.

Here’s the problem as I see it and why I’ve not bought into AGMs. You can buy a AGM charger, like the Xantrex that will monitor voltage, current, and temperature such that when you go down to your boat first thing in the morning, the batteries are perfectly charged with a minimum of gassing.

Then you jump into your boat, while wearing boat shoes and carefully avoiding the hatch lift handles. Feet preserved, you light the fires, toss the power cords and dock lines, and throttle up. During the six hour trip to BIH, the engine mounted alternators are charging the nearly fully charge batteries at 14.2 volts, well above the recommended 13.1 volt optimum float voltage.

Theoretically, the batteries should be out gassing or in thermal run-away when you’re running the mains. The stock alternators are programmed to put out about 14.2 volts. The regulators generally do reduce output when hot, but the regulators are in the alternator and are mostly likely sensing the heat coming off the engines. However, despite what the books says, Frank W says he gets great performance from AGMs without special treatment.

I think Balmar makes alternators with external regulators that have external regulators with temperature compensation and AGM profiles. Break out another grand or two for new alternators and regulators.

Seems like a big pain in the butt just so you can start the mains. Did I mention that I hate batteries?

Best regards,
Frank
 
Four Suns said:
You are forgetting the port engine alternator, the polished stainless raw water tube on the port engine, front gear oil seals on both engines and new fuel coolers on both engines. I did have a private discussion with the boat yesterday as I pulled off the AC fan.
Click to expand...

These things will $5k you to death and not even show anything for it. It sounds like Gary took the 1st quarter of the year off and made up for it with $10k worth of maintenance in the last 6 weeks. :huh:
 
fc3 said:
...the engine mounted alternators are charging the nearly fully charge batteries at 14.2 volts, well above the recommended 13.1 volt optimum float voltage.
Click to expand...

That's why I started looking at this stuff again... and since I'm putting on a new alternator, I wondered about the charging levels for AGM.
 
While my experience with AGM batteries is not as long as Frank's, I have had Enersys Odyssey AGMs in my boat since the beginning of last season. http://www.odysseyfactory.com/batteries.html

My boat has the standard Intelli Power PD2040 charger (which does not have any special adjustments for AGM or gel batteries) and standard alternators.

No issues with batteries so far. Great investment, particularly because the batteries were free (my neighbor is one of the founders of Enersys).
 
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Four Suns said:
So here's the Balmar info:

http://www.balmar.net/index.htm

and the regulator issue:

http://www.balmar.net/page14-Regulatorsmain.html

Yet something else to think about. I think I like Frank W's approach... but then I'm sure I will NOT have his luck. His boat never breaks.
Click to expand...

I like the Alternator side Regulator idea.
I have wondered now that the batts are topped off, especially when we're disconnecting from a marina, to head to home or whatever, I question if I'm 'overcharging' the batteries from the alternator.
A regulator may be simple. Balsam makes a smaller unit it looks like. I don't need the monster one your system may require.

Good link!
 
Pirate said:
These things will $5k you to death and not even show anything for it. It sounds like Gary took the 1st quarter of the year off and made up for it with $10k worth of maintenance in the last 6 weeks. :huh:
Click to expand...

Yes.
 
Running the boat on Saturday it was about 100 degrees outside and I noticed both alternators had dropped to 12.85 volts so I assume there is some temp-based regulation that occurs. I believe the voltage is measured right after the alternator because the wires coming off the the thing go into an engine mounted box where the wiring harness from the bridge plugs into. That voltage number corresponds to a battery temp of 110+ degrees per the document which I would bet was the case on Saturday.

I'm not going to change anything... I'm going boating.
 
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