AGM Battery Charging?

[HalfFish5087]

Gents,

I have a Schumacher SE-5212A charger and recently purchased 2 smart start 31 AGM marine batteries. I have looked through the manual and it does not appear that it specifically calls out that it can be used to charge AGM batteries. Also, I have done a little web searching and some say its ok to use Flooded lead acid battery charges on AGMs and others said don't. So which is it?

I did a little testing with it last night and put it on the 10A and it appeared to provide a current of roughly 8A then scaled down to 2.5A until reaching 14.6 V over about 2 hours and then floated with less than 2A intermittently at 14.8. I then took the battery off and put it on a tender which provided a current of about 1.25A at 13.8V. This appears to meet the specs of what I have found online.

Thanks!

 

[H20Rat]

Re: AGM Battery Charging?

AGM's can be charged by flooded battery chargers, but you have to watch the float voltage. 13.8 is too high and will gas out electrolyte. (AGM's float at 13.6 max) I've personally seen AGM's killed in under a year by being left on a float charger in an RV. Gel cells, on the other hand, NEVER charge those with a non-gel cell capable charger. The charging voltage for a gel cell is around 14 to 14.1 volts, non gel cell chargers will shoot up to 14.8 to 15+ volts.

 

[HalfFish5087]

Re: AGM Battery Charging?

Thanks smokingcrater! I'll double check the tender's voltage and get a new one if it was in fact over 13.6V.

 

[UncleWillie]

Re: AGM Battery Charging?

The Common Flooded cell Lead Acid battery will outgas if the charge voltage exceeds ~14.4 Volts.
The gas will vent and the water can be replaced. No real damage done.
The flooded cell will withstand a great deal of abuse. 15+ volt when charging is not uncommon.

If an AGM Battery is allowed to Outgas, the bubbles will tear up the Mat on the cells. Bad!
A small amount of gassing will safely pass through the Matting. The battery will withstand a small amounts of abuse.
Stay below ~14.4 volts when charging. 14.6v-14.8v is pushing it.

If a GEL cell Battery is allowed to outgas, The bubbles will form in the Gel and it will tear away from the plate. Very Bad.
The Gel battery will not withstand any amount of abuse.
Stay below ~14.1 volts when charging.

I do NOT see anywhere in the Schumacher SE-5212A Manual that it states it is for AGM Batteries.
Regular and Deep Cycle, Yes! AGM NO!

Get a Smart Charger designed for AGM Batteries.

Race Cars Builders routinely use AGM Batteries because they expect to crash and rollover.
Unless you realistically anticipate mounting the Batteries on their sides, or flipping the boat,
There is no advantage to buying AGM Batteries for the Boat.

 

[bruceb58]

Re: AGM Battery Charging?

There is no advantage to buying AGM Batteries for the Boat.

AGM batteries can be discharged further without reducing their capacity than flooded cell. They also are true deep discharge as well as providing amazingly high current for starting.

ODYSSEY Batteries - Marine

I use the Dual Pro PS2 for my batteries.
http://www.dualpro.com/products/professional/

They are one of the recommended chargers by Odyssey.
http://www.odysseybattery.com/documents/ODYSSEYapproved12VchargersMay2013_000.pdf
No Schumacher battery chargers that are currently in production are approved.

if you want to see the charge profile that Oddysey shows for their chargers look at this:
http://www.odysseybattery.com/chargers.html
Charge voltage is 14.7V

 

[H20Rat]

Re: AGM Battery Charging?

Stay below ~14.4 volts when charging. 14.6v-14.8v is pushing it.

Depends on who you ask... Modern AGM's are a lot better than the old ones. The largest vendor of AGM batteries says up to 15.0 volts for a normal charge, with rapid charging at 15.6 volts. If a flooded cell charger is above that, its time to toss out the charger anyway!

Support - Battery Care - Charging :: OPTIMA? Batteries

 

[TerryMSU]

Re: AGM Battery Charging?

AGMs also have much lower self discharge, meaning they hold a charge much longer without it leaking off. (Or at least that has been my experience.)

TerryMSU

 

[bruceb58]

Re: AGM Battery Charging?

AGMs also have much lower self discharge, meaning they hold a charge much longer without it leaking off. (Or at least that has been my experience.)

Mine too. I have an AGM(Oddyssey) in a Harley that doesn't get ridden often. Nice to know it will always start.

 

[HalfFish5087]

Re: AGM Battery Charging?

Thats kind of why I bought them was for their reserve capacity. Not to brag, but I got the set for $208.. As my last set of flood acid kicked the bucket in 2 years so for the same price I thought why not give it a try.

I'll try and reach out to Deka to see if they recommend any chargers. As it appears these batteries are re-branded deka intimidators.

 

[Slide]

Re: AGM Battery Charging?

I love my Optima, but I would get a charger specifically designed for AGM batteries. I had no success getting mine charged with a cheapie float charger - had to take it to Autozone after I inadvertently killed it.

 

[jhebert]

Re: AGM Battery Charging?

AGMs also have much lower self discharge, meaning they hold a charge much longer without it leaking off. (Or at least that has been my experience.)

TerryMSU

I always smile when people say things like this. Exactly what is "much lower"? I have measured the self-discharge rate of an AGM battery compared to a flooded-cell battery and found the difference in the self-discharge rate is really rather small, only a few percent difference. The difference is so small that it would only be an influence if you left the batteries sitting for a year. Over a period of a few days or weeks, the typical interval of use on a small boat, the difference in the self-discharge rate between an AGM and a flooded cell was insignificant in my actual measurements.

People apparently keep repeating this "much lower self-discharge" phrase, but there are never any measurements to authenticate it. Perhaps if someone has some measurements we could see them. My measurements showed no real significant difference.

The actual influence on the self-discharge rate has nothing to do with the AGM construction. The purity of the lead is the real factor. There are plenty of AGM batteries made with lead of no special purity. Only an AGM battery with very high purity lead will have a lower self-discharge rate. Not all AGM batteries are made with high-purity lead. It is completely misleading to suggest that an AGM battery will inherently have a lower self-discharge rate. It will not. Only an AGM battery made with high-purity lead will have a lower self-discharge rate.

There are also flooded cell batteries made with high-purity lead, and they will have lower self-discharge rate than a typical battery.

For more data see

Self Discharge of Storage Batteries
Self Discharge of Storage Batteries: Follow Up - Moderated Discussion Areas

 

[bruceb58]

Re: AGM Battery Charging?

I always smile when people say things like this. Exactly what is "much lower"? I have measured the self-discharge rate of an AGM battery compared to a flooded-cell battery and found the difference in the self-discharge rate is really rather small, only a few percent difference.

Using your own data, the difference in discharge rate between the AGM and the flooded was over 40%. So what is your definition of a few percent difference?

Typically, the self discharge of a battery is steeper in the first month and becomes somewhat constant after that. Data really should be taken after 30 days to see what the real rate is.

But this thread was about charging AGMs right?

Odysseys do use virgin lead in their batteries and that is why they have such a low discharge rate.

 

[UncleWillie]

Re: AGM Battery Charging?

Using your own data, the difference in discharge rate between the AGM and the flooded was over 40%. So what is your definition of a few percent difference?

But this thread was about charging AGMs right?

Whether it discharges 50% in 2 years or 30%; That is 2% a month or 1.25% a month.
Even if it was 1% a Month, 100% better, Does it matter in the practical world?
If you only take the boat out once a year, you need another hobby!

For the price of an AGM you could buy 2 cheapo Flooded Batteries and and a quality Maintainer and loose 0% a month.

If you insist that AGM batteries are needed to make you feel secure, get a quality smart charger designed for them and go boating.

 

[bruceb58]

Re: AGM Battery Charging?

I agree, I always keep my charger on it. I wouldn't buy an AGM just because of that reason for a boat. Its just an added benefit.

For my Harley, an AGM is the only battery that lasts more than one year because of the vibration and discharge. AGMs last 5 years in it so its a 5 to 1 ratio.