Battery Maintainer/Tender

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CharBaby

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I wasn't sure where to put this subject/question(Auto Gen Topic, Mech & Maint or Auto Electrical), so I chose this section.

Question:
Are standard battery "Tender" maintainers OK to use on AGM batteries?
The "maintainers" say to use for Lead Acid Batteries but, aren't AGM batteries a form of lead acid(gel) anyway?

Thanks,

CB
 
You'd think that would be the easy way to do it while waiting on HOLD for the next available representative. Only then to get a person who doesn't really know the answer 'cause they've never come across this question.

I'm just asking those who already know.
 
CB...

If the maintainer does not specify it is good for AGM batteries... I would not be one to use it on one.

Typically the battery maintenance chargers do specifically name it is good for flooded batteries, AGM and gel batteries.

My charger did say that one the outside of the package... A 3 amp charger/battery maintainer sold by AZ.
 
It depends. If the maintainer is programmed to work on AGM then it will be fine. For example, the one that I use for my backup generator specifically states that it works for AGM and gel.

maintainer.JPG
 
I'm in the camp of not to, unless specifically allowed. AGM has slightly different charge/ float voltages.

I would use one "off label" in an emergency to get from <50% charge up to 75% but no more.
 
Originally Posted by eljefino
I'm in the camp of not to, unless specifically allowed. AGM has slightly different charge/ float voltages.

I would use one "off label" in an emergency to get from div>

I'll expand a bit on that. AGM batteries have a higher charge and float voltage. If the charger says it will work on AGM but doesn't have a setting for it, it will not fully charge the battery; maybe 75-90% if it stops at 12.6V.

Make sure your charger has a separate setting for AGM or flooded/gel batteries. Charge is well over 14V while float is closer to 13V.
 
Originally Posted by LotI
I'll expand a bit on that. AGM batteries have a higher charge and float voltage. If the charger says it will work on AGM but doesn't have a setting for it, it will not fully charge the battery; maybe 75-90% if it stops at 12.6V.

Make sure your charger has a separate setting for AGM or flooded/gel batteries. Charge is well over 14V while float is closer to 13V.

Which makes you wonder what happens when people replace a standard lead-acid flooded battery in their car with an AGM one. Can the car's charging system cope with it or will they have a continuously undercharged battery?
 
Originally Posted by LotI
Originally Posted by eljefino
I'm in the camp of not to, unless specifically allowed. AGM has slightly different charge/ float voltages.

I would use one "off label" in an emergency to get from div>

I'll expand a bit on that. AGM batteries have a higher charge and float voltage. If the charger says it will work on AGM but doesn't have a setting for it, it will not fully charge the battery; maybe 75-90% if it stops at 12.6V.

Make sure your charger has a separate setting for AGM or flooded/gel batteries. Charge is well over 14V while float is closer to 13V.


This is the right answer. They make chargers with a different AGM setting for a reason.th wonky thing to add is that temperature compensation on float is helpful too..

Originally Posted by Quattro Pete

Which makes you wonder what happens when people replace a standard lead-acid flooded battery in their car with an AGM one. Can the car's charging system cope with it or will they have a continuously undercharged battery?


AGM are great batteries. I experimented with this, running one in my E30 BMW for many years. No issues. Yes it was slightly undercharged, but the lower impedance and higher performance overall made it just fine for that little engine. I used a group 49. Ditto for the one I put into my Saab.

A degraded battery with high initial capacity and low initial impedance can still work well in a semi-degraded state, but that is vehicle dependent.

I'll note though that I reprogrammed my 135i for a 90Ah AGM and put a group 49 in there, and the voltage in that car never goes over 14.1
 
When I studied this stuff 2 years ago while installing a battery backup sump pump, I found the literature to be inconsistent regarding charge and float voltages/amps for AGM batteries. It seems some of the highest quality AGM batteries for solar power require very specialized charging profiles. With more generic off the shelf AGMs (i.e., DEKA), the charge and float volts/amps seem to have optimum rates, but they overlap flooded battery requirements it seems. GEL batteries seem the most different and require less charging voltage - 14v +/-.

Temperature seems to be more of a concern with AGM (and GEL) batteries due to their VRLA construction. For instance, a car alternator cranking out 14.8 volts in a high temp engine compartment might fry an AGM battery.

I guess my point is that while you guys talk about different charge/float voltage/amps of AGM vs. flooded, it does seem that they overlap enough so that various charges will work, but maybe not be optimized. Does that make sense? I wonder if the chargers/maintainers mentioned above with no buttons to select gel/flooded/AGM just have one "in-between" profile to attempt to satisfy all?

This DEKA literature seems thorough about the subject: http://www.eastpenn-deka.com/assets/base/0139.pdf ...Look at the temperature chart on page 11, which supports a temp compensated charger.


Also, this statement by Loti seems incorrect, especially the 13v float (too low): "Make sure your charger has a separate setting for AGM or flooded/gel batteries. Charge is well over 14V while float is closer to 13V." Gels seem best charged near 14V and flooded/AGM float charges seem to be between about 13.4 and 13.7 +/-, depending on mfg..
 
Good post man...

One thing of note...

My car has the ECM feature that rarely charges above 14.4 volts... And most of the time when I use my scanner to monitor live data it is 13.12 to 13.2. I have charged my AGM two times now.
 
I don't know how cars compensate for the high under-hood temperatures. If you look at the temp. chart on page 11 of my link (and the text next to and below), a maintenance charge of 13.12 to 13.2volts might be appropriate for the high under-hood temperatures. Higher voltages might cause gassing of flooded batteries or extreme venting/dry out of the AGM battery.

I don't think we have discussed charging algorithms under the hood with a hot engine running (or down south and the blistering sun). It has to be much different than bench/in-car charging a relatively cool battery during non use.
 
Originally Posted by doitmyself
I don't know how cars compensate for the high under-hood temperatures. If you look at the temp. chart on page 11 of my link (and the text next to and below), a maintenance charge of 13.12 to 13.2volts might be appropriate for the high under-hood temperatures. Higher voltages might cause gassing of flooded batteries or extreme venting/dry out of the AGM battery.

I don't think we have discussed charging algorithms under the hood with a hot engine running (or down south and the blistering sun). It has to be much different than bench/in-car charging a relatively cool battery during non use.


You are absolutely right ^^^^^^
 
Here's my exact scenario.

I put in a new AGM battery in my(given to me) Schumacher Jump Starter/Tire Inflator which my buddy originally purchased ~ 2010. It came with a Lead Acid Battery.

I called Schumacher and they it would be OK as they're now equipping all of their [jump starters/tire inflators/USB] with AGM batteries & the same/similar type of charger/maintainer. But again, she sounded a bit reluctant in her answer.
 
I have a another buddy who works for INTERSTATE BATTERIES here locally and he got me this brand new(correct model #) AGM battery for $30...However, with what I had mentioned above(speaking with Schumacher) and doing more searching online/youtube, it doesn't seem as though the internal charger is capable of maintaining an AGM battery regardless what the Schumacher phone rep said.
 
FYI, here are voltages applied by some of the BatteryMinder chargers/maintainers, depending on battery type:

[Linked Image from i.imgur.com]


They also do temperature compensation:
[Linked Image from i.imgur.com]
 
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