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Old 11-05-2016, 17:06   #1
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Mixed agm and gell

I Need to replace my house batteries. I have 8 x 6 volt GC2. I am in Grenada and all I can get is 4 AGM and 4 gell. I run 24 v so ihave two pArallel battery banks. I also have a wind generator and a solar panel for lead acid type batteries. The supplier told me that the charging rates for the AGM and gells are the same so there should be no problems. Is this correct? I am at a location where I can not get 8 batteries the same. My fastback is buy four of one type and keep my shot lead acid for the other 4 until I get to Antigua then buy 4 more so I end up with 8 the same. But then I am sailing for a few weeks with 4 new AGM and 4 dead lead acid. Please advice
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Old 11-05-2016, 17:22   #2
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Re: Mixed agm and gell

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Originally Posted by neilsty View Post
I Need to replace my house batteries. I have 8 x 6 volt GC2. I am in Grenada and all I can get is 4 AGM and 4 gell. I run 24 v so ihave two pArallel battery banks. I also have a wind generator and a solar panel for lead acid type batteries. The supplier told me that the charging rates for the AGM and gells are the same so there should be no problems. Is this correct? I am at a location where I can not get 8 batteries the same. My fastback is buy four of one type and keep my shot lead acid for the other 4 until I get to Antigua then buy 4 more so I end up with 8 the same. But then I am sailing for a few weeks with 4 new AGM and 4 dead lead acid. Please advice
Not true. Any good marine book will give you the charging voltages for different battery types. If you don't have one, go to Balmar | Marine Charging Systems | Battery Monitors | Multi-Stage Voltage Regulators | High Power Alternators | Serpentine Pulley Conversions and look at ANY regulator manual, they have great charts in each one giving the recommended voltages for all sorts of different battery types. AGMs are like wet cells. Gels NEED lower voltages.
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Old 11-05-2016, 17:40   #3
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Re: Mixed agm and gell

My charger shows gels cells float voltage at 13.8 and AGMs at 13.6.

My AGMs have the required float voltage stamped right on top of them, 13.4 to 13.6

I would tend to use the AMG setting for a mixed bank so as to not damage the new AGMs, although it would take a while to do any real damage. You can get away with a mix for a little while, but I would not do it over the long term.

Can you use a smaller bank until you get all AGMs?
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Old 11-05-2016, 22:36   #4
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Re: Mixed agm and gell

gels are way different. that's why they are no longer used....

I'd rather mix agm and flooded then agm and gel.

sail with 4 new agm. add 4 more later. forget the dead ones. 4 gc with solar and wind should last you a bit
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Old 12-05-2016, 14:26   #5
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Re: Mixed agm and gell

supplier is correct , even in automotive industry / o.1 volt / differences are completely ignored simply ..the bat. charging curves are so flat that ...it's only academic talk.
Just make sure , Do No run half dead batteries in your system, they still suck the charge
but do not hold capacity.
each bat. charger and solar cut off switch have different characteristics
who is righ ..who is wrong...just run what you have..she'll be right...
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Old 12-05-2016, 15:48   #6
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Re: Mixed agm and gell

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Originally Posted by SteveInMD View Post
My charger shows gels cells float voltage at 13.8 and AGMs at 13.6.

My AGMs have the required float voltage stamped right on top of them, 13.4 to 13.6

I would tend to use the AMG setting for a mixed bank so as to not damage the new AGMs, although it would take a while to do any real damage. You can get away with a mix for a little while, but I would not do it over the long term.

Can you use a smaller bank until you get all AGMs?
Typically float voltage is not the problem; absorption voltage is what makes the difference. If you look at the literature from battery manufacturers you will probably find that, under most use scenarios, the absorption voltage that is required to take AGMs to 100 per cent SOC as frequently as they require will be too much for gels.

IMHO charger literature is not very useful to learn the needs of a specific battery.




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Old 12-05-2016, 18:33   #7
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Re: Mixed agm and gell

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Originally Posted by svlamorocha View Post
Typically float voltage is not the problem; absorption voltage is what makes the difference. If you look at the literature from battery manufacturers you will probably find that, under most use scenarios, the absorption voltage that is required to take AGMs to 100 per cent SOC as frequently as they require will be too much for gels.

IMHO charger literature is not very useful to learn the needs of a specific battery.




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On many chargers the only difference between the gel and AGM setting is the float voltage, so it is likely the only variable he can control.
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Old 12-05-2016, 21:51   #8
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Re: Mixed agm and gell

Quote:
Originally Posted by neilsty View Post
I Need to replace my house batteries. I have 8 x 6 volt GC2. I am in Grenada and all I can get is 4 AGM and 4 gell. I run 24 v so ihave two pArallel battery banks. I also have a wind generator and a solar panel for lead acid type batteries. The supplier told me that the charging rates for the AGM and gells are the same so there should be no problems. Is this correct? I am at a location where I can not get 8 batteries the same. My fastback is buy four of one type and keep my shot lead acid for the other 4 until I get to Antigua then buy 4 more so I end up with 8 the same. But then I am sailing for a few weeks with 4 new AGM and 4 dead lead acid. Please advice


Gel batteries require different absorption and float voltages than either AGM or FLA batteries. They have become a very small part of the battery market because they received a bad reputation after incorrect charging voltages that manufacturers at the time required.

Gels, treated properly, can be the longest lasting lead acid type of battery. Properly treated 12 years isn't uncommon.

They typically have a lower bulk/absorption voltage and a higher float voltage than other batteries. They must be treated properly if you expect a good life from them. Check with the battery manufacturer for the required voltage settings.
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