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Old 19-07-2019, 18:12   #1
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GEL and AGM batteries

Hi , I need some help because I have 2 banks with 4 batts .The first one is composed by 2 batt of AGM of 100 and 150 volts .No problem but the other bank is composed now by one gel 150 Amp and one AGM 100 amps .
Both banks are connected a samlex charger .Smart? .
It's possible charge the bank with gel and agm batt as usual and trust in the smart charger ? .Any problem could be produce for different way to stock the charge ? .
Any experience .Thanks
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Old 19-07-2019, 18:28   #2
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Re: GEL and AGM batteries

I had to throw in a gel this year among 4 agm's for the house system. I watched it all season and it acted fine. The solar charger seems to handle it ok too. Guess I wouldn't know there was a difference if it didn't say "gel" on the side.
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Old 19-07-2019, 18:32   #3
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Re: GEL and AGM batteries

I think you meant 100 and 150AH in your second sentence, I can change it for you if you want.

That is a horrible mix of batteries, why not have one house bank (assuming there is another engine start battery you haven't mentioned) and join the three AGMs together. Not sure what to do with the gel battery, is it fairly new? sell and replace with AGM perhaps.

What are the charging voltages the manufacturers give for each of the batteries? You need the absorption and float voltages.

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Old 19-07-2019, 18:32   #4
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Re: GEL and AGM batteries

Iím thinking though over time life will be reduced, if your chargers are set for AGM, Iíd assume itís the gel that is going to have a reduced lifespan, question is by how much?
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Old 19-07-2019, 18:47   #5
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Re: GEL and AGM batteries

It's a matter of amp hours per Quetzal. The charge rates for agm and gel differ little.
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Old 20-07-2019, 01:53   #6
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Re: GEL and AGM batteries

Short answer "no".


Charge voltages and acceptance rates are quite diff between the two. Charging a GEL at AGM voltages will significantly shorten the life. Charging AGMs at GEL profiles will chronically undercharge them thus shortening their life.

Mixing battery chemistries in one bank might get you thru a season or two, but there is no charger made that can handle that properly. Yet another way batteries are murdered.
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Old 20-07-2019, 06:21   #7
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Re: GEL and AGM batteries

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Originally Posted by belizesailor View Post
Short answer "no".


Charge voltages and acceptance rates are quite diff between the two. Charging a GEL at AGM voltages will significantly shorten the life. Charging AGMs at GEL profiles will chronically undercharge them thus shortening their life.

Mixing battery chemistries in one bank might get you thru a season or two, but there is no charger made that can handle that properly. Yet another way batteries are murdered.

I have 3 chargers on the boat. All three have the same indicator light for agm and gel, what's with that?
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Old 20-07-2019, 06:48   #8
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GEL and AGM batteries

Quote:
Originally Posted by Ecos View Post
I have 3 chargers on the boat. All three have the same indicator light for agm and gel, what's with that?


I donít understand the question. I guess your saying your charger has the same program for both?
If so, then Iíd suggest itís not a real good charger
However at best pre programmed chargers are a little suspect at best, they are sometimes very close to required voltages, sometimes not, AGMís voltages differ by manufacturer and many seem to think that the charging rates and profiles are the same, an AGM is an AGM, but they sometimes differ significantly. Other chemistries are Iím sure the same.
That is the problem with preprogrammed chargers, brand x battery sometimes differed from brand y even though they have the same chemistry.

I believe beliezesailor is correct
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Old 20-07-2019, 07:09   #9
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Re: GEL and AGM batteries

Actually there 4 chargers on the boat. The wind generator seems to know, solar charger ditto and the main battery charger. The alternator regulator is the only one that has a gel setting and I don't use the engine for charging that much.
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Old 20-07-2019, 09:27   #10
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Re: GEL and AGM batteries

Quote:
Originally Posted by Ecos View Post
I have 3 chargers on the boat. All three have the same indicator light for agm and gel, what's with that?
Dunno, but thats odd, on most they are different and in terms of battery chemistry the charge profiles are different. AGM charge profiles are closer to FLA than GEL.
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Old 20-07-2019, 09:29   #11
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Re: GEL and AGM batteries

Quote:
Originally Posted by a64pilot View Post
I donít understand the question. I guess your saying your charger has the same program for both?
If so, then Iíd suggest itís not a real good charger
However at best pre programmed chargers are a little suspect at best, they are sometimes very close to required voltages, sometimes not, AGMís voltages differ by manufacturer and many seem to think that the charging rates and profiles are the same, an AGM is an AGM, but they sometimes differ significantly. Other chemistries are Iím sure the same.
That is the problem with preprogrammed chargers, brand x battery sometimes differed from brand y even though they have the same chemistry.

I believe beliezesailor is correct
Being able to program times and set points directly is definately better. My old NextStep regulators are like that...no battery type setting at all, but lots of control over charge profile parameters.

But to the OPs question, no amount of parameter tweaking will correctly charge a bank of mixed battery chemistries.
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Old 20-07-2019, 09:37   #12
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Re: GEL and AGM batteries

There are obviously people who are happy to just create "banks" out of whatever batteries they come across.

If they are cheap and you don't care about maximizing longevity fine, rarely will there be a safety issue.

However, if you do want to do things right, like goes with like, not just the same chemistry

not just the same model batteries

but ideally the same production run, matching mfg dates.

Every decent deep cycle battery has detailed documentation, manuals and datasheets, showing the precise charging profile specs.

Both Sonnenschein and EPM's GEL deep-cycling batteries' specs (are there any others worth buying?) will show both current rates and voltage setpoints well below the same size AGM.

GEL are famous for being easily damaged* by overcharging.

AGM really need the higher voltage and C-rate for longevity.

Now again, if you're sourcing your batteries from automotive and big box retail sources, who knows, they don't last long anyway so doesn't really matter.

If you do care, post the specific battery models, ideally links to their specs and we can help optimize what you currently have and advise what do do when the bank needs replacing.

Ideally besides dedicated Starters, you should have only one big bank.

*damaged may just mean greatly reduced longevity - "worked fine for years" does not mean optimal care
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Old 20-07-2019, 09:48   #13
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Re: GEL and AGM batteries

Like most things in life the best results come from using the right tool for the job. I would run the banks until they die the rebuild with a new bank designed to meet your particular boat use. To get best performence that will be a matched set and generally 2 large 6v rarther than multiple batteries untill bank size makes that impossible
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Old 20-07-2019, 10:46   #14
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Re: GEL and AGM batteries

thanks to all, it is clear to me that the 150 amp gel battery must be charged with its own charging profile and separated from the AGM.
The distribution on my yacht is a bank composed of two batteries of 100 AGM amps which are used independently to start the generator and the other to start the engine. In this way, the generator starter battery is always available.
The other bank that is the reason for my question is the service one and it is now composed of a 150 amps gel batt and another AGM 100 amps.
According to the answers received, I will use the third charge output of the Samlex 12 volts 30 Amps to separately charge the gel batt with its own profile
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Old 20-07-2019, 11:03   #15
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Re: GEL and AGM batteries

Link to that Samlex please.

It would be very unusual for outputs to deliver separate profiles.

Sterling does so with add-on modules.
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