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Old 03-27-2012, 04:30 AM   #21
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RE: Comments on Changing by Battery arrangement

"However my battery charger is set to the higher charge voltage of AGM batteries meaning that it will eventually fry the wet cell engine start battery."

I always understood AGM could be charged with more AMPS ,

but if the VOLTAGE of a wet batt was used on an AGM the tiny amount of elecrolite could be boiled out.

I understood the better dock chargers had selection to lower the charge Voltage for AGM and gell.
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Old 03-27-2012, 04:48 AM   #22
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RE: Comments on Changing by Battery arrangement

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I understood the better dock chargers had selection to lower the charge Voltage for AGM and gell.
*You mean increase the voltage for AGM and Gell. Yes this is true of mine as well. However my 3 bank charger allows one selection for all 3 banks. I don't know of any charger that will allow you to charge banks and different voltages.
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Old 03-27-2012, 06:54 AM   #23
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RE: Comments on Changing by Battery arrangement

Quote:
timjet wrote:FF wrote:
I understood the better dock chargers had selection to lower the charge Voltage for AGM and gell.
*You mean increase the voltage for AGM and Gell. Yes this is true of mine as well. However my 3 bank charger allows one selection for all 3 banks. I don't know of any charger that will allow you to charge banks and different voltages.

*One thing you could do is find an old isolater.* An isolator uses a diode to keep the current from going in two directions.* That will drop the voltage .5V down stream from what is going in. But I'm not sure that is needed.

If you go to four different sites you get four different answers and this is all*from battery manafactuers.* Bottom line is AGMs Charge from between 14.2 V*- 14.8 V depending on who wrote the article.* Wet cells are in the same range 14.4 V*- 14.9 V again depending on who you believe.* So I'm not sure the charge voltage is the issue.* Float rate varies about the same as well.**So it seems that 14.4 V*-*14.6 V makes everyone happy as a charge rate for both types and with an adjustable regulator you should be able to get there.* I did find an article that explains the real problem with mixing them and in fact makes sense.

"Mixing Batteries

The reasons we do not recommend wet cell and AGM Batteries together are:

When charging, the AGM will reach full charge before the wet cell. This means that the charge system will do one of two things. It will keep charging until the wet cell is fully charged and may over-charge the AGM or it will switch off when the AGM is fully charged which means the wet cell is only partially charged.

The advantage of having 2 AGM batteries is that both can be used for starting or house use in an emergency and quicker charging means less drag on the alternator."

In my mind we are only talking one AGM here so just bite the bullet and get one.* You already have the major cost done with the for house bank AGMs.
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Old 03-27-2012, 08:50 AM   #24
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RE: Comments on Changing by Battery arrangement

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The reasons we do not recommend wet cell and AGM Batteries together are:

When charging, the AGM will reach full charge before the wet cell. This means that the charge system will do one of two things. It will keep charging until the wet cell is fully charged and may over-charge the AGM or it will switch off when the AGM is fully charged which means the wet cell is only partially charged.

The advantage of having 2 AGM batteries is that both can be used for starting or house use in an emergency and quicker charging means less drag on the alternator."

In my mind we are only talking one AGM here so just bite the bullet and get one.* You already have the major cost done with the for house bank AGMs.
*Yes, but am I really mixing wet cell and AGM's if they are on different banks? Won't the battery charger reduce the voltage on the AGM's when they are topped up and continue to charge the wet cell because it's on a different bank. I thought the charging voltage of a wet cell was less than the charging voltage of a AGM. If not then why do battery chargers have different settings for wet cell, gell, and AGM's?
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Old 03-27-2012, 10:45 AM   #25
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Comments on Changing by Battery arrangement

Quote:
timjet wrote:*Yes, but am I really mixing wet cell and AGM's if they are on different banks? Won't the battery charger reduce the voltage on the AGM's when they are topped up and continue to charge the wet cell because it's on a different bank. I thought the charging voltage of a wet cell was less than the charging voltage of a AGM. If not then why do battery chargers have different settings for wet cell, gell, and AGM's?
*Tim

I don't think your charger can see the difference.* It will charge according to what ever you have it set to.* Wet or AGM.**It is only a program.* One or the other and the same*on all three legs.* As to the voltage being different as I said there are different voltages on different sites but the middle ground is about 14.4V on both.* The major difference is the rate that the battery can take the charge of a 100 amp charger.* The wet can take 50% of it's rated capacity so a 100 amp battery can take 50 amps.* Were as the 100 amp AGM can take 100% or 100 amps.* So if drawn down both*to 50% the wet cell would take a little over an hour to be recharged but the AGM hooked to the same charger will be at full charge in about 30 minutes.* So if the charger reduces the rate to float it cuts back to 13.3 V.* Which is fine for the AGM but not enough to fully charge the wet.* If the charger continues to charge the wet at 14.4 V then the wet will get to full charge but you over charge the AGM.

I would hook my charger and alternator to the B+ of the AGM house bank.* Use an Echo charger to charge the start battery.* If it is a wet cell it will always be a bit under charged.*I would bet that more than 50% of the batteries in boats are under charged as we speak. *If you change it to an AGM the problem goes away and*it will be just fine.* I would rather have the start battery a bit under charged (which is more than enough to start the engines) than to over charge the AGMs.* In the long run the under charged state will cut the life of the wet cell by say a year or two.* So say a wet cell lasts for 5-6 years and your lasts 4-5 and it costs $75 - $100.* The AGM lasts 7-8 years and because it is being charged correctly does last 7-8 years but it cost $225 - $275.* Replace the wet every 4-5 years and money wise you are better than even.*Or use the same set up and*buy the AGM and*forget about it.*


-- Edited by JD on Tuesday 27th of March 2012 10:48:12 AM
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Old 03-28-2012, 03:26 AM   #26
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RE: Comments on Changing by Battery arrangement

One caution for AGM is never equalize the set.

16V or so ., even at a tiny amperage will kill them forever.

Be sure a solar regulator has the Equalizing feature disabled.
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Old 03-28-2012, 08:05 AM   #27
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RE: Comments on Changing by Battery arrangement

Thanks JD, good explanation. I'll probably just get a AGM for engine start and be done with it. Thanks.
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Old 03-28-2012, 08:33 AM   #28
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RE: Comments on Changing by Battery arrangement

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timjet wrote:
Thanks JD, good explanation. I'll probably just get a AGM for engine start and be done with it. Thanks.
*I think that is your best option.* You do realize that the way you have it set up that the house charger is going to split it's total 50 amps or what ever yours is,*by three.* So as an example a*50A*charger gives you 16.6 amps per leg.* Also the Gen set battery*is being charged like the AGMs at 16.6 amps.* You might consider an Echo from the*start battery to the Gen set which is the least used battery and splitting the house charger to two legs like the two Alts.* That would give you 25 amps per bank using my example of a 50 amp house charger.* When the Echo sees the Gen set as fully charged, as it will most of the time, the*start will get as much of the 25 amps as it needs.
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Old 03-28-2012, 08:46 AM   #29
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RE: Comments on Changing by Battery arrangement

Quote:
FF wrote:
One caution for AGM is never equalize the set.

16V or so ., even at a tiny amperage will kill them forever.

Be sure a solar regulator has the Equalizing feature disabled.
I equalize my Lifeline AGMs in the bus at least once a year, usually every 6 months.* There's more than one opinion on whether it is necessary but it clearly hasn't killed them yet and they're about 10 years old now.
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Old 03-28-2012, 06:04 PM   #30
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RE: Comments on Changing by Battery arrangement

Blue Seas and Charles have both introduced very smart battery chargers. One unit will charge correctly all 3 types of batteries. Gel AGM and wet cell. Nice feature if you have wet for start and AGM for house side.
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Old 03-29-2012, 05:44 AM   #31
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RE: Comments on Changing by Battery arrangement

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*I think that is your best option.* You do realize that the way you have it set up that the house charger is going to split it's total 50 amps or what ever yours is,*by three.* So as an example a*50A*charger gives you 16.6 amps per leg.* Also the Gen set battery*is being charged like the AGMs at 16.6 amps.* You might consider an Echo from the*start battery to the Gen set which is the least used battery and splitting the house charger to two legs like the two Alts.* That would give you 25 amps per bank using my example of a 50 amp house charger.* When the Echo sees the Gen set as fully charged, as it will most of the time, the*start will get as much of the 25 amps as it needs.
*JD, it was my understanding that my 3 bank 30 amp Charles charger will put out a max of 30 amps to one bank if the other two banks are full, otherwise it splits the bank charge as necessary to a combined total of 30 amps, less some line loss.

But my battery charger is really not part of this equation because of my high amp fridge. At 300 amps per daily use split between two charging periods that means I have to replace 150 amps twice a day. My 30 amp battery charger would run off the genset 10 hrs per day to keep up. Not really feasible.

I'm working with Tony Athens to determine the amp output of my alternators. He thinks they're 100 amp units but he's trying to find out for sure, Cummins did not use the same alternators on all it's 6BT's.

So to make a reasonable effort to replace 150 amps twice a day I'm running the engines for 45 minutes which should put back most of the 150 amps used per charging cycle.

It's rare we spend more than 2 days at anchor without moving the boat so this seems the most economical solution for the time being. Spending big boat bucks for isolators, echo charges, battery chargers and monitors will help, but simply running the engines for 45 minutes at 1000 rpm twice a day seems a simple economical solution.
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Old 03-31-2012, 06:35 AM   #32
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but simply running the engines for 45 minutes at 1000 rpm twice a day seems a simple economical solution.

Not if you figure engine life.

BUT since most yachties seldom wear out an engine in a lifetime , it will be the next owners problem.

The real solution would be better fridges , or a different energy storage system.

Batteries , even AGM take time and only hold so much energy, and do not get full that quickly..

Perhaps a eutetic system ( Coldplates) might work better.

And there is always Propane , for months of quiet.

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