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Toddavid

Convince me: AGM vs lead acid

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Great posts RJ. Agree with all except the fear comment.

Let’s consider another possibility. Perhaps it’s not about the OEM creating fear, but rather their reality that most customers/users don’t consider needing to upsize, and instead swap size for size to save a buck and then have trouble. So, to prevent larger issues like a blown ECU/ECM and even more wrath, they specify starting only because they know the CCA and reserve minutes will be sufficient. 

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3 hours ago, rjbergen said:

Let's talk starting vs. dual-purpose vs. deep cycle. This is a matter of the internal construction of the battery and relates to how a battery provides current. The chemical reaction that generates electrons, which are measured as current, occurs on the surface of the lead plates. More surface area allows the battery to supply larger amounts of current. As the chemical reaction occurs, the strength of the acid solution in contact with the lead plates decreases which decreases the battery voltage. Given time, the acid solution will diffuse and equal out throughout the battery and the voltage will climb gradually after a high current draw event.

Yes, I think at this time the topic has morphed from "lead acid vs AGM", to "starting vs deep cycle vs dual purpose (starting/deep cycle hybrid)".

I'm sticking with lead acid chemistry.

But I'm still torn on which application to get.

Best description I could find of the dual purpose batteries: 

With large, thick plates containing more antimony than starting batteries and an active lead paste chemistry, dual-purpose batteries are a good compromise, tolerating deep discharges that would ruin a typical starting battery. Since they have lower storage capacity than comparably-sized deep cycles, we recommend them for the following applications:

Runabouts or other small powerboats using a single battery for both starting and running loads with the engine turned off.

Sailboats with two identical batteries used interchangeably for starting and house electrical loads.

Boats with one battery bank that does double-duty for house applications and engine starting. Dual-purpose batteries will last longer and give more reliable service than a starting battery for about $20 more per battery.

 

Even though I have a dual battery setup, I like the ability to have reserve on both batteries, so I don't have to worry about switching banks. The Group 27 batteries in there now are dual purpose on both banks with 810CCA @ 32F, 23AMP for 175min rating. 

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On 5/19/2019 at 2:02 PM, Toddavid said:

Aren’t we now talking about two different things?

Starter type vs deep cycle type? Both lead acid and AGM come in those varieties.

I don’t think AGM is a mandate for my engine, but I’m not sure if starter type is required vs deep cycle.

And then there is starter/deep cycle hybrid type, which is already in my boat. Online research shows that type has best of both worlds for a slightly higher cost: ability to maintain voltage under heavy draw (starting) and the ability to be run low without damage (running the stereo on the hook).

My understanding is,  that AGM will give you the best of both worlds. High starting amps and can be deep cycled.  I would Google "lead acid vs AGM battiers" 

I have twin Volvos and my AGM's  start that both engines with out a problem of the past 8 years. I think what the Volvo bulletin is getting at. If the deep cycle battery is too small, than you will have a problem. If that deep cycle battery is over the rated CCA for that engine, it will be fine. From what I have read, that is the problem, not the fact that it is a deep cycle battery.   Remember too, size for size between the two, the CCA rating is lower on deep cycle.

 

Also AGM you can bring them down to 40% were lead acid is only 50% before you will have ill affects. This maybe brand dependent on AGMs but I know, not on mine

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58 minutes ago, rjbergen said:

I'm not sure how many CCA you'd have. I only have the Duracell AGM datasheet right now and they don't have a group 31 dual purpose AGM.

What brand do you have?

I bought the West Marine Groupe 31 Dual Purpose

Amp Hours (Ah): 105

  • Cold Cranking Amps (CCA): 800
  • Marine Cranking Amps (MCA): 1000
  • Reserve Minutes: 200
  • Weight: 69 lbs.

This is my starting battery (had to turn the tray sideways because it's considerably larger than the Interstate starting only battery that was in there before) and I have another pair of the same for my house bank which I run for hours.  I left all 3 batteries in the boat for the winter and plugged in my charger to keep them topped off and a couple of weeks ago when I took off the shrink wrap and put my voltmeter on them, they all read 13.7vt.  Hopefully they will continue to perform this way even with the windlass added to either bank.  I'll have to figure out what to do with the bow thruster when I cross that road.

vQnOlXk.jpg

 

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5 hours ago, Curt said:

Great posts RJ. Agree with all except the fear comment.

Let’s consider another possibility. Perhaps it’s not about the OEM creating fear, but rather their reality that most customers/users don’t consider needing to upsize, and instead swap size for size to save a buck and then have trouble. So, to prevent larger issues like a blown ECU/ECM and even more wrath, they specify starting only because they know the CCA and reserve minutes will be sufficient. 

I agree with your post, but it seems that the OEMs use fear of destroying your engine to not have to explain the intricacies of batteries. Most owner would tend to swap for identical size, and then end up with problems because a deep cycle will produce fewer CCA at the same physical size. 

For those of us that understand batteries, we have no issues increasing their size in order to use deep cycles. 

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5 hours ago, Toddavid said:

Yes, I think at this time the topic has morphed from "lead acid vs AGM", to "starting vs deep cycle vs dual purpose (starting/deep cycle hybrid)".

I'm sticking with lead acid chemistry.

But I'm still torn on which application to get.

Best description I could find of the dual purpose batteries: 

With large, thick plates containing more antimony than starting batteries and an active lead paste chemistry, dual-purpose batteries are a good compromise, tolerating deep discharges that would ruin a typical starting battery. Since they have lower storage capacity than comparably-sized deep cycles, we recommend them for the following applications:

Runabouts or other small powerboats using a single battery for both starting and running loads with the engine turned off.

Sailboats with two identical batteries used interchangeably for starting and house electrical loads.

Boats with one battery bank that does double-duty for house applications and engine starting. Dual-purpose batteries will last longer and give more reliable service than a starting battery for about $20 more per battery.

 

Even though I have a dual battery setup, I like the ability to have reserve on both batteries, so I don't have to worry about switching banks. The Group 27 batteries in there now are dual purpose on both banks with 810CCA @ 32F, 23AMP for 175min rating. 

What engine do you have? I can’t see your sig on my phone. What does the manual say you need for cranking amps?

AGMs are still lead acid. No one is saying go to a different battery chemistry. AGM vs flooded lead acid is what you’re asking. AGM will usually provide higher CCA for the same group size. 

If you’d like to stick with the same group 27, you’ll need to compare the CCA ratings of a few batteries. If you upsize to group 31, an AGM deep cycle should have no problems providing enough CCA. 

As for price, shop around. I bought my AGMs at Sam’s Club on sale for $160 each for group 31 deep cycle. I believe the flooded group 31 batteries were $80? So like twice the price but the flooded group 31 deep cycles didn’t provide enough CCA. 

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35 minutes ago, rjbergen said:

What engine do you have? I can’t see your sig on my phone. What does the manual say you need for cranking amps?

He requires a minimum 650 and 135 minutes. I believe you’ll find the Deka Group 27 Hybrid Starting/Deep Cycle is adequate initially. Looking a few years down the road, the traditional starting style should gain the edge with voltage still exceeding what his ECU/ECM needs to function reliably. He has a Gen. IV motor, and the ECU/ECM’s from that point forward are susceptible to voltage issues. The Gen. V’s are even more so, with AGM now standard with Volvo Penta. We can disagree on the fear thing some. No worries. Love your posts again. Very helpful to one and all.

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Good call on the battery voltage not holding up under load with age.

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I dropped a line to Cecil Marine, and learned the following:

New boats are shipped without batteries (guess that makes sense from a shipping weight savings and unknown commission date stand point)

Cecil only installs starting-type batteries for a configuration like mine.

 

I’m able to buy Interstate Group 27 flooded cell starting-type batteries for $110 ea., so that’s what I’m doing.

Specs on that battery are better in all respects than the Deka dual purpose, and with 6-7 hrs of stereo use I shouldn’t be running them empty (I’ll do some voltage tests after a full day of use for my own curiosity).

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2 hours ago, rjbergen said:

If you’d like to stick with the same group 27, you’ll need to compare the CCA ratings of a few batteries. If you upsize to group 31, an AGM deep cycle should have no problems providing enough CCA. 

As for price, shop around. I bought my AGMs at Sam’s Club on sale for $160 each for group 31 deep cycle. I believe the flooded group 31 batteries were $80? So like twice the price but the flooded group 31 deep cycles didn’t provide enough CCA. 

RJ,

I see from your signature that you boat on Lake St. Clair, that’s where my boat was from. I bought her through Sun Sport Marine. Wonder if you used to see her around the lake in 2015.

Thanks for your insight into batteries. If I had a Sig, I’d definitely look into deep cycle batteries, but in the end I’m just a dayboater. Changing up to a larger group and having to move things around in my engine compartment didn’t seem to be worth it.

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9 hours ago, Toddavid said:

I dropped a line to Cecil Marine, and learned the following:

New boats are shipped without batteries (guess that makes sense from a shipping weight savings and unknown commission date stand point)

Cecil only installs starting-type batteries for a configuration like mine.

 

I’m able to buy Interstate Group 27 flooded cell starting-type batteries for $110 ea., so that’s what I’m doing.

Specs on that battery are better in all respects than the Deka dual purpose, and with 6-7 hrs of stereo use I shouldn’t be running them empty (I’ll do some voltage tests after a full day of use for my own curiosity).

If this is the battery that you're looking at, $110 seems to be a decent price and it should work fine for your use. When you go to check voltages, make sure to give them about an hour with no load and no charging on them. This allows them to equalize and stabilize so that you have an accurate measure of their charge level. If you measure them back at the marina, you'll have charged them up with the engine on the way back. You could of course use one battery on the hook, then switch to the other for the ride home so you don't charge the battery you used on the hook and measure that one when you get back.

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9 hours ago, Toddavid said:

RJ,

I see from your signature that you boat on Lake St. Clair, that’s where my boat was from. I bought her through Sun Sport Marine. Wonder if you used to see her around the lake in 2015.

Thanks for your insight into batteries. If I had a Sig, I’d definitely look into deep cycle batteries, but in the end I’m just a dayboater. Changing up to a larger group and having to move things around in my engine compartment didn’t seem to be worth it.

I probably did, but there's so many boats out here it's impossible to know for sure unless it's one of the dozen or so boats I regularly raft up with. My marina alone has over 500 slips and the one next to it has 800. Those are just the 2 I'm familiar with the most, then there's 4 more right here. 6 marinas right in a row, probably over 2,500 boats right here. Then there's the dozens of other marinas around the lake. The number of boats here is easily measured in the tens of thousands.

As for Sun Sport, how was your experience with them? I can't get anyone over there to answer emails. I was trying to learn more about Chap's stringer construction techniques when I was having the crack in my bilge repaired. Chap wouldn't answer technical questions and referred me to the dealer. Sun Sport is the only local Chap dealer and they wouldn't answer my emails. That was last fall, still haven't gotten an answer to any of my 3 emails. Maybe its because I'm not trying to give them money...

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1 hour ago, rjbergen said:

If this is the battery that you're looking at, $110 seems to be a decent price and it should work fine for your use. When you go to check voltages, make sure to give them about an hour with no load and no charging on them. This allows them to equalize and stabilize so that you have an accurate measure of their charge level. If you measure them back at the marina, you'll have charged them up with the engine on the way back. You could of course use one battery on the hook, then switch to the other for the ride home so you don't charge the battery you used on the hook and measure that one when you get back.

Yep, that's the one. I plan on checking first thing in the morning before firing up, and then first thing in the afternoon after jamming out all day before firing up again.

If I understand my charging system on my current boat vs my last one, both batteries are being charged during engine operation regardless of switch position (will confirm that with a multimeter this weekend).

Sun Sport: I dealt with Neil Williams, neil@ is his email address there. He was extremely responsive and 100% honest about every detail of the boat, even took photos of rub rail defects less than a couple mm long. I bought it long distance with a survey and when it arrived in my driveway it surpassed my expectations. Paid below market, too. Drop him a line, maybe.

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On ‎5‎/‎20‎/‎2019 at 12:51 PM, Phillbo said:

I buy all my batteries at Costco ( Interstate Starting and Deep Cycle Marine ) and return them just before the free replacement period expires. They do not have the ability to test them and simply give you a new one. I always have fresh batteries and have not had to pay for one in years. 

Not surprised you're bragging about your dishonesty.

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Ok, brand new Interstate group 27 batteries swapped in.

Still having the trim sender issue, so new sender has been ordered.

However, before swap I’d always see 13.9 to 14.0v when running. Now I’m seeing between high 12s to mid 13s, even after 30 minutes of 35mph running. That would suggest depleted batteries needing a lot of charge, but they both start the engine strong and supply hours of tune power, and show 12.5v even after hours of use on the hook.

Grrr.

 

edit: wait, maybe my memory of charging systems is betraying me. Perhaps the better condition batteries are requiring less voltage to charge them, vs the ones I pulled? The lower voltage I’m seeing is not a function of a higher load on the alternator?

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So can anyone comment on my alternator behavior? My last boat had an analog gauge, and was a 2007.

I think these newer alternators are PCM controlled, meaning that they only put out voltage that's needed, to eliminate the possibility of battery overcharging issues. Stronger battery would result in lower voltage output.

I plan on testing with some electrical loads this weekend to see if there is a correlation.

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18 minutes ago, Toddavid said:

So can anyone comment on my alternator behavior? My last boat had an analog gauge, and was a 2007.

I think these newer alternators are PCM controlled, meaning that they only put out voltage that's needed, to eliminate the possibility of battery overcharging issues. Stronger battery would result in lower voltage output.

I plan on testing with some electrical loads this weekend to see if there is a correlation.

I don't think a stronger battery would mean a lower voltage output. Unless I misunderstand. I mean that it would take longer in time for the charge voltage to happen. Due to the fact that the battery would take longer to discharge. 

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12 minutes ago, Iggy said:

I don't think a stronger battery would mean a lower voltage output. Unless I misunderstand. I mean that it would take longer in time for the charge voltage to happen. Due to the fact that the battery would take longer to discharge. 

From what I am reading online, modern alternators are computer controlled and output only voltages needed to recharge the battery.

So if the battery is strong, at full charge, the alternator puts out less voltage.

This also puts less load on the engine, which help fuel economy (emissions).

Old school exciter type alternators went into charge mode no matter the charge state of the battery. So if you saw lower voltage with the older alternators it was because it was struggling to keep up with the load demands of a drained battery and other electrical needs (or you had a bad alternator).

All I did was swap in fresh Interstate batteries, and now my voltage is in the low 13v range, where it was 13.9V on the old batteries. 12.5V on both new batteries when at rest, after sitting for a few hours, so they are fully charged.

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7 minutes ago, Toddavid said:

From what I am reading online, modern alternators are computer controlled and output only voltages needed to recharge the battery.

So if the battery is strong, at full charge, the alternator puts out less voltage.

This also puts less load on the engine, which help fuel economy (emissions).

Old school exciter type alternators went into charge mode no matter the charge state of the battery. So if you saw lower voltage with the older alternators it was because it was struggling to keep up with the load demands of a drained battery and other electrical needs (or you had a bad alternator).

All I did was swap in fresh Interstate batteries, and now my voltage is in the low 13v range, where it was 13.9V on the old batteries. 12.5V on both new batteries when at rest, after sitting for a few hours, so they are fully charged.

I am just trying to use logic, but not sure. As in, "This also puts less load on the engine, which help fuel economy (emissions)." I would think if that was to happen, there would need to be a clutch to engage and disengage the Alt. Other wise its always turning. Yes?  

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2 minutes ago, Iggy said:

I am just trying to use logic, but not sure. As in, "This also puts less load on the engine, which help fuel economy (emissions)." I would think if that was to happen, there would need to be a clutch to engage and disengage the Alt. Other wise its always turning. Yes?  

Load on the engine is determined by how much voltage is being sent to the windings via the voltage regulator. Less voltage, less demand, less load. 

Apparently, modern alternators can take a cue from the engine ECM in response to electrical needs and modulate the voltage output much better than the older designs, and hence lower the load on the engine when conditions permit (and then lower corresponding emissions, the holy grail of modern internal combustion performance).

Here:

https://gearsmagazine.com/magazine/a-common-sense-approach-to-charging-system-diagnosis/

 

 

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42 minutes ago, Toddavid said:

Load on the engine is determined by how much voltage is being sent to the windings via the voltage regulator. Less voltage, less demand, less load. 

Apparently, modern alternators can take a cue from the engine ECM in response to electrical needs and modulate the voltage output much better than the older designs, and hence lower the load on the engine when conditions permit (and then lower corresponding emissions, the holy grail of modern internal combustion performance).

Here:

https://gearsmagazine.com/magazine/a-common-sense-approach-to-charging-system-diagnosis/

 

 

I have a hard time believing that. Not doubting you!!  But everything in the Alt (the windings) is turning. Than the regulator will will adjust to the needs of the amp load. When you say "  Less voltage, less demand, less load. " Less load on the ALt and not on the engine I would think? But I am no expert on Alts!

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AS a battery ages. It needs higher charge voltage to get as much power stored in it as it can................. I have seen old  batteries peaking at 15.00 volts.

AS a result they had much less energy in them to crank a engine fast enough.

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22 minutes ago, Iggy said:

I have a hard time believing that. Not doubting you!!  But everything in the Alt (the windings) is turning. Than the regulator will will adjust to the needs of the amp load. When you say "  Less voltage, less demand, less load. " Less load on the ALt and not on the engine I would think? But I am no expert on Alts!

Yes, load on the engine is proportional to the output of the alternator. The higher the output from the alternator, the more "drag" on the shaft that the engine needs to overcome, costing power (and creating emissions).

https://mechanics.stackexchange.com/questions/1536/how-much-power-hp-do-the-components-on-the-engine-belt-generally-use

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4 hours ago, Toddavid said:

Apparently, modern alternators can take a cue from the engine ECM in response to electrical needs and modulate the voltage output much better than the older designs, and hence lower the load on the engine when conditions permit (and then lower corresponding emissions, the holy grail of modern internal combustion performance).

In some vehicles yes, and equipped with AGM batteries. When the battery is charged, “registration” is required or the system can go all kinds of wonky. To this point in time, “registration” is a dealer only service.  The theory is clean, stable power to run all the sensitive electronics, not fuel economy. It seems both sides could be argued.

The alternator on your engine is a marine rated 75-amp unit, and is internally regulated. Type has been around a long time. The regulator adjusts produced voltage based on the battery.

PCM, if my old memory serves, was a Ford thing. Your engine, well most of it, is GM. They, along with Chrysler called it something different. Functionally the same though.

13 does not seem to be a cause for concern.

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