Battery charging

[billg]

I have wooden launch 11 metres (36ft), powered by a Perkins 215 horse diesel. Charging is by 140 amp alternator controlled by an Ample Power V3. I am about to replace my lead acid house batteries with AGM and am concerned that my start battery will not be fully charged unless I modify my charging arrangements. The start battery is charged from the house battery via a VSR. The Ample Power has provision to work with an AGM battery but operates at a lower voltage that with flooded call batteries. The system has served me well but it is time to replace my house batteries. What changes should I make to my charging system to accomodate the two types of battery?

Cheers

Bill

 

[boomerang]

Hello Bill. Curious as to why you want to change from flooded to AGM. Unless there's a specific need & since your past arrangement has served you , I personally wouldn't change the setup for the sake of change.

 

[dhays]

Welcome Bill.

I would echo what boomerang asked? If you have a specific reason to change from wet cells to AGM that is fine, but if the wet cells have been working well for you why change? Two reasons I can see to change to AGM may be to take advantage of all of the 140 amps since the AGM will likely have a larger charge acceptance rate than the wet cells. The other may be if watering the batteries has been an issue for you.

Anyway, your start battery will get fully charged. Being charged at a lower voltage may potentially shorten its life, but a start battery should last a long time as its only job is to start the engine which takes a very small fraction of its capacity.

However, there are others much more knowledgeable than I around here (ie most everyone).

 

[DavidM]

The charging profile for AGM batteries is very close to that for flooded cell batteries. So set your regulator for AGMs and the charging profile should work fine for your starting battery. Or to be really sure, replace your starting battery with an AGM.

David

 

[CMS]

I have wooden launch 11 metres (36ft), powered by a Perkins 215 horse diesel. Charging is by 140 amp alternator controlled by an Ample Power V3. I am about to replace my lead acid house batteries with AGM and am concerned that my start battery will not be fully charged unless I modify my charging arrangements. The start battery is charged from the house battery via a VSR. The Ample Power has provision to work with an AGM battery but operates at a lower voltage that with flooded call batteries. The system has served me well but it is time to replace my house batteries. What changes should I make to my charging system to accomodate the two types of battery?

Cheers

Bill

Ignore the words/Acronyms and focus on the voltages

Just take a big red marker and cross out the Battery Types on your Ample regualtor. Now that you’ve done that, find the voltage settings that match your batteries.

Let's choose a profile for a Rolls AGM battery (14.7V and 13.7V).. Do we simply select the acronym AGM from column 1 or column 2, or should we focus on the actual voltages the battery maker wants to see?

Here's an example:

Even with 11 presets to choose from, on this charge source, how well did we do..? Now imagine you only had two or three settings?

Manufacturer suggested charging voltages:

AGM Batteries – Which “AGM” Preset works?

Lifeline AGM’s = 14.4V & 13.4V = AGM Preset #1
Odyssey TPPL AGM’s = 14.7V & 13.6V = Neither AGM Preset
Firefly AGM =14.4V & 13.2V = Neither AGM Preset
Mastervolt AGM = 14.4V & 13.2V = Neither AGM Preset
Full River AGM = 14.7V & 13.7V = Neither AGM Preset
Rolls AGM = 14.7V & 13.7V = Neither AGM Preset
East Penn/Deka = 14.6V & 13.6V = Neither AGM Preset
US Battery AGM = 14.4V & 13.4V = AGM Preset #1
Trojan AGM = 14.4V & 13.5V = Neither AGM Preset

This is why we should always buy chargers, regulators and charge controllers that have a custom setting. Sure AGM preset #2 is pretty close but why aim for close enough. If it is all you had, that would be the best option.

Even with 11 presets only 2 out of 9 “AGM Pre-Sets” actually line up with an AGM brand. Again please don't focus not on the words/acronyms, but rather on the voltages they represent.

Which flooded preset works for Trojan or Deka flooded batteries?

Trojan Flooded = 14.8V & 13.5V = Neither Flooded Preset is Idea
Deka Flooded = 14.7V & 13.8V = Neither Flooded Preset is Ideal

What do all these batteries have in common? They all ideally need a user customizable voltage profile. If one of the Ample presets works for both batteries, that's great, if not choose as close as you can for the bigger, newer and more expensive bank. A flooded start battery is inexpensive and disposable, comparatively speaking, so if you must go over or under voltage on one bank, let it be the flooded start battery not the expensive AGM bank.

Over the years I have seen too many batteries destroyed by folks following words or acronyms instead of paying attention to the actual voltages the battery manufacturer recommends. Today many quality battery chargers, controllers and voltage regulators do allow full custom programming.

Start with your brand of battery then get the recommended absorption & float charging voltages from them. For PSOC type use (partial state of charge/cruising) the highest allowable absorption voltage will work best at fighting sulfation.

If both batteries are in the same or very similar voltage range +/- 0.1V - 0.2V for absorption (preferably within 0.1V) there won't be an issue.

 

[Maerin]

What CMS said.

The reason I really like the Balmar regulator is that it can be configured for the battery, down to the temperature compensation curve. I'm relatively certain I'm one of those he referred to whose expensive Lifeline L-16 bank met a premature demise because of charging shortcomings, mostly chronic undercharging from many months at anchor and not running the generator long enough to fully float the bank. Now, 480W of solar is floating the bank daily while at anchor, genset run times reduced significantly, and best of all, the new bank is at full capacity and MUCH happier.

If you have temperature sensing on the bank (a good idea), make sure it's programmed correctly. Those settings can be rather obscure, and may take some persistent research to confirm the settings are matched to your battery, they can vary significantly between manufacturers. More important yet if your batteries spend their life, as most do in an engine room that experiences regular temperature swings.

I'm with the school where a flooded start battery will easily live alongside AGM's, mine do fine. The start battery, as CMS indicated may not have as long a life as it would otherwise, but it's not significant enough to be concerned about.

 

[DavidM]

The foregoing post from CMS begs the question: How do the various battery manufacturers develop those recommended charging voltage profiles and why are they different for basically the same battery chemistry?

David

 

[FF]

"why are they different for basically the same battery chemistry?"

Who knows?

One concept to remember is charging to 14.3+ or so will use water , the more often you go to 14.?? will use more water.

A battery will charge with only one volt of push 12.8 is full, 13.8 will do the job , but it will take longer , and use less water.

If you are in a real hurry to get the noise reduced , high voltage is fine , but is 14++ really needed for every bring up plugged in a slip?

 

[CMS]

"why are they different for basically the same battery chemistry?"

Who knows?

One concept to remember is charging to 14.3+ or so will use water , the more often you go to 14.?? will use more water.

A battery will charge with only one volt of push 12.8 is full, 13.8 will do the job , but it will take longer , and use less water.

If you are in a real hurry to get the noise reduced , high voltage is fine , but is 14++ really needed for every bring up plugged in a slip?

I would urge anyone who believes this to be true to run some simple bench tests.

First charge to where you you assume is 100% SOC while letting the battery sit as long as you want at 13.8V. Now do a 20 hour discharge test on the battery and count the Ah's it delivered to the 10.5V cut off.

Now repeat the same test only this time at the manufacturers recommended absorption voltage, lets call it 14.8V for a Trojan flooded battery, until current tapers to less than 1% of Ah capacity @ 14.8V. Now run another Ah capacity test.

What will become quite obvious is that 13.8V is insufficient to charge the battery properly.

The proper absorption voltages are critically important for PSOC use.

 

[john61ct]

The foregoing post from CMS begs the question: How do the various battery manufacturers develop those recommended charging voltage profiles and why are they different for basically the same battery chemistry?

David

Because their engineers know what they're about, years of testing before a new line's released.

Slightly different formulations, physical construction details, all make a difference.

 

[Alaskan Sea-Duction]

So AGM batteries are more expensive that flood. You have to change your charging system to accommodate the new batteries. If the floods worked for you, like Boom stated why change and spend more $$$$

 

[john61ct]

This is why you should IMO pay a bit more for charge sources with fully-adjustable setpoints, you are free to select whatever chemistry you like in future.

Even basic chargers at least have the ability to select batt type from a fixed set of options.