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Old 15-09-2018, 12:37   #1
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AGM Float charging

Looking for some guidance on following:

I have 400Ah Northstar AGM 31 (NSB-AGM31) battery bank and Mitsubishi 115A alternator (A003TR0091ZT) on Volvo Penta D2-55.

As far as I can tell, the internal (“dumb”) regulator on the alternator caps voltage at 14.4V which is fine for bulk (and absorb?) charging stages of the Northstars.

However, Northstar manufacturer recommends 13.5V for float charging stage.

So...am I at risk of damaging the AGMs when motoring? Do I need to get “smart” regulator? If so, recommendations?

I’ve seen some posts indicating that the Volvo Penta D2-55 does not work well with external regulators (I.e alarms going off). Any experience to the contrary?

[new to and first post on cruisersforum so if this has already been addressed elsewhere, my apologies for duplicative entry].

Thanks
Christophe
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Old 15-09-2018, 15:30   #2
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Re: AGM Float charging

First off, wrt your title, Float is not really part of charging.

When adjusted properly a quality charge source only drops to Float V after 100% SoC has been reached, at least as often as possible.

Next the Bulk vs Absorb transition is not under regulator control. Early CC stage is max amps "striving" to bring bank to the setpoint, then once reached CV is limiting max V, current starts to drop as SoC rises, can be many more hours until Full.

______
Now, yes stock dumb VRs generally have awful charging profiles, not designed to properly care for big expensive deep cycle banks.

Yes if motoring for over 8 hours a day, you may be overcharging enough to shorten AGM lifespan.

This is a FLA advantage, little harm as long as you keep watered.

Balmar MC-614 is a good adjustable smart VR.

Also some from Mark Grasser and Ample Power, even a FOSS project by a member here.

Also look at DCDC chargers, great if you can't or prefer not to mess with the stock alt setup.

I like Sterling's, but also CTEK and Redarc.
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Old 15-09-2018, 19:48   #3
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Re: AGM Float charging

Quote:
Originally Posted by Cstrauven View Post
Looking for some guidance on following:

I have 400Ah Northstar AGM 31 (NSB-AGM31) battery bank and Mitsubishi 115A alternator (A003TR0091ZT) on Volvo Penta D2-55.

As far as I can tell, the internal (“dumb”) regulator on the alternator caps voltage at 14.4V which is fine for bulk (and absorb?) charging stages of the Northstars.

However, Northstar manufacturer recommends 13.5V for float charging stage.

So...am I at risk of damaging the AGMs when motoring? Do I need to get “smart” regulator? If so, recommendations?

I’ve seen some posts indicating that the Volvo Penta D2-55 does not work well with external regulators (I.e alarms going off). Any experience to the contrary?

[new to and first post on cruisersforum so if this has already been addressed elsewhere, my apologies for duplicative entry].

Thanks
Christophe
First piece of advice - ignore advice from anyone without direct and practical experience that relates to your question.

To your question, yes, you should consider purchasing a Balmar 614 since the Northstars are expensive and will last longer if you follow the mfg recommendations on charge voltages. I just replaced a 10 year old Northstar bank that was actually still going strong but I wanted LiFePO4. I set the Balmar at the bulk and float voltages Northstar specified, and they stayed strong for a long time.

I generally never discharged below around 60% SoC, tried diligently to fully recharge them even though it took a long time of motoring to get there, and that explains the banks longevity.

If you can spring for another $300 the Banner SmartGuage is worth the investment. I just installed one on my lead acid starter bank and it is nice to be able to see the state of charge with the press of a button.
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Old 15-09-2018, 19:59   #4
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Re: AGM Float charging

SmartGauge is an excellent product, best SoC meter on the market for lead by far.

But does not show AH usage, just SoC for House and voltage for both House and Starter.

Actually a product from Merlin in the UK, often cheaper if you can source it from there.

But Balmar (not Banner) does give excellent support for it here in the Americas.

Also available from Maine Sail's shop, best if you can to help support his amazing work for the community.
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Old 15-09-2018, 20:26   #5
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Re: AGM Float charging

Quote:
Originally Posted by john61ct View Post
SmartGauge is an excellent product, best SoC meter on the market for lead by far.

But does not show AH usage, just SoC for House and voltage for both House and Starter.

Actually a product from Merlin in the UK, often cheaper if you can source it from there.

But Balmar (not Banner) does give excellent support for it here in the Americas.

Also available from Maine Sail's shop, best if you can to help support his amazing work for the community.
Thanks for correcting my auto correct speller. Very helpful.
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Old 15-09-2018, 22:03   #6
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Re: AGM Float charging

No worries Delfin. . .
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Old 16-09-2018, 01:04   #7
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Re: AGM Float charging

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Originally Posted by john61ct View Post
First off, wrt your title, Float is not really part of charging.
You keep pushing this crazy idea that Float is not really part of charging. All chargers out of the box will drop to Float before the battery is FULLY charged - to protect the batteries - that is what they are designed to do. If you have a large bank you should adjust the absorption time to get to about 2% of the Ah capacity of the battery and this Mainesail calls 'cruiser full' - getting to 100% full in float mode then takes many more hours because of the reduced voltage still trying to charge the battery.

Quote:
Originally Posted by john61ct View Post
When adjusted properly a quality charge source only drops to Float V after 100% SoC has been reached, at least as often as possible.....
Of all the boat owners I have met none do what you are doing. It is impossible to safely do this with every day Smart chargers unless you always start at 50% SOC. If you leave a dock when 85% charged you will likely get to full but but will stay at Absorption voltage for far too long.

With Mainsail's setup if you want to check FULL you must turn off the charger and turn it back on and it will go into Absorption mode when the charge current for FULL will be 0.5% of Ah capacity. You only need to do this once a week to avoid staying at the Absorption voltage for too long. When a battery is FULL and sitting at Absorption voltage this is called overcharging.
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Old 16-09-2018, 13:36   #8
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Re: AGM Float charging

We will continue to disagree on many points.
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Old 16-09-2018, 13:42   #9
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Re: AGM Float charging

Many intelligent chargers vary the AHT depending on starting SoC, e.g. a sliding scale based on how long the CC to CV transition took.

Straight egg timers are dumb.

Just getting to endAmps once a week will harm longevity much more than a bit of occasional extra AHT.

Again, anyone that worried about the latter should just get a shunt based regulator, or

monitor manually, not hard and just a few times a week.
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Old 16-09-2018, 13:48   #10
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Re: AGM Float charging

Your last para is not accurate, that technique is a kludge compromise for less than ideal gear, and your mistaken thinking is not in line with dozens of MS's posts wrt premature infloatulation issues.

Go back and read some more, but I'm not wasting time finding all the threads for you. SailboatOwners, Sailnet, have a lot more than CF, also Trawlers, where he goes by CMS
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Old 16-09-2018, 15:46   #11
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Re: AGM Float charging

how long are you motoring? unless you are motoring longer then 4 hours everyday then I wouldn't be worried. most chargers will absorb for ~4 hours anyways.

if you are motoring 8 hours a day then yes get an external reg. if you motor 30 mins out of the marina then its' not needed.
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