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Old 26-03-2019, 20:58   #1
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Join Date: Jul 2008
Boat: Pacific Seacraft 37
Posts: 20
pirate Batery charger drops to float too soon?

Hi everyone,

I recently installed a Sterling Pro Ultra 12V - 60 amp battery charger. I am using it to charge a tired and soon to be replaced 625Ah bank of Lifelines. My power source is a Honda 2000. I have the charger programed to 14.5 for Bulk and 13.3 Float. I bumped the V up a tenth over recommended Lifeline charging voltages because it seemed like the charger was displaying 14.4 while the terminal voltage was reading 14.2. The charger would then go into float before terminal voltage was at full 14.4 and thus I feel like the battery is not fully charged. I have observed the unit go into float mode while the battery monitor (sg200) is still showing 17 amp going in. When this happens, I turn the charger off, wait a few minuets and then restart it and the voltage then goes up to 14.1 or so and starts pumping in 20 or so amps.

In order to correct for this apparent premature flotation I am wondering if it makes sense to set the float voltage to something like 14.4. As long as I monitor the amp input and shut the charger off at around 6 amps input can I assume that my battery is fully charged and that I wont be overcharging them?

Just now the charger switched to float and it still shows that it is putting in 10 amps while in float. Is there any reason to continue to let my generator run with the charger in float mode at 13.2 while it is still showing an input of 10 amps?

There are no loads on the battery. Having turned the charger off (once it went into Float) only minuets ago, my terminal voltage is at 12.6-12.7 with no loads on the system. I know my batteries are pretty shot and have a set of Firefly being shipped to me but I still have a month and a half of cruising until I arrive in Guam to pick them up.

Any insight and advice is appreciated.

Grant Gardner
s/v Viandante
PSC 37
Pohnpei, Micronesia
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Old 26-03-2019, 21:22   #2
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Join Date: Sep 2014
Location: Auckland, NZ
Boat: Compass 790 , 7.9 metres or 26 ft
Posts: 1,140
Re: Batery charger drops to float too soon?

Basically, as I understand it, you can't escape the battery taking time to reach fully charged state. But you can definitely help shorten the time required by doing as you suggest. I would programme it to be at least 14.8 for bulk & 14.4 for float.
But a disclaimer here: I'm not a battery expert, just read a lot about them. We put a 14.7 volt regulator on our alternator to charge our pair of 225amp Crown 6v deep cycles & it works way better than the old 14.1v reg with no issues but we turn it off if motoring for more than a few hrs.

Lifeline says on their website to have bulk charge as high as possible.
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Old 27-03-2019, 06:05   #3
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Join Date: Jan 2017
Posts: 11,804
Re: Batery charger drops to float too soon?

Yes, AHT cannot be extended on those otherwise excellent chargers, re-starting until you get to 100% Full is the most common workaround. But half the cycles not critical, few times a week is enough.

Or as you say, set Float = Absorb, as long as you have an alternative way to stop charge within an hour or so after reaching your endAmps spec.

A Victron BMV with a programmable relay like 712 might work, just cut the charger's input.

Personally I'd be wary of relying on (my) human memory.

Here's a couple Maine Sail posts on AGM time requirements using Lifeline as an example

New Balmar Alternator Charging Question
john61ct is offline   Reply With Quote

charger, loa

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