Charging deep cycle battery

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I have researched and it appears this isn’t recommended and some say won’t even work as the charger isn’t strong enough.

Been doing it for years but was wondering if it is “bad” per se.

24DC everStart
Powers 55 pound trolling motor on a 14’ fishing boat.

Rarely gets below 75%.

I come home from fishing and plug it in to my 0.75A BT. Usually flashes green. Then steady in a day or so.

I have the SAE connectors on the battery set up so it can power other things if needed. So I am not looking to change anything unless absolutely needed.

I’d the 0.75a too low of a charge?
 
Not at all. A 750 mA BT is essentially what is called a trickle charger ... it will not overcharge your large deep-cycle battery. Nor will it fast charge your battery. But it is charging your it, just not fast, as in it takes 12 to 24 hours to recharge your battery with this low current charger. BatteryTender chargers switch to a "float mode" when your battery is fully charged, reducing the charge current to a very low amount (that steady light state you mentioned). This low "float" current mode keeps the battery at 100% and ready for immediate use.

You can leave the BatteryTender hooked up indefinitely.

Your charger is a low current unit, and it will take hours for it to properly charge your battery. But it is working. Wait for the the steady-state light before disconnecting and using it again. You're doing things correctly. Use it with confidence.


I would like to mention that the "ideal" charge rate for lead-acid and AGM batteries is the battery's amp-hour (AH) capacity divided by 10. So, if this battery is a 55-AH battery, the ideal charge rate would be 5 or 5.5 Amps. Chargers in the 4, 5, or 10-Amp range would be ideal. Your 0.75-Amp charger just takes a while to charge it.
 
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Is this a flooded battery or an AGM battery? Have you confirmed that your charger is actually getting the battery to a 100% SOC (test with a voltmeter or preferably a battery hydrometer) ?
 
Some battery tender type devices may not fully charge a dead battery that is too large:

The NOCO Genius 1's manual says that it will go into an error state if the battery isn't fully charged after 24 hours or something like that.

Since it only puts out 1 amp, this means you either cannot use it to fully charge a dead battery of over about 24AH in size OR you have to unplug and reset it after 24 hours to continue charging.

No idea if it actually does error out, I haven't tried using one to charge a really dead battery...
 
I have researched and it appears this isn’t recommended and some say won’t even work as the charger isn’t strong enough.

Been doing it for years but was wondering if it is “bad” per se.

24DC everStart
Powers 55 pound trolling motor on a 14’ fishing boat.

Rarely gets below 75%.

I come home from fishing and plug it in to my 0.75A BT. Usually flashes green. Then steady in a day or so.

I have the SAE connectors on the battery set up so it can power other things if needed. So I am not looking to change anything unless absolutely needed.

I’d the 0.75a too low of a charge?
I think as long as the charger gets the battery back up to 100% after use, it's fine.
 
I keep all 3 of my vehicles on Noco Genius 1's. What I like about the Genius 1 over the Battery Tender, is it has 3 different settings. 1.) Flooded lead acid. 2.) AGM, and 3.) Lithium Ion.

They only put out 1 amp. Sometimes my vehicles will sit for a week, and this assures the batteries are always fully charged to 100%. They will not overcharge a battery. Once 100% charge is reached, the unit goes into "Float Mode", and monitors the charge.

If it drops off, it will then go into "Topping Off Mode", and install a milliamp charge until it is fully charged again. I have mine wired right into the battery terminals, and just plug them in.
 
Some battery tender type devices may not fully charge a dead battery that is too large:

The NOCO Genius 1's manual says that it will go into an error state if the battery isn't fully charged after 24 hours or something like that.

Since it only puts out 1 amp, this means you either cannot use it to fully charge a dead battery of over about 24AH in size OR you have to unplug and reset it after 24 hours to continue charging.

No idea if it actually does error out, I haven't tried using one to charge a really dead battery...

One of my problems with NOCO is they dont make it easy to understand what each chargers upper and lower limits are - you basically have to download the manual to see.

CTEK, and Optimate publish this right on the spec sheet for each model.
 
You're doing things correctly. Use it with confidence.
^ What Steve said. I just bought my third Schumacher 1.5A maintainer for my AGM motorcycle battery. I bought 2 about 15 years ago and gave one to my son and both have worked beautifully all these years. The Battery Tender brand are hard to beat but I liked the longer power cord on the Schumacher.
 
would be better if you charged it a higher bulk charge amps, but the real question is what voltage does the BT charge at in bulk charge? in float charge? if it holds 13.6V in float charge mode then you're fine it will bring it back to 100% SOC in a few days.
 
Is this a flooded battery or an AGM battery? Have you confirmed that your charger is actually getting the battery to a 100% SOC (test with a voltmeter or preferably a battery hydrometer) ?
Flooded.
Multimeter says 12.8-13.2
 
I bought a Noco 1A on
Prime day thanks to you guys on here. However, with the different connectors, I didn’t want to start changing things and the battery posts are not accessible.
 
would be better if you charged it a higher bulk charge amps, but the real question is what voltage does the BT charge at in bulk charge? in float charge? if it holds 13.6V in float charge mode then you're fine it will bring it back to 100% SOC in a few days.
Bulk stage is not a voltage, it is a maximum amperage stage that will take a certain amount of time, to get the battery to absorption voltage, well hopefully absorption.

The higher the amperage potential of charging source, the sooner absorption voltage is achieved.
The charger is basically maxxed out, in bulk. Constant current stage.

Once absorption voltage is achieved then the amperage required to maintain absorption v, tapers. Constant voltage stage

When amperage ,with battery still bei ng held at absorption voltage, tapers to about 1% of the flooded battery capacity rating, at 20 hour rate, rated in amp hours, hopefully a temperature compensating hydrometer dipped into each cell reads 1.270, or higher.

This is unlikely, and less likely the older and more abused the battery is.

If people actually used a hydrometer, they will likely find that specific gravity is well below 1.275 and the battery, especially a group 24 or 27 or 29 or 31 flooded marine battery, being cycled below 80% state of charge, is not fully charged, despite that green light glowing from their well marketed charging source.

Ideal, is truly fully charged.

Charging any undercharged battery toward full, is better than no charging, but initial amperage rate becomes important in deep cycle duty, in terms of maximizing potential battery performance, and longevity .

Trojan, one of the most respected deep cycle flooded battery manufacterers, says apply 10 to 13% of capacity in bulk mode, until 14.82v i absorotion voltage is reached.

So a 100 amp hour group 27 should be fed 10 to 13 amps initially, until 14.82v is reaches at battery terminals, then holding absorption voltage for 1 to 4 hours more will be requires before battery is in 95% charged range.

Premature dropping to float voltage, is the deep cycled lead acid battery killer. A Week+ more on a maintenance charger before.next discharge cycle, hopefully should get the healthy battery full. The less than healthy battery has much lesser chance.

Starting the next discharge before a true fill charge has been attained, is cumulatively damaging rthe battery capacity, and its ability to maimtain respectable voltahe powering lightnor heavy DC loads.

The deeper the discharge, the more important the recharge becomes.

Almost every 'garage' charger wll drop to float prematurely, onna deeply cyxledarine/ trolling battery, and the deeply cycled battery subjected to partial state of charge cycling, loses capacity significantly faster, than if it were truly fully charged, first respecting that 10 to 13% initial charge current in bulk stage, then held at absorption for long enough, and only then maintained at the proper temperature compensated manufacturer recommended float voltage, by a maintenance charger.

This is ideal treatment.

Good enough, is opinion, and there is no shortage of those these days.

Achieving ideal can be expensive in equipment, and/or time.

It Could be very well easier, to just replace more often, and worry about more consequential topics.

But one should know what ideal is, then draw their OWN line in the sand as to how far they wish to take it.

Those wanting ideal, should be watching a voltmeter, AND an ammeter, as their charging source does its thing.

A hydrometer, like the the OTC 4619, is the flooded lead acid battery polygraph, as to state of charge, but ignorance is indeed blissful.

Most deeply cycled flooded, maintenance free, or AGM marine batteries, will be far from fully charged, when the smart charging source, glows that soothing lying green light, in deep cycle duty.

More tham charged enough to start an engine, but far from charged enough, to prevent premature capacity loss.

Could be good enough though.

Decide what is 'good enough', for yourself.

Ideal, is not opinion.
 
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I wouldn't overthink this too much. The bottom line, regardless of battery type, size, or voltage is that a battery is better off, and will overall last longer if it is kept at or near a 100% charge level.

Most any of these newer "smart chargers" can accomplish this task. And they're inexpensive and easy to use.
 
Bulk stage is not a voltage, it is a maximum amperage stage that will take a certain amount of time, to get the battery to absorption voltage, well hopefully absorption.
let me be more specific... the real question is what maximum voltage does the charger reach & hold at the conclusion of bulk charge before it drops to float.

"bulk" charging requires higher and higher voltage to keep pushing amps into the battery as it charges. how high it goes matters more than how many amps it can push into a dead battery.

I'll take a 0.7a charger that reaches 14.4 before it floats at 13.6 over a higher amp charger that doesn't.
 
I spin dials on adjustable voltage power supplies, to choose target voltage, while watching an ammeter showing total charger output, and amp hour counter which also displays amps into or out of battery.

Ive a battery temp display and adjust accordingly.

I do this Hundreds of times per year.

I can limit amps with voltage dial, keeping target voltage a few tenths above combined voltage, or just set it to 14.4v, attach to battery an have 41.1, or 97.7 amps to achieve that target voltage.

I easily see what my chargers are doing, and what the battery can take, and judge performance/efficacy of my recharge regimen.

Balmar mc 614 voltage regulator does have a separate ' bulk voltage' and absorption voltage and float setpoints

Some batteries, after a period of time held at 14.4v , like my deka intimidators, will accept 99.5% of the amperage at 13.9v as they will at 14.4v, so no point in holding 14.4v.

My Northstar agm-31 however, lowering voltage from 14.7v to 14.2v cuts amperage by 33%, so that battery i leave at 14.7v till amps taper to 0.5, then float at 13.6ish.

Get an ammeter, its like a speedometer. Watch it and learn, and then get frustrated as smart charger X drops to float flashes green light well before amps taper to the point the battery can be considered full.

A hydrometer will prove it too.
But ignorance is blissful.

A newish healthy battery can get to 100% at float voltage with enough time, the battery past half life, will not, and just accellerate the degradation.

Initial charge rate is important, in deep cycle duty, when one seeks very good to excellent cycle life.

Getting to as high a state of charge as possible, with high amperage charging sources, is far less detremental to the battery compared to starting the next deep discharge cycle from less than full charge.

Not only does starting a discharge from 90% SOC yield less electrical storage, it will take less time to take battery below the 50% boogieman, and it then takes even longer to recharge, even though total capacity has walked down.
Partial state of charge deep cycling is abusive.

7 psoc cycles in a row will have voltage held by battery during same discharge regimen, appear pathetic.

Achieveng true full after 7 psoc cycles takes about twice as long when held at absorption.

If it is not held for long enough, it is just another PSOC cycle.

The lower the state of charge when each discharge begins, the more the battery hates the Psoc cycling, and the faster its available capacity walks down.

Without a true full charge, that reduced capacity from many psoc cycles back to back, will be irreversible. No matter the physics defying claims of the marketers and those without any way to actually judge battery performance.
 
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