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500 amp hour battery bank with 2 different chargers: a 25 amp charger and a 4 amp charger.

Which is more efficient for a battery to suck up?

Please don't make it more complicated than the question is :)


Merci!


Mark
 

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Depends on how charged batteries are to start with. My understanding is from 50% to 70-80% makes little difference. After that unless you have Li and have Pb based batteries the batteries can only accept a decreasing amount as they come to full charge. The rest of the energy is in part released as heat. So ultimately depends on the design and sophistication of the two different chargers. The one that presents just enough energy that can be efficiently absorbed will be the winner.
 

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If you're charging a nearly full bank and not using more than 4 amps at the time, I would think the difference would be negligible.

If you're charging a discharged bank that will accept more than 4 amps, I'd have to say the larger charger, which will run fewer hours. For that matter, I don't think a 4 amp charger would ever properly recharge a deeply discharged 500 Ahr bank, especially if the "trickle" charger only does so in float voltage.
 

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The 25A will be your better choice. You're looking at an effective charge rate of just 0.05C (5% of Ah capacity) and most AGM's can easily be charged much, much faster, typically in the .4C or 40% of Ah capacity range...

The problem with the trickle charger is that your bank may be full before the trickle charger can even get to the limiting absorption voltage. 4A is just .8% of capacity and this does not include on board loads which could easily make it a charger smaller than .5% of Ah capacity.. A 100% chock full Lifeline AGM is considered full at .5% of Ah capacity at 14.4V.

Also, if this is a true "trickle charger", meaning constant current only, no absorption and no float, it can actually damage the batteries. Stick with a true multi-stage marine charger.
 

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bell ringer
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500 amp hour battery bank with 2 different chargers: a 25 amp charger and a 4 amp charger.

Which is more efficient for a battery to suck up?

Please don't make it more complicated than the question is :)


Merci!


Mark
the 25 amp charger (that's the simple answer to me)

but that's making assumptions of SOC and charging source

but a 70-100 amp one would probably be even more efficient for the first couple hours

what good is a 4 amp charger anyway? My refrigerator uses more power than that

BTW - I didn't read anyone else's answer because I don't care, this is MY answer
 

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Actual trickle chargers are traditionally totally crippled-stupid, no concept of stages at all like a PSU really. Very much not recommended.

If by "efficiently" you mean lower heat losses, not using so much input power, that does not depend on current rate throughput and is not important with mains as your upstream source, nor even a genset in practice.

If by "efficiency" you mean time taken charging from a depleted state to 100% Full, then higher amps will make a difference.

But not as much as you'd think with lead chemistries, especially with FLA. With GEL you don't want to fast charge anyway.

AGM has a very high CAR, but still takes 7+ hours no matter how much current you throw at it. might save 20-30min doubling amps offered.

https://marinehowto.com/how-fast-can-an-agm-battery-be-charged/

If this answer - simple as I could make it - was not comprehensive, please clarify your question.
 

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500 amp hour battery bank
Yes with a 500Ah bank, beside the 4A charger taking 100 hours

depending on the chemistry, **dropping to 5 or 10A** may be the specification for knowing that you're at 100% Full.

Since the max charge is 4A, there is a real danger that rate being **too** low will result in overcharging.
 

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Discussion Starter #10
I made a mistake by thinking that a question simply put would give the wanted answer. I see I was wrong and didn't realise assumptions would be made that throw my question off course.
Sorry... so... here is the amended question that I think has been answered by 'heat' but I'm not sure.

I am in a marina in London for all of winter with *Extremely* expensive electricity. US 30 cents per kilowatt (GBP .245 cents per KW).

I have solar panels in a reasonably sunny position. But I need to augment that with a bit of shore power charging.

I generally only drop the batteries down 10% per day... about 50 amp hours on the meter. This will be made up by the solar on a normal sunny day. But when its not due to ice, snow, grey clouds ect I need to put in about 50 amp hours per day.

I only turn on any charger on demand and turn it off before fully charged (I get to fully charged on sunny days at least once per week).

So the question is does a battery accept charge better faster or slower?

The answer appears to be the by-product of heat produced by the units. Where heat is generated there must be an inefficiency in the charging unit.
The longer the charger is on the more time for heat to generate.

If the 25 amp charger is a marine, new technology and claims very little heat generated its shorter charging time (say 1.5 hours) it would be more efficient than a much longer, 8 hour, changing time at lower amps with heat generated from the trickle charger which is a cheap auto charger.

It may just be a few cents per hours, but over 6 months a dinner with a few beers...


Mark
 

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Turns out your question wasn't simply put - we all were thinking you were asking about the efficiency of charging a battery with different chargers, where you were actually asking about the operating efficiency of the different chargers themselves. They are related, but not the same, and would have different answers.

Like already said, if your trickle charger is a cheap dumb one, the pennies you save on electricity won't pay for the new battery bank you may need in the end.

$0.30 USD isn't that outrageous - we are paying $0.23 in the US now, and have paid up to $0.47 in other countries.

Mark
 

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I have solar panels in a reasonably sunny position. But I need to augment that with a bit of shore power charging.

I only turn on any charger on demand and turn it off before fully charged (I get to fully charged on sunny days at least once per week).

So the question is does a battery accept charge better faster or slower?
It will be most efficient to allow the batteries to run down enough so that you can use your 25 amp charger AND it provides the 25 amps. Once the amps supplied drops below the 25 amps turn it off and allow the solar to do it's thing to finish the charging.

And accept that maybe you don't get 100% charged each day.
 

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Assuming zero load, which can’t be possible, the 4amp charger can only charge at a rate of less than 1% of capacity (4/500). If you’ve drawn your 500ahr bank down by 50 amps, it should be able to accept well more than 1%c. Therefore, if you can push in more amps, faster, the larger charger should be more efficient, because it will get you back to any level faster, then you unplug. That’s my logic.

Now, consider the “net” amps actually available for charging. The first thing a charger accommodates is load, then whatever is left is available for charging. This means the 4 amp charger is never fully, continuously pushing 4 amps. Makes the math all that more compelling for the 25, I would think.
 

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If the bank was never really drawn down and all you needed to do was accommodate loads of less than 4amps, or the low acceptance rate of very high states of charge, it would be a wash between the two chargers.
 

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Wow.

Yes, that is not expensive electricity, not at all.

Use the better quality charger, don't worry about "efficiency", just do what's best for the bank.

So the question is does a battery accept charge better faster or slower?
Trying to understand what you could be asking here makes my head hurt.

We need to know what make of battery you have and how big in Ah in order to estimate how many amps it will draw at what SoC.

However none of that has any bearing on your electricity bill.

Feeding 50A per 24 hours will cost roughly the same whether you are doing it fast or slow.

Obviously the 1A charger will run 24 hours a day and never catch up, and being a cheap automotive one, shoul be thrown away and never allowed to touch a good quality bank.

The 25A charger can do the job in 2-3 hours, but you should - if it is a good quality charger - never turn it off manually, never let your bank get drawn down any more than necessary, support your loads from that cheap shore electricity.
 
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