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Old 05-07-2013, 09:46   #1
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Can you combine multiple chargers to charge?

I have both Prosine 2.0 and a Dolphin 20amp charger.

The boat currently has 1020 amp/hr capacity from LifeLine AGM's in 4 8D's.

When I turn both chargers on at the same time, for 15 minutes they both seem to work together. After 15 minutes the Prosine panel shows that charging amps start to fall from the typical +105 amps going into the batteries. Usually it takes over an hour for that to happen. Is the current coming from the Dolphin starting to make the Prosine think the batteries are filling and therefore make the Prosine shift down to the 2nd stage of charging? After the prosine starts changing its charging voltage higher, the Dolphin shuts off completely.

Can the Dolphin be programed to run just like the Prosine so that I can charge my AGM batteries faster? When using the genset, I'd like to utilize more available amps and charge the batteries faster.

I'm not sure why the former owner put the Dolphin charger aboard. Could it be because he sailed internationally and the Dolphin is flexible on input cycles and voltages?. I plan on sailing abroad as well.

Mark Powell
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Old 05-07-2013, 20:21   #2
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Re: Can you combine multiple chargers to charge?

Mark,

From what you've said in this thread and the other one, it seems that your charging system is WOEFULLY UNDERPOWERED for even the existing house bank (1020AH Lifeline AGM 8-Ds), much less what you are discussing about increasing that size to 1500AH.

Forget the Dolphin charger. It's merely an annoyance. Concentrate on the major sources of charging. Think about adding big solar panels and a good MPPT controller.

AGMs like to be fully charged frequently. If they're not, they will quickly lose capacity. Mechanical charging systems (generators and engine-driven alternators) are unlikely to do the job of fully charging the batteries, because it takes many hours to do that and would be very costly, not to say annoying and impractical.

Your 1020AH house battery bank when 50% discharged will easily take over 1,000 charging amps for awhile! You're only able to supply about 10% of that with the genset/Link setup.

My suggestion is that you look at ways to beef up your charging capability, and forget enlarging the already formidable house battery bank capacity.

BIG alternator, maybe. Big solar panels/MPPT controller surely. Wind generator, maybe.

Also, it would be useful to develop an energy budget and look for ways to cut your consumption. Remember, every watt you take out of your batteries has to be replaced somehow. The way you're now set up, that is both costly, noisy, and very time consuming.

Bill
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Old 05-07-2013, 20:38   #3
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Re: Can you combine multiple chargers to charge?

You can't custom tailor the charging curve on chargers so that both chargers have exactly the same curve.
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Old 05-07-2013, 22:12   #4
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Re: Can you combine multiple chargers to charge?

My system is 24v, but the same principal applies.
When I upgraded my house bank in 2008 from 400Ah to 1040Ah, I added a new Victron 70amp (24v) charger to the existing 50amp.

With a larger bank that meant less % draw in 24 hrs.
I did an initial test of charge rates combined and then every hour I shut one off for about 5 minutes to see what they were doing individually.

The interesting part of my spreadsheet is line 39 to 40 where 10% draw in 24 hrs. can be replaced up to absorption level (80%) in only 2 hours with both chargers working.
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File Type: xls Charging Tests.xls (25.0 KB, 35 views)
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Old 06-07-2013, 08:01   #5
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Re: Can you combine multiple chargers to charge?

Quote:
Originally Posted by btrayfors View Post
From what you've said in this thread and the other one, it seems that your charging system is WOEFULLY UNDERPOWERED for even the existing house bank (1020AH Lifeline AGM 8-Ds), much less what you are discussing about increasing that size to 1500AH.
His Prosine has a 100A charger. Although the AGM's may be able to take 1000A in bulk, it is unreasonable to achieve this in practice. This would involve stacking several large chargers. Solar and wind are not going to get anywhere close to that, and forget alternators all together.

Solar and wind are good for providing topping off charging once the mains charger gets the batteries well into absorption.

I agree about forgetting the Dolphin all together. The extra 20A is not going to be of much practical use.

However, if your battery SOC is low, then the two chargers should not have any problems working together providing full output. It sounds like your batteries are reaching absorption voltage and the Dolphin voltage is a bit higher than the Prosine and shutting it down. If you want to use the Dolphin also, just shut it off once absorption voltage is reached and let the Prosine take it from there.

Either the boat came with the Dolphin and the Prosine was added later, or the Dolphin was added simply as an inexpensive backup.

Do you know your actual typical daily electrical usage? It may not be so high as your battery capacity suggests. The issue with the two chargers also suggests that your batteries are not being taken down to low SOC.

Mark
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Old 06-07-2013, 09:12   #6
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Re: Can you combine multiple chargers to charge?

As a basic answer, yes you can combine chargers. A charger doesn't "know or see" another charger, all it sees is a battery voltage.

In the bulk stages they are going to put out maximum so there is no problem.

When one of the chargers sees a battery voltage that causes it to switch to the next stage, you will have a period where the one that changed is doing very little and the one that didn't is doing the bulk of the work until it finally reaches its next transition.

So the bottom line is charging may take a little longer since there are times when you really only have one working.
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Old 06-07-2013, 10:29   #7
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Re: Can you combine multiple chargers to charge?

"As a basic answer, yes you can combine chargers. A charger doesn't "know or see" another charger, all it sees is a battery voltage."

I'd agree with you, but what happens when there are two chargers, each putting out a nominal 14.4 volts, connected to one battery bank?

IF the bank is so depleted and so large that it can pull down the chargers to a lower voltage, great, each of the chargers "sees" just the lower voltage and keeps putting out. But what happens if the chargers are using new digital circuits and really, they are still putting out 14.4 volts no matter how hungry the battery is?

Doesn't that set up the opportunity for the chargers to be deceived by steady voltage, or pulses, from each other?

I confess that the rash of "new" smart chargers has me befuddled, especially the "safe" ones that will not put out any current if the battery voltage is below ~10.6 volts. Supposedly they do this for safety reasons. RFPITA, to this fossil.

Odds of digital (as opposed to old school simple transformers) chargers messing with each other's tiny little silicon minds?
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Old 06-07-2013, 10:53   #8
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Re: Can you combine multiple chargers to charge?

Chargers don't put out VOLTAGE, they put out CURRENT. The voltage that they see is the level of charge that current has established in the battery by charging it.

There is no such thing as a "charger with new digital circuits that puts out 14.4 volts no matter how hungry the battery is".
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Old 06-07-2013, 16:36   #9
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With the greatest respect " hellosailor" I think its best to leave the electronics to the experts. as you say yourself you area" befuddled"


Multiple charging sources can be paralleled , however unless they have current sharing circuits, they will not neccessarily proportionally share the load. In bulk mode because the battery is a very impedance , all charge sources will output as much current as they are capable of. as the battery terminal voltage rise as it approaches absorption , the charge source will begin voltage regulation, each source will regulate at slightly different voltages , so the one that's regulates higher will do the brunt of the absorption mode charging

Bulk mode will be faster but absorption mode charging could be slower depending on which source is doing the work.

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Old 06-07-2013, 23:01   #10
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Re: Can you combine multiple chargers to charge?

Andina, my adminttedly uninformed opinion was that the Delcotron alternators, and the logic they were built with, were very much still with us.

"There is no such thing as a "charger with new digital circuits that puts out 14.4 volts no matter how hungry the battery is".

A Delcotron integrally regulated alternator (standard GM/Delco issue in the 1970's) was designed to put out exactly and only 14.3-14.4 volts. It would send out something like 10-10,000 pulses per minute, and in between the pulses it would listen, over the same charging wire, to measure the state of charge of the battery.

If the battery was holding 14.3 volts, the Delcotron might only turn on ten times per second. If the battery was holding 13.2 volts, the Delcotron might turn on 5000 times per second. Each time it turned on, it shot a pulse of 14.3-14.4 volts at the battery. Never more, never less. The CURRENT never was varied. The frequency of the pulsing was varied, the current was fixed. The voltage was fixed. Only the pulse frequency varied.

Delco was quite proud of this design.

So there's a lot of stuff out there. In comparison, I know a lot of Hitachi alternators are regulated to put out anywhere from 13.6-14.4 volts, a very wide and sloppy range by comparison.

Most of the alternator companies won't discuss what they are doing with the public these days. Some of the Japanese won't even provide output curves, because that's proprietary information to their customer, in their logic.

I'm not motivated enough to spend time with a scope trying to figure out how who's tys work these days, I only know they have met Heinlien's Rule: Any sufficiently advanced technology will be indistinguishable from Magic.
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Old 07-07-2013, 11:01   #11
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Re: Can you combine multiple chargers to charge?

If a battery is at say 12.2 volts and you have a 40 amp charger that "puts out 14.2 volts" it would have to be able to supply (14.2-12.2)/0.00125 = 1,600 amps to maintain 14.2 volts (for an 800 cca battery). It may attempt to put out 14.2 volts but current will be limited to the maximum available and the voltage will be the at rest voltage + max current x battery impedance, = about 12.25 when it first turns on, not 14.2.
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Old 08-07-2013, 14:27   #12
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Re: Can you combine multiple chargers to charge?

Thanks for the help guys. You basically told me what I needed to know. Using both chargers may help for 10-15 minutes but as soon as I see the Prosine panel start to drop below the startup +105 amps into the batteries, I will be better of shutting off the smaller charger. It is really good to know that it won't damage either charger.

We typically use approximately 300 amps each day. The Lifeline charging recommendation is (300a / 105a/hr) + (2 hr) = 5 hrs each day. The reality is that my wife uses the washing machine and we make water for about 2-3 hours/day anyway. Add in some air-conditioning in the heat of the mid-day sun and we are already Charging/generating for 4 hrs per day.

Certainly, solar panels and/or a wind gen would be great tools to top off the batteries to keep them full as they desire. But, for us, changing out batteries every 3-4 years instead of 6-8 because we don't recharge them long enough to reach an injection current of 0.5% of capacity (5 amp rate for 1000a bank takes about 5-6 hours of generator time) beats the noise and aesthetics of solar and wind gen top off methods to us. We are planning to spend the kids inheritence anyway.

Mark
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Old 08-07-2013, 16:50   #13
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Quote:
Originally Posted by hellosailor View Post
Andina, my adminttedly uninformed opinion was that the Delcotron alternators, and the logic they were built with, were very much still with us.

"There is no such thing as a "charger with new digital circuits that puts out 14.4 volts no matter how hungry the battery is".

A Delcotron integrally regulated alternator (standard GM/Delco issue in the 1970's) was designed to put out exactly and only 14.3-14.4 volts. It would send out something like 10-10,000 pulses per minute, and in between the pulses it would listen, over the same charging wire, to measure the state of charge of the battery.

If the battery was holding 14.3 volts, the Delcotron might only turn on ten times per second. If the battery was holding 13.2 volts, the Delcotron might turn on 5000 times per second. Each time it turned on, it shot a pulse of 14.3-14.4 volts at the battery. Never more, never less. The CURRENT never was varied. The frequency of the pulsing was varied, the current was fixed. The voltage was fixed. Only the pulse frequency varied.

Delco was quite proud of this design.

So there's a lot of stuff out there. In comparison, I know a lot of Hitachi alternators are regulated to put out anywhere from 13.6-14.4 volts, a very wide and sloppy range by comparison.

Most of the alternator companies won't discuss what they are doing with the public these days. Some of the Japanese won't even provide output curves, because that's proprietary information to their customer, in their logic.

I'm not motivated enough to spend time with a scope trying to figure out how who's tys work these days, I only know they have met Heinlien's Rule: Any sufficiently advanced technology will be indistinguishable from Magic.
The original Delcotrons had a mechanical relay regulator. This essentially pulsed the alternator just like you said , As did the later solid state versions of it , it didnt put out 14.4 , only when the battery allowed it to do so ( ie nearly fully charged ) it operated on similar lines to the current crop of crude PWM solar regulators

Its been well surpassed by modern regulators

Dave
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