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Old 25-01-2019, 18:59   #1
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Charging with multiple battery chargers

I already have a 40A Pronautic1240p (identical to Sterling ProCharge) and 40 is not enough amps when using my Honda EU2000 on those days when the sky is overcast and solar alone won't cut it.

The batteries are six 6V 300A AGM Lifelines in 3 parallel strings of two 6-volt batteries in series to make a total bank capacity of 900 AH.

Usually I have a 100AH to 125AH deficit in the morning. I normally can charge completely with solar but occasionally need to use a small Honda 2KW generator. When I do this I do not fully charge the batteries; solar energy will top them up to 100%

Instead of upgrading to a very expensive charger, I propose to buy a second 40A charger and run them in parallel.

As far as I can tell from what electrical specialists are writing on the internet this should not be a problem. Since all charging sources (alternator regulators, solar controllers, and AC powered chargers) seem to use a maximum voltage (e.g. 14.4v), that should keep them all from overcharging or conflicting with each other.

Solar and my single charger play nice with each other. I can't see a problem with the dual chargers and it is far cheaper than buying a new high capacity charger; it also gives a measure of redundancy in case one of the chargers dies for some reason.

Does anyone see a problem with this?

Thanks,

Jeff
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Old 25-01-2019, 21:45   #2
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Re: Charging with multiple battery chargers

Not an issue. 80a will be pushing the 2000w gen. but should work. You won't be able to run anything else at same time.

I think the promariner you can link and they will work perfect together? But if not. Any 2 chargers with similar settings will work fine together.
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Old 26-01-2019, 07:36   #3
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Re: Charging with multiple battery chargers

Quote:
Originally Posted by pacific_voyager View Post
... Instead of upgrading to a very expensive charger, I propose to buy a second 40A charger and run them in parallel...
... Does anyone see a problem with this?
Chargers of the same voltage connected in parallel will increase amperage with no effect on voltage. For example, two 12V, 40-amp chargers connected in parallel totals 12V, 80-amps.


However, multi-charger applications can present challenges to chargers with built-in smart charge control technology. In this case, the charge controller manages the individual charger when the purpose of the series or parallel configuration is for the chargers to work together for total increased output voltage or increased amps. Chargers with built-in controllers can interfere with each other in their various charge stages of bulk, absorption, float, and equalization and the batteries may not reach full charge. In operations where auxiliary battery power is mission critical, chargers with built-in controllers can contribute to decreased battery performance and battery life. I believe your ProNautic 1240P may be just such a “smart” charger.

Best to consult with Pro Mariner Technical Support:
Phone: +1 603 433 4440
Email: support@promariner.com

The most reliable charging solution for mission critical operations in series and parallel configurations is to use an external charge controller that manages the entire charging configuration.
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Old 26-01-2019, 08:07   #4
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Re: Charging with multiple battery chargers

When you contact Tech Services, you might cite redundancy as your motive, not cost savings.
Parallel charging offers redundancy in “mission critical” operations, such as emergency response vehicles, mobile command posts, and mobile medical units, etc.
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Old 26-01-2019, 08:22   #5
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Re: Charging with multiple battery chargers

There is no problem at all doing this, even with completely diverse multiple sources.
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Old 26-01-2019, 09:41   #6
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Re: Charging with multiple battery chargers

I agree this could be a problem. In theory 2 identical chargers should output the same voltage but in practice I doubt it. Even a small variation in voltage could mean one charger putting out a lot less power. To be sure you need to look at chargers which are designed to work in parallel or find a way to spit the bank for charging.
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Old 26-01-2019, 09:41   #7
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Re: Charging with multiple battery chargers

There can be an issue with two very similar chargers attempting to operate at the same time. Typically one of the chargers will chop back a little too early when it sees the voltage rise from the other charger. They can also interfere with each others regulation. The issue is fairly easily addressed if you can tinker with the various voltages for each stage of charging.

The net effect is that when the batteries are first charged both chargers usually work well but say an hour into the charge as the battery voltage rises, they will do a bit of 'hunting'. You can get the same effect with a big solar array versus a battery charger.

I assume your using the chargers for the bulk phase so it should not be a practical problem. If you can set one of the chargers with slightly lower equalization and float voltages the two will play together nicely.

Very minor issue but perplexing if you watch near fully charged batteries and chargers showing erratic voltages.
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Old 26-01-2019, 09:50   #8
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Re: Charging with multiple battery chargers

Along those same lines, is it required/smart to protect one charging source from another? Specifically, if you have a solar controller (fed by multiple solar panels), a windgen controller fed by a windgen, and a AC Battery Charger, ALL feeding a common battery bank, do they need to be isolated with a blocking diode (Shotkey diode?) on each charging leg? When I installed the (4) solar panels, I was told to put a blocking diode on the (+) feed from each panel, so one panel would not try to backfeed another. With that same logic, should there be a blocking diode on the (+) feed from each controller (solar and windgen)to the battery bank? I'm assuming that when the AC Battery Charger is on it would overpower the solar and windgen controller inputs and they would show a '0' charge to the batteries. And if true, maybe the same would be true for using 2 AC Battery Chargers....if the charging (+) leg from each was isolated with a blocking diode each would act independently and their charge amps would be additive?
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Old 26-01-2019, 09:55   #9
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Re: Charging with multiple battery chargers

Quote:
Originally Posted by pacific_voyager View Post
I already have a 40A Pronautic1240p (identical to Sterling ProCharge) and 40 is not enough amps when using my Honda EU2000 on those days when the sky is overcast and solar alone won't cut it.

The batteries are six 6V 300A AGM Lifelines in 3 parallel strings of two 6-volt batteries in series to make a total bank capacity of 900 AH.

Usually I have a 100AH to 125AH deficit in the morning. I normally can charge completely with solar but occasionally need to use a small Honda 2KW generator. When I do this I do not fully charge the batteries; solar energy will top them up to 100%

Instead of upgrading to a very expensive charger, I propose to buy a second 40A charger and run them in parallel.

As far as I can tell from what electrical specialists are writing on the internet this should not be a problem. Since all charging sources (alternator regulators, solar controllers, and AC powered chargers) seem to use a maximum voltage (e.g. 14.4v), that should keep them all from overcharging or conflicting with each other.

Solar and my single charger play nice with each other. I can't see a problem with the dual chargers and it is far cheaper than buying a new high capacity charger; it also gives a measure of redundancy in case one of the chargers dies for some reason.

Does anyone see a problem with this?

Thanks,

Jeff
I parallel three of the Sterling equivalent to supplement the 100 amp output of a Trace charger. No issues. The three Sterlings behave as if they were one, and are designed to be in parallel.
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Old 26-01-2019, 09:56   #10
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Re: Charging with multiple battery chargers

If both chargers are smart then they can fight each other. Better I think to separate the banks with a simple switch and then set 1 charger on 1 bank and the other charger on the other bank. Monitor the charging voltages on each bank separately and when they are both full or on float, you can turn off the chargers and make the connecting switch again. You can then leave just one charger on for float as it will have little work to do now. Then they won't fight each other and you will have better control over the batteries and longer life too.
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Old 26-01-2019, 10:11   #11
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Re: Charging with multiple battery chargers

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Originally Posted by mikecambrai View Post
If both chargers are smart then they can fight each other. Better I think to separate the banks with a simple switch and then set 1 charger on 1 bank and the other charger on the other bank. Monitor the charging voltages on each bank separately and when they are both full or on float, you can turn off the chargers and make the connecting switch again. You can then leave just one charger on for float as it will have little work to do now. Then they won't fight each other and you will have better control over the batteries and longer life too.
Unnecessary. If the bank is LA, by the time voltage rises to the point where one charger might theoretically cut out, the acceptance rate has dropped to the point where it doesn't matter if one charger drops off. Besides, that charger is designed to be paralleled. I parallel with no adverse issues an alternator putting out 100 amps, a Trace charger and three Sterlings.
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Old 26-01-2019, 13:58   #12
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Re: Charging with multiple battery chargers

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If both chargers are smart then they can fight each other.
Yes completely unnecessary to consider any such factors.

Smart or dumb, no need to coordinate, no need for the units to be "designed" to be paralleled.

A very common belief, that, but long proven to be a myth.
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Old 26-01-2019, 13:59   #13
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Re: Charging with multiple battery chargers

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Along those same lines, is it required/smart to protect one charging source from another?
No none, not to worry, any types of charge sources, same or mixed.
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Old 26-01-2019, 14:21   #14
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Re: Charging with multiple battery chargers

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Originally Posted by Delfin View Post
Unnecessary. If the bank is LA, by the time voltage rises to the point where one charger might theoretically cut out, the acceptance rate has dropped to the point where it doesn't matter if one charger drops off. Besides, that charger is designed to be paralleled. I parallel with no adverse issues an alternator putting out 100 amps, a Trace charger and three Sterlings.
"If the bank is LA" LA ?? It'd be helpful if this forum had a glossary (I checked,no) for those of us who are not familiar with all the acronyms associated with the subject at hand.
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Old 26-01-2019, 14:27   #15
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Re: Charging with multiple battery chargers

Quote:
Originally Posted by Capt Gill View Post
"If the bank is LA" LA ??...
LA = (Flooded) Lead Acid
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