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Old 26-08-2009, 11:54   #1
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Multiple Charging Sources to the Same Battery Bank

I'm pretty sure that it's impossible for multiple regulators to be used on the same battery bank simultaneously. The reason is these regulator/chargers, solar, wind, etc. simply look at the battery bank voltage. As soon as they detect that voltage has increased above 12.8 volts (fully charged), they stop supplying power. In the case of multiple charging sources, that means when Charger A detects the voltage of the battery is above 12.8, it stops charging. However that battery voltage is due to charger B, not due to a fully topped off battery. Even things like the CenterFielder seem only able to direct the output of two charging sources to one of two regulators.

The issue with this is say you have a huge boat with massive solar panels and a huge 12v battery bank. The biggest MPPT out there will only allow 60 amps of output. You'd like to have two of them working together to provide charging to the same house battery bank. Is there a solution for this? Or on a simpler level wanted wind and solar to work together at the same time.
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Old 26-08-2009, 12:55   #2
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Hi,

the outback charge controller Flexmax 80 can deliver 80A per unit as MPPT and there can be multiple of them installed as far as i understood it.
I have a 600Ah 12V housebank and an outback 60A charger.
3 Sanyo panels wired serial can deliver up to 38A here in Portugal.

When connected to shorepower (but there is no need to) then it looks like the chargers compete against each other.
Then i use the shorecharger at night and solarpower during the day


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Michael
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Old 26-08-2009, 13:02   #3
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Hi Schoonerdog,

12.8V would be an atypical charging limit for a regulator. Most regulators go in constant current bulk mode until 14.2-14.8V are reached after which they go into a constant voltage mode and ramp the current down to stay at this voltage during the absorb phase before shutting mostly down into a maintenance mode at 13-13.5V.

If your battery bank is large, or if it has been drawn down some, it will not reach the 14.2-14.8 volts until quite a bit of the bulk mode charging has occurred.

If all of your charging sources have multistage regulators that are all set to the same charging regimen points (and you have a large enough, or sufficiently depleted battery bank), then all of them will put out all they can during the bulk charging stage.

When bulk charge is reached, then they may start to play against each other and the output of one charging source might shut down the output of another due to slight variations of the regulator set points and how charge is sensed. But now it doesn't matter because your batteries cannot accept the higher current of all your charging sources and as long as one of those sources can supply the absorb current, all is well.

In fact, it is dandy if you have multiple charging sources. For example, if you are in the absorption phase of the charge cycle and your solar panel regulator has shut down your wind generator regulator and is supplying the entire absorption charge, then when clouds decrease the solar output, your wind generator will step in and shut down the solar regulator and continue the charging regimen.

We have 480W solar, a 125A AC charger and two 60A engine alternators as charging sources. The solar and AC charger regulators are set to the same charge points. When the AC charger is on and it is sunny, both the solar and charger regulators contribute full on when the batteries are low. When the absorption voltage is reached, the AC charger regulator over-rules and the solar regulator shuts down the panels completely. When the charger is turned off, the solar regulator immediately comes back on line and continues the charge regimen.

The only true conflict for us is the engine alternators. They are internally regulated and ramp down output at 13.8V. So when it is sunny and we are motoring, the alternators shut down before bulk charging is complete even though the batteries can take more charge than the solar is providing. I put a diode and switch in line with the alternator sense wire to drop the voltage 0.5V which helps a lot in keeping the alternators on-line during the bulk charge phase.

Long story short: make sure your charging source regulators are set to the exact same points and they will all play nice together until you are sufficiently charged that it doesn't matter if they interfere and swap roles with each other.

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Old 26-08-2009, 13:14   #4
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this question peaks my interest as well. i have a 30ft rawson with 2house batteries and 1 start battery. the alternator is only a 40amp i believe so my question here is can i run my honda generator to the 110charger while im motoring ? will this allow me to charge my batteries at a faster rate ?
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Old 26-08-2009, 13:41   #5
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Will your generator run a 110A charger? That will depend on which charger and which generator you have. If so, there should be no problem running it while motoring. Your alternator will most likely shut down its charging when the 110A charger is running.

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Old 26-08-2009, 13:43   #6
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Multiple Controllers Linked Together / Duo-Charge Controllers

Quote:
Originally Posted by schoonerdog View Post
Is there a solution for this? Or on a simpler level wanted wind and solar to work together at the same time.
schoonerdog,

The short answers:
1) Most high-end MPPT controllers DO allow for multiple controllers to be connected to a battery bank (sharing the charging), and be "linked" together, so they operate as one large controller.....

I installed my two Blue Sky 2512ix MPPT controllers exactly that way, and they've been working fine for almost 3 years now.....
See Solar Panels for photos and article about my 520 watt solar array and installation....

2) The main problem has always been connecting multiple charge sources, such as wind and solar, together and having them (and their charge controllers actually work......typically it doesn't work....
So, many have simply switched off the wind gen during the 5 - 6 hours when the solar array is producing its maximum power......and then allowing the wind gen to do its job as the sun is setting....

Many have struggled with this problem, and some have tried to solve it....
Blue Sky Energy has come up with a fairly decent solution......one that is elegant in its simplicity, but also very efficient......
It allows for FULL MPPT output of a solar array, and at the same time allows whatever power the wind gen is capable of producing in the curent wind to be BOTH supplied to the batteries for charging......
(this of course assumes that the battery bank is large enough, and at a sufficiently low state-of-charge, to accept all of this charge current....)

Have a look at their new Solar Boost 30124il Duo Blue Sky Energy Inc. | Solar Boost 3024iL DUO

Also have a look at the entire Blue Sky website.....
Blue Sky Energy Inc. - Industry Leaders In Solar Boost Charge Controllers and Maximum Power Point Tracking (MPPT)


3) Blue Sky also has controllers, such as my 2512ix's, that have "aux" battery charge outputs which allow up to 2 amps of charging to an "aux" battery (such as staring battery, etc.).....


4) Although the specific voltages you write about are off the mark, your point is VERY valid.....
Which is why I'm answering your questions...



Gosh, I know I sound like a salesman for Blue Sky....but I'm not.....just a happy customer.....

Sunny skies and fair winds...

John
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Old 26-08-2009, 13:46   #7
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dog, AFAIK it comes down to kludges, coincidences, and "if". But nothing I've been able to find has been designed to actually itegrate (as opposed to switching off or dumping) multiple sources to one bank at one time. Especially when one source is a generator type that needs to be dump regulated, while the others are alternator/solar type than can be used more elegantly.

If anyone is making "one ring to rule them all" they need a marketing program to let the world know about it.
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Old 26-08-2009, 14:08   #8
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OK, from one of the leading makers of MPPT controllers, Outback, specifically, their back end engineering.

You are indeed correct; one controller will stop harvesting from the array when it sees another source applying power to the batteries. As you probably already know, we advise to call the batteries manufacturer to get your batteries proper absorb voltage, float voltage, and if you EQ (charge algorithms). Obviously, the larger the battery bank, the longer the time your going to want to absorb. The absorb time limit is adjustable, but the float time limit isn’t. Where I’m getting at with this is, the controller does not read state of charge at all. They do not know how many amps have left in your bank and what is needed. The controllers do not know how much of your battery charge is left (state of charge); it solely look at the batteries voltage.

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Old 26-08-2009, 14:21   #9
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Now to charging voltage, a fully charged battery is around 12.7 volts. However, to fully charge a 12 volt battery we must slowly raise the voltage of the battery to approximately 14.5 for a wet cell (lead-acid) battery or 14 volts for a sealed, maintenance free or gelled cell battery. Once the battery terminal voltage has been brought up to 14 or 14.5 volts and held there for a period of time we can say the battery has been fully charged. Once we stop charging the battery and allow the voltage of the battery to “settle” it will drop down to the 12.7 volts mentioned earlier.

All of that though is just back ground. A charge controller will periodically back off and try to sense the battery voltage to determine how many more amps it needs to kick in. So it's charging happily away, raising the battery voltage from 12.3 volts to it's particular bulk charging voltage (say 14.5 volts). It then backs off to see if the battery is still needing bulk charging. If the battery bank is still very depleted AND you have no other charging source, it will see the battery is now say 12.35 volts, and then close it's eyes so to speak and start putting out everything it has again (bulk charging). BUT, if you have another charging source, when it backs off the voltage, the voltage of the battery bank will stay at 14.5 volts, held there by your second charging source. Your first source knows nothing of this second source (let's uncomplicate this by saying that we've got two disparant systems like solar and wind). Your first source now sees the battery voltage is 14.5 volts when it's not putting anything it and it backs completely off (sleep mode, etc). Obviously if you have a 1000 amp hour battery bank with a 500 amp hour deficit and you have two solar chargers that can put out a maximum of 80 amps each (that's the highest MPPT made) or a solar that can do 50 and a good windy day is giving you 20 from your wind generator, you want them BOTH to be charging. But one precludes the other.

So then two questions, what, if anything, can take both of them and either combine them into one virtual regulator, or if that isn't available what units can be combined through interconnects to be aware of each other and thus act as one unit. Maybe blue sky has such an interconnect?
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Old 26-08-2009, 14:25   #10
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Absorbtion Charge Time

Quote:
Originally Posted by schoonerdog View Post
The absorb time limit is adjustable, but the float time limit isn’t.
schoonerdog,

The Blue Sky MPPT controllers have the same adjustments, allowing you to adjust a set time, AT a set voltage (adjustable, but default is 14.4v).....

Not sure if you saw my answers above.....
If not, please have a look....you will find them useful and accurate...

Have you looked at their website????
Blue Sky Energy Inc. - Industry Leaders In Solar Boost Charge Controllers and Maximum Power Point Tracking (MPPT)
and looked at their Duo-Charge unit, which I believe is shipping this week or next.....
Blue Sky Energy Inc. | Solar Boost 3024iL DUO


John
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Old 26-08-2009, 21:37   #11
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"The [Outback] controllers do not know how much of your battery charge is left (state of charge); it solely look at the batteries voltage. "
Now, that's interesting because the BlueSky controllers, at least some of them, are PROGRAMMED by the installed with the amp-hour capacity of the battery bank. I would probably be rash to assume that information is used by the microprocessor, in conjunction with the voltage level of the battery, to determine just how full the battery is or isn't.
Anyone know?

The BS controllers, by the way, aren't "three stage" at all. Rather, they apply all the amperage that they can develop at a certain amount over the battery voltage. So you may think you'd see 14.4V during bulk charging, but the controller display will show 13.2V or some other figure that seems very wrong. But, that allows them to pump in more amps, boil less electrolyte, and in theory charge very much more efficiently.
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Old 26-08-2009, 22:22   #12
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Hellosailor,
Quote:
So you may think you'd see 14.4V during bulk charging, but the controller display will show 13.2V or some other figure that seems very wrong. But, that allows them to pump in more amps, boil less electrolyte, and in theory charge very much more efficiently.
That is, unfortunately, not how it works. You see 13.2V during bulk charge because the controller can't deliver enough amperage to get the voltage up higher (the load of the battery pulls the voltage down). This is how every bulk-phase works: maximum amps with rising voltage until the voltage reaches the defined upper limit, like 14.4V.
When you never see the voltage higher than 14V during bulk charge, it means you never charge your battery past bulk mode, or the settings are wrong, or the controller is broken. It has nothing to do with a system to get in more amps or boil less electrolyte. You must go to that higher voltage of 14.2 or 14.4V in order to charge a 12V battery.

After bulk phase, they switch to absorption mode, which means that the voltage isn't raised any higher and the amperage will come down as the battery gets charged more.

About programming Ah capacity: that is because the charger does look at the amperage going into the battery. There is a relation between the total Ah capacity of the bank and the current that is still accepted when the batteries are full. This way, without recording how many Ah's went into the battery, a charger can know when the charging is done.

About multiple charge sources: If a charger/controller momentarily stops charging to sense the current voltage level in order to decide to continue or not: this is just fine. When the other source is able to keep the voltage that high, it means that it doesn't need another source for maximum charging current. If the source that stops for sensing is needed, the voltage will drop and it will resume. Of course there is an overlap area, but that is past the bulk phase.

You must remember that a charger is not a power supply with a fixed and stable voltage. In bulk phase, it is a constant-current source, meaning it will provide it's maximum output current for as long as the voltage is less than the programmed value like 14.4V. After that, the charger does go into a constant voltage mode. Until the battery is almost fully charged, it is the battery that determines the voltage on the circuit. This is because it's putting so much load on the charger, that the charger can't maintain the voltage (it just drops). This is just like your battery voltage dropping when you switch on a high load.

cheers,
Nick.

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Old 27-08-2009, 04:29   #13
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Good post, Nick!

Anyone interested in batteries, charging, and control/monitoring, might be interested in some of these earlier discussions, paying particular attention to Rick’s expert advice.


How "fast" you can reliably charge your battery.

Understanding a model for battery charge acceptance

Lead-acid battery equalization

Basic Battery Question

Charging Capacity & Time to Recharge

3 stage alternator regulator logic

Battery-Charging Voltages
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Old 27-08-2009, 04:46   #14
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Quote:
Originally Posted by schoonerdog View Post
I'm pretty sure that it's impossible for multiple regulators to be used on the same battery bank simultaneously.
Just to address this original comment in another way - we have two alternators with two separate and independent regulators feeding our battery bank and it works just fine.

When the charging starts and the bank is low, both regulators will be in bulk mode and pumping out their maximum amps trying to bring up the voltage to 14.6 (in our case with wet deep cycles). They don't 'fight each other' at all. When they are able to bring up the voltage to 14.6, they flip into the programed 3 hr absorption mode and then one of them does typically do most of the work,staying at a high amp output, keeping the voltage up at 14.6 while the other one tappers off its charge amps.

But the simple message is we have been using two separate regulators feeding the same bank for a decade. It does actually work and there are no tricks to it.
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Old 27-08-2009, 06:13   #15
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Solar and Wind charging...

Nick and Evans,

Like gord, I want to thank you for your wonderful posts.....
Just wish I could write that elegantly......

My comment on multiple charge sources not typically working well together was directed at wind (where many have a "divert load" controller), and solar (where you're likely to have an MPPT controller), not working well together......
Of course my personal experiences are primarily with solar only.....
So, maybe I should've kept my mouth shut...
But, since most of my charging is in accpetance / absorbtion, rather than bulk, perhaps my opinions are shaded by that????

While I could be wrong, and please correct me if I am, when an MPPT controller with sufficient solar power drives the voltage up, then a wind gen divert load controller simply diverts the wind gen's output.....(or even the other way around, should the wind gen be a large one and the solar array small....)
Yes, this may only happen when you've reached the acceptance mode voltage.....but, I read of many with both wind and solar power who do experience this trouble....


Sunny skies...

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