Xantrex C60 as a 12V charger from 24V battery bank

Iya · August 2009

Hello Everyone,

Been a long time.
If I may ask for advice please....

I am thinking to use a Xantrex C60 charge controller to charge 12V battery bank but power source not from PV, it will be from a 24V battery bank.

Why I decided this way is :

The application is for a wooden motorized sailing boat. The main engine is a 24V starting system and so 24V DC is the voltage to go as domestic battery bank voltage since the alternator is 24V.

However the VHF and SSB radio always requiring 12V DC supply. So there must be a 12V radio battery bank regardless.

I have seen DC to DC converter for such application and I was thinking, for a bit of more money, the Xantrex C60 can be a DC to DC converter and a smart charger at the same time and 60 amps is decently big.

The 24V domestic battery bank will have powerful marine charger using 230V, somewhere in the region of 60 to 90 amps and the battery bank will be about 400-600 amps, approximate.

The idea is, when all generators are down or if the 24V battery charger is down, I still have the main engine alternator feeding the 24V battery bank. Hence even if I get a dedicated 12V marine battery charger for the radio battery bank, the Xantrex seems like a good back up to have and a good primary system to rely on, if....(only if ) it will work when set up as I intended.

However, page 7 & 8 of the owner manual, makes me worried.

Page 7
If the PV array’s output increases above the rated amp level
due to reflection or “edge of cloud effect,” the controller will
continue to operate until the heatsink reaches a maximum
safe operating temperature. This will take several minutes to
occur, depending upon the ambient temperature involved.
When the heatsink reaches the maximum safe temperature,
the controller will reduce the current, cooling the transistors
and the heatsink.

Page 8
If the current from the PV array reaches 85 amps, the
controller will turn off to protect the circuitry. In the event of
a shutdown, the controller automatically resets itself after
10 minutes (if overcurrent condition is no longer present).

Page 7 info is a common design of a charger, I will install a extra fan no worry.
Page 8 info is scarry. With a planned 200 amps 12V radio battery bank, it is easy to hit 85 amps during initial charge of a rather depleted battery bank.
I am only familiar with marine battery charger and quite blind on solar charge controller. However I really envy the advance design and capability of good solar charge controllers in the charging section of it.

What I am trying to understand is how will the Xantrex C60 "sees" a battery bank compared to a PV.

A PV is limited in its output, no matter what happens it will never go much above its spec.

A 24V lead acid battery bank is different, it can easily allow 200-300% of its amperage rating for engine starting or anchor windlass operation. If the Xantrex "sees" this 24V battery bank like a huge PV or worse a hydro...I will be screwed....

If I set the C60 to a Load Controller Mode, I then might as well get a DC to DC converter.

Confused....confused.

Thank you guys.

Regards,
Iya

Solar Guppy · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

DON'T DO IT, the C60 is NOT A DC to DC converter!!!!!

The C60 is a PWM controller ... basically it connects the input to output directly ... using battery's, you will short your 24V battery to the 12V one and blowup the controller is the best case , worst case will be a fire

Iya · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

Ok Chief,..... got that. This is what worries me.
Thank you very much.

Regards,
Iya

mike95490 · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

Additionally, this would run the main starter batteries down too.

What about adding a 12V alternator onto the engine?

Cariboocoot · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

Yes, you need to either use an MPPT type controller or a true DC to DC converter or ...

Check the wiring. Many 24 VDC start/charge apps in industry have center grounding. That is to say, there is a -12V and a +12V relative to chassis ground. This is done so that loads like lights can be run from the chassis to +12. Unbalancing the charge isn't really an issue, as the 12V loads are usually low current, especially compared to the starting system. If this is not specifically present but there are two 12V batteries in series you can "center tap" it yourself. Providing the loads aren't significant, it shouldn't unbalance charging.

Iya · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

Really thank you so much guys....

I will answer one by one :

Mike,
Adding additional 12V alternator is a possibility but it will be more work on the mechanical side and the way I see the belt arrangement on the engine, it will be a lot of work and I may need to add another pulley. Besides, an alternator, unless very special ones are not as smart as any typical 3 stage battery chargers.
The idea is to make use of the 24V domestic battey bank to the fullest.
The vessel will have its own 24v starting battery banks. I have an electronic split charging unit than can charge 2 battery banks separately without the typical diode voltage loss of 0.4 to 0.6 volts.

Money for money, it will be cheaper to use a DC to DC converter and a separate 12V battery charger powered from a 230v AC and less wiring headache from engine room to helmstation.

Cari,
OK, I will look into an MPPT solar charger as a possibility.
I just downloaded Outback 60 amps data and still studying it.
I have emailed MorningStar asking the same question and if their MPPT can do it, I hope they will write back to me.

Most marine switching type battery chargers ( not a big transformer type ) are dedicated 12V or 24V units by design ( at least those I opened to see ) since they are not multi pupose charger like industrial one where it can do 12/24/36 and 48 volts.

However, a few big ones are actually 2 or 3 unit in one being parallel. I had an opportunity of looking at a 180 amps 24V unit from Italy ( can't remember the brand, its custom made ). 3 of 60 amps module paralled. I hate this kind of charger. The vessel using it , so happen needs constant 120 amps minimal for DC powered engine room blowers (4 units ) and one of the module I suppose has higher battery voltage output by a bit after so many years in operation and never calibrated....this module always turned itself off due to auto overheat shut down. The rest of the two 60 amps modules being juiced out maximum power will also shut down minutes later.....zero charging in the end. The vessel at that time had faulty 175 amps alternator.

I really really envy solar charger controllers. They are so flexible, so adjustable and so smart, compared to marine battery chargers even the so called smartest one.

Sorry for the rant...

Thanks ALL,
IYA

Cariboocoot · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

Iya;

The charging system may be dedicated 24V, but are the batteries? If you've got two 12V in series to make 24V, you've got 12V. It's just a question of if the 12V loads would put too much strain on the one battery.

Iya · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

Hello Cari,

Yes, I done this type of taking of 12v from 24v battery bank but it was a very small load, less than 5 amps from a 200 amps bank and it wasn't countinuos operating appliance.

Depending on radio traffic, the SSB will need about 11-12 amps at transmit. the VHF will take 4 amps at the most and this will be more frequent use than the SSB. At standby these two radios should not take more than 1 amp.

I shall take note of the 12V taking from 24V as part of back up, many thanks for the reminder.

I looked at Outback 60 amps MPPT, it looks like an efficiency of 95% do able based on 24V input to output 12V at 500 watts and still +-93% at 1000 watts.
Let me ask the manufacturer for my intended use and see what they will reply.

I really would want a solar charge controller, so that when one day I decided to install a PV on the boat, the basic system is already there.

Mike had a point too, during float charging to the 12V battery bank, I need to know what is the drain an MPPT charger will consume from a 24v battery bank.
More confusion..........

Thanks Cari...

Regards
Iya

Cariboocoot · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

MX 60 is a good unit (I have one) but big and heavy - be sure you have space for it.
If the 12V is in float, the draw from the 24V bank would be minimal: basically whatever the load requirements are. Chances are the 12V is 100 Amp/hr? In which case it would only need, say, 10 Amps charging current. This plus the current draw of whatever devices are in use will be the key factors in the load on the 24V bank. Even at half the MX 60's capacity that would be around 15 Amps off the 24V.

Cautionary note: lots of people here have talked about using an MPPT controller in this manner. To my knowledge, no one has done so. Manufacturers will likely err on the side of caution and tell you not to, as it is not intended use. Yet most of us see little difference between 24VDC sourced from a solar array or sourced from a battery bank.

Maybe start with a cheap one?

Just in case something goes "fwoom!"

Iya · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

Gee, I did not know many people have talked about doing the same thing.
I tried the search function but could not narrow it down. Sorry it this question were asked a few times before.

Money lost on charger is OK, if there is fire hazard and this boat is wooden motorized sailing boat............dang I will hang myself....

I see the limitation of MX60 maximum output is based on NEC ruling.

Has the MX60 today resolved its noise interference to radios issue ?

I been last in this forum like over a year ago and this noise issue to radio units was mentioned. Are you using any sort of radio with your MX60 ?

Thanks Cari.

Iya

Cariboocoot · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

Iya;

I've never had any radio noise trouble, but then there are many different kinds of radios. You mentioned SSB - Single Side Band, right? Compress the signal onto one half of an AM carrier wave! Depending on the operating frequency, different radios are more/less likely to pick up RF interference. This would, I think, especially be a problem on a boat where there is no Earth ground.

Perhaps the new FM80 solves these issues? I don't know; I'm not an Outback expert.

There are a couple of guys on this forum who probably would know: crewzer &/or boB.
Are you listening guys?

Maybe send them a PM with that question.

Iya · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

Cari,

Morningstar just got back to me....that is FAST !!! In less than 2 hours. Bravo to Adam Kehlenbeck of Morningstar.

PWM used as DC to DC converter...no way he said, same as what Solar Guppy mentioned. The PWM will deliver maximum current all the time.
MPPT type also not reccomended....hick hick hick.

Looks like I will have to use "stealing 12V from 24V bank wiring" and/or DC to DC converter and a 12V/20A battery charger with a 200 amps battery bank.
With 3 way selector switch, two poles type to disconnect the minus, I should be able to have 3 power supply variations for worse case scenario.

Yes, SSB ground on boat not as good as on land but I will place big ground plates on the hull. I don't understand much of SSB, they are much more complex than VHF but they are sure much sensitive to interference.

Thanks again everyone....1 dream down....will think of others later. Ha ha ha.

Regards,
Iya

Cariboocoot · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

This is probably the simplest and cheapest way to do it:

http://store.solar-electric.com/12to24or24to.html

Less expensive than an MPPT controller and acually designed to do the job!

Good luck with your project.

Photowhit · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

I'm not sure why you don't want to use a DC to Dc converter, If you "go solar some day, you'll still have a 24 volt charging source with your motor and need the 24 volt system to start the motor, so I'd guess you'd run a 24 volt solar array.

I haven't heard that Converters have any noise problems. I believe they draw as needed, don't know that for a fact, I'd guess there is some base line draw.

NWAS Link - http://store.solar-electric.com/sa24voto12vo.html

Iya · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

Hello Cari & Photo,

YEP, looks like no choice but a DC to DC converter as simplest way but it will stay as alternative, not primary power source. Thanks for the link guys.

I just surfed for a DC to DC charger and there is such a unit : http://www.powerstream.com/DCC.htm
But its is too small at 7.5 amps. I will check with manufacturer if they have bigger ones. 20 amps minimum is what I am hoping for. I will ask them on how the system actually works.

Photo,

Why I don't really like DC to DC converter for radio because when I use it, I can't connect its output to a radio battery bank, to allow the battery to act as buffer. I am not an electrical engineer, but if that DC to DC converter output exceed battery voltage, current will flow into the batteries and the converter will be working hard as a charger and short lived...I guess. The same reason Morningstar does not reccomend me using MPPT as DC to DC charger.... I think.

If it can do charging, I can then hook it up to the battery bank and enjoy second charger capability ( will use a switch to isolate both charger units output if required ) and get to use the 12V battery bank all the time. It will be such a waste if I can not excercise that 12V radio battery bank. By being used often the 12V battery will also be taken care of more often.

In the event of a 24V supply failure, I still can use the 12V battery bank without needing to switch sources ( DC to DC converter or 12V Battery Bank with charger ).

In most cases, a captain of the vessel will keep that power source switch in DC to DC converter source because the natural choice is to use a power source which is always maintained. Naturally is the 24V domestic battery bank because it feeds the lights too. Dim lights always matter to everyone on board. In an emergency, if the DC to DC converter got fried and vessel also in some sort of other emergency, most likely he will forget that there is a 12V battery bank available, as he thought both SSB and VHF radio are dead thru mailfunction. A DC to DC converter failure will result in dead radios. A failure of DC to DC converter with charging capability and hooked up to a battery bank, will result in low voltage situation after at least a few hours later, but not immediate radio death. Emergency situation sometimes do funny things to people, they tends to forget things.

By having a DC to DC converter charger capable connected to a battery bank, I can install low voltage alarm as reminder or that dimming of display backlighting on SSB and VHF is a give away of drained battery, meaning obviously something went wrong somewhere.

If this vessel will ever have a PV, it will be for radio battery bank charging only, not for its 24V domestic battery bank system. The 24V domestic battery bank usage will be too high ( and expensive ) to be practical for a PV array, its a better job for a high power 95amps 24V charger powered by the generator.

Its just my mind trying to think of ways for the vessel operator to have less hassle. This vessel will have no dedicated radio officer, its a small 86 feet traditional wooden vessel for dive charter.

Regards,
Iya

Cariboocoot · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

Iya,

It looks like you'd need the converter and a charge controller. I can fully appreciate your desire for having a separate 12V battery for a 'buffer'. Good idea. Nothing like redundant systems in an emergency (I have FOUR generators). Maybe just run a standard PWM charge controller from 1/2 of the 24V to charge the 12V battery. Best of both worlds and all that.

Solar Guppy · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

If your going to have a 12V battery, then the MorningStar Sunsaver Mppt will do exactly what you want. It will down convert 24V to 12V and keep the battery fully charged which your loads can be peak more that the 15amp without any issues

This is different than the question you asked of them which was having the Mppt unit just be a down converter ( no battery ) and hence what I am saying is different than what Adam suggests.

The Sunsaver is small, efficient and should be a perfect fit for your need, with the understanding you will have a 12V battery. I would suggest a AGM 100 ah should work well for running the electronics

GreenerPower · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

Iya wrote: »

...I just surfed for a DC to DC charger and there is such a unit : http://www.powerstream.com/DCC.htm
But its is too small at 7.5 amps ...

If you're still interested in DC-DC as a backup path, here is an inexpensive 350W one (27.5A @ 12V) . They have a 500W i.e. 40A @ 12V model also.
GP

mike95490 · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

I think SG hit the nail on the head, with a 12V 100AH AGM, and a MorningStar Sunsaver MPPT. That will keep a battery floated, and radios running, with 100AH backup if all else fails. And trusted name brand.

edit - I guess if you use a $$ AGM, you better get the
optional Battery Temperature Sensor too

niel · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

i haven't been following this thread too closely, but did catch the last portions of it and i'll also agree with sg. i will add that if you need current levels near 20a that you may wish to get an agm of the 200ah class. i have run radios in the 20a class and my regret was only having about 100ah for it. if you wind up talking allot then the battery could dip below 50% dod in 3-5hrs. i know from experience on that point. a larger capacity allows for better battery utilization with lower draw %s on full power. even listening for a full day could put a 100ah battery down to about 65% soc (35% dod). the 15a from the controller will still charge the battery fine, but it may take a bit longer if you draw down too far on the battery. this will in general give some independence from relying too heavily on the 24v system during an emergency situation. the drawback with the 200ah battery would be that it will take a bit more solar power from pvs if charging is to be done. at the 5% minimum that is 10a at 12v or 5a at 24v and would be roughly about 175w or more in pv.

Cariboocoot · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

I agree with Niel about the bigger battery, but this is where we get into "how good is the charging system?" since it won't be recharged off PV's. 200 Amp/hrs of battery would, under "full charging" conditions draw approximately 10 more amps from the alternator/generator. Depending on how heavily loaded the system is over-all and what its capacity is, this starts to become a significant factor.

Photowhit · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

OK I'll plead ignorance here to some degree, If this is your emergency backup I would look for redundance. I've done a bit of sailing in the Gulf and a standard VHF radio has huge range. My last ill fated voyage I called in a bad storm from 12 miles out with out a problem. I don't think the radio drew much at all in reciever mode.

I suspect you could find space and money for a 12 volt agm battery and a small panel to maintain it. Just for bck up.

BTW - I wouldn't go for cute name, after spending the night on the hook, The motor wouldn't start in the morning, I couldn't cally (?) to pull the anchor, (I was lone) so I had to cut loose. So I was headed home and had to call in for assistance in the chanel, "Sailing vessel Shark Bait requesting assistance"(6-8ft in a 19ft sail boat, I went out in warnings and the front backdoored me! before I get scolded, this was an 19' Alacrity very sea worthy! Fixxed keels , mud puppy )

dwh · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

Solar Guppy wrote: »

This is different than the question you asked of them which was having the Mppt unit just be a down converter ( no battery ) and hence what I am saying is different than what Adam suggests.

Actually he did ask about using it a battery charger...from the OP:

"I am thinking to use a Xantrex C60 charge controller to charge 12V battery bank but power source not from PV, it will be from a 24V battery bank."

Solar Guppy · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

Iya wrote: »

Why I don't really like DC to DC converter for radio because when I use it, I can't connect its output to a radio battery bank, to allow the battery to act as buffer. I am not an electrical engineer, but if that DC to DC converter output exceed battery voltage, current will flow into the batteries and the converter will be working hard as a charger and short lived...I guess. The same reason Morningstar does not reccomend me using MPPT as DC to DC charger.... I think.
Iya

This quoted text is what lead me to believe OP was asking if a Mppt charger can run without a battery. With a 12V battery, you can have any power source on the input of an Mppt controller as long as its with in operational parameters of the charger

The Sunsaver Mppt is good to 75V so a 24V battery is fine and regardless of the load on the 12V side, it will be limited to 15amps maximum by the charger, so if the radio draws more, its comes from the 12V battery

GreenerPower · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

Frankly I don't understand the OP's decision that he must have a 12V battery bank.

Iya wrote: »

...The application is for a wooden motorized sailing boat. The main engine is a 24V starting system and so 24V DC is the voltage to go as domestic battery bank voltage since the alternator is 24V.

However the VHF and SSB radio always requiring 12V DC supply. So there must be a 12V radio battery bank regardless.

If the 24V is the most reliable power source:

The idea is, when all generators are down or if the 24V battery charger is down, I still have the main engine alternator feeding the 24V battery bank.

then a simple DC-DC converter with enough wattage and surge capacity should be sufficient wihout a 12V battery bank.

If for whatever reason, the 12V battery bank is a must (afraid of DC-DC converter failure ?), then using CC as DC-DC converter to maintain the 12V battery as SG suggested is best.
GP

dwh · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

Solar Guppy wrote: »

The Sunsaver Mppt is good to 75V so a 24V battery is fine and regardless of the load on the 12V side, it will be limited to 15amps maximum by the charger, so if the radio draws more, its comes from the 12V battery

While we're on the subject, let me ask a stupid question...

What about feeding the output from an automotive charging system into that CC?

I.e., if the engine alternator was putting out say 13.8v would the MPPT "boost" the voltage up to 14.4 (or whatever)?

mike95490 · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

dwh wrote: »

I.e., if the engine alternator was putting out say 13.8v would the MPPT "boost" the voltage up to 14.4 (or whatever)?

I think I heard somewhere, MPPT's only down convert, no up convert.

BB. · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

No, the "average" MPPT Solar Charge Controller only "down converts"--they cannot do "up conversion" of voltage.

There may be some out there that can do buck/boost (down/up convert)--but usually these circuits are less efficient than the usual buck down converter electronics.

-Bill

Cariboocoot · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

dwh wrote: »

While we're on the subject, let me ask a stupid question...

What about feeding the output from an automotive charging system into that CC?

I.e., if the engine alternator was putting out say 13.8v would the MPPT "boost" the voltage up to 14.4 (or whatever)?

What would be the point?
An automotive "12V" charging system puts out more than 13.8V anyway: as needed for re-charging the battery. Take the battery out, and a "free running" alternator will crank out significantly more V than 13.8. In fact without the regulator some will churn 50+ Volts. You could feed that into an MPPT I suppose ...
Do you have a specific project in mind?

dwh · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

Cariboocoot wrote: »

Do you have a specific project in mind?

Nah.

There was a guy here recently talking about building a generator rig using an automotive alternator to run a washing machine and dumping the excess power to his battery bank. Also when Kamala was speccing out his system he mentioned charging his trailer's deep cycle battery from the tow vehicle engine. And then of course there was this thread.

These things just had me thinking on the subject of, "Does an automotive charging system put out a high enough voltage to fully charge a true deep cycle battery - and if not, then what to do about it?"

That was in the back of my mind somewhere and this thread reminded me of a dumb question that had I wondered about some time ago but forgot to ask.

Cariboocoot · August 2009

Re: Xantrex C60 as a 12V charger from 24V battery bank

dwh wrote: »

These things just had me thinking on the subject of, "Does an automotive charging system put out a high enough voltage to fully charge a true deep cycle battery - and if not, then what to do about it?"

As configured, probably not as that's not what they're designed to do. But a good 100 Amp (truck) alternator ... that's about 1200 Watts so the potential is certainly there! (Most auto equipment is 50-70 Amp). You'd need a few HP to turn it over - about 4-5.

But to start with a auto system and feed into an MPPT and then expect to charge a deep cycle ... No. The reason being the original charging system will keep the output down to where there's no higher voltage to work with. Mind you, they make special "regulator bypass" kits just for this sort of thing.

Xantrex C60 as a 12V charger from 24V battery bank

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