Which charger to use ?

[ghost0070]

My American tug has two battery chargers. A Xantrex Prosine 2.0 2000 watt inverter charger and a Xantrex Trucharge 40 charger. I have a house bank of two 4D 200 amp batteries and a single 4D 200 amp start battery. Currently, the boat is on a mooring so the options are the generator or engine alternator to provide power for charging. I can't find a clear indication in the manuals or online as to which is the best to use. Thoughts? Thanks

 

[ranger58sb]

Since you have two, you may need to use both.

Might be the inverter/charger is set up to service one bank (often inverter/chargers are single-bank units) like the house bank, and might be the other charger is for other banks (main starting battery, maybe genset starting battery).

-Chris

 

[O C Diver]

If the engine alternator doesn't have a "Smart 3 or 4 stage external regulator", it will be much slower at charging your batteries. Alternators are slow battery chargers, primarily designed to handle power being consumed.

Ted

 

[meridian]

You should consider making all the 4D's a single bank then get a right sized battery for the starter. 4D is overkill.


Sent from my iPhone using Trawler Forum

 

[DavidM]

Well, Ted is correct above, but the question is which charger to use, driven by the genset presumably.


I have a good friend in exactly the same situation. He has a 400 watt solar bank, an old Charles 30 amp charger and a Xantrex Freedom HW 1000 watt inverter/charger with a 25 amp rating, all connected to the house bank.


The simple answer is to use them all or the latter two with the genset at night. In practice as the batteries get up to about 75% charged, the Charles charger effectively cuts off and all charging is done by the Xantrex. This is because the acceptance/float transition voltage on the Charles is lower than the Xantrex, and it reverts to float which means it isn't providing any meaningful charge anymore.


Without a clamp on ammeter and some experimentation, it isn't possible to know which charger will "cut out" first, but it doesn't matter- use them all.


Now if you don't have enough KW from your genset to run them all that is a different story, but I doubt that that is the case.


David

 

[foggysail]

I have a Xantrex 50 something or other that I certainly do NOT recommend! Sure, it is a so called smart charger, that is the label they past onto it. My opinion is that is slightly better than the old constant voltage transformer battery chargers. It WILL charge 50 amperes but not for long. The charging current quickly diminishes and it takes forever to recharge batteries. Impossible if at anchor for a weekend or longer.

Now solar, that is another story! My4 each 150W panels provide between 20-25 amperes for either the complete daylight hours or until the batteries attain float voltage. Heck, last week I noticed that the circuit breaker for my 8.3 cf self defrost fridge was accidentally turned off. Been that way for about a month. Piece of cake for my solar, it kept the problem a secret!

 

[caltexflanc]

From genset or shore: Inverter for the bank that feeds it. Pure charger for the start bank. Get someone knowledgeable on board to help you figure out what the alternator is set up to do and have the chargers do per the first sentence. Leave everything else alone in the meantime, no reason to screw with the legacy battery set up unless you have definite plans to change the power requirements.

 

[DavidM]

I think that you are right- solar controllers charge more effectively than AC powered chargers. The why is puzzling. Maybe solar controllers in general are used with flooded cell batteries. Those can stand more over voltage with out harm (other than boiling a bit of electrolyte) so the acceptance/float transition is set higher than AC chargers.


That is certainly the case with my friend's charging system described above. The solar controller is the last one to switch to float- assuming there is still sun out at that point.


David

 

[foggysail]

I think that you are right- solar controllers charge more effectively than AC powered chargers. The why is puzzling. Maybe solar controllers in general are used with flooded cell batteries. Those can stand more over voltage with out harm (other than boiling a bit of electrolyte) so the acceptance/float transition is set higher than AC chargers.


That is certainly the case with my friend's charging system described above. The solar controller is the last one to switch to float- assuming there is still sun out at that point.


David

There is no reason why a properly designed AC charger should not work well using the now common 3 stages. Personally I believe the manufacturers such as Xantrex skimp on the charger designs. To charge continuously at 50 amperes means the inverter must be capable of about 650 watts of charging power. The dinky little Xantrex I have that is rated at 50 amperes I think would smoke after about 30 minutes at that charge rate.

Now solar is different unless you are using an MPPT controller WHICH I DO NOT RECOMMEND. Most regulators are designed as a switch so that all of the current a panel can provide gets to the batteries. They begin to fall back after the batteries reach the float state.

So in my case, the 20-25 charging amperes is the maximum that my panels can provide. Now interestingly, panels are constant current sources. That means a panel will provide (if the load can accept) the max current with little regard to the output voltage..............within reason. This characteristic is shown as a curve of output voltage vs current where the output voltage is determined by the load on the panel's specification sheet.

 

[Martin J]

You need to put a couple of solar panels on to keep everything charged on the mooring. The use the inv/chrger when on Genny, that will supply 110 and charging 12v

 

[BruceK]

...Now solar is different unless you are using an MPPT controller WHICH I DO NOT RECOMMEND....

There`s a tantalizing observation. I thought MPPT was the solar controller of choice. Why do you not recommend them?

 

[Bay Pelican]

The OPs question was which of the two chargers he has should he use. Between the two, the Xantrex Prosine 2.0 will deliver approximately 100 amps to start (had one years ago but I am now guessing on the output). The Truecharge will deliver 40 amps. Both will have a drop off as the charging cycle continues. Between the two the OP is better off using the Prosine 2.0 and getting a faster charge when operating his generator. His battery bank is large enough to take the full 100 charge from the Prosine 2.0.

If the OP has any sort of meter which can monitor the output of the two chargers he should try and use both chargers at the same time. Again 140 amps is within the 25% rule for battery charging, 25% of total amp hours for the bank. (25% of 600 amp hours is 150 amp hours). The problem with running two chargers without a meter is that the Prosine 2.0 might sense the output of the Truecharge as a false battery level reading and reduce its output. The meter would show this.

An alternative for the OP is to use a couple of battery switches and use the Prosine to charge the two 400 amp batteries (again 100 amp output is 25% of 400 amps) and to use the Truecharge to charge the single 200 amp battery. This would allow for full charging power when he is running the generator. When on shore power he can use the battery switches so he only needs one charger. The battery switches would also be useful if one charger fails. He could then use the remaining charger for both banks.

 

[FF]

"Both will have a drop off as the charging cycle continues."

This is because many charger ratings are pure BS.

The "full output" might be there on a dead batt , at about 10V , but is quite limited when the batt gets up to 13.5 or 14V.

Work the output in KW and see the difference.

 

[CaptTom]

I have a Xantrex 50 something or other that I certainly do NOT recommend! Sure, it is a so called smart charger, that is the label they past onto it. My opinion is that is slightly better than the old constant voltage transformer battery chargers. It WILL charge 50 amperes but not for long. The charging current quickly diminishes and it takes forever to recharge batteries. Impossible if at anchor for a weekend or longer.

I think that's the way smart chargers are supposed to work.

Unless you've let the house bank get way down - 50% SOC or less - the charger output is only going to be near it's rated power for a short time, then throttle down as the voltage comes up. I've read a lot about why, but only retained enough to know that's the way they work.

Apparently the formula they use is complicated, so with my limited knowledge I wouldn't be comfortable putting two smart chargers on the same bank and letting them fight it out. But I'll defer to better experts than myself on this one.

That said, my answer to the original question would be to use the "big" charger on the "big" bank, and the smaller on the single battery.

Don't expect to pull a partly discharged bank up to 100% by running the genset for an hour. In my experience, if you can get to 90%, you're doing well.

 

[Martin J]

Sorry foggysail I've had solar on my last 2 boats (10 years) the first had a Blue sky MPPT and my current has a Midnite Solar MPPT. Both perform excellent and the MPPt does ensure no power is wasted. Both units bulk charge, and appear to be more efficient on charging than an a.c. charger. My current unit (Midnite solar) produces some 2-4kw a day here in the caribbean, runs all requirements domestic , fridge,wine fridge, hairdryers, 110v cooking rings at lunch etc. All without the cost of a genny, and the noise associated. As per the "do not recommend MPPT" I would love to hear your rationale? Why throw away the extra 25-30% of power? The developmment of MPPT is a huge step up in technology over the old basic controllers.

 

[DavidM]

Well, at the risk of supporting this thread shift, let me expound on MPPT controllers:


Solar panels have gotten cheaper over the years, but controllers (except for questionable Chinese ones) have stayed the same. So if you are installing up to a couple of hundred watts of 12V nominal panels, MPPT controllers don't make much sense. They do add 10-15% to the power produced, but you can add panel wattage to make up the difference cheaper than you can switch from PWM (the cheaper pulse width modulation) to a MPPT controller.


That is the basis for the PP's statement, but it isn't applicable to all situations and particularly not for 24V panels.


If you install more wattage or you use 24V or higher panels (which are required for anything more than 135 watts per panel) then use an MPPT controller. The MPPT controller is an absolute no brainer for the 24V panels. You would lose 60% of your power if you just connected a PWM controller to a 24V panel.


The above are of course generalities and the specifics of the installation can make a difference.


David

 

[foggysail]

OK, OK, now that I have dumped pee into everybody's cereal I will explain my positions.

My thoughts on Xantrex or at least the one I own, XC5012. And yes, I am well aware how modern chargers are supposed to work but that does not mean that they do work the way they are advertised. Let me acclaim that the old Heart Interface Freedom 10 that I have for my 24v bank, though old its charger is second to none!

It charges the way a modern 3 state charger should work. I installed this device some years ago after purchasing it new on EBay for about $200, a bargain that few wanted because it operates on 24vdc. I use 24v primarily for my windlass, I never want to have to haul my 80# Manson Supreme by hand nor did I want to use 00 gage copper wire to minimize voltage drop to the windlass. It also provides pseudo AC power which offsets some of the load from my 12v bank.

I recharge the 24v bank with our generator. I watch the generator current remain at an almost constant current of 10 amperes AC for about 1-1 1/2 hours and then suddenly drop off to about 1 ampere. At that time, the 24v bank is completely replenished. OK..... Heart is now Xantrex but Xantrex is a far cry from Heart!

My over rated Xantrex XC5012 seems to charge as a constant voltage source, NOT a constant CURRENT source such as the way my old Heart charges. A constant current source is going to charge at a given current rate until told not to. A constant voltage source will charge according to:

I = (Vsource - Vload)/(load impedance)

Now sure, I know that impedance does not apply to DC but the chemical reactions inside a battery cause the battery's internal resistance to change as a function of charge. That is why I characterized the battery's internal resistance as impedance.

So say what you will about Xantrex! Mine takes days to recharge the 12v bank by itself and that is the ONLY reason I resorted to solar.

 

[foggysail]

Well, at the risk of supporting this thread shift, let me expound on MPPT controllers:


Solar panels have gotten cheaper over the years, but controllers (except for questionable Chinese ones) have stayed the same. So if you are installing up to a couple of hundred watts of 12V nominal panels, MPPT controllers don't make much sense. They do add 10-15% to the power produced, but you can add panel wattage to make up the difference cheaper than you can switch from PWM (the cheaper pulse width modulation) to a MPPT controller.


That is the basis for the PP's statement, but it isn't applicable to all situations and particularly not for 24V panels.


If you install more wattage or you use 24V or higher panels (which are required for anything more than 135 watts per panel) then use an MPPT controller. The MPPT controller is an absolute no brainer for the 24V panels. You would lose 60% of your power if you just connected a PWM controller to a 24V panel.


The above are of course generalities and the specifics of the installation can make a difference.


David

@#%&*^%$ HEY!!! YOU STOLE MY THUNDER!!!!!!!!

Others should pay attention to your post

Foggy

 

[Martin J]

Thanks for the commets David. In my case and many others it's always where to stick the panels, , mine are on the Flybridge top you can see in my avatar. . There is no room for more and not to waste power to loss for a couple of hundred bucks more it seems silly to use pwm . The extra bucks are nothing over the years and recouped easily in a year of not running the genny at 1gph+ (15kw). The modern MPPT has come a long way from there inception (10-12) years ago. I can not praise my Midnite pumping 30-50 amps in, it's a pleasant thing to watch!! It's always amazing to notice guests who will stand on the bridge and watch the screen with the volts and amps constantly changing!

 

[foggysail]

Thanks for the commets David. In my case and many others it's always where to stick the panels, , mine are on the Flybridge top you can see in my avatar. . There is no room for more and not to waste power to loss for a couple of hundred bucks more it seems silly to use pwm . The extra bucks are nothing over the years and recouped easily in a year of not running the genny at 1gph+ (15kw). The modern MPPT has come a long way from there inception (10-12) years ago. I can not praise my Midnite pumping 30-50 amps in, it's a pleasant thing to watch!! It's always amazing to notice guests who will stand on the bridge and watch the screen with the volts and amps constantly changing!

Dave provided an excellent explanation for use of the MPPT controllers. Now of course those who are space limited cannot resort to just adding additional panels. I also want to add that I never considered the impact on higher voltage panels because I concentrated my attention to a 12v system such as currently installed on my boat.

My only exception to Dave's post is that if one has space for additional panels (12v only), adding panels is still a better approach than adding an expensive controller. Consider for example a 20% benefit (if that) per panel by using an MPPT. Five panels would be required before the benefits of a controller are equal to a panel.

Morningstar's 25 ampere controller sells now for $298. I paid $320 for 2 each 150 watt 12v panels delivered from Amazon. At this time I have a total of 4 panels.

 

[Martin J]

Thanks for the comments. In my case panels were 1$ a watt 4x235watt $940 plus the Midnite controller $550. I went for the midnight over the blue sky I had beforebecause the functions were better and ease of use. It takes up to 150vdc in and up to 96volts out for 72 volt systems. I run mine at 48volt in and 12volt out. The 48volt means the wiring is very light 4g or 6G if i remember. More than adequate for the amperage I create. My main criteria was to fully utilize all power, and enable me not to waste the shoulder periods of dawn and dusk.As we spend considerable time 3 monrths cruising in the spring and 3 months cruising in the Autumm in the Caribbean power is very important and has to be self managing. Since installation on this boat the last 3-4 years have been maintenance free, apart from a self watering battery bank! As an after thought I do have a standard PWM on my jeep running the solar panels that keep my Jeep operational at the airport while we are in the caribbean!! Even when we return in early January the jeeps charged and ready to go!!

One major thing is the saving in heavy cables , and runs to use the variable voltages of an MPPT

 

[foggysail]

Thanks for the comments. In my case panels were 1$ a watt 4x235watt $940 plus the Midnite controller $550. I went for the midnight over the blue sky I had beforebecause the functions were better and ease of use. It takes up to 150vdc in and up to 96volts out for 72 volt systems. I run mine at 48volt in and 12volt out. The 48volt means the wiring is very light 4g or 6G if i remember. More than adequate for the amperage I create. My main criteria was to fully utilize all power, and enable me not to waste the shoulder periods of dawn and dusk.As we spend considerable time 3 monrths cruising in the spring and 3 months cruising in the Autumm in the Caribbean power is very important and has to be self managing. Since installation on this boat the last 3-4 years have been maintenance free, apart from a self watering battery bank! As an after thought I do have a standard PWM on my jeep running the solar panels that keep my Jeep operational at the airport while we are in the caribbean!! Even when we return in early January the jeeps charged and ready to go!!

One major thing is the saving in heavy cables , and runs to use the variable voltages of an MPPT

Well thought out system! I do want to comment on heavy cables that many believe are necessary in 12 volt panel wiring.

Batteries in need of charge have low terminal voltages even when accepting a charge. The important thing to notice is the voltage/current curves for the panels in use and calculate the voltage that the panels will see....battery voltage under charge plus the wiring voltage drop. The time when most current will be accepted by the battery is when it is in a lower charge state so some wiring voltage drop can be accommodated. As the charge increases, the acceptance current decreases which reduces the wiring voltage loss.

Now of course this does not suggest one can use lamp cords for panel wiring. It illustrates only that lesser size wires can be used in many cases and that is all.