Decreasing charge time of FLA house bank

[haveaday]

Wayne,

Appreciate the comparison. It does sound like the challenge is around the fact that I just can't get that big initial charge you are achieving. I'll do some poking around as well as speak with the inverter manufacturer.

The suggestion of comparing the voltage at the alternator and at the battery is a good one. I'll check that tomorrow.

Thanks again to everyone for the information and direction about where to look. I have not ignored the advise of checking the cable lengths and configuration. At this time I don't have the confidence we are going to keep the boat long enough to pay off an investment of rewiring. Additionally, I'm currently in the Bahamas where I suspect enough 4/0 would cost me my first born.

Ben

[haveaday]

Originally Posted by Captain Bill

What size are your cables from the charger to the batteries and how long are they. Also are there any battery switches between the charger and the batteries. I have seen corrosion on battery switches cause charging problems as the charger sees a higher voltage than the battery. At the amps you are seeing the switch would get quite hot.

There is a battery switch, it is not warm as measured with an infrared thermometer and my hand. I am using 4/0 cable with runs of about 14' from inverter to batteries. The runs are nearly identical in length for negative and positive.

Ben

[rom]

Originally Posted by haveaday

According to the current reading on the Victron BMS I am seeing 13.56v at the batteries right now. When the alternator is running the voltage is higher but not over 14v. It is also worth mentioning that there is basically no time when the 12v system isn't under some load. So currently I believe there's about 30a of 12v load being consumed while the charger is also supplying charge current. Not sure if this would reduce the voltage to that level or if this is still pointing towards an issue with the charging function of the inverter.

Ben

From your first post it does not seem your batteries have a problem (though they might have one). Did you try to push your engine to full throttle to get the max out of your alternator ? Can you temporarily disconnect your loads while doing this test ? What's the charge rate then ?

[smac999]

Originally Posted by wayne.b

===

You appear to have a similar configuration to our Grand Banks 49: Magnum 120 amp inverter/charger, 8 Trojan T-145 golf cart batteries, 3 fridges, 1 freezer, lots of electronic toys, Kohler 20 KW generator, etc. We run the generator in the morning until the charger drops well into the acceptance range of about 50 to 60 amps. The starting rate in the bulk phase is about 110 amps which lasts for about an hour. Total run time in the morning is usually about 1 1/2 hours. We'll run the generator again while cooking dinner for maybe an hour or so, and again before bedtime until the charge rate drops well into the acceptance phase. That seems to work fairly well for us with the batteries lasting 5 years or so even with a lot of time at anchor. When underway we have a 300 amp firetruck alternator on the port engine which will fully recharge the house bank on a normal full day run. They also get fully charged if we're on a dock, maybe once a week on average.

I think you need to focus on getting more charging amps during the bulk phase, whatever that takes. It could be charger settings, cables that are too small, bad connections or what ever. You should be able to recharge at over 100 amps in the morning just like we do. It's also possible that you may need a new inverter/charger.

off the OP's topic but you also need more chargers. with a 20k gen (HUGE!!) and 900ah of batteries add another 100-200a of chargers. maybe 100 with FLA and 200 if you have AGM.

I use alot of the mastervolt 100/12/3 as a 2nd charger to an inverter / charger.

most people only have 3.5k gens and then you can't do this. but with a 20k you should have more chargers.

[john61ct]

Do what you can to get all charge sources' voltages the same and much higher, right up to the top of what the bank vendor specs.

And make sure that voltage stays high, that nothing is dropping down to float until current has dropped right down to .005 - .010C

All measured at the bank.

[TheThunderbird]

Hint. Split the house bank in two, and add a second charger.

Use a deviator to connetc the two banks if / when needed.

Possibly, same size/brand.

Engine batteries are charged by the engine alternator, or by the charger after the main bank.

Genny should directly charge its own dedicated battery.

PS change boat, if any , for other considerations than electric ones

[Maine Sail]

Originally Posted by smac999

if the battery is going from 12.5v to 14.6v and the charger is putting out 40a. then the batteries have issues. as that is the most they will take. which should be higher if you are 300ah down.

^^^THIS^^^

As batteries age & sulfate their ability to take current declines and their bulk stage becomes very short. With the current the OP describes it should be taking HOURS to attain absorption voltage. Golf cart batteries also need to be charged at higher voltages than the old school 14.4V thinking. 14.6V min to 14.8V is going to yield a considerably longer service life.

A short rise up to absorption voltage is a sure sign the batteries are on their last legs.

Originally Posted by smac999

you need to measure both sides. if the alt post is 14.5v and the battery is 13.5 then it's a cable issue too small, lose, or going through diodes or other junk. and you will have limited charging

Again ^^^THIS^^^


We need to start with the basic then move onto the other stuff. Voltage drop in charging systems on boats is one of the number one performance killers I know of. If the battery voltage is not the same as the "sensed" voltage at the charge source the charge source may already be in "voltage limiting" AKA CV/constant votlage or absorption or float... Once the charge source enters voltage limiting the amount of current going into the battery can only decline. When charging batteries even 1-2 tenths of a volt can mean big differncess in accepted current into batteries. Voltage drops in the 0.5v to 1V range are performance murdering...

Measure the voltage at full current output, the most you regularly see from the charge sources, and compare the voltage at the batteries to the charge source end. You can then further test the positive and negative leads to see which one may be the real culprit or to see if the share the issues.

Start with this test, then move on..

[ranger58sb]

Originally Posted by haveaday

According to the current reading on the Victron BMS I am seeing 13.56v at the batteries right now. When the alternator is running the voltage is higher but not over 14v.

13.56V would maybe be a float voltage -- and your eight GC2s would more likely want something like 14.5-14.8V (somewhere in there, whatever the battery maker recommends) during bulk and absorption phases.

Unless... Are your batteries old? If so, maybe they just won't accept as much current as they did when new...

-Chris

[haveaday]

Okay, we arrived at a marina and plugged in for the night. From that I've gotten some new data and made some adjustments. The first piece of data is that on shore power the inverter is capable of delivering big amps charging. Right now with the bank only down about 30 amps the batteries are taking 69 amps of charge. The only difference is that I am now on shore power instead of generator. The shore power I'm getting is over 240 volts, looks like around 245. So, I took a look at the generator, despite being rated for 240v it was putting out 230. I adjusted the voltage regulator and am now getting 242v out of the generator. That seems to have improved things on the generator side. It was putting out about 50 amps of charge on generator after the adjustment. But, there's still a big discrepancy between what is delivered on shore power versus on the generator. I'm not sure why that is and I'm still seeing the behavior where when the AC kicks in and loads up the generator charging amps increase. From this I've got to conclude that some how the generator isn't seeing the full demand from the inverter. I've got a call into the inverter manufacturer but haven't heard back.

Ben

[haveaday]

Oh and I should have mentioned that right now according to the BMS I am putting 61 amps of charge into the battery bank and the bank is at 14.42v.

Ben

[wayne.b]

Originally Posted by smac999

off the OP's topic but you also need more chargers. with a 20k gen (HUGE!!) and 900ah of batteries add another 100-200a of chargers. maybe 100 with FLA and 200 if you have AGM.

I use alot of the mastervolt 100/12/3 as a 2nd charger to an inverter / charger.

most people only have 3.5k gens and then you can't do this. but with a 20k you should have more chargers.

===

If you're talking about our Grand Banks 49, we do have more chargers. The 120 amp inverter/charger is just for the house bank (8 golf cart batts). The port side engine batt (AGM) has a dedicated charger, and the stbd side engine has a charger shared with the generator and windlass battery (also AGM).

[wayne.b]

Originally Posted by haveaday

Okay, we arrived at a marina and plugged in for the night. From that I've gotten some new data and made some adjustments. The first piece of data is that on shore power the inverter is capable of delivering big amps charging. Right now with the bank only down about 30 amps the batteries are taking 69 amps of charge. The only difference is that I am now on shore power instead of generator. The shore power I'm getting is over 240 volts, looks like around 245. So, I took a look at the generator, despite being rated for 240v it was putting out 230. I adjusted the voltage regulator and am now getting 242v out of the generator. That seems to have improved things on the generator side. It was putting out about 50 amps of charge on generator after the adjustment. But, there's still a big discrepancy between what is delivered on shore power versus on the generator. I'm not sure why that is and I'm still seeing the behavior where when the AC kicks in and loads up the generator charging amps increase. From this I've got to conclude that some how the generator isn't seeing the full demand from the inverter. I've got a call into the inverter manufacturer but haven't heard back.

===

One possibility is that your generator is not creating a perfect sine wave waveform, and that's causing your inverter/charger to cut back its output. You really need a professional to diagnose that properly. If all else fails you could replace your inverter/charger with a Magnum. I have one and it seems to be remarkably unfussy about its input power.

[Maine Sail]

Originally Posted by haveaday

The first piece of data is that on shore power the inverter is capable of delivering big amps charging.

Your Inverter/Charger does not like the power from your genset. Some are really picky, some are not.. Your gen set may need to be adjusted and set up or it could be you just have a picky I/C.

Originally Posted by haveaday

Right now with the bank only down about 30 amps the batteries are taking 69 amps of charge.

You would be down 30 Ah's not 30 amps. Regardless, your battery monitor is likely out of calibration and your bank is likely smaller than its face value rating. 69A or .08C, at 96.5% SOC, would be a pretty high acceptance rate for a bank of flooded GC batteries even if they were in good health.

Be sure to check the calibration of your battery monitor.

[haveaday]

Originally Posted by Maine Sail

Your Inverter/Charger does not like the power from your genset. Some are really picky, some are not.. Your gen set may need to be adjusted and set up or it could be you just have a picky I/C.




You would be down 30 Ah's not 30 amps. Regardless, your battery monitor is likely out of calibration and your bank is likely smaller than its face value rating. 69A or .08C, at 96.5% SOC, would be a pretty high acceptance rate for a bank of flooded GC batteries even if they were in good health.

Be sure to check the calibration of your battery monitor.

Will do on the battery monitor. I'll do a full calibration routine on it.

I'm hoping the inverter manufacturer can help with it's pickiness about power.

Ben

[ramblinrod]

Originally Posted by Pizzazz

The charging profile for GC2 batteries is simple and we'll understood. When you start charging the batteries the voltage will increase from about 13V (deeply discharged) to 14.4V (around 80% charged) and stay there for the acceptance portion which takes ages. You need:

1) Make sure you are in bulk charging mode (voltage starts below 14.4 and climbs up slowly).

2) Make sure the charger configured to supply max current at 14.4V. If in bulk charging mode GC2s can take up to 1/3C which means in excess of 200A in your case. Older or worn out batteries typically do not retain charge well but they accept the rated current.

Note that if you oversize your battery bank you will spend a lot more time in the acceptance range (80%-99% charge) which means long and inefficient charging times. My firm conviction is that you are better off undersizing your bank, abusing the batteries in the bulk charging range (20-80% charged) and replacing them often. There was another thread on this subject a few months ago.

Agreed, but 4 times daily A-hr consumption (for FLA) is ideal, and the OP is under this.

The main issue, RUNNING TOO MUCH REFRIGERATION.

Best solution, when away from shore power, shut down all but the most efficient single fridge/freezer combo. If you hafta walk 20 feet for another beer, it will likely do you some good, if you are used to needing 4 refrigeration systems aboard when tied to a slip! ;-)

PS, I think the OP is way underestimating other overnight loads. An incandescent anchor light alone = 12 hours X 1.2 A = 14.4 A-hrs.

A 12" MFD for anchor alarm can easily = 12 hours X 2.5 A = 30 A-hrs. Much better to run an anchor alarm app on a mobile device that will likely be on anyway.)