Victron battery monitor auto synch question

[Downeaster]

I have a stock alternator on a Universal M35B that seems to max out at 13.5V and 30amps regardless of SOC and engine speed. It is a 55amp alternator so not sure why it never exceeds 30amps. The battery bank has 460 AH (4 golf cart batteries).

The default setting for the Victron to auto synch is when the voltage exceeds 13.2 V and the charge current is less than 4% of total battery capacity. In my case that is 18.4 amps. So when the current drops to 18 amps at 13.5 V the monitor auto synchs.

Given the low voltage and current output of the alternator into a relatively large bank it seems to auto synch pretty quickly. I'm concerned the batteries are not being recharged sufficiently.

Is the Victron assuming a more healthy 14.5 V 50+ amp injection from the alternator? And if so, how would I adjust the Victron settings (charged voltage and tail current)?

Any suggestions or thoughts?

[sailorboy1]

Originally Posted by Downeaster

Given the low voltage and current output of the alternator into a relatively large bank it seems to auto synch pretty quickly. I'm concerned the batteries are not being recharged sufficiently.

Been there, done that!

If they are flooded lead acid batteries they aren't getting fully charged at 13.2V!!!! (sorry they are 6V golf cart batteries so of course they are). u have the same house bank as I do and I went though this last year.

The first thing you need to do is look into your voltage regulator to see if can be adjusted for a higher voltage. It wouldn't matter what you do to the BM if you can not get the voltage up. Did you have AGMs or gels before which would have used a lower setting?

As a min in the meantime I would (and did) change the Vc setting in the BM to something higher so as least it stops resetting to 100% so it keeps track.

[btrayfors]

I'd be much more concerned about the low voltage and amperage output from the alternator. Probably, this is because the regulator isn't allowing the voltage to climb higher than the 13.5VDC you're seeing, and at 13.5VDC your 460AH battery bank isn't accepting any more current than you're seeing.

Don L is right on!

If you have an internal regulator, it's probably one of the older ones and may not be adjustable for higher output voltage. If it's an external one, it almost certainly is.

This is a much more important issue than setting up the Victron monitor, because if your batteries aren't getting a truly full charge they will be sulfating and losing capacity.

If the golf carts are flooded (like Trojans or Exides or Dekas, etc.) their absorption voltage needs to be kicked way up....somewhere in the 14.8VDC region.

Bill

[Quintessa]

Your poor little alternator is looking at climbing mt Everest. If it charges any more than 30 amps it will burn out. If your batteries are say half charged it would take at least 10 hour as the fuller they get the less the alternator will put in. Also you have to allow what you are using on the boat who'll charging which with a plotter sounder fridge etc is probably 10 to 20 amps. Frankly you need better charge system and with battery bank that size 3/ 80 watt solar panels. I have 4 panels and wind generator and end of the day they are fully charged but also have charger running on the genset which tops them up again before going to bed but we have 2 /12 volt fridges which suck a bit.

[Downeaster]

Thank you gents - this is what I feared. It is a stock alternator (Prestolite or Mitsubishi) with an internal regulator that doesn't appear to have an adjustment for voltage. It is frustrating because the alternator specs state 13.5-14.5 V as normal output range and we all know now that 13.5 is too low...

So now I need to decide whether to upgrade the alternator or take the plunge on a solar setup. Both a challenge with the boat on a mooring and working like a dog all week long...

[btrayfors]

I agree that additional charging capacity would be a good thing (larger alternator, solar panels, wind generator, etc.), but you might also look at the cost of converting the existing alternator to use an external regulator.

This is normally a very easy thing to do for any competent alternator shop.

Then, you could buy a good external regulator like the Balmar MC-612 or MC-614 which can be set up any way you like to take advantage of whatever alternator you have, including de-rating it a bit to help ensure it doesn't burn up from overwork :-) Later, you could add a larger alternator and use the same regulator.

Estimated costs:

- Convert to external regulator....less than $100
- Balmar MC-614 regulator w/harness....less than $300
- New 100-125A marine alternator (top quality)......$400-500

Also, if the boat is on a mooring much/most of the time, solar panels are certainly the way to go to keep your batteries topped up.

Even a smallish panel and a good regulator would be helpful, like one which could put out 140-200 watts, and something like the Morningside Prostar or Sunsaver MPPT regulators.

Bill

[noelex 77]

Originally Posted by Downeaster

The default setting for the Victron to auto synch is when the voltage exceeds 13.2 V and the charge current is less than 4% of total battery capacity. In my case that is 18.4 amps. So when the current drops to 18 amps at 13.5 V the monitor auto synchs.

I agree this is synchronising too early. 0.2v below absorption voltage and 2% is a commonly recommended setting and many people use a more aggressive setting.

[Downeaster]

Thank you all for your responses! :-)

[colemj]

For now, put a diode on the sense line. This will drop the voltage 0.4-0.6V and you will make that up in charge current and voltage - putting your output at ~14V with higher current getting there. This will cost you $1. Make sure you put the diode in the correct orientation.

Mark

[sailinglegend]

My suggestion for the Victron problem would be to turn the auto sync off and manually re-synch when YOU know the batteries are 100% charged. To do this simply set the reset voltage to about 16 volts - which of course it will never get to!

[goboatingnow]

Originally Posted by colemj

For now, put a diode on the sense line. This will drop the voltage 0.4-0.6V and you will make that up in charge current and voltage - putting your output at ~14V with higher current getting there. This will cost you $1. Make sure you put the diode in the correct orientation.

Mark

I suspect the alternator isn't ever getting the batteries out of bulk mode, so the diodes not going to do much

Dave

[colemj]

The diode will increase the voltage the alternator attempts to reach. He says it is currently maxing out at 13.5V regardless of SOC, so increasing the output voltage will help.

Mark

[goboatingnow]

Originally Posted by colemj

The diode will increase the voltage the alternator attempts to reach. He says it is currently maxing out at 13.5V regardless of SOC, so increasing the output voltage will help.

Mark

Not really , the batteries are so big and there will be system loads , so I suspect the alternator is flat out as it is , it won't help IMHO as the alternator probably never completes the bulk phase. Seriously undercharged batteries I suspect

You can't " force" up the alternator voltage if the battery load is too high.
Dave

[colemj]

OK. I was going by the OP saying it was only reaching 13.5V regardless of SOC.

Mark

[Maine Sail]

Originally Posted by Downeaster

I have a stock alternator on a Universal M35B that seems to max out at 13.5V and 30amps regardless of SOC and engine speed. It is a 55amp alternator so not sure why it never exceeds 30amps. The battery bank has 460 AH (4 golf cart batteries).

It likely never exceeds 30A because you are never able to get them near full at 13.5V and you are still in bulk mode.

Originally Posted by Downeaster

The default setting for the Victron to auto synch is when the voltage exceeds 13.2 V and the charge current is less than 4% of total battery capacity. In my case that is 18.4 amps. So when the current drops to 18 amps at 13.5 V the monitor auto synchs.

With a single stage regulator you really need to ignore auto-synch feature and do manual re-sets when the accepted current falls to 2% of less of capacity, or in your case about less than 10A can justify a manual re-set. If this is your only source of charging then you can re-program it to auto synch at a higher voltage.

Originally Posted by Downeaster

Given the low voltage and current output of the alternator into a relatively large bank it seems to auto synch pretty quickly. I'm concerned the batteries are not being recharged sufficiently.

I work on a lot of these engines and to say the factory wiring for charging is a complete and utter joke, is an understatement. I suspect your alternator can easily regulate to 14.2V - 14.4V but with the diode isolator and the poor wiring, both neg and pos side. You are having trouble getting you bank to target voltage but your alt is at target voltage when at higher SOC. I do suspect that you may never have run the engine long enough at this voltage to get beyond the bulk phase.. .

Originally Posted by Downeaster

Is the Victron assuming a more healthy 14.5 V 50+ amp injection from the alternator? And if so, how would I adjust the Victron settings (charged voltage and tail current)?

Any suggestions or thoughts?

If this is your only source of charging then you could easily re-program the Victron for a higher "tail" voltage and current.


The big problem is that you ideally need to correct your charge voltage.

Start with this:

#1 With all DC loads off measure the voltage at the back of the alternator, after the batteries have been charged via a shore charger to full. Put the + of the volt meter on the B+ and the - lead on the alt case or B- stud. What is that voltage and what is the current flowing out of the alternator. Write it down.

#2 When pushing your 30A of current measure the output of the alt (same as above) and then do the same only this time measuring the voltage at the battery terminals. The difference between the two is the sum of your systems voltage drop. If you have 14.1V at the back of the alt and 13.5V at the battery posts then you have a 0.6V drop at 30A. If you have 14.4V at the back of the alt then you have 0.9V drop.

#3 Now place the + lead of the volt meter on the B+ terminal of the and the - lead on the + battery post. Does your meter give a reading? This is the sum of the voltage drop in the + cable.

#4 Now do the same for the neg side of the alt circuit. Neg lead to neg on battery pos lead to case of alt. Is there a reading?

#5 Now get rid of the diode isolator and run new dedicated positive and negative wires, sized for bare minimum voltage drop, to the house bank or to the starter post and let it pick up the bigger wires.

#6 If you want to charge both banks automatically add an Echo Charger , Duo Charger or combining relay..

#7 If there is a Universal/Westerbeke factory installed ammeter circuit GET RID OF IT. You can replace the ammeter with a simple volt meter.

Still, don't count on this factory alt to put out the rated 55A for more than a couple of minutes. When hot it will likely run at about 35-45 +/- amps but at least your voltage and chronic undercharging of the bank will be solved..... Once the voltage issue is fixed you may find that your 460Ah bank may eventually cook the alt by running it at wide open for far too long....