Battery SOC query

[KJT]

OK,

 

When the genny charge current reached 4 amps, can you remember what the charge voltage was? Also forgot to ask what's the Battery Capacity set to in the BMV?

 

Also would be good to run the engine til the charge current reaches 4 amps, then find out what the charge voltage is.

 

I'd set the Charge Voltage to 14.1V (at least initially), Tail Current to 2%, capacity to 440Ah.

 

If the batts are in daily use, they still need a looonng weekly charge to minimum tail current, especially AGMs which should reach less than 0.5-1%.

 

Sounds like the charge voltage is set way too low at 13.2V, so when the solar was dribbling in current at say 13.5V under low light levels, the meter would sync to 100% even though the batts were nowhere near charged.

 

Once it's syncing as it should, all that needs doing is checking the reported SoC against the resting voltage SoC.

 

cheers, Pete.

~smpt~

Hi Pete

 

As it happens I did make a note of the charge voltage @ 4 amps. It was 13.17v

 

I did as you suggest and altered the settings to 14.1v and the Tail Current to 2%. The battery capacity was correctly set to 440 ah.

 

We will be cruising again tomorrow and will post the charge current @ 4amps, hopefully at the end of the day. Will solar affect that reading or should I cover them up again? (530 watts)

 

Cheers

 

Ken

 

ETA solar

Edited August 30, 2014 by NB Ellisiana

[nicknorman]

Hi Pete

As it happens I did make a note of the charge voltage @ 4 amps. It was 13.17v

 

Nope, something wrong there! The current has fallen to 4A because the voltage has dropped to 13.17v. This is probably because the charger (presumably being run from your genny) has gone into float mode. Unfortunately some chargers have a habit of going into float prematurely, resulting in the batteries never reaching fully charged. Ask Spuds of this forum! If, at float voltage of 13.17, the batteries are taking 4A they are not fully charged. The correct float current should be very close to zero.

 

These sorts of chargers can typically be put back into absorption mode by cycling the power, ie turning them off and on again. Do that, and see what the charge current is when the charge voltage is over 14v. The batteries are only fully charged when, with the voltage well over 14, the current is but a few amps, preferably 1 or 2.

Edited August 30, 2014 by nicknorman

[smileypete]

We will be cruising again tomorrow and will post the charge current @ 4amps, hopefully at the end of the day. Will solar affect that reading or should I cover them up again? (530 watts)

 

Thinking about it, might be easier to lower the solar charge voltage to the minimum while cruising tomorrow, just so the alt charge voltage is more likely to end up highest and can then be read when the current tails off to <4A. As long as the alt warning light stays off then the alt should be doing something.

 

The name of the game is to find the highest alt charge voltage, the highest genny charge voltage, the highest solar charge voltage. Then take the lowest of all three, subtract say 0.1V then use that number as your BMV Charged Voltage.

 

That will mean the BMV can sync to 100% with any of the charge sources, as they can all exceed the Charged Voltage setting.

 

It's possible to find out the rated voltage of the alt and the charger and solar settings, but it's good to double check with an actual reading.

 

cheers, Pete.

~smpt~

Edited August 30, 2014 by smileypete

[KJT]

Nope, something wrong there! The current has fallen to 4A because the voltage has dropped to 13.17v. This is probably because the charger (presumably being run from your genny) has gone into float mode. Unfortunately some chargers have a habit of going into float prematurely, resulting in the batteries never reaching fully charged. Ask Spuds of this forum! If, at float voltage of 13.17, the batteries are taking 4A they are not fully charged. The correct float current should be very close to zero.

These sorts of chargers can typically be put back into absorption mode by cycling the power, ie turning them off and on again. Do that, and see what the charge current is when the charge voltage is over 14v. The batteries are only fully charged when, with the voltage well over 14, the current is but a few amps, preferably 1 or 2.

Thanks Nick. You are quite right. The charger was in 'float' mode at the time. The Victron has a forced absorption facility. I will do as you suggest.

 

Thinking about it, might be easier to lower the solar charge voltage to the minimum while cruising tomorrow, just so the alt charge voltage is more likely to end up highest and can then be read when the current tails off to <4A. As long as the alt warning light stays off then the alt should be doing something.

 

The name of the game is to find the highest alt charge voltage, the highest genny charge voltage, the highest solar charge voltage. Then take the lowest of all three, subtract say 0.1V then use that number as your BMV Charged Voltage.

 

That will mean the BMV can sync to 100% with any of the charge sources, as they can all exceed the Charged Voltage setting.

 

It's possible to find out the rated voltage of the alt and the charger and solar settings, but it's good to double check with an actual reading.

 

cheers, Pete.

~smpt~

Thanks Pete. I will cover the panels and see what charge voltage I get at the end of the day.

 

Cheers

 

Ken

[ditchcrawler]

I think the OP should be ensuring that he gets to 100SoC before worrying about syncing

[smileypete]

I think the OP should be ensuring that he gets to 100SoC before worrying about syncing

 

I'd say the best way to guarantee a proper full charge is to use an ammeter, as you'd do with a Smartguage.

 

Then set the BMV so it's a little pessimistic with partial charges, so the SoC reading is a little lower than actual, until a full charge is done.

 

cheers, Pete.

~smpt~

Edited August 31, 2014 by smileypete

[KJT]

Hi again.

 

I think we are getting there. After about 8 hours of cruising today the charge current was hovering around the 3.8 to 4 amps and the charge voltage was 14.17 to 14.2 v.

 

I had all the solar panels covered so they were giving zero output.

 

I hope that sounds better.

 

Ken

[Arthur Brown]

Now those are much better figures, Probably as close as many people get to 100%SOC but let the solar have a go at getting the float charge completed.

[KJT]

Thanks Arthur. That's good to know. Solar panels now uncovered!

 

Cheers

 

Ken

[Tony Brooks]

If that last set of figures\are from alternator charging then I think the alternator is somewhat suspect unless itis from the 1970/80s. This tends to be supported by some readings you took earlier. However this has already been commented upon.

Edited August 31, 2014 by Tony Brooks

[KJT]

If that last set of figures\are from alternator charging then I think the alternator is somewhat suspect unless itis from the 1970/80s. This tends to be supported by some readings you took earlier. However this has already been commented upon.

Yes, they were from the alternator which is circa 2002 vintage. From what has been mentioned it seems the alternator needs some attention.

 

Thanks

 

Ken

[Martin Megson]

I've just bought a BMV 700 model and am looking for a bit of advice on connections to the shunt. I think I've worked it out but would appreciate confirmation before I do something wrong. Particularly as my BSS is due next month. I know some would say leave it till after the test but I'll sleep better knowing an expert has looked it over.

 

My battery bank has 4 separate negative leads connected to it as follows:

 

1st connects to the negative busbar for the 12 volt systems.

2nd connects to the engine block (I assume this is the negative for the alternator).

3rd connects to the Inverter

4th connect to the battery charger.

 

I initially connected just the first to the shunt, leaving the others connected directly to the battery. The BMV was showing current drawn as I switched various things on but did not show the charge when the engine was running. I then connected the 2nd cable to the shunt and it now shows a positive current going in when the engine is running. Logic tells me I need to connect the 3rd and 4th cables to the shunt to capture input from the charger and current drawn by the inverter. However, I can't physically get anymore cables onto the shunt terminal so I'll need to fit a terminal block (busbar?).

 

Please could someone who knows confirm this approach is correct and if not how should the system be connected.

 

Thanks

Edited August 31, 2014 by Meggers

[nicknorman]

Yes one end if the shunt should be the only thing connected to the battery negatives. All the other leads must go to the other end of the shunt, including the -ve from the starter battery.

[Martin Megson]

Yes one end if the shunt should be the only thing connected to the battery negatives. All the other leads must go to the other end of the shunt, including the -ve from the starter battery.

 

Many thanks for the quick reply which confirmed what I thought, I forgot to mention the starter -ve cable.

[nicknorman]

Yes, they were from the alternator which is circa 2002 vintage. From what has been mentioned it seems the alternator needs some attention.

Thanks

Ken

On our modern Iskra 175A alternator, the voltage at 4A or so is 14.5 to 14.6v. It might seem as though 14.2v is not that far away, but the 0.3 to 0.4v makes a big difference.

[KJT]

On our modern Iskra 175A alternator, the voltage at 4A or so is 14.5 to 14.6v. It might seem as though 14.2v is not that far away, but the 0.3 to 0.4v makes a big difference.

Thanks Nick. As a result of the helpful replies I have had I think it best that I get the alternator checked out when I return to our marina in a couple of weeks. As I mentioned previously I am having some work done including the belts changed and Smartguage fitted so that would be a good time to get the whole system checked out.

 

Cheers

 

Ken

[smileypete]

Hi again.

 

I think we are getting there. After about 8 hours of cruising today the charge current was hovering around the 3.8 to 4 amps and the charge voltage was 14.17 to 14.2 v.

 

I had all the solar panels covered so they were giving zero output.

 

I hope that sounds better.

 

Ken

 

OK sounds like your alt has a 14.2V reg, IIRC some Beta engine alts charge at that level.

 

All that needs doing now is checking reported SoC against 'resting voltage' SoC from time to time, nighttime when solar has stopped is a good time. This table should be more accurate for AGMs:

 

http://jgdarden.com/batteryfaq/carfaq4.htm#mf_soc

 

If it's underreporting straight after a full charge, the Batt Capacity parameter may need adjusting. If it drifts excessively with partial charging then the charge efficiency may need tweaking.

 

 

While we're at it, your solar and batt charger can be a set a bit higher than 14.2V, according to the data sheet for Victron AGMs on this link (last page):

 

http://www.victronenergy.com/upload/documents/Datasheet-GEL-and-AGM-Batteries-EN.pdf

 

They give a range, for solar and shoreline charging I'd be conservative and use the lower end. But for genny charging which needs to be done quickly and is time limited 'd use the upper end.

 

 

 

Many thanks for the quick reply which confirmed what I thought, I forgot to mention the starter -ve cable.

 

Found a pic via google search on another forum which may help:

 

 

cheers, Pete.

~smpt~

[Martin Megson]

Thanks for the diagram Pete. It confirms what Nick said.

I now just need to get a high amp bus bar to connect everything to the shunt terminal.

[KJT]

OK sounds like your alt has a 14.2V reg, IIRC some Beta engine alts charge at that level.

 

All that needs doing now is checking reported SoC against 'resting voltage' SoC from time to time, nighttime when solar has stopped is a good time. This table should be more accurate for AGMs:

 

http://jgdarden.com/batteryfaq/carfaq4.htm#mf_soc

 

If it's underreporting straight after a full charge, the Batt Capacity parameter may need adjusting. If it drifts excessively with partial charging then the charge efficiency may need tweaking.

 

 

While we're at it, your solar and batt charger can be a set a bit higher than 14.2V, according to the data sheet for Victron AGMs on this link (last page):

 

http://www.victronenergy.com/upload/documents/Datasheet-GEL-and-AGM-Batteries-EN.pdf

 

They give a range, for solar and shoreline charging I'd be conservative and use the lower end. But for genny charging which needs to be done quickly and is time limited 'd use the upper end.

 

cheers, Pete.

~smpt~

Thanks, Pete. And for the links.

 

I will keep an eye on the readings now I have a better idea (hopefully) of what is going on.

 

Cheers

 

Ken

[KJT]

Looking at the worst case scenario, if I need to replace my alternator, are they normally a service exchange item or just a case of bin the old one and buy new? My existing one is 130 amp fitted to my Beta 1903 (43hp) engine. 2002 vintage. It looks like the maximum output I can get from it is about 60 amps. Would it be worth upgrading it to a 175 amp one? Where would be a good place to buy or exchange one?

 

Thanks

Ken

[nicknorman]

Looking at the worst case scenario, if I need to replace my alternator, are they normally a service exchange item or just a case of bin the old one and buy new? My existing one is 130 amp fitted to my Beta 1903 (43hp) engine. 2002 vintage. It looks like the maximum output I can get from it is about 60 amps. Would it be worth upgrading it to a 175 amp one? Where would be a good place to buy or exchange one?

Thanks

Ken

It should be repairable / overhaulable. The two "elements" are the electromechanical bits (stator, rotor, slip rings, brushes) and the electronic bits (rectifier, regulator). Hopefully it is just the electronic bits that need replacing, the stator and rotor don't really "wear" but the slip rings and brushes do, so I would have these checked and maybe new brushes, even if it is just the electronics that actually need replacing. Anyway, someone else will know a good place to get it repaired.

 

I'm not sure it is worth upgrading to 175A unless it is going to be very easy. For battery charging, our 175A alternator doesn't spend much time over 130A - maybe the first 30 mins after start (depends on how flat the batteries are of course) because the batteries become reluctant to take that much current. So, compared with a fully functioning 130A jobber, it won't decrease overall charge time significantly. It would I suppose allow running something like a 2 kw kettle or washing machine via inverter without depleting the batteries significantly.

 

Presuming the same belt (6pk polyvee) and flange to pulley distance, if there is not that much cost differential maybe it is worth it, depends on how tight on money you are.

 

Ed: can't remember if you said what engine you had. If a Beta, they are very helpful on technical queries and will be able to advise if a 175A is a direct and easy replacement. The only other thing to bear in mind is the engine size. A 175A alternator at full load puts quite a big load on an engine at idle. Smaller high-revving engines might struggle a bit.

Edited September 1, 2014 by nicknorman

[Tony Brooks]

If with fairly well discharged batteries the alternator, with engine revving well, can only produce 60 amps then either you have a significant voltdrop on the charging circuit or you probably have a failed diode or dry solder joint in the alternator.

 

To check for voltdrop put a voltmeter set to 20 volts DC (200V DC for 24 volt systems) between the main alternator positive terminal and battery positive. Then with well discharged batteries rev the engine. The meter should read no more than about 0.3 but I would not try to cure anything less than 0.5 volt.

 

Do the same with the negatives.

 

If the readings are OK then look on Yell or the BT sight for "Alternator & Starter specialist" for your local area and take it there for testing and discuss replacement with them.

[ditchcrawler]

On our modern Iskra 175A alternator, the voltage at 4A or so is 14.5 to 14.6v. It might seem as though 14.2v is not that far away, but the 0.3 to 0.4v makes a big difference.

Agree, I bet the extra 0.3 volts would lift that current a bit.

[smileypete]

Thanks for the diagram Pete. It confirms what Nick said.

I now just need to get a high amp bus bar to connect everything to the shunt terminal.

 

For something ready made this 200A bus bar may do OK:

 

 

http://www.12voltplanet.co.uk/4-point-negative-distribution-block-busbar.html

 

Best have the high current paths on same or adjacent studs. Examples being engine return to starter batt return, inverter return to shunt return.

 

If there's access to tools, they're not too hard to DIY from copper bar, maybe worth starting a new topic with details and photos for ideas.

 

cheers, Pete.

~smpt~

[KJT]

Thanks Nick, thanks Tony. That's very helpful and points me in the right direction.

 

Cheers

 

Ken