Charging queary

[FredW]

Good Morning,

I wonder if any of you good people could help with a problem I think I've just discovered?

We've lived aboard our boat as CC'ers since October 2012.She is fitted with a Beta 38 with twin alternators,the Domestic one is a 100amp Iskra.The battery bank is 6 x100Ah Numax sealed batteries that were fitted in June 2012.We have 400w of solar with a Victron Blue Solar 40amp controller.I have a Smartgauge and a cheap Chinese monitor that I use to keep my eye on things.The Chinese one I only use to tell me the what Amps and Volts are going into or out of the batteries,not the SoC,that I leave to the Smartgauge.Both gauges give similar voltage readings at any given time.Having read as many posts that I can find about the SG on the Forums,I think I understand the limitations of the SG,though I could be wrong of course.We have a Victron 1600w Inverter which only powers a 230v fridge,which is off in winter,a Candy 3kg Washer,very occasionally,any charging we don't have 12v adapters for and all lights are LED.I dont think I've ever seen our battery bank SoC go below 75%,and that only rarely.It's usually in the high 80,s or above when we go to bed,after a couple or three hours of watching the 12v telly. If I check in the night with everything off the voltage is usually 12.6 or above.

My problem first came to my notice yesterday evening when I ran the engine for some hot water.We'd had some charge from the solar all day and the battery monitor was showing a tail current of one to two amps after a short while,maybe ten minutes, but the charge voltage though was at 14.9 which I think was high and the SG flashed up E3 which I believe is overcharging.This morning,with the SG showing 88%, I started the engine and the voltage was again above 14.7 and the charge current started at around 45amp,dropping quickly to about 12.Could this indicate that the Domestic alternator is on the way out?Where we are at the moment would require a couple of days or so to get a new one & SWMBO doesn't think too much of the idea of ordering one just in case.Sorry to go on a bit but I'm trying to give as much info as possible.

Thanks in advance,

Fred.

[Tony Brooks]

What is the charge warning lamp doing when its supposed to be out and the engine is revving? Cup your hands around it and look for a glow. If you find on then a field  diode has probably failed.

If the 14.9V was in bright daylight and it was very cold that might have been caused by a temperature compensated solar controller so would be little to worry about.

I think the more likely explanation is temperature compensated solar coupled with well charged batteries. Can't rule out an alternator fault but would advise "wait and observe". If the voltage drops as the temperature rises then its probably temperature compensation.

[FredW]

Thank you Tony. I’m out for the rest of the day so can’t check but will do so when I get back. 

Fred

[Tony Brooks]

4 minutes ago, FredW said:

Thank you Tony. I’m out for the rest of the day so can’t check but will do so when I get back. 

Fred

I meant observe over the next few days, we have 9C forecast as on the way.

[FredW]

1 minute ago, Tony Brooks said:

I meant observe over the next few days, we have 9C forecast as on the way.

Will do,thanks again. 

Fred

[Detling]

Chargers which temperature compensate will increase the volts in cold weather. My victron does that and my smartguage always shows e3 just ignore it unless the volts are stupid ie. 17 volts or similar.  I believe that at -10 C the normal 14.6 charge goes to up to 15 volts for a wet lead acid battery. This is because the chemical reaction involved slows down increasing the internal resistance of the battery

[Alan de Enfield]

My 'cheapo' Halfords 6 amp charger was putting out 15.6v overnight & this morning, but started dropping and was at around 14.9/15.0 by mid-afternoon.

I have taken it off charge now.

[FredW]

Good Morning,

Just an update to this query. Now the warmer weather is here the charging voltages have gone down to what was advised,another lesson learned. No glimmer from the Warning Lamp Tony so all seems ok. Thank you to those who replied,much appreciated.

Merry Christmas & Happy New Year,

Regards,

Fred.

[Tony Brooks]

Many thanks for the feedback. It rounds the question and answer off nicely so others can learn in the future.