Batteries, what to do next?

[Andt The Fiddler]

A perennial problem.

 

I have 5 110Ah domestic and 1 110Ah starter battery.

 

Yesterday I charged them with the generator as normal at about

1600hrs.

Later in the evening when watching a movie on DVD (TV)

the water pump cut in and the TV screen went black.

 

I checked the monitor 98% charged but 12.5 volts.

 

Today I have charged them from the engine,

as we moved the boat.

 

At 1102hrs they were at 100% with 13.12 volts showing

At 1425hrs they were at 99.4% with 12.51 volts showing

and 5.5 Ah having been used.

 

We were out between the readings and the on,y load was

the 12volt fridge which is about 12 years old.

 

It doesn't add up in my book.

 

So I have two thoughts,

1) is the battery bank filing (after about 3 years)?

2) is the fridge draining the batteries?

 

Our lighting is LED.

We rarely use the inverter.

 

I know I can rely on you guys for much input including

- do I need such a big bank with only LED lighting, a TV and a fridge

Plus ipad, phone charging etc?

[Kae]

Sounds like a bad connection somewhere. Have you checked all the battery connections?

[Alastair]

I think you are getting too much voltage drop due to resistance in your wiring. It is a constant problem with 12V (and the reason why 24V is better on bigger boats). How far is your TV from the battery bank? The voltage at your TV is probably marginal. Water pump draws a fair bit of current when starting, voltage dips and boom, TV turns off.

 

This is also why I think that it can be better to have an inverter and run appliances off 240V.

[ditchcrawler]

What are you measuring your state of charge with?

[Andt The Fiddler]

Ok,

 

I'll check my battery terminals.

 

I have a victron bmv 6025

 

Just checked again - am on the boat now!

 

1530 - 99.1% 12.64 volts 7.3Ah used - again Olathe fridge on.

 

The starter battery - same age same spec is showing 12.84 volts.

[Proper Job]

12.64v would indicate that your batteries are, as your indicator say, about fully charged

 

If your battery voltages are staying up in the 12.5v range, but appliances are dropping out, the previous posters are on the right track.

 

You have a large voltage drop on your system when loads are applied

 

Are you able to keep an eye on the battery voltage when the loads are applied? Does it dip when start up loads are applied?

[Andt The Fiddler]

Just checked the battery terminals and connections back to the Victron Charger, all nice and clean and tight.

 

Also checked the monitor again, @ 1700hrs 98.9% 12.57 volts 9.6Ah used (starter at 12.84v)

 

I note the comments on the wiring and 12v system, this has been ok forever but the symptoms resemble those experienced last time the battery bank went down.

 

With only the fridge in use, on a low setting, we have used nearly 10 amps in 6 hours, that is more than I would expect - yes?

 

I don't want to replace either if there is no need or if there is I want to replace the one that needs replacing. If both then both....

Though I am dubious about the size of the bank, is there any benefit to it, I've never had it down to 50%!!!

[GUMPY]

Ballpark figures for a fridge

Current drawn when running about 3 amps

Usually on about 50% of the time

So in 24hrs it will use about 36Ah

6hrs will be about 9Ah

[MikeV]

Battery voltages all seem fine. I'd next look at the voltage at the TV. Put a digital meter there and then run the water pump and see how much it drops. Are you using a voltage stabiliser for the TV?

[nicknorman]

Yes 10AH is ballpark correct for 6 hrs fridge. If the tv is dropping out when the batteries are showing 12.5v then as said, there is a high resistance connection somewhere. Depending on the type of fuses fitted, these can be a source of corroded and hence high resistance connections, especially if the TV and waterpump are on the same fuse. Worth a visual check and a wiggle. Then there is the battery isolator - sometimes cycling the isolator can help in the short term. Otherwise you will just have to methodically go through from batteries to services such as TV with a multimeter looking for the point where the voltage dips when the pump cuts in.

[MikeV]

I note the comments on the wiring and 12v system, this has been ok forever but the symptoms resemble those experienced last time the battery bank went down.

Any metal-to-metal connection, whether fuse, switch or plug & socket, can corrode and increase resistance over time.

[ditchcrawler]

OK I have not got this battery monitor but it tells you they are 99% charged at 12.5 volts, that doesn't seem right to me. What percentage is it showing when the volts are down to 12.2 ish

[Arthur Brown]

I'd look for a bad connection that is common to the TV and the water pump.

[Boaty Jo]

Do you have shore power to give the batteries a long charge.

I believe that, over time and a number of short charges the monitor tells you the batteries are full when in fact they are not.

This was once explained (simply) to me by Kuranda Marine.

 

Look at the Smartguage website - lots of info at http://www.smartgauge.co.uk/technical1.html

[Proper Job]

Don't forget that the temperature of the battery that's just come off charge will be high in comparison to it's temperature a few hours later and this will effect the voltage reading at the battery.

 

Also the reading should be taken with the battery at rest with no loads connected to it (something that few livaboards can afford to do)

Edited October 22, 2013 by Proper Job

[Andt The Fiddler]

Hi all, thanks for your comments, I have continued to monitor the situation.....

The way one does.

After watching a movie on the Ipad and TV last night the readings at 2300 were 12.4v and 15.4 amps used showing 98.1% on the dial.

This morning at 0900 12.02v 30.1 amps used 96.5%

 

I'd have to get the manual out but I think the % charged is based on the size of the bank 550Ah and not purely the voltage held - the two are obviously linked.

 

The fridge when running uses about 5 amps - I checked, currently it is set very low (circa no 2) and is on a lot - though this could be yet another 'red herring'

 

The batteries are coming up 3 years old and though technically still in warranty we all know about battery warranties I assume!

 

My debate is really if it is the batteries do I get a smaller bank as we are pretty much a 12V environment and use normally 30 > 40 Amps per day. so a pair of 'good' 110Ah might (should) suffice.

 

Your thoughts on all of this have been much appreciated, I know the boat wiring inside out btw and don't disagree with any of your comments.

[nicknorman]

Ok so if the battery voltage is 12.02 under no load, they are flat. That means that the actual capacity is much, much less than the 550Ah you think it is. This is likely to be due to sulphation.

 

If you never give a long charge (say 8 hrs) at a reasonably high voltage (say 14.8v) then sulphation will inevitably result. Let us know what your charging regime is, it might give a clue. As you say, probably best to replace the bank with fewer batteries and try to keep them properly charged. Maybe you should consider some Solar?

[Proper Job]

I think you need to ignor your SOC indicator

 

At 12.02v your battery in virtually flat - around 20% SOC

[Tony Brooks]

OK I have not got this battery monitor but it tells you they are 99% charged at 12.5 volts, that doesn't seem right to me. What percentage is it showing when the volts are down to 12.2 ish

 

 

Those were my thought but to be honest we have had this so often in the past I could not be bothered to reply.

 

It also depends where that voltage was measured. Many seem to think it was at the TV or fridge but I have not see this stated so I think its another case of an amp-hour counter encouraging the boater to sulphate their batteries.

[GUMPY]

At a rough guess from your readings your bank has a usable capacity of about 25 Ah

The thing that your meter doesn't do is allow for the reduced capacity as the batteries age.

[Proper Job]

I'd calculated a total bank capacity of about 60 - 70 Ah, so the 50% target would be about 35Ah.

 

Based on the voltage readings it's dropping to about 25 - 30% SOC

 

Time for new batteries me thinks - especially with Winter fast approaching and higher demands placed on battery capaicity between recharges.

 

In fairness, the OP appears to be a liveaboard, so three years usage isn't bad.

[smileypete]

If the OP has non sealed batts, could help if they posted all the SG readings after a reasonably full charge then a wait for an hour say.

 

cheers, Pete.

~smpt~

Edited October 22, 2013 by smileypete

[dor]

edit: deleted as in wrong thread.

Edited October 22, 2013 by dor

[ditchcrawler]

 

The batteries are coming up 3 years old and though technically still in warranty we all know about battery warranties I assume!

 

 

 

3 years and still in warranty, does the make start with " E " by any chance?

[GUMPY]

50Ah / 60Ah doesn't matter really if the bank was 550Ah then its down to 10% or in other words "broken with a capital F"