Jump to content

puzzling batteries


Featured Posts

Hi gurus(guys) my batteriez are proving to be a puzzle,I have 6 X 125ahc in a 12v bank. I have a bmc 702 battery monitor which after charging says I have a healthy 13.8v in the bank. However when i start to use this it takes about 2 hours before it says thar SOC is 11.9v, i have disconnected one battery at a time for 24 hours and it still happens. The batterys are connected to:-

A victron inverter 3000w which powers the fridge/freezer 7amps and the cooker + 2 more amps when running and the 12v supply to the boat when everything is switched on draws a 51amp load. Simple maths tells me that there are more than enough amps in the batteris to run my boat for more than 2 hours if everything is in use, but it is not under that kind of load ever. Now i am not electrically minded but do need some sage advice. Other than "buy 6 more batteries and see if it still happens" i have recently on advice fitted a de sulphater(sterling) and the problem still exsists, other advice given was that the dicharged state should be 12.1v any lower and you're in a whole heap of pain.

Link to comment
Share on other sites

Hi gurus(guys) my batteriez are proving to be a puzzle,I have 6 X 125ahc in a 12v bank. I have a bmc 702 battery monitor which after charging says I have a healthy 13.8v in the bank. However when i start to use this it takes about 2 hours before it says thar SOC is 11.9v, i have disconnected one battery at a time for 24 hours and it still happens. The batterys are connected to:-

A victron inverter 3000w which powers the fridge/freezer 7amps and the cooker + 2 more amps when running and the 12v supply to the boat when everything is switched on draws a 51amp load. Simple maths tells me that there are more than enough amps in the batteris to run my boat for more than 2 hours if everything is in use, but it is not under that kind of load ever. Now i am not electrically minded but do need some sage advice. Other than "buy 6 more batteries and see if it still happens" i have recently on advice fitted a de sulphater(sterling) and the problem still exsists, other advice given was that the dicharged state should be 12.1v any lower and you're in a whole heap of pain.

How old is the bank?
Link to comment
Share on other sites

Fitted Aug 2013

Fitted Aug 2013

 

Depending on how well you have treated them it is certainly possible to trash a bank in two years.

 

The last bank we had on our boat were showing similar to yours at around 2.5 years, by the time we came to sell the boat at three years old they wouldn't hold any charge of any significance what so ever and were replaced as part of the agreement when we sold.

Edited by MJG
Link to comment
Share on other sites

Hi gurus(guys) my batteriez are proving to be a puzzle,I have 6 X 125ahc in a 12v bank. I have a bmc 702 battery monitor which after charging says I have a healthy 13.8v

Sorry but that reading proves nothing, to be of any use the batteries must have been rested for a few hours with nothing going in and nothing going out.

 

However when i start to use this it takes about 2 hours before it says thar SOC is 11.9v,

Small confusion of terms SOC is a percentage of capacity (not necessarily what the labels says) Was 11.9v with anything turned ON

 

i have disconnected one battery at a time for 24 hours and it still happens. The batterys are connected to:-

A victron inverter 3000w which powers the fridge/freezer 7amps and the cooker + 2 more amps when running and the 12v supply to the boat when everything is switched on draws a 51amp load. Simple maths tells me that there are more than enough amps in the batteris to run my boat for more than 2 hours if everything is in use, but it is not under that kind of load ever. Now i am not electrically minded but do need some sage advice. Other than "buy 6 more batteries and see if it still happens" i have recently on advice fitted a de sulphater(sterling) and the problem still exsists, other advice given was that the dicharged state should be 12.1v any lower and you're in a whole heap of pain.

Usually given as 12.2v but we will not be pedantic, that 12.2v is the given figure for 50% SOC and is the guide figure for the best use/life of a battery but it is not set in stone.

 

Two year old battery bank is about the norm for battery life if of the leisure type, some will get a better life, some worse it all depends on the charging/use and whether it is carried out correctly.

 

My previous leisure batteries lasted two and a half years as a live-aboard CCer. The latest AGM deep cycle have lasted three and a half but I always charge them to at least 95%SOC and once a week charge to 100% SOC.

 

I use a Smartgauge as a monitor.

Link to comment
Share on other sites

You need to do a load test on the batteries and see what capacity is left in the batteries. There is plenty of articles regarding on how to do, but the basics are you fully charge, and use turn on a load that's a percentage of the batteries rating and see how long it takes down to get to a certain voltage (that's around 20% soc). You then fully charge again.

Edited by Robbo
Link to comment
Share on other sites

Simple maths may be fine for calculating discharges but it is far from fine for calculating state of charge over time. The problem is that you have no idea how many of the amps provided have been converted into the chemical change, how many have been wasted as heat and how many have been wasted in gassing. The good thing is that you are quoting voltages and not any state of charge figure your monitor may display.

 

As Bottle says getting a definitive state of charge from a voltage reading requires the batteries to have been rested OFF LOAD for several hours AND for the reading to be taken with no load on the batteries. Otherwise the best you can do is to take an OFF LOAD voltage reading after you stop charging and after a small load has been turned on for (say) 15 minutes.

 

On the basis of what you say I fear your meter might have mislead you to undercharge the batteries in the past so they have now lost capacity. I am also not very happy with the idea of electric cooking on a boat unless it is generator driven or its load is covered by the running alternator(s).

 

I also get the feeling that you may be keen on gadgets. Those desulphaters are, as far as I am concerned, not been proven. Gibbo who used to post here said that when he tested them sometimes they worked, sometimes they did nothing and sometimes they wrecked the battery. I have seen two academic tests that contradicted each other.

 

To emphasise what Bottle says about battery life. My own Exide wet open cells are no three years old and seem to be fine BUT I do have a degree of solar charging when we are away from the boat and I am a bit particular over monitoring and charging when on the boat. The last set of non-Exides lasted two years when a cell failed. Batteries ARE consumables, especially when you have heavy electrical demands. My advice would be to get used to assessing the battery and charging by measuring amps and volts at various times of the day and then when you feel you have cracked it buy some expensive, true deep discharge batteries and LOOK AFTER THEM. I suspect you may haem to buy another six "cheapies" while you get to grips with assessing charging and discharging. If that all sounds like too much trouble then a Smartguage may make it easier for you.

Link to comment
Share on other sites

You have an electrical cooker as well as fridge freezer??

How do you charge your batteries??

 

If you run your engine once a day for an hour to see the state of charge you are getting, the batteries are likely end of life.

The OP said the Cooker around 2amp when on, so guessing it for fan/clock, and not for heating.

Link to comment
Share on other sites

A cross purpose the cooker has an electric fan and electronic ignition otherwise it is cooking wiv gas. I have now arranged to go into a marina for a week so i can take readings from the batteries a couple of hours after charging, as i want this issue resolved before winter comes.

Link to comment
Share on other sites

My charging regime is fairly simple i charge for 8 hours once a month wiv the genny and bat charger to syncronise with the meter then i run the engine 2 hours in the morning and everytime i see the voltage drop i run it for an hour, last thing i charge til the complaints come in or in heavily populated areas have an early night inverter is switched off.

Link to comment
Share on other sites

Others running that sort of charging regime do the 8 hour charge once a week, I very much doubt once a month will be enough, especially with electric refrigeration.

 

I am not clear as to what you mean by by "every time I see the voltage drop", can you be more specific. The voltage will drop to some degree as soon as anything is switched on. If you mean every time the voltage reaches 12.1 then you are not charging enough.

Link to comment
Share on other sites

Bit puzzled by your numbers 7 amps for the fridge freezer and a couple for the cooker, so what uses the other 43 amps.

I would suggest that your fridge freezer alone unless its a very high spec. one will require 3 to 4 hours engine running a day just to replenish it if you are just running on fast tick over.

spilling again

Edited by ditchcrawler
Link to comment
Share on other sites

This is where the puzzling part is. A few weeks ago i came in to find that the bmv was indicating the voltage was down to 9.7v and 17ahc. And everything was still working albeit lights were very dim. It is not a slight drop of .2v but 1/2v.

Link to comment
Share on other sites

 

Two year old battery bank is about the norm for battery life if of the leisure type, some will get a better life, some worse it all depends on the charging/use and whether it is carried out correctly.

 

My previous leisure batteries lasted two and a half years as a live-aboard CCer. The latest AGM deep cycle have lasted three and a half but I always charge them to at least 95%SOC and once a week charge to 100% SOC.

 

I use a Smartgauge as a monitor.

When we sold Innisfree a couple of months ago 8 AGMs were 8 years old and still going strong and that was after neglecting them for couple of years including leaving them disconnected for 3 or 4 months on a few occasions. Much much better than previous el cheapo leisure.

Link to comment
Share on other sites

Take the opportunity to go to the marina and STAY plugged in for a long while -maybe a week! This should ensure that your batteries are as fully charged as they will go. Then rest them and then start checking voltages.

 

It's not unusual for batteries to last two years and they are consumables. Personally I think that your batteries have never been charged to full since you fitted them.

Link to comment
Share on other sites

I can easily believe that a set of batteries two years old can be knackered if not looked after properly.

 

Ours are about two and a half years old and up until this summer had shown no signs of loss of capacity.

 

This summer our battery charger failed and we had a month of never really charging the batteries to full. Since then there has been a noticeable drop in capacity.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.