Battery advice

[Angus Wolf]

Hi all,

 

I have a query in regards to my batteries that I hope someone might help me with.

 

I currently have a set up of 7 batteries. I charge then using a 2kw generator. When I turn the genny on they go to 99%.

 

I also have solar panels that when the day is sunny take the batteries to 99%

 

Now the problem I find is that whenever I put an appliance on. Say my laptop with 12v charger the battery percentage drops suddenly. It seems to plumit very quickly.

 

On days where I use very little power the battery goes from 99 - 65

 

And in the morning it's always very low.

 

I am very conscious not to ruin my batteries but I want to be able to use more power and surely I should be able to??!!

 

Any help would be greatly recieved

 

Thanks

[ditchcrawler]

How are you measuring your state of charge?

[Angus Wolf]

I'm using the reading on what I belive is the solar charge controller

[Rob-M]

When you say you use little power some days what do you actually have using electricity...? That sounds a heavy drain for something you class as little use.

[Angus Wolf]

I would say on an average day. Maybe 30- 60 minutes 12v iphone charger. One or two lights on for an hour roughly. Water pumps for washing up and one shower per day.

[Rob-M]

It sounds to me like the batteries aren't actually charged to the level you think or they are already knackered and not capable of holding a charge anymore. Have a search of the Forum and you will find plenty of threads relating to measuring specific gravity which should give you an indication of their state.

[Richard10002]

Your solar charge controller reading is obviously not a battery state of charge monitor. It probably uses instantaneous voltage to suggest a state if charge and, if this is over about 12.8 volts, it will report the batteries as fully charged.

 

However little you use, they will not be 99% when you start the generator, or solar charging commences.

 

What make and model of charger is the generator feeding? My Honda 2kw Genny feeds an 89A Sterling inverter charger, so I get lots of Ah when I first start charging, but this falls to about 10Ah and less as they get close to fully charge.

 

You need to charge for much longer with your Genny, and you will only really know how long if you get a proper battery monitor, and understand a bit about how it all works. Perhaps a Smartguage would be the best investment as this magically calculated what users seem to trust as a reasonable stab at %age state of charge.

Edited August 17, 2015 by Richard10002

[matty40s]

How old are your batteries??

 

If you are using a Tracer MPPT controller and have the separate panel, the state of charge reading is complete bo77oc9s.

To get a true reading of your battery bank state, you need a decent gauge like a smartgauge of a NASA gauge.

[nicknorman]

As above, the SoC reading you are referring to, is almost certainly meaningless. Quite probably, your batteries have not been properly charged for a long time. The only question is. Is this situation recoverable from (by proper and full charging) or are the batteries now knackered due to chronic under-charging.

 

You need first to devise a better method of determining the state of charge.

Edited August 17, 2015 by nicknorman

[Arthur Brown]

Charge the batteries from a stated SOC to full, Count the time taken and measure the actual current put into the batteries. It's likely that your batteries are either not new and their capacity has decreased which is one "end of live" symptom or the metering doesn't tell the whole truth.

 

Accurately measure the current going out of the battery regularly -spend half a day recording the meter readings every few minutes You could be looking for unexpected small currents or occasional large currents. It's the small currents flowing 24/7 that actually make a LOT of difference to battery state.

 

With a set of seven batteries it's too hard to wire them for exactly equal current distribution, it's possible that one heavily loaded battery is failing and drawing power from the others hence flattening the battery bank "internally". Don't make a diagnosis based on one reading, make several (or more!).

[IDS]

To diagnose your battery health and state of charge you need a Hydrometer. Fully charged cells have a specific gravity of 1.265 to 1.280 (depends on battery type and temperature) Check all individual cells, look for any that are significantly different from others in the battery, which will indicate faulty cells. You will find tables of specific gravity on the internet that will help you understand what is going on with you battery bank. Just google 'lead acid battery' .

Terminal voltage can also be used to monitor state of charge, but not accurately when the battery is in use either charging or discharging. It is recommended to monitor the voltage after charging, but let the battery rest for 6 to 12 hours with no load before measuring. There are numerous provisos with this method including temperature and battery type, but it is a good way to get to know your batteries. Again the internet will provide tables to help determine the state of charge from the measurement.

If your current state of charge monitor is only measuring voltage then it will always be fooled if current is being charged or discharged.

[Tony Brooks]

Add to the above if the estimated state of charge from an off load or virtually off load voltage reading (at least an hour after charging stopped) shows a significantly higher state of charge than that shown by a hydrometer your batteries are probably sulphated badly and at or very near the end of their life.

 

Take great care not to splash acid about when using the hydrometer.

 

If this is a Stecca solar controller I think you can set it to another type of display giving voltage, battery voltage, solar charge, and and another fairly useless aggregate reading (think it may be Watts to date). Set it to that any use voltage readings last thing at night and before it gets light in the mornings to monitor battery voltage and thus state of charge. Ideally it would be easier to also have an ammeter to monitor the charge and to keep charging until it is between 1 and 2% of battery capacity. Otherwise fit a Smartgauge.

[Angus Wolf]

Hi all

 

Firstly thank you all so much for your advice. It has been extremely useful and I feel confident with what I should do next.

 

In response to a previous question I am running. 2 kW kipor generator through a victron multiplus.

 

I am going to buy a hydrometer and smartgauge this week and give them a go/ hopefully begin to get to the route of the problem.

 

If I have any trouble I will be sure to ask you again for your kind advice!

 

I will also keep you posted with my progress

 

Thanks again,

 

Angus

[Richard10002]

Make and model of charger?

[bottle]

Victron multiplus as mentioned in previous post. (#13)

 

As to size no idea.

[FidoDido]

Tracer SOC complete work of fiction.. Can often say 60% when my mastervolt MICC tells me it's 90% or more.. Think it goes off voltage only, and that obviously changes with load.

 

A decent monitor is needed. Unfortunately they are not cheap.

[Bod]

Hi all

 

Firstly thank you all so much for your advice. It has been extremely useful and I feel confident with what I should do next.

 

In response to a previous question I am running. 2 kW kipor generator through a victron multiplus.

 

I am going to buy a hydrometer and smartgauge this week and give them a go/ hopefully begin to get to the route of the problem.

 

If I have any trouble I will be sure to ask you again for your kind advice!

 

I will also keep you posted with my progress

 

Thanks again,

 

Angus

Fitting a Smart Gauge is the simplest way of getting a SOC reading. Despite what some on here would like say, the readings you get after it has settled down (allow about 5 cycles of charge/discharge) will be an accurate reflection of the state of your batteries as a whole.

As Gibbo would have said, like it or lump it, that's how it is.

Hydrometer reading from every cell will find any bad cells, that battery will have to be removed. ( assuming you have unsealed batteries)

 

Bod

[dmr]

Add to the above if the estimated state of charge from an off load or virtually off load voltage reading (at least an hour after charging stopped) shows a significantly higher state of charge than that shown by a hydrometer your batteries are probably sulphated badly and at or very near the end of their life.

 

 

Is this correct? Its very interesting and I have not really thought this through.

If a battery is sulphated then some of the acid is permanently locked into hard sulphate so the specific gravity will be low. But this is just like a part discharged battery so why would the settled off load voltage indicate a higher charge????

 

...........Dave

[Tony Brooks]

 

 

Is this correct? Its very interesting and I have not really thought this through.

If a battery is sulphated then some of the acid is permanently locked into hard sulphate so the specific gravity will be low. But this is just like a part discharged battery so why would the settled off load voltage indicate a higher charge????

 

...........Dave

 

Because the remaining lead oxide is or should be properly charged, that gives you the voltage but not the capacity.

[Guest]

 

Because the remaining lead oxide is or should be properly charged, that gives you the voltage but not the capacity.

I think that describes my present batteries nicely. I am currently nursing them, hoping they will last until autumn, but they have a very low capacity now, and the inverter takes them down in minutes. That said, they owe me nothing.

[valrene9600]

Hi all

Firstly thank you all so much for your advice. It has been extremely useful and I feel confident with what I should do next.

In response to a previous question I am running. 2 kW kipor generator through a victron multiplus.

I am going to buy a hydrometer and smartgauge this week and give them a go/ hopefully begin to get to the route of the problem.

If I have any trouble I will be sure to ask you again for your kind advice!

I will also keep you posted with my progress

Thanks again,

Angus

I read this as you are shutting down gennie soon after seeing the make believe SOC on solar controller.

To be clear just how long are you running the genny to charge the 7 batteries.

[Chewbacka]

My MPPT display for soc also goes down very quickly. I think this is because it works by measuring the voltage and as it has no understanding of the load on the battery - inverter etc, it reads a lower voltage and shows low soc. So your batteries may not be as bad as you think.