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Battery power


DaveR

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Good day,

 

Well we ran out of battery power this morning and I was most concerned. Yesterday, after a good days engine run for moving, this should not have happened - or I believe it should not. The charge ammeter (large faced moving coil via a shunt) at the end of the days run was showing hardly an Amp or two. However at 0830 this morning the inverter was complaining & the battery voltage was down to 11.6v On stopping the inverter (running a 700w toaster) the batteries recovered, within seconds, to 12.4v

 

This afternoon, I switched off the solar panels 30 minutes before taking battery SGs of the now 6 years old 110Ah units. I was most surprised to find 1 sealed 110Ah unit hidden at the back of the line of wet cell units. Anyway the SGs obtained from the 5 wet cell batteries are all between 1.275 & 1.3 for all cells.

 

Questions, was I right in leaving 30 minutes after switching off the solar cells and doing the readings? The MPPT was showing 9A charge at the time I switched them off.

I have no idea where the sealed unit came from nor how old it is. If this has reached the end of its life could this be dragging the other batteries down?

If yes and I disconnect the +ve terminal, do I also have to disconnect the -ve?

 

Set up is a Beta 43 with a 95 Amp alternator for the domestics. This is controlled by a Sterling 4 step digital charge controller. 4 solar panels through a 40A MPPT controller all from Onboard Solar. The inverter is a 3kW pure sine wave unit from Sunshine Solar.

 

Thank you

Dave R

 

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The sealed battery might be the starting battery so a photo of the batteries showing the connections or a carefully drawn diagram.

 

The difference in cell readings from a hydrometer should be no more than 0.03 or 0.025 for Lucas. So you may have a shorting cell.

 

9 amps suggest that the bank was well charged but not fully charged unless it is between a 450 and 900Ah bank.

 

You need to monitor the charging amps throughout the day. A fast charge and fast discharge suggest sulphation as does a discrepancy between the state of charge implied by  rested voltage and the hydrometer reading. A slow charge and fast discharge suggest a shorting cell or cells.

 

 

 

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Six years is a very good life for 110 amp batteries anyway. Even if they spend most of their life in a marina on a maintaining charge regime. Sounds like they are sulphated and charging up quickly but discharging even more quickly due to loss of capacity. 

Edited by mrsmelly
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Thank you for the thoughts, Tony, the starter battery is beside the domestics - the sealed 110 is with the domestic bank.

 

Anyway, as suggested 6 years is not bad so I guess I will be shopping soon.

 

Regards

Dave R

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I would disconnect the sealed battery and see what happens. You just need to disconnect either the + or the -, you don’t need to disconnect both. If you disconnect the +, do it at both ends so it can’t short to hull.

 

But I would also observe from your description that 700w inverter drain (about 70A from the 660Ah of batteries) caused a 0.7v drop and when that drain stopped, the 12.4v voltage indicates quite a reasonable remaining state of charge. Therefore I would check for any slightly poor connections in the wiring that could drop voltage under a high current load. Try to check the difference between the inverter voltage and the battery terminal post voltage using a multimeter when the toaster is on. A favourite source of bad connection/voltage drop can be the battery isolator switch, especially if is the red plastic key type.

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Well that did not work. 3am the inverter is complaining, I took the voltages 12.5 at the batteries, 12.5 at the inverter but when the fridge compressor tried to start . . . 9.2v.  Guess they are shot.  Why do they go down hill so quickly?

 

Right now to put my battery buying research into action & get 6 new ones + a new starter. They are all the same age (except the rogue one) I might as well do them all in one go.

 

7 batteries, Pass the hankie, I need a cry.

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18 minutes ago, DaveR said:

Well that did not work. 3am the inverter is complaining, I took the voltages 12.5 at the batteries, 12.5 at the inverter but when the fridge compressor tried to start . . . 9.2v.  Guess they are shot.  Why do they go down hill so quickly?

 

Right now to put my battery buying research into action & get 6 new ones + a new starter. They are all the same age (except the rogue one) I might as well do them all in one go.

 

7 batteries, Pass the hankie, I need a cry.

My 4 x 130 ah AGMs did exactly the same a couple of weeks ago. Look on the bright side,  I got £50 back on the empties.  

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17 minutes ago, DaveR said:

Why do they go down hill so quickly?

 

 

Because they now only have a fraction of their original capacity because of potentially poor charging and being left partially charged, so sulphation can occur.

 

Your (probably) 990Ah nominal capacity may not be less than half that now.

 

It sounds as if your electrical demands are very high so maybe fit a  decent digital voltmeter and ammeter (a battery monitor will do as long as you ignore all but volts, amps, and Ah out) so you can monitor battery usage and charging. However, six years is  a very good life for run of the mill leisure batteries.

 

 

 

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