battery computer mystery

[snowleopard]

i have a 'heart 10' battery computer which measures current in and out of a battery and gives a running total of the number of amp-hours required to recharge. it has always been pessimistic, saying the charge required is higher than it really is.

it resets itself to zero when charging voltage stays above about 13.5 for 15 mins and current is below 6A (i.e. battery full), it is then supposed to re-calculate the efficiency factor of the charging and give a more accurate reading next time.

i recently left the boat with the batteries fully charged and the master switch off so there was no load but the computer was still on-line. 3 weeks later the computer shows a deficit of 250AH (from a total of 330) but when i started up the charge voltage went straight to 14v, as per adverc controller specs, and current was only 9A, indicating the batteries were pretty full.

anyone had trouble with this unit? and no, i don't believe it is wired wrong.

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[pvb]

Link 10...

I fitted a Link 10 about 7 years ago, and I haven't had any problems with it. Are you sure the display was set to show Ah, and wasn't showing the Time Remaining setting?

I have heard of an instance in which an alternator fault caused a significant discharge to build up on a Link 10, whilst the boat was unattended. It's possible that such a fault might reduce the current output of the alternator and make you think the batteries are more charged than they actually are. Best way to find out is to use a mains charger to totally recharge them, and then monitor what happens in future.

Incidentally, the Ah display shows the actual Ah used, not the Ah required to recharge (which will be more, depending on the charging efficiency). The charge efficiency factor is only recalculated by the meter if you've first discharged at least 10% of the batteries' Ah capacity as programmed into your meter - otherwise it'll just use a default setting of 90% CEF.

As you're using an Adverc regulator, you might consider reprogramming the meter with a slightly higher Charged Voltage Parameter.

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[snowleopard]

Re: Link 10...

yes, it's definitely showing AH, when i went to the boat yesterday the LED indicators were showing one flashing red where they had been on 4 green last visit. i have a sterling mains charger also - no difference in effect.

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[pvb]

Looks like...

Looks like there's a fault somewhere then!

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[Oldhand]

I don't know the "Heart 10" but have a Link 10 battery monitor. I'm wondering if there is a current shunt fitted to measure current flow by the voltage drop across it. Ther could be a bad connection or corrosion on the shunt connections giving a much larger voltage drop across the shunt than there should be. Suggest you check the "sensor" end of the system.

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[HaraldS]

puzzeled as you are. Have a Link 10, think it's the same. Behaves as you describe: Slightly pessimistic. Haven't left it without charging for a long time so I don't know what mine would do in that case. Don't think it accounts for self discharge at any rate, at least the manual says nothing about it.

Best guess is to think about Amps as volatge drop on the shunt and thus possibly a loose or corroded wire, rather than real current flow.

If 'this problem doesn't reoccure, the unit might have been confused by strong RF. Did you opereate your SSB before you checked Ah maybe??

Sorry no real good idea.

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[snowleopard]

yes, the unit is also known as the Link 10.

Could be bad contacts around the shunt but doesn't explain why it registers discharge while the battery is disconnected! i haven't transmitted on the ssb since the last reading so it can't be rf interference. time for some serious investigation with a multimeter. i wonder if moisture is causing bad resistance readings.

thanks all.

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[HaraldS]

just a thought: I think the recommendation in the manual is to run separate wires form the shunt for measuring current (volatge drop), measuring voltage, and supplying power to the Link-Monitor.
So, supply voltage and volatge measured have a minus pole connection in common and a plus connection most liklely in common, either battery or user side of the shunt. Now if the supply one is connected on the user side, maybe together with the current sense line, and has a corroded connection, the voltage drop over the corroded area, caused by the power consumption of the link would give you a reading like you saw.
When al is turned off, is the monitor showing any current drain from the batteries??
That's my best guess.

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[jfkal]

Hi Have the same problem. Interesting is that it affects only one battery bank. Goes down to red LED in a matter of 5 days. Batteries are new. Unit wired correctly. A mystery to me as well

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[pvb]

Are the batteries actually discharged?...

...or does the Link 10 meter just say they are?

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[snowleopard]

Re: Are the batteries actually discharged?...

no i'm sure they were pretty full, hence only charging at low rate with 14v. if they were really that flat i would expect to get 40A or more at 13-13.5v

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[jfkal]

Re: Are the batteries actually discharged?...

Yep. That is my suspicion since the batteries are pretty new.

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[pvb]

How is your alternator wired?...

Two thoughts on possible discharge causes linked to the alternator. First, faulty diode could allow discharge - is alternator output direct to batteries (which would allow discharge when main switch is off) or is it isolated by main switch? Second, some alternators need a field disconnect relay when used with smart regulators, otherwise there's a discharge via the field winding.

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[snowleopard]

Re: How is your alternator wired?...

charging is through the master switches and all three were off while the boat was not in use so it couldn't be the alternators, or the wind gen or solar panels.

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[Robin]

Re: How is your alternator wired?...

You can check if there is an unknown drain despite the switches being off. Use a digital multimeter with current measuring facility (ours goes to 10A), disconnect the battery lead and conect the multitester between this lead and the battery, it should read zero. Our engine battery seemed to self discharge and when tested I found a 0.5A drain - some plonker had wired a lead from the Off switch (live side) to the alternator warning light connection, this also explained why on a really dark night you could see a faint glow from the warning light with everything turned off and no engine running! Once this lead was removed the battery stays well up and there was no effect on alternator performance, via Adverc regulator.

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