Battery discharge

[Porthandbuoy]

I replaced 3 x 110 Ah lead acid batteries when I bout Sheolin. These batteries had been ignored totally for 5 or 6 years and showed zero volts when I put a multimeter across them.

Step 1: Thinking 'nothing venture, nothing gained' I hooked one up to a 15A Cetek smart battery charger. No good. The charger didn't even recognise a battery was connected.

Step 2: I put an old 12V battery, which held some charge, in parallel with one of the duff ones and hooked up the charger. This time it worked, recognised a battery was connected and started shoving some amps in. After a while I disconnected the old batter and the duff one continued charge. The charger completed it's charge cycle and I then selected 'Recondition'. After an hour or two that was completed and the battery showed 13.2 decaying to 12.7 overnight. Result!

Step 3: Repeat Step 2 with 2nd duff battery. It recovered as well.

Step 4: Repeat Step 2 with 3rd duff battery. Not such a good result. This one went into some sort of thermal runaway and began to hiss and spit and distort alarmingly. Dropped it in the water butt to cool down.

Still, two out of three isn't a bad result @Jayayecee, your's might recover, but don't leave it on charge unattended.

Batteries 1 & 2 are still holding their charge. I did a drop test on them and I reckon they're down to around 80~90 Ah.

 

[Refueler]

I replaced 3 x 110 Ah lead acid batteries when I bout Sheolin. These batteries had been ignored totally for 5 or 6 years and showed zero volts when I put a multimeter across them.

Step 1: Thinking 'nothing venture, nothing gained' I hooked one up to a 15A Cetek smart battery charger. No good. The charger didn't even recognise a battery was connected.

Step 2: I put an old 12V battery, which held some charge, in parallel with one of the duff ones and hooked up the charger. This time it worked, recognised a battery was connected and started shoving some amps in. After a while I disconnected the old batter and the duff one continued charge. The charger completed it's charge cycle and I then selected 'Recondition'. After an hour or two that was completed and the battery showed 13.2 decaying to 12.7 overnight. Result!

Step 3: Repeat Step 2 with 2nd duff battery. It recovered as well.

Step 4: Repeat Step 2 with 3rd duff battery. Not such a good result. This one went into some sort of thermal runaway and began to hiss and spit and distort alarmingly. Dropped it in the water butt to cool down.

Still, two out of three isn't a bad result @Jayayecee, your's might recover, but don't leave it on charge unattended.

Batteries 1 & 2 are still holding their charge. I did a drop test on them and I reckon they're down to around 80~90 Ah.

You have highlighted one of the problems of smart chargers ..... they look for voltage suitable for the battery mode you select ...

You can take it further ... if you have one that does 6v as well as 12v ... you can literally connect to a 12v battery that shows less than 6v ... charger goes into motorcycle 6v mode ! Done it - got the T shirt.

Its an old trick to fool smart chargers by connecting a battery that has some charge in it ... and as you found - once old battery has sufficient - you can disconnect the 'donor' battery.

But if you can find an old 'dumb' charger that just pumps x amps in without smart modes - then that will do the job.

De-sulfator units - the ones that you connect additional to charger ... they do not like smart chargers .. actually smart chargers don't like them ... usually causes charger to default off when de-sulfator pulses. Done it - got the T shirt !

Smart chargers are of course better ... they change mode as battery charges ... they can maintain a battery ... some have recovery mode ... but one 'mode' I look for is restart mode when battery charge drops. Many smart chargers - I'm talking car etc. now - once battery is full they drop to trickle or switch off. If battery then is used and charge drops - the charger fails to restart charge. You have to restart it.

 

[MontyMariner]

You have highlighted one of the problems of smart chargers

I hang on to an old transformer supplied 12v charger along with my modern 3 stage charger for when all else fails.
It has room in the case for me to add a chunky capacitor to help smooth the output.

 

[Scotty_Tradewind]

Normally when the boat is on the berth we leave the fridge switched on and the battery charger plugged in. However, this time the mains supply failed and the fridge was left running on the domestic battery for two weeks. The terminal voltage had fallen to 6.5V. My question is will the domestic batteries be permanently damaged or will they recover when recharged? This is the only time something like this has happened normally the batteries are kept fully topped up.

sounds as if you need solar back-up.
Wind generators useless for many days on end and if you cannot sail well in a breeze, then that's also when a wind generator won't charge well either, especially if you're expecting to have a fridge staying cold.

 

[Refueler]

I hang on to an old transformer supplied 12v charger along with my modern 3 stage charger for when all else fails.
It has room in the case for me to add a chunky capacitor to help smooth the output.

Its getting harder and harder to find a bog standard charger ...

 

[Stemar]

sounds as if you need solar back-up.
Wind generators useless for many days on end and if you cannot sail well in a breeze, then that's also when a wind generator won't charge well either, especially if you're expecting to have a fridge staying cold.

An electrical engineer friend compared the expected annual output from a fairly modest solar setup (50w, perhaps) and a Rutland wind generator for the south of the UK. Solar came out comfortably on top. It also has the advantages of being silent, easily expandable and having no moving parts

 

[Refueler]

After last weekend, I can confirm that it didn't.

While I'm deciding what to do ... I shall be fitting one of these into the fridge power line ....

rated to 10A ..... just as a stop gap to avoid discharging my batts down again so low.

Banggood : DC 12V Battery Undervoltage Low Voltage Cut off Automatic Switch Recovery Protection Module Charging Controller Protection Board

 

[B27]

I know the undervoltage protection built into my fridge works, because it operated quite often until I upgraded the wiring.
The volts tend to dip a bit as the fridge fires up, so getting the trip voltage right might be fiddly.

 

[PaulRainbow]

While I'm deciding what to do ... I shall be fitting one of these into the fridge power line ....

rated to 10A ..... just as a stop gap to avoid discharging my batts down again so low.

Banggood : DC 12V Battery Undervoltage Low Voltage Cut off Automatic Switch Recovery Protection Module Charging Controller Protection Board

That's not likely to be long lived with a fridge, the startup current will likely kill it off. Add a cheap automotive relay with a higher current rating.

 

[VicS]

That's not likely to be long lived with a fridge, the startup current will likely kill it off. Add a cheap automotive relay with a higher current rating.

I notice it is rated for resistive loads only so not only the startup current but also the voltage spike generated when it de-energises.

 

[ChromeDome]

Swift answer is no.
Various snake oil tablets etc. appear year after year, believe, none work.

Just like arthritis. Not reversible

 

[Stemar]

My fridge has a low voltage cut-off, but the "high" level is 11.1v, with lower voltages available. It did cut out, but that's way lower than I want to take a LA battery. Since I'm unlikely to need the fridge before next April at the earliest, I'll leave things as they are for now and, when the batteries die, consider the next step, which could very well be Li, given the way prices are falling.

 

[Refueler]

That's not likely to be long lived with a fridge, the startup current will likely kill it off. Add a cheap automotive relay with a higher current rating.

I have an auto relay on my cool box in other boat .... so its a point I appreciate.

I plan to check by Wattmeter - I have various that display peak current and steady ... before any installation.

Its not something I will be fitting for a while anyway - so have plenty of time. Likely result will be using the cut-off on the relays detection side ... while high power feeds through the other. That way cut-off unit never sees high current.

 

[pandos]

My three batteries which I bought in 2006. have been totally discharged many times. I replaced two of them 2 years ago and shifted one of the original house batteries for us as the starter battery...

They never gave me any trouble but over time the capacity did drop. The ones I fitted last I had bought at one year old from a guy with a camper. They are 120amp versus the original 80amp, so 240ah versus160ah.

It may be imagination but I think my older smaller batteries had better capacity, certainly in use the voltage drops off quicker now.


But everything stays working so I don't worry.

But then I am a cave man I have splitter diodes and a 1 2 both switch.

All the batteries are AGMs. To get them up from zero volts, I used an old caravan charger and also a desulphator.

 

[PaulRainbow]

I have an auto relay on my cool box in other boat .... so its a point I appreciate.

I plan to check by Wattmeter - I have various that display peak current and steady ... before any installation.

Its not something I will be fitting for a while anyway - so have plenty of time. Likely result will be using the cut-off on the relays detection side ... while high power feeds through the other. That way cut-off unit never sees high current.

Another option is to connect the 10a relay to the thermostat wiring.

 

[Refueler]

Another option is to connect the 10a relay to the thermostat wiring.

mmmm tbh - without further look in the cabinet - was one of the ways I considered.

No way did I think to have as a protection for whole boat of the battery ... much as I'd like whole boat to be less than 10A !!

My thoughts were either power to the fridge compressor or as you say - the controller.

The system must be quite old as the main control is without any display .. its a rotary control - supposed to vary the temp. So far I have noted that it cools to about 9C whatever its set - but at max will drop past 5C .... I have suspicion that it will not freeze anything ... its just a fridge.
Temp is shown by a separate temp display similar to a house internal / external item.

The blue switch behind the towel holder (left) is the main control, while temp display is right at back centre ..

Will be interesting to sort out where to fit unit. Maybe an updated controller could be fitted .... will see.