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Will dead batteries come back to life?


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Just been over to the boat. Something (possibly the fan heaters I'd left switched on, controlled by thermostat) seems to have tripped out the shoreline. The batteries now appear dead. I've got the shoreline going again and the batteries are now charging via the inverter. My question is... will they recharge and be OK or have I killed them? I have a bank of three + a starter battery. All were new this time last year. Thanks.

Charlie.

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Ahhh another dreaded battery question. It will depend methinks on how flat and for how long? Batteries get very pissed off if mistreated, they are like teenage girls!!

If they are Trojans you will never recover them because you have not been reading them a bedside story and tucking them up in bed.

I have had in the past very flat batteries that have recovered and been used again but you are somewhat in the lap of the Gods. Some pucker battery bods will soon advise though.

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I think you may be a little confused about what does what.

 

An inverter will flatten batteries.

A battery charger will charge batteries

 

An inverter will not charge batteries.

 

If the heaters were plugged into the 220v landline how did they flatten your batteries ? (you wouldn't leave them plugged into an inverter would you ?)

 

If the batteries have been totally flattened, and left in that state for some time (days / weeks) then they are most probably past resuscitation.

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I think you may be a little confused about what does what.

 

An inverter will flatten batteries.

A battery charger will charge batteries

 

An inverter will not charge batteries.

 

If the heaters were plugged into the 220v landline how did they flatten your batteries ? (you wouldn't leave them plugged into an inverter would you ?)

 

If the batteries have been totally flattened, and left in that state for some time (days / weeks) then they are most probably past resuscitation.

Automatic changeover to batteries if mains is tripped? Just a thought

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I think you may be a little confused about what does what.

 

An inverter will flatten batteries.

A battery charger will charge batteries

 

An inverter will not charge batteries.

 

If the heaters were plugged into the 220v landline how did they flatten your batteries ? (you wouldn't leave them plugged into an inverter would you ?)

 

If the batteries have been totally flattened, and left in that state for some time (days / weeks) then they are most probably past resuscitation.

OP will have meant an inverter/charger, as you probably realised Alan. When left on shore power some inverters will auto switch to battery power if the shoreline gets interrupted.

 

Ian.

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I think you may be a little confused about what does what.

 

An inverter will flatten batteries.

A battery charger will charge batteries

 

An inverter will not charge batteries.

 

If the heaters were plugged into the 220v landline how did they flatten your batteries ? (you wouldn't leave them plugged into an inverter would you ?)

 

If the batteries have been totally flattened, and left in that state for some time (days / weeks) then they are most probably past resuscitation.

 

 

 

 

OP will have meant an inverter/charger, as you probably realised Alan. When left on shore power some inverters will auto switch to battery power if the shoreline gets interrupted.

 

Ian.

 

 

This seems to fit the OP's description. Something tripped the shoreline and the combi switched over to batteries as the power source, and rapidly draiend them flat.

 

I'd have expected a decent combi to be clever enough not to fully drain the batteries though, and to turn OFF at say 12.0v

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I had a sterling that did precisely that and nearly trashed my batteries on a previous boat, a damned stupid idea.

I am sure these auto changeovers are fine if you know it has switched,and its not left un-attended with a load on. Give me a manual changeover anytime!

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It entirely depends on the batteries. With some a single discharge to zero will kill them stone dead - you can charge them up but they'll have no capacity. Others will be more forgiving.

 

The only way to know will be to charge them up and see. They may well also require equalising if they're open wet cell.

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I am sure these auto changeovers are fine if you know it has switched,and its not left un-attended with a load on. Give me a manual changeover anytime!

 

I am one hundred percent in agreement. This boat is way better and fitted by a very knowledgable boatyard owner for his own liveaboard use. It has plenty of leccy kit BUT everything is via a manual switch so I know exactly what is on and can isolate each item, the only drawback is the combi but this is a clever one so nothing can drag batteries down much as it is set to shut down at 11.9 volts and this can be set to any voltage within reason. I was onboard with the washing machine running when the shoreline on previous boat went off when the whole marina tripped, luckily I heard the combi fans screaming and realised somett was amiss and switched it all off before screwing the batteries.

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Apologies for any confusion. It is indeed a combi - can't 100% recall model but it's a 3000W Victron. And yes, I'm assuming that it switched to battery power when the shoreline tripped out, and that the fan heaters came on when the temp dropped and drained the batteries.

 

My 3000W Victron has a "charger only" setting, which I use when leaving the boat unattended to prevent this from happening.

 

You can also set the low voltage trip setting. Mine is set to 12.0 volts. Default setting is set to trip 10.5 volts IIRC.

 

 

It entirely depends on the batteries. With some a single discharge to zero will kill them stone dead - you can charge them up but they'll have no capacity. Others will be more forgiving.

The only way to know will be to charge them up and see. They may well also require equalising if they're open wet cell.

Exactly, cheap batteries will die when discharged fully, others, such as tractions, semi-tractions and quality AGM's will recover with only a slight loss of capacity, provided they are put on charge very soon after the end of discharge.

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My 3000W Victron has a "charger only" setting, which I use when leaving the boat unattended to prevent this from happening.

 

You can also set the low voltage trip setting. Mine is set to 12.0 volts. Default setting is set to trip 10.5 volts IIRC.

 

 

 

 

 

We have a 220v socket wired into the feed BEFORE the combi, this allows 220v land-line to be left 'on' at all times, but, with the combi switched 'off' to avoid discharging the batteries if the mains supply is disconnected.

 

I believe that electric 'fan heaters' would invalidate your insurance (worth checking).

We use the tubular 'greenhouse heaters' which cannot 'fall over'. Insurance co happy with them.

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I always leave a couple of fan heaters plugged in to the shoreline during the winter. Their advantage is that unlike tubular heaters the fan ensures that the length of the boat and not just in the area close to the heater.

 

The insurance company's view, when I asked them, was that it was a good idea provided that they were good quality heaters in that they have overheat protection built in (to ensure that the power is cut off if the fan should stall) and that the manual does NOT state that it must not be left unattended. Heaters meeting these criteria are slightly more expensive but are readily available.

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I recon they they'll charge up alright with a powerful garage type boost charger to kick em off. Wet cell batteries in battery wirelesses were charged up from almost dead flat and so were batteries used for lights in sailing yachts with no aux engines. The American electric car of 1914 used ordinary 12v wet cell batteries which charged up from almost dead flat. They had a range of 80 miles, so nothing new. Just learned about it on ''Chasing Classic cars'' on freeview Quest 37.

Wartime submarines also often flattened their batteries when forced to remain submerged for long periods by being hunted and bombed at by their enemy. But managed to charge em up again when the engines were running on the surface at night. The crews also ate tons of carrots to improve their night vision.

Edited by bizzard
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A friend of mine had his batteries flattened when the boatyard after doing some work and moving the boat and didn't wind the stern greaser down afterwards which they were requested to do. By the time my friend visited again the bilge pump had flattened the batteries. The boat yard took them into the shed and after managing to set their battery charger alight managed to recharge them. The worked OK for a while before dying again a short time later.

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Don't give up hope. I had a set of ordinary basic batteries which were flattened because I forgot to turn the isolator off and the fridge light (door left open) flattened the batteries quite quickly. Left like this for a couple of weeks. After a good charge they were OK and lasted another two years ( off grid). So you may be lucky.

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