How Bad Did I Mess Up?

[Madehn]

I left my negative battery cable from my charger disconnected inadvertantly 3 months ago when i was installing an ACR relay to the winch battery- this means that the boat sat at the dock for several months with no charge at all going into the batteries as both solar and wind were systems were turned off-- Bad deal- yesterday i installed a 3 bank digital volt meter to replace the hard to read analog gauge. ALL BAD-- my batteries were down to 11.6 volts-- they are all AGMS with the house bank being four 8D batteries and the starter bank 2 smaller AGMs- winch battery is similar in size to the starter. they are charging now and have come up to 12.5 volts and still going-- have i damaged the batteries? How do I tell? I have an automotive style load tester and plenty of Voltmeters etc that i am comfortable with using. Any help would be appreciated. On a seperate not the charger a 3 bank 1240i (12 volts 40 amps) is only putting a couple of amps per bank into the batteries despite their low charge state ( as measured by a clamp on DC ammeter-- is the charger toast? Seems like it should be giving out its full output with the batteries that low. ( i have other charger hooked up to them right now to get them recharged.)

[MarkJ]

Don't panic. Long and slow.

All you can really do is hope they are ok after you get them up as high as you can.

Certainly don't start pricing new ones yet

PS, we all make mistakes... is a synonym for the word "boat".

[john61ct]

What specific brand/model batteries?

Likely they'll work but at reduced capacity, shortened their lifetime for sure, maybe a lot.

Google 20-hour capacity test, maybe pay a pro do it for you.

[rbk]

Most smart chargers won't charge if discharged too low. If the charger refuses to charge them because they're too low, you can sometimes trick it into charging them by adding a good battery (from your car if 12v) in parallel with jumper cables to bring the volts up to start the process. You may have to do this one at a time, but have done this a few times on various boats. If mixing battery types for this watch closely, you don't usually need to let it sit for long, just long enough to get the process started. Then remove the extra battery and let charge as normal. 11.6 isn't bad, I have one in the jet boat that's down around 10.5 that I have to deal with at some point and that's the route I'll have to take if it works.

[Cheechako]

at 11.6v the batteries should be fine. Not sure why they aren't charging though. Heck, I regularly got pretty low like that on one boat when I didn't charge often enough and the fridge ran overnight. Next am 11+ volts.
But of course those hadn't sat for 3 months...

[JPA Cate]

Had a friend, who, to resuscitate unhappy AGMs, fully discharged them, then slowly recharged, but I have no idea what kind of charger he had, it may have been one of the kind you can tell what to do, rather than expecting it to do it on its own. Anyhow, he did not have to replace them after he did it.

Ann

[Wotname]

I have had some limited success "re-conditioning" AGM by first discharging them to 10.5 V and recharging at a constant current of 1/10 of the stated capacity for 12 to 15 hours. This method of recharging reduces the number of life cycles but will sometimes get some capacity back.

Do keep an eye on any heat build up and stop immediately if battery gets hot or case starts to bulge.

See also http://www.cruisersforum.com/forums/...ck-143949.html

[john61ct]

Originally Posted by Cheechako

But of course those hadn't sat for 3 months...

Yes, huge difference between getting to a low (<30-40%) SoC momentarily, and having them sit there for weeks or months.

[smac999]

if the 40a charger raised them from 11.6 to 12.5v and is only putting out 3 amps your charger is hooped. it should be putting put the full 40a untill the battery hits 14.5 or whatever you've set the bulk level at.

40a is way to small for a 900ah bank. you are during further damage by charging them so slowly. you should throw 200a into them. or one battery at a time with the 40a. agm want /need high current charging

[gamayun]

I did something similar recently when my battery charger died (unbeknownst to me). If you don't have a battery monitor, it's probably going to be a little difficult to see what's happening at the different stages, but you first need to get it up to peak charge (typically 14.1-14.4 V for AGMs), then the current may be very small at the float stage. The only time you'll get high amperage is when the batteries are almost fully discharged. I wrote down and monitored mine every 15 minutes when I was trying to get them back from 10 volts after a few days of full discharge. I know I probably damaged them, and it was a painful lesson to learn, but it has also been quite informative to my understanding of how the AGMs work. If yours had truly discharged to 11.6 V, perhaps you didn't damage them as much as you think....

[fatherchronica]

So much to learn in the rapidly expanding battery world. I have no advice on this except that batteries have memory and I would going through many charging cycles before I threw up my hands. They will either come back most or all of the way, or you will get used to some level of reduced capacity and not know the difference anyway. I had a friend, a cheap friend, who used to get discarded lead acid batteries and saw the bottoms off with a hacksaw, carefully clean the lead residue from between the plates that was in effect shorting out the battery, glue the bottom back on with silicone, and refill and charge it and install it into vehicles or to his solar panels. More of an exercise in self sufficiency than a monetary need, but interesting to me.

[S/V Alchemy]

Originally Posted by fatherchronica

So much to learn in the rapidly expanding battery world. I have no advice on this except that batteries have memory and I would going through many charging cycles before I threw up my hands. They will either come back most or all of the way, or you will get used to some level of reduced capacity and not know the difference anyway. I had a friend, a cheap friend, who used to get discarded lead acid batteries and saw the bottoms off with a hacksaw, carefully clean the lead residue from between the plates that was in effect shorting out the battery, glue the bottom back on with silicone, and refill and charge it and install it into vehicles or to his solar panels. More of an exercise in self sufficiency than a monetary need, but interesting to me.

Rapid expansion suggests an overcharge!

[a64pilot]

Find Lifelines manual online, it easy, look in their manual for "reconditioning"

This is cut n paste their definition
A special constant current charge process used to restore a battery’s capacity after extended storage periods or deep discharge exposure. Also known as reconditioning.

Manual address
https://www.google.com/url?sa=t&rct=...wvU1vjSROwP_fA


Page 20, sections 5.5 and 5.6 are of interest to you



This is of course for a Lifeline battery, but may be applicable to yours?

[LoudMusic]

For people who leave their boat unattended for weeks at a time, do you do anything to remote-monitor it? Like a moisture meter in the bilge, a volt meter on the battery, and gps transponder that can all be checked remotely? Maybe even cameras?

[Suijin]

Last winter my boat was up on the hard and plugged in and I left it for almost five months. During that time some $%&hat disconnected my shore power so they could use the plug. When I came back the batteries were dead as doornails, down around where yours were. Four four year-old Lifeline 31's. Plugged her back in and a week later they are up to high 13's With a Xantrex 40 amp charger. Can't comment on the slow charging as I did not monitor mine during that week.

They definitely took a hit based on my heavy use of them since and comparison to prior experience with them. I'd say they are at 80% of what they were before the incident. They had been very well cared for up until that point and were still very strong.

So no, they are certainly not toast, but they're not going to be very happy with the experience.