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Post by lollygagger on Dec 26, 2016 11:22:16 GMT
It's not really a conundrum, but the thread title is better like that. Ze equipment: Mastervolt 80a/12v charger. 2x Mastervolt 200ah gel batteries, old. Since I got the boat 6-7 months ago it's been plugged into the mains. Sometimes I switch the charger off for a couple of days, then when I've used about 50ah I switch it on. It goes through it's phases of charging then sits there topping up the batteries. All they are used for is fridge, lights and pumps, max draw always below 10a apart from one time about 3 months ago when the meter ran out and the inverter ran the washing machine for less than a minute, it was pulling 150a and I had no interest in seeing if the system coped. Roll on Christmas eve and I noticed the fan in the charger running which it doesn't do when it's just keeping the batteries topped up. The meter showed it was providing 6a, normal for fridge plus a few lights. I switched off, let things run on the batteries until yesterday during which time the meter counted out the usual amount of ah. Switched charger on, it went through it's normal routine but didn't get to topping up. It has 4 lights, the last one didn't come on as normal. The battery I can get at is warm. It's never been warm before. The charger is switched off again. The batteries are knackered aren't they? I thought I was doing OK. They are very old but I hoped/expected they'd fade out rather than wham bam. What have I done wrong? There was £1k of batteries there.
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Post by lollygagger on Dec 26, 2016 11:28:22 GMT
I've read somewhere words to the effect of "gel batteries don't like being on a charger for extended periods", but never any explanation.
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Post by lollygagger on Dec 26, 2016 11:33:08 GMT
Oh dear. Just checked the meter. I've used 15ah and down to 11.22v. Next up the fridge will stop working.
What to do? Would it be dangerous to switch on the charger?
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Post by lollygagger on Dec 26, 2016 11:38:37 GMT
Which begs the question...
It's a bit daft to sit in a marina running your 12v systems off a constantly charging battery bank?
Wouldn't it be kinder to leave the batteries out of the loop and have a transformer?
Or, is that in effect what the charger should be doing?
Has the charger been fooled into providing incorrect voltage to the batteries by the load on the circuit?
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Post by lollygagger on Dec 26, 2016 11:43:20 GMT
20 mins and no replies, you'd think it was Christmas or something.
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Post by JohnV on Dec 26, 2016 11:59:04 GMT
I'm sympathising but I don't have any experience, so I'm not daft enough to comment.
I don't see why gel batteries shouldn't be left permanently connected to chargers that are set up properly though .... after all gel batteries are the standard "standby" battery in many alarm and computer room standby systems.
Sorry I can't help
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Post by lollygagger on Dec 26, 2016 12:10:50 GMT
The fridge has conked out now.
I wonder if the warm battery, I couldn't reach the other to check, is faulty and maybe, just maybe there's life in the other. Probably not.
With the charger on, but not charging properly due to going into float too soon, would that slowly deplete the batteries so I wouldn't notice? It's been a month or two since I last switched it off and let the batteries drain deliberately.
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Post by Gone on Dec 26, 2016 12:19:46 GMT
If you have 2 batteries in parallel and one now has an internal fault, then isolate that one and use the charger on the good one. Make sure that the charger is set to Gel batteries as if set to normal type the float voltage may be too high. That way you will get your fridge going again.
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Post by lollygagger on Dec 26, 2016 12:54:49 GMT
First things first, I need so safely disconnect. Any advice? The other battery is under this one down a hole.
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Post by lollygagger on Dec 26, 2016 13:00:32 GMT
Just checked the spec, 70kg per battery. Down a hole.
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Post by lollygagger on Dec 26, 2016 13:02:56 GMT
Plan is to switch off at the isolator then remove the link between -ve and the shunt. Don't be shy, shout out if I'm doing something daft.
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Post by tonyb on Dec 26, 2016 13:09:51 GMT
If you do that you will isolate both batteries. Assuming the one underneath is OK then disconnect the shunt ink from the top battery PLUS the black lead running down beside that battery and join the two cable terminals with a chunky boat. Then wrap the joint in some form of insulation.
Alternative is take the whole negative clamp off the top battery and stock it in several plastic bags to insulate it.
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Post by Gone on Dec 26, 2016 13:15:52 GMT
From the limited detail in the picture I would suggest that to disconnect - 1) The top battery. Disconnect both black wires from the negative post, then bolt the two wires together and tape up ensuring it goes nowhere near the positive terminal. This will remove the top battery from the circuit and leave the bottom battery connected.
2) The bottom battery. - Simply disconnect the black wire from the bottom battery from the top battery negative post. Tape up and keep it away from the boat hull and the other battery connections. This leave the top battery connected into the boat circuits.
If you are not sure, find someone to help you as these are big batteries that can do a lot of harm if shorted out etc. By taping up I mean that the exposed metal ring terminals are insulated and the wires fixed so they don't move around. But again, if not sure, please seek advice before touching. If you short out one of those batteries it has enough power to melt a spanner causing sever burns or even eye damage.
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Post by lollygagger on Dec 26, 2016 13:18:05 GMT
If you do that you will isolate both batteries. Assuming the one underneath is OK then disconnect the shunt ink from the top battery PLUS the black lead running down beside that battery and join the two cable terminals with a chunky boat. Then wrap the joint in some form of insulation. Alternative is take the whole negative clamp off the top battery and stock it in several plastic bags to insulate it. Phew, glad you're about Tony. I don't know if both or one battery has had it, it's just a theory. As luck would have it my multimeter battery just ran out after 5+ years so I'm wondering how I can check anything other than try charging/using the batteries one at a time and see what happens.
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Post by lollygagger on Dec 26, 2016 13:22:43 GMT
Now I've read both your replies it'sunk in! I was imagining having to drag the top battery out.
I would like to try the bottom one first as I know the top one was getting warm.
Your advice is much appreciated gents, I'm glad I asked.
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