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Post by lollygagger on Dec 26, 2016 13:40:22 GMT
Neg leads now joined with a short m8 bolt washer and nut, charger on, fingers crossed.
Up to 78A, the dropped slowly to about 70A. Then I switched the fridge on. Now the amps has climbed to 76 and voltage appears to be slowly dropping. Am I right in thinking it's not looking good?
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Post by lollygagger on Dec 26, 2016 13:46:05 GMT
Now up to 80.2A with fridge cycles OFF. This seems wrong, the amps should be dropping?
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Post by lollygagger on Dec 26, 2016 14:23:58 GMT
The charger thinks it's finished bulk, it thinks it's well into absorption, well over 30 mins, but still up at 80A.
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Post by lollygagger on Dec 26, 2016 14:37:28 GMT
Thinking out loud, if, when I switched on the fridge the volts dropped, could that have caused the charger to switch from bulk to absorption?
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Post by lollygagger on Dec 26, 2016 15:22:24 GMT
Panic over, it's now dropped to 30A and the voltage is at 14.6V.
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Post by Ditchcrawler on Dec 26, 2016 16:12:59 GMT
When you put it all back if it were me I would change the wig nuts to proper nuts so that I could do them up with a spanner. But that's just me.
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Post by lollygagger on Dec 26, 2016 17:08:24 GMT
When you put it all back if it were me I would change the wig nuts to proper nuts so that I could do them up with a spanner. But that's just me. Me too. It does look like the battery I've cut out was duff, the other is behaving I think. Down to 5A now, I've made access to it and it's cool. The charger fan has stopped. I'll switch off in a while and see how fast the voltage drops.
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Post by lollygagger on Dec 26, 2016 17:10:42 GMT
Next up and completely unconnected - where did the inch of water under the engine come from...it's all good fun.
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Post by smileypete on Dec 26, 2016 19:56:56 GMT
What have I done wrong? There was £1k of batteries there. For 2x 200Ah? They do sound overpriced! A set of Trojans should come in at half the cost... Might be good to wind the charger current right down for the remaining battery, hi power mains chargers and iffy batts don't go well together...
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Post by smileypete on Dec 26, 2016 20:22:45 GMT
Also are the batt takeoffs at diagonally opposite corners of the batt pair?
And wing nuts need to be done up tightly with pliers, not easy to safely do with terminals that close.
Poor connection issues may hasten batt demise, a £25 DC clamp ammeter can greatly help diagnosing this sort of thing...
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Post by lollygagger on Dec 26, 2016 20:51:23 GMT
What have I done wrong? There was £1k of batteries there. For 2x 200Ah? They do sound overpriced! A set of Trojans should come in at half the cost... Might be good to wind the charger current right down for the remaining battery, hi power mains chargers and iffy batts don't go well together... Well yes and no, they survived 12 years mostly lived aboard off line charged with a generator. Not too bad? It'll be cheaper replacements for me though.
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Post by lollygagger on Dec 27, 2016 9:51:13 GMT
...and finally...after all night running the fridge on the bottom battery, though that was only 8ah, we're at 13v. I think that proves that one is OK.
Q. With stuff connected as it is, using the top +ve battery terminal but with top -ve disconnected from everything, can I put a STD garage type 8a charger on the top battery?
Another Q. Is there anything I can measure on the "duff" battery that would show it to be duff and so cut down on the experimenting?
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Deleted
Deleted Member
Posts: 0
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Post by Deleted on Dec 27, 2016 11:18:06 GMT
If the top battery has a shorted cell the voltage will be about 10.5-11v even if its just finished charging. don't connect a charger to it as it could go bang........
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Post by Clinton Cool on Dec 27, 2016 11:37:07 GMT
If one battery is shot but the other is OK: have you considered just carrying on with the one battery? you're on shoreline much of the time, 200ah is quite a lot...
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Post by tonyb on Dec 27, 2016 12:07:38 GMT
...and finally...after all night running the fridge on the bottom battery, though that was only 8ah, we're at 13v. I think that proves that one is OK. Q. With stuff connected as it is, using the top +ve battery terminal but with top -ve disconnected from everything, can I put a STD garage type 8a charger on the top battery? Another Q. Is there anything I can measure on the "duff" battery that would show it to be duff and so cut down on the experimenting? Q1 - yes but note what Loddon said, I wouldn't although at 8 amps or less it is less likely than with a larger charger on for weeks on end. Q2 - Probably not with anything you have to hand or ware likely to afford/buy. If it was getting warm/hot and the voltage is down around the 11 volts or less it is reasonable to suspect it has had it. The only way a boater can do it with any sealed batteries is to put them on charge for long enough to ensure they SHOULD be fully charged. Then stand overnight an measure the voltage. If it is below about 12.7 then either you did not fully charge it or it is faulty. If it is around 12.7 note the voltage and leave to stand for about a week. Remeasure the voltage. If it has dropped significantly the battery is even more probably faulty. If it is still around 12.7 then put a known load on it and see how long it can supply the load until the voltage drops to (I think, others please correct) about 11.8 then current draw x time in hours = amp hour capacity. If it is less than about 50% of what is on the label it is time to change the battery. The load should be set to fully flatten the battery over 20 hours for accuracy but any load like a headlamp bulb should give a near enough figure.
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