Ryannn
Posted a lot
Posts: 2,421
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Dec 21, 2014 13:33:55 GMT
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Hiya, hoping someone can help me with an issue on my shogun.
Car has twin 12V batteries as it is an import and has a cold start pack. I went out earlier this week and the car was dead, just clicking when I turned the key.
Re-charged the batteries for a day and the car drove fine for a day, Left it parked overnight and went to it this afternoon to go to work and again it is completely flat! Won't even light the dash up now.
When the car is running there is about 16V at the battery and although the alternator is second hand, it's only been fitted a few months.
The batteries are of unknown age, are they likely to be the cause?
Thanksss
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Dec 21, 2014 13:48:55 GMT
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16v is too much, way too much - your alternator is overcharging the batteries and boiling them dry. Is there a sulphurous smell around them?
14.8v is really as high as you ever want to see on the battery terminals.
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squonk
Part of things
Posts: 858
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Dec 21, 2014 14:16:33 GMT
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Is the 16v a measured value using a multimeter or a guesstimate using a dashboard voltmeter? If it is the latter I wouldn't give it much credence.
If one of the batteries has died it will drag down the other when not charging. I had exactly the same problem with my HiLux Surf which also uses a twin battery system. You will probably find that if both batteries are fully charged using a proper battery charger, with them disconnected one will be at a lower voltage than the other (measure with a DVM) - this will be the dead one.
The batteries should be replaced as pairs - an imbalance in capacity will create similar problems unless the car is used very regularly.
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Last Edit: Dec 21, 2014 14:19:05 GMT by squonk
2004 Chevrolet Avalanche Z71
2005 Mercedes CLK320 Cabriolet
1996 Mercedes C180 Elegance Auto Saloon
1996 Rover 620Ti (Dead fuel pump)
1992 Toyota HiLux Surf
1987 Range Rover Vogue (Rusty)
1992 Range Rover Vogue SE (More Rusty)
2006 Chrysler Grand Voyager
2008 Corsa 1.4 Design
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Ryannn
Posted a lot
Posts: 2,421
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Dec 21, 2014 15:14:04 GMT
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It's measured using a multimeter, I will re measure it again tomorrow before I commit to any batteries though.
So if I charge both batteries, and one is below 12V, that is the dead one?
Thanks
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Dec 21, 2014 16:07:05 GMT
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12.8v is fully charged, 12.2v is pretty damned flat If one's below 12v, then it's a large paperweight  |
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You're like a crazy backyard genius! |
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Dec 21, 2014 16:23:46 GMT
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One bad battery won't be causing your alternator to overcharge them both to 16V, so you absolutely definitely have a charging problem unrelated to the batteries.
16v on the batteries for any appreciable amount of time will undoubtedly have done some damage. If they are serviceable, check the level of electrolyte in them both and top up with distilled water.
Charge both batteries with a workshop charger until it says they are full, then put a fixed load like a headlamp bulb on there for ten minutes. Leave the battery to rest for a minute then read the voltage. 12.2 or less is bad, any more is varying levels of OK up to 12.+7 where you have a reasonably good battery.
Having two batteries in parallel, one of which being tired out won't usually drain the good battery, you simply lose the extra capacity of the second battery.
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Dec 21, 2014 17:00:47 GMT
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Check each battery when cranking, they will do below 12v but if you see below 10v that's a dead battery. The regulator on the alternator has gone too if it's letting 16v out.
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squonk
Part of things
Posts: 858
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Dec 21, 2014 17:11:40 GMT
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Having two batteries in parallel, one of which being tired out won't usually drain the good battery, you simply lose the extra capacity of the second battery. Without wishing to start an argument, on the two occasions in the last ten years that I have had batteries die on my HiLux the dead one has dragged down the good one, possibly something to do with altered plate resistance? Its currently running on one battery as the other is dead and drags down the good one over the course of a couple of days. With the dead one disconnected the good one remains charged. Also had the same happen on a wheeled loading shovel with a twin battery 12v system when dissimilar batteries were fitted. |
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2004 Chevrolet Avalanche Z71
2005 Mercedes CLK320 Cabriolet
1996 Mercedes C180 Elegance Auto Saloon
1996 Rover 620Ti (Dead fuel pump)
1992 Toyota HiLux Surf
1987 Range Rover Vogue (Rusty)
1992 Range Rover Vogue SE (More Rusty)
2006 Chrysler Grand Voyager
2008 Corsa 1.4 Design
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Dec 21, 2014 22:36:26 GMT
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No worries man!
I fart about with lead batteries a lot in my line of work. Parallel connection causes no issues unless one of the batteries is in a very bad way. Series is where you have problems generally, especially if they are charged in series, even a slight imbalance will quickly kill the worse of the two batteries.
In parallel, if one of them ends up with one (or more) bad cells rather than just general overall deterioration, 12.6v or so settled voltage on the good battery will be enough to pump a bit of charge into the remaining good cells of the bad battery, and waste most of the energy in the bad cell or boiling the rest away depending on how it has failed.
Like I say, It totally can happen, but it's not really the normal way a battery will fail, unless it is abused. I suppose in this case, where they are heavily overcharged it's a possibility, but the overcharge definitely needs to be looked into before any new batteries are introduced!
For context and an uninteresting story I've got a shed full of old scrap , more or less untested (other than looking for explosions or bulges) batteries all blindly paralleled up as my workshop power supply and have done for yonks. I can leave it for weeks without seeing the voltage drop appreciably between charges. Occasionally I will disconnect them and drop test a few and bin the absolute worst if I'm doing a scrap run, so there has probably been a dozen in turnover or more, but nothing has ever drained the rest of them.
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Dec 22, 2014 11:51:32 GMT
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Have you checked the electrotyle level in the batteries?
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Ryannn
Posted a lot
Posts: 2,421
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Dec 22, 2014 19:09:37 GMT
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They're both sealed batteries so I have no way of getting into them.
I called the AA out today as I was sick of messing with it. The guy said there is a draw of 5amps on the battery when the car is off and we checked but couldn't find anything turned on.
When running, the alternator isn't charging at idle, only at 2500 revs. So he thinks the alternator is shot and it is also drawing power back out.
Does that sound logical?
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squonk
Part of things
Posts: 858
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Dec 22, 2014 19:49:33 GMT
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It's possible that one of the diodes is shot in the alternator. Try disconnecting the alternator and see if the current draw is still there.
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2004 Chevrolet Avalanche Z71
2005 Mercedes CLK320 Cabriolet
1996 Mercedes C180 Elegance Auto Saloon
1996 Rover 620Ti (Dead fuel pump)
1992 Toyota HiLux Surf
1987 Range Rover Vogue (Rusty)
1992 Range Rover Vogue SE (More Rusty)
2006 Chrysler Grand Voyager
2008 Corsa 1.4 Design
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Dec 22, 2014 21:28:24 GMT
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As above could be a fault in the alternator. Try disconnecting it and isolating the terminals, then re-do the current draw test the AA did.
If that is ok, one by one pull each fuse in turn and measure the current drain across each, then you can at least narrow down where the juice is going. That said at 5amps it's significant and should be easy to find, if nothing else by the heat, it's 60watts of energy,
Brian
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Ryannn
Posted a lot
Posts: 2,421
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Dec 22, 2014 21:33:24 GMT
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As above could be a fault in the alternator. Try disconnecting it and isolating the terminals, then re-do the current draw test the AA did. If that is ok, one by one pull each fuse in turn and measure the current drain across each, then you can at least narrow down where the juice is going. That said at 5amps it's significant and should be easy to find, if nothing else by the heat, it's 60watts of energy, Brian AA man pulled each fuse in turn and none dropped the draw. How can I test for a draw without one of those fancy testers? Should I disconnect an earth lead and put my multi meter in place? Thanks again! |
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Dec 22, 2014 21:45:23 GMT
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Does you meter have a 10A setting?
If so you can use that, but you MUST use it in series, that is to say you disconnect a main battery cable and run the power from the battery in one meter lead, through the meter and out the other lead back to the vechicle cable.
If you did this with the alternator connected, then disconnect it (isolate any cable ends, put in a plastic bottle and wrap with insulation tape) and repeat the test, you could find this is the culprit.
Brian
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Ryannn
Posted a lot
Posts: 2,421
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Dec 22, 2014 21:47:01 GMT
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Thanks Brian, that's what I was hoping!
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Dec 27, 2014 19:54:22 GMT
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It's simple and basic but worth throwing in... Have you checked the alternator is earthing properly? If it isn't, it will cause these symptoms. I had this same problem with my Bedford. Replaced the alternator with a brand new one, bought a new battery, problem persisted. Eventually discovered the earth cable had come away from its anchor point, but out of sight and buried inside a previous owners electrical tape bodge. Reconnected it and never had a problem again
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