Nick_H
Well-Known Member
Am I right in thinking that if a lead acid battery holds 12.94 volts for 24 hours then there's nothing wrong with it?
lead acid battery
- Thread starter Nick_H
- Start date
SEARANGER ANCASTER
Well-Known Member
I can see how it can be 12.9 ? Max it should be is 12.64 when fully charged
SEARANGER ANCASTER
Well-Known Member
davids0865
Well-Known Member
Varies with temp
BartW
Well-Known Member
I don't think you can make that conclusion just like that,
I'm testing 10 old lead acid boat battery's here right now, (from BA previously replaced all by new)
and they give some weird results,
all were left alone, disconnected for more then a year,
all were flat, mostly less then 12volt,
two had a label "bad" on them, (a year ago tested with my electronic battery tester)
at least one of the previously "bad" battery's after recharging one night,
keeps about 13V on the terminals for several hours,
some of the non labelled ones aswell,
my electronic battery tester instructs to take off the charger (while there isn't any connected)
some other settle at around 12,7 volt, and measure OK with my electronic battery tester
the tester gives a value for the remaining capacity that seems OK.
next testing will be with load resistors on them for several hours,
(next week, have other obligations right now)
we need Anna Geek for advice !
jfm
Well-Known Member
We need annageek but I think the answer is "no", or at least "not necessarily". For example it could make voltage but hold very little quantity of charge (energy) in which case it would show 12-point-something volts but go flat very quickly and therefore be knackered
VicS
Well-Known Member
Probably, but I'd want it to hold a decent charge ( say 12.7 to 12.8 ish) for a lot longer than 24 hours. My newish leisure battery, which I last charged about three weeks ago, reads 12.87 at the moment.
Another, nearly new, very traditional type, car battery last charged a couple of weeks ago reads 12.81
However volts alone is not a test of a battery. It indicates state of charge and by monitoring over a period of time you can confirm that it is holding its charge. It does not however guarantee that the battery will deliver the high currents that it should do.
The old fashioned "drop tester " will do this as will more modern battery testers
gjgm
Well-Known Member
I think it is the other way.. if it can't hold the voltage then there is something wrong with it.
Still, unless this is uber critical, I would settle for the idea there is probably little wrong with it.
You can't ask in absolutes on this forum, Nick !
sailorman
Well-Known Member
That s is for wet unsealed i assume
Nick_H
Well-Known Member
I'm asking out of interest more than anything else, as I've already bought two new batteries to replace them. They're off my sportboat, one is a dedicated starter battery that seemed to be struggling to turn over the big outboard at the end of the season, the other is the domestic battery that was completely flat (measured 1.5 volts!) after standing since October.
To my surprise both have readily accepted a charge and seem to be holding it. The starter battery came off charge yesterday, measured 12.94V a few hours later before I went to bed, and hadn't dropped at all when I measured it again this morning. When I removed it, I noticed the engine start connection was made to the threaded studs, not the tapered lugs, so I'm now wondering if the issue was poor connection to the terminal rather than a shot battery. I should have checked this before I ordered the new one I suppose, but it didn't occur to me that it may be connected incorrectly.
The domestic only came off charge this morning, and after several hours shows 12.8 but I think is still dropping slowly. I wanted a bigger capacity anyway, and batteries are surprisingly cheap, so I think it's off to recycling regardless.
Out of interest, the brand new batteries measure 12.74V.
To my surprise both have readily accepted a charge and seem to be holding it. The starter battery came off charge yesterday, measured 12.94V a few hours later before I went to bed, and hadn't dropped at all when I measured it again this morning. When I removed it, I noticed the engine start connection was made to the threaded studs, not the tapered lugs, so I'm now wondering if the issue was poor connection to the terminal rather than a shot battery. I should have checked this before I ordered the new one I suppose, but it didn't occur to me that it may be connected incorrectly.
The domestic only came off charge this morning, and after several hours shows 12.8 but I think is still dropping slowly. I wanted a bigger capacity anyway, and batteries are surprisingly cheap, so I think it's off to recycling regardless.
Out of interest, the brand new batteries measure 12.74V.
annageek
Well-Known Member
What type of charger was used to recharge them? Are they SLA/AGM or flooded batteries? Roughly speaking, what sort of temperatures was the battery charged / stored in prior to taking it's open circuit voltage. How old is the starter battery.
They may well charge up and appear to hold charge, but my guess would be the domestic will slowly decrease over the next few days and the starter battery will stick up at around 12.9V. The poor performance from the starter battery could well be the result of some mild sulphation robbing you of performance. It could also be good 'ol end of life (capacity has fallen below 80% due to the plates being eaten away / not enough active material where it should be) and the equivalent internal impedance has therefore increased to the point where voltage droop is just too low under cranking current draw.
One test you could do to ascertain if it was just a dodgy connection (if you are so inclined - and I wouldn't blame you if you're not) is to get your old starter battery, attach a multimeter that has a hold function which preserves the lowest voltage measured (many do) and crank the engine. Then try again with the new battery - see if the voltage drops are about the same or different (bigger voltage drop on the older battery). It'd probably be worth beginning with a warm engine though, so the starting demand is roughly equal.
In all honesty, I wouldn't expect much from the domestic battery... Sounds like you've gained a very effective door stop from that one! It's always worth a try though, as for no apparent reasons, so batteries just recover remarkably well.
One thing to note, though, is if you were suffering poor performance from the original starter battery, and it turns out it's a result of sulphation (as opposed to just end of life), then it's probably being slightly undercharged. If you do a lot of start stop in your sports boat (pulling skiiers/boarders/ringos and stopping to pick them up?), it can take its toll if you're not also giving it some long term shore / storage trickle charging too. May be worth having a think about how it's being used so as to ensure you don't prematurely kill your new batteries.
They may well charge up and appear to hold charge, but my guess would be the domestic will slowly decrease over the next few days and the starter battery will stick up at around 12.9V. The poor performance from the starter battery could well be the result of some mild sulphation robbing you of performance. It could also be good 'ol end of life (capacity has fallen below 80% due to the plates being eaten away / not enough active material where it should be) and the equivalent internal impedance has therefore increased to the point where voltage droop is just too low under cranking current draw.
One test you could do to ascertain if it was just a dodgy connection (if you are so inclined - and I wouldn't blame you if you're not) is to get your old starter battery, attach a multimeter that has a hold function which preserves the lowest voltage measured (many do) and crank the engine. Then try again with the new battery - see if the voltage drops are about the same or different (bigger voltage drop on the older battery). It'd probably be worth beginning with a warm engine though, so the starting demand is roughly equal.
In all honesty, I wouldn't expect much from the domestic battery... Sounds like you've gained a very effective door stop from that one! It's always worth a try though, as for no apparent reasons, so batteries just recover remarkably well.
One thing to note, though, is if you were suffering poor performance from the original starter battery, and it turns out it's a result of sulphation (as opposed to just end of life), then it's probably being slightly undercharged. If you do a lot of start stop in your sports boat (pulling skiiers/boarders/ringos and stopping to pick them up?), it can take its toll if you're not also giving it some long term shore / storage trickle charging too. May be worth having a think about how it's being used so as to ensure you don't prematurely kill your new batteries.
Nick_H
Well-Known Member
Thanks Anna
The charger is an old but good quality 10 amp domestic unit (the batteries were disconnected and taken into the house), doesn't have any reference to different stages of charging though. They're flooded batteries, and were charged at room temperature. I don't know how old they are, as they came with a used boat, but they're unlikely to be older than 2010.
Actually, a day on, both batteries have held their voltage OK, but I now understand that this doesn't necessarily mean they're OK. It would be quite a faff to try both on the engine, not least because the boat is on a trailer at the mo' so I'd have to rig up cooling water etc. As I say, I've already replaced them, so my original question was more out of interest as I thought I may have replaced them for no reason.
One question though if you don't mind. The boat sits on a river mooring for 6 months of the year, and I rely on a 10 watt solar panel to keep the batteries topped up. I was told I didn't need a regulator for such a small panel. Do you know if this type of charging is good or bad for the batteries?
The charger is an old but good quality 10 amp domestic unit (the batteries were disconnected and taken into the house), doesn't have any reference to different stages of charging though. They're flooded batteries, and were charged at room temperature. I don't know how old they are, as they came with a used boat, but they're unlikely to be older than 2010.
Actually, a day on, both batteries have held their voltage OK, but I now understand that this doesn't necessarily mean they're OK. It would be quite a faff to try both on the engine, not least because the boat is on a trailer at the mo' so I'd have to rig up cooling water etc. As I say, I've already replaced them, so my original question was more out of interest as I thought I may have replaced them for no reason.
One question though if you don't mind. The boat sits on a river mooring for 6 months of the year, and I rely on a 10 watt solar panel to keep the batteries topped up. I was told I didn't need a regulator for such a small panel. Do you know if this type of charging is good or bad for the batteries?
annageek
Well-Known Member
It sort of depends on the capacity of the battery as to whether you need a charge controller or not. That said, given we're talking about an engine start battery and a domestic battery, you're almost certain not to have any troubles. Basically, as a rule of thumb, you want to aim at C/100 charge rate to be safe. Given a 10W solar panel connected to a 12V Pb battery will be dragged by the battery to about 14V maximum, you're going to get around 700mA of current, therefore as long as you're over 70Ah, you'll be fine.
Also, given that temperatures inside a covered boat (and therefore the batteries) can get pretty hot in the summer sun, self discharge will be really high, and you could probably push the C/100 limit a touch in order to overcome this self discharge.
Put simply, my batteries are 150Ah (combined) of Halfords specials. If I had a 10W PV panel, I'd use it without any worries.
I'm assuming this is the case, but all of this pre-supposes the PV panel is diode blocked (99% likelihood it will be). If not, it needs to be!