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Post by Firefox on Jun 24, 2015 15:56:55 GMT
Most of you will know this, but if you want them in handy chart form, here they are. 12.8 to 12.9v is usually fully charged and around 12v 50% charged, below which you should not drop much, to avoid permanent battery damage.
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Post by stonedaddy on Jun 25, 2015 21:46:25 GMT
What a coincidence, I was just looking at a chart from the motor caravan site that had exactly the same chart from there technical department. .... Tom ....
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Post by Firefox on Jun 25, 2015 22:41:47 GMT
I think I nicked it off Facebook, but if I see anything interesting there, I generally copy here because it gets lost over there in a couple of days, whereas here, it's relatively easy to find again.
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Post by Deleted on Jun 26, 2015 16:11:57 GMT
Are these levels that the battery is at without any load on?
For example, my voltmeter (it shows a 0.1v drop from true battery level) shows 12.5v
I switch on lights and battery level drops to 12.3
I switch on tv / radio / media player and battery level drops to 12.1
I plug my mobile in to recharge and battery drops to 12.0
When I switch off lights, the battery level goes back up to 12.2
I can then watch tv and recharge mobile for a good few hours without the level dropping more than 0.1 or 0.2v.
This time of year it's a treat to have a full battery for about 20 hours each day which means I rarely drop below 12.0v even with gadgets being powered for hours on end, but in the winter, I can regularly drop to 11.9 or 11.8 by bedtime, although this does bounce back up a little when gadgets are switched off.
So presumably, based on above, my battery should be healthy as there is only about 1 month in the year when it regularly drops to 11.9v and that's only overnight until some solar charge brings it back up.
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Post by Firefox on Jul 2, 2015 12:00:12 GMT
Yes these are levels without loads. Attach anything to the battery and it will cause further voltage drops.
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Post by Deleted on Jul 3, 2015 10:55:09 GMT
So what's the lowest voltage you can let it drop to under load without doing harm?
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Post by Firefox on Jul 3, 2015 11:25:47 GMT
Depends on the amount of the load.
But say about 11.9v without load and 11.6v with a load of 2 or 3 amps (20w to 40w approx) as a rule of thumb. Most small loads seem to cause a drop of 0.2 to 0.3v.
Any discharge damages your battery - batteries love to be buzzing and fully charged like people - they all fail in the end, but its a question of depth of discharge and number of times it happens. There isn't really a threshold below which the battery is damaged and above that it's fine. So let it drop to 11v the odd time and it's not a big deal, but keep on doing it as a matter of course, and the life will be reduced significantly.
Conversely, keep it above 12v all the time and it will still eventually fail, but hopefully you'll get a good 4-5 years of use or more out of it.
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Post by billypants on Oct 19, 2015 23:10:17 GMT
And if you do let it drop below 12 volts recharge it fully using a multi stage charger. If you leave it overnight even at 50% discharge you are damaging it. Trojans claim they can discharge right down to 20% as long as you recharge right away. And amp for amp their prices are very close to bog standard lead acids now.
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Post by Firefox on Oct 20, 2015 1:14:59 GMT
Trojans are built for things like golf buggies where they get nearly flattened and then back on charge after the round, so I can believe that.
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Post by billypants on Oct 20, 2015 10:38:42 GMT
However throw LiFePo4 into the mix and it becomes interesting. 200 ahrs of LiFePo4 battery is about £960. A lot? Equivalent lead acids might cost about £200 but as you can only use 50% of a lead acid battery you need 2 x 200 ahrs so that's £400.
However a Trojan 220 ahr battery is 52 kilos, a 200 ahr LiFePo4 battery is about 12 kilos. That's a spectacular saving, and generally speaking they only need 1/2 - 3/4 of the recharge time that a lead acid does.
Add to that the fact that LiFePo4 batteries can be discharged about 2000 compared with lead acids 500 cycles, and LiFePo4's can be discharged down to 0% with no ill effects at all and you begin to see the attraction. They might be double the initial cost but there are massive savings in other ways over the medium and long term.
I simply don't have the money to be getting LiFePo4's at the moment but when they drop in price I'll be there like a shot.
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