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Post by Deleted on Oct 24, 2020 21:24:15 GMT
INTRO added to this thread on Sun 25th: Don't waste your time reading this!
I'm afraid asked a silly battery question yesterday, based on incorrect information, and it turned out that I have more leeway than I thought, and I need to try a couple of things out before considering replacing my batteries.
If you love a bit of pointless waffle, here is the original post text:
I'm pretty sure my batteries are past their best, and I'm wondering if maybe the time has come to look at getting replacements.
On some days I can cruise for 6 hours at (typically at about 1200-1500rpm most of the time), and in the evening after that cruise, I will turn the fridge down to a low setting at say 6pm, and then turn it off at about 10pm. Also I now use only rechargeable LED lights in the evenings. So the only significant drain on the batteries during the evenings is the fridge and the Eberspacher, which at the moment is on for about 30 mins at a time, on say 3 or 4 occasions per evening. I dont know what it draws, but I dont think 90-120 mins of it running should bring the batteries down from 12.7v to 12.5v. But thats what is happening- unless I run the engine again for an hour in the evening.
Even if I do that, the batteries can be down to 12.5 anyway by bedtime, with almost nothing draining them.
There is a scribbled summary in the boat's documentation which states that 12.7v is effectively full, and 12.4v is 50% discharged. Even with the minimal use described above, when I get up next morning the batteries are usually around 12.5 or 12.4, so often I feel I have to run the engine again from 8am to 9am, so that I can turn up the fridge, switch on the CH and get all my LED light recharged (via USB).
I know sod all about batteries, but surely three 100ah Trojans should give me more juice than that, in the course of getting down to a 50% state of charge?
They are over 3 years old, and I suspect that in the winter months the boat wasn't used very often, and even though the 600w of solar would have kept them topped up most days, and the charge controller would have prevented them being damaged by charging, I still think they've lost a lot of their effective capacity.
One chap I spoke to suggested that the 50% discharged point might have shifted downwards over the 3 years of their life, to say 12.2v. if that's the case then maybe they have a bit more life in them. But if I assume the 50% discharged point is at 12.4v, then the batteries dont seem to be giving me the amount of power I would have expected.
So is there a way I can check whether the batteries are past it? And if they are, what batteries would people recommend?
Cheers guys
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Post by Deleted on Oct 24, 2020 21:28:02 GMT
Take cover...
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Post by bodger on Oct 24, 2020 21:32:51 GMT
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Post by Deleted on Oct 24, 2020 21:45:34 GMT
So I can let them go down to 12.2v? Thanks bodger. The previous owner seemed fairly well-informed about these sorts of issues, and it is odd that he should write down these values incorrectly, but it looks like he has. I'll try using 12.2 as the 50% discharge point, and see how things go.
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Post by Deleted on Oct 24, 2020 21:53:25 GMT
I think this was previously mentioned the last time you asked this question, but tellymachus advised another Trojan owner to discharge then to 30% then charge them all the way which reportedly had a positive effect. Also you could try the desulphation cycle function.
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Post by Deleted on Oct 24, 2020 22:06:19 GMT
I think this was previously mentioned the last time you asked this question, but tellymachus advised another Trojan owner to discharge then to 30% then charge them all the way which reportedly had a positive effect. Also you could try the desulphation cycle function. I'm afraid I trusted the written version from the previous owner as to the correct 50% charge value, thinking that perhaps he had been given some specific knowledge of these particular batteries from the people who installed them. I did try discharging down to 12.1 on one occasion, but obviously that was not low enough to get to 30%. I've still to try the desulphation cycle. I think rather than waste more people's time on reading a basic question, I'll amend the thread title.
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Post by Telemachus on Oct 24, 2020 22:21:23 GMT
So I can let them go down to 12.2v? Thanks bodger. The previous owner seemed fairly well-informed about these sorts of issues, and it is odd that he should write down these values incorrectly, but it looks like he has. I'll try using 12.2 as the 50% discharge point, and see how things go. 12.2v with no load is roughly 50% SoC. With load, you will get to 12.2v well above 50%. Trojans are semi-traction batteries and “mind” being below 50% SoC much less than cheapo leisure batteries. All that said, with 300Ah you should be getting plenty of capacity for your needs. What you haven’t mentioned at all is whether the batteries are being charged adequately. You just say that you have run the engine for 6 hours or whatever, but that is pretty meaningless in terms of whether you have adequately charged the batteries or not. Probably the alternator is working to some extent, but there are plenty of issues that can mean the alternator isn’t working properly or even that it is unsuitable for charging the Trojans. So the questions to be answered are, what is the battery voltage with the engine still running, near the end of the 6 hours, and what is the charging current? Without those two pieces of info it is impossible to know whether the batteries are being charged properly. If the batteries are not being charged properly, even quality batteries like Trojans, that should last 6 years at least, can quickly be knackered. When batteries are being charged, of course the SoC may well be much lower than the voltage might suggest. For example when the charging voltage hits 12.7v, the SoC could well be only 60% or so. And there is an effect called “surface charge” whereby even after the charge is stopped, the voltage is higher than the SoC suggests, perhaps for several hours. It will eventually subside to its “correct” (for the SoC) value. So for example, if you stop charging and 5 mins later the voltage is 12.7v, if you leave the battery disconnected (don’t discharge at all) then 5 hours later it might only be 12.3v because the surface charge has dissipated and the actual SoC was only 60%. So in summary, first you need to be sure that you are charging the batteries properly. If you definitely are, then yes you need new batteries. But if you are not, there is no point in buying expensive new batteries because they won’t last long (like, no more than a few weeks) if they are not charged properly.
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Post by Telemachus on Oct 24, 2020 22:25:43 GMT
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Post by Deleted on Oct 24, 2020 22:37:14 GMT
I think this was previously mentioned the last time you asked this question, but tellymachus advised another Trojan owner to discharge then to 30% then charge them all the way which reportedly had a positive effect. Also you could try the desulphation cycle function. I think rather than waste more people's time on reading a basic question, I'll amend the thread title. Don't worry about it. Only people with time to waste will reply anyhow.
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Post by Clinton Cool on Oct 24, 2020 23:19:22 GMT
There might be other power being used that you're not immediately aware of. Do you have an inverter, is it permanently switched on? Do you have a t.v. and if so, is it on standby all night?
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Post by Deleted on Oct 25, 2020 7:09:44 GMT
There might be other power being used that you're not immediately aware of. Do you have an inverter, is it permanently switched on? Do you have a t.v. and if so, is it on standby all night? Thanks Ricco, yes I leave the inverter on all the time, although the only mains appliance (sometimes) left on is the fridge. I dont have a TV at the moment. The previous owner's advice was that he just left the inverter on at all times, so I stuck to that. I guess my thinking was that if I start the evening with say 100ah of charge, it should be ok to leave the inverter on overnight. I want to leave the fridge on overnight if possible, as I don't think it helps food preservation if you raise and lower the temperature by a big margin twice a day. But with winter fast approaching, and with me about to start cruising less often after I reach Cheshire, I need to get to grips with understanding and managing my electrics better.
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Post by JohnV on Oct 25, 2020 7:18:13 GMT
As usual there's very little Telemachus has overlooked. However you are quoting voltages but is this from your own testmeter or from something installed in the boat and if so are you sure of it's accuracy ?
only mention it because on my little narrow cruiser there is fixed el cheapo digital voltage meter reading to 1 decimal point that has an error of just under 0.1V .............. enough to skew the readings ........... I know this and allow for it so have never bothered to correct.
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Post by naughtyfox on Oct 25, 2020 7:33:57 GMT
There might be other power being used that you're not immediately aware of. Do you have an inverter, is it permanently switched on? Do you have a t.v. and if so, is it on standby all night? I want to leave the fridge on overnight if possible, as I don't think it helps food preservation Everything I read about batteries problems is the darned fridge. Get rid of the stupid thing. Just roll it off the back of the boat! I don't understand how boaters can't manage without a fridge. Fresh meat, fruit & veg from the shops, UHT milk. How about a water-tight box that resides at the bottom of your water tank that can be pulled up easily? It's bloody cold down there at the bottom (I know, having stood on the base plate at the bottom of ours).
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Post by Deleted on Oct 25, 2020 7:35:35 GMT
So I can let them go down to 12.2v? Thanks bodger. The previous owner seemed fairly well-informed about these sorts of issues, and it is odd that he should write down these values incorrectly, but it looks like he has. I'll try using 12.2 as the 50% discharge point, and see how things go. 12.2v with no load is roughly 50% SoC. With load, you will get to 12.2v well above 50%. Trojans are semi-traction batteries and “mind” being below 50% SoC much less than cheapo leisure batteries. All that said, with 300Ah you should be getting plenty of capacity for your needs. What you haven’t mentioned at all is whether the batteries are being charged adequately. You just say that you have run the engine for 6 hours or whatever, but that is pretty meaningless in terms of whether you have adequately charged the batteries or not. Probably the alternator is working to some extent, but there are plenty of issues that can mean the alternator isn’t working properly or even that it is unsuitable for charging the Trojans. So the questions to be answered are, what is the battery voltage with the engine still running, near the end of the 6 hours, and what is the charging current? Without those two pieces of info it is impossible to know whether the batteries are being charged properly. If the batteries are not being charged properly, even quality batteries like Trojans, that should last 6 years at least, can quickly be knackered. When batteries are being charged, of course the SoC may well be much lower than the voltage might suggest. For example when the charging voltage hits 12.7v, the SoC could well be only 60% or so. And there is an effect called “surface charge” whereby even after the charge is stopped, the voltage is higher than the SoC suggests, perhaps for several hours. It will eventually subside to its “correct” (for the SoC) value. So for example, if you stop charging and 5 mins later the voltage is 12.7v, if you leave the battery disconnected (don’t discharge at all) then 5 hours later it might only be 12.3v because the surface charge has dissipated and the actual SoC was only 60%. So in summary, first you need to be sure that you are charging the batteries properly. If you definitely are, then yes you need new batteries. But if you are not, there is no point in buying expensive new batteries because they won’t last long (like, no more than a few weeks) if they are not charged properly. Thanks Telemachus- yes I've noticed when running the engine that the voltage can appear to rise to 14.4v. About an hour or so after the engine stops they drop to 12.7 or 12.8v, which I assumed was their normal/'true' SoC. But for all I know they might be continuing to lose surface charge for another few hours. I've never left them alone long enough to see. So if I can leave them unused for a few hours and see how far and fast they drop, that will give me some idea of their state? I had assumed they were dropping voltage too quickly under modest loads, but it might actually be surface charge taking several hours to dissipate. The moment I've been dreading has arrived. I need to take the time to go through the manuals for the charger and associated equipment, and try to actually understand their workings better. Thankfully I will soon have a lot more time for general meddling and fettling.
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Post by quaysider on Oct 25, 2020 7:43:04 GMT
There might be other power being used that you're not immediately aware of. Do you have an inverter, is it permanently switched on? Do you have a t.v. and if so, is it on standby all night? Thanks Ricco, yes I leave the inverter on all the time, although the only mains appliance (sometimes) left on is the fridge. I dont have a TV at the moment. The previous owner's advice was that he just left the inverter on at all times, so I stuck to that. I guess my thinking was that if I start the evening with say 100ah of charge, it should be ok to leave the inverter on overnight. I want to leave the fridge on overnight if possible, as I don't think it helps food preservation if you raise and lower the temperature by a big margin twice a day. But with winter fast approaching, and with me about to start cruising less often after I reach Cheshire, I need to get to grips with understanding and managing my electrics better. HAving switched from a 12v to mains fridge/freezer, which by virtue of my inverter never going into eco mode (the fridge seems to just draw enough to keep it on constant) I think if you actually measure the temp having had it turned off from 10pm to 7am, you'll find there is only 1 degree in it. I've gotten around that now by simply bunging in a couple of ice packs from the freezer to the fridge part before I turn off the inverter overnight. THAT'S assuming it's a reasonably modern insulated fridge/freezzer like mine is I'll grant you.
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