|
Post by Telemachus on Apr 5, 2021 18:10:27 GMT
If I had solar and didn’t need the full capacity (summer usage, no cooking by leccy etc), I think I’d set the charge voltage to around 13.3 or 13.4 to keep the SoC mid-range..
|
|
|
Post by kris on Apr 5, 2021 18:25:35 GMT
If I had solar and didn’t need the full capacity (summer usage, no cooking by leccy etc), I think I’d set the charge voltage to around 13.3 or 13.4 to keep the SoC mid-range.. im waiting at the moment for a new usb to serial cable which will hopefully solve the communication problems between my laptop and mppt. at the moment Im on the gel settings which james has said are, okay he's used one of these on gel with these batteries. But yes I would like to optimise the settings and using it as a hv cutoff as has been suggested would be good. ill see what sort of currents these solars generate and if I am wasting a lot of power ill sort out a relay and water heating.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 5, 2021 18:58:23 GMT
The trouble is that over the middle part of the range, which is the optimum range to keep the batteries if you don’t need their full capacity, there is virtually no change in voltage. If you look at that chart I posted you’ll see that the voltage at 70% and 40% are both quoted as 13.2v. Of course there is some voltage change, but it is down to the 100ths of a volt and the accuracy of the measuring device and the exact measuring conditions, become the predominant factors. Better to set the SoC on the BMV at quite a high SoC where the voltage change with SoC becomes significant. From what I can see in the graph, at the lower end there seem to be much bigger changes in voltage as the SoC decreases. e.g. at 30% SoC the voltage is 13.0, and at 20% SoC the voltage is 12.9 So if Kris lets the voltage get down to 12.9 or 13.0v, he can assume the SoC to be 20-30%, which is at least a starting point. My impression is that when cruising, you need to keep half an eye on the batteries (which is fair enough). I've been letting my SoC get up past 90% a few times in the last week (with going cruising and it being sunny), and I'm starting to think I need to tweak things so that happens less often. Ultimately I can switch off the B2B charger if I'm concerned- eg the SoC is up to say 85% and its only halfway through the day. I let it get high today as I'm stopping for the next two days. Starting the static period with a high SoC will mean no engine running tomorrow, and little or none the day after. So on one hand I want to let my batteries run up a high SoC when cruising, so that I dont have to run the engine on the subsequent days when I'm still. But on the other hand I cant let them get up past 90% too often, as that will shorten their lifespan. How often is too often, is what I'm wondering- and also whether to impose a maximum of 85% as a high SoC, that will only be exceeded once per month when synchronising.
|
|
|
Post by Telemachus on Apr 5, 2021 19:05:31 GMT
The trouble is that over the middle part of the range, which is the optimum range to keep the batteries if you don’t need their full capacity, there is virtually no change in voltage. If you look at that chart I posted you’ll see that the voltage at 70% and 40% are both quoted as 13.2v. Of course there is some voltage change, but it is down to the 100ths of a volt and the accuracy of the measuring device and the exact measuring conditions, become the predominant factors. Better to set the SoC on the BMV at quite a high SoC where the voltage change with SoC becomes significant. From what I can see in the graph, at the lower end there seem to be much bigger changes in voltage as the SoC decreases. e.g. at 30% SoC the voltage is 13.0, and at 20% SoC the voltage is 12.9 So if Kris lets the voltage get down to 12.9 or 13.0v, he can assume the SoC to be 20-30%, which is at least a starting point. My impression is that when cruising, you need to keep half an eye on the batteries (which is fair enough). I've been letting my SoC get up past 90% a few times in the last week (with going cruising and it being sunny), and I'm starting to think I need to tweak things so that happens less often. Ultimately I can switch off the B2B charger if I'm concerned- eg the SoC is up to say 85% and its only halfway through the day. I let it get high today as I'm stopping for the next two days. Starting the static period with a high SoC will mean no engine running tomorrow, and little or none the day after. So on one hand I want to let my batteries run up a high SoC when cruising, so that I dont have to run the engine on the subsequent days when I'm still. But on the other hand I cant let them get up past 90% too often, as that will shorten their lifespan. How often is too often, is what I'm wondering- and also whether to impose a maximum of 85% as a high SoC, that will only be exceeded once per month when synchronising. This of course being why I have 80% and 100% (and 50%) charge termination settings on my alternator controller! 80% normally, and flip to 100% for the last hour of the day if we won’t be cruising the next day. Yes one can look for voltage vs SoC at either top or bottom 20% or so, no difference in terms of battery stress.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 5, 2021 19:10:24 GMT
There is one other thing that struck me about managing lithium batteries- it does make it more tricky for me to allow any close friends/relatives to use the boat for a few days.
I'm not being entirely altruistic- my elder brother has just bought a brand new Dethleffs motorhome and he is considering allowing a few of us siblings to use it, so letting him use my boat would go a long way to persuading him to allow me to use his motorhome.
But I'm realising that I'm going to have to stress and stress again to any would-be users that the batteries are all-important, and must be managed carefully. They'll want to cruise in the summer, and the solar will be flooding in all day, as well as the engine charge- and even though I have voltage cutoff set at 14.0v, the SoC will be held at 90-100% for the entire time they are aboard.
So part of the boat tutorial will have to be telling them to connect their phone to the BMV712, and to switch off the B2B when it gets above say 80%.
I think it might be a while before hire boats get lithium batteries...
|
|
|
Post by Telemachus on Apr 5, 2021 19:13:57 GMT
There is one other thing that struck me about managing lithium batteries- it does make it more tricky for me to allow any close friends/relatives to use the boat for a few days. I'm not being entirely altruistic- my elder brother has just bought a brand new Dethleffs motorhome and he is considering allowing a few of us siblings to use it, so letting him use my boat would go a long way to persuading him to allow me to use his motorhome. But I'm realising that I'm going to have to stress and stress again to any would-be users that the batteries are all-important, and must be managed carefully. They'll want to cruise in the summer, and the solar will be flooding in all day, as well as the engine charge- and even though I have voltage cutoff set at 14.0v, the SoC will be held at 90-100% for the entire time they are aboard. So part of the boat tutorial will have to be telling them to connect their phone to the BMV712, and to switch off the B2B when it gets above say 80%. I think it might be a while before hire boats get lithium batteries... I have a similar but more pressing issue, Jeff is not very technical and does visit the boat on his own. Actually he doesn’t often take it out on his own, but my design brief was that it had to be “user friendly” and pretty much transparent/automatic. I am hoping that provided the alternator switches are set to slow charge and 80% SoC, it will completely look after itself. We shall see! (Eventually!).
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Apr 5, 2021 19:40:00 GMT
There is one other thing that struck me about managing lithium batteries- it does make it more tricky for me to allow any close friends/relatives to use the boat for a few days. I'm not being entirely altruistic- my elder brother has just bought a brand new Dethleffs motorhome and he is considering allowing a few of us siblings to use it, so letting him use my boat would go a long way to persuading him to allow me to use his motorhome. But I'm realising that I'm going to have to stress and stress again to any would-be users that the batteries are all-important, and must be managed carefully. They'll want to cruise in the summer, and the solar will be flooding in all day, as well as the engine charge- and even though I have voltage cutoff set at 14.0v, the SoC will be held at 90-100% for the entire time they are aboard. So part of the boat tutorial will have to be telling them to connect their phone to the BMV712, and to switch off the B2B when it gets above say 80%. I think it might be a while before hire boats get lithium batteries... I have a similar but more pressing issue, Jeff is not very technical and does visit the boat on his own. Actually he doesn’t often take it out on his own, but my design brief was that it had to be “user friendly” and pretty much transparent/automatic. I am hoping that provided the alternator switches are set to slow charge and 80% SoC, it will completely look after itself. We shall see! (Eventually!). I want to see what I can do to make mine a bit more self-managing, and limiting the SoC is one thing I would like to do. Sadly the BMV712 only has a low SoC cutoff as you will be well aware, and not a high one. I can remember being given the instructions about a boat I was hiring- how to steer and throttle, where the water tank cap and the hose were, the water pump, the CH, etc- but for some reason the battery voltage numbers didn't sink in at all. It hardly mattered- the batteries were shot anyway, and only good to run a small 12v TV for about 2 hours in the evening, after which everything more or less died. But I'm trying to put myself in that position of a newbie who is being overloaded with info about how to work the boat, and my challenge is to make sure they fully take on board the importance of keeping an eye on the battery SoC, and take simple steps to keep it below 80% or so.
|
|
|
Post by peterboat on Apr 6, 2021 17:56:24 GMT
It started out at 0% SoC so to get it up to 100% (well, 99.6%) surely it has to have been fully charged? They get out of sync so to reset it 14.6 volts until cell balancing finished then it reads a true 100% I did all the batteries like that and I had a lot of them! Prior to that they had all sorts of state of charge on them, if I checked them now they will be miles out as its over 4 years since I top balanced them. But as I say for our light use does it matter? they will outlast my usage I suspect
|
|
|
Post by Telemachus on Apr 6, 2021 19:57:42 GMT
It started out at 0% SoC so to get it up to 100% (well, 99.6%) surely it has to have been fully charged? They get out of sync so to reset it 14.6 volts until cell balancing finished then it reads a true 100% I did all the batteries like that and I had a lot of them! Prior to that they had all sorts of state of charge on them, if I checked them now they will be miles out as its over 4 years since I top balanced them. But as I say for our light use does it matter? they will outlast my usage I suspect
On the forum you linked to is this, so as well as resetting to 100% at 14.6v, if the cell voltages are all 3.4v = 13.6v total, with a low current, that is 100% charged. Which is what I’ve been saying.
|
|
|
Post by peterboat on Apr 6, 2021 20:19:23 GMT
They get out of sync so to reset it 14.6 volts until cell balancing finished then it reads a true 100% I did all the batteries like that and I had a lot of them! Prior to that they had all sorts of state of charge on them, if I checked them now they will be miles out as its over 4 years since I top balanced them. But as I say for our light use does it matter? they will outlast my usage I suspect
On the forum you linked to is this, so as well as resetting to 100% at 14.6v, if the cell voltages are all 3.4v = 13.6v total, with a low current, that is 100% charged. Which is what I’ve been saying. Between 3.4 and 3.8 per cell, but its by the by, less than 14.6 volts it wont trigger the SOC to reset to 100%. When I ran them down to 80% it was at 13.8/9 volts so that does for me for 13.8/9 for bulk 13.7 absorb and 13.6 float and its worked for 4 years so it will do for me John and James who sold us the batteries and has sold hundreds if not thousands with the same advice
|
|
|
Post by Telemachus on Apr 6, 2021 21:11:46 GMT
On the forum you linked to is this, so as well as resetting to 100% at 14.6v, if the cell voltages are all 3.4v = 13.6v total, with a low current, that is 100% charged. Which is what I’ve been saying. Between 3.4 and 3.8 per cell, but its by the by, less than 14.6 volts it wont trigger the SOC to reset to 100%. When I ran them down to 80% it was at 13.8/9 volts so that does for me for 13.8/9 for bulk 13.7 absorb and 13.6 float and its worked for 4 years so it will do for me John and James who sold us the batteries and has sold hundreds if not thousands with the same advice Yes nothing wrong with those voltages, but you think it gives you 80% SoC, I think it gives you close to 100% SoC. Quite happy to agree to disagree.
|
|
|
Post by Telemachus on Apr 26, 2021 18:13:50 GMT
Well day 2 out and about with my precious. Yesterday I charged to nearly 100% - well, one cell hit 3.6v and BMS started beeping, the others were lower so a bit of top balancing needed. BMV and Mastershunt both reset to 100% anyway. We stopped about 4pm, obviously there is the fridge and lighting, plus the sat box and TV (to watch that programme about the flooring company, Lino Duty), gas fan oven for my dins, then electric blanket on number 3 all night (we didn’t bother to light the stove and it was a chilly night) then Mikuni on 7:15 to 9am, the electric kettle for a large pot of tea, Nespresso machine for Jeff, then electric kettle again for Jeff’s porridge-in-a-pot (his jaw/gums still require mush food) and then electric kettle on again because he didn’t like that pot of fancy Waitrose “mixed grain” porridge so had a different one. Laptop, 2 phones and 2 iPads charged, finally set off at about 9:30 with batteries on 75%. I will have to think of a way to use more power!
Tinkered a bit with the alternator controller, everything fine on slow charge (about 85A) but on fast charge the temperature compensation (reducing max output as the alternator gets hot) wasn’t working after the last code edit. But now fixed. And the output reduction at low revs was a bit too sluggish during a sudden drop in rpm (flicking to idle as moored boats approached etc) so that was tweaked. The ramp up to max field current is nice and slow so you hardly notice it. It seems the Iskra can hold about 130A at about 80C which is not bad IMO.
BMS all wired up to Tyco relay and BMV, and I installed a longer battery temperature probe that fits down the gap between 2 cells created by the corrugations in the casing, thus giving me “core” battery temperature. Alternator is currently using the Mastershunt SoC to decide when to go to float but I think I’ll switch it to using the BMV SoC, or really I should have it using both/either / the most recent data, to give redundancy.
All in all, quite happy and no magic smoke escaped. Yet.
|
|
|
Post by kris on Apr 26, 2021 18:18:15 GMT
Yes I’m trying to think up new ways to use power.
|
|
|
Post by peterboat on Apr 27, 2021 8:22:41 GMT
Yes I’m trying to think up new ways to use power. I bought an induction hob this year, two "rings" wasnt expensive £84 one is 1000watts and the other 1800 watts , it lives on top of the Rayburn now I am not using it. Very fast to use and it uses up all that spare solar I have stored, the speed with of temp control is fantastic I recommend them highly and so easy to clean just a quick wipe of the surface looks like new
|
|
|
Post by kris on Apr 27, 2021 8:27:27 GMT
Yes I’m trying to think up new ways to use power. I bought an induction hob this year, two "rings" wasnt expensive £84 one is 1000watts and the other 1800 watts , it lives on top of the Rayburn now I am not using it. Very fast to use and it uses up all that spare solar I have stored, the speed with of temp control is fantastic I recommend them highly and so easy to clean just a quick wipe of the surface looks like new yes an induction hob is on the cards as well as an electric oven and grill.
|
|