270ah DIY LiFePO4 build

[vas]

Vic,
I understand you are on 12V bank, 750W sound a lot!
I'm on 24V and 600W, and I'm facing the issue of not getting 600W out of them. When it's end of July and August ambient is too high that I'm loosing up to 20% it seems, whereas now in Sept sun is much lower and I'm loosing as my panels are almost flat on the f/b hardtop.
So Q is, how much of your 750W do you see reported (as peak power midday!) by battery monitor in different months during the summer?

cheers

V.

 

[Poey50]

We haven't regretted buying a Balmar alternator, external regulator (MC614) and serpentine belt upgrade. It doubled the overall cost but I can add 70-90 ah to the battery in the hour it takes to get out of the harbour. I have an off switch on the regulator as most of the time I don't use it but after several dull days it is very handy.

 

[vas]

otoh, I've regretted spending a hundred quid on an sterling advanced alternator regulator... Unless you motor daily (I tend to spend 3-4days on each spot before moving...) solar has to be the main source of power in the Med. But it seems that even that needs careful planning. I could add two 1000X500mm (approx) 100-120W each flex panels on the coachroof, may have to consider it for next summer instead of LifePO4 conversion

 

[Kelpie]

otoh, I've regretted spending a hundred quid on an sterling advanced alternator regulator... Unless you motor daily (I tend to spend 3-4days on each spot before moving...) solar has to be the main source of power in the Med. But it seems that even that needs careful planning. I could add two 1000X500mm (approx) 100-120W each flex panels on the coachroof, may have to consider it for next summer instead of LifePO4 conversion

It seems a shame that 240w flexi panels would prevent you from going ahead with LFP. Surely the two projects are not the same magnitude of cost or difficulty?

If solar is limited, that is even more reason to go ahead with LFP. Can you add some rigid panels as well? They're so cheap that they are almost free

 

[vas]

well tbh I still cannot understand how going LifePO4 automagically gets the same solar to charge them whereas same solar wouldn't be enough for FLA... There's either a flaw in that argument or I'm missing something big ?
no reasonable place to fit more rigid solar on my mobo, first step would be replace the 300W ones with hopefully 360W identical size so they fit in the hardtop. Second step is flex ones in series and an extra victron mppt.
Third step is LifePO4.

I may do #1 and #3 this winter especially if we end up WFH again!
we shall see. Decent progress on my VictronOS running raspberry so got an awful lot of data to analyse and think upon during winter. I'll report once I figure out what my demands really are.

edit: just checked and found locally exact same size panels 992X1956 @370W each for 200euro a piece. Now have to re-read the difs between polycrystaline and monocrystaline panels (mine are poly, the 370W ones are mono I think there was a catch) So seems that this is step one during the winter. Probably leaves me with enough change to get 8X280Ah LifePO4 cells

V.

 

[Poey50]

well tbh I still cannot understand how going LifePO4 automagically gets the same solar to charge them whereas same solar wouldn't be enough for FLA... There's either a flaw in that argument or I'm missing something big ?

I think Kelpie is referring to the low internal resistance of LFP compared to lead acid especially when the latter is above 80% SOC. It makes LFP noticeably better at harvesting solar.

 

[vas]

I understand that, but atm my problem is doing the initial 75% (early in the morning) to 85% before noon. And there, the problem is that I dont have the solar output to do it. Yes, once I'm over 90% and it's 15:00 LifePO4 may be slightly better, but then sun drops again and I'm loosing W again.

 

[Kelpie]

I understand that, but atm my problem is doing the initial 75% (early in the morning) to 85% before noon. And there, the problem is that I dont have the solar output to do it. Yes, once I'm over 90% and it's 15:00 LifePO4 may be slightly better, but then sun drops again and I'm loosing W again.

It's that last 10% where you really see the benefit. And with LFP it doesn't actually matter whether you get to 100% anyway (although it's good to get them fairly full every so often do that they can balance).

 

[sailaboutvic]

Vic,
I understand you are on 12V bank, 750W sound a lot!
I'm on 24V and 600W, and I'm facing the issue of not getting 600W out of them. When it's end of July and August ambient is too high that I'm loosing up to 20% it seems, whereas now in Sept sun is much lower and I'm loosing as my panels are almost flat on the f/b hardtop.
So Q is, how much of your 750W do you see reported (as peak power midday!) by battery monitor in different months during the summer?

cheers

V.

If you ask me a few months ago I could had given you an answer but to be honsty I never bothered taken much notice , I probably did when they where new but the urge to keep looking at them have long gone ,
but to day it's over cast again and as I looked just now it's pushing 35A ,
While 6.3A are coming out.
so no way are the batteries going to reach full (98%) ,
As we got no plain to move our anchor .

The best part about the lithium is even tho they low by now with my old LA I be almost empty where I still got 150ah at less if I wanted to push them , plus we using much my Amps now then we used with LA

 

[sailaboutvic]

Vic,
I understand you are on 12V bank, 750W sound a lot!
I'm on 24V and 600W, and I'm facing the issue of not getting 600W out of them. When it's end of July and August ambient is too high that I'm loosing up to 20% it seems, whereas now in Sept sun is much lower and I'm loosing as my panels are almost flat on the f/b hardtop.
So Q is, how much of your 750W do you see reported (as peak power midday!) by battery monitor in different months during the summer?

cheers

V.
[/QUOTE]

It's now 15.50 and the input dropped to 19A

 

[vas]

It's that last 10% where you really see the benefit. And with LFP it doesn't actually matter whether you get to 100% anyway (although it's good to get them fairly full every so often do that they can balance).

well,
I'm at anchor now for 10days, unless I get the geny pumping 60A@24V for half an hour in the morning I have no chance of reaching 90% in the evening from the 75% I start when the sun comes up. I doubt that's going to improve by just moving to LifePO4.
The biggest argument for me for LifePO4 is the flat curve so that I'm not on the verge of the Multiplus kicking me out in the morning when the two fridges happen to be on and the fresh water pump kicks in (15A+) Hate it when I see 23.8-24.2V as I know it's v.easy to go under.

 

[vas]

If you ask me a few months ago I could had given you an answer but to be honsty I never bothered taken much notice , I probably did when they where new but the urge to keep looking at them have long gone ,
but to day it's over cast again and as I looked just now it's pushing 35A ,
While 6.3A are coming out.
so no way are the batteries going to reach full (98%) ,
As we got no plain to move our anchor .

The best part about the lithium is even tho they low by now with my old LA I be almost empty where I still got 150ah at less if I wanted to push them , plus we using much my Amps now then we used with LA

thanks Vic,

I guess they are monocrystaline ones (black)?
the 35A would be 17.5A @24V or in LifePO4 money 27+V which is much more than I've ever seen over the last 5yrs I'm running them!

V.

 

[gregcope]

@sailaboutvic interesting data. Thank you.

 

[sailaboutvic]

@vas see the snap shot, one is of 16.30 we still getting over 9.5 A but only 2.3A are being put back in .
Next one show 17.50 1hour 20 mins later and as you can see although we still getting Amps there not enough to replace what's coming out .
Rought estermate to day we used 120A over the day light hours ( fridge, freezer, kettle,charging some stuff and the microwave when on for about 4/5mins
We started at 50% soc and ended 77%soc on a 400AH bank , I sure you be better then me to do the maths.
Weather today, out break of sun but it was mostly over cast .
I was hoping we be make 85%soc but it didn't quite make it .

We just going into our first winter as you know with the lithium and the 750Wsolar so it all still new but if I take the last six days we had,
I reckon if we don't want to start the gen and only charge with solar we could do with another 300W ,
Especially as the winter months come along.
From April to now we had plenty of solar.

With more over cast days to come , to use the induction hob or heat up the heat water it would mean turn on the Gen or we just be depleting the batteries more,

On the other side , we could cook to night and heat up water on the batteries but they be back to 30%soc and with more overcast day to come it's going to take same to get them back up to 98% unless we get one or two days of full sun or motor or start the Gen .

We have managed six days now at anchor only charge as been the panels which no way could we have done that on LA and we was using less power but then we only had 400w solar .
but we have managed our consumption and not heated up water and used the gas for cooking over some of the last few days .

What I posted isn't Internet figures it's what we got ,
It's all find to do calculations how much you use and how much you need but in the real world it don't work that way , if you want to stay on your hook for weeks , a few days of shirty weather will knock the calculations for a Burton.

 

[sailaboutvic]

thanks Vic,

I guess they are monocrystaline ones (black)?
the 35A would be 17.5A @24V or in LifePO4 money 27+V which is much more than I've ever seen over the last 5yrs I'm running them!

V.

Yes black monocrystaline but there not some super dropper panel , brought from Gremany but I bet there from China

 

[sailaboutvic]

@vas
Continue from yesterday posting Vas we around 180A down till 0730 when we had first little bit of power from the solar ,

We need to pump in 280A min if we take into account what we use to day to get the batteries back to 95/98%
That's not going to happen this time of year on just solar of 750W especially with overcast days,
Althought we probably get them back up to where they finish last night possibly a bit high depending on how much sun we get .or not get as it's forecaster of being overcast again.

We may move to day which mean we be charging through our B2B but it only be around 25A and as we won't be motoring for long that's not going to help much.

In my eyes this is where lithium come into their own .
With my LA 400Ah bank now I be out of juice @52% SOC I couldn't use Anything without charging them let alone the AC ,
With Lithium drawing 146A ( see photo ) the batteries only drop to 12.9v then shot back up to 13.1v once I stop drawing 146A
Add to that I still have a good 180Ah before I need to put any charge into them .

 

[sailaboutvic]

Just another update .
It's now 16.30 and we had a pretty good day after all,
we manage to put in over 200A plus what we used during that time .
We gone from 50% to fully charge 98%
The MPPT are on Float 13.5v so only what coming out is being replace

 

[Poey50]

Just another update .
It's now 16.30 and we had a pretty good day after all,
we manage to put in over 200A plus what we used during that time .
We gone from 50% to fully charge 98%
The MPPT are on Float 13.5v so only what coming out is being replace

A slight tangent Vic but do you have a screen shot of your cell voltages when fully charged? I'm interested to see how well your 123Smart is doing at keeping balance. Mine got well out of balance last year as I wasn't using the boat much and had only about 60% charge for most of the year. I'm not sure if it was the BMS or the cheaper cells that I use which may not be so well matched for internal resistance.

 

[noelex]

So Q is, how much of your 750W do you see reported (as peak p

As another data point that may be helpful:

We have 1005w of solar. I suspect we are a little further from the equator than most at over 51°N. Today was a mixture of blue sky and heavy rain, so was reasonably representative, although perhaps a little better than average.

Our peak production today was 825w. Total production so far was 2.9 kw hours. This included around two hours of regulation, and the solar day is not yet over. Without these factors I would estimate total potential production would be a little over 3.5 kw hours.

At 4pm we were regulating, but turning on a high load, during a sunny patch produced 440w.

I hope these numbers are of some help, although overall the best way to test if your solar system is producing what it should be is to look at the peak production at the best part of the year. If you are in an area of reasonable solar insolation you should see a peak production around the rated output of the panels. These peaks will only be brief, but show the system is working well. Even slightly above the rated output is possible.

The most I have seen from our 1005w is 1182w.

 

[sailaboutvic]

A slight tangent Vic but do you have a screen shot of your cell voltages when fully charged? I'm interested to see how well your 123Smart is doing at keeping balance. Mine got well out of balance last year as I wasn't using the boat much and had only about 60% charge for most of the year. I'm not sure if it was the BMS or the cheaper cells that I use which may not be so well matched for internal resistance.

I have to look back as I use to keep them but if I haven't give me few days when I have some time and I will print one for you, got to catch it just right or I miss it.
What I can remember is set at 13.8V there nothing in it between the cells even up to 14.1V BUT AT 14.2V cell 1 or4 would run off so there be something like 0,06 /0.08 different.