270ah DIY LiFePO4 build

[geem]

The difference with using a smaller range of charge with LFP is that you always have the choice of using the whole range. Looking forward to hearing about your build.

Agreed but you can also do the same with lead in an emergency.
I know people on here will tell you how cheap lifepo4 is but it isn't really. I am buying cells from the USA. £1000 for eight 280Ah. Class T fuse and holder. £150. Victron b2b £250. Carriage for the cells £150. There will be sundry parts such as new tinned wire, terminals, threaded rod, end plates etc but we are already up to £1550. To replace my Trojans with no other costs would be £750 out here. Cheaper in the UK.
I will be keeping the Trojans until they fail, which might be a long way off. They are four years old this year and still test perfectly on the hydrometer even though they suffer high temperatures.
Edit; forgot to add in BMS at £150 as well.

 

[Poey50]

Agreed but you can also do the same with lead in an emergency.
I know people on here will tell you how cheap lifepo4 is but it isn't really. I am buying cells from the USA. £1000 for eight 280Ah. Class T fuse and holder. £150. Victron b2b £250. Carriage for the cells £150. There will be sundry parts such as new tinned wire, terminals, threaded rod, end plates etc but we are already up to £1550. To replace my Trojans with no other costs would be £750 out here. Cheaper in the UK.
I will be keeping the Trojans until they fail, which might be a long way off. They are four years old this year and still test perfectly on the hydrometer even though they suffer high temperatures.
Edit; forgot to add in BMS at £150 as well.

You wouldn't damage LFP by doing it in the way you would with lead. But I take your point about up-front costs. My system was twice the upfront cost of AGMs. The savings are lifetime costs - when LFP is well-ahead given the great difference in number of lifetime cycles. Assuming, that is, they are properly cared for in a good system.

 

[Poey50]

This is a comparison on various features of my DIY LFP pack compared to a fairly cheap AGM.

 

[geem]

This is a comparison on various features of my DIY LFP pack compared to a fairly cheap AGM.

Interesting. A couple of questions.
How do you define cycles? My lead drop to no lower than 80% charged each night. I only have 450Ah in 12v money. I don't need any more even as liveaboard as we have solar, wind and water charging. This brings the cost of the batteries as well as the weight and size down in your comparison.
I have always though AGM was a poor choice for batteries. They cost more than Trojan wet cell batteries and have a shorter life. They are maintenance free but evidence suggests that they deal with partial state of charge less well than Trojan batteries. Lifeline stipulate that their AMG batteries must be fully charged at least once a week. You also can't equalise most AGM batteries. Lifeline AGM are super expensive. Most comparisons between lead and lifePo4 seem to compare expensive lead batteries with dubious quality lifePO4. If you take something like a high end lead battery system and compare with a Victron lifePO4 installation the costs are eye watering. The BMS alone is over £1000.
People need to make sure they are going the lifePO4 route for the right reasons. It isn't the be all and end all solution some people think it is

 

[Poey50]

Interesting. A couple of questions.
How do you define cycles? My lead drop to no lower than 80% charged each night. I only have 450Ah in 12v money. I don't need any more even as liveaboard as we have solar, wind and water charging. This brings the cost of the batteries as well as the weight and size down in your comparison.
I have always though AGM was a poor choice for batteries. They cost more than Trojan wet cell batteries and have a shorter life. They are maintenance free but evidence suggests that they deal with partial state of charge less well than Trojan batteries. Lifeline stipulate that their AMG batteries must be fully charged at least once a week. You also can't equalise most AGM batteries. Lifeline AGM are super expensive. Most comparisons between lead and lifePo4 seem to compare expensive lead batteries with dubious quality lifePO4. If you take something like a high end lead battery system and compare with a Victron lifePO4 installation the costs are eye watering. The BMS alone is over £1000.
People need to make sure they are going the lifePO4 route for the right reasons. It isn't the be all and end all solution some people think it is

Comparisons are always a bit crude. As you say you can pay megabucks or go DIY for LFP with vast differences in prices and there is a good range of differences across various lead acids. But I think in general the lifetime financial argument is sound with some caveats. (If you keep the boat for a long time, if you need the advantages of LFP, if you can build a seaworthy and safe system, if, if if ...) So I don't think they are a good idea for everyone. Many people thinking of installing LFP do so without a full realisation of what is involved. I'm no LFP fanboy or a paid up member of the Lead-is-Dead Brigade!

 

[geem]

Comparisons are always a bit crude. As you say you can pay megabucks or go DIY for LFP with vast differences in prices and there is a good range of differences across various lead acids. But I think in general the lifetime financial argument is sound with some caveats. (If you keep the boat for a long time, if you need the advantages of LFP, if you can build a seaworthy and safe system, if, if if ...) So I don't think they are a good idea for everyone. Many people thinking of installing LFP do so without a full realisation of what is involved. I'm no LFP fanboy or a paid up member of the Lead-is-Dead Brigade!

I agree entirely and share the same approach. As you know I have an commercial interest in lifepo4 as well. It certainly isn't the natural progression from lead for every user. Lifepo4 will allow some users to change how they do things such as electric cooking but you need a very powerful charging system if you are going to make that kind of lifestyle change or accept the drawbacks of not always having the electrical capacity for a Sunday roast.
I also have some major concerns with drop in replacements with internal BMS. When the BMS fails you have no access to amps stored in your battery without cutting the top off. Even expensive drop in Lifepo4 batteries have had BMS failures. If this happens at sea you may be I serious trouble. One solution may be to oversize the engine start battery bank to act as a back up in such a scenario or maintain a small back up lead domestic bank.

 

[Kelpie]

I know people on here will tell you how cheap lifepo4 is but it isn't really. I am buying cells from the USA. £1000 for eight 280Ah. Class T fuse and holder. £150. Victron b2b £250. Carriage for the cells £150. There will be sundry parts such as new tinned wire, terminals, threaded rod, end plates etc but we are already up to £1550. To replace my Trojans with no other costs would be £750 out here. Cheaper in the UK.
...
Edit; forgot to add in BMS at £150 as well.

How many Trojans can you buy for £750?

When I built my system my costs were:
£690 for 4 T105s (450Ah @12v so 225Ah if cycling between 50-100%)

Or
£407 for 4 271Ah LFP cells and BMS, delivered to my door in the UK. Usable capacity 217Ah although I have gone below the magic 20% a few times with no apparent ill effects.
Yes I had some extra costs but nothing that added up to the nearly £300 cost difference. E.g. threaded rod is pennies and the end plates came from an old road sign I fished out of a ditch.
I baulked at the cost of a class T fuse holder so I'm just going to use a pair of BlueSea powerposts. The fuse itself was €50.
I don't charge from the alternator which I know is a minority position, but nearly two years in and I've barely felt the need. I'm adding a secondhand B2B but I wouldn't consider it essential by any means.

 

[geem]

How many Trojans can you buy for £750?

When I built my system my costs were:
£690 for 4 T105s (450Ah @12v so 225Ah if cycling between 50-100%)

Or
£407 for 4 271Ah LFP cells and BMS, delivered to my door in the UK. Usable capacity 217Ah although I have gone below the magic 20% a few times with no apparent ill effects.
Yes I had some extra costs but nothing that added up to the nearly £300 cost difference. E.g. threaded rod is pennies and the end plates came from an old road sign I fished out of a ditch.
I baulked at the cost of a class T fuse holder so I'm just going to use a pair of BlueSea powerposts. The fuse itself was €50.
I don't charge from the alternator which I know is a minority position, but nearly two years in and I've barely felt the need. I'm adding a secondhand B2B but I wouldn't consider it essential by any means.

4 Trojans. Here everything is expensive. You got your cells very cheap. I can get cells direct from China for $105US each. I then still need to get them from the US to St Martin. St Martin is duty free so it keeps costs down. I will buy my cells from Huston. They are $140US each. The wait for cells from China is over 3 months to the Caribbean if you are lucky.
My boat is 24v so I need 8 cells. My lifePO4 bank will be twice the capacity of yours. If I am going to go to all the trouble of building it it may as well be bigger so I have an opportunity to do other things with it. Run the 220v watermaker for example. The cost difference between small capacity cells and the 280Ah I will buy is not significant. The BMS cost and fuse costs are the same.
I will be using a B2B to charge the Trojan bank from the lithium probably. I will see how it goes. The engine battery charges from its own solar or the alternator. The B2B gives me options for another charge source but where I choose to put it in the system hadn't yet been decided. The Trojan bank could be charged from the engine as well so its all to be worked out what is best. I think I am going to need lots of switches

 

[Kelpie]

Yes I wish I'd built a second battery, I didn't realise it would cost so much more to do it later.
I just wanted to point out that comparing eight lithium cells to the cost of four Trojans is a bit unfair, because you can get nearly twice the useful capacity from the lithium battery. So you'd really need eight Trojans which makes the cost much closer.

 

[Poey50]

I think I am going to need lots of switches

Ha ha! I have five.

1. Engine start
2. House
3. Emergency link house-start circuit (run loads from the start battery or start engine from LFP)
4. Alternator service switch (isolating the alternator a) when I work on the engine or, b) in combination with 5 to re-route alternator charging from LFP to engine battery)
5. Emergency alternator to engine charge switch - (if I need to switch alternator charging direct to the start battery if LFP goes down. Combined with 3 - run loads from start battery option)

 

[geem]

Yes I wish I'd built a second battery, I didn't realise it would cost so much more to do it later.
I just wanted to point out that comparing eight lithium cells to the cost of four Trojans is a bit unfair, because you can get nearly twice the useful capacity from the lithium battery. So you'd really need eight Trojans which makes the cost much closer.

I can see you point but if you just want a relatively small set of reliable lead acid batteries on a 24v boat, 4 Trojans is the minimum. Ditto 8 cells on a lifePO4 battery is the minimum. We don't need a big battery bank as liveaboards. The four Trojans work fine for us even with a couple of fridges, mainly as we have a big (for a monohull) solar installation. Our watermaker is 220v running from the genset for 15 minutes per day. We make between 1.5 and 2.25kw of power each day on the solar to charge batteries and make a tank full of hot water. The water heating is typically about 900w. We cook on gas as it suits our lifestyle. Everything works well and we are very satisfied with the set up.
I will have to see how I can make the most of the lifepo4 bank

 

[vas]

Once you get over the lead-acid mind set of trying to get the batteries as full as quickly and as often as possible, if you aren't a high user of power then hanging around in the mid-range just becomes a natural thing to do. Then if some bigger demands are ahead charging fuller just takes a small amount of planning. I was surprised how often I've switched off chargers - including solar chargers to avoid running too full. That was unthinkable in lead acid days, of course. I'm not really trying to lengthen life - the mid-range thing just happens as part of everyday usage.

felt like that this summer (my first with LifePO4)
ended up using the watermaker more often and wasting water afterwards
was planning to replace the two 300W panels for 380W but decided not to

 

[Zing]

I fully understand where you are coming from and it makes a lot of sense to maximise life. Its real information from those using lifePO4. The reality is that you are only using 40% of the capacity of the battery in much the same way as those with lead keep their batteries between 50 and 100% for similar reasons.
None the less, I will be ordering some cells this month to build a battery. I little project over the summer.
It's not out of necessity as my lead installation is still going strong. I just fancy building stuff and doing some testing. I plan to sail home next year. We should then be into liquid cooled lifepo4 on my boat and ready for the next adventure

My situation is not usual and drives what I do. I have a very big battery 740ah @ 26v, so it’s very easy to not run it down much. I oversized it for redundancy and to allow for a full electric boat, nighttime watermaker, water heating, nighttime aircon and long periods of no genset running. If you don’t want that and most don’t then get one half the size or less. One of the many advantages of lithium is can be sized much smaller. To run it at say 80% capacity will impact life only a bit, quite the opposite of lead. I’m sure you will like your new installation and once you see its advantages with your own eyes I doubt you will go back to lead. I won’t.

 

[vas]

It has been mentioned before, so probably repeating here, but the biggest issue I had with my 304Ah@26V bank (8s) was to relax when/if it went under 50%
Took me a couple of weeks onboard to not freak out, now I'm happy running it from 20% to 95%. Now I start freaking if it goes over 95, which is a "fake" 95 as I stop charging at 3.53V per cell
Means less planning needed, run the 1.8kW watermaker whenever I like, never bother to turn off the inverter, generally be more relaxed and more like I am at home.
generator clocked 2.5h this season from the 30-40h previously. Also not going back for sure.
Problem is various fellow boaters close to me want to get lifepo batteries. Spent an hour yesterday trying to explain to one guy that adding 3X300Ah@26V "ready made" cheap chinese "batteries" and replacing his AGM with them hooking everything up as it were before IS NOT a good solution and he'll be in trouble v.soon. Not very difficult as he says:
"don't want to mess with building from separates, don't want to pay for Victron/Renogy/whatever, cheap chinese do have a bms in there, so should protect the battery, right, so why not?"

and no, I cannot point him to this thread, he'll freak out

cheers
V

 

[Poey50]

Problem is various fellow boaters close to me want to get lifepo batteries. Spent an hour yesterday trying to explain to one guy that adding 3X300Ah@26V "ready made" cheap chinese "batteries" and replacing his AGM with them hooking everything up as it were before IS NOT a good solution and he'll be in trouble v.soon. Not very difficult as he says:
"don't want to mess with building from separates, don't want to pay for Victron/Renogy/whatever, cheap chinese do have a bms in there, so should protect the battery, right, so why not?"

and no, I cannot point him to this thread, he'll freak out

If you can get him to read one article - this is good.
drop-in-lifepo4-be-an-educated-consumer

Or a Will Prowse tear-down video may do the trick. Worth noting that there was nothing wrong with the aluminium-cased prismatic cells inside the battery (which did provide the quoted capacity) but the case was used to hide the rubbish construction.

 

[GHA]

Not convinced.....
From the data here "float" seems to work quite well in just supplying loads , not really float like in a lead acid though. ....

This seems to be working pretty well so far, though still early days. Only gets to about 77% SOC.
Smartsolar regs are set to absorption 13.8v (voltage from smartshunt) , fixed time at 0m, float at 13.45v. So the regulators will give all they have in bulk until the voltage gets to 13.8v ( 3.45v per cell) then only put any current in if voltage gets below 13.45v ( 3.3625v per cell) so just keeps the SOC up near 80%.
Of course SOC accuracy will not be bang on, not that it matters that much.

Switched to float at around 14:00 >

 

[Kelpie]

I'm planning a few upgrades and would like to take the chance to sort out the layout of my system, which is currently somewhat... organic.

I'm swapping my 120A BMS for a 200A one, adding a battery monitor, and swapping from an ANL to a class T fuse. At the same time in going to try to improve the ventilation and get a bit more space between the components, and just generally tidy everything up.

Where does everybody mount their BMS? I could probably free up some space on the bulkhead, or it could go on the perspex cover above the cells.

Anybody got some pics of tidy installs that they could share, to give me some inspiration?

 

[gregcope]

the end plates came from an old road sign I fished out of a ditch.

Love it!

 

[gregcope]

I'm planning a few upgrades and would like to take the chance to sort out the layout of my system, which is currently somewhat... organic.

I'm swapping my 120A BMS for a 200A one, adding a battery monitor, and swapping from an ANL to a class T fuse. At the same time in going to try to improve the ventilation and get a bit more space between the components, and just generally tidy everything up.

Where does everybody mount their BMS? I could probably free up some space on the bulkhead, or it could go on the perspex cover above the cells.

Anybody got some pics of tidy installs that they could share, to give me some inspiration?

I taped my BMS to the side of the pack. My pack sides are GP4 1.5mm sheets to islote.

Mounted on 5mm foam off stands to give a bit of ventilation room. Taped on with strong parcel tape. It has not moved. Will dig out my post in my build thread. This all goes in a box.

 

[Kelpie]

I taped my BMS to the side of the pack. My pack sides are GP4 1.5mm sheets to islote.

Mounted on 5mm foam off stands to give a bit of ventilation room. Taped on with strong parcel tape. It has not moved. Will dig out my post in my build thread. This all goes in a box.

I've already added some alu angle to the new BMS, using bolts tapped in to the heatsink. Should be nice and sturdy and there's an inch gap underneath it for airflow.

I think one major decision I may have to make is to shift the -ve busbar, to put it nearer the +ve. So the new layout would go battery- BMS- busbars/fuses/iso- inverter.
At the moment the battery is in the middle, with the -ve busbar on one side and the +ve on the other. This makes the heavy wiring to the inverter longer than it could be.