Kelpie
Well-known member
Technically we have left the EU, but are still in a transition period.
270ah DIY LiFePO4 build
- Thread starter Poey50
- Start date
Poey50
Well-known member
Out of interest, what is the price difference in postage?
BTW - my UK delivery was paid during the transition period and didn't look excessive in relation to the weight of goods compared to your quote..
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vas
Well-known member
cheap from SWE that's a contradiction 
but only 4S, no 8S around
but only 4S, no 8S around
Kelpie
Well-known member
They didn't say what it would be to an EU country, just that it would be "much cheaper".
I've read through all of the Nordkyn articles now and to be honest I'm beginning to wonder if installing a LFP bank is a project too far. I've got about six months to get the boat ready for an extended liveaboard cruise, and it's going to be a bit of a race to the finish. There's also a lot of pressure on the budget. So whilst I know it's something of a false economy, I can see myself just buying four Trojans as I always intended. They'll probably last the 3-5 years I expect to be away.
Having said that, I'm not quite ready to give up on the idea. I need to at least get the point where I know what price I can get a safe and workable system down to. I have to spend £600+ on Trojans anyway, and I know that I can get LFP cells for that. It just doesn't leave muchfor the installation and management!
From what I've learned so far, it seems that most of the pitfalls arise when connecting LFP to certain chargers. So I'm contemplating running two almost completely separate systems. I would keep the existing lead-acid banks, charged by the engine and towed generator, and this would power instruments, nav lights, autopilot, windlass. I can dedicate some PV to this bank if it needs it. But mainly it will be the bank used when underway, so I think the hydro and alternator should keep it happy.
All other loads (inverter, fridge, laptop chargers and other portable devices) would be powered from the new and separate system, using 200Ah LFP and a 600w+ new solar array running through a new MPPT charge controller.
The only loads I'm unsure about are the cabin lights- I might put the bulk of these on the new system but leave a few 'emergency' lights on the old system.
If I need to send power one way or the other, I would either hook up a charger via an inverter, or (probably better) use a B2B. But if I find this becomes a regular occurrence, I might just shuffle around the five PV panels so that each bank gets the appropriate amount of charging. I might even be able to use the LFP bank to top up the lead-acids and stop them from sulphating.
What attracts me to this idea is that I can completely separate the LFP cells from the 'bad' charging loads (alternator) and I don't have to worry too much about sudden LVD events. I hope that the MPPT charge controller can be relied on to not over-charge, and I could protect from under-voltage using a VSR or similar. It will need a degree of active management but that's a price I'm willing to pay.
vas
Well-known member
Kelpie,
I'm also thinking of ways of implementing a hybrid system, but going the other way round since I already have invested on a decent Victron 3000VA 24V inverter charger where you cannot isolate charging to discharging (but which is 90% of the time used for discharging loads) with most charging being through solar/alternator. AFAIK, most (if not all) combined chargers/inverters have this issue to address.
I'm thinking of going B2B, keep (almost) everything as is and have the following
CHARGE SIDE as:
a 3way contactor so that Inverter+24V loads are fed either from Trojans or LiFePO4 (probably not too cheap for a high Amp one!) Not sure it's contactor that you need as I'd rather have something that is not live in order to be in state A or B, would rather have some kind of bistable switch, triggered from a small current signal for a split second, change state and stay there without a need for a constant signal...
Contactor to Trojans - LiFePO4 Offline when:
So a hybrid system roughly setup like that would need:
still wont be same as replacing a bank of trojans for sure, but much more fun setting it all up
cheers
V.
I'm also thinking of ways of implementing a hybrid system, but going the other way round since I already have invested on a decent Victron 3000VA 24V inverter charger where you cannot isolate charging to discharging (but which is 90% of the time used for discharging loads) with most charging being through solar/alternator. AFAIK, most (if not all) combined chargers/inverters have this issue to address.
I'm thinking of going B2B, keep (almost) everything as is and have the following
CHARGE SIDE as:
- Alternator/Solar charge the Trojans with the right profile (dead easy no fancy h/w and money to spent there!)
- B2B (no idea of costs!) charges your LiFePO4+simple/cheap BMS and turns off over 90% SOC
a 3way contactor so that Inverter+24V loads are fed either from Trojans or LiFePO4 (probably not too cheap for a high Amp one!) Not sure it's contactor that you need as I'd rather have something that is not live in order to be in state A or B, would rather have some kind of bistable switch, triggered from a small current signal for a split second, change state and stay there without a need for a constant signal...
Contactor to Trojans - LiFePO4 Offline when:
- 230V is sensed in input (generator/shore power) feeding the Inverter, charge/loads go to Trojans keeping their aggressive profile (this is debatable tbh-still thinking about it-could alter profile and charge the LiFePO4 instead) Mind when done so, and for LiFePO4 SOC between 20% and 90%, the B2B will be charging them on the background and whilst offline (on the load side that is)
- LiFePO4 pack under 20% SOC (don't care about the over 90% SOC as this is taken care by the BMS which is taking them offline on the charge side)
- 230V not sensed in input - Inverter used in inverter mode only
- LiFePO4 pack between 20% and 90% SOC
So a hybrid system roughly setup like that would need:
- a B2B
- a 100A 3way contactor (ymmv) I'd probably need a 150A, you may be ok with a 60A dunno
- a 20euro arduino or any simple plc to do the instructions to the 3way contactor. You may be lucky and trigger the changes from the battery monitor or charger/bms warning relays or whatever
still wont be same as replacing a bank of trojans for sure, but much more fun setting it all up
cheers
V.
Poey50
Well-known member
Another installation with alu cased cells. This time with two 4S packs each with an Overkill BMS. i assume they are arranged as two parallel packs of 12 volt nominal. Good idea for redundancy if you can afford x 2 BMSs.
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Kelpie
Well-known member
I got another email today- shipping to another EU country is $105, so about a third the cost of shipping to the UK.
May have to call in a favour from a friend...
Poey50
Well-known member
Ah well. At least we don't have any more bendy banana misery. Swings and roundabouts.
Kelpie
Well-known member
One other consideration with my dual system approach. I could make the new system 24v. The main loads on it will be new equipment, yet to be purchased- a fridge and a large inverter. I'd like to have 2.5kw+ available at 240v for a number of reasons, and this sort of current becomes much easier to handle at 24v.
The main downside of course is that if the LFP bank goes down, I can't power any of those loads from the other bank- so no fridge. And it might complicate transferring power between the banks. Further, the BMS side of it I think becomes a bit tricker. And of course no chance of pack-only monitoring being sufficient. But I'm finding it hard to find suitable high-current cut off devices rated at 250A and above, so maybe 24v make sense?
The main downside of course is that if the LFP bank goes down, I can't power any of those loads from the other bank- so no fridge. And it might complicate transferring power between the banks. Further, the BMS side of it I think becomes a bit tricker. And of course no chance of pack-only monitoring being sufficient. But I'm finding it hard to find suitable high-current cut off devices rated at 250A and above, so maybe 24v make sense?
Poey50
Well-known member
Hi Kelpie and Vas,
I haven't commented on your particular proposals as I don't have the breadth of knowledge of different systems to make detailed meaningful comments. My researches were focussed on my system although, of course, I have picked up some general LFP knowledge along the way. You might want to consider running them past the enormous (4000+ members) of the Lithium Batteries in Boats Facebook Group.
But just a quick comment on the above. It does seem a pity to give up the redundancy of having both systems at 12 volts. There are relays above 250amps.
vas
Well-known member
np Poey50,
I'm still formulating this in my mind, so wrote it down mainly as a personal note and just copied over here. Not in a hurry so will think about a few months more at least 2grand out of family kitty wont go unnoticed atm, so have to wait for it!
re Kelpie's idea, I agree it's not good, adding a level of complication for running an inverter? Not really an issue imho.
BTW Kelpie, typical Danfos BD35 compressors with their matching controller are 12/24V, don't need to do anything to switch over, just feed it 12 it will work just fine...
V.
PS. fb is out of the question for me, no way I'll get in there, if it was somewhere more acceptable I'd probably give it a try (fe, following a couple of threads in cruisers forum)
I'm still formulating this in my mind, so wrote it down mainly as a personal note and just copied over here. Not in a hurry so will think about a few months more at least
2grand out of family kitty wont go unnoticed atm, so have to wait for it!re Kelpie's idea, I agree it's not good, adding a level of complication for running an inverter? Not really an issue imho.
BTW Kelpie, typical Danfos BD35 compressors with their matching controller are 12/24V, don't need to do anything to switch over, just feed it 12 it will work just fine...
V.
PS. fb is out of the question for me, no way I'll get in there, if it was somewhere more acceptable I'd probably give it a try (fe, following a couple of threads in cruisers forum)
Poey50
Well-known member
Cruisers Forum also has some good people. I have a Facebook account which does not include a single photo, has the tightest security settings, no content and only a handful of friends that I didn't have the heart to refuse friend offers. I don't use it for anything else than accessing some very informed groups.
Kelpie
Well-known member
Yes it would be a compromise to run half the boat on 24v. Any suggestions for 250A relays? I'm really struggling to find anything, perhaps I'm not using the right search terms.
Poey50
Well-known member
As said, why not raise that question on sites that have many experienced users? Cruisers Forum, Lithium Batteries on Boats Facebook Group or DIY Solar. That gives you a knowledge base that I imagine is in excess of 10,000 people.
Zing
Well-known member
Blue Sea do a latching one. Albright is cost effective - a contactor. Tyco do them too.
vas
Well-known member
+1 search for ML-RBS Remote Battery Switch 12V, but over 150quid it looks for 300A iirc
gregcope
Well-known member
Overkill solar seem good. From my zero experience!
Ardunio libs on github; FurTrader/OverkillSolarBMS
And a nice detailed set of instructions; FurTrader/OverkillSolarBMS
Ardunio libs on github; FurTrader/OverkillSolarBMS
And a nice detailed set of instructions; FurTrader/OverkillSolarBMS
Kelpie
Well-known member
Have done, but no joy so far. There seems to be a pretty diverse range of experience out there. Clearly not everyone is up to the level of your Nordkynd chap!
Poey50
Well-known member
I've seen your posts on two of the forums. It can take a while for the knowledgeable people to pipe up. Keep the conversations there going. If the answer isn't satisfactory ask for clarification. On all forums those quickest to answer aren't always the most helpful. Rod Collins (Marine How To) steps in sometimes.
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