270ah DIY LiFePO4 build

[sailaboutvic]

First choice for me with an AGM would be to charge to full and completely isolate for the winter. But it needs to be cold and a good condition battery. So not, I think, the best options for me. In early lockdown I left it charged and isolated and came back after a few months to find it at 12.4 volts. Not disastrous, but not good either.

Before LFP I had a Votronic Duo Digital MPPT controller which had a trickle charge connection for the start battery. I still have that but it is an old dip-switch configured unit and can't be set for a storage voltage for my LFP. My Victron SmartSolar is perfect for maintaining the LFP at 13.3v but has nothing to offer the start battery.

I'm not really an innovator - I don't have a deep enough knowledge for that - but I know one when I see one and this method looks suitable and, at cost of £20 ...? You may have come across him as SY Destiny on the Lithium Facebook Group and, posting under CatNewBee, he has this very interesting thread on the Cruisers Forum. He knows his stuff!

Merged LiFeYPO4 1000Ah Winston prismatic cells and all electric galley... - Cruisers & Sailing Forums

S,/Y Destiny yes we know them from some years back when he was on the Med

 

[Poey50]

As has been pointed out, in colder conditions for several months simply isolating an AGM battery with no drain on it can be a good solution. This is a little risky in COVID times when access to the boat may be delayed, it also it is not ideal for longer periods in hotter weather.

If you have solar, especially a system with multiple controllers, diverting one panel to the start battery is an excellent strategy. Reduce the voltage set points on the solar controller, as the battery is now in storage mode rather than cyclic use. The solar controller will initiate a new cycle of bulk, absorption and float each day. This is not ideal with a fully charged battery at the normal voltage settings. There are a few options and the exact settings are not too critical.

My personal favourite is to reduce the float voltage to around 0.5v less than the normal float so typically around 13.2v. There is some evidence that a short boost at higher voltage helps. This avoids stratification of the electrolyte in flooded batteries, but also seem to help AGM, perhaps by ensuring the cells do not go out of balance. To achieve this, set the absorption voltage higher than the float voltage, say at 14.0v, but keep the absorption time very short, say only 5 minutes.

Thus when the solar panel starts each morning, the AGM will be sitting at around 12.7v. This will rapidly climb to 14.0v (because the battery is at, or very close to 100% SOC), stay at this voltage for 5 minutes, and then drop to 13.2v for the rest of the solar day. This is only one possible charging algorithim for an AGM battery in storage mode, but something like this is close to ideal in my view.

What solar controller do you have? I can't set an absorption period so short on my Victron Smart Solar. I have looked for a smallish switch to divert a solar charger from house to start. Do you know of one?

 

[noelex]

What solar controller do you have? I can't set an absorption period so short on my Victron Smart Solar. I have looked for a smallish switch to divert a solar charger from house to start. Do you know of one?

For the Victron controllers go to the "expert mode" and you can set any absorption time in 1 minute increments.

If you want this exact time also change absorption time to "fixed" rather than "adaptive". The other option is stay with "adaptive", but as this will reduce the absortion time by 1/6 if the morning resting voltage is high (which it should be) so mutiply the required absorption time by 6x, so 30 mins for 5 mins actual.

The other option is to retain the "tail current" to "enabled". This is something I do not normally recommend, but in this storage mode situation the controller will attempt to automatically reduce the absorption time. Personally, I prefer to set the absorption time manually rather than relying on this automatic feature, but the automatic system functions reasonably well in most situations to reduce the absorption time.

 

[Poey50]

Go the "expert mode" and you can set any absorption time in 1 minute increments.

If you want this exact time also change absorption time to "fixed" rather than "adaptive". The other option is stay with "adaptive" but as this will reduce the absortion time by 1/6 if the morning resting voltage is high (which it should be) so mutiply the required absorption time by 6x, so 30 mins for 5 mins actual.

Odd .. I found that in fixed mode the lowest absorption setting allowed wouldn't go as low as five minutes. I'll look again.

 

[geem]

Sorry, a postscript. The device attached to the front of the aluminium restraining bar is an active balancing device. This is a back-up to the BMS which passively balances the cells at the end of the charge by burning off power from any cell ahead of the others. The active balancer (which cost less than £10) balances at lower states of charge and redistributes power between cells when the difference between them exceeds 0.1volt. This should be a rare occurrence. It takes miniscule amounts of power when not engaged so I've simply left in place.

More here ...

Thanks for sharing. Very useful. The first think that strikes me is how expensive it would be for me to go lithium. My system is 24v so I need more batteries, connectors, etc. The capacity you have in terms of KW would be fine however.

 

[Poey50]

Thanks for sharing. Very useful. The first think that strikes me is how expensive it would be for me to go lithium. My system is 24v so I need more batteries, connectors, etc. The capacity you have in terms of KW would be fine however.

Yes, it works for me. I would never be able to reasonably fit a lead acid equivalent amount of batteries on our 32 footer.

 

[sailaboutvic]

Thanks for sharing. Very useful. The first think that strikes me is how expensive it would be for me to go lithium. My system is 24v so I need more batteries, connectors, etc. The capacity you have in terms of KW would be fine however.

Lithium not cheap although when I worked out to replace my 400ah Trojan and have the same amount of AH lithium it wasn't too bad.
My whole lot including B2B , breaker , BMS and wires was 2.1k .
I could had brought that price down quite a bit by,
Buying from China , having a 300ah bank , using a cheaper BMS and useing cheaper cells instead of my Calbs cell.
But I thought if I'm going to do this let's use better cells and keep the bank the same .

 

[Poey50]

In case anyone is thinking of going the DIY route - still the best route. Everyone agrees that the best quality (matched for internal resistance and capacity) cells to buy are the Winston Thundersky. (If you cut open a Victron LFP battery that is what you would find inside.) These are very expensive through European companies like GWL. But there has been universal praise (as far as I can see) for those dealing direct with Julia Yu at this company. I'm not sure what the saving is but those dealing with her seem very happy with the whole experience. In general direct imports from China are the Wild West so reputation counts and hers is a good one. She can be contacted on Facebook Messenger or better still via the Lithium Batteries on a Boat Facebook Group of which she is a member.

No personal connection.

Sky Power – Winston LiFePo4 Battery Provider

I try not to encourage people to change to LFP. in fact I hope I have put a fair few people off for whom LFP has not been sufficienty thought through. However in considering cost it is worth bearing in mind that no-one really knows how long a well-maintained LFP pack will last. Rod Collins made his 400ah pack of Winston cells eleven years ago. He capacity-tests regularly and keeps details of this at the end of his long article that is referenced on #1. Winstons tend to come in new over nominated capacity but after 11 years and 550 cycles his latest capacity test using a constant 30 amp load is still a remarkable 419ah.

 

[Kelpie]

Re costs:
I installed a new LFP system and it probably worked out cheaper than if I had bought Trojans.
Cells (4x271Ah) and BMS (120A JBD) came to £407 inc delivery etc.
There were other costs (MPPTs, fuses, etc) but these would have been the same regardless of battery type.
I did buy a B2B charger which a purely lead acid system wouldn't really have needed, but I haven't actually installed it yet and have not found that it was needed. I am getting sufficient charge from solar alone.

 

[geem]

Re costs:
I installed a new LFP system and it probably worked out cheaper than if I had bought Trojans.
Cells (4x271Ah) and BMS (120A JBD) came to £407 inc delivery etc.
There were other costs (MPPTs, fuses, etc) but these would have been the same regardless of battery type.
I did buy a B2B charger which a purely lead acid system wouldn't really have needed, but I haven't actually installed it yet and have not found that it was needed. I am getting sufficient charge from solar alone.

What cells did you buy and where from? A friend in Portugal is looking to build a large bank for a house. I think he has about 9kw of solar array. He was talking about a 10kw battery!

 

[Kelpie]

What cells did you buy and where from? A friend in Portugal is looking to build a large bank for a house. I think he has about 9kw of solar array. He was talking about a 10kw battery!

Lishen cells from Shenzhen Basen, on Alibaba. Took a couple of months to arrive but everything seems ok with them.
The best places to check for to to date info on suppliers is the DIY solar forum, and the Lithium Batteries on Boats Facebook page.

 

[vas]

bringing up the thread!

studied as recommended the diysolarforum.com and Amy Wan Shenzhen Luyuan Technology Co., Ltd - Lifepo4 battery, LTO battery comes highly recommended, so decided to contact her re 8 x EVE 280Ah matched et al cells (I'm 24V)
came back after less than two hours, quote delivered to Greece was 1090euro all in. These are the new(er) version EVE LF280K.
from her email:

So,the total price is:

Battery price + freight = $125*8+$270=$1270

With welded studs

With 8pcs busbars +16pcs nuts

With test data of each battery

not bad at all with a delivery of 60 days, tbh don't mind if it's 90, boat is not going anywhere till June.
Happy with the price, not so clear about customs (my main problem) so want to clarify some things with her before going ahead with the purchase.

Further need to figure out what I'll do re BMS. With all the Victron integration I've managed, I'd really like a VenusOS compatible BMS that I can hook up to my raspberry pi3B+ running VenusOS and which would instruct both the Victron MPPT and the Victron Multiplus II (inverter charger) so that they'll stop charging or remove loads when conditions are deemed necessary from the BMS. Avoid all the mess with setting both of them as then they are configured to be controlled from the Raspberry which is instructed by the BMS (sounds complicated, but isn't really )

will let you know how I progress.
Any suggestions for VenusOS / Victron GX device compatible BMS welcomed!

cheers

V.

 

[Poey50]

bringing up the thread!

studied as recommended the diysolarforum.com and Amy Wan Shenzhen Luyuan Technology Co., Ltd - Lifepo4 battery, LTO battery comes highly recommended, so decided to contact her re 8 x EVE 280Ah matched et al cells (I'm 24V)
came back after less than two hours, quote delivered to Greece was 1090euro all in. These are the new(er) version EVE LF280K.
from her email:


not bad at all with a delivery of 60 days, tbh don't mind if it's 90, boat is not going anywhere till June.
Happy with the price, not so clear about customs (my main problem) so want to clarify some things with her before going ahead with the purchase.

Further need to figure out what I'll do re BMS. With all the Victron integration I've managed, I'd really like a VenusOS compatible BMS that I can hook up to my raspberry pi3B+ running VenusOS and which would instruct both the Victron MPPT and the Victron Multiplus II (inverter charger) so that they'll stop charging or remove loads when conditions are deemed necessary from the BMS. Avoid all the mess with setting both of them as then they are configured to be controlled from the Raspberry which is instructed by the BMS (sounds complicated, but isn't really )

will let you know how I progress.
Any suggestions for VenusOS / Victron GX device compatible BMS welcomed!

cheers

V.

In the Wild West of importing from China, there are only two or three names that seem to stand out for reliability and customer satisfaction. For aluminium cased cells Amy Wan currently tops the list. Well done for taking the plunge!

It sounds like you will need a fairly high-end BMS. Rec-Active would, I think, do it but you may find an Electrodacus will fit the bill at a lower cost. Someone on DIY Solar has done a very good job in producing a simplified Electrodacus user-manual. I'll try to find a link and will post below.

Good luck with your future build - I'm sure many will be interested to follow your progress.

Edit: Download via orange button, top-right on this page. Failing that the very best source of advice is the Lithium Batteries on a Boat Facebook Group.

Beginner's Guide to ElectroDacus

 

[vas]

thanks!

like that, Electrodacus beginners guide: 31pages ? knackered, will have a read tomorrow!

not getting a REC one, not spending 400euro on a BMS... further their active BMS is only 4S so not for me.

looks like Amy hasn't got anything but a Chargery BMS16T 300A for 140euro but don't look interesting.

so I'll probably order as soon as I figure out what's happening with Greek customs and then spent the following 3m figuring out which BMS I want

 

[Poey50]

thanks!

like that, Electrodacus beginners guide: 31pages ? knackered, will have a read tomorrow!

not getting a REC one, not spending 400euro on a BMS... further their active BMS is only 4S so not for me.

looks like Amy hasn't got anything but a Chargery BMS16T 300A for 140euro but don't look interesting.

so I'll probably order as soon as I figure out what's happening with Greek customs and then spent the following 3m figuring out which BMS I want

Yes, the guide certainly stretches the meaning of 'beginner'.

 

[gregcope]

@vas i think there is a victron driver for thr JDB BMS that Amy can supply (via the 485 port). Let me find my links…

 

[gregcope]

Here you go;

Home · Louisvdw/dbus-serialbattery Wiki

 

[gregcope]

Not tried it mind…

 

[gregcope]

So I think you can hook up a JDB dms via rs485 on a PI into your victron kit. Not sure it will do all you want.

 

[vic008]

Is there a reason why nobody supplies a kitset including a bms, b2b charger etc etc?