LiFePO4 Electric Schematic for Review and Comments

[LeighC]

Why not install a BMS the has a programmable LV, HV, Cell Temp or cell balance warning well before the disconnect takes place?
This would allow action to be taken well before a critical situation

[newhaul]

Originally Posted by goboatingnow

One mans way over engineering is another’s good engineering , people spending $$$$$$$$ on lithium yet somehow baulk at installing a proper alternator.

What do you consider $$$$$ spent on lifepo4.

I have 600 all in 250ah Daly bms and smart meter with shunt .
Stock alternator with a b2b of appropriate size is plenty.

[SV_FlyingTigress]

Originally Posted by PaulCrawhorn

Requires way over-engineering.

Just keep a lead batt on the engine/alt circuit. Usually the Starter, two birds one stone.

Otherwise can be a small cheap "sacrificial" unit, just replace every 2-3 years even if never needed.

I was wondering if somehow adding a lead acid to the charging circuit as a cheap sink would address that perhaps something this type of approach.

https://www.youtube.com/watch?v=XAOhT2HwKWM&t=325s

[SV_FlyingTigress]

Originally Posted by s/v Jedi

Stephen, you are looking at details but those should only be addressed after the fundamentals are good. Also, you have to decide if you want to comply with ABYC recommendations.

Simply said: a BMS is required to send out warning signals about an imminent LVC or HVC. This is before the BMS actually disconnects the battery. In case of a:
- LVC warning: the battery is empty. Using this warning signal, you must automatically switch off things like an inverter.
- HVC warning: the battery, or maybe just one internal cell, is overcharging. Using this warning signal, you must automatically switch off things like an alternator or solar controller (any charge source).

If this works well, the actual LVC or HVC may be avoided, and for sure battery life is extended.


For batteries with internal BMS, this means it must have external connections for this. Also, some BMS’s don’t have these warning signals: they are not allowed under ABYC and ISO setups.

Got it Jedi, thanks that is clear. Because my boat was implemented per this diagram and went online earlier this week and is installed and online now, I am in a situation where I am forced to tweak the physical installation to address material gaps. It was a bit of a ready, fire, aim unfortunately. So, I am trying to do the gap analysis described and migrate my implementation toward a safe design. Dakota BMS, per Dakota, does not feature external communication. Dakota is a Victron dealer as well and when I asked them they said to layer in a Victron external BMS to address graceful alternator shutdown. Integration is the question. I am just trying to sequence things and address critical items in situ in Guatemala and deal with lower likelihood/impact issues when I get the vessel in the US next year. To that I need to understand specific operational question as a function of what is implemented, ergo the detail questions. If the battery, vs the installation, has to be ABYC compliant and that compliance requires direct BMS>>Alternator management , then that cannot happen with my installation.

[SV_FlyingTigress]

Originally Posted by goboatingnow

One must assume that for safety sakes HVC and LVC BMS shutdown events will always occur when least expected. Battery faults themselves produce these faults.

Hence to protect your alternators they will have to instructed by the BMS to stop charging just before the BMS disconnects.

Makes sense thanks GBN!

[SV_FlyingTigress]

Any thoughts on this: Balmar APM-12 Alternator Protection Module for 12 volt systems https://shop.pkys.com/Balmar-APM-12-...EaAnamEALw_wcB

Also the Victron external BMS isn't a lot more $$$ than this, it is just the integration question.

[goboatingnow]

Originally Posted by newhaul

What do you consider $$$$$ spent on lifepo4.



I have 600 all in 250ah Daly bms and smart meter with shunt .

Stock alternator with a b2b of appropriate size is plenty.

Including the LFP batteries ? I doubt it.

[newhaul]

Originally Posted by goboatingnow

Including the LFP batteries ? I doubt it.

My bad 687.00

492 for the batteries includes shipping .
147 for the 200amp bms.
48. For the meter with the 350 amp shunt.

https://www.cruisersforum.com/forums...ml#post3063601

And yes I have the receipts.

[goboatingnow]

Originally Posted by newhaul

My bad 687.00



492 for the batteries includes shipping .

147 for the 200amp bms.

48. For the meter with the 350 amp shunt.



https://www.cruisersforum.com/forums...ml#post3063601



And yes I have the receipts.

Wow that’s very cheap batteries

[newhaul]

Originally Posted by goboatingnow

Wow that’s very cheap batteries

Factory direct calb aluminum case cells .labeled as 240ah cells tested at 262ah .

B2b purchase

[rgleason]

I've been following newhaul's trials and step by step improvements for several years now since he has a small boat, and what he's learned and accomplished is pretty good and thoughtful considering his sailor's budget, and commendable scavenge and reuse approach.

[goboatingnow]

Originally Posted by newhaul

Factory direct calb aluminum case cells .labeled as 240ah cells tested at 262ah .



B2b purchase

I’m looking at GWL Solar own brand LFP cells as I need a EU source and AFD transport.

At preset the sweet spot is 70Ah cells at $80 each ex shipping

[s/v Jedi]

Originally Posted by goboatingnow

I’m looking at GWL Solar own brand LFP cells as I need a EU source and AFD transport.

At preset the sweet spot is 70Ah cells at $80 each ex shipping

Expensive. For Winston, considered the best in the market, I paid $1 per Ah.

[PUDDLE JUMPER II]

Would you use a Winston battery for a starter battery? Or would you go AGM? I have a small dog onboard and I am trying to eliminate all lead acid batteries for safety... Hence the ask...

[newhaul]

Originally Posted by PUDDLE JUMPER II

Would you use a Winston battery for a starter battery? Or would you go AGM? I have a small dog onboard and I am trying to eliminate all lead acid batteries for safety... Hence the ask...

Are you looking at using your house bank or a separate battery for the iron wind?