First Charging and top balancing Lifepo4

[BrissyBrew]

Originally Posted by nebster

Do you plan to have a generator as well?

No Generator, only a DC to DC 24V 30amp charger off the alternator.

[nebster]

Originally Posted by BrissyBrew

No Generator, only a DC to DC 24V 30amp charger off the alternator.

Excellent. Sounds like a cool build. Keep us posted!

[newhaul]

Originally Posted by john61ct

Using a mix as we do in practice, almost every cycle will end at a slightly different "full" point.

just a question are you talking metaphorically or did you sneak out and suddenly get an Lfp system of your own ?
Please post your system on the systems and cost thread so we can see how your build compares to others and possible new tech that may be incorporated into our future upfit's .

[newhaul]

Originally Posted by BrissyBrew

Thank you for the replies.
Confession:I hope I don't get booted from the forum but the battery bank is for Motorhome/Land yacht. People on this board are way more knowledgable than the RV forums which I find a little more wild west and less professional input.

Clarifications:
The cells are Winston each single cell @ 400AH, in which I using 8 cells in series for a nominal 24V pack.

Changes:
3.0V as LV relay set point as suggested.

System setup:
Zeva BMS (it has some active balancing but really only resistor shunts I think way too small to make much difference on a 400AH cell) actually the BMS I can turn balancing on and off. Does have cell monitoring display 0.005 resolution.

Dual Bus: I plan to implement a dual bus system so in the advent that charging is disconnected loads are still connected to drain SOC, or if LV relay is tripped loads are disconnected and charging is still possible. Exception to the rule is the inverter/charger is going to be on the load side of the bus. I am looking at putting a secondary relay in and driving the victron inverter/charger disconnect off the HV relay, but dont plan to be plugged into shore power that often

Usage:
AC off the inverter are my high current consumers, induction cooker, hot water (it is also a heat exchanger unit), air con (split cycle inverter 400-1200W), inverter fridge running 24/7.
DC stuff is pretty low draw stuff a couple computer fans 24/7 LED lights, extraction fans.

Given possible memory effects?
Do I need to worry about shallow cycling, like reach full charge charging stops, current draw runs it down soon starts charging and tops up quickly. Solar charge controller and constant loads being the culprit.


Currently thinking of using the 10A Power supply to do initial charging until cells hold 3.35V. Then topping off any cells that need the extra juice.

hey no problem if your build is for an rv . Now as to our data being more technical and concise and safety conscious. We are . Out in the middle of the ocean there ain't no place to pull over if it goes sideways.

[Q Xopa]

Originally Posted by newhaul

just a question are you talking metaphorically or did you sneak out and suddenly get an Lfp system of your own ?
Please post your system on the systems and cost thread so we can see how your build compares to others and possible new tech that may be incorporated into our future upfit's .

Yes please John.
We would love to hear details of your system 'Using a mix as we do in practice'.

Please post details links and costs so the community can benefit.

Thanks.

[BrissyBrew]

Originally Posted by newhaul

hey no problem if your build is for an rv . Now as to our data being more technical and concise and safety conscious. We are . Out in the middle of the ocean there ain't no place to pull over if it goes sideways.

Exactly, you have marine electricians with your own codes a little different to caravan / RV market.

Australian Outback is not very forgiving either but would take my chance in the middle of the desert over the ocean any day of the week. A sailing adventure in my younger days with waves crashing over the height of 30 foot mast kinda killed any romance I had for the sea but developed a deep respect for the ocean built on fear.

I should post a system design outline at some point, just rough schematic at present.

[newhaul]

Originally Posted by BrissyBrew

Exactly, you have marine electricians with your own codes a little different to caravan / RV market.

Australian Outback is not very forgiving either but would take my chance in the middle of the desert over the ocean any day of the week. A sailing adventure in my younger days with waves crashing over the height of 30 foot mast kinda killed any romance I had for the sea but developed a deep respect for the ocean built on fear.

I should post a system design outline at some point, just rough schematic at present.

most Lfp systems on our boats are owner built but safety is utmost . Fire on a boat is the worst thing that can happen . You can't just step away and watch it burn.

On the other front 30 ft waves sounds like a fun day on the water.

[BrissyBrew]

I am setting up Victron multiplus I noticed minimum absorption time is 1hr. The current does not taper at all keeps full 50amps (would be 70 if I was using 15amp 230v) is there a way it tapers or cuts off charge on current.

[john61ct]

Normal charge regulators of all types just hold the Absorb voltage, ensure it goes no higher.

The tapering of current toward the end of the charge cycle is not controlled by any electronics.

It is the **battery** that is controlling that phenomenon, specifically the fact that the changing chemical reactions are increasing its internal resistance as 100% SoC is approached.

With lead, that tapering will usually start hours before 100%. With LFP it might be 10min or even less, depending on the charge C-rate available higher/longer, lower/shorter.

As long as the charge is held at your spec'd Absorb, and current remains higher than your desired endAmps level, say .03C (3A per 100Ah capacity) that means the bank is not yet Full.

Nothing to do with the charger.

Unless it, or the battery or wiring is faulty.