Replacing AGMs with Lithium on a 2018 Leopard 40

[B4A]

Hi all,

I'm looking for advise. I'm considering swapping my 3 years old AGMs house battery bank and replacing them with lithium (LiFePO 4). I haven't followed lithium's industry progress in the last 3 years.

My questions are:

1) What does it take to replace AGMs with lithium? It is just a matter of changing settings to the inverter/MPPT/Battery monitor? Or does it require re-wiring and/or additional equipment as well?

2) What is the most convenient and safe LiFePo brand these days?

Here's my equipment:

- Victron Venus version 2.60
- Victron BMV712
- Victron MultiPlus 12/3000/120-50 - Firmware 413
- Victron MPPT
- Victron PWM

Thanks in advance for your expert advise!

[ForeverDes]

I'm hardly qualified to answer, considering a few days ago I made a similar post. However, I've received a lot of good advice and data for my own conversion, and I'll share the link to that discussion.


This is the gist of what I have processed:

Solar charging LFP through a properly programmed mppt controller is fine.
Directly charging through the alternator requires an external regulator because LFP charging rates don't diminish (much) as SoC increases, which will cause an alternator to burn out. As will bms disconnecting the bank while the alternator is running.


Alternator to FLA start battery with a dc to dc charger from the start battery to LFP house bank provides a "buffer" and a standard alternator should be fine.


LFP like a high charge rate of around 1C, which is difficult to provide on a boat without a dedicated charger and generator or shore power. (in my case I'm not worried about charging at 1C, and I'm not worried about having a high capacity dedicated charger right now)


With your 120amp inverter charger you may get close to 1C depending on your battery bank capacity.


I assume your Victron mppt controller is fully programmable, so it should work well to charge LFP.


The rest of your Victron Equipment should work fine with LFP. As far as I know, you'll have to fully discharge your new bank to reprogram the BMV712.


Victron makes a dc to dc charger as well, that should work and communicate with your existing equipment (ymmv, I haven't personally used Victron Equipment.)

[Adelie]

Why the desire to change? Weight? Are you having problems with the AGMs?
Real deep cycle FLAs would be cheaper than AGMs and last longer. AGMs are like LiFePo in that they need to be charged hard, though not as hard as LFP.

If you buy plug-n-play LFPs they are almost 2x the cost of FLA over the life of the battery and that’s assuming they get a 10yr life.

If you DIY you LFPs you can be a lot cheaper than FLAs.

One thing to keep in mind with LFPs is that when you connect an inverter you need to go thru a giant capacitor or resister. Inverters, even off and not producing have giant capacitors that charge up as soon as you connect to power and there will be a giant current spike, like 1,000A for milliseconds. Doesn’t hurt the cells but with LFPs the spike can fry the BMS. As I understand it this is more a problem with bigger inverters, 4,000W.

https://community.victronenergy.com/...ttery-pac.html

https://diysolarforum.com/threads/in...ing-spark.295/

https://forum.solar-electric.com/dis...-lfp-batteries