UPGRADING TO LiFePO4 - QUESTIONS

[tadej.mezek]

Hi All,

I am unable to find satisfactory informations online (youtube + google) in order to get exact answers to few questions.

The current setup is:

Standard Bavaria 44 (2002) wiring with Studer SBM-02 battery monitor and shunt.
3x 105Ah Lead Acid House battery bank
1x 105Ah Lead Acid Engine battery.

I would like to change to LPF (LiPoFe) - looking closely to LIONTRON Lithium LiFePO4 LX Smart BMS 12,8V 150Ah (3 X = 450Ah)

My Questions are;
- why vast majority of people are using ISOLATED DC to DC (B2B) chargers if there shall be only ONE common ground anyway. Bavaria has common
ground for both batteries and I believe also all other "mass production boats"?
- Is use of NON isolated B2B charger then OK? (I found one shematic online and is attached to this msg.

- Can one use ISOLATED B2B charger (I already bought 2 of them and bridge the GND (Ground)? Is there anyone who upgraded to LFP and knows which things needs to be altered or changed in order to do it right?

- What is correct way of dealing with grounds in Bavaria environment? Shematics seems vague to me.

- By coupling parallel two B2B chargers (I own Victron Isolated B2B 30A) one can charge LFP 60A; how safe is this considering the usage of standard stock D2-55 70A alternator? Do you advise using only 1 30A B2B? One article suggest using only 50% of alternator capacity.

-Are there any other "Bavaria special" cost saving solutions, which one needs to be aware of when changing to LFP?

- What is the correct way of charging LFP with solar panels? Most installations I have seen are using MPPT which is directly linked to any sort of batteries, in this case LFP. But some installations are using MPPT controller, which is driving B2B charger in order to charge the batteries, which path is correct?( by using Victron MPPT, you select which type of Battery you are charging...)

- What happens in situation when connected to shore power with Mastervolt EVOSMART 12V-35A charger. (In case we use 60A B2B it will deplete the engine battery or?)

Basically installation /replacement shall be very simple; practically drop in replacement, expept that a B2B charger is installed in between Engine and House (new LFP bank) battery bank. Everything else stays the same, is that correct? Alternatively, by using alternator regulator, which I believe is not very popular/favorable.



I am attaching the pictures of what I found online. Hope this does not violate any kind of rules.

Thank you for answers,

Ted, SY MAMORA

[Yngmar]

- By coupling parallel two B2B chargers (I own Victron Isolated B2B 30A) one can charge LFP 60A; how safe is this considering the usage of standard stock D2-55 70A alternator? Do you advise using only 1 30A B2B? One article suggest using only 50% of alternator capacity.

Not safe without thermal management of the alternator. They are not designed for outputting those 70A over any length of time. They will overheat dramatically. More so when running at low rpm. In case of our friends catamaran (2 engines), it fried both internal regulators, but the rectifiers survived, so they're putting out unregulated 15V. This will over time boil out the starter battery. The B2B charger doesn't mind it though!

I would considering an A2B charger or upgrading alternators. Unfortunately the Balmar alternator + MaxCharge regulator are super expensive and the Sterling A2B I cannot really recommend. If you have an external switching input on the B2B, you can also cobble together your own thermal regulator from a standard thermostat controller.

[tadej.mezek]

Thank you for your answer;

The major question still is and that is how to properly deal with masses (GND).

[SYJetzt]

There is no reason for isolated b2b Chargers.
I run  my lfp system with ground coupled batteries without any troubles.
Connect a solar charger direct to the lfp house bank, i would suggest a mppt charger which should have a fully adjustable charging characteristic.
As Yngmar mentioned, our standard alternators aren't able to deliver the rated current over longer times. So a 30Amp b2b charger between starter and house bank is enough. Charging currents of 60Amps and more will kill your alternator over time (don't ask me, why i know this...).
Remove all charge splitting systems on your alternator and keep only the charging line between alternator and starter battery but leave the sensor cable from the starter battery to the alternator in place.
I don't know the characteristics of your 220V mains charger, but it should have a lfp charging characteristic. If not, charge only the starter battery and your b2b Charger will get your lfp charged.
Don't forget all the neccessary fuses and use only cabling with proper cross sections, because the currents in thoes systems are huge....

[marioxp]

- What happens in situation when connected to shore power with Mastervolt EVOSMART 12V-35A charger. (In case we use 60A B2B it will deplete the engine battery or?)

There is a serious chance that the engine battery will be discharged, because the Mastervolt will provide a voltage of 13.7 V and the B2B charger will start charging the house batteries, but the Mastervolt charges with 30A and the B2B discharges with 60A, after a certain time the engine battery will be discharged. All the time, the B2B will sense 13.7 V and think that the engine battery is full.

https://www.youtube.com/watch?v=rDXixCzg6iw&t=6s

Your entire electrical system is made for batteries of approx. 315 Ah, (effective 157 Ah). you are now upgrading the system to 450 Ah (effective 360 Ah) that is a big jump. Electricity production are the same as mine, which I have 2x150Ah. Your system is not in balance, it will take a long time for lithium batteries to charge, and they slowly degrade if they are discharged.