Charging a lithium battery from lead acid system

[elias]

Hi ,
I am thinking to install an 100ah 12v lithium battery for some extra loads I am planning to install. My question is if i can charge it through my current system ( alternator and solar ) . Is there such a b2b charger for lithium batteries from lead acid banks ?

[Yngmar]

Yes, and it's called a B2B charger!

[elias]

I have one onboard already cause I have by law a dedicated battery and charger for the vhf battery , but will be that charger ok ? Lithium battery should require specific charge process that’s lead acid no?

[Yngmar]

You'll have to look at the manual or tell us which one you've got - the crystal ball is cloudy today 

There are definitely B2B chargers suitable for charging LiFePo batteries, Victron Orion series for example and probably many others.

[elias]

You are right , is an DBC1212 https://shelectro.gr/language/en/dc-dc-dual-battery-changers-and-chargers/ no manual unfortunately , it says specifically for lead acid , so I guess is a no

[tiger79]

If you buy a 100Ah battery with integral BMS (eg Victron SuperPack), you can charge it basically in the same way that a lead-acid battery is charged.  So you could keep the DBC1212.

Alternatively, you could charge it from the house batteries using a low-loss isolator (eg Victron Argofet).

[elias]

So a key factor is to buy a battery with built in BMS so it can self regulate the charging process ?

[tiger79]

So a key factor is to buy a battery with built in BMS so it can self regulate the charging process ?

I believe so.  Otherwise, you need to use an external BMS to manage the battery.  Ones with built-in BMS are often described as "drop in" replacements for lead-acid.

[Yngmar]

That's probably a smarter idea, as they've got integrated BMS and charging and are easier to use. Cost a bit more, but then you don't need to buy a new B2B charger and come out around the same cost.

[AndyS]

I have been looking at swapping to Lithium batteries for a while, but even with the "drop-in" replacement versions it looks like there are various other modifications needed...on my 2008 boat it would be a minimum of changing the charger and modifying/replacing the alternator to cope with the higher charge voltage and current demand of the Lithium batteries.  Or alternatively using a battery-to-battery charger but losing some charging capability and efficiency.

Just noticed that Ryan of "Ryan & Sophie Sailing" have just made an update video on this.  For me it helped cut through a lot of the conflicting information that is also around. 

The bit on drop-in replacements is at 9:23 in the attached video.

https://youtu.be/vraRhNpEWcE