Wiring for Lithium Batteries convert on a SO 419

[bitsailor]

I am planning to convert my 4x 105ah AGM batteries to 2x 200ah Renogy Lithium batteries. I have sketched out what I think the new wiring diagram will look like and would be great to get some advice from anyone who is familiar or done this  before. 

I have attached the original and new diagrams for reference. The changes from the original are the areas highlighted in yellow.

Some notes:
* The starter battery and thruster batteries will remain AGM type batteries. These will be charged by the alternator, and original AC charger when plugged in.
* A Renogy DC-DC smart charger will be used to charge the Lithium batteries from the alternator. The charger I am installing specifies that it should be connected to the start battery and will only charge the lithium batteries when the voltage is above 13.2 and will stop charging when it dips below 12.7
* When connected to AC power, the currently installed Magnum charger/inverter will charge the lithium batteries.

Feedback/thoughts/ideas appreciated

[mic98034]

Make sure your Magnum charger and your DC-DC charger both have a LiFePO4 charger profile, and use that.

But then you probably already thought of that ;-)

[bitsailor]

We just completed the lithium conversion on our SO 419. 

Just providing an update here.

With a bit of planning, the installation was relatively easy and the system is able to work fine alongside the existing AGM batteries for the starter and thruster. The lithiums are charged via a DC-DC off the alternator while the motor is running. They can also be charged either directly off our Magnum inverter, or off our factory battery charger when plugged into shore power. We achieved this by connecting the DC-DC converter to our starter battery, so it charges the lithiums both when the alternator or the factory AC charger is running.

We used 2x 200ah renogy lifepo4 which were about 1/4 of the price of mainstream batteries. Replacing the 4x 105ah factory agm batteries.

In order to fit the batteries we removed the front of the battery box and built cleats around the new batteries.

Photos attached, wiring diagram is in my original thread, and happy to answer any questions.

[barryl]

Hi,

Thanks for this post. I plan on doing the same thing over next winter on my 2011 409. Did you make any changes to your alternator to provide for higher output? How long do you have to run the engine to replace 200AMPS? 

Thanks,
Barry

[mred25234]

Jan 26, 2024 22:09:58 GMT bitsailor said:

We just completed the lithium conversion on our SO 419. 

Just providing an update here.

With a bit of planning, the installation was relatively easy and the system is able to work fine alongside the existing AGM batteries for the starter and thruster. The lithiums are charged via a DC-DC off the alternator while the motor is running. They can also be charged either directly off our Magnum inverter, or off our factory battery charger when plugged into shore power. We achieved this by connecting the DC-DC converter to our starter battery, so it charges the lithiums both when the alternator or the factory AC charger is running.

We used 2x 200ah renogy lifepo4 which were about 1/4 of the price of mainstream batteries. Replacing the 4x 105ah factory agm batteries.

In order to fit the batteries we removed the front of the battery box and built cleats around the new batteries.

Photos attached, wiring diagram is in my original thread, and happy to answer any questions.

Can you estimate your total cost for this project?

[bitsailor]

Barry - we did not modify the alternator but decided to run it though the DC-DC converter which is rated at 50A. This means our max charge rate on the alternator is 50A. Our primary charge while cruising is solar so not an issue for us. Using a smart alternator that can charge lithium directly is another option if that is your primary charge source while cruising.


mred25234 - Costs will vary based on gear etc - you can get 200ah batteries for around 900CAD each - we went with Renogy. DC-DC and cabling etc comes to about 400-500 CAD. Install was approx 10hrs of labour.

[MartyB]

200ahr lithium for $900 is a great price. Locally, Seattle they are around $1100 USD+ depending upon the brand size etc.

I have a size 31 AGM, put in a new charger last summer vs the one I had from 15 years ago. I can do lithium, agm and lead. I can have a lead on one circuit, ie the motor start battery, and AGM as my house is. With a flip of a switch/button, I can change out to one of the other types. I figure a 31 sized lithium should net me at least twice if not three times the use time as the AGM or Lead versions I had before, along with lighter.....Cruisers may not worry, but a racer does! LOL

Marty