Re: lithium batteries
Reply #7 –
Here are some things I have learned along the way. If you are considering Lithium batteries think it all through as a major system in the coach and do what is appropriate. If I can help please ask, I am glad to help get you to a great end result for your coach.
120 amp charge rate is OK with 720 amp hrs of Lithium batteries. For maximum charge cycles you want to stay at or below 20% of maximum total capacity. So for 400 amp hrs charge at 80 amps max. 600 amp hrs? 120 amp charge rate is OK.
A bigger inverter/charger will pull more from the batteries when inverting and can push more when charging. Most of our coaches have 3/0 cabling between the batteries and the inverter which in general is too small, more so on the inverter side if you have appropriately limited charge rates. Switch to 4/0 cables or if you can connect two cables as you can on a Victron Multiplus, use 2 2/0 cables for each side. They have more cross section area than a single 4/0 cable and are easier to route.
Best practice (my choice) is to cable batteries to bus bars with appropriately sized cables, switches, and an appropriate fuse on the + side and a shunt on the - side. Then 4/0 minimum to the coach common post, the inverter fuse (350 to 400 amp) and then 4/0 minimum to the inverter/charger.
If you have sufficient solar you may rarely need to charge the Lithium batteries while driving. If you do need to charge while driving there are practical solutions to give you a multiple stage charge profile to the lithium batteries while driving. Don't just hook up the alternator to the Lithium Batteries. It is not approprite.
Foretravel often piled up cable lug ends on posts, often as many as 5 large lugs and a couple smaller ones. Current practice is three lugs per post maximum so replace an overburdened post with a jumpered second post nearby to share the load or better yet with a two or three post bus bar. Especially if cable sizes or counts ate increased.
A hybrid inverter will add inverted power to the passed through power from the inverter's internal transfer switch. To do this you have to bypass the second FT inverter switch between the shoreline/generator and the inverter to the inverter circuit sub panel. If it is set up so then power flows to the sub panel through the inverter only when you are on land line or generator or simply from the inverter when you are not. In this case as wired from the factory it will only be 20 amps. If you want the full land line or generator capacity to be available as it was wired from the factory then the circuit breaker in the main panel to the inverter needs to be 50 amps nd the wiring from the main panel to the inverter must also be significantly bigger. And if the hybrid side if the inverter starts adding to that power it can be passing up to 65 amps to the secondary panel. All of that wiring must be changed out for much bigger as well nd a circuit breaker panel and 65 amp circuit breaker should be added next to the inverter.
If you are using your inverter connected as originally wired the boost available from the hybrid function will never work since the 120v output of the inverter is not connected to the inverter circuit sub panel when connected to a land line or the generator. If your land line connection is 20 amps then that is all that is available as originally wired.
Lots to learn and consider.
Topic: lithium batteries