Lithium Battery Upgrade

[Dae Sung]

I have a 2021 HR Nautica 33TL DP with 4 6 volt coach batteries (2 bank series for 12v total).  Installing 400 Ah of 12 volt lithium batteries.  Currently the coach has a OEM non lithium 225 BIM from precision circuits.  Do I need to do anything else other than swapping the non lithium BIM for a lithium BIM to protect the alternator?  Thanks in advance.

[Mark B]

You'll have to check you inverter charger settings to see if the charge profile is compatible with lithium batteries. More than likely it is at that new of an age but never assume it is.

[1nolaguy]

As Mark B said, first check you inverter converter to make sure it is compatible with Lithium chemistry and make any necessary changes. Failure to do so can permanently damage your new batteries. The best place to check this is directly with the manufacturer where they can check the based on the I/C serial number. In addition, I highly recommend you invest in a shunt based battery monitor.   Victron makes a great one but if you are not into tracking your battery SOC on your phone a good alternative can be gotten on Amazon for about $40. With your age of rig you likely have a battery monitor system based on voltage. This is not effective with LFP batteries as the voltage drop is minimal until they are depleted and then the voltage drops precipitously. I have first hand experience with this when everything is fine until its not. While this is not "necessary", it is a worthwhile investment.

[Dae Sung]

Thanks for the replies, good to go for lithium on the inverter and solar controller.  Any thoughts or suggestions are greatly appreciated on the Li-Bim.  

[Dae Sung]

Also getting feedback from most rv'rs I should go with a DC to DC Charger, I can.  I would assume I remove the existing non lithium BIM, and install there?

 

  

[1nolaguy]

Dc-dc charger is good if you do not spend most time with full hookups and move often or if you rely on a Gen to charge the batteries. If using an existing connection to replace with a dc-dc converter 1) make sure wiring is properly sized. 2) make sure dc-dc is about 50% or less of the alternators rated output. Failure to do so can lead to other problems.

[Dae Sung]

Makes sense thanks!  We will probably boon dock in this rig about 30% or less, would you then recommend the Li-Bim?

 

[wamcneil]

1 hour ago, Dae Sung said:

Also getting feedback from most rv'rs I should go with a DC to DC Charger, I can.  I would assume I remove the existing non lithium BIM, and install there?

I think the main concern around the BIM is for your alternator, rather than battery health. Since the lithium batteries can accept charge so much faster than the GC batteries, it may peg the alternator at its limit for long periods and overheat. So you generally want to keep the house batteries disconnected from the alternator to protect the alternator.

DC/DC charger would charge the house battery underway, but it won't keep the chassis battery charged when parked. 

Personally, I've removed my battery isolators, have not installed a DC/DC charger and so far haven't missed it. IMO, the DC/DC chargers seem really expensive for what they do. For my purposes, it's not like a sophisticated 3-stage charger is needed. I've considered a cheap buck/boost converter with adjustable output voltage and set it to something like 13.2v.

I installed a small 10a battery charger dedicated to the chassis batteries (plugged into the non-inverted block heater outlet) to keep the chassis charged when parked. And I've still got the big battery combiner solenoid that I could engage if needed.

But so far I haven't felt compelled to add a DC/DC charger. Underway, there's usually plenty of solar, and in warm weather the generator is running for AC.

Cheers,

Walter

Edited April 19, 2022 by wamcneil

[Dae Sung]

Ok thanks Walter, I might give that a try.  -Russell

[CAT Stephen]

Dae Sung, do you have the flexibility to locate your DC to DC converter outside of the battery compartment (explosion proof DC to DC chargers are a 5X cost uplift)?  If you do, based upon your current Cummins ISB 160A Maximum output alternator, I recommend the following Renogy 60A DC-DC charger, assuming that your inverter is not attached to your alternator output: https://smile.amazon.com/Renogy-60A-Battery-Multi-Stage-Charging/dp/B07Z4GSYC2/ref=sr_1_3?crid=1778Q0M70R3UY&keywords=renogy+60a+dc-dc+charger&qid=1650393252&sprefix=renogy+60A+DC%2Caps%2C2149&sr=8-3

Edited April 19, 2022 by CAT Stephen
Revised

[Dae Sung]

Hi there, I can locate it outside of the compartment.  The existing BIM is opposite the battery compartment in a separate electronics compartment so easy to install.  I will check on the inverter/alternator connection, but I do not believe it is. Thanks for the input leaning toward a DC/DC charge.

[wamcneil]

22 hours ago, CAT Stephen said:

do you have the flexibility to locate your DC to DC converter outside of the battery compartment (explosion proof DC to DC chargers are a 5X cost uplift)?

Why does it need to be explosionproof? Are starting batteries in the compartment with house batteries?

[anand.s]

Hi all -

I have my DC-DC (renogy equiv) in the top tray of my battery compartment with 3-SLA batteries in the lower one.  I just did the lithium upgrade and have no other place to put the DC-DC setup.  The ignition conversation has me rightly spooked.  The box does vent with the holes that wires come through in the top rear, but I’m concerned.  The simpler solution for me may be to replace the starting batteries with AGM.   They are coming to time anyhow.  Would that still pose venting problems?

2007 Beaver Marquis.

Thanks!

Anand