Community Forums

SavnTheWales · 06-19-2022, 01:48 AM

I have a Bounder 35k that includes a Battery Control Center, which controls many functions. Most importantly I was interested on how it combines the house and starting batteries together.

https://rvcustomproducts.com/f73-1020

Upon reviewing the docs I came across information that states the relay will combine the batteries when voltage hits 12.2v and disconnect when the voltage drops below 12.8v. This coincides what I was seeing when my solar system was generating power. It charged both batteries (lead acid GC2) and lead acid starting battery. At night when the solar was no longer able to keep float going the voltage would drop below 12.8v and the starting battery would no longer be latched to the house batteries due to the solenoid opening. So everything was working great.

This got me to thinking about when I switch to Lithium house batteries. These batteries should never get down to 12.8v, so the starting battery will always stay latched to the house batteries. Thus draining my starting battery. Maybe this is some of the complaints I see on here with dead starting batteries.

I suppose I could turn off my Main switch so the starting battery never latches. However then it would never get charged by my solar either… unless I manually turn the Main on and off.

What do you think?

Isaac-1 · 06-19-2022, 05:14 AM

I think you will need to redesign your battery isolation system if you go with LiFePo4 Lithium batteries.

computerguy · 06-19-2022, 08:45 AM

I don't think you are understanding correctly. If the voltage is above 12.8 the lead acids are continually charging. This is actually ok for lead acid.
I have a '16 35K and have solar and lithium for 5+ years. I did make a change to the charging system though. I have a switch to disconnect the alternator from the lithium via the BCC when the engine is on. I don't want to charge the lithiums from the alternator nearly 100% of the time. Lithium will accept whatever charge you give it. This is NOT good for the alternator and why I did it. The lead acid may drain the lithiums a smidge when the solar is not charging as the lithiums will have a higher voltage than the lead acid and the banks are connected. I have not had any adverse affects in 5+ years.
I have a whole thread on my design and install along with experiences here https://www.irv2.com/forums/f107/16-...de-323250.html

153stars · 06-19-2022, 09:20 AM

If the combiner is latched you can be using extra top charge from chassis batts, more with the coach than charging the lifepo batts because 12.8 resting voltage on chassis batts isn't really going to charge lifepo batts. Most owners disable BIRD/IRD function like mentioned as mentioned, if using more than 100ah lifepo batt. Will add a DC-DC charger for charging into lifepo will driving.

Pellmauid1 · 06-19-2022, 10:33 AM

I've had lithium batteries in my last 2 diesel pushers. They are more important than the 9 solar panels on my roof. The starting batteries also benefit because my lithiums usually are at or near 13V so the RV charges them when on shore power.

The ones that I have are Scremower brand, 120 AH. 12V. I had 4 on my prior RV and 8 on my current one. I paid $550 each and now the same ones cost $479. Very good quality, each has a digital readout with the voltage, 2 USB connectors, and each comes with a charger (which I have never used).

Absolutely trouble free. I can dry camp all day with the tv and refrigerator (no water heater load). No problem keeping the residential refrigerator running all night.

My present RV is a 2016 Entrega Anthem. And questions feel free to ask, 6026976555.

SavnTheWales · 06-25-2022, 12:46 AM

The vendor replied and recommends disabling the latching capability when going to Lithium. They provided the wiring changes which was a bonus. They did have a way to keep the emergency start option as well.

computerguy · 06-25-2022, 07:54 AM

Quote:

Originally Posted by SavnTheWales

The vendor replied and recommends disabling the latching capability when going to Lithium. They provided the wiring changes which was a bonus. They did have a way to keep the emergency start option as well.

Hope you can share those wiring changes. I'd like to see what they recommend compared to the way I did it.

SavnTheWales · 06-25-2022, 10:41 PM

Quote:

Originally Posted by computerguy

Hope you can share those wiring changes. I'd like to see what they recommend compared to the way I did it.

Vendor states:
We recommend you defeat our voltage control of the interconnect relay. Do this by removing the yellow wire from the coil terminal of the interconnect relay. Provide charging of your lithium batteries from the engine alternator by using a dc to dc converter or battery isolation manager. If you wish to retain the aux start feature of the interconnect relay, snip the wire going to P4-10 and wire it to the coil terminal from which you removed the yellow wire.

Pellmauid1 · 06-27-2022, 11:21 AM

I have never had starting batteries discharge, never disconnect them and sometimes leave the RV for long periods between use in coveredstor. Lithiums are great and when used with my 9 solar panels allow me to run (1) AC on a 20AMP outlet. Yesterday it was 95 degrees in Banks Oregon and I ran an AC all day. Amazing to me that I can do this, never had an RV before that would.