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Li-BIM and Chassis Battery Charging

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osuallen

RVF VIP
Joined
Feb 12, 2020
Messages
209
Location
Oklahoma City
RV Year
2022
RV Make
Newmar
RV Model
Dutch Star 4369
RV Length
43'
Chassis
Freightliner
TOW/TOAD
2018 GMC Canyon
Fulltimer
No
A couple of weeks ago, I visited SES and did a complete upgrade on my 2022 DS 4369 with Lithium and Solar. Upgraded to 2400 watts of solar, four (4) Victron 330 ah batteries for a total of 1,320 ah, and added a second victron inverter (On the DS line from early December 2022 to the end of the model year, Victron MP 3000 was the standard inverter). SES did a fantastic install job. Unfortunately, we have not been able to really test as I am still working and that 4-letter word has demanded that I have reduced play time at the moment.

Several weeks prior to going to SES, we tripped a breaker in our storage unit and I did not know until I went to do a few things on the MH. Opened the garage door and something seemed off and noticed that there was no smiley bulldog on my watchdog. Went inside the coach and could not even get the KIB panel to turn on to see what my voltage was. Fortunately, I found the breaker box and found which breaker my unit was and turned it back on. But then I kept having bad thoughts of "next time". I had been contemplating this scenario and had been considering an RV whisper, so I ordered it and got it all hooked up. My primary purpose was to keep a remote eye on shore power and the chassis battery. (Yes, I can view the house side now with the Victron VRM).

A few weeks of observing, my chassis battery would drain down to 12.5V and the standard BIM would connect and charge to 13.3 and release. This happened around 4 times a day. Not sure what the rapid drain was, but the standard BIM was keeping the battery charged. After the upgrade and the new Li-BIM, I am not seeing the same pattern. It now has a long slow drain.. We arrived home Tuesday evening, did a quick unload and put the coach in storage. That weekend we went down to go dump, clean bugs, and get the things that we forgot. I noticed that the chassis batteries were slowly ramping down, but they were still just slightly above 12.5V, so charging was not yet engaged. Not sure why they had a quick ramp down before and now it is slow. Over the next several days I continued to observe as the chassis batteries ramped down to 12.5 and down to 12.3 and the Li-BIM had not connected. All this time, the new Lithium house batteries had fully charged and had dropped to 13.5V and were cruising along in float mode. I asked SES and they sent the document below. There are 2 criteria that have to be achieved -- Chassis below 12.5V and house above 13.5V. Obviously the chassis batteries were below 12.5, but the house were rocking along at 13.5 - not enough to trigger connecting for charging as the house voltage has to be over 13.5V. I turned off the inverter charger for a few hours to drop the house batteries, hoping that when I turned them back on and they went to bulk or absorption, that would trigger charging the chassis. I achieved the result and the house batteries moved up to 14.2 for a couple of hours, but did not trigger charging the chassis. I did that again a couple of days later with the same result of no action. When I push the battery connect, the Li-BIM definitely connects, but I am wondering if it is otherwise defective as both conditions were met to connect and charge and it did not. SES claims that since it connects with the battery connect switch - that it cannot be defective, but I am not so sure.

I also started wondering how would the Li-BIM ever keep the chassis batteries charged. If the house batteries are content to go along at 13.5V in float mode, the condition that house the be over 13.5V will never be met. --- So wondering what those of you that have an Li-BIM have experienced?


Screenshot 2024-07-01 182115.jpg
 
Mine kicks in and charges chassis battery at 12.5 V, multiple times a day. House batteries are at 13.6 at float..
 
Mine kicks in and charges chassis battery at 12.5 V, multiple times a day. House batteries are at 13.6 at float..
If I remember you were there the week after me.
 
We have lithium batteries and the li-bim, but not using Victron equipment.
House batteries a couple times ended up going to a low voltage, but luckily caught it before damage occurred.
Our solution was to install a low amperage battery maintainer on the chassis battery. Now we never have to worry about the chassis battery.
But due to the way the li-BIM works, there are times when the low amp chassis battery maintainer ends up pushing a little onto the lithium house battery when the li-BIM connects the 2 sides together.
 
I would call precision circuits and see what they think. I had mine go bad but had the opposite problem…it never disengaged…. Maybe yours is not connecting when needed.
630-515-9100. Ext 2

Btw, I do use a small battery charger, but only when the Rv is home and not plugged in. The lithiums don’t run down when parked, but I want the coach batteries to stay charged.
 
I would call precision circuits and see what they think. I had mine go bad but had the opposite problem…it never disengaged…. Maybe yours is not connecting when needed.
630-515-9100. Ext 2

Btw, I do use a small battery charger, but only when the Rv is home and not plugged in. The lithiums don’t run down when parked, but I want the coach batteries to stay charged.
Thanks Rich. I bought a charger for the chassis. Plan to do a couple of trials this weekend.
 
To be on the safe side for me is I put a trickle charger in the Rv connected to a 110 outlet on the Rv and hard wired it to the chassis battery. No when I am connected to shore power or 110 power to the Rv it is maintained. Oh, the BIM you see in the pic is no longer used. My idea of using it didn’t work out.
 

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To be on the safe side for me is I put a trickle charger in the Rv connected to a 110 outlet on the Rv and hard wired it to the chassis battery. No when I am connected to shore power or 110 power to the Rv it is maintained. Oh, the BIM you see in the pic is no longer used. My idea of using it didn’t work out.
We did the same, adding in a maintainer that takes care of the chassis battery, just to be safe.
We have the precision electronics LiBIM, but after a couple times of the chassis batteries not being maintained while parked - it was cheap insurance to add the battery maintainer.
 

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