Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×
 

Go Back   Thor Forums > Thor Tech Forums > Motorhome Tech Topics
Click Here to Login
Reply
 
Thread Tools Display Modes
 
Old 04-29-2021, 04:34 PM   #1
Senior Member
 
Brand: Thor Motor Coach
Model: Axis 24.1
State: Connecticut
Posts: 1,868
THOR #20289
Precision Circuits BIM 160

Most newer Thor motorhomes are delivered with a Precision Circuits BIM 160 which will connect the house and chassis batteries under certain conditions to allow one to charge the other. PC says that it will connect when the chassis is charging and the house batteries are at 80% or less state of charge (SOC).

My experience is that the house batteries need to be well below 80% for it to connect. At 70-80% while driving for hours, I got very little house battery charging. Only on another leg when the house batteries were down to 50% did I get any decent charge, about 10% per hour.

Like my earlier post on WFCO converter charging I suspect this is just the way RV component manufacturers do things- they overstate their products capabilities.

But in this case why does it matter that the house batteries have to be below 80% for the BIM to connect?

I come from the boating world which has the same BIM requirements. But every BIM I have used on my boats, connects at any SOC as long as the propulsion engine is charging at 13.0 V or greater. Why should it matter?

And if it doesn't matter, can I replace that "crippled" PC BIM 160 with a Blue Seas or similar Automatic Charging Relay (ACR as they call them). It has all of the capabilities of the PC device including the equivalent of the aux start switch- It has a terminal that when activated connects the two batteries period, for starting boosting. It does not have the ignition switch terminal of the PC device, but I don't see what that does for me. If one or the other battery isn't at 13+ volts (which it can only be if the engine is on and charging well) then it won't connect.

Am I missing something?

David

__________________
DavidEM is online now   Reply With Quote
Old 04-29-2021, 05:16 PM   #2
Site Team
 
16ACE27's Avatar
 
Brand: Thor Motor Coach
Model: ACE 27.1
State: Florida
Posts: 15,232
THOR #7035
Quote:
Originally Posted by Precision Circuits
The BIM monitors the battery voltage of both the chassis and coach batteries over long periods of time. If it senses a charging voltage, it connects the two batteries together. If the charging system is drastically overburdened, the batteries will be isolated, however, if the
BIM sees a long term charging of both batteries it will allow the batteries to remain connected and allow the charging system to do its job. Once the batteries have charged for one hour, the BIM will isolate the batteries to prevent overcharging, and will only reconnect the batteries for charging if one of the batteries drops to approximately 80% charge, and the other is being charged. This long term monitoring of the batteries prevents the annoying relay clicking that exists in simpler isolation modules today. The BIM does not guarantee 100% battery charge, but prevents harmful battery charge levels.
The "80%" only comes into play after the 1 hour charge/disconnect cycle,

Yes, you can replace the BIM with a marine ACR if you so choose and realize the current limit of their standard ACR is 120 amps. I haven't seen an ACR with an integrated "AUX Start Switch" - that function is provided by the accompanying battery isolation/combining switch. Some ACRs do have a remote OFF function to prevent combining.
__________________
Ted & Melinda
2016 ACE 27.1
2020 Chevy Colorado Z71 Trail Runner Toad
2024 Chevrolet Trax 2RS - Soon 2B BU TOAD
16ACE27 is offline   Reply With Quote
Old 04-29-2021, 05:19 PM   #3
Senior Member
 
Judge's Avatar
 
Brand: Still Looking
Model: Dynamax Isata 3 24FWSFX
State: Florida
Posts: 4,258
THOR #12751
I have spoken to Precision Circuits. The BIM160 does not kick in until the house or chassis batteries hit 12.6V.

Mine works great.... but that was after fixing the wiring. Based on my research and experience (along with a few others on this forum), I believe Thor does not always wire it correctly.
__________________
Judge is offline   Reply With Quote
Old 04-29-2021, 05:38 PM   #4
Senior Member
 
Brand: Thor Motor Coach
Model: Axis 24.1
State: Connecticut
Posts: 1,868
THOR #20289
Quote:
Originally Posted by 16ACE27 View Post
The "80%" only comes into play after the 1 hour charge/disconnect cycle,

Yes, you can replace the BIM with a marine ACR if you so choose and realize the current limit of their standard ACR is 120 amps. I haven't seen an ACR with an integrated "AUX Start Switch" - that function is provided by the accompanying battery isolation/combining switch. Some ACRs do have a remote OFF function to prevent combining.
So you are saying that the PC BIM connects for an hour then shifts to the 80% rule. That would mean unrestricted charging for the first hour but I didn't see that. Hard to check while driving down the road, but after 2-3 hours of driving after starting at 70% it barely charged 5% overall it seems. Only after starting near 50% did I see significant current.

I mentioned the Blue Seas ACR since some are familiar with it. I probably would use the Yandina Combiner 200 which has a "nominal" 200 A rating. See Combiner 200 Sheet. It does have a "remote on" connection for starting assistance.

Yandina is an interesting single employee company that used to sell combiners under the West Marine label. Now they only sell direct or through Defender (a marine on line hardware store) to clients who know and trust their products.

David
__________________
DavidEM is online now   Reply With Quote
Old 04-29-2021, 05:41 PM   #5
Senior Member
 
Brand: Thor Motor Coach
Model: Axis 24.1
State: Connecticut
Posts: 1,868
THOR #20289
Quote:
Originally Posted by Judge View Post
I have spoken to Precision Circuits. The BIM160 does not kick in until the house or chassis batteries hit 12.6V.

Mine works great.... but that was after fixing the wiring. Based on my research and experience (along with a few others on this forum), I believe Thor does not always wire it correctly.
I remember reading what I suspect was your postings on the A vs B terminal wiring issue. Could you give me a reference or post here so I can check how mine is wired.

David
__________________
DavidEM is online now   Reply With Quote
Old 04-29-2021, 06:41 PM   #6
Site Team
 
16ACE27's Avatar
 
Brand: Thor Motor Coach
Model: ACE 27.1
State: Florida
Posts: 15,232
THOR #7035
Quote:
Originally Posted by DavidEM View Post
So you are saying that the PC BIM connects for an hour then shifts to the 80% rule. That would mean unrestricted charging for the first hour but I didn't see that. Hard to check while driving down the road, but after 2-3 hours of driving after starting at 70% it barely charged 5% overall it seems. Only after starting near 50% did I see significant current.

David
How are you determining the battery's SOC?
__________________
Ted & Melinda
2016 ACE 27.1
2020 Chevy Colorado Z71 Trail Runner Toad
2024 Chevrolet Trax 2RS - Soon 2B BU TOAD
16ACE27 is offline   Reply With Quote
Old 04-29-2021, 06:53 PM   #7
Senior Member
 
Brand: Thor Motor Coach
Model: Axis 24.1
State: Connecticut
Posts: 1,868
THOR #20289
Quote:
Originally Posted by 16ACE27 View Post
How are you determining the battery's SOC?
I installed a shunt based battery monitor that reads instantaneous amps (+ or-) and cumulative amp hours and percent of charge capacity. I am using those values, mostly just the change in cumulative amp hours divided by battery capacity. I have two, 100 Ah AGMs or 200 Ahs total capacity.

So when I said "after 2-3 hours of driving after starting at 70% it barely charged 5% overall" that means after 2-3 hours of driving after starting at 140 amp hours cumulative it barely charged 10 amp hours overall.

It should give pretty accurate data. I am definitely not using battery voltage which is highly variable based on load or charging current.

David
__________________
DavidEM is online now   Reply With Quote
Old 04-29-2021, 07:47 PM   #8
Senior Member
 
Judge's Avatar
 
Brand: Still Looking
Model: Dynamax Isata 3 24FWSFX
State: Florida
Posts: 4,258
THOR #12751
Quote:
Originally Posted by DavidEM View Post
I remember reading what I suspect was your postings on the A vs B terminal wiring issue. Could you give me a reference or post here so I can check how mine is wired.

David
I posted this in a few different threads. Here is one of the posts about it when someone else was having issues similar to mine at the time and it solved their issues.....

https://www.thorforums.com/forums/f1...ges-25455.html


Before I changed my wiring around, my house batteries were not being charged properly by the alternator. So much so I could not extend the slide when getting to camp (even with the engine running) because the voltage was too low. I had to start the generator so the Converter was boosting the house batteries and the I could open the slide.

I was also getting crazy voltage readings on the Firefly panel for the house and chassis batteries when I was driving. None of this made any sense so I was on a mission to figure out what was wrong... since I knew the dealer would never figure out in a timely fashion.

Precision Circuits even sent me a new BIM160 for no charge and that didn't fix the issues either.

Once I did a bunch of research and then changed the wiring, everything started working as it should. The batteries were all charging properly and the voltage readings were normal. I have not had any issues since.
__________________
Judge is offline   Reply With Quote
Old 04-29-2021, 10:08 PM   #9
Senior Member
 
Brand: Thor Motor Coach
Model: Axis 24.1
State: Connecticut
Posts: 1,868
THOR #20289
Judge:

Thanks for the reference. I suspect it is wired backwards as you say. Thor's own schematic indicates the coach battery is wired to the terminal on the same side as the ignition terminal. So if they wired it as their schematic shows, then according to your experience, it is wrong. Wouldn't be the first time I am sure.

The schematic is a 4 Mb file which is too big to post, but that is what it shows.

Thanks, I will check it out.

David
__________________
DavidEM is online now   Reply With Quote
Old 05-06-2021, 07:07 PM   #10
Senior Member
 
Brand: Thor Motor Coach
Model: Axis 24.1
State: Connecticut
Posts: 1,868
THOR #20289
Thanks Judge- I switched the A to B and it worked!!!!

I spent a few hours at the MH dealing with things I learned during our weeklong trip a few weeks ago. I confirmed what Judge suspected: the BIM 160 was wired backwards by Thor.

So I switched the A and B circuits. Fairly easy but you have to disconnect the coach wiring and since it is near impossible to get to the chassis battery to disconnect it, carefully switch it to the other terminal then attach the coach battery wire.

After i made the switch, I left the Fantastic Fan on to discharge the coach batteries a bit to get their voltage down below 12.6 since Judge notes that the BIM will not engage until it reaches that level. It took maybe 30 minutes for it to drop to 12.5 on the BMPro.

So I started the engine. For the first minute or so the coach battery voltage stayed at 12.5. While I was waiting I hit the aux start switch and the coach battery voltage jumped to 14.5 or so. When I released it it dropped back to 12.5 after a few seconds. So far so good.

Then a minute later it jumped back to 14.5, the voltage of the chassis alternator and stayed that way. I quickly checked my battery monitor and it was charging at 12 amps. After a few minutes it dropped as expected to about 10 amps and continued to drop for the next fifteen minutes until it was down to 3-4 amps and the coach batteries were full.

So, what a difference switching the A to B terminals makes. Thanks Judge for giving me the clue to do this. FWIW Thor's wiring was wrong and so is their schematic.

David
__________________
DavidEM is online now   Reply With Quote
Old 05-06-2021, 08:42 PM   #11
Site Team
 
16ACE27's Avatar
 
Brand: Thor Motor Coach
Model: ACE 27.1
State: Florida
Posts: 15,232
THOR #7035
Now you have to test it back the other way to verify the converter charges the chassis battery.
__________________
Ted & Melinda
2016 ACE 27.1
2020 Chevy Colorado Z71 Trail Runner Toad
2024 Chevrolet Trax 2RS - Soon 2B BU TOAD
16ACE27 is offline   Reply With Quote
Old 05-06-2021, 09:09 PM   #12
Senior Member
 
Brand: Thor Motor Coach
Model: Axis 24.1
State: Connecticut
Posts: 1,868
THOR #20289
Yes perhaps I should test it that way, but I am less concerned about that direction. It is much more important to be able to charge the coach batteries while driving.

Oh and that WFCO converter is another story. I am convinced it is acting like it is a fixed 13.6 volt charger whether it really is a three step charger or not, therefore it charges very slowly unless the batteries are well discharged, ie below 50%. So I am going to replace it with a Progressive Dynamics 9260.

David
__________________
DavidEM is online now   Reply With Quote
Old 05-06-2021, 11:13 PM   #13
Senior Member
 
Judge's Avatar
 
Brand: Still Looking
Model: Dynamax Isata 3 24FWSFX
State: Florida
Posts: 4,258
THOR #12751
Quote:
Originally Posted by DavidEM View Post
I spent a few hours at the MH dealing with things I learned during our weeklong trip a few weeks ago. I confirmed what Judge suspected: the BIM 160 was wired backwards by Thor.

So I switched the A and B circuits. Fairly easy but you have to disconnect the coach wiring and since it is near impossible to get to the chassis battery to disconnect it, carefully switch it to the other terminal then attach the coach battery wire.

After i made the switch, I left the Fantastic Fan on to discharge the coach batteries a bit to get their voltage down below 12.6 since Judge notes that the BIM will not engage until it reaches that level. It took maybe 30 minutes for it to drop to 12.5 on the BMPro.

So I started the engine. For the first minute or so the coach battery voltage stayed at 12.5. While I was waiting I hit the aux start switch and the coach battery voltage jumped to 14.5 or so. When I released it it dropped back to 12.5 after a few seconds. So far so good.

Then a minute later it jumped back to 14.5, the voltage of the chassis alternator and stayed that way. I quickly checked my battery monitor and it was charging at 12 amps. After a few minutes it dropped as expected to about 10 amps and continued to drop for the next fifteen minutes until it was down to 3-4 amps and the coach batteries were full.

So, what a difference switching the A to B terminals makes. Thanks Judge for giving me the clue to do this. FWIW Thor's wiring was wrong and so is their schematic.

David
I'm glad I could help and switching the wiring solved the problem!

What just kills me is that Precision Circuits even claims it shouldn't matter but after all of my testing and research of how other RV manufacturers were wiring the BIM it sure as heck does matter which posts the house and chassis batteries are connected to for a RV implementation.

The funny thing is I even sent this information to the Thor Factory Service Center when they thought they originally fixed the issue when I had it there 18 months ago but they didn't. I sent them all of my testing and documentation to back up my work..... but apprarently they are convinced there way is the right way or they just don't care to soend the time and effort to change the schematics and the assembly procedure.

I just wonder how may Thor coaches out there with the BIM160 / BIM225 are wired incorrectly and causing electrical issues that owners and dealers are chasing their tails over???
__________________
Judge is offline   Reply With Quote
Old 05-06-2021, 11:22 PM   #14
Senior Member
 
Brand: Thor Motor Coach
Model: Axis 24.1
State: Connecticut
Posts: 1,868
THOR #20289
Judge:

To be brutally honest, 90% of Thor owners never need the chassis charging capabilities because they always go to full hookup RV parks. And I suspect 90% of the remaining 10% don't know what is going on and don't have the skills to deal with it. It is only the 10% of the 10% (maybe you and me) who need it and understand how to fix it.

Yes it is unconscionable that Thor doesn't recognize that they are assembling their coaches incorrectly. But Precision Circuits is complicit as well.

David
__________________
DavidEM is online now   Reply With Quote
Old 05-06-2021, 11:33 PM   #15
Senior Member
 
Judge's Avatar
 
Brand: Still Looking
Model: Dynamax Isata 3 24FWSFX
State: Florida
Posts: 4,258
THOR #12751
I can guarantee it works both ways mow too but here is ak easy test....

- Plug into shore power

- Turn on the coach headlights to start draining the chassi batteries

- Watch the chassis battery vomtage and it shoild jump to 14.4V when the Converter takes over charging once the voltage drops below 12.6V
__________________
Judge is offline   Reply With Quote
Old 05-06-2021, 11:34 PM   #16
Senior Member
 
Judge's Avatar
 
Brand: Still Looking
Model: Dynamax Isata 3 24FWSFX
State: Florida
Posts: 4,258
THOR #12751
Precision Circuits BIM 160

Quote:
Originally Posted by DavidEM View Post
Judge:

To be brutally honest, 90% of Thor owners never need the chassis charging capabilities because they always go to full hookup RV parks. And I suspect 90% of the remaining 10% don't know what is going on and don't have the skills to deal with it. It is only the 10% of the 10% (maybe you and me) who need it and understand how to fix it.

Yes it is unconscionable that Thor doesn't recognize that they are assembling their coaches incorrectly. But Precision Circuits is complicit as well.

David

But you do want shore power to charge your chassis batteries when you are parked for long periods!

When itís wired incorrectly the BIM picks up the house battery voltage instead of the actual chassis battery voltage so they never charge on shore power.
__________________
Judge is offline   Reply With Quote
Old 05-27-2021, 08:07 PM   #17
Senior Member
 
Brand: Thor Motor Coach
Model: Axis 24.1
State: Connecticut
Posts: 1,868
THOR #20289
For the geeks among us, here are some observations about how the Precision Circuit's BIM works and a tip to use it more efficiently.

We dry camped for three nights this week. My house batteries started at 200 Ah and by the morning after the second night they were down to 145 Ahs. Extrapolating a bit, I am using about 30 Ahs each 24 hours.

So with the batteries down to 145Ah and the voltage on the BMPro reading 12.5 (I think it always reads a few tenths high) I started the chassis engine. The current was 40 amps, great. So I drove a few minutes to the dump station as we were heading for another campground an hour away and turned the engine off to dump. Big mistake. When I cranked up the engine five minutes later I was getting no current from the chassis battery. What happened?

This is what I think happened. When the BIM first sensed the 12.5 volts on the house battery and with the chassis engine running 14+ volts, it connected the two and I got 40 amps. After running for ten minutes I turned off the engine. That caused the BIM to reset and when I restarted 5 minutes later the house batteries were reading maybe 13+ and that was too much. The BIM wants to see 12.6 or less to connect. So all I got was a few amp hours for the first ten minutes of chassis engine running. The next hour or so I got zero, probably because my 100 amp solar panel was charging at 4 amps and that was enough to keep the house batteries above 12.6 volts.

The next morning I read 125 amp hours available on the batteries and the voltage was down a bit to 12.4. We were going home, so I started the engine and wow I got 50 amps at first but that quickly slid to 40 amps and stayed there. So again I drove to the dump, but this time didn't turn off the engine. It kept charging at 40 amps and we headed out for the 3-4 hour drive home. Half way I stopped at a rest area and the chassis engine had charged 40 amp hours but had now stopped charging even with the engine still running.

What happened. Well the PC documentation says it will maintain connection for one hour to prevent overcharging and that is exactly what happened. Here is the PC text which is a bit confusing. The first sentence says it maintains the connection, the second sentence says only for one hour.

"The BIM monitors the battery voltage of both the chassis and coach batteries over long periods of time. If it senses a charging voltage, it connects the two batteries together. If the charging system is drastically overburdened, the batteries will be isolated, however, if the BIM sees a long term charging of both batteries it will allow the batteries to remain connected and allow the charging system to do its job. Once the batteries have charged for one hour, the BIM will isolate the batteries to prevent overcharging, and will only reconnect the batteries for charging if one of the batteries drops to approximately 80% charge, and the other is being charged."

So now that I understand it better, I think I can live with it. If not I will replace it with a simple battery combiner from the marine industry, which has none of this less than 12.6 V and only connect for one hour stuff.

dAvid
__________________
DavidEM is online now   Reply With Quote
Old 09-24-2023, 04:45 PM   #18
Junior Member
 
Brand: Thor Motor Coach
State: Alabama
Posts: 11
THOR #28148
Bim 160

I realize the thread is old but I'm chasing a somewhat related issue.
In my case the bim seems to charge the batteries fine but does not isolate them when dry camping.
If the house batteries go so does the chassis battery. This leaves the chassis dead.
Sounds like you know your stuff on this isolater.. can you give me any ideas?
__________________
Brassspike is offline   Reply With Quote
Old 09-24-2023, 06:27 PM   #19
Senior Member
 
macdaddy1111's Avatar
 
Brand: Thor Motor Coach
Model: Hurricane 35m
State: North Carolina
Posts: 997
THOR #13505
Quote:
Originally Posted by Judge View Post
I have spoken to Precision Circuits. The BIM160 does not kick in until the house or chassis batteries hit 12.6V.

Mine works great.... but that was after fixing the wiring. Based on my research and experience (along with a few others on this forum), I believe Thor does not always wire it correctly.
Miss the Judge! Wonder who ran him off!!
__________________
Retired Squid who has a Retired Squid that drives him around in a RV!
macdaddy1111 is offline   Reply With Quote
Old 09-24-2023, 06:56 PM   #20
Senior Member
 
Brand: Thor Motor Coach
Model: Axis 24.1
State: Connecticut
Posts: 1,868
THOR #20289
Before going any further is your BIM 160 wired correctly with the chassis battery pos cable connected to the A terminal on the BIM and the house battery pos cable connected to the B terminal. If not, switch the wires. I don’t think that is causing your chassis battery discharge problem, but let’s start with the system wired right.

One cause is that the aux start switch is stuck on all of the time, either by mechanically binding against the dash or electrically inside the switch. That switch can be wired two ways. Either from the house 12V pos through the switch then to the Sig terminal or from chassis ground through the switch to the Sig terminal. You can measure the voltage at the Sig terminal on the BIM which will tell you if it is working right. Either fix the mechanical binding or replace the switch if electrical.

Or just disconnect the wire to the Sig terminal and see if the two batteries draw down simultaneously.

I know that the above sounds pretty arcane and why Precision Circuits allows two different wiring schemes is beyond me. Pick the safest and just use that one.

The other thing that may be causing both batteries to discharge simultaneously is an internal failure of the BIM. Replace it.

Good luck, David
__________________
DavidEM is online now   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Disclaimer:

This website is not affiliated with or endorsed by Thor Industries or any of its affiliates. This is an independent, unofficial site.




All times are GMT. The time now is 01:41 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.6.0 PL2