Li-BIM 225 as a battery trickle charger

[Chateau_Nomad]

A question for those familiar with how a Precision Circuits Li-BIM 225 battery isolation manager works:

My intent is to keep a simple trickle charge going to the motorhome chassis battery during 5+ months winter storage. Consider that the "house" batteries (LiFePO4) DO NOT connect with the coach chassis battery (FLA) via the Li-BIM 225 solenoid without the engine running. It seems a simple way to "trick" the Li-BIM to connect would be to run a jumper wire from the "ignition" terminal on the Li-BIM to the chassis battery during storage. With the Li-BIM seeing 12 volts, wouldn't this theoretically trigger it's programmed connection strategy? The intent is to let the Li-BIM manage connecting/disconnecting to avoid an overcharge situation on the chassis battery, yet would still allow enough charge to keep it topped up. The charging source is 600 watts of solar panels.

Any insights / opinions welcome!

[16ACE27]

So you want to "trick" the LiBIM to connect the lithium house batteries and the LA chassis battery together without sufficient charging capability to charge the house batteries? Because once they are connected, the resting voltage of the lithium batteries is going to look like charging voltage to the LA batteries and the current will probably flow from the house to the chassis batteries if they have been "maintained" at 13.2 VDC.

[Chateau_Nomad]

Originally Posted by 16ACE27

So you want to "trick" the LiBIM to connect the lithium house batteries and the LA chassis battery together without sufficient charging capability to charge the house batteries? Because once they are connected, the resting voltage of the lithium batteries is going to look like charging voltage to the LA batteries and the current will probably flow from the house to the chassis batteries if they have been "maintained" at 13.2 VDC.

...which is what I want. Lithium batteries are being charged/maintained from solar.

[16ACE27]

Originally Posted by Chateau_Nomad

...which is what I want. Lithium batteries are being charged/maintained from solar.

OK, I thought the chassis battery was under the trickle charge. Yeah, that should work.

[galOnTheGo]

MY THOUGHTS --- i'm not sure about it working without testing it myself, but, if your only source of power is the solar, and that solar power will be very limited as far as when it is available, ..with the li-bim on all the time, and no power coming to charge, i am not sure how it will behave. (SIDE NOTE:This being the case, it may be draining more than charging) in my experience, the bim tends to go "wild" when it thinks there is a charge to be managed and there is no charge. the thing i would need to do is test it with a multimeter, in several scenarios. JUST MY THOUGHTS

[RizeMaster]

Originally Posted by Chateau_Nomad

Any insights / opinions welcome!

Huh, I did not know that (some?) BIMs only connect when the engine is running. My (non-Li) BIM160 is always working, so when solar is charging the coach batteries, suddenly - clonk - it connects and charges the chassis battery. May be different for Li chemistry.

Are you sure about <<run a jumper wire from the "ignition" terminal on the Li-BIM to the chassis battery>>? I guess see how it goes.

On the BIM160, one can override the functionality by removing the ground wire. That way one can connect or disconnect both batteries permanently (which is what I understand you want to do while in storage).

Momentarily touching the SIG terminal with the ground wire will flip the relay. Open/not connected vs closed/connected.

Anyway, this may not apply to or work with the 225.

[Chateau_Nomad]

Let me clarify that it's my "understanding" that the Li-BIM 225 does not connect without power to the ignition terminal. I cannot find any details otherwise. It seems to me the device's intention by design is to provide alternator based charging to separately wired house batteries AND provide a method of engine jump starting via house batteries due to a dead chassis battery. The scenarios for connecting the separate batteries imply engine running... with exception of E-start. A PDF can be found by searching "Li-BIM 225 wiring diagram".

My previous stock Trombetta setup did in fact connect without alternator power, and did an excellent job of keeping the chassis battery charged with minimal solar. But I have yet to hear the Li-BIM "thunk" to connect this way... I initially thought it did.

Maybe a call to Precision Circuits tech staff next week to clarify. Seems like an oversight, but I'm no electrical engineer!

[16ACE27]

Originally Posted by Chateau_Nomad

Let me clarify that it's my "understanding" that the Li-BIM 225 does not connect without power to the ignition terminal. I cannot find any details otherwise. It seems to me the device's intention by design is to provide alternator based charging to separately wired house batteries AND provide a method of engine jump starting via house batteries due to a dead chassis battery. The scenarios for connecting the separate batteries imply engine running... with exception of E-start. A PDF can be found by searching "Li-BIM 225 wiring diagram".

My previous stock Trombetta setup did in fact connect without alternator power, and did an excellent job of keeping the chassis battery charged with minimal solar. But I have yet to hear the Li-BIM "thunk" to connect this way... I initially thought it did.

Maybe a call to Precision Circuits tech staff next week to clarify. Seems like an oversight, but I'm no electrical engineer!

It's my understanding that the Li-BIM is bi-directional like the original BIM; so it also allows charging of the chassis battery from the house batteries/converter when plugged into SP.

From your referenced PDF:

Senario 2: The Chassis battery voltage is below 12.5V and a Coach battery voltage greater than 13.5V
Response: The LI-BIM 225 will connect the batteries for 1 hour, then disconnect the batteries for a wait time of 2 minutes. After this wait time, a new voltage reading will
be taken of each battery. If the voltages remain within the scenario's parameters, the response repeats.

So you shouldn't need that ignition jumper if your solar charger keeps the house batteries above 13.5 VDC.

[Chateau_Nomad]

I think their explanation is ambiguous... Scenario #2 doesn't give engine status either ON or OFF but scenario #1 explicitly states engine ON.

I think the answer is a call or email to their tech department for clarification. Then I think I'll monitor chassis battery voltage for a week or two.

Because it is not taken into account by the BIM logic: and having to have the "engine on" for chassis battery charging while on SP is ridiculous.

[Chateau_Nomad]

UPDATE:

I reached out to Precision Circuits regarding my concerns. According to the tech who PROMPTLY responded the Li-BIM 225 is bi-directional in operation... regardless of engine running (supplying 12 volts to ignition terminal) the device WILL connect house and chassis batteries based on monitored voltages. Excellent!

This means that the device will definitely keep the chassis battery charged as well as house batteries during 5+ months of winter storage.

House batteries > chassis battery:
With solar or shore power AND house battery voltage ABOVE 13.5 volts, if the chassis battery drops below 12.5 volts, the Li-BIM will connect for one hour then disconnect for two minutes... then take a new reading.

Chassis battery > house batteries:
The "driving scenario" is connect for 15 minutes then disconnect for 20 minutes to protect the alternator.

Next step is to take a voltmeter to the chassis battery... just to verify voltage.

If all goes well this winter, I'll attest that the Li-BIM 225 is a well thought out device.

[RizeMaster]

Thanks for the update.

Consider that the "house" batteries (LiFePO4) DO NOT connect with the coach chassis battery (FLA) via the Li-BIM 225 solenoid without the engine running.

See, often incorrect to assume stuff... despite bold font and upper case use.

[Chateau_Nomad]

Well... More an "understanding through observation"; we ALL know what assumptions do to "u" and "me".

This from when being around the motorhome for a time I did not hear the tell-tale "thunk" of the relay. Even so, an occasional voltage check on the chassis battery will speak volumes.

[galOnTheGo]

thanks Chateau, that is good to know. Question I have - how does the stock charger installed with the fuse box etc that is fed from shorePower fit in? I know that upgrading to lithium requires an upgrade to the house charger to handle lithium. if it is not upgraded, the non-lithium charger will not charge the house batteries. I know this from experience. so how does the Li-Bim fit into that? next question is how does the solar power get to the Li-BIM? my solar connects to the chassis batteries.

just wondering here - does the power coming from shore power go through the house charger directly to the house batteries, or to the bim to charge house and chassis? if SP goes to the BIM, then it should charge both sets of batteries just fine. but in my experience and what I've been told by the charger manufacturer is that unless you change the charger, the house batteries will not be charged.
I have not changed my charger because it is a lot of wires and re-wiring to change that out. Please tell me if you know otherwise. the solar is doing just fine charging the house, but does not appear to charge the chassis. i did change my BIM to a Li_BIM, don't see a chassis charge, in fact see a drain in some cases, I suspect conditional on the state of the Li-BIM state. END of my wondering.

[16ACE27]

Originally Posted by galOnTheGo

thanks Chateau, that is good to know. Question I have - how does the stock charger installed with the fuse box etc that is fed from shorePower fit in? I know that upgrading to lithium requires an upgrade to the house charger to handle lithium. if it is not upgraded, the non-lithium charger will not charge the house batteries. I know this from experience. so how does the Li-Bim fit into that? next question is how does the solar power get to the Li-BIM? my solar connects to the chassis batteries.

just wondering here - does the power coming from shore power go through the house charger directly to the house batteries, or to the bim to charge house and chassis? if SP goes to the BIM, then it should charge both sets of batteries just fine. but in my experience and what I've been told by the charger manufacturer is that unless you change the charger, the house batteries will not be charged.
I have not changed my charger because it is a lot of wires and re-wiring to change that out. Please tell me if you know otherwise. the solar is doing just fine charging the house, but does not appear to charge the chassis. i did change my BIM to a Li_BIM, don't see a chassis charge, in fact see a drain in some cases, I suspect conditional on the state of the Li-BIM state. END of my wondering.

Realize that SP and the generator provide AC voltage to your RV. Most of your questions regard the DC distribution system. The connecting point is the converter/charger which connects directly to the house DC buss. The house DC buss allows the converter to power all house DC loads (lights, furnace, control power for the water heater, thermostat, Air Conditioner and propane fridge, etc).

The DC buss is also connected to your house batteries directly through the battery disconnect (USE/STORE or Master Power). So that has to be connected for the converter to charge your house batteries while on SP.

The house batteries and chassis battery are connected together by the Li-BIM. There is no connection to the converter by the Li-BIM unless the house battery disconnect is shut (allows connection). So the engine alternator can charge the house batteries through the Li-BIM regardless of the status of the house battery disconnect.

Now for Lithium house batteries:
Your standard Lead-Acid converter charger CAN charge your Lithium batteries, but not necessarily to 100% and even if they do get charged to 100%, the converter/charger will not maintain them at 100% once it shifts into float mode. In my experience the Lithium house batteries will be maintained anywhere between 55% - 70% by the converter,charger while on SP.

So if you're not up to swapping out the converter you can purchase a stand-alone Lithium battery charger at Amazon to top them up to 100% while on SP:

https://www.amazon.com/gp/product/B074X1QK2R/

[Chateau_Nomad]

When I did my lithium upgrade, I pretty much revamped the entire system. I currently have two 100Ah SOK batteries with Bluetooth and internal heaters, and will soon install an additional 206Ah SOK battery, for a total of 406Ah.

The battery bank connects to a Victron Power In busbar through a Blue Seas master battery disconnect. The busbar is the central connection point for all things 12 volt... solar charge controller, Li-BIM 225, Inverter/charger and feeds 12 volts to the DC load panel. With the exception of the 300 amp battery terminal fuse, I modified the busbar to accept Mega fuses of appropriate size.

The inverter/charger is a Sungoldpower 3000 watt pure sine wave.

For the 120 volt AC side, 30 amp shore power goes to the EMS, then to the transfer switch. The 4k generator is also wired to the transfer switch. Then the transfer switch goes to the AC input on the inverter/charger.

The inverter/charger has an integrated transfer switch, which is essentially a "pass through" for AC when connected to shore power or when the generator is running. In pass through mode, it's basically a battery charger - which I can configure the amperage it will allow to pass.

So the Li-BIM is just another 12 volt charging device which connects to the master busbar... just like the inverter/charger (when in charge mode) and 12 volts from the solar charge controller. It ALL connects to the DC busbar...

The battery bank can be completely disconnected via the battery switch. And I also installed a photovoltaic switch between the solar panels and charge controller to completely disconnect the solar panels if desired.

My power system bears little resemblance to the stock setup Thor installed.

P.S. I verified the chassis battery voltage today at 13.3 volts. So that confirms that the Li-BIM 225 is definitely supplying charge from the solar.

[galOnTheGo]

much thanks ACE for that, I understand all that, your description makes it very clear. and, I have an inverter / charger that when connected to SP I can turn on that will quickly charge the lithium house batteries, thanks for that item link, got it covered.

what i am not understanding is how a charge (from solar input, herein referred to as a trickle charge) is going to feed back to the BIM so the BIM can charge the chassis battery.
my solar is input to the house batteries, which are connected to the BIM, which connects to the chassis battery. how does a charge (from the solar) to the house get the BIM to supply that (solar) charge to the chassis?

[16ACE27]

Originally Posted by galOnTheGo

much thanks ACE for that, I understand all that, your description makes it very clear. and, I have an inverter / charger that when connected to SP I can turn on that will quickly charge the lithium house batteries, thanks for that item link, got it covered.

what i am not understanding is how a charge (from solar input, herein referred to as a trickle charge) is going to feed back to the BIM so the BIM can charge the chassis battery.
my solar is input to the house batteries, which are connected to the BIM, which connects to the chassis battery. how does a charge (from the solar) to the house get the BIM to supply that (solar) charge to the chassis?

Same way the charge from the converter or inverter/charger gets there. The solar charges the house battery bank. When the house battery voltage reaches the "triggering" voltage and the chassis batteries reach the low threshold the BIM connects the house battery bank to the chassis battery and it charges.

Look at the quote in post #8 above.

[Chateau_Nomad]

A cleaner wiring layout would be to have your solar controller connected to a 12 volt busbar. Your batteries are also connected to that busbar. AND your house battery terminal on the Li-BIM is connected to that same busbar.

The BIM technically is measuring voltage from the house batteries THROUGH the busbar.... and also measuring the chassis battery voltage via its direct connection to the chassis battery.

If your solar is providing current, that is taken into account in the measurement. If that measurement is higher than the chassis battery, the BIM connects.

It's not good practice to connect a spaghetti of cables directly to your house batteries... although some people do it. Multiple cables on one contact point have the potential to create resistance, not to mention making the entire wiring scheme more difficult. Basically it's the same reason it's bad practice (and likely against code) to wire multiple AC circuits to a common breaker.

[galOnTheGo]

wow, much thanks again Ace and Chateau, your contributions herein helped me understand the BIM and battery connections MUCH better. time for me to get out my multiMeter and check some numbers, that's what I call fun!

[Korey & Tana Jackson]

Chateau_Nomad,

Attached is a short clip demonstrating the chassis 12V system voltage and our LiBIM225 in action on our 2018 Vegas with lithium coach batteries. While this clip was taken tonight night, using shore power, it performs the same when using just the solar panels.

With the engine off:
I turned on the headlights, resulting in a draw on the chassis battery, and it drifts down from about 12.9 V to below 12.5V (roughly 80% SOC). The voltage at the coach batteries and converter is roughly 13.6V. When the LiBIM senses the chassis side is below 12.5V, AND there is a charging voltage on the coach side, it engages the internal solenoid so that the chassis battery system is charging from the coach system.

The result: the chassis battery is maintained from the coach system. which may be either (or even both) the coach batteries system charging from solar or the converter (assuming converter output is above about 13.4V).

https://photos.app.goo.gl/tSrrcqQf5YTNRxzH6