DC-DC charger for lithium batteries

[waterskier_1]

I've reviewed this product's predecessor.  I discussed the apparent failing with the engineers.  I was told that that previous version was not a "charger" and only "combined" the battery banks.  I believe there have been some attempts to improve with this release, but it still need much improvement.  

A BIM is a "Battery Isolation Manager".  Monaco use their Solid State Isolator in the early days (late '70's into the early 90's), then went with the IRD (Isolator Relay Delay) and BIRD (a Bi-Directional IRD).  The delay comes from the fact that Monaco didn't want the batteries immediately connected right after engine start, but want a delay to allow the alternator to replenish the chassis battery and engine to "warm up".  Then it would connect the two banks to the alternator.  They would stay connected together as long as long as the engine was running.  The alternator is not a smart charger.  It only has a Voltage Regulator, that is preset to 14.2 - 14.4 volts.  It will do all it can to maintain that voltage.  If the load is too great, the alternator output (voltage) wil decrease.  This is usually only seen after dry camping and the coach batteries are very depleted.  Other than that case, the alternator output is 14.2 - 14.4 volts constantly, it doesn't know or care about the State of Charge (SOC) of the batteries.  So, if you are taking an 8 hour trip, it's possible that your house batteries (and the chassis batteries) are being charged for 8 hours at 14.4 volts.  This is not good for any battery's life, but Lead Acid, particularly Flooded Lead Acid (FLA), can tolerate it.  AGM don't fair quite so good, but most won't notice the difference.  Now enter the Lithium, specifically Lithium Lead Phosphate (LiFePO4) batteries.  There are two problems.  One is that they HATE being held at a high voltage once they are charged.  Second is they can accept a higher rate of charge by at least 10 time than what Lead Acid batteries can.  This has to do with a significantly lower internal resistance.  I'll leave it at that for this response.  If you desire more info on this, let me know.  Based on the above, users and manufacturers recognized the need to address these issues.  When these batteries first came out, and no other provisions were made, owners experienced failures - either the isolator components because they were not designed to handle the much higher current (mostly the solid state devices) or the alternators were destroyed, attempting to supply 10 times the current they were designed for.  So, some enterprising companies are now attempting to respond to these problems. 

As I mentioned above, I evaluated the previous version of this device.  I found the description lacking, from an engineering/design point of view.  So I called and talked to engineers.  That device, was designed to connect the batteries when conditions (one or more batteries were being charged, the voltage was less than 15.5 volts on both banks and the house battery was 0.2 volts or more below chassis battery.  As I recall, that version was not Bi-Directional, but in any case, the problems are really only when the alternator is the charging source.  The Inverter/Charger is a Smart Charger, and doesn't have those problems.  Once connected, it would remain connected for 15 minutes.  Then it would wait 15 minutes and reevaluate the conditions to determine if it would connect again for another 15 minutes.  It would continue this cycle until the engine was shut off, or the house battery came within 0.2 volts of the chassis, or either of the batteries exceeded 15.5 volts.

I had two primary concerns.  The first being how the 15 minutes was determined.  They didn't know, but guess that the alternator would not overheat and destroy itself within those 15 minutes.  I'm not convinced.  My second concern was charging profile.  They admitted there was no charge profile, it was not a smart charger, other than it would disconnect the house batteries within 15 minutes of them becoming within 0.2 volts of the chassis battery (bassically greater than 14.0 volts).

Now on to this new one.  I have has several clients ask about it.  I have not done a review other than to read the promotional brochure (they don't publish any specifications, and I haven't called to talk to anyone).  The new one is a bit more vague, but it clearly identifies that it is Bi-Directional (will allow connecting the chassis batteries when the inverter/charger is working.  It claims to "monitor the voltage of both .... over long periods of time", but I don't know what the voltage will tell them, nor how stores and uses the "over long periods of time" data.  It also states that if "the charging system is drastically overburdened" the batteries will be isolated.  But it doesn't define how it senses this and what the parameters (i.e., > 100 Amps) defines "overburdened".  I'm sure this is response to the previous version not taking into consideration any burden, but "hoping" that it wouldn't destroy anything during the 15 minute connection period.  They also state "if the Li-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".  That's some word salad there.  My take away is that they no longer use a predefined guess of 15 minutes, but as long as it's not overburdened, it will keep the batteries connected.  I don't think it can really tell if there is charging going on.  It doesn't have any control of voltage or current.  The alternator still sets the voltage, and the batteries (and any loads connected to them - headlights, refrigerators, etc - sets the current.  It can open the house battery connection and stop all charging - that's it.  Now, after an hour, it will isolate the batteries to prevent overcharging (how did the one hour come into play?  Likely another guess), and will only reconnect "if one of the batteries drops to approximately 80% charge".  Based upon the connections to the device, they have no way of determining the State Of Charge.  They can only measure the voltage of the batteries under some load, which they don't know.  I suspect they have just programmed a guestimate voltage in to say the batteries are charged.  

This version has addressed, but not satisfactorily, the concerns I related to the engineer relative to the previous version.  It still isn't a smart charger.  It can't determine the state of charge or apply an appropriate charge profile (Bulk, Absorption, Float).  I don't know how it knows and handles "overburdened" alternator current draw.  But I will also state that I don't know of a device similar that does the job. 

What I have done is to completely (and permanently) isolated the chassis system and alternator charging for the house system and the inverter/charger.  The alternator only charges the chassis battery and only works when the main engine is running (obviously).  It does not charge the house batteries.  The house batteries are charged by the inverter/charger when or shore power, or the generator.  This does not directly charge the chassis battery.  I have installed, but have not found the need to connect, a stand only battery maintainer that plugs into the block heater which could be enabled to charge the chassis battery when the inverter/charger is powered.  I also have 1400 Watts of solar on the roof.  I used to original Monaco 100 Watt panel just for the chassis battery through its own MPPT controller.  This was a result of not finding any panels that could be use in combination with that panel, so deployed it to the chassis battery instead of simply removing it.  The other 1300 Watts are used to charge/maintain the house batteries though two MPPT controllers.  The MPPT controllers are smart chargers that can be programmed to Bulk, Absorption, and Float, just like the inverter/charger.  I've only had a couple times when the solar didn't keep up.  One time was a snow storm last year where we got over 8" of snow and it didn't get above freezing for a week and I was out of town so I couldn't plug it in.  The other time was when the repair (body) shop didn't turn off the battery disconnect switches and it was inside for over 10 days.  In both cases, the engine generator started up and charged up the house batteries.  The chassis battery didn't discharge in that short period of time. 

Sorry about the long post but I've had a lot of people bring this to my attention, and I have discouraged them from purchasing.  After understanding there concerns and requirements, I've provided alternative solutions.

  -Rick N.

[Capt. Tango]

3 hours ago, waterskier_1 said:

I've reviewed this product's predecessor.  I discussed the apparent failing with the engineers.  I was told that that previous version was not a "charger" and only "combined" the battery banks.  I believe there have been some attempts to improve with this release, but it still need much improvement.  

A BIM is a "Battery Isolation Manager".  Monaco use their Solid State Isolator in the early days (late '70's into the early 90's), then went with the IRD (Isolator Relay Delay) and BIRD (a Bi-Directional IRD).  The delay comes from the fact that Monaco didn't want the batteries immediately connected right after engine start, but want a delay to allow the alternator to replenish the chassis battery and engine to "warm up".  Then it would connect the two banks to the alternator.  They would stay connected together as long as long as the engine was running.  The alternator is not a smart charger.  It only has a Voltage Regulator, that is preset to 14.2 - 14.4 volts.  It will do all it can to maintain that voltage.  If the load is too great, the alternator output (voltage) wil decrease.  This is usually only seen after dry camping and the coach batteries are very depleted.  Other than that case, the alternator output is 14.2 - 14.4 volts constantly, it doesn't know or care about the State of Charge (SOC) of the batteries.  So, if you are taking an 8 hour trip, it's possible that your house batteries (and the chassis batteries) are being charged for 8 hours at 14.4 volts.  This is not good for any battery's life, but Lead Acid, particularly Flooded Lead Acid (FLA), can tolerate it.  AGM don't fair quite so good, but most won't notice the difference.  Now enter the Lithium, specifically Lithium Lead Phosphate (LiFePO4) batteries.  There are two problems.  One is that they HATE being held at a high voltage once they are charged.  Second is they can accept a higher rate of charge by at least 10 time than what Lead Acid batteries can.  This has to do with a significantly lower internal resistance.  I'll leave it at that for this response.  If you desire more info on this, let me know.  Based on the above, users and manufacturers recognized the need to address these issues.  When these batteries first came out, and no other provisions were made, owners experienced failures - either the isolator components because they were not designed to handle the much higher current (mostly the solid state devices) or the alternators were destroyed, attempting to supply 10 times the current they were designed for.  So, some enterprising companies are now attempting to respond to these problems. 

As I mentioned above, I evaluated the previous version of this device.  I found the description lacking, from an engineering/design point of view.  So I called and talked to engineers.  That device, was designed to connect the batteries when conditions (one or more batteries were being charged, the voltage was less than 15.5 volts on both banks and the house battery was 0.2 volts or more below chassis battery.  As I recall, that version was not Bi-Directional, but in any case, the problems are really only when the alternator is the charging source.  The Inverter/Charger is a Smart Charger, and doesn't have those problems.  Once connected, it would remain connected for 15 minutes.  Then it would wait 15 minutes and reevaluate the conditions to determine if it would connect again for another 15 minutes.  It would continue this cycle until the engine was shut off, or the house battery came within 0.2 volts of the chassis, or either of the batteries exceeded 15.5 volts.

I had two primary concerns.  The first being how the 15 minutes was determined.  They didn't know, but guess that the alternator would not overheat and destroy itself within those 15 minutes.  I'm not convinced.  My second concern was charging profile.  They admitted there was no charge profile, it was not a smart charger, other than it would disconnect the house batteries within 15 minutes of them becoming within 0.2 volts of the chassis battery (bassically greater than 14.0 volts).

Now on to this new one.  I have has several clients ask about it.  I have not done a review other than to read the promotional brochure (they don't publish any specifications, and I haven't called to talk to anyone).  The new one is a bit more vague, but it clearly identifies that it is Bi-Directional (will allow connecting the chassis batteries when the inverter/charger is working.  It claims to "monitor the voltage of both .... over long periods of time", but I don't know what the voltage will tell them, nor how stores and uses the "over long periods of time" data.  It also states that if "the charging system is drastically overburdened" the batteries will be isolated.  But it doesn't define how it senses this and what the parameters (i.e., > 100 Amps) defines "overburdened".  I'm sure this is response to the previous version not taking into consideration any burden, but "hoping" that it wouldn't destroy anything during the 15 minute connection period.  They also state "if the Li-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".  That's some word salad there.  My take away is that they no longer use a predefined guess of 15 minutes, but as long as it's not overburdened, it will keep the batteries connected.  I don't think it can really tell if there is charging going on.  It doesn't have any control of voltage or current.  The alternator still sets the voltage, and the batteries (and any loads connected to them - headlights, refrigerators, etc - sets the current.  It can open the house battery connection and stop all charging - that's it.  Now, after an hour, it will isolate the batteries to prevent overcharging (how did the one hour come into play?  Likely another guess), and will only reconnect "if one of the batteries drops to approximately 80% charge".  Based upon the connections to the device, they have no way of determining the State Of Charge.  They can only measure the voltage of the batteries under some load, which they don't know.  I suspect they have just programmed a guestimate voltage in to say the batteries are charged.  

This version has addressed, but not satisfactorily, the concerns I related to the engineer relative to the previous version.  It still isn't a smart charger.  It can't determine the state of charge or apply an appropriate charge profile (Bulk, Absorption, Float).  I don't know how it knows and handles "overburdened" alternator current draw.  But I will also state that I don't know of a device similar that does the job. 

What I have done is to completely (and permanently) isolated the chassis system and alternator charging for the house system and the inverter/charger.  The alternator only charges the chassis battery and only works when the main engine is running (obviously).  It does not charge the house batteries.  The house batteries are charged by the inverter/charger when or shore power, or the generator.  This does not directly charge the chassis battery.  I have installed, but have not found the need to connect, a stand only battery maintainer that plugs into the block heater which could be enabled to charge the chassis battery when the inverter/charger is powered.  I also have 1400 Watts of solar on the roof.  I used to original Monaco 100 Watt panel just for the chassis battery through its own MPPT controller.  This was a result of not finding any panels that could be use in combination with that panel, so deployed it to the chassis battery instead of simply removing it.  The other 1300 Watts are used to charge/maintain the house batteries though two MPPT controllers.  The MPPT controllers are smart chargers that can be programmed to Bulk, Absorption, and Float, just like the inverter/charger.  I've only had a couple times when the solar didn't keep up.  One time was a snow storm last year where we got over 8" of snow and it didn't get above freezing for a week and I was out of town so I couldn't plug it in.  The other time was when the repair (body) shop didn't turn off the battery disconnect switches and it was inside for over 10 days.  In both cases, the engine generator started up and charged up the house batteries.  The chassis battery didn't discharge in that short period of time. 

Sorry about the long post but I've had a lot of people bring this to my attention, and I have discouraged them from purchasing.  After understanding there concerns and requirements, I've provided alternative solutions.

  -Rick N.

Thanks for the explanation, always better to have advice rather than learn by error.

[wamcneil]

On 11/13/2023 at 8:45 AM, Jim McGarvie said:

I have installed three 12V 100AH LiFePO4 batteries. Initially I just disconnected the relay between the engine and house batteries to avoid the potential alternator issues of charging the lithium batteries while driving. I have solar, so depending upon available sunlight I might get by this way, but I am considering installing a DC-DC charger. What is everyone's favorite? I would just as soon not need to run a wire to the alternator if possible, simply replace the solenoid with the charger.

Wow! Lots of discussion in this thread. I didn't read it all... 🤐

To answer your question, I have a Victron Orion-TR DC-DC Converter 12 VDC to 12 VDC 18AMP Isolated ORI121222110 from House>>Chassis.

I'm not trying to charge the house lithium batteries from the alternator while moving, just keep the chassis batteries floated while parked. I figure if I really need to charge the house batteries while moving, I'll start the generator.

My first attempt was to put a small noco battery charger on the chassis battery, plugged into the block heater outlet. But that charger was a little too smart and would occasionally go into an error state and let my chassis battery go dead. The victron has been 100% reliable.

[Jim McGarvie]

18 minutes ago, wamcneil said:

Wow! Lots of discussion in this thread. I didn't read it all... 🤐

To answer your question, I have a Victron Orion-TR DC-DC Converter 12 VDC to 12 VDC 18AMP Isolated ORI121222110 from House>>Chassis.

I'm not trying to charge the house lithium batteries from the alternator while moving, just keep the chassis batteries floated while parked. I figure if I really need to charge the house batteries while moving, I'll start the generator.

My first attempt was to put a small noco battery charger on the chassis battery, plugged into the block heater outlet. But that charger was a little too smart and would occasionally go into an error state and let my chassis battery go dead. The victron has been 100% reliable.

Thanks Walter.