charging off the alternator

[reilym]

All,
We have a 2016 PW Lexor. It is all stock with 2 proprietary 100 Ah lithium batteries in the coach, an AGM chassis battery and a Sure Power 1315-200 one-way battery isolator. Before our last trip, I installed DC amp meters on both the cable going from the isolator to the coach batteries and the alternator to the chassis battery. What I observed when we started out was what I expected. About 35 amps going into the chassis and 80 amps going back to the partially depleted coach lithiums. The chassis current quickly settled down to a steady 15 amps for the rest of the trip. What I am puzzled about is that the current going to the coach batteries never went below 40 amps, even after the coach batteries showed 100%. That 40 amp reading continued during the entire 8 hour trip. The only appliance we were operating (off the battery) was the Dometic fridge which is rated at 15 amps and turning the fridge off did not change the 40 amp reading. So, it seems that the alternator is working harder than it needs to. Shouldn't the alternator current going to the coach batteries drop to near zero once the coach batteries are full? Where are all those electrons going? It's hard to get any detailed information from PW on the lithium batteries, other than they are equipped with a BMS that protects the batteries from various things including over charging or going too low.

Appreciate thoughts on this.

 

[booster]

All,
We have a 2016 PW Lexor. It is all stock with 2 proprietary 100 Ah lithium batteries in the coach, an AGM chassis battery and a Sure Power 1315-200 one-way battery isolator. Before our last trip, I installed DC amp meters on both the cable going from the isolator to the coach batteries and the alternator to the chassis battery. What I observed when we started out was what I expected. About 35 amps going into the chassis and 80 amps going back to the partially depleted coach lithiums. The chassis current quickly settled down to a steady 15 amps for the rest of the trip. What I am puzzled about is that the current going to the coach batteries never went below 40 amps, even after the coach batteries showed 100%. That 40 amp reading continued during the entire 8 hour trip. The only appliance we were operating (off the battery) was the Dometic fridge which is rated at 15 amps and turning the fridge off did not change the 40 amp reading. So, it seems that the alternator is working harder than it needs to. Shouldn't the alternator current going to the coach batteries drop to near zero once the coach batteries are full? Where are all those electrons going? It's hard to get any detailed information from PW on the lithium batteries, other than they are equipped with a BMS that protects the batteries from various things including over charging or going too low.

Appreciate thoughts on this.

Are you sure it is a 1315-200 and not a 1314-200 as the 1315 is shown as the bidirectional separator? It is not commonly defined isolator as they would be single direction diode units.


The big question would be what is telling you the batteries are actually 100% full? If it is a voltage triggered indicator it could be way off of actual battery state of charge.


But this doesn't make it any easier to understand the 40 amps lasting that long as 8 hours would fill the batteries in that time. It also doesn't explain why turning off the frig doesn't change the reading on the ammeter.



What kind of ammeters are you using? It is possible the ammeter is getting some kind of reveres voltage on the ground or something, so very curious, indeed.


You may want to swap the inputs on the meters and see what happens to test the meters. Also take a look to see if the starting and coach batteries are on the same 12v ground circuit, which would be the chassis normally. PW may have run isolated ground on the lithium setup, but we haven't heard of that before.


Do your ammeters read direction of the amperage as a plus or minus? That would tell you if you have the meter actually reading backward current under some conditions.

 

[markopolo-ClassB]

Just some thoughts. (edit: Booster covered most of it, but figured I'd post what I typed anyway)

Could 15A be double counted? My assumption here is that power from the alternator goes to a distribution block.

A steady 15A to run the Promaster doesn't seem likely as I'd expect some variance. Brake lights, engine fan etc., are not always on.

The device you used doesn't display a negative sign according to Amazon comments. It instead shows a dot. Did you happen to notice a dot at the end?

 

[jakegw2]

I just installed 2 100A Battleborn LiPo batteries last weekend and have been testing them. When I spoke to Battleborn they actually told me that I would have the exact problem you just described - e.g. the alternator charges the batteries to a certain point (something less than 100%) but they keep accepting a high current input without gaining any additional charge.

This baffles me. Where is that power going? Is it just converting to waste heat in the batteries? Doesn't that cook them? The person I spoke to seemed to think it was no big deal for the batteries but potentially problematic for the alternator.

After my install this is something I tested immediately and found that... with my Promaster the charge current trickled down to near zero once the batteries were charged. Hmm... Why the different behavior from what I was told to expect?

Here are a few theories I have:
- Alternator charge voltage matters: My Promaster charges at about 14.4v when running. This might be higher than most vehicles and could be enough to get the LiPo batteries to near full charge, which would allow them to stop accepting current.

- Solar: Perhaps my solar panels (I have 340W) were boosting the voltage enough that it got the LiPo battery voltage above the alternator voltage so that no current continued to flow. In the absence of a solar boost perhaps I would have seen the same issue.

You could try charging your batteries to 100% on the shore power charger and then turning the van on to see if you still get the power draw. If the solar theory is correct then you shouldn't. The problem would only happen when you try to recharge the batteries exclusively from driving.

It might also be worth checking to see what the alternator voltage is when the LiPo batteries are disconnected.

 

[markopolo-ClassB]

................. When I spoke to Battleborn they actually told me ...................... the alternator charges the batteries to a certain point (something less than 100%) but they keep accepting a high current input without gaining any additional charge.............

You were given incorrect information.

................After my install this is something I tested immediately and found that... with my Promaster the charge current trickled down to near zero once the batteries were charged................. .

That's what you should expect. At any given charging voltage, charge current will eventually go to near zero if held at that given voltage long enough. The BMS will consume some current but it might not even be observable on some equipment.

 

[reilym]

Booster,
You are right, it is the 1314-200, unidirectional and it is a separator, not an isolator. The hall effect sensors have directional arrows and it seems that I got them installed correctly the first time, since there is no "dot" on the display to indicate negative current. These are cheap devices and I would not expect them to be accurate, but they do seem to work in general. When I disconnect the alternator and solar charging by turning off the high current switch, the coach current goes to almost zero. I also did not account for the solar panels which were active while I was driving. I will check the voltage at the isolator with the alternator running and report back, but my recollection is it's south of 14.4, something like 13.8. Still, it seems that your observations with the BattleBorns are more like what I was expecting.

 

[booster]

Booster,
You are right, it is the 1314-200, unidirectional and it is a separator, not an isolator. The hall effect sensors have directional arrows and it seems that I got them installed correctly the first time, since there is no "dot" on the display to indicate negative current. These are cheap devices and I would not expect them to be accurate, but they do seem to work in general. When I disconnect the alternator and solar charging by turning off the high current switch, the coach current goes to almost zero. I also did not account for the solar panels which were active while I was driving. I will check the voltage at the isolator with the alternator running and report back, but my recollection is it's south of 14.4, something like 13.8. Still, it seems that your observations with the BattleBorns are more like what I was expecting.

I would have to really doubt that current is really going to the coach are that is 500 watts and you should be seeing something getting really hot from it, which I think would be very noticeable.



jakegw2 had the battleborn comments, we have AGM in our Roadtrek.

 

[markopolo-ClassB]

Just a note:

The 1314-200 would be described as single sense and the 1315-200 as dual sense. Nether are directional once latched.

Both latch at 13.2V and don't disconnect until voltage drops to 12.8V. There's probably something like a 12W draw when latched. If latched, the lithium battery will supply that 12W + whatever the chassis battery takes until the lithium battery falls below 12.8V (or is disconnected).

Once unlatched, the 1314-200 won't latch again until the engine is started or if some other charge source is present on the chassis battery.

Both the 1314-200 and the 1315-200 are not really intended for use with lithium batteries. They're not the best choice to use with solar either as 12W or so is wasted.

 

[markopolo-ClassB]

You should see reverse current on the coach battery cable ammeter if the 1314-200 is latched and engine is off and the coach batteries and solar are on.

If you did the calibration procedure with solar output or lithium battery power going to and through the 1314-200 then that would create a measuring error.

 

[rlum-JAY]

Hi: I have a 2016 Lexor TS like you. Same charge set up with unidirectional separator. Just replaced recently. The separator is activated when the chassis battery is 13.4 to 13.6 volts. Once this happens all batteries will try to equalize.

I upgraded to 2 additional 100ah lithiums so total of 400ah lithiums. I use a Victron 712 monitor to check charging and discharging. After each trip, my house batteries at 13.9 to 14.0 volts or 100 percent. The separator stays active until the chassis battery voltage drops below 13.4 volts. So when I go into storage my lithiums lose a bit of charge. This may be what is happening in your situation. The separator is connecting the house battery to chassis to allow draw down. You can disconnect your separator. There is a small black wire behind it. I think 18 gauge? If you disconnect this wire, the separator will be disabled. Now when driving see if your house batteries are still receiving a charge or 40 amps? Also how old is your chassis battery. It may not be holding a charge well enough so keeps trying to equalize with lithiums?

 

[reilym]

Just a note:
The 1314-200 would be described as single sense and the 1315-200 as dual sense. Nether are directional once latched.

That makes sense.

Just a note:
Both the 1314-200 and the 1315-200 are not really intended for use with lithium batteries. They're not the best choice to use with solar either as 12W or so is wasted.

That is the first I heard this, but it also makes sense. 2016 was the year that PW transitioned from AGM to LiFePO and I imagine that the system is not fully optimized for lithium. I have yet to find anyone a PW that is able or willing to describe the details of their coach power deployment. What would be a better mechanism for isolating the coach and LiFePO chassis batteries while maintaining automatic alternator charging?

 

[reilym]

Hi: I have a 2016 Lexor TS like you. Same charge set up with unidirectional separator. Just replaced recently.

Mine is on it's second separator too.

I upgraded to 2 additional 100ah lithiums so total of 400ah lithiums. I use a Victron 712 monitor to check charging and discharging. ... There is a small black wire behind it. I think 18 gauge? If you disconnect this wire, the separator will be disabled. Now when driving see if your house batteries are still receiving a charge or 40 amps? Also how old is your chassis battery. It may not be holding a charge well enough so keeps trying to equalize with lithiums?

I also have installed the Victron to monitor charge state. I did not know that I could interrupt the black wire and disable the separator. I will definitely do that and some other testing based on the feedback today and report back. Maybe putting a switch into that black wire so it can be controlled from the cab. I am uneasy with seeing 40 amps all the time. I'm no EE, but something must be suffering other than the alternator.

 

[markopolo-ClassB]

That makes sense.

That is the first I heard this, but it also makes sense. 2016 was the year that PW transitioned from AGM to LiFePO and I imagine that the system is not fully optimized for lithium. I have yet to find anyone a PW that is able or willing to describe the details of their coach power deployment. What would be a better mechanism for isolating the coach and LiFePO chassis batteries while maintaining automatic alternator charging?

A DC-DC charge controller seems to be a popular choice now. They limit the current from the alternator and let you choose the charge profile. I chose that method for a small lithium battery as I wanted to limit the current available to it while supplying a specific voltage.

Victron's Argofet 200-2 might be an option worth considering if you don't want a DC-DC charge controller.

 

[booster]

A DC-DC charge controller seems to be a popular choice now. They limit the current from the alternator and let you choose the charge profile. I chose that method for a small lithium battery as I wanted to limit the current available to it while supplying a specific voltage.

Victron's Argofet 200-2 might be an option worth considering if you don't want a DC-DC charge controller.

Totally agree, the whole deal with charging off the engine these days is kind of running in circles, I think, and with bigger battery banks and batteries that will accept more current than in older systems, the entire charging system takes a beating. The mentions of single alternators failing seem to be increasing as was kind of expected as this type of use got more common. Stock alternators just don't like running at 50%+ output all the time and will often fail early.



When the bigger bank, lithium batteries, and such first hit the market many of the systems included a second, standalone, alternator to run them, but now there are more "drop in" battery systems and OEM like Pleasure-way who just use high acceptance, different voltage lithium, systems on top of old school charging stuff, using the stock OEM alternator.


I think the marine market figured this out a long time ago, as the marine rated alternators have tiny output for their size compared to automotive ones, but are mostly rated for 100% continuous output so they can't hurt themselves as easily.


For a pure lithium system, you could probably get by with a current limiting charge relay and a cutoff triggered by the "full" signal from a Victron battery monitor. On an AGM system where float is desirable the 12v to 12v charger is a good idea, or use a standalone second alternator with a smart regulator on it plus the Victron cutoff setup.


In any case, I would get rid of the coil type, high current draw Sure Power separators that fail early and waste energy besides. There are plenty of bistable relays and separators out there that are much better.

 

[rlum-JAY]

I placed a water proof marine switch to disconnect my separator. As soon as I drive up and am ready to store for weeks or months. I hit the disconnect switch. I check my Victron 712 blue tooth. No amps going out. I can see my lithium bank voltage stays higher because no longer connected to chassis battery. Before doing this, my lithiums would draw down from the chassis battery. Not a big deal but now my lithiums can stay almost fully charged during the winter months.

 

[booster]

I placed a water proof marine switch to disconnect my separator. As soon as I drive up and am ready to store for weeks or months. I hit the disconnect switch. I check my Victron 712 blue tooth. No amps going out. I can see my lithium bank voltage stays higher because no longer connected to chassis battery. Before doing this, my lithiums would draw down from the chassis battery. Not a big deal but now my lithiums can stay almost fully charged during the winter months.

You must not have solar either as that will also hold the separator in when parked unless you turn it off and will also use up a lot of the solar to run the coil if you are topping the starting battery with the solar in storage or a long stay. After we had one Surepower fail and the second run so hot all the time and eat up too much solar, we got rid of it for a no power use even when closed or open bistable Blue Sea relay.

 

[hbn7hj]

Just an opinion but a DC to DC charge controller is the best option. It is mentioned toward the end of the following thread.

https://www.classbforum.com/forums/f23/2003-roadtrek-hybrid-battery-system-8526.html

 

[rlum-JAY]

You must not have solar either as that will also hold the separator in when parked unless you turn it off and will also use up a lot of the solar to run the coil if you are topping the starting battery with the solar in storage or a long stay. After we had one Surepower fail and the second run so hot all the time and eat up too much solar, we got rid of it for a no power use even when closed or open bistable Blue Sea relay.

Hi: I have solar panels(190watt) connected to the house batteries. I use a portable solar panel to keep the chassis battery topped off. I store outside in Southern California so lots of sun here. Solar kept the chassis battery above 13.4 volts. Separator stayed closed. Equalizing constantly with house lithium. Finally figured it out and made the switch as a disconnect. Now can charge chassis battery with the separator switch open. No more draining of house lithiums. Works very well for me.

 

[booster]

Just an opinion but a DC to DC charge controller is the best option. It is mentioned toward the end of the following thread.

https://www.classbforum.com/forums/f23/2003-roadtrek-hybrid-battery-system-8526.html

I would agree in most cases, but the problem can come when there is a big battery bank that can accept a lot of current. I think the biggest 12 to 12 right now is the 120 amp Sterling(?). The Nations alternators are able to do about 165 amps average output, but normally heat cycling so higher and lower than that back and forth so you need to handle about 200 amps. What we really need is an updated version of the Charles/Ample Power external regulator that was programmable for profile, could be set to limit current to two different settings, and could be stage forced while in use. That would cover nearly every shortcoming of the alternator charging from a standalone add on alternator.

 

[rowiebowie]

I just installed 2 100A Battleborn LiPo batteries last weekend and have been testing them. When I spoke to Battleborn they actually told me that I would have the exact problem you just described - e.g. the alternator charges the batteries to a certain point (something less than 100%) but they keep accepting a high current input without gaining any additional charge.

This baffles me. Where is that power going? Is it just converting to waste heat in the batteries? Doesn't that cook them? The person I spoke to seemed to think it was no big deal for the batteries but potentially problematic for the alternator.

I'm only adressing only the above portion of your post.

My recent Renogy lithium install does continue to charge at full rate for an extended period of time past the point of 100% on my battery state-of-charge monitor. It doesn't do this for hours, but I'd say I've observed this charge to continue for 30+ minutes.

When this charging occurs, the battery voltage sits at 13.6 volts for about 95% of this time before it quickly ramps up to 13.7, 13.8, etc. rising ever faster until voltage momentarily hits 14.6 volts. Then charging abruptly stops and voltage settles at 13.3-13.4 volts after another 5-10 minutes.

As I understand it, this is normal and part of the lithium charging profile.