Do we add 2 additional Solar panels or not

[jakegw2]

I disagree. I have installed an aftermarket system that is very similar to what the poster describes in my Promaster-based "B+." I was quite concerned about all of the many issues raised about LiFePO4 batteries and was planning to install a DC-DC charger on mine. After getting it up and running without the DC-DC charger and doing quite a bit of testing I have concluded that for <300A LiFePO4 capacity it is not needed. The alternator responds almost fully within the needs of the battery bank, lacking only the ability to provide a full charge to balance the cells (which the solar controller can provide in a short period of time once the batteries are almost fully charged by the alternator).

A lot of the worry about LiFePo4 batteries boils down to trying to optimizing them to work for 15 years instead of just 10 - both timeframes are well outside the ownership period for most RV owners and not really worth the extra investment. They don't need everything perfect, they are more robust then people give them credit for.

[jakegw2]

I have a system that is very similar to yours (that I installed aftermarket in my Promaster based "B+") except with 370W of solar and an 80A charger instead of your 45A unit.

Having used it now for a while I have concluded that I don't need all the solar that I installed. The big reason is because the alternator (and generator) charge the batteries much faster and even when camping in one spot I almost never fail to drive for at least some distance each day. The only real value the solar offers me with my use pattern is keeping the batteries charged when I am not using the RV. This could have been easily accomplished with a 50W panel.

[booster]

Originally Posted by jakegw2

I disagree. I have installed an aftermarket system that is very similar to what the poster describes in my Promaster-based "B+." I was quite concerned about all of the many issues raised about LiFePO4 batteries and was planning to install a DC-DC charger on mine. After getting it up and running without the DC-DC charger and doing quite a bit of testing I have concluded that for <300A LiFePO4 capacity it is not needed. The alternator responds almost fully within the needs of the battery bank, lacking only the ability to provide a full charge to balance the cells (which the solar controller can provide in a short period of time once the batteries are almost fully charged by the alternator).

A lot of the worry about LiFePo4 batteries boils down to trying to optimizing them to work for 15 years instead of just 10 - both timeframes are well outside the ownership period for most RV owners and not really worth the extra investment. They don't need everything perfect, they are more robust then people give them credit for.

My concerns are more about the stock alternator running at too high an output for too long in relation to the B to B charger. How many amps do your batteries take when fairly low, and how big is the alternator? If the manual for OP's rig is correct, it has twin 150 amp fuses as the only limit on alternator charging, which may be an issue depending on how much the batteries accept. No doubt, from a voltage standpoint, the alternator would not be an issue, as long as it survives longer term. Best way to tell is to check the temp of the alternator at the diode area and/or laminations. Some say that 225* F should be max, others will say a bit higher, but if it gets near 250* it is very likely going to be shortening the life if it does that for repeated cycles. The Balmar remote regulators turn down the output at about 220* to not go higher that, and a 280 amp high output alternator (Nations/DC Power Eng) will net about 165 amps average over an hours time running hot.

[markopolo]

Jake - let us know how you are taking your current measurements and also where in the system you take them.

When you say you see 120A out of your alternator for example was that measurement taken at the lithium batteries or before the isolating device?

[jakegw2]

Booster -

This is what I am seeing on my Promaster with a 220A alternator:
- Initial charge rate at start up (as measured by the BMS at the battery) is 120A
- Charge rate slowly falls until it levels off at about 70A where it stays until the batteries are full. The slow decline strongly suggests some internal regulation that is bringing the output down. My guess (and it is just a guess, but an educated one) is that the internal regulation is keeping the output to a alternator-safe level. 70A represents about 38% of the 185A output that the alternator produces when hot (200 degrees) at highway cruising RPM (engine ~2500, alt ~7000 w/ 2.9:1 ratio). I feel this is probably a safe continuous output level even when adding in a reasonable buffer for the chassis load.

I really like your suggestion of looking at the temperature. I have a non-contact thermometer, so the next time I take it out and put it under load for a while I will try taking a temp measurement. It will be pretty easy because the alternator is easy to get to at the bottom of the engine.

Markopolo - My isolation device is a solenoid that is closed when the engine is running and open when the engine is off. I have two manual override switches installed that let me open it when the engine is running (if I ever need to protect the alternator from running too long - I have never ended up using this) or temporarily close it when the engine is off (as a battery boost for starting). I also have a dual-solar charge controller that charges the house and chassis batteries separately with their respective charge profiles (LiFePo4 and AGM).

[markopolo]

Originally Posted by jakegw2

...........
- Initial charge rate at start up (as measured by the BMS at the battery) is 120A
- Charge rate slowly falls until it levels off at about 70A ...........

So the Battle Born BMS shows current?



What voltage do you see at 120A and what voltage do you see at 70A?

[booster]

Originally Posted by jakegw2

Booster -

This is what I am seeing on my Promaster with a 220A alternator:
- Initial charge rate at start up (as measured by the BMS at the battery) is 120A
- Charge rate slowly falls until it levels off at about 70A where it stays until the batteries are full. The slow decline strongly suggests some internal regulation that is bringing the output down. My guess (and it is just a guess, but an educated one) is that the internal regulation is keeping the output to a alternator-safe level. 70A represents about 38% of the 185A output that the alternator produces when hot (200 degrees) at highway cruising RPM (engine ~2500, alt ~7000 w/ 2.9:1 ratio). I feel this is probably a safe continuous output level even when adding in a reasonable buffer for the chassis load.

I really like your suggestion of looking at the temperature. I have a non-contact thermometer, so the next time I take it out and put it under load for a while I will try taking a temp measurement. It will be pretty easy because the alternator is easy to get to at the bottom of the engine.

Markopolo - My isolation device is a solenoid that is closed when the engine is running and open when the engine is off. I have two manual override switches installed that let me open it when the engine is running (if I ever need to protect the alternator from running too long - I have never ended up using this) or temporarily close it when the engine is off (as a battery boost for starting). I also have a dual-solar charge controller that charges the house and chassis batteries separately with their respective charge profiles (LiFePo4 and AGM).

Very interesting on the alternator outputs. The 120 amps at probably high idle at startup sounds pretty normal for a 220a alternator.


What conditions did you have to read the 185 amps hot at driving speed? The 185 would also seem typical for an alternator running at high temp and would normally be considered way too much for normal OEM style alternator, albeit a good one because I think the use Denso.


Now concerning the tapering to 70 amps. Did that happen at idle or is it also at driving speed? It would be interesting to watch what is happening during the tapering in relation to temp and and field voltage. The 38% output is in the range of safe to run continuous in most cases and would probably give a case temp at the laminations of maybe 220*.



Do you happen to know if the alternator is running on the PCM or internal regulator? Most now are to the PCM and many are doing things beyond just checking temp to control output for fuel savings and such.


Temps checks as it tapers the output will be very interesting to see if they track each other. The internal regulators protections are usually pretty crude, I think. The Denso regulator in a 250 amp DC Power alternator didn't start to reduce output until 250*, which is just too hot for continuous output.



How fast they start to taper can have a big effect on how much wire size is needed and how much recovery you can get to the coach in a short time. We have 530 amps of alternator capacity and we can run close to 300 amps for about 20 minutes before the temps get to warm at idle. It is also about the same amount of time it takes for the AGM batteries to start to heat, so no big deal. We have found that we never need to run that high though as we always used the switchable 180 amp setting instead which can run continuous without overheating either. I now have the two settings at 180 and 120 and we haven't even needed the 180 very often. Our limits are set by a top limit on the field voltage (pwm) from the remote regulator so we still will flash higher with a cold alternator. The 180 amp setting will flash to 250+ amps for a while, which is actually a good thing for recovery and it backs down as it heats the alternator to the 180 continuous.

[jakegw2]

marcopolo - Not a Battleborn battery management system. For clarity, I have a Victron Battery Monitor installed and the shunt is on the negative connection for the Battleborn batteries. My measured values are all from that location.

Booster - The 185A value is from the spec sheet for the alternator. I have not measured it at the alternator, I only measure at the house battery negative connection on the Victron BMV.

The tapering from down to 70A happens even while driving at highway speeds, so it doesn't appear to be alternator RPM dependent.

There is a possibility that the output is being limited to control temperature by the alternator, I can't rule that out until I take some temp measurements. The more probable explanation however is that the chassis computer is limiting the continuous output to prevent an temperature issue from developing.

[markopolo]

I'm still curious to know system voltage when you see the current reduce down to 70A. Is the alternator able to stay at or above 14V?

[booster]

Originally Posted by jakegw2

marcopolo - Not a Battleborn battery management system. For clarity, I have a Victron Battery Monitor installed and the shunt is on the negative connection for the Battleborn batteries. My measured values are all from that location.

Booster - The 185A value is from the spec sheet for the alternator. I have not measured it at the alternator, I only measure at the house battery negative connection on the Victron BMV.

The tapering from down to 70A happens even while driving at highway speeds, so it doesn't appear to be alternator RPM dependent.

There is a possibility that the output is being limited to control temperature by the alternator, I can't rule that out until I take some temp measurements. The more probable explanation however is that the chassis computer is limiting the continuous output to prevent an temperature issue from developing.

Now that is really interesting. My bet is that the hot comes before the limiting as otherwise there would be no reason to have a 220 amp alternator. In normal vehicles these days, they tend to hit the starting battery really hard right after a start to get as much of that start power use replaced as quickly as possible. I wouldn't be surprise that is what you would be seeing. It might be 120 to coach as you have seen and the rest to the starting battery, but the guess is that the alternator is maxed until it heats up which won't take long.


The temps you get will be a really good help to try to see what is actually happening.

[jakegw2]

Ok, so I took some measurements this morning. Here are the details:

2017 model year Dodge Promaster, 220A alternator. 2.9:1 pully ratio. Expected output (from spec curve) at engine 750 RPM (2175 RPM alt): 155.8A

Very cloudy day, quite dark out but muggy. I ran the AC for about an hour to lower drain the battery (not hot enough to run at 100% duty cycle, so it only got it down to about 64% charge = 72Ah deficit).

Battery bank is 2 x 100Ah Battleborn LiFePO4 batteries. Current measurement made with Victron 702 BMV measuring at the battery bank (e.g. does not measure chassis load or house load, only current flowing in or out of the battery bank).

Before starting the engine I see the following:

Current flow at battery: +1.1A (from solar)
Solar output: +1.3A (e.g. there is about 0.2A draw from house load)
Ambient Temperature: 71°F (from dash readout)

Alternator Temperature 74°F (from non-contact spot reading at metal alternator body near the front of the alternator by the pulley. This location was used for all measurements. It is not fully reflective of the alternator temperature in the short-term because the diodes are located in the back which I could not reach. The front is also where the cooling fan inside the alternator is located.)

All chassis accessories turned off (no AC, no radio, no headlights)

At engine startup I saw the following:

• Current into battery 102A
• Engine RPM 750 @ idle (which is where I kept it for the full measurement cycle)
• No increase in current when engine RP raised to 2800 and held there for 30 sec. (e.g. something else is limiting the current input to the battery bank).

See the chart for my full measurement results as the alternator brought the battery from 64% charged to 100% charged.

Observation and Notes:

• I did not see the 120A input I have seen in the past. Theory 1 - perhaps it was combined input with my solar panels? They put out about 19.5A in full sunlight. Theory 2 - I had to move the RV up on ramps so I could reach the alternator, perhaps the 3 min of running lowered the current before I started the measurement cycle.
  
• The current drop over time appears to be entirely driven by the battery's ability to accept charge. The first significant decline happens when the SOC
  reaches 96%.
  
• Turning on the AC with fan on high dropped the output from around 92A to 70A. The radio made no appreciative difference. I suspect my previous observations about Current drop over time were more driven by chassis and house load (inverter running the fridge / TV & DVD player on / AC on medium-high is typical for me).This would indicate that with all of those loads I really was at the alternator max output. Take this observation with a grain of sand, I didn't test it exhaustively or carefully.
  
• When the cooling fan on the engine cycled on it dropped the current by about 20A, but the output would climb back up again to around 92A. This seems to indicate the 92A is not the alternator output limit. Again, take this as tentative, however more reliable than the previous observation as the cooling fan ran for much of the test.
  
• When I stretched I could get a further back on the alternator and read temps from closer to the back. They were consistently higher, but I never saw a reading over 195°F.

[booster]

Very interesting, thanks for getting all that information.


Bummer that it is so hard to get to the alternator to get temps. On all our the ones we have, which all are modern front and rear fan style, the coolest spot is in the front, hottest was at laminations in middle of the alternator and the diodes area and output post was about 10-20* cooler than the laminations. The front was much cooler on ours, 30-40* cooler most of the time.


Also something that will give you low readings is the spot size of the infrared thermometer. The spots get big really quickly with distance and even on my Fluke I had to be within about 4" to be getting the hottest spot repeatedly. Also need to be quite perpendicular which can be tough in tight spots.



Really hard to tell where the power is all going, though. It is interesting that Battleborn told another member, IIRC, that even though the batteries say 40 amp limit that they could accept like 80-100 amps like they used to be rated, so I would expect them to be taking more if it was available. You don't happen to have a DC clamp on ammeter, do you, so you could check the alternator output wire?


A test that might be interesting would be to turn on a bunch of chassis loads while the batteries are at max amps to them. Heater fan on high, rear window defogger, headlights, etc. If the alternator is maxed out, you charging amps should drop a lot, but if the alternator is just being limited by the PCM of the van it should see those items come on and allow more charging amps so you would see a smaller drop in charging.


Do they really run that engine at 220*? That is pretty hot a place to be and leaves very little headroom for loading it. Is this of the vehicle gauge or an OBD reader?

[markopolo]

Fantastic post Jake - full of data!

My guess is that the lower than expected current prior to tapering is related to voltage. Your testing shows 13.9V & 14.0V then. Current acceptance would be higher at 14.4V for example.

That said, I like charging lithium at 14.0V as the cells stay more closely balanced compared to when I charge at 14.4V.

If faster charging was needed then a boost/buck DC-DC charger would supply a steady 14.4V or 14.6V to the batteries.

It would be useful to know what voltage triggers BMS balancing with Jake's Battle Born batteries and the OP's Eco-Ion lithium batteries. That would help with the decision re: needing a DC to DC unit.

ram alt out crv pdf.png

Looks like around 130A 14V expected when hot & alt shaft rpm at 2175 so maybe you're getting what's expected. ReilyM measured 40A to 20A for chassis needs on his Promaster. 30A chassis (avg) + 100A coach = 130A

[jakegw2]

I used an Etekcity 630 non-contact dual-laser thermometer. The dual lasers are configured to show the spot measurement size. I used them to ensure I was taking a true spot measurement on the alternator.

When you mention it, I suspect my alternator has a rear fan as well. If it had a similar temperature gradient to yours the max temp would be around 200-210°F. Not terribly far from my spot check of 195°F.

I know the batteries can accept more charge since I have definitely observed it happening in the past. They are rated for a safe (e.g. no affect on 10 year lifespan) charge rate of 50A each (so 100A total), however they can accept up to 100A each (200A total) with some reduction in longevity.

Agreed on the value of a maximum-loading test. Perhaps another time I will give it a try. I know it is possible to max out the alternator. When I run the AC on the inverter (along with the dash AC on max) the net flow to the batteries is modestly negative, indicating the alternator is fully tapped out and the batteries have to supply the difference.

Engine temp readings from an OBD reader. I agree it seems quite high, and under hard acceleration up a hill it will climb above 233° if I let it. That's part of why I have the OBD gauge - so I can manage the temperature myself by modifying my driving when needed. Perhaps they keep it high to promote more complete combustion?

Regarding the LiFePO4 balancing - I have a solar charge controller configured for Lithium. Since it is always on it trickle-charges at a higher voltage to ensure balancing. The alternator provides the bulk charge and the solar provides the higher-voltage charging that is needed periodically.

[engnrsrule]

A lot of good advice above, but take a full systems approach. Before investing in solar to extend your boondocking limitation consider all other limiting systems. My RT has a 10 gal black tank. That is our most limiting system, equating to 3-4 days (2 people); we have managed 7 days when other toilet facilities are nearby. We greatly improved our electrical endurance by going to 2 6v golf cart batteries for 235 ah, vice the original 1 12v at 90 Ah. also added battery monitor and now can manage 7-14 days or more on battery. I probably would not consider solar unless I also changed to a composting toilet. Propane is least limiting. With liberal use I fill up once or twice a year. We do not use the generator much (like to run air conditioning) so it seems to last forever running fridge, hot water and furnace when needed. If your fridge has to run off 12v you need a lot more battery capacity.

[RMLetstryrving]

This is the first time we have participated in a “Forum” of such knowledgeable participants. My wife and I have never RVed before and are doing this because we love to travel. Before March of 2020, we would fly to a destination and then board a ship for 30+ days. We don’t see ourselves travelling like that again for a while.

We decided to travel throughout North America for now. I think my request for information was a little premature until we really do some RVing and knowing what is really involved and how it all works. Have read through all of the posts and realize that I don’t have the information that you have asked for because I don’t have the van as yet. We have been watching youtube videos trying to get an idea as to what to expect, I know youtube videos are not always the best source of information but when you research a topic, you have to check everything resource available.

We want to thank everyone for the comments, suggestions and recommendations. We will continue to monitor this Thread and provide additional details once we get the Lexor and experience Rving for ourselves.

Sorry for not being as active as I should be in a forum that I started.

[booster]

Originally Posted by RMLetstryrving

This is the first time we have participated in a “Forum” of such knowledgeable participants. My wife and I have never RVed before and are doing this because we love to travel. Before March of 2020, we would fly to a destination and then board a ship for 30+ days. We don’t see ourselves travelling like that again for a while.

We decided to travel throughout North America for now. I think my request for information was a little premature until we really do some RVing and knowing what is really involved and how it all works. Have read through all of the posts and realize that I don’t have the information that you have asked for because I don’t have the van as yet. We have been watching youtube videos trying to get an idea as to what to expect, I know youtube videos are not always the best source of information but when you research a topic, you have to check everything resource available.

We want to thank everyone for the comments, suggestions and recommendations. We will continue to monitor this Thread and provide additional details once we get the Lexor and experience Rving for ourselves.

Sorry for not being as active as I should be in a forum that I started.

No problem here, for sure.


Diving in without having what you need to know or having tried some of it can make for extra expense and hassle. I think you are very wise to sit back and wait and learn what you can until your van shows up.