Replacing OEM batteries with LiFePO4's

turbopilot

New member
I guess I am unclear about different charging sources "fighting" and "battling".
I am referring to the charge controllers each trying to "smartly" charge the batteries from different sources. Obviously not an issue for the chassis source (which is dumb) but on shore power with solar charger and inverter/charger on line together they each try to smartly charge the batteries. Bottom line you can overcharge the batteries.

Ideally any battery set should have a smart controller which looks at all sources of charging current then applies the current to the battery set smartly and appropriately to the battery type, irrespective of what current source is currently on line.

BlueSea acknowledged the need for such a device and claimed to be working on it.
 

Peter Tourin

2020 Unity RL, ex 2012 Unity MB
Here's an example of the concern - and by the way, this is similar to the question of whether lithium batteries need their internal banks balanced or not. Suppose I plug into shore power and my charger comes on. Let's say that I just pulled in and hooked up, so my chassis battery is fully charged - that'll close the isolator relay and connect house and chassis batteries. So now the charger is seeing my house batteries - let's say they're pretty discharged and are at 13.02 volts. Let's say that my chassis batteries are charged up and still have a bit of surface charge from the alternator, so they're at 12.95 volts. What's going to happen? Will the charger keep trying to bring my chassis battery up, since its voltage is lower than the house batteries? I'm not sure.

As for multiple charging sources fighting, I think this is what turbopilot is getting at: if one of my chargers puts out 14.6 volts (like my lith battery charger) and my solar charger supplies a lower charging voltage, will the batteries try to take most or all of their charging current from the higher voltage source (biggest difference between battery voltage and charger voltage)? That's similar to my example - in the example the question is whether the lower voltage battery will take most or all of the charging current from the charger, since it has the biggest difference between battery voltage and charger voltage?

I don't know how complex systems interact - I put this post out because I don't know and want to find out. I would love to have all these functions happen automatically - but I'm tempted to put a disconnect switch on my isolator relay so I can force it to remain open. Then my alternator charges my car battery and my charger charges my house batteries, and I have a simpler system that I control manually - I simply watch the voltages. But the EarthRoamer example shows how complex it can get - he has alternators, solar charger and inverter/charger - 3 different charging systems that may or may not behave well together. In my case, I have 2 different battery types and 2 different charge sources, an alternator and a converter/charger.
 

Rensho

Member
We had similar issues in the EarthRoamer with no solution. EarthRoamer has 1000 amp/hrs of AGM battery, 3000 watt inverter / 150 amp charger, 1,000 watts of solar panels and 2 chassis alternators putting out 350 amps @ 12 volts. Rolling down the road the alternators and solar panels fought over who was charging the chassis and house batteries. Parked plugged into shore power during the day the solar controller and inverter/charger battled to charge the house and chassis batteries. The only sanity existed off grid with solar only charging the batteries.

I met with the folks at BlueSea who are based in Bellingham, WA about this problem. They claimed to be exploring some technology for a "universal smart charger" that would take amps from any source and charge batteries of different varieties. As far as I know this device does not exist.
Sounds like a CTEK 250S 250S and the added Smartpass.
http://www.batteriesdirect.com.au/shop/product/12680/ctek-smartpass.html
http://www.batteriesdirect.com.au/shop/product/23370/ctek-d250s-dual.html
 

avanti

2014 GWV Legend 3500 I4
I am no expert, but...

I have reached the following two conclusions:

1) Having the chassis battery and its "dumb" charger in your coach loop is a no-win situation. This is one of the things that drove me to a completely separate coach system using a second alternator.

2) If all of your chassis house chargers are programmable and you program them all the same way, there should be no "fighting". They will all make the same decisions in parallel, and so should sing along in more-or-less perfect harmony, or at least close enough for government work.

The only way that my coach and chassis systems interact is via a Trik-L-Start, which seems benign. (I also left my old isolation relay in place, but it is now only activated by a momentary "boost" switch on my dash. If I ever found myself with a weak chassis battery, I would hold that switch in for awhile before cranking in hopes of charging it up enough to get me started.)

I do not feel any great need for a super-smart integrated charger. Am I missing something?
 
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turbopilot

New member
I don't know how complex systems interact - I put this post out because I don't know and want to find out. I would love to have all these functions happen automatically - but I'm tempted to put a disconnect switch on my isolator relay so I can force it to remain open. Then my alternator charges my car battery and my charger charges my house batteries, and I have a simpler system that I control manually - I simply watch the voltages. But the EarthRoamer example shows how complex it can get - he has alternators, solar charger and inverter/charger - 3 different charging systems that may or may not behave well together. In my case, I have 2 different battery types and 2 different charge sources, an alternator and a converter/charger.
The EarthRoamer is obviously configured for extended off grid operation. Weak point in very hot areas: it has no on board generator. So even with all the batteries the air conditioner is only good for about 6 hours on the inverter (AGM batteries).

I am thinking of a dream configuration for the Unity if I was willing to give up extended use of the air conditioner (not sure I am) running the generator.

1. Remove LP Generator.
2. Build custom battery box for two SB300 LiFePO4 batteries and a 3,000 watt inverter which would take the place of the LP Generator. Have not scrubbed the dimensions but I think the batteries would fit in the generator area easlily maybe the inverter/charger too.
3. Remove house lead acid batteries.
4. Add a extra set of FLEX 200 PV panels to the roof.

Advantages:

1. Extended off grid AC/DC power available.
2. Option to switch to DC compressor refrigerator.
3. Reduce the weight of the Unity by +/- 120 lbs.
4. Run microwave, AC ect from the inverter.
5. Propane solenoid becomes a nuisance versus a show stopper.

Disadvantages:

1. No extended off grid use of the air conditioner.
2. Cost of the system would be several thousand more than the diesel generator option. Could net some of that by selling the LP generator.

Difference in Operation

1. Extended off grid operation would require running the Sprinter engine for extended periods of time to top off the big LiFePO4 batteries. In this case swapping diesel for propane to charge the batteries. Not sure this is a disadvantage or advantage, I think it might be an advantage.
2. With fully charged batteries the rig could be operated for several days on DC alone.

In the EarthRoamer with 600 amp hours of batteries and a DC refrigerator in the summer I was able to get by on around +/- 150 amps hours per day. Obviously this did not include air conditioner operation but does include use of the fans. The EarthRoamer had 5 X 200 amp PV panels so I was easily able to make the amps back from the sun. Not feasible with the limited roof area of the Unity.

Phase 2 of the dream once conversion above took place would be to install a marine style diesel fired hydronic heater for camper heat and hot water. This would allow for the removal of the propane tank. Would need to get a small induction cooktop to replace propane burners in the kitchen (that is what the EarthRoamer uses).

Clearly all this would not be cheap to retrofit but if someone wanted to have a custom build of a Unity running on only diesel and the sun, it is clearly feasible.
 

Peter Tourin

2020 Unity RL, ex 2012 Unity MB
Avanti - I'm thinking of doing exactly what you described. In my book, your Trik-L-Start isn't an interactive system at all - it simply takes power from one system to charge another one. Simple system, no problems! I already have the momentary push-on dashboard boost switch - I'm thinking of also installing a dashboard switch that defeats the isolator, so I have more control over my charging systems. I also want to get a chassis battery voltage read-out, either running back to my battery monitor (which can monitor 2 battery systems) or separate.

I have a couple of thoughts on y our post...

1) The M-B regulators are no longer dumb, and it appears that they've gotten smarter since my '12 MB. For example, my regulator seems to limit house battery charge current to around 45 amps or so, and some other threads indicate that the newer regulators are multi-mode with all sorts of complexity. That may mean that they charge the chassis battery better than older systems do, but it makes it a much more complex world when you try to charge 2 systems from the alternator. So I definitely understand the 2-alternator concept, and I've thought a lot about it vs solar.

2) If you mean your 2 alternator/regulator systems when you say "chassis chargers", that seems to make sense. I can see why that "fighting" situation is of interest, especially if you add solar into the mix. But at least in my system, what's more of a question is what you do when your 2 battery systems aren't similar. That's what I'm mostly thinking about - and why I'm thinking of isolating my 2 battery systems until I understand more about how they interact when linked.
 

Peter Tourin

2020 Unity RL, ex 2012 Unity MB
Turbopilot - how would you charge on shore power? I think the largest Progressive Dynamics lith charger is 80 amps, so you'd be talking 8-10 hours on shore power to recharge if they were far down. OTOH - that charger still will run on a 20A breaker and it could be made to work easily in a Unity with a 30A service.
 

turbopilot

New member
Turbopilot - how would you charge on shore power? I think the largest Progressive Dynamics lith charger is 80 amps, so you'd be talking 8-10 hours on shore power to recharge if they were far down. OTOH - that charger still will run on a 20A breaker and it could be made to work easily in a Unity with a 30A service.
The EarthRoamer has the Xantrex Freedom SW Inverter/Charger which if I recall correctly allows custom charging configurations. So it might be configured to support LiFePO4.

It also has an excellent smart power save feature which automatically trims back 110V going to charging anytime other appliances start to crowd the 30amp breaker.

Very capable inverter/charger in a small foot print. It will charge up to 150 amps depending on AC input capacity.
 
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avanti

2014 GWV Legend 3500 I4
1) The M-B regulators are no longer dumb, and it appears that they've gotten smarter since my '12 MB. For example, my regulator seems to limit house battery charge current to around 45 amps or so, and some other threads indicate that the newer regulators are multi-mode with all sorts of complexity. That may mean that they charge the chassis battery better than older systems do, but it makes it a much more complex world when you try to charge 2 systems from the alternator. So I definitely understand the 2-alternator concept, and I've thought a lot about it vs solar.
You're right, of course. "Dumb" was a poor choice of words. What I really meant was more like "highly specialized and oblivious to the needs of the house batteries". As my contributions to those "other threads" indicates, my data suggest that my 2014 I4 is so highly optimized as to be pathetically bad at charging the house battery in the traditional way. That is what pushed me over the edge to committing to a totally independent system.

2) If you mean your 2 alternator/regulator systems when you say "chassis chargers", that seems to make sense. I can see why that "fighting" situation is of interest, especially if you add solar into the mix. But at least in my system, what's more of a question is what you do when your 2 battery systems aren't similar. That's what I'm mostly thinking about - and why I'm thinking of isolating my 2 battery systems until I understand more about how they interact when linked.
"Chassis chargers" was a typo. I will fix it. I meant "house chargers". Sorry.
My chassis alternator can no longer charge my house, nor does it need to due to the second alternator. It is out of the equation. The house batteries can be charged by any and all of (a) solar; (b) shore power via the Outback inverter/charger; and (c) the second alternator via the Balmar charger/regulator. All three are capable of proper 3-stage charging and all can be programmed to be consistent with each other. That was all I was trying to say. Sorry for the confusion.
 
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Peter Tourin

2020 Unity RL, ex 2012 Unity MB
Yes, now I'm remembering that you were one of the big participants in that thread. And that thread was what alerted me to the fact that the M-B charging systems were evolving rapidly. I haven't had much time to experiment since I installed the lith batteries - no long trips yet since Jean had the MB till October. But from what I see, no matter how far down the house bank is, the alternator gives it around 14.2v at a max of about 45 or 50A - so there must be some charge management circuitry in action there. As it turns out, that voltage wont' hurt my house liths, though it won't fully charge them either.

Since I don't have solar, I only have one house charger, and it's a lith charger. I'm not sure what the M-B charging system does - whether it's multi-mode, etc. - I need to get the time to watch it and find out. But my house charger is a simple CCCV charger, which is what the lith batteries want. When first started, it charges at near its rated current (mine's rated at 60A, I actually see around 45A max, but I've never had the batteries WAY down yet) and the voltage slowly climbs to a max of 14.6 as the batteries get nearly full - that's the Constant Current part. Then the charger holds 14.6 and keeps charging until the battery climbs up to almost 14.6, with the current dropping to near or at zero as the battery gets fully charged - that's the Constant Voltage part. I've watched it do this, monitoring the house voltage and charging current over time as the battery fills up.

I'm still not sure about your 2), and I want to learn more about complex system behavior. Basically, I'd like to understand 2 things: first, if all your house chargers are configured so that they're almost the same, will the batteries still pull their charging current from the charger that's putting out the highest voltage at any particular moment? And second, if house and chassis batteries are at different voltages when connected to a single charger, will the battery with the lowest voltage take all or most the charging current?

I'm no electrical engineer, though I've had some practical experience with various systems, including a 50kw hydro site. So this stuff comes a bit slow for me. I know that in the lith world, that second issue is complex. The reason some lith batteries have internal balancing circuitry relates to this issue. Suppose a nominal 12v lith battery has four 3v banks in series. And suppose the four banks aren't balanced - that is, one is weaker or less charged than the other three. The charger will keep trying to bring up the weakest bank while the other 3 cells overcharge - unless the battery has some bank-level balancing circuitry to prevent this situation.

I bought my batteries from SmartBattery - they claim several things. First, they very carefully match each cell and each bank of cells during manufacture, so they don't need any internal balancing circuitry - and they don't provide any. Second, you can use a simple CCCV charger like the Progressive Dynamics one I bought, because all the cells will become fully charged at the same point since they're balanced - so the charger current will drop to zero and even if the charger remains on, no banks will get overcharged. That's the claim, and I don't think anybody is in a position to prove or disprove it at this point. But I want manual control of my charging systems - I'd rather be safe and stop charging at or near full charge and not risk the possibility that SmartBattery is wrong <g>... That was one of the topics of my original post on this thread. It sounds to me like you're going through similar issues and thought processes, even though our systems are pretty different.
 

turbopilot

New member
Yes, now I'm remembering that you were one of the big participants in that thread. And that thread was what alerted me to the fact that the M-B charging systems were evolving rapidly. I haven't had much time to experiment since I installed the lith batteries - no long trips yet since Jean had the MB till October. But from what I see, no matter how far down the house bank is, the alternator gives it around 14.2v at a max of about 45 or 50A - so there must be some charge management circuitry in action there. As it turns out, that voltage wont' hurt my house liths, though it won't fully charge them either.
So far I have no experience with the MB charging characteristics. For comparison, I can tell you that the late model Ford SuperDuty trucks have a temperature compensated charging schedule. System voltage will taper down from around 14.2 to as low as 13.6 at very high ambient temperatures. In the F550 the engine PCM was reading temperature data from the ambient temperature sensor on the right mirror to make this adjustment.

Will be looking to see how the MB handles temperature compensated charges.
 

israndy

2007 LTV Serenity
Re: Battling chargers

The house batteries can be charged by any and all of (a) solar; (b) shore power via the Outback inverter/charger; and (c) the second alternator via the Balmar charger/regulator. All three are capable of proper 3-stage charging and all can be programmed to be consistent with each other. That was all I was trying to say. Sorry for the confusion.
I am excited that someone has done the 2nd alternator trick, like the guys at RoadTrek have pioneered. I should probably do that before everyone stops making parts for the T1N.

Curious what you think you mean by "all programmed to be consistent"...

If I have a battery pack and it's at 12v so they have room to be charged and I turn on a charging source, that source (assuming like you say is capable of intelligent 3-stage charging) will see the 12 volts and pump it full of current as it is in need of bulk charging. But at some point it will detect by measuring the voltage that there is no room to provide bulk power and will ratchet back to acceptance charging, typically you will see on a voltmeter the measure going from 14.4v bulk to 13.8v acceptance. Eventually the charger will measure that the battery can no longer accept the current and will ratchet it back again to 13.2v so as not to boil away the battery water.

The problem is, you want to charge your batteries after using them up all night, you have this great 90 amp (in my case) charger and you plug it in, it starts going but then the first rays of sun hit the solar panels on the roof. It's only gonna have 2 amps of power this early, but it puts it out to the battery as best it can. The charger sees this voltage when it is testing what stage to charge at and decides the battery must have this voltage that is actually coming from the panels and it backs down from charging, maybe all the way to trickle charge. So even though you are plugged in, when you go to leave the site the batteries are still low as neither charge source took the lead and filled the batteries up. If you had unplugged one of the sources you would actually have MORE charge in the batteries at this point.

Now there are chargers, like the one RoadTrek uses, I think I saw it was by AMS, that have inputs for solar, wind, alternator, and shore, and then it takes the power of all the sources and charges the batteries the best it can. I think this is all on the house side, the chassis uses the other alternator only, as in your car. I love this approach and am trying to emulate it, but I have to do it by hand, flip the solar breaker when I am on shore. I may add the dash switch for the isolator to keep the alternator from messing with the solar 3-stage while driving.

-Randy
 

avanti

2014 GWV Legend 3500 I4
First of all, let me repeat two points I made above:
1) I am no expert; and
2) My claim is that typical multi-charger systems work "well enough for government work."

That said, there is no doubt that the interactions among the charging algorithms of various 3-stage chargers can be very complex and hard to predict. The results can certainly be less than optimal. But, in practice my (limited) experience suggests that the results are very typically acceptable under most conditions. In the case you cite, the shore charger is happily in bulk mode, working toward raising the system's voltage to its "absorption" target. If the solar charger then joins the party and has the same target voltage, it hopefully would make the same decision and start contributing amps until that target is reached. Is that what will really happen in any given case? Hard to say, since it depends on the details of the implementation of each charger's algorithm. [EDIT: I guess whether this story makes sense depends on whether the chargers ramp up to the target voltage, or just slam it on until the current target is reached.] You can raise your odds by setting the target for the "preferred" charger a bit higher than the "secondary" one. There are also tricks that you can play with setting different bank sizes (since we have to worry about current targets, too).

Truth be known, I haven't thought TOO hard about this, since empirically, my system seems to work just fine. I have ordered a clamp ammeter, and will do some more exploration when it arrives. If you would like to drink from a fire hose, I recommend the following article on this topic:

http://roadslesstraveled.us/charging-rv-marine-batteries-solar-power-shore-power/
 
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Peter Tourin

2020 Unity RL, ex 2012 Unity MB
Now that's an interesting article. I just skimmed it, but they're discussing just what interests me at the moment - the dynamic interactions when several systems are working at the same time.
 

Peter Tourin

2020 Unity RL, ex 2012 Unity MB
Calbiker - too late, I've already installed 2 SmartBattery SB100's. But I did look at several companies like CALB and thought of building my own. Chickened out, I guess - but that was a year ago. At this point there are several sources and more information available - I might do it differently if I did it again.
 

wade5979

New member
Peter, Picked up our 2016 MB this week in Vegas and are headed back to Naples. There is plenty of room for an additional battery tray under the hood did you give any thought to adding a third smart battery there. I know I would need to upsize the wire gauge since it would be farther away from the other two but would there be any other issues with a third that you've seen in your research
 

Peter Tourin

2020 Unity RL, ex 2012 Unity MB
I think I've got an empty space there too. The only thing that immediately comes to mind is what would happen with charging - you'd have 3 batteries in parallel but one would have much longer wire lengths than the others. You'd also have to be careful about cold weather - if you were parked, that battery would get cold faster than the ones that are in the battery box. But it'd be a way of getting more battery power without taking up storage space - better than putting it in the outside storage box behind the battery box.

I think in my MB there'd be space under the murphy bed for more batteries - 2 or even 3, it's a big space. That'd be a lot of battery power! - and if I bought them, I couldn't afford the gas to go anywhere <g>...
 

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