Replacing OEM batteries with LiFePO4's

turbopilot

New member
TurboPilot - that $380 every 2 years is pretty appealing, compared to $2600 every whenever <g>... I'm also assuming that the cost will go down with time - and in fact, it'd already be a lot lower if I built up cells like what AM Solar is selling, instead of buying drop-ins.

So I'm talking against my own system here, but it IS appealing to use batteries you can get cheaply anywhere, use them as hard as you choose, and just replace them when they die. I'm a techie type and I don't personally like that route, but as long as you understand what you're doing, it can be a very cheap route to go. And I think it's what many RV'ers do, though by ignorance or inattention <g>...
Peter you did some outstanding research. I really appreciate your thread on these issues. Like you, I am also a techie and love to try out the new stuff even when it is not yet economically viable. LiFePO4 is the future, no doubt about it. They just need to get the price point lower.

I was all set to order the LiFePO4's when I measured the battery compartment in my 2016 Unity. It appears to be only 25" wide, while two SB100's need 25.5" side by side. I need to double check that measurement but it looks like I cannot fit two SB100's in there as I hoped. So current plan is convert that damned propane solenoid to a magnet switch then just run the lead acids to near full discharge when I need to and see if I have enough amps for my needs.
 

Peter Tourin

2020 Unity RL, ex 2012 Unity MB
I got caught by surprise with the width of the battery box. The box is a bit wider than it looks, because of the rubber gasket at the top. But it was a very tight fit! I had to push the wires that come in at the back of the box in order to get the batteries in. I had to remove the bottom battery positioning brackets. I had to redrill for the top brackets, as the height is different. But they did go in.

If I were to do this again, I don't think I'd buy drop-in batteries again. I keep waiting for when AM Solar can ship - I thought of building up my own batteries as they do, but chickened out and went with the drop-ins. However, their battery management is almost non-existent and I've had a great deal of trouble even getting them to tell me clearly what that system does and doesn't do. We'll see how they perform - time will tell...
 

alichty

2014 LTV Unity TB
turbopilot - thanks for bringing another set of eyes and thought to this discussion. I have been following Peter's progress carefully through this thread and others and have also spent a lot of time chasing through similar threads on open water cruising forums and had to conclude that while this is clearly the future of battery power it still falls short of being practical for everyone. For me cold weather camping is a critical piece of the puzzle and not being able to charge the lithium batteries below freezing is a complete show stopper for me. I store my RV during the summer and bring it back out to use for fall, winter, and spring. I don't try to camp in ski resort parking lots but I have spent over a dozen nights out since early fall this year with temps into or below the 30's. I was thinking that I needed something like LiFePO4's to make it through cold nights but that was without good battery monitoring onboard and a poor grasp on just what the consequences really are for delving below a 50% SOC. Knowing I can dip below that and having a good battery monitor now (Magnum ME-BMK) gives a lot more confidence it being able to get by with the Interstate battery bank.

You confessed to being a techie so I won't feel bad about what comes next :rolleyes:

You mentioned having 2 232AH batteries in your shiny new coach so you are doing your homework on Interstate's web site. Have you had the time to explore what LTV has done to set up your MM1212 charging specs to properly get 232AH at 100% SOC? You have the programmable ME-RC remote that can meet Interstate's charging specs under the menu item setup>04 Battery Type>custom. The menus that follow allow you to match the specs for fully charging the Interstate GC-2 batteries. Can you verify that LTV has programmed the ME-RC to meet that spec so you do have a full 232AH? The default programming parameters for a wet cell battery will not give you a full charge with the Interstates. For the record I have the same inverter as you (MM1212) using a Magnum ME-RC remote and I have added in the Magnum ME-BMK battery monitor. I have programmed mine to use Interstate's specs for their GC-2s.

I am still delighted that Peter has taken this plunge for the LiFePO4s and do hope they end up working out. :clapping:

I hate it when ancient technologies like lead acid batteries keep hanging on because we have wrapped ourselves around being so integrated with it.....
 

turbopilot

New member
..Have you had the time to explore what LTV has done to set up your MM1212 charging specs to properly get 232AH at 100% SOC? You have the programmable ME-RC remote that can meet Interstate's charging specs under the menu item setup>04 Battery Type>custom. The menus that follow allow you to match the specs for fully charging the Interstate GC-2 batteries. Can you verify that LTV has programmed the ME-RC to meet that spec so you do have a full 232AH? The default programming parameters for a wet cell battery will not give you a full charge with the Interstates. For the record I have the same inverter as you (MM1212) using a Magnum ME-RC remote and I have added in the Magnum ME-BMK battery monitor. I have programmed mine to use Interstate's specs for their GC-2s.
Just working my way through the documentation on the ME-RC. Please post the custom settings your are using.
 

alichty

2014 LTV Unity TB
Just working my way through the documentation on the ME-RC. Please post the custom settings your are using.
Easy to check since I am camped out along your coastline tonight :smirk:

setup>03 Absorb Time>Absorb Hrs = 2 hrs (this is a default)
setup>04 Battery Type>custom>Absorb = 15.3V
setup>04 Battery Type>custom>Float = 13.4V
setup>04 Battery Type>custom>Equalize = 15.6V
setup>05 Charge Rate>Max Charge = 80%

The Absorb hours doesn't seem to be meaningful because the MM1212 is using the voltage number as a signal to switch from Bulk to Absorb. Absorb will run until the input amps drops below 20. That switches over to Float for the remainder of the charge cycle.
 

turbopilot

New member
Easy to check since I am camped out along your coastline tonight :smirk:

setup>03 Absorb Time>Absorb Hrs = 2 hrs (this is a default)
setup>04 Battery Type>custom>Absorb = 15.3V
setup>04 Battery Type>custom>Float = 13.4V
setup>04 Battery Type>custom>Equalize = 15.6V
setup>05 Charge Rate>Max Charge = 80%

The Absorb hours doesn't seem to be meaningful because the MM1212 is using the voltage number as a signal to switch from Bulk to Absorb. Absorb will run until the input amps drops below 20. That switches over to Float for the remainder of the charge cycle.
Thanks. Next time I am at the rig I will check to see what setting LTV put in.
 

Peter Tourin

2020 Unity RL, ex 2012 Unity MB
Wade: No, the 6.5" width of the my 2 SB100's left just enough room for mounting the shunt on the stair riser facing the sides of the batteries.

> I am still delighted that Peter has taken this plunge for the LiFePO4s and do hope they end up working out. <
Thanks! I would be delighted too if someone else had already figured out all this LiFePO4 stuff so I knew that it was going to work <rofl>...

At this point, below-freezing charging is the biggest issue for me too. I believe I can manage all the other issues. I don't know how well the battery box is insulated underneath - there's some, but I haven't really paid a lot of attention yet to just how much. If I'm driving and camping in cold weather, I'd expect the inside of the RV at 65-70 to offset the outside temps - I just ordered a cheap digital adjustable temp sensor with an internal relay, so I'll be able to both watch the temp at the bottom of the battery box and open my charging controller if it gets too cold - but I won't be able to play with it till next Spring so it's going to be a while before I know. Gotta retire so I have time to play...
 

turbopilot

New member
Wade: No, the 6.5" width of the my 2 SB100's left just enough room for mounting the shunt on the stair riser facing the sides of the batteries.
Looks like I have a 12v bus on the back of my battery box. Cable coming in from the right center of the image is the +12v from the battery. Looks like 3 cables then leave the bus along with a yellow wire. Don't have a schematic so don't know where they go.

Front of the battery box is on the right side so the smaller cable sweeping up to the right might be the connection to the cab. May be the other two go to the battery switch and inverter. Just guessing.

 

Peter Tourin

2020 Unity RL, ex 2012 Unity MB
I can't figure out the frame of reference for the photo. When you say "the back", do you mean the back when you're standing in the stairway with the step raised - that is, the long side of the box that's nearest the centerline of the RV?

That pic looks somewhat like what I have - a junction point that contains a big fuse. I'd think you'd have a big lead going to the batteries, and 3 leads coming into the junction box: one from the isolator relay (alternator charging line to the batteries), one from the DC disconnect switch (charger line to the batteries) and one to the generator. I'm not sure what the small yellow is.
 

turbopilot

New member
I can't figure out the frame of reference for the photo. When you say "the back", do you mean the back when you're standing in the stairway with the step raised - that is, the long side of the box that's nearest the centerline of the RV?

That pic looks somewhat like what I have - a junction point that contains a big fuse. I'd think you'd have a big lead going to the batteries, and 3 leads coming into the junction box: one from the isolator relay (alternator charging line to the batteries), one from the DC disconnect switch (charger line to the batteries) and one to the generator. I'm not sure what the small yellow is.
Peter, sounds right. I simply slid the batteries back and stuck the iPhone down into the box and shot the inside wall of the battery box. Makes sense that there would be a fuse under the rubber cover before distributing 12 volt from the battery. Not sure this is the best arrangement for a 12 volt system, but it is what we have.
 

Peter Tourin

2020 Unity RL, ex 2012 Unity MB
I gather that a few people have replaced it with a breaker that has a manual shut-off switch. That would be handy in my case - at present I have no way of preventing charging from happening, since the alternator line comes to that junction box.
 

turbopilot

New member
I gather that a few people have replaced it with a breaker that has a manual shut-off switch. That would be handy in my case - at present I have no way of preventing charging from happening, since the alternator line comes to that junction box.
Peter, got the schematics for my rig. The black cover on the back of the battery box covers two 200a fuses. 12+ from the battery terminates at the base of the twin 200a fuses. One fuse terminates at the lead going to the generator, the second fuse has three terminations: battery switch, IRD solenoid to the chassis and a #8 wire to the solar controller.

All of this makes sense though I would like to see these connections in a separate enclosure. The only concern I have is that it looks like there would be no way to "jump start" the engine using house batteries in the event of a chassis battery failure with the current setup. IRD will not open the IRD solenoid unless there is at least 13.5v on the chassis side of the solenoid. I suppose you could "jump" the IRD solenoid with a 12 volt wire from the house battery to power the starter motor on the Sprinter engine. Or if battery cables were long enough you could jump start from the house batteries directly to the +12 in the engine compartment.
 

SSTraveler

2014 LTV Unity Murphy Bed
I attached Battery Tender terminal connectors, http://www.amazon.com/gp/product/B0...rue&ref_=ox_sc_act_title_2&smid=ATVPDKIKX0DER and use Battery Tender 12' extention cable, http://www.amazon.com/gp/product/B0...rue&ref_=ox_sc_act_title_1&smid=ATVPDKIKX0DER to jumper the two batteries if I ever need that option.
I realized this was an added benefit after I used these to hook up my two Battery Tender Solar charger/maintainers, http://www.amazon.com/dp/B004Q86JJ8/ref=twister_B00UYBAP0K?_encoding=UTF8&psc=1. The battery terminal connectors came with the solar panels, but you can buy them separately as described above. The Battery Tender Solar charger/maintainer works great to maintain my batteries anytime I have it parked between trips or for the Winter. I just place them in the front windshield and they work great. :thumbup:
 

turbopilot

New member
..
I realized this was an added benefit after I used these to hook up my two Battery Tender Solar charger/maintainers
In my last RV (an EarthRoamer) there was a "combiner" switch (Blue Sea) which automatically hooked the house battery and chassis battery together, yet isolated the chassis battery anytime system voltage fell below a certain level (around 12.7 volts if I recall correctly). This protected the chassis battery from inadvertent discharge. This also allowed all batteries to be maintained by one controller for long term storage (AC charger for indoor storage and solar charging for outside unplugged storage).
 

israndy

2007 LTV Serenity
There is also a nice one called Trik-L-Start that will help charge your chassis batts when there is charge going to the house batts. Unlike using a combiner you don't have issues with the charge cycle of the set of house batts. It is always best to have both house batts changed at the same time, as charging two batteries that are at different times in their lives means they need different volts and amps to best charge. Same thing happens when you pair your house and chassis batts on anything but a trickle. The adapter above hooks over your battery isolator and allows just a few watts thru, so your house charging isn't brought down to the level of your chassis battery, yet your chassis batt gets some help from the charging you are doing. I got mine for less than $40.

-Randy

ps. I did have to cut mine out recently as it was messing with my battery trouble shooting, but I have been running it successfully for years and it's otherwise been great. I will be putting it back on with a quick disconnect switch on one side for trouble shooting starting issues.
 

Peter Tourin

2020 Unity RL, ex 2012 Unity MB
Randy just hit on something that I've been thinking over these last few days - getting some wiring schematics has also fed this spate of brain activity. I'm wondering how charging works when your house and chassis batteries are not identical. This isn't so much of an issue with a mix of standard and AGM batteries, because their voltages and charging algorithms are similar. But my chassis battery is an AGM and my house batteries are LiFePO4's, so it's a different world. Here are a few tidbits to mull over:

* How does the system charge when you're driving? In my RV, the isolator relay closes and both systems see the alternator voltage of 14.2-14.4 volts. This seems OK - the chassis battery will charge as usual - the house batteries will get up to about 60A at that voltage, and they'll charge, though not quite up to 100% SOC (that takes 14.6v).

* How does the system charge when you're on shore power? For the moment I'm going to assume the isolator is closed. Both batteries see the charger voltage. I'm not sure what happens here. I know how the LiFePO4's will charge but I'm not sure what will happen with the chassis battery. I assume that it'll ramp up to 14.6 as well - I'm not sure if this is a problem for the chassis battery or not - IIRC, it's an AGM. Of course, if the isolator is open there's no potential problem - only the house batteries see the charger.

* How does the isolator work? I believe my RV has a "dumb solenoid" with an Intellitec IRD - this is a voltage sensing and time delay unit like what you'd get in a hybrid isolator - LTV just happens to have done it with a separate IRD and solenoid. I'm not sure which of their models are in my RV - they apparently have 2 models with slightly different open and close voltages and time delays. They can look at both chassis and house battery voltage and close the isolator solenoid when the voltage on either goes over 13.1v or 13.3 depending in which model. But the RV schematic shows that they're wired to only sense the chassis battery voltage. That's good for me - the rest voltage of my house batteries at full charge is 13.4 - that would force the isolator to remain open most of the time - with standard or AGM batteries, the full charge rest voltage is 12.8, so the isolator would only close when the charger or alternator brings the voltage up into the low 13's.

You see where I'm going here. By adding the lith batteries with their higher rest voltage, I've changed the way the RV's isolator circuitry is going to work, and I'm not sure what that's going to do. Still in the process of thinkng this out - just wanted to mention it because as with many things, when you get a bright idea and make a change, you may be affecting more things in a complex system than you thought you'd be affecting. I'm obviously using this thread as a place to think out loud, so I'm interested if anybody has thoughts on this.
 

turbopilot

New 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.
 

jackfish

Active member
Because I had the Blue Sky Solar Boost 3024iL solar charge controller I was presented with the opportunity to use its 2 amp auxillary battery charger. When in acceptance or float conditions, up to 2 amps is diverted to charge the chassis battery. The 3024iL can be used with many lithium battery products.
 

jackfish

Active member
I guess I am unclear about different charging sources "fighting" and "battling".
 

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