Travato LiFePO4 Battery Install

[wincrasher]

I got my battery and charger installed.

Wincrasher's Travels: Smart Battery Lithium Ion Battery Project

[markopolo]

Holy Moly you did it! That's kind of exciting.

How you figure out the lithium battery SOC will be interesting. I've read pretty much the same thing you posted - that it's 12.8v for a long time then severely drops off. I'm sure you'll figure it out.

Nice write-up on your blog

[booster]

Originally Posted by markopolo

Holy Moly you did it! That's kind of exciting.

How you figure out the lithium battery SOC will be interesting. I've read pretty much the same thing you posted - that it's 12.8v for a long time then severely drops off. I'm sure you'll figure it out.

Nice write-up on your blog

I would think you would have to use a Trimetric.

[eric1514]

I'm sorry, I don't mean to be Debby Downer here, but there must be something I'm not understanding with this whole LiFePO4 thing.

You spent almost $1500 dollars to achieve what you already had except that it weighed less than 50lbs more. You could have paid a guy with a welder to fabricate a bracket for that AGM for about $100.

I applaud the effort and I'm learning from all this and your blog, but this, I just don't get.

Eric

[wincrasher]

That's OK Eric. Sometimes I do things just to see if they can be done. This is about the cheapest way to go if you want Lithium.

There are definately some advantages - the weight savings is alot more than 50 lbs. The recharge time is significantly improved. Hopefully the useable life is longer, negating some of the cost difference.

Compared to the single battery setup, this is double the useable capacity. So if you were going to upgrade from the single, stock AGM battery, this is probably alot easier of an upgrade than the route I took.

[eric1514]

Originally Posted by wincrasher

That's OK Eric. Sometimes I do things just to see if they can be done. This is about the cheapest way to go if you want Lithium.

There are definately some advantages - the weight savings is alot more than 50 lbs. The recharge time is significantly improved. Hopefully the useable life is longer, negating some of the cost difference.

Compared to the single battery setup, this is double the capacity. So if you were going to upgrade from the single, stock AGM battery, this is probably alot easier of an upgrade than the route I took.

Fair enough. If my AGM died, I might go this route, also.

[wincrasher]

If I get some performance out of this battery, I may consider getting one for my T@G. Tongue weight is an issue on the small car I pull it with, so even getting it 20 lbs lighter makes a difference. It's alot of money to get that 20 lbs!

[eric1514]

For the converter you removed, you could have bought a "pendant" which would have allowed you to force the converter to charge in different charging modes.

Is there something similar for the new converter or would you even want that capability?

Eric

[wincrasher]

That pendant will let you force the charger into Boost mode for a period of time. That is not enough voltage to charge these (at least according to the manufacturer) and then it also returns to the normal cycling after boost is over, which is not good for the lithiums.

So I thought changing out the charger was in order. I suppose I could have gone with the 70 amp or higher charger, but with space requirements, and the existing wiring, I thought that was a bad idea. Also, this converter uses the same 725 watts as the original, so I wouldn't need to be concerned with all my other AC loads, nor the circuit breaker being adequate.

There is no pendant for this new converter. It's a fairly dumb device - it holds voltage and drops the amperage as the battery approaches full. I'm not an electrical engineer, so I can't explain how that works exactly, nor is it described in the manual. Stark does recommend this charger for their batteries. Smart Battery has a littany of chargers they recommend and sell, but from what I can gather, they all work the same way.

[markopolo]

Originally Posted by booster

I would think you would have to use a Trimetric.

Just wondering if anyone has contacted Bogart Engineering to ask if their Trimetric units are suited for use with lifepo4 batteries. I scanned their site but didn't see any specific mention of lithium batteries. I don't know if the battery chemistry matters or not with their units but it would be nice to know what the company says about it.

[wincrasher]

I looked at those. I don't think the chemistry matters.

What you need is a shunt on the negative cable. It connects across that. Don't quite understand then how it accounts for the charge from the alternator.

I searched amongst my wiring to see if there was an existing shunt, and I couldn't find one.

[eric1514]

Your new converter supplies 14.6v DC even without a battery installed. Obviously, you would be running your 12v appliances with the battery filtering that output, but say something went haywire and that battery wasn't there. Would that 14.6 volts harm anything like lights, furnace, the transfer switch, etc.?

[wincrasher]

That I don't know. But if you notice, when the van's engine is running and the converter is unplugged, you get anywhere from 14.0 to 14.4 volts in the coach 12v system.

[eric1514]

Good point. Let's all hope those batteries come down in price significantly in the next year.

[markopolo]

Tesaje replaced the AGM batteries in his Leisure Travel Van with LiFePO4 batteries from Smart Battery early in 2014. Link: The Arleth Adventures: Electrical

He did many upgrades to the van. I only just found the blog while googling Trimetric and LiFePO4. This paragraph was interesting - I couldn't find any followup to it though.

Quote from the blog:

My trimetric battery monitor shows the AH used after being off charging but while charging, it reverses and shows far fewer AH without me resetting it. That is, I use 150AH but when the batteries are full after a charge, it shows 4AH an hour or so after it is done. I guess it is measuring the deficit from full. I never saw that with the AGMs.

[wincrasher]

Interesting reading. Unfortunately his blog abruptly stopped not long after that post.

[booster]

The Trimetric probably was having problems because of something in the lithium like a full shutoff of charging when full, or wrong settings. They may be ways to program around that.

Normally, the Trimetric would measure the amp hours out of the battery without any modifier, so that makes sense, and it would be accurate. In recharge mode, it takes into account programmable charge efficiency to account for the fact you get less ah recovered in the battery compared to what you put in, so that reading of amp hours could be off based on the programming.

I think the problem is probably showing up because of the Trimetric does a calculation based on programmable readings of what it sees when the batteries get full. To be considered full, it has to reach a set voltage for a time, a minimum amps for a time. Very similar to how a return amp charger knows to go to float.

Once all these are met, it will illuminate the "charged" light, but it will still show whatever amp hours and % charge that it ran up while charging. Once you start to discharge the batteries, it will reset the % full and amp hours used to 100% full no amp hours used. This confuses a lot of folks as it doesn't happen right away, it happens at something like 12.7 volts.

That is probably what is happening in the case mentioned, and it could be messed up even more if the batteries totally shut off charge.

As mentioned, the Trimetric measures the current in the negative battery cable by using a shunt. As long as there are no connections between the shunt and the battery, it shouldn't care what kind of battery it is, as it just measures current.

[wincrasher]

Just as a follow up, I let the battery charge overnight on the converter.

When I went out to the shop to check on it, the guage still reads 14.5 volts. The charger was warm to the touch. The battery was not warm at all - felt room temperature.

I pulled the power plug and turned the battery disconnect switch, so it will sit dark until the next time I use the coach.

I'm undecided if leaving the shore power connected and the converter activated is a good idea or not.

[markopolo]

Ask Smart Battery if it is OK to to leave the battery on a 14.5v or so charger for extended periods. You need to know in case you're ever at a campground plugged in for a few days or a week etc.

[wincrasher]

I'm sure they'll ask me how many amps are flowing. It should be next to nothing.