I am at the point where I need to replace the 5 year old 6v AGM batteries on my TT so this article was timely. Thanks (again) for the useful information. As someone who got into RV life seven years ago with little knowledge of AC/DC electrical systems you’ve been a consistent source of trusted information and I’ve really enjoyed learning from you.
As Mike has pointed out so well, LFP batteries are hardly "plug and play" or a "drop-in replacement" as many mfrs and vendors claim.
Mike pointed out all of the most important considerations, but a couple others are:
1) Terminals and connections. The terminals on most LFP batteries I've seen -- including the 2 Lion batteries we have -- are ridiculously undersized. 6mm or 8mm threaded inserts are common. Not only are they small, but it is a weak design because the torque placed on the hardware can break the insert loose. They are not meant to accept large cable with 5/16 or 3/8" ring terminals.
The only decent design I've seen are the 'blade' terminals on Battle Born batteries.
We ended up using the posts Lion included that are similar to the posts on ordinary lead-acid batteries. I bought some nice mil-spec battery post terminals The problem was that the Lion posts are perfectly cylindrical, while FLA battery posts are sightly conical. That meant that the contact surface was much smaller than it ordinarily is, but it seems adequate. We used the bolt on each terminal to attach the #4/0 welding cable. The Lion posts have threaded holes on top, which we used to secure the 2 cables to connect the batteries in parallel.
Bottom line -- it took a lot of time and it is not very pretty. It does work and there is no discernable heat at any of the connections when charging at 100A+ (50A per battery). They will start the (small) diesel generator (QD 3200) and even run the AC (13,500 BTUI Coleman). We did that inadvertently...
2) This is small in comparison, but the existing battery hold-down hardware will probably not fit. I had to rig up something with angle iron and all-thread.
3) Oh, and charging LFP batteries may be too big a load for the alternator. Without testing, it's best to disconnect the cable from the alternator to the house batteries. If the alternator is used, a DC to DC is needed, at a cost of several hundred dollar. They are generally limited to 30-40A, or 15-20A per battery, which means a long charging time.
Price of LFP batteries is becoming less of an issue every day. I more worry about if all these battery companies will be around to honor their long warranties (5 year plus). The market might saturate eventually and force a consolidation. Very hard to predict. Here is a link to what appears to be a cheap and well built 100Ah 12V LFP battery for under $200.
I am currently converting my 2016 Winnebago Travato to Lithium iron phosphate and have had to upgrade both the solar controller and converter charger at a cost of less than $200. The batteries are from Renogy and I will pay $620 for 2 100 AH batteries. A 200 AH AGM battery would be over $600. I think that the cost difference is not a factor. It is more about the process. For me the weight difference is big. The batteries are currently just in front of the rear axle. The prospect of wrestling the 120 pound AGM into that spot with all the connections done by feel, out of sight, as opposed to the 2 25 pound Lithium batteries going under my bed where the inverter and DC charger now live, tipped the scale for me. I’m too old to take advantage of the lithium's long life but the increased storage capacity will be a big plus. Appreciate all the information you provide. Just thought the 'expensive lithium' line is a bit dated. Mike ( all Canadian $ )
Two items were mentioned that I don't know what they are : "a super-capacitor is added to provide extra peak current for these situations". What is it added to? And
what is : "Shortstop circuit breaker with a manual resettable circuit breaker".
I am at the point where I need to replace the 5 year old 6v AGM batteries on my TT so this article was timely. Thanks (again) for the useful information. As someone who got into RV life seven years ago with little knowledge of AC/DC electrical systems you’ve been a consistent source of trusted information and I’ve really enjoyed learning from you.
As Mike has pointed out so well, LFP batteries are hardly "plug and play" or a "drop-in replacement" as many mfrs and vendors claim.
Mike pointed out all of the most important considerations, but a couple others are:
1) Terminals and connections. The terminals on most LFP batteries I've seen -- including the 2 Lion batteries we have -- are ridiculously undersized. 6mm or 8mm threaded inserts are common. Not only are they small, but it is a weak design because the torque placed on the hardware can break the insert loose. They are not meant to accept large cable with 5/16 or 3/8" ring terminals.
The only decent design I've seen are the 'blade' terminals on Battle Born batteries.
We ended up using the posts Lion included that are similar to the posts on ordinary lead-acid batteries. I bought some nice mil-spec battery post terminals The problem was that the Lion posts are perfectly cylindrical, while FLA battery posts are sightly conical. That meant that the contact surface was much smaller than it ordinarily is, but it seems adequate. We used the bolt on each terminal to attach the #4/0 welding cable. The Lion posts have threaded holes on top, which we used to secure the 2 cables to connect the batteries in parallel.
Bottom line -- it took a lot of time and it is not very pretty. It does work and there is no discernable heat at any of the connections when charging at 100A+ (50A per battery). They will start the (small) diesel generator (QD 3200) and even run the AC (13,500 BTUI Coleman). We did that inadvertently...
2) This is small in comparison, but the existing battery hold-down hardware will probably not fit. I had to rig up something with angle iron and all-thread.
3) Oh, and charging LFP batteries may be too big a load for the alternator. Without testing, it's best to disconnect the cable from the alternator to the house batteries. If the alternator is used, a DC to DC is needed, at a cost of several hundred dollar. They are generally limited to 30-40A, or 15-20A per battery, which means a long charging time.
Other than that, no problem!
Price of LFP batteries is becoming less of an issue every day. I more worry about if all these battery companies will be around to honor their long warranties (5 year plus). The market might saturate eventually and force a consolidation. Very hard to predict. Here is a link to what appears to be a cheap and well built 100Ah 12V LFP battery for under $200.
https://youtu.be/UDkJ7Sq21Qw
I am currently converting my 2016 Winnebago Travato to Lithium iron phosphate and have had to upgrade both the solar controller and converter charger at a cost of less than $200. The batteries are from Renogy and I will pay $620 for 2 100 AH batteries. A 200 AH AGM battery would be over $600. I think that the cost difference is not a factor. It is more about the process. For me the weight difference is big. The batteries are currently just in front of the rear axle. The prospect of wrestling the 120 pound AGM into that spot with all the connections done by feel, out of sight, as opposed to the 2 25 pound Lithium batteries going under my bed where the inverter and DC charger now live, tipped the scale for me. I’m too old to take advantage of the lithium's long life but the increased storage capacity will be a big plus. Appreciate all the information you provide. Just thought the 'expensive lithium' line is a bit dated. Mike ( all Canadian $ )
Two items were mentioned that I don't know what they are : "a super-capacitor is added to provide extra peak current for these situations". What is it added to? And
what is : "Shortstop circuit breaker with a manual resettable circuit breaker".
The super capacitor is added in parallel with the lithium battery.
I believe the shortstop breaker is slang for a circuit breaker mounted at the battery terminal, but I need to check with Dennis.
Thanks.
also i have a warning from cummins that the K generators are not compatable with lithium batteries. why not?
I’ve not heard about that, but I’ll check with my Cummins contact.