Lithium vs AGM..... the weight discussion

[Troutboy]

Okay,

I've read a lot and learned a lot from everyone on these forums (thanks!). I know this topic has been discussed over and over, but I am having a hard time seeing much of a weight advantage from lithium as people tend to state. I did the simple math based on a table from AM solar. Table as follows:

https://static1.squarespace.com/stat.../?format=2500w

I am looking at extended dry camping so looking for 400 amp hour useable storage. According to the table, four of the lifeline AGM will net 420 amp hours ( after parallel and series connection and 50% discharge max), 66 pounds each, for total weight of 264 pounds.

For lithium, using Victron from same table, one way would be three 160 amp hours, for 3x160x0.8 = 384 amp hours, close enough (80% depth of discharge), Weight of 73 pounds each, or 220 pounds. So 220/264 = 83%. So there is a 17% difference, is it worth the extra cost? I guess that depends on each person and how you calculate life cycle cost.

I know there are other advantages. But my main concern was the weight, and not sure 44 pounds in weight saving is worth the extra cost.

Am I wrong on this analysis? Missing something? Maybe at the higher amp hours, the advantage is less?

I think I will stick with the lifeline AGMs, as I can get 4 from a local dealer for $1200.

Could go with four crown AGM for about $800, but hear great things about lifeline. Anyone use the crown AGM?

If I am missing something here, please let me know.....






Thx
Troutboy, aka Rich

[fran&frank]

I think your calculations are wrong for amp hours on the AGMs--I think you need twice as many as you estimated. Each pair of 66lb 220 Ah 6 volt batteries connected in series will give you 12 volts and 220 Ah; connect these two sets in parallel and you have 12 volts and 440 Ah, but allowing for 50% discharge your back to 220Ah.

[Troutboy]

Ahhh. That makes mor sense, thank you! I was doubling up on the volts!


Thx
Troutboy, aka Rich

[Troutboy]

So if I went with two of the Victron 160, it would be 2x160x.8= 256 amp hours, at 146 pounds, versus the four AGMs for 220 amp hours, at the 264 pounds. So 146/264=62%. So the batteries compared in this case give more amp hours, at 38% weight.

Thanks again!


Thx
Troutboy, aka Rich

[lewster]

Originally Posted by Troutboy

Okay,

I've read a lot and learned a lot from everyone on these forums (thanks!). I know this topic has been discussed over and over, but I am having a hard time seeing much of a weight advantage from lithium as people tend to state. I did the simple math based on a table from AM solar. Table as follows:

https://static1.squarespace.com/stat.../?format=2500w

I am looking at extended dry camping so looking for 400 amp hour useable storage. According to the table, four of the lifeline AGM will net 420 amp hours ( after parallel and series connection and 50% discharge max), 66 pounds each, for total weight of 264 pounds.

For lithium, using Victron from same table, one way would be three 160 amp hours, for 3x160x0.8 = 384 amp hours, close enough (80% depth of discharge), Weight of 73 pounds each, or 220 pounds. So 220/264 = 83%. So there is a 17% difference, is it worth the extra cost? I guess that depends on each person and how you calculate life cycle cost.

I know there are other advantages. But my main concern was the weight, and not sure 44 pounds in weight saving is worth the extra cost.

Am I wrong on this analysis? Missing something? Maybe at the higher amp hours, the advantage is less?

I think I will stick with the lifeline AGMs, as I can get 4 from a local dealer for $1200.

Could go with four crown AGM for about $800, but hear great things about lifeline. Anyone use the crown AGM?

If I am missing something here, please let me know.....






Thx
Troutboy, aka Rich

The second poster is correct! If you are considering a 400 amp/hour usable battery capacity, you will need 800 amp/hours of total AGM capacity as you only get to use 50% of that number. Lithiums give you 80% of total capacity.

To get a total of 400 amp/hours of USABLE capacity , you need 500 amp/hours of lithiums and 800 amp/hours of lead acids, like AGMs.

Looking at your 3 X 160 lithium pack, you will indeed have a total of 480Ah with 384 usable. This lithium bank will weigh 220 lbs.

Using 6VDC AGMs, connecting a pair in series will give you 12VDC at the rated capacity. For Lifeline GPL-4CT, this means 2 will give you 220 amp/hours at 12VDC. 4 will give you 440 amp/hours at 12VDC and 6 will give you 660 amp/hours at 12VDC with corresponding usable capacities of 110, 220 and 330 amp/hours and weights of 132, 264 and 396 lbs for the respective AGM banks.

So...... a 660 amp/hour AGM bank comprised of 6 X GPL-4CT Lifeline will weigh 396 lbs and provide you with 330 usable amp/hours. A 480 amp/hour Victron lithium bank will weigh 220 lbs and give you 384 usable amp/hours.

Big difference!

[wulfraat]

If you need that many amp hours of battery storage / usable energy you have 2 choices:

1. Keep your airstream and add lithiums

2. Ditch the airstream and buy a late model Newmar diesel pusher King Aire coach and load it up with 500+ lbs of lead acid batteries

[Troutboy]

Lol .... I meant I needed the 220. I'm gonna stick with the airstream. That many lead acid batteries might classify me as a moving bomb or something....

Thanks Lewster. How much difficult is the lithium install. I see you need a BMS, and that Orion DC-DC converter. What does the Orion actually do?

Also, do you need the cold weather disconnect?

I also noticed that all the Victron Lithiums batteries are sold out..... what is the typical wait time to get them in?

Thanks!


Thx
Troutboy, aka Rich

[sgschwend]

There are higher current density lithium ion battery chemistry. That will lower the weight per battery again.

[lsbrodsky]

The way the Lithium BMS works, you need to isolate the chassis ground from the battery ground. The Orion is a DC-DC converter that allows you to power your DC distribution with the negative connected to chassis ground. I installed my system before the cold weather disconnect was available and rationalized that I have a cold weather sensor for the inverter/charger but not the truck alternator or solar. My trailer sits in the driveway in the winter and solar cannot exceed the .05C of the battery bank; I can disconnect the batteries or pull the alternator charging fuse if I haul the trailer in freezing weather. But, if you are going to use your trailer in freezing weather, the cold weather disconnect seems like a good idea. Oh, the install is not trivial.
Larry

Originally Posted by Troutboy

Lol .... I meant I needed the 220. I'm gonna stick with the airstream. That many lead acid batteries might classify me as a moving bomb or something....

Thanks Lewster. How much difficult is the lithium install. I see you need a BMS, and that Orion DC-DC converter. What does the Orion actually do?

Also, do you need the cold weather disconnect?

I also noticed that all the Victron Lithiums batteries are sold out..... what is the typical wait time to get them in?

Thanks!


Thx
Troutboy, aka Rich

[lewster]

Originally Posted by Troutboy

Lol .... I meant I needed the 220. I'm gonna stick with the airstream. That many lead acid batteries might classify me as a moving bomb or something....

Thanks Lewster. How much difficult is the lithium install. I see you need a BMS, and that Orion DC-DC converter. What does the Orion actually do?

Also, do you need the cold weather disconnect?

I also noticed that all the Victron Lithiums batteries are sold out..... what is the typical wait time to get them in?

Thanks!


Thx
Troutboy, aka Rich

Larry is correct about the Orion's use. As for the automatic cold weather disconnect, you can now get one for AM Solar's 'Essential' lithium system as well, but it is easily accomplished by using the Master system disconnect on the negative terminal.

I also install a 30 amp marine breaker on the positive charge line coming in from the tow vehicle, as you don't always want 14.2VDC charging your lithiums while driving.....especially when you also have solar.

By using both of these disconnects, along with the included solar disconnects, you can easily isolate the lithiums from receiving any charging simply by turning a few switches. This will also allow you to USE the lithiums (down to -4ºF) without charging them to run the furnace and warm up the trailer to a point where you CAN charge them again.

The Essential system sure is easier to install than this one that I just finished!!

[slowmover]

Ratio of post-work beers to number of connections seems high.

[lewster]

YUUUUUUUGE!!!! :-))


Lew Farber

[Violet2060]

Another quick weight consideration...I just finished a Victron AM Solar lithium install and moved the batteries inside under the bed (27FB) which frees up the battery box and reduces overall tongue weight. That may or may not be a concern for you but just something to consider.

[Glenn T]

As I understand it, lithium batteries can be mounted anywhere, so you could possibly mount them somewhere in the trailer over the axles and eliminate some tongue weight.

[Troutboy]

Thanks guys, I will definitely move the batteries inside. It's a 23D. I get the trailer in 2 weeks, so I will be able to see. With the inverter and four AGMs, it's like 300 pounds, mi use 80 from the tongue batteries.

I am wondering what happens to the balance if I but 300 pounds on one side. It will be more wiring, but under the bed might be way to go.

Anyone have thoughts on balance and weight in terms of tow ability if I load it up under the lounge?


Thx
Troutboy, aka Rich

[lewster]

Originally Posted by Glenn T

As I understand it, lithium batteries can be mounted anywhere, so you could possibly mount them somewhere in the trailer over the axles and eliminate some tongue weight.

There are limitations though. The further away batteries are placed from high amp items like inverter/chargers, the heavier gauge cables you need.

Since most 2000 watt inverter/chargers that I install (Magnum and Victron) specify 2/0AWG cable up to 5' and 4/0AWG from 5' - 10' and DOUBLE 4/0 above 10' to 15', you are talking about some really big cables.

Go up to a larger unit like a Magnum 3012 hybrid and the cables increase to 4/0AWG minimum to 5' and DOUBLE 4/0AWG above that to 10'.


Lew Farber

[gecko]

Hi Troutboy--

First of all, Lew is the man on this subject!

We also dry camp in our 2009 28' International Ocean Breeze, and we set ourselves up initially with four 6volt AGM's. (My understanding is that 6 volts last longer for dry camping, as they are better suited to deeper discharge/recharge). This gives us a total of 440 amps, of which 220 are usable. We have found this to be adequate, with 270 watts on the roof, for dry camping from March-October, even with a 2-3 consecutive days of overcast.
We have not changed out the factory converter/charger, but we do have a BlueSky MPPT solar charger, which Lew says is what has most likely saved our batteries from our three months of shore power hookups each summer--the factory Parallax converter/charger is a one stage battery killer. We have been through 8 full seasons with the Lifelines so far.

But oh my they are heavy! The Airstream 28's are notoriously one of the heaviest (if not the heaviest) in tongue weight. We have two of the batteries in the battery box (built 1" higher to accommodate) and the other two under the short leg of the "L" shaped gaucho int the front of our coach. This gives a very small distance among the batteries, (best to have short leads) but it also (a) puts the second pair of batteries quite far forward (just the other side of the front wall from the battery box) and (b) off to the side, to get to your question. To relocate all four farther aft (under the front of the bed, for example, to get close to the axles and get weight off the tongue, would be prohibitively pricey according to Lew, as all of the electrical leads come to the charger/Converter located in the front of the coach and would have to be-routed, so not a practical solution.)

We have therefore setup with Lew to install a 300amp Lithium bank to replace the AGM's under the gaucho and the two in the battery box. This should reduce the weight of our battery bank from about 280 lbs to about 85lbs, and take almost all directly off the tongue (well, it's not quite all the way forward, but close. They will still be off center, but the roughly 140 lbs of the off center AGM's will be replaced with roughly 85 lbs of lithiums, so that should help, too.

Lew is going to do a master shutoff for us to separate the lithiums from the solar for winter storage in Southern California (temps sometimes get into the high 20's at night where the AS is stored.)

I have no doubt that the finished product will be lighter, and that it will look great, as all of Lew's finishes do.

[Troutboy]

Thanks for sharing Gecko, sounds like a sweet new setup. I like the idea of one of those 300ah lithiums. I live in Colorado, so maybe after a few seasons of the AGMs, I'll take the trailer up to Oregon when a Lewster is there, and have him swap out for the lithium!

Do you already have the lithium 300? What is the order lead time on that deal?

Please let me know how that mod goes.


Thx
Troutboy, aka Rich

[ghaynes755]

A bit lighter with more power, the Elite Power Solutions 200ah pack is 55#.

[55AS]

Originally Posted by Glenn T

As I understand it, lithium batteries can be mounted anywhere, so you could possibly mount them somewhere in the trailer over the axles and eliminate some tongue weight.

You can do this with AGM's as well.