lithium batteries or AGM

[Giannisailing]

hello everyone
I have 1000 AH on my Cat and recently noticed that voltage was dropping very rapidly from fully charged. When inspecting the battery bank I found that one of the 4 batteries was quite warm. Proceeded in disconnecting it and with 750AH the voltage drop was diminished. Nevertheless I think that the bad battery had spoiled the other 3.
The batteries are Deep Cycle AGMs and I think need replacing unless I can improve performance somehow.
I am also planning to install some solar panels. 900W perhaps
What is the general opinion regarding Lithium?
Ive checked some suppliers and have seen 150AH at $560 which looked very competitively priced to me...perhaps too competitively.
What should I look for when shopping for Lithium and, what is the trend now days? replacing AGMs with other AGMs or with Lithiums?

Any tip greatly welcomed.

[travellerw]

Hard question.. No clear cut answers... There are many lithium solutions to fit multiple budgets. The one thing to note, is there are really very few "drop-in" replacements. Going lithium usually means looking at the whole electrical and charging system.

If you have a big budget then Victron has some very nice stuff. If you have a medium budget them there are some companies that offer complete systems using standard cells. If I remember correctly, one company is Elite Power Systems.

If your budget is more limited, then a DIY system with Winston, Calb, Sinoploy or other cells is about the only solution. In that case, you have literally days of reading ahead of you. I would recommend you start reading the RV forums as they have a much bigger install base and better data. However.. Even the cheapest DIY system is going to run you over $6000 for 1000AH.

[Giannisailing]

many thanks for your suggestions....I guess I do have some bedtime reading ahead..haha.
Just one question...1000AH of AGM = 1000AH lithium? or Am I correct in thinking that because Lithium is more efficient in its delivery of its charge it would require less capacity?

[senormechanico]

If you have 1000 aH of AGM, or any other type of lead, you can get an equal amount of USABLE capacity with a much smaller bank of Lithium.
LiFePo4 can be discharged to around 20% remaining without damage.
I've gone down to 23% several times and have had the bank for several years.

You could easily get the same performance with a bank half the size.

[a64pilot]

Lithium is not for the faint of heart, not for someone who wants batteries they install and forget about.
You can waste a whole lot of money if you don’t know what your doing, so do your homework and decide if you want to go down this road

[scotty c-m]

Are there fire hazards with lithium??

[john61ct]

The umbrella term Lithium-ion covers dozens of wildly different chemistries, many of which have safety issues wrt thermal runaway.

LiFePO4 or LFP is not one of them

Only one worth considering for House use in a mobile context.

[john61ct]

Most experts believe the only LFP batts that should be installed on boats are the packaged systems including proprietary BMS protective gear.

These can come out to 7x more expensive than even quality lead.

But if they last for many decades maybe less expensive in the long run.

Right now IMO only sensible for racing yachts where saving weight is worth spending boat bucks.

[john61ct]

> Am I correct in thinking that because Lithium is more efficient in its delivery of its charge it would require less capacity?

More because lead AH delivers 50% usable, LFP more like 90%.

Other huge advantage is very short charge cycle, no need to get to Full (in fact staying there is unhealthy), so little need for solar if you're already burning dino juice a few hours per week.

[john61ct]

Best thread for detailed info:

​ http://www.cruisersforum.com/forums/...nks-65069.html

Maine Sail's notes: http://www.pbase.com/mainecruising/lifepo4_on_boats

If there are any RV forums with quality discussion on LFP, I'd appreciate links.

[john61ct]

Other quality "systems" vendors besides Victron: OceanPlanet (Lithionics), MasterVolt and Redarc (only in Oz?)

[GTom]

There are modern lead batteries with moderate Peukert's effect and long cycle and service life. There are a few things to consider:

Lithium:
+deeper discharge than practically any lead acid on the market, 50+% advantage over the average AGM, ~20%(?) over special deep dischage industrial/solar LA.
+huge weight advantage (especially if equivalent AH-s are compared, like 1kAh LA vs 600Ah LFP)
+fast charging, superior charge retention
-even LiFe(Y)PO4 burns (not as violent as LiPo of course)

Lead-Acid:
+chargers are available for all wind and solar gens
+cheaper
+available everywhere in the world(!). Imagine yourself with that faulty bank issue on a circumnavigation somewhere in Southern Chile...

[travellerw]

Originally Posted by Giannisailing

many thanks for your suggestions....I guess I do have some bedtime reading ahead..haha.
Just one question...1000AH of AGM = 1000AH lithium? or Am I correct in thinking that because Lithium is more efficient in its delivery of its charge it would require less capacity?

This is one of the BIG misconceptions you will find here on this forum. You will get TONS of views saying you can get by with much less. However, spend some time in the RV forums where they have been "boondocking" for years on thier LifePO4 batts and its a different story..

In a very quick sum up.. The RV crowd now believes LifePo4 should not be discharged below %70. Nor should it be charged over %90 (maybe once in a while when you think it will be cloudy and need the extra capacity you can do the %100 - %20). So if you do the math.. That is %60 of the capacity of the bank that is usable. Pretty much exactly the same as modern AGM. Of course these numbers are for maximum life cycles. If you aren't concerned about that, then %100 charge and %20 discharge are an option, but life will suffer (especially in a hot environment like the tropics).

On the flip side.. The lithiums will weigh MUCH less than the AGM. The lithiums also charge faster (you cross zero earlier in the day). Lithiums also don't suffer from as much voltage sag, making some electronics work better (like your autopilot drive if its linear). Lithiums are also happy at any state of charge (you don't need to hit %100 ever).

Again.. A big shoulder shrug... They may be exactly perfect for you, or not. Only you can decide. I really encourage you to use as many data sources as you can to make that descision. The cruising crowd is tiny potatoes compared to the RV or offgrid crowd.

[travellerw]

Originally Posted by john61ct

Best thread for detailed info:

​ http://www.cruisersforum.com/forums/...nks-65069.html

Maine Sail's notes: LiFePO4 Batteries - Thoughts & Musings Photo Gallery by Compass Marine How To at pbase.com

If there are any RV forums with quality discussion on LFP, I'd appreciate links.

Google is your friend.. Also google "off grid living", there is tons of gold there.
Here is a one link to get you started.. This one is already 5 years old (the original post) and they had begun to see the trend.

https://www.solarpaneltalk.com/forum...rging-and-care

[john61ct]

> RV crowd now believes LifePo4 should not be discharged below %70.

I've never seen any such source, credible or not.

Total insanity IMO.

I've never seen any land-based forum with better quality discussions on LFP compared to the sailing ones.

Links please!


Edit

Originally Posted by travellerw

and they had begun to see the trend.

What trend?