GC2 ti LiFePO4

[agesilaus]

OK I have a bank of 4 GC2 batteries and I'm thinking about replacing them with Lithium.

Each battery is rated at 225 a/h. A Li battery is 100 a/h. Do need 2 Li to replace each GC2 or 2 Li per pair of GC2?

I'll need a new converter for Li. And maybe a new solar controller.

Any help much appreciated.

Edited November 9 by Kirk W
Changed text color to black

[ogaddcb]

What happened in your original post.  Looks like all the sentences after the first one are faded out.

I am not an expert. My assumption is that wiring of the 4 GC2 batteries was a set of two GC2 batteries wired in series and then these two in series were wired in parallel to equal 12 volts and 450-amp hours. Conventional theory is that lead acid batteries should not be discharged below 50-60% so in theory to avoid damaging the batteries the is 225-amp hours.

I had to replace my two T-105 6V Deep Cycle Golf Cart Batteries. When boondocking with the T-105 I would try to run the microwave, and the inverter would shut down because the batters would drop below 10.7 voltage required by the inverter.

I had to go with two lifepo4 because the BMS (battery management system) would allow only 100 amps dump of current. When boondocking the microwave running via the 2,000-watt inverter would draw 120 amps. In addition, the (BMS) has both low/high temperature shutoff.

I have not replaced my OEM inverter. Which means that when plugged into shore power the inverter will not charge the lifepo4 to 100%.

I do not have a DC-to-DC charger. My truck has dual alternators, so it sends 14.3 volts and 20 amps down the 7 pen so when driving I do charge the lifepo4 at the recommended rate.

I have changed my ancient MorningStar ProStar MPPT to charge the lifepo4 at the recommended rate.

The conversion to lifepo4 has meet requirements but can get very expensive very fast.

[Kirk W]

I suggest that you visit Heiser RV Solar & Electric for some information. With any luck, Chad will see this and join in. While I have a lot of experience with wet cell batteries, my lithium battery experience and knowledge is pretty limited.

[oldjohnt]

 Good morning ag, Without going too deep in the weeds and all the techy stuff and figuring your needs and energy storage capacity on and on and on (too much for here) and having evolved over MANY years from Lead Acid to RV Marine to Deep Cycle to AGM then Lithium, I will only say: If I were starting all over ID USE EPOCH LITHIUM BATTERIES with of course a good BMS with low temp protection and maybe even internal heaters???  (if cheaper maybe go SOK, many prefer Battle Born). The voltage, amp hours, size etc depends on your needs. Also, Id opt to use Victron for most other components (charge controllers, inverter/chargers, DC to DC Chargers, Monitors, etc) They can all talk bluetooth to each other while Epoch can communicate with Victron also. Ive also used and had good luck with brands such as SOK and Renogy, they may be a bit cheaper than Victron but all worked great.

EXPENSE:  Of course your chargers and other equipment need to be LITHIUM compatible, THIS ISNT CHEAP 

YOUR QUESTIONS: 

1) A Li battery is 100 a/h. Do need 2 Li to replace each GC2 or 2 Li per pair of GC2?

Its not good to discharge Lead Acid over 50%, while you can discharge deeper with Lithium, so in broad general terms a 100 AH Lithium could replace 200 AH of Lead Acid BUT THATS NOT A PERFECT EXAMPLE 

2) I'll need a new converter for Li. And maybe a new solar controller.

  YES your converter/charge needs to be Lithium compatible for best performance and again YES your solar charge controller likewise.

NOTE if you need a new converter/charger, I would opt for a Combination Pure Sine Wave Inverter/Charger  

NOTE: DC TO DC Instead of using any wimpy low current capacity 7 pole round connector to let the alternator charge Lithium house batteries I HIGHLY RECOMMEND A DC TO TO DC CHARGER suitable for Lithium using heavy cables and an Anderson connector 

NUFF SAID for now, this is ONLY very preliminary you need to figure your needs then design the system. If you' have more questions we could go one step at a time this is ONLY a start of my personal recommendations, see what others advise AND CHECK OUT DIY SOLAR BY WILL PROWSE ON YOU TUBE he's very good.  I do a lot of dry camp boondocking and my solar investment is the best thing I ever did and Im never going back 

 

John T  Electrical Engineer but NO Solar Expert, so check the other fine gents here and Will Prowse 

 

 

[Lou Schneider]

Most 12 volt 100 a/h lithium batteries use a Group 27 case which is 2" longer than the GC2.  If the physical size is a problem several manufacturers make a "mini" 100 a/h that uses the Group 24 case which is similar to the GC2 in both length and width.  The main difference between the Group 27 and Group 24 "mini" batteries is the latter has less dead space between the battery cells and the ends of the case. 

You can also get 200 a/h and even 300 a/h 12 volt batteries which are essentially two or more 100 a/h batteries in a single case so you only have a single point of connection.  12 volt lead acid batteries of these sizes are too heavy to lift, LiFeP04 batteries are much lighter.

The "cheap" 100 a/h batteries are getting surprisingly good reviews including by Will Prowse who tears them down and inspects the internals.  They have become commodity products with little difference between brands.  The LiTime (formerly Chins) 12 volt 100 a/h "mini" battery has very good reviews and is currently selling for $230 on their website, $20 less than their Amazon price.  There are also several for less, the cheapest selling for $170 on Amazon.  Again, check with Will Prowse on YouTube to see if he's reviewed them.

If you get multiple 12 volt batteries you'll have to wire them in parallel, not series (+ to + and - to -) so if you get 4 batteries you'll need a couple of more battery cables.

If you have a multistage converter that gets it's voltage up to 14.5 volts during the charging cycle or another means of charging these batteries up to that voltage your existing setup will work just fine.  A converter that only puts out 13.5 volts will eventually (overnight) get them to about 85% of a full charge and you can make up the rest from another charging source like solar or the vehicle's alternator. 

You do need a shunt based battery monitor to keep track of the battery's state of charge.  These run from $50 -80 for a wired version to $200 for the Victron wireless one that displays the parameters on your cell phone.  A voltage based monitor won't work as there isn't enough voltage change between 80% and 20% SOC for any kind of an accurate reading.

Edited November 10 by Lou Schneider

[Randyretired]

As others have said you currently have 450ah but should only use around 50%, so 225ah.  Lithium can be drawn down to 0% but many prefer to plan on 20% as a dead battery can cause problems.  If the current batteries easily covered your needs you can probably get by with 200ah of lithium.  If not you may want more.  Lithium batteries are available in larger sizes if needed.  I have seen 12v in sizes up to 460ah and larger.  I built a couple of 608ah for our RV.  200ah lithium batteries are widely available. Changing everything to charge Lithium can be expensive but maybe some things can wait.  Lithium typically require higher voltage to fully charge but if it isn't necessary for everything to fully charge for your use a partial charge may work now and again.  Lithium doesn't need to be fully charged like lead acid.  In fact it will last longer when stored at less than 100%.  However, for balancing Lithium needs to be fully charged at least monthly during use.

[oldjohnt]

2 hours ago, Randyretired said:

I have seen 12v in sizes up to 460ah and larger.

Hey there Randy, X2  Epoch makes a 300 AH and a 460 AH in 12 Volts I believe. Battle Born Game Changer 12 Volt are 270 AH. Lots of gents are going away from the early 100 AH Drop Ins (sized to fit in regular battery boxes) to bigger singles instead of having to parallel two or three with all those extra connections. Instead of our discrete Chargers, Inverters, Batteries and MPPT Controllers for Solar Inputs and DC to DC connection capability, some moderate to big energy users are going with the all in one units    THE TIMES THEY ARE A CHANGING  !!!!!!!!!! Wish I was young and starting all over but my SOK's, Renogy and Progressive Dynamics units are workin great even though I paid much more then versus todays prices grrrrrrrrrrrrrrr 

 John T

[Randyretired]

Good points John.  Things are changing fast.  Battery prices have come down, the new hybrid inverters combining inverter, chargers and charge controllers are sometimes cheaper than either one item just a year or 2 ago.  Solar panel prices have really dropped.  I am building a solar setup for our off grid property.   Twenty new 400 watt bifacial solar panels shipped for $136.  A couple of months later the price dropped $15.  3 years ago 285 watt used panels were $85.  The technology is also changing.  The 400 watt panels will be wired with 10 panels in series producing around 400v to the hybrid inverter.  

[GlennWest]

I am using the all in one units. 2 EG4 6500. Not the first grip about them. Working great. May upgrade my batteries later. They are getting very reasonable. I still using the leaf cell paks.

[Chad Heiser]

On 11/8/2024 at 6:14 PM, agesilaus said:

OK I have a bank of 4 GC2 batteries and I'm thinking about replacing them with Lithium.

Each battery is rated at 225 a/h. A Li battery is 100 a/h. Do need 2 Li to replace each GC2 or 2 Li per pair of GC2?

I'll need a new converter for Li. And maybe a new solar controller.

Any help much appreciated.

Your current battery bank has a total amp hour capacity of 550.  For the longest life on those batteries, you don't want to drop below 50% state of charge very often so that gives you a useable capacity of 225 amp hours from your four GC2 batteries wired in series/parallel to make a 12 volt battery bank.  If you want similar battery capacity from a lithium battery bank, two 100 amp hour lithium batteries wired in parallel will give you basically 200 amp hours of available capacity.  This is because lithium batteries can use all of their capacity without harming the battery.  Realistically, you don't want to draw the batteries all the way down to 0% so I would say a minimum of three 100 amp hour lithium batteries would easily replace your four golf cart batteries.  You could also consider going with one or two larger capacity lithium batteries.  A couple of 200 or so amp hour lithium batteries would have a slightly smaller footprint than your four GC2 batteries and give you quite a bit more capacity.

You didn't mention what all equipment you have attached to the battery bank, so I will assume you are just powering basic RV loads for now.  To go along with these new lithium batteries, you will want to add a battery monitor like the Victron SmartShunt.  This will give you a very accurate assessment of your battery capacity, usage, etc. in real time.  I never install a lithium battery bank without a battery monitor.  You will also want to make sure your chargers are lithium compatible.  You already mentioned your converter and solar controller.  Ideally you would install a lithium compatible converter and a lithium compatible solar charge controller (assuming your existing ones don't have a lithium setting).  Most lithium batteries can stand to be connected to standard chargers with no detriment to the battery in the short term.  The standard chargers may not completely charge the batteries or properly top balance them over time so ultimately those components should be changed out, but it is not critical that it be done immediately.

If you have any specific questions, let me know.  I just finished presenting on this specific topic (and several others) at a Grand Design RV rally and I am well versed in the RV solar/inverter/battery world.

[agesilaus]

OK guys thanks for the advive. My mouse died and I was off the computer until O found a temp replacement.

my plans unless some says stop:

2 eCOfkoe 100 a.h batteries.

a new converter

some battery heating pads tho I'm putting these in the pass thru which should keep them warmer.

[Kirk W]

16 hours ago, agesilaus said:

My mouse died

         😊

[oldjohnt]

On 11/11/2024 at 5:10 PM, agesilaus said:

OK guys thanks for the advive. My mouse died and I was off the computer until O found a temp replacement.

my plans unless some says stop:

2 eCOfkoe 100 a.h batteries.

a new converter

some battery heating pads tho I'm putting these in the pass thru which should keep them warmer.

It looks like all the fine gents answers were pretty much on the same page, hey thats a GOOD thing !!!!

 

John T