Another Lithium battery question

[twinboat]

Originally Posted by wopachop

. Problem is about half of them still dont understand you cant compare the usable capacity of a flooded 6v battery bank to that of a lithium bank.

.

Why not ?

Has the lead acid battery industry been lying to the world forever ?

[Isaac-1]

It is way more complicated than that, for one thing Lead Acid batteries suffer from the Peukert effect, which means the higher the amp draw the less capacity the battery has. This means a 1 watt draw for 500 hours is not the same as a 500 watt draw for 1 hour, and while LiFePo4 Lithium batteries also are subject to this effect, it is only to a tiny trivial degree. This makes a 100AH usable capacity LiFePo4 battery better than a 100AH usable capacity lead battery for higher amp draw duty, such as powering an inverter. In addition to this LiFePo4 is not subject to voltage sag like a Lead Acid battery is during high amp draw, it also runs at a slightly higher voltage meaning less chance of an inverter shutting down on low voltage during heavy amp draw while the lead acid battery may still be in the 30-50% charge range

[astrnmrtom]

It wouldn't hurt to know a few more details about your set-up. What are you running off the inverter overnight?

My gut-based SWAG is that something is wrong, such as the batteries being shot, or not being fully charged during the day. As mentioned, a battery monitor is a good investment however, the need to be calibrated when installed, and it's important the batteries are fully charged before doing so. One thing it can do even if not calibrated is to show your actual load, and charge rates.

If these are flooded batteries, before you do your clean-up, go purchase a hydrometer. Make sure the batteries are fully charged, then disconnect them from a load and let them "rest" for a couple hours. Take a reading for each cell. This is the only way to determine the real state of charge. If they all still read low, but are fairly consistent in the readings, try charging them with a separate battery charger, rest and test again. This will tell you if it's the charger or the batteries.

You can also "borrow" a load tester from many auto parts stores. Same procedure as testing. Full charge, rest and test.

Batteries should last longer than 3 years, but not always. I had four expensive new AGMs go bad in a little over two years of fairly light use, and that's with a monitor, solar charging, and never running them down past 50% capacity. Biggest load overnight was my residential refrigerator. Batteries can also be killed by deeply discharging and letting them sit too long discharged, especially if they are subject to freezing temperatures when dead. Factory installed batteries are often of not high quality.

Good, luck, and let us know what you find.

[Rocketman3]

I will add my opinion.
Full-time RVer - installed a self-built lithium battery 2years ago.

One issue with the battery you selected MAY be the total amp draw when using your inverter. When I use the microwave on the inverter it can pull about 200 amps from the battery. Make sure your bms(in whichever batteries you select) can handle your max load with the inverter. If one battery can’t handle - you can put two or three or four in parallel.

Recharging… make sure you have at least one recharging source that is ideal for the battery. If your alternator isn’t ideal and your inverter/charger isn’t ideal - get a solar charge controller that is ideal (with an appropriate amount of solar cells). That way your lithium cells get fully charged and can balance occasionally. (Bad things happen if they never get to the balancing stage).

Look at a Victron Smartshunt or BMV712 for battery monitoring now. You will need it when you get the lithiums. It can help figure out problems/issues with your usage.

Find a battery that really fits the space well. I had to diy my lithium battery. I got 544ah in the space of four CG2 batteries. Look at the Lion batteries from Costco (mentioned above).I believe You could have 400ah into less space than you have now.(maybe even more).

Good Luck!

[Pappion]

AGM needs to be fully recharged to avoid sulfur-cation. That can take hours to cover the last 10%.
Years ago I bought special AGM that did not need full recharge. Drawback was it needed about 4.2v to put a good charge in it. They don't make these sizes anymore, never cared for Mobile RV. OUTBACK Power Lead Nano-Carbon, Energy Cell 106NC Nano-Carbon VRLA AGM 106Ah.
https://www.emarineinc.com/outback-p...ano-carbon-12v


Firefly Oasis group 31 110Ah is another that tolerates partial recharge. Popular with boaters, that don't want to expend the diesel running the generator. Not for RV, heat is a problem.

[zoso1971]

Been away for a while, hey guys. I had 6v GC2 in the past at 225AH. If the bank pictured is equivalent it's 450AH max 225AH usable. The 230AH he is looking at has around the same capacity from where I'm standing. Plus all the benefits. Li will maintain voltage under high draw where FLA drops dramatically possibly causing inverter cutout when approaching 50%.


To the OP checkout https://www.litime.com/
They have US distribution and warranty. There are others as well.


- Jeff

[twinboat]

Originally Posted by zoso1971

Been away for a while, hey guys. I had 6v GC2 in the past at 225AH. If the bank pictured is equivalent it's 450AH max 225AH usable. The 230AH he is looking at has around the same capacity from where I'm standing. Plus all the benefits. Li will maintain voltage under high draw where FLA drops dramatically possibly causing inverter cutout when approaching 50%.


To the OP checkout https://www.litime.com/
They have US distribution and warranty. There are others as well.


- Jeff

That's only if you buy into the 50% usable myth. Seems you do.

[zoso1971]

Originally Posted by twinboat

That's only if you buy into the 50% usable myth. Seems you do.

So you can run FLA dead every day dropping the inverter with voltage below 10 for 5000 cycles?

[paul65k]

Originally Posted by twinboat

That's only if you buy into the 50% usable myth. Seems you do.

Originally Posted by zoso1971

So you can run FLA dead every day dropping the inverter with voltage below 10 for 5000 cycles?

Zoso1971, you certainly can run AGMs down to 20%, Twinboat is correct there but with AGM you still have to deal with the following;

• Lower Operating voltage (13.0V fully charged with AGM vs 14.4V W/LiFePO4)
• 1.25 Peukert component (AGM) vs. 1.05 Puekert LiFePO4) - This means much lower operating voltage on high drawdown devices (Coffee Pots, Microwave, hairdryers)
• 20% SOC on AGM is ~ 11.66V vs 12.9V with LiFePO4
• AGMs should be charged back to 100% after deep discharge to alleviate the effects of sulfation...... LiFePO4 batteries are not subject to sulfation
• LiFePO4 batteries have, arguably, 4-10X the # of usable cycles during their lifetime
• Top-tier LiFePO4 batteries (Comparable to LifeLine) come with 3500 - 4000 Cycle warranties
• I almost forgot..... LiFePO4 batteries will charge 2-5X faster than AGM as they are not subject to the Bulk/Absorption long charging cycles as LiFePO4 will charge to 99% in the bulk mode

Other than that AGMs are no different and will do the same thing as LiFePO4 in an RV

[Ludo]

Originally Posted by Captain8

Everyone on here is right, you'll be swapping 400AH to 225AH so will get half the battery you had before. You need 2 of those to get the same and 4 of them to get double.

This is not completely right, the AGM's can only be used down to about 50% SoC, the Lithium (at least) down to 90%.


So 90% of 225Ah is more then 50% of 400, and all is well, he will be exactly where he is right now.


What he will need in any case with Lithium is a good BMV, so I'd propose to at first install a Victron BMV 712 and record the data over at least a couple of days of normal usage of the RV.


With this data a good guess can be made upon the state of the existing batteries and the needed energy, so its possible to decide how to proceed.

[paul65k]

Originally Posted by Mudfrog

Only getting a day out of four big 6 volts is terrible and indicates to me that either there is no rationing of power

Rationing of Power?????......... you must not be married