Battery - Flooded and LiFePo4

[gpounder]

I bought a lot of 8 LiFePo4 batteries to create a 12 volt 560 ah set at an amazing cost of $1384 including the BMS.

I did this because I could, noting I am somewhat of a battery geek. I am a fan of flooded batteries and still have a good set of GC2's rated at 690 AH.

Lithiums have some negative features. Your not supposed to store them at 100% all the time. I have 400 watts of solar on the roof too. I plug in during the winter and use solar charger in the summer during storage. We do a number of boondocking trips each year.

I am thinking of locating the new Lithium batteries in the space behind the drivers seat and the slide-out. It happens to be real close to the battery compartment and keep the flooded set. Now you are thinking I am crazy and maybe that is true.

If I do this I can switch sets on or off as needed.

Pros: The Lithium will do better in moderate temperatures. I will have huge battery capacity (80% of 560=448 and 50% of 690=345) for a total of 793 ah.

Cons: I must manage charging by changing the charge protocol on the Magnum. If the sets are well depleted I will need to run the generator potentially for 10+ hours (charger is 125 amps)

Anyone else operate two dissimilar sets.

[theoldwizard]

Originally Posted by gpounder

Lithiums have some negative features. Your not supposed to store them at 100% all the time. I have 400 watts of solar on the roof too. I plug in during the winter and use solar charger in the summer during storage.

Never heard this !

Check out this YouTube Channel - DIY Solar Power with Will Prowse

Also check out this forum - DIY Solar Power Forum

[gpounder]

Originally Posted by theoldwizard

Never heard this !

Check out this YouTube Channel - DIY Solar Power with Will Prowse

Also check out this forum - DIY Solar Power Forum

Thanks for the links, I have seen many of Wills videos.

About 6 years ago I installed my own 6KW solar system and added an off grid battery system for the house.

[gpounder]

Originally Posted by theoldwizard

Never heard this !

Check out this YouTube Channel - DIY Solar Power with Will Prowse

Also check out this forum - DIY Solar Power Forum

Here is a link regarding not storing the battery at 100% and why.
https://www.solacity.com/how-to-keep...tteries-happy/

[theoldwizard]

Originally Posted by gpounder

Here is a link regarding not storing the battery at 100% and why.
https://www.solacity.com/how-to-keep...tteries-happy/

I am not sure what you read but here is what I saw

The very low self-discharge rate makes it easy to store LFP batteries, even for longer periods. It is no problem to put a lithium-ion battery away for a year, just make sure there is some charge in it before placing it in storage. Something between 50% – 60% is ideal, that will give the battery a very long time before self-discharge brings the Voltage close to the danger point.

IMHO the following applies to ALL batteries !

If you need to store batteries for longer periods, be sure to simply disconnect all wires from them. That way there can not be any stray loads that slowly discharge the batteries.

Even lead acid. For lead acid they should be "topped off" about once a month if in storage. Continuous trickle charge for months on end actually will shorten the life.

[bigchick]

as far as the question of changing charger settings to maintain two dissimilar battery banks, why not just get a second charger and dedicate one to one bank, the second to the other bank. no charger settings to change.

[gpounder]

Originally Posted by theoldwizard

I am not sure what you read but here is what I saw



IMHO the following applies to ALL batteries !



Even lead acid. For lead acid they should be "topped off" about once a month if in storage. Continuous trickle charge for months on end actually will shorten the life.

Yes lead acid need to be topped off to prevent sulfication.

But it turns out Lithium have a different problem when either fully charged or discharged. Here is the quote from the article as to why. Do a search and you will find many posts that also say the same thing. Haven't you ever heard not to keep your cell phone at full charge.

"We talked about how LiFePO4 batteries work: They move lithium ions between the electrodes. It is important to understand that these are actual, physical particles, that have a size to them. They are yanked out of one electrode and stuffed into the other, each time you charge-discharge the battery. This causes damage, in particular to the carbon of the negative electrode. Each time the battery gets charged the electrode swells a bit, and each discharge it slims down again. Over time that causes microscopic cracks. It is because of this that charging to a little below 100% will give you more cycles, as will discharging to a little above 0%. Also, think of those ions as exerting “pressure”, and extreme State-Of-Charge numbers exert more pressure, causing chemical reactions that are not to the benefit of the battery. That is why LFP batteries do not like to be put away at 100% SOC, or put into float-charging at (near) 100%."

[gpounder]

Originally Posted by bigchick

as far as the question of changing charger settings to maintain two dissimilar battery banks, why not just get a second charger and dedicate one to one bank, the second to the other bank. no charger settings to change.

Good point.
I have the classic set up whereby the inverter is also the charger so I still must manage it by turning off the charger if on the lithium set. I also know even at 125 amps this is a low charge for the lithium that can be charged as high as 560 amps, even if I go conservative at 50% it is still 280 amps. That would require a 4000 watt charger that I don't think is made for 12 volts and would be real costly.

Part of the advantage of lithium is it can be charged at a much greater rate and that means less hours running the generator but as stated the standard charger is not really big enough to fast charge even a small battery set. Say you had 3 100ah batteries or 300ah total, most inverters are 100 amp max or just 30% charge.