LifePO4 3.2V Batteries vs. "Drop in Replacements"

#1
Hey guys, starting to work on the details about our eventual house bank. I know we live ok with our 6 6V Trojan T125's on our boat (675 amp hours) but am considering lithium batteries for the new RV. I looked into the Battle Born drop in replacements and they seem like a nice option but would need 4 of them, so almost $4k for batteries. So, I started to do a bit more looking around and found these https://www.electriccarpartscompany.com/Fortune-100Ah-Aluminum-Encased-Battery. So I would need 16 of them and the related BMS and balancers but would come in around $3k. So, anyone know what magic happens in the "drop in replacements" that allow them to be charged with wet cell chargers? Can I replicate this with the 3.2V batteries?
 
#2
Get on Alibaba and get some quotes for an EWT 100aH lithium battery, its what Renology rebrands for their 100aH LiPo.. they are basically same as a BB about $500 a pop, shipping fees are a few hundred dollars tho so in the end I'd of saved like $100-150 bux for a single battery and had virtually no warranty.. but if I needed 4 of em, thats the direction I'd of gone.

https://www.alibaba.com/product-det...pm=a2700.7724857.normalList.34.182349bbEJRgpy
 
#3
Thanks for the tip. I did talk with Renogy about their batteries. Tech support told me I should size my new lithium bank the same as my current wet cell and should only discharge the batteries to about 40%. Then if I accidentally fully discharged the batteries they would be "locked up". Not sure about that as I have never heard that. So I decided if that support person was correct then the batteries they were selling were a bit strange. And if the support person did not know what they were talking about, well then not sure I would want to spend that much money on those batteries.
 
#5
as stated Renogy just slaps their name on it and sells em, they dont know wtf they are talking about.. Ive read good things about the EWT batteries.. for the *more affordable* lipos, everyone uses same cells internally it seems.. the only difference being BMS they put on em.

My setup I use a LVD hooked to a Victron Battery Monitor, it disconnects my lithium battery at 20% SOC.. I have a parallel switch that over-rides the Battery Monitor and lets me get another ~15AH of reserve consumption, then the voltage drops below 12V and the LVD hard disconnects to save the battery with ~5% left in it.. and the internal BMS is supposed to shut it all down before it fatally damages the cells..

From what I understand, discharging it to 20% SOC has no adverse effects.. you can go higher at the exchange of cycles (which is still many times more than lead), but wont do any fatal damage unless you run em completely flat.. the internal BMS was not 'safe' enough for my use, so I put more layers of protection on em.. its kinda weird to get to 50% SOC and still having 30% capacity usable, its quite a paradigm shift.. but I overbuilt so I've yet to see it get below 40% in the field with our use.
 
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#6
Thanks Joe for the link, I actually was on the phone with the company they bought their batteries from today asking a lot of questions. They seem to sell some reasonable systems. One of my ideas with the lithium was reduced size and weight of the battery bank. Since we will likely move off the boat into this RV available space is important.

Dreadlocks, I agree about Renogy's support. I have never read or heard a recommendation like the one given to me about lithium batteries. Would make for an extremely expensive battery bank. Research continues as I still have some time before the batteries are needed.
 
#9
yeah lithium is still friggin expensive :(

weight was why I paid for it, my rig is a toy hauler.. batteries basically gotta be on the tongue and a lead system of same capacity woulda been too much since I'm already pushing it.. ~130lbs vs ~30lbs

If I had the space/weight capacity, I'd of likely gone with 4x lead batteries and had more electrical capacity for less money.

With 400aH of Lithium your not going to be able to enjoy the quick charging capability either, going to take 150-200A of charge capacity to top off quickly.. tha'd overload the lil gensets like a <2000w and require far more solar than you have roof.. not to mention cost of such a system.. so if your going to be slowly charging it, and weight/space is not at a premium on your rig.. then the old tried and true lead is hard to beat, despite the serious advantages of lithium.

Kinda a sweet spot for 1 battery systems and lithium right now, lets you do stuff that requires a much bigger lead bank of equivalent cost.. like charge w/very large solar setup, and use large inverters intermittently.. since you can charge back up in a fraction of the time, the storage capacity can be reduced.. I'm perfectly happy with 100aH of lithium and running my genset for a little bit a day, otherwise I'd be looking at 300-400aH of lead so I could just give it a full recharge when I reach shore power instead of running a genset for 10-18h solid.
 
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#10
As long as you keep the battery bank perfectly balance, and use an overvoltage relay that can disconnect your charging source, you can charge it with any charger. The BMS will be like a deadman switch to stop charging if something fails. You mention you will be getting balancers, thats what I use on my 110ah lifepo4, I even bought the balancers from electriccarpartscompany.
active balancers.jpg

On my system I charge it from my 240 watt solar panel/20 amp ecoworthy mppt. I set the controller so it shifts to float when the battery reaches a certain voltage. When on float it charges at less then an 1 amp. I could set the float so low that it would be charging at 0 amps. I have an overvoltage relay that will disconnet the solar panel if the battery voltage gets too high (but you can have it disconnect any other charging source). As long as the battery is in perfect balance, you can leave the battery connected all the time. Its been months since I had to make any adjustments to the controller voltage. Before the active balancers I never let the battery connected all the time, I had to make constant adjustments to the controller every few hours. The overvoltage relay you can set to something like 14.4 volts, if the battery voltage reaches 14.4 volts, it will trigger a relay that will disconnect the power going into the battery. In my system I use a 30 amp relay but you can use much larger relays that can handle 100's of amps.
I got my system so fine tuned that the mppt controller is doing all the charging, when the battery voltage is high enough it trickle charges it the rest of the day, I get to 100 percent almost every day. I have a coulombmeter that counts amps I use against amps I put back in and it always shows a full charge, no more guessing like with lead acid.
diagram a.jpg
 
#12
Thanks JonyJoe101, that was the info I was looking for. Looks like the electric car company has all the needed parts.

Joe, what you mention about lead acid batteries is pretty much our experience over the last 20 years living with them. We pretty much count on 2 years for our battery bank before planning on replacing them. This is full time use with quality charging systems and not letting them get below 50%.
 
#15
Building your own lithium bank from loose cells is fairly involved. There are some units that have a BMS, but you need to set it up and use your own disconnect relays etc. Drop-in is not really true, as you need to configure your system for the lithium batteries properly.

What made you decide you needed 4 battleborn batteries? The reality is that a lithium bank never needs to be more than half the rated AHs of the lead bank its replacing. This is due to larger usable capacity, more efficient charging, and higher energy storage per AH.
 
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