I’m way out of my league here. I was surprised to find a thread here that dealt with energy storage. The LiFePo4 batteries are still way out of my budget. I know that it’s far from the best option but I can get golf cart batteries from Sam’s Club for a little over a hundred bucks including the core charge. I could afford probably 6 of those. I can seem to find good information about the most efficient way to charge them from a generator or how best to do so in the shortest amount of time. I’m wanting to pull the pin on this fairly soon. Lacking any better information and within my budget constraints I’m looking at one of these
I would appreciate any help or information I could get about the best low cost way to build a system.
There are other RV chargers out there. You can get much larger chargers than the one you found.
If you go 24 volt, this open the range of battery chemistry you can use. You can make Lithium work on just about any voltage. But 24 Volt systems are the closest match in a 7 series set up. Then you can use 24 volt heavy duty alternators direct from engine for charging.
If you can afford 6 of those cells at a 100 bucks a pop, you can afford to go with lithium. Those batteries will be junk in a year if you are hard cycling them. I will never buy lead acid batteries of any kind ever again. Im going on three years off grid and have spent enough wasted money on lead acid. In the long run lithium is the best bang for your buck and are getting cheaper than lead acid.
This right here for $245 bucks gets you 2.2 kW / hours. That is a huge amount of power for that kind of money. This was un heard of even a year ago.
I completely understand, which is kind of why I was looking at other ways they may help, or other places to reduce expenses. I also wasn’t sure what you did have, as the inverter/charger system is expensive as well. and they make LiFeP drop in replacement batteries so you wouldn’t have to change anything if you had an existing LA system. I am not sure they are more expensive, but they definitely have a higher upfront cost. If you figure 300cycles for LA and 2000 cycles for LiFeP, you are already at 600 dollars without factoring the 50% vs 100% discharge or the greater cell efficiency.
There is someone within a 100 miles of here that sells refurbed golf cart batteries. I can’t remember where I saw it. If I see the ad again, I will post it.
I would either opt for used automotive batteries. Those are like 35 bucks.
or buy used lithium cells and build a cell pack. You need a battery spot welder though and be pretty aware of what you are doing, which isn’t everyones cup of tea. It is like a good winter project when you are in your electronics workshop.
When you are shopping for batteries, find out what the “watt hours” are. Take your final cost, batteries plus shipping and then divide by the total “watt hours” This gets you the cost pr watt.
So for example the Dekota LifePo4 cells are 10 amp hours at 12 volts nominal voltage. this only gets you 120 watt hours. They are $109 bucks with shipping to me with out tax. This puts the cost pr watt at $0.90 a watt. That is ridiculously expensive.
The LG Chem pack I just posted is $245.00 plus $350 shipping = $595.00
$595 / 2200 watts = 27 cents pr watt. If you buy more this gets much cheaper as the shipping is flat rate.
worth also chiming in to point out that you can save a boatload (and lower heat/wear and tear) by using a voltage higher than 12v, attractive as it may seem at the outset due to the ubiquity of 12v. Instead, consider aiming for 24 or 48v systems. Simple reasons: a 2000w load with a battery voltage of 12v nominal = 166 amps and change. 2000w at 48v nominal: 41amps. Wildly different cabling, fuses, etc.
I have really kicked around the idea of forklift batteries. I read of people using them for 20+ yrs. The prices I got was $2800 48v 800ah delivered,but They are 3-4000lbs. I don’t know if my equipment will handle it to unload off the truck. The plus side is they are made of individual cells that can be changed out when bad.
True, but you still need battery management, and probably a cooling system. They are also used so even if they work out of the box after getting a BMS, it may not be that long before you start finding and needing to replace dead cells. I would still go through the entire pack looking for dead cells because of fire risks from lion. Lion also doesn’t last as long as LiFeP.
But it is a viable solution for about the same money as brand new golf cart batteries.
48 volts at 800 amp hours is 38.4 kW / hours of storage. At your pricing at just $2800 bucks that puts you at just .07 cents pr watt. That would be very cheap system and very robust. But I would imagine these will not have as good conversion efficiency but I dont know just assuming.
So for comparison, you would need roughly 13 of the LG Chem packs to match. That would put that cost in comparison to $3535.00 That includes shipping. For the $2800 price is that including the shipping?
A BMS only cost 20 to 50 bucks. These cells are going to last a minimum of 5 years; more like 10 years. It depends on your set up. If you have solar to maintain things any battery will last much longer. Lithium ion has a much greater cycle life than LifePo4 and are 40% more efficient. If you are fueling a gasifier then your energy has value added, you then will want the best possible efficiency you can get. .
You dont need a cooling system for off grid. These cells are capable
Edit: That is the different in cycle life. Cycle life is factoring hard cycling full charge to cut off. If you charge at 50% drain then you cells will last a life time. But you need twice the storage to meet application requirements.
If you are constantly maintaining the cells they very well could last you a lifetime especially lithium ion. When your charging above 50% drain you really are not charge cycling them as they are never getting far past the nominal voltage. A battery in your car can last 4 to 8 years as the system is always maintaining the charge. Verses off grid you would be lucking to get a year of hard cycling.
Degradation of the cells is very dependent on the chemistry as well. They all degrade but all do it in different ways.
Here is a randon reseller of a lifep batteries, they are simpliphi and for sure aren’t the cheapest. Note: they are claiming 10k cycles. And you don’t get the deterioration with the deep discharge with lifep like you do with lion or lead acid. My point is once you start calculating the finite lifetime of a battery, they are actually cost competitive. If you buy the rolls only discharge it to 50% you get 1250 cycles. If you get the simpliphi battery you get 10k cycles at 100% depth of discharge, but you aren’t paying over 8x more for the battery nor do you have to install them and pay for shipping 8x. Where I agree is the upfront cost is considerably more.
Lithium Ion has better cycle life than LifePo4. Also factor in the conversion efficiency as well.
LifePo4 are only 60% efficient verse Lithium Ion is over 90%.
So if you are paying in the form of labor to fuel a gasifier , this is 30% more labor you will put into every charge cycle to get the same outcome. Your labor is cost and it will add up.
“SimpliPhi batteries have a round-trip efficiency of 98% – one of the highest in the industry. … SimpliPhi batteries use LFP chemistry , which is the safest, non-toxic and environmentally benign Lithium Ion chemistry available.” --(annoying * from their site)
That is about right on par with other lithium batteries for roundtrip -battery- efficiency. The inverters are what really knock it down, but that happens with any inverter regardless of cell type.