How quickly do lithium batteries charge?

[Mike Lewis]

I have on occasion depleted my original lead-acid batteries below 50%, and then found a campground with hookups so I could charge them up. I found that sometimes they would not charge completely overnight, but would take a day or more, depending upon their state of discharge.

We now have enough lithium users for some real-world data on how they perform. So-- how quickly will the lithium batteries charge from shore power or a combination of shore power and solar panels, using an appropriate charger (e.g. Progressive Dynamics)? I'm curious.

[Vermilye]

My pair of Battleborn 100 amp hour lithium batteries will take the full output of the converter (I have a 35 amp converter), plus the solar output until they reach around 95%, when they start to taper off. So far, the highest combination I've seen is 47 amps.

As to how long, it depends on far down they are, but much faster than lead acid batteries since there is no absorption phase (at least with the right converter). It goes from bulk to float.

So far, with limited camping, I've never seen the converter run a full power (except at home after letting the batteries get down to 79%). By the time I get to a campground, the 9 amps from the truck & what ever the solar is producing has the batteries full by the time I get there.

[Lanark Camper]

Originally Posted by Vermilye

My pair of Battleborn 100 amp hour lithium batteries will take the full output of the converter (I have a 35 amp converter), plus the solar output until they reach around 95%, when they start to taper off. So far, the highest combination I've seen is 47 amps.

As to how long, it depends on far down they are, but much faster than lead acid batteries since there is no absorption phase (at least with the right converter). It goes from bulk to float.

So far, with limited camping, I've never seen the converter run a full power (except at home after letting the batteries get down to 79%). By the time I get to a campground, the 9 amps from the truck & what ever the solar is producing has the batteries full by the time I get there.

Jon, I assume it's the wire size between the trucks alternator and the trailer battery bank that limits the charge to 9 amps. Have you considered increasing the size of these wires to take advantage of the large alternator on your truck ?

On boat engines I've installed an external smart regulator to output 90 amps into an AGM bank. The smart regulator used a sense wire right on the battery post to measure actual battery voltage at these current levels.

Bob

[Vermilye]

Originally Posted by Lanark Camper

Jon, I assume it's the wire size between the trucks alternator and the trailer battery bank that limits the charge to 9 amps. Have you considered increasing the size of these wires to take advantage of the large alternator on your truck ?

On boat engines I've installed an external smart regulator to output 90 amps into an AGM bank. The smart regulator used a sense wire right on the battery post to measure actual battery voltage at these current levels.

Bob

No, it is the 9 amp DC to DC converter that I have in the charge line. While not absolutely necessary, without it the lithium batteries (that have a float voltage around 13.6, higher than the resting voltage of the truck's AGM starter battery) would attempt to charge the tow vehicle battery and might never reach full while towing.

The converter is a one way path - the output is set at 14.4V (the bulk/absorption voltages recommended by Battleborn) to charge the lithium batteries. With dual solar panels, I don't need more than the 9 amps charging from the truck. Battleborn suggests limiting the charging current for 2 100 amp hour batteries at 100 amps, so I could go higher if necessary, but so far the 9 amp limit has not been a problem. I spend months at a time in one location, so the solar is far more important as a charging source.

[Mike Lewis]

Originally Posted by Vermilye

Battleborn suggests limiting the charging current for 2 100 amp hour batteries at 100 amps

This was the information I was looking for, thanks. So I can imagine a scenario in which someone with 4-500 amp-hours of lithium batteries depletes their charge after a string of cloudy days, then camps for one night at a spot with hookups, and charges them all overnight before moving on to another string of days boondocking. Sort of like a camel at an oasis, but with electricity instead of water. Sure, this would be a super-expensive way of doing things, but I find the possibility intriguing.

[Vermilye]

Originally Posted by Mike Lewis

This was the information I was looking for, thanks. So I can imagine a scenario in which someone with 4-500 amp-hours of lithium batteries depletes their charge after a string of cloudy days, then camps for one night at a spot with hookups, and charges them all overnight before moving on to another string of days boondocking. Sort of like a camel at an oasis, but with electricity instead of water. Sure, this would be a super-expensive way of doing things, but I find the possibility intriguing.

They do recharge at high rates, and unlike lead acid batteries, charge at the source current rate until 95% or so full.

If you charge at "C", (200 amps in my case) you do cut the life down a bit - 2000 cycles, or for me at 250 days per year only 8 years. At C/2, the recommended rate, you can expect 3000 - 4000 cycles. That would be discharging to 50% every day, which I would rarely do. The lowest I discharged my flooded 6V batteries was 75% and I can count on one hand the number of times that happened.

On the other hand, if you limit charging current to C/4 or less, you extend the life to 8000 - 10,000 cycles. Let's see - that would make me 111 years old before the capacity dropped to 80%!

Along with the quick charging, the other major advantage is the voltage curve is much flatter than lead acid batteries as they burn amp hours. Full is around 13.6V, at half capacity you still have 13.2V, and at 15% capacity (down from full by 85%) you still have 12.5V. This makes inverters much happier.

[Mike Lewis]

Thanks, Jon. Is "C" determined by the total amp-hours that you have in your battery bank, or is that just a coincidence?

[John in Santa Cruz]

yes, in this context, C is the capacity, or max amp-hours of the battery. so C = 100 for a 100AH battery.

[Mike Lewis]

So if I have a 500 Ah battery bank and charge at a rate of C/4, I can live to be 120? I might be drawing the wrong conclusion here.

[John in Santa Cruz]

of course, C/4 for a 500AH battery would be a 125 amp charger, thats like 1700 watts

[Mike Lewis]

I installed two Battle Born lithium batteries last Sunday 10/20. The solar panels are disconnected from the system while I finish upgrading the controller. My Escape has the stock WFCU charger / distribution panel.

Two days ago I disconnected the batteries from shore power and cooked a frozen dinner in the microwave, using the stock inverter. I did this in order to draw the batteries down (and I was hungry). Yesterday I recalibrated my TriMetric TM-2025 battery monitor to work with the new batteries according to Bogart Engineering's instructions. The batteries read 90% capacity.

I plugged the trailer in to shore power. At first the batteries were charging at nine amps, which tapered off to 5-6 amps and continued to taper off until it was just a trickle. At sundown yesterday the batteries were at 99%. This morning they were at 100% and the "fully charged" light on the monitor was on.

So it appears right now that my stock converter will fully charge the new batteries. It may be that the batteries have to cycle a few times before the monitor will give an accurate reading. I'll try it again in a few days to see.

[John in Santa Cruz]

my experience has been that Lithium batteries take several 80% discharge cycles before they deliver full capacity.

[Mike Lewis]

After some partial battery cycling I have some new data that shows Jon and others were right: the stock WFCO charger will not fully charge the lithium batteries. I had the trailer out in the sun a week or so ago to test the solar panels and new converter. Then I moved it back under its shed, and after being there for several days on shore power the batteries are showing 79%.

So at some point I'll need to replace the charger portion of the WFCO converter. I still think this can wait-- I should be able to depend upon the solar panels and my truck to top off the batteries.

[Vermilye]

A bit of real world charging of lithium batteries:

I left a dry campsite with a pair of Battleborn 12V 100 amp hour batteries at 79%, down 57 amp hours. Along with the furnace overnight, I toasted a muffin (at 100 amps @ 12V), and made a pot of drip coffee.

On the drive south on a cloudy Natchez Trace (lots of overhanging trees) the charge rate varied from 9.1 amps (the output of the truck through a 9 amp DC to DC converter) to as high as 22 amps when the trees & clouds went away (320 watts of solar on the roof with a Victron 100/30 solar controller set for lithium batteries).

At the end of a 196.5 mile, 4.5 hour drive, the batteries were at 99.8%. Unlike lead acid batteries, there was never a slow down in charging during the entire trip, other than the cuts in solar input due to shade.

[Mike Lewis]

Originally Posted by Vermilye

A bit of real world charging of lithium batteries:

I left a dry campsite with a pair of Battleborn 12V 100 amp hour batteries at 79%, down 57 amp hours. Along with the furnace overnight, I toasted a muffin (at 100 amps @ 12V), and made a pot of drip coffee.

On the drive south on a cloudy Natchez Trace (lots of overhanging trees) the charge rate varied from 9.1 amps (the output of the truck through a 9 amp DC to DC converter) to as high as 22 amps when the trees & clouds went away (320 watts of solar on the roof with a Victron 100/30 solar controller set for lithium batteries).

At the end of a 196.5 mile, 4.5 hour drive, the batteries were at 99.8%. Unlike lead acid batteries, there was never a slow down in charging during the entire trip, other than the cuts in solar input due to shade.

That's good info, and that drive mimics my typical trailer usage pattern-- driving 2-300 miles between stops, then staying a few days. Hopefully I'll get similar results.

BTW- did you see any wild turkeys? When I was going north on the Trace in Tennessee back in the spring I saw big wild turkeys on the side of the road. They may be in hiding this time of year, though.