Converting to Lithium Batteries

[DLR Camper]

I have a Nash 2016 17K trailer with two deep cycle batteries (the original ones from purchase). I recently purchased 2 Lithium batteries so I can get longer battery life between charges or having to hook up to power. I looked to see if there was a switch in the panel to change from deep cycle to Lithium. I did not find one. Has anyone switched over to Lithium batteries? Is there anything special I need to do before switching them out. Any feedback is appreciated.

 

[JayArr]

You may need to change your battery charger.

Can you tell us the make and model of the charger/converter currently installed in your rig?

 

[PJ Stough]

Your current charger/converter, or charger/inverter will probably charge your LiFePo4 batteries, but probably not as efficiently as a charger made specifically for LiFePo4 batteries.

 

[Isaac-1]

What they said, your current converter charger likely falls into 1 or 3 possible categories:

1, It will charge your LiFePo4 batteries ok, though perhaps slightly slower than optimal

2, It will charge your batteries just fine, and there is no need to upgrade

3, It will either over charge or under charge your batteries and should be replaced before you kill your new expensive batteries.

Please post the model number of the converter and how many and what size batteries you have.

Ike

 

[DonTom]

I looked to see if there was a switch in the panel to change from deep cycle to Lithium.

Some converters have such a strap (which can be on a switch), but not many.

But your old LA converter will probably charge a lith battery to around 85% or so. In some cases, you will probably prefer such, as many lith batteries do NOT like to be left at 100% SOC for a long time.

The same goes for charging while driving.

But if you have solar, it will probably charge it from your ~85% to 100% on a sunny day.

I have lith batteries in both my RVs and both converters are for lith. But normally it's not necessary to charge to 100% SOC, but your converter will also be slower. But it will be useable as is, perhaps in most cases.

Like much of RVing a lot of what you need depends on the way used.

I use my house batteries a lot for ham radio and watching TV when boondocked and I like to start with a full charge. But I have yet to use as much as 15% SOC even staying up most of the night on my 300 AH lith battery. I normally use less than 10% SOC per night. So I should be able to go around ten nights without a recharge when boondocked, but I never have tried such.

-Don- Reno, NV

 

[Zulu Kono]

I have a Nash 2016 17K trailer with two deep cycle batteries (the original ones from purchase). I recently purchased 2 Lithium batteries so I can get longer battery life between charges or having to hook up to power. I looked to see if there was a switch in the panel to change from deep cycle to Lithium. I did not find one. Has anyone switched over to Lithium batteries? Is there anything special I need to do before switching them out. Any feedback is appreciated.

I'm about to invest in LiFePO4 batteries myself.
My camper is a '97 and had an old single-stage converter.
Seemed to me like upgrading the converter
was the first thing I needed to do, so I replaced
it with a four-stage Progressive Dynamics unit which
can be switched over to charge LiFePO4 batteries.
It also came with a new DC fuse board and labels to
apply on the inside of the power center which will
alert any future owners that it's been retrofitted.
Total cost was about $240.

 

[rbrdriver]

That's what we did was change the converter charger to one that was designed for lithium batteries. Works great so far anyways........

 

[steveblonde]

2 issues with Lithium batteries

1. cost
2. if you run them below 10.6 volts they will lock you out and then you need to take them in to get them reset - everytime!
yes they are lighter but really not worth the extra investment in my opinion - we sell them at work nothing but issues

 

[Lou Schneider]

2 issues with Lithium batteries

1. cost
2. if you run them below 10.6 volts they will lock you out and then you need to take them in to get them reset - everytime!
yes they are lighter but really not worth the extra investment in my opinion - we sell them at work nothing but issues

Never heard of #2. When I ran my Lion Safari batteries down to cutoff they started charging as soon as they saw the charger's voltage. Will Prowse routinely does the same thing on the lithium batteries he tests - runs them down until they shut off to measure their a/h capacity, then puts them on a charger to fill them back up.

Of course, if the battery is below freezing a smart BMS will refuse to let it accept charging power until it warms up. They'll deliver power down to -10F or so but won't charge until the battery warms above freezing. This is another parameter Will routinely tests on his battery teardown videos.

Some battery chargers won't start charging unless they see adequate battery voltage to start with, 10.6 volts is a common cutoff point for these chargers since it's the resting voltage of a lead acid battery with a shorted cell. Maybe this is what you're seeing?

As far as cost, with 100 a/h lithiums (with 100% of that usable capacity) now starting at about $400, they're cost effective with AGM lead acid batteries. And unlike lead acid batteries lithiums don't brown out as they reach end of charge.

 

[DonTom]

Never heard of #2.

I have, at least with EV HV motorcycle batteries. I assume this applies to all the larger more expensive lith batteries.

It is only an issue with long term storage when the battery is not being kept charged. That's another reason why they often say charge every few months when not being used.

In normal use, the BMS will shut the load off the battery well before it gets to that point that destroys the battery and you can still recharge after a short wait. This always happens well below zero SOC indicated.

The fastest way to void an EV battery warranty is to drive it all the way down to below 0 SOC ("reserve tank" often gives close to an extra 10% of range below zero SOC) and then let it sit for more than 24 hours without a recharge. And the bike's computer will know if that happened and will save the info for the battery warranty claim which will then be denied. I assume it's the same with the EV cars, but I only read about the issue with EV bikes.

BTW, electric motorcycles made for the military have a special switch that can be turned on to drain the battery all the way down to true nothing, which WILL destroy the expensive battery, but that could save a life.

I assume the RV lith batteries are the same other than what voltage the BMS cuts off the load at.

So while it is true ( I do not know if 10.6V is accurate or not with RV lith batteries), it's rarely an issue. It's just not going to happen simply with normal use when the RV is being used normally, even if you drain it all the way down, as long as you do not let it sit long discharged. I think by then any RVer will know they need a recharge!

-Don- Auburn, CA

 

[DonTom]

1. cost

Cost is about the same these days, if you take into consideration how long each type of battery will last. The lith could cost five times as much as it lasts five times as long than a L-A.

I doubt if I will need to buy another RV house battery for the rest of my life. Same for my EVs.

-Don- Auburn, CA

 

[steveblonde]

Cost is about the same these days, if you take into consideration how long each type of battery will last. The lith could cost five times as much as it lasts five times as long than a L-A.

I doubt if I will need to buy another RV house battery for the rest of my life. Same for my EVs.

-Don- Auburn, CA

We sell the regular acid batteries for $200 each and the Lith ones are $1000 each (canadian) and yes we have to get the dealer to unlock the batteries which is a pain

 

[DonTom]

We sell the regular acid batteries for $200 each and the Lith ones are $1000 each

And the lith can last five times as long, plus give better performance. I would say the price of the lith is cheaper than L-A for what you get.

-Don- Auburn, CA

 

[Isaac-1]

There are also plenty of LiFePo4 batteries that cost less than $1,000, I paid just under $1,500 US for a pair of 210AH 12V LiFePo4 batteries in November, though admittedly they were discounted due to being irregular (actual specs did not match what was printed on the label).

 

[Grid Point Designs]

Just hear to clear up some misconceptions about lithium batteries.
Charging: Not only does lithium have a slightly higher resting and working voltage than lead acid, it has a different charging algorithm. Lithium doesn't benefit or need an "absorption" cycle, and the lifespan can be significantly shortened if the battery is put into an absorption cycle for an hour. Most lead acid chargers will have a set absorption time and should not be used with lithium chemistry. A charger for lithium batteries lets you cut out the absorption cycle, or limit it to just 20 minutes. This is essential.

Low voltage lockout: All lithium batteries come with some type of BMS (battery management system), which will protect the battery from overcharging or over-draining. The vast majority of name brand lithium providers, such as Lifeblue and Battleborn, will have a BMS that disconnects at about 9 volts. This is simply to avoid the batteries being damaged, and they will reconnect as soon as they see a charging source.

Lithium batteries last for over 6000 full discharges, and have an incredibly long lifespan. Treat them right!

 

[Isaac-1]

Thanks for this comment, though without specifying exact voltages such terms as absorption does not tell us much. Some lead acid chargers, have low enough absorption voltages (13.6-13.8VDC) that it is not an issue for Lithium batteries as this is below their full charge voltage, others put out high equalization charging which can be bad for Lithium batteries. I don't know that most lead acid chargers are bad for Lithium, though I would agree that many are, and if converting to Lithium you should carefully check the charging specs for your existing converter charger to see if it is within the accepted range for the Lithium batteries you are buying.

 

[Zulu Kono]

Just hear to clear up some misconceptions about lithium batteries.
Charging: Not only does lithium have a slightly higher resting and working voltage than lead acid, it has a different charging algorithm. Lithium doesn't benefit or need an "absorption" cycle, and the lifespan can be significantly shortened if the battery is put into an absorption cycle for an hour. Most lead acid chargers will have a set absorption time and should not be used with lithium chemistry. A charger for lithium batteries lets you cut out the absorption cycle, or limit it to just 20 minutes. This is essential.

Low voltage lockout: All lithium batteries come with some type of BMS (battery management system), which will protect the battery from overcharging or over-draining. The vast majority of name brand lithium providers, such as Lifeblue and Battleborn, will have a BMS that disconnects at about 9 volts. This is simply to avoid the batteries being damaged, and they will reconnect as soon as they see a charging source.

Lithium batteries last for over 6000 full discharges, and have an incredibly long lifespan. Treat them right!

I'll soon be putting together a LiFePO4 kit from SunFunKits.
I recently upgraded the converter in my camper
from a single-stage to a four-stage PD4643V.
It has a jumper on the circuit board that can be moved into
"lithium" mode which will put out 14.6 volts continuously.
I don't know what you mean by "absorption" cycle.
Is that the same as bulk charging, and which mode
should my converter be in for a LiFePO4 battery?

 

[Grid Point Designs]

Yes good point, I'll be more specific. Lithium voltage is either one of the following: a) Lithium-Ion at 3.7v per cell or b) LiFePO4 at 3.2v per cell. Four cells make up a 12v battery. These days almost all lithium providers are using LiFePO4, and have a nominal voltage of about 13.2v.

A full charging cycle for lithium usually involves bulk charging to around 14.2v and removing the float stage. If float is kept, it just has to be below the resting voltage (13.2v in this example).

An older lead-acid converter/charger won't work for lithium charging if it has:
a) Any type of equalization (charging at 15 volts for a period of hours)
b) Absorption for longer than 30 minutes (voltage higher than 14.2v)
c) Float at higher than resting voltage (a float of 13.3 or higher in this example).

 

[xrated]

The safest way to charge a LFP battery is to use a charger that basically stops charging based on tail current of the charger. Some have adjustable tail current values, other don't. And any LFP charger that maintains a float voltage of 13.8 or higher is, in my opinion, detrimental to the battery. 13.8V (3.45V per cell) is considered to be fully charged, and if the charger holds that as a float voltage, you are essentially keeping the LFP battery at 100% SOC.....and LFP batteries do not like to be held at full charge for long periods of time. My charger's tail current is based on 10%, so the 43A charger will revert to float when the charging current gets down to 4.3 amps. And float on mine is 13.4V, which is below the point of keeping the battery at full charge.

 

[xrated]

Yes good point, I'll be more specific. Lithium voltage is either one of the following: a) Lithium-Ion at 3.7v per cell or b) LiFePO4 at 3.2v per cell. Four cells make up a 12v battery. These days almost all lithium providers are using LiFePO4, and have a nominal voltage of about 13.2v.

A full charging cycle for lithium usually involves bulk charging to around 14.2v and removing the float stage. If float is kept, it just has to be below the resting voltage (13.2v in this example).

An older lead-acid converter/charger won't work for lithium charging if it has:
a) Any type of equalization (charging at 15 volts for a period of hours)
b) Absorption for longer than 30 minutes (voltage higher than 14.2v)
c) Float at higher than resting voltage (a float of 13.3 or higher in this example).

Mine floats at 13.4, which is below full charge voltage. 13.4V works out to 3.35V per cell and is obviously below the 3.45V per cell which is considered to be full charge on LFP.