Lithium Batteries

[grashley]

I have the RV in my sig. Right now it has 2 Lead Acid (LA) coach batteries and one LA chassis battery side by side under the entry steps. As I understand this, all 3 batteries are charged with the converter when 120V is available and with the chassis alternator when driving. They power coach and chassis independently when not charging.
I kept my 2 x 200 aH Li batteries when I sold the FW and would like to use them in the new RV.
The current converter is a PD 9245-C, which will not hurt a Li battery, but will not give it a full charge. I have also read mixing Li and LA batteries is not good. Is keeping the LA chassis battery and switching to Li Coach batteries considered mixing batteries? Do i need to ditch the 2 LA coach batteries to protect the Li batteries?
Would I need to upgrade my converter? Could I keep the converter and get a full charge from a Li capable trickle charger or Li capable battery charger (higher amps)? How about a DC2DC?
Any special wiring needed to better separate the Li from the LA?
I just know enough to know I do not know enough.. Please educate me.
Gordon

 

[Isaac-1]

First off, you should never mix batteries of differing chemistries in the same battery bank, if you ditch the Lead Acid and go LiFePo4 is up to you.

A PD9245 will most certainly fully charge a set of LiFePo4 batteries, if you have the optional Charge Wizard pendant and manually set it back into bulk charge mode if it times out after 4 hours and the LiFePo4 batteries are not fully charged. I have its big brother the PD9260, and have been using 420AH of LiFePo4 batteries with it for almost 3 years. In my case most of the time 4 hours at 60 amps (240AH) will bring mine back to full charge, as I rarely drain them down over half way, as I also have solar on the roof, and it would take a long string of cloudy days to fully discharge my batteries.

 

[John From Detroit]

Progressive Dynamics also makes a version specific for LiFePO4 batteries in partnership I believe with Battle Born batteries. I use an inverter/charger here at the apartrment (Same one I had in the motor home) and it ... is programmable for different batteries .

 

[John Canfield]

...snip... As I understand this, all 3 batteries are charged with the converter when 120V is available and with the chassis alternator when driving. They power coach and chassis independently when not charging.
I kept my 2 x 200 aH Li batteries when I sold the....snip.....

That is correct, house and chassis batteries are all bridged together by a solenoid that Winnebago calls the "Battery Mode Solenoid" when the engine is running, or when the "Battery Boost" switch is operated.

On shore power all three batteries are charged, how exactly that is done depends on what Winnebago installed - maybe the Trik-L-Start or something else.

I have no direct experience with LiPo (or whatever chemistry) in an RV environment so I'm not sure how engine alternator charging would affect Lithium batteries.

 

[atodalen]

I have the PD4645 converter and as Isaac-1 said above, you can use the charge wizard to fully charge them. I was concerned with potential alternator damage from charging the LiFePO4 batteries due their

large current draw. In order to negate the risk I chose to disable the solenoid that ties the coach and chassis batteries together while the engine is running. It was a simple matter of installing a switch in the wire that controls the solenoid. Be aware that if you do this that your coach batteries will only charge if you're on shore power or the generator is running. Another option is to install a DC-DC charger such as some made by Victron but the solenoid would still need to be out of the charging circuit.

 

[Gary RV_Wizard]

A somewhat more elegant (but still inexpensive) method is to install an auto-reset circuit breaker in the path from alternator to LiPo house batteries. Maybe a 50A breaker? That protects your alternator from a severe load but let's charging operate normally most of the time.

Note that this potential overload problem isn't universal - it depends on the alternator capacity and the battery bank size (amp hours). A big battery bank (>200 AH) and a smallish alternator (<120A) is a high risk scenario, but a <200AH batter bank with a 160 A alternator is pretty safe.

 

[Lou Schneider]

I have the PD4645 converter and as Isaac-1 said above, you can use the charge wizard to fully charge them. I was concerned with potential alternator damage from charging the LiFePO4 batteries due their large current draw.

I found the voltage drop along the charging wire(s) will limit the current to safe values, even in a motorhome. Like Gary said, excessive current draw is only a problem with large battery banks - if you only have 100-200 a/h of lithium it's not a concern.

 

[Mark_K5LXP]

Voltage drop - an option you don't hear many bring up is the use of a ballast. Add a little bit of series resistance from the alternator charge side and the charge current will drop to a safe value. Resistance in this case is a piece of wire, of either calculated or empirically determined length that results in the desired charge current. Pick a worst case, like lithium battery dead, add in the ballast wire (say 2 gauges smaller and some nominal length like 10ft) and measure again. Trim length to net the current and done. The initial reaction is it's not efficient to do it this way, but who cares. You're going down the road, your battery is charging and your alternator is within bounds. No modifications to existing systems, simple and cheap.

Mark B.
Albuquerque, NM

 

[Isaac-1]

I found the voltage drop along the charging wire(s) will limit the current to safe values, even in a motorhome. Like Gary said, excessive current draw is only a problem with large battery banks - if you only have 100-200 a/h of lithium it's not a concern.

This may work for some people, but not all, and a lot has to do with the wire size the RV manufacturer used for the charge line, and how far the batteries are located away from the alternator. Keep in mind some motorhomes have the house batteries located right next to the engine starting battery close to the engine, while others may have them located 15-20 feet away or more. Worse yet the variables at play here are not that easy for the average person to determine in advance

 

[Isaac-1]

A somewhat more elegant (but still inexpensive) method is to install an auto-reset circuit breaker in the path from alternator to LiPo house batteries. Maybe a 50A breaker? That protects your alternator from a severe load but let's charging operate normally most of the time.

Note that this potential overload problem isn't universal - it depends on the alternator capacity and the battery bank size (amp hours). A big battery bank (>200 AH) and a smallish alternator (<120A) is a high risk scenario, but a <200AH batter bank with a 160 A alternator is pretty safe.

I don't trust self resetting breakers for something like this as they can get VERY hot after repeatedly tripping and resetting.

 

[John Canfield]

Here's a pretty useful article about Lithium chemistry battery charging. Alternator charging is partway down the page.

 

[Isaac-1]

How Battle Born stays in business charging $750 for a 100AH LiFePo4 battery in an era when I recently (March) bought a Dr Prepare 100AH LiFePo4 battery with a 10 year warranty for $139 is beyond me. Sure they are good quality and come with great support and warranty, but that does not justify charging more than 5 times the price of the import competition.

 

[John Canfield]

Do not construe my post as endorsing Battle Born products.

 

[John From Detroit]

How Battle Born stays in business charging $750 for a 100AH LiFePo4 battery in an era when I recently (March) bought a Dr Prepare 100AH LiFePo4 battery with a 10 year warranty for $139 is beyond me. Sure they are good quality and come with great support and warranty, but that does not justify charging more than 5 times the price of the import competition.

I recall when TV went digital. At an FMCA convention they were selling "Digital" tv antennas $99.00.

same antenna was $30 (or less) at Radio shack and not as good as the original batwing 4

 

[Lou Schneider]

How Battle Born stays in business charging $750 for a 100AH LiFePo4 battery in an era when I recently (March) bought a Dr Prepare 100AH LiFePo4 battery with a 10 year warranty for $139 is beyond me. Sure they are good quality and come with great support and warranty, but that does not justify charging more than 5 times the price of the import competition.

Battle Born was the first to bring LiFeP04 batteries to the consumer market using the same techniques their parent company Dragonfly Energy used to make LiFeP04 batteries for the military. They manually assemble 26 cylindrical cells in parallel to make a 100 a/h, 3.6 volt pallet. Then 4 of these are stacked in series with a BMS to produce a "12 volt" lithium iron phosphate battery.

The basic construction of cylindrical cells makes them well suited to withstand the extreme vibrations and abuse you'll find in combat situations.

In the meantime, Chinese companies have become very good at mass-producing low cost LiFeP04 batteries using commodity grade rectangular prismatic cells, where a single cell delivers 100 a/h. Again 4 of these are placed in series with a BMS to make a 12 volt battery.

If you have an application where the battery will be subject to extreme combat-like conditions, Battle Born is your choice. Otherwise, IMO the much less expensive prismatic cell batteries are perfectly fine for RV and stationary use.

Also, "Battle Born" is the state slogan of Nevada, home of their factory and parent company.