Charging Lifepo4 with shorepower

Jbarnes1719

New Member
quick search says NEC allows 75 amps in #6 with 90c insulation.
my ampacity chart says 120 amps with 105c insulation.

Voltage drop might be an issue, probably not heat.
Hopefully my bms will give me the info I need to decide whether to rewire with a bigger gauge. Everything works well with my 100ah lead acid batteries but I need more capacity.
 

HRTKD

Boondocker
Unless his RV is fairly new, it probably came with a 'converter' which does exactly that - Converts 120 VAC to a single voltage DC, typically 13 volts or so which isn't good for charging ANY battery - The voltage is low enough it will take forever to recharge even a small lead acid battery, but high enough that once it is fully charged, it will boil the water out of the battery

Any multi-step charger which advertises adjustments for lithium batteries should work fine. I would agree with a 50 amp unit. Usually when you're plugged into shore power it's for long enough (typically overnight) that 50 amps would recharge a modest size battery bank. The exception for a larger unit might be if he intended to use it while running his genset, then a larger unit might be preferred so charging would be faster . . . . but not so large it would cause problems starting his A/C unit

Don

Many of the converters in RV's, even going back quite a few years, would have more than one stage. My 2006 trailer had a three stage converter.

Still, the older converters oriented towards lead acid batteries aren't optimal for LiFePO4. Any four stage converter certainly isn't acceptable since the fourth stage is usually for desulfation which uses high voltage.
 

snoobler

Solar Honey Badger
Moderator
I can't recall ever seeing a converter that offered equalization as an option. Often the 4th stage was a forced re-bulk and absorption every 24 hours.
 

Diysolar123

Solar Enthusiast
quick search says NEC allows 75 amps in #6 with 90c insulation.
my ampacity chart says 120 amps with 105c insulation.

Voltage drop might be an issue, probably not heat.
the voltage drop is the heat... it turns the wires into a nice resistance heater.
Here is a calculator that has the NEC allowable voltage drop equation...


a 6awg wire 20' long would have a 12% voltage drop.
 

HRTKD

Boondocker
I can't recall ever seeing a converter that offered equalization as an option. Often the 4th stage was a forced re-bulk and absorption every 24 hours.

My IOTA Engineering converter did it with the IQ4 module.

 

snoobler

Solar Honey Badger
Moderator
That's an IQ4 module, not a converter, but I'll concede the point with a re-statement.

Never seen a non-IOTA converter/IQ4 combo that offered equalization. :)
 

bruceb58

New Member
they were running 55amps thru a long length of 6awg wire??? toasty...
Wouldn't be toasty, just a bunch of voltage drop. With 20' it would be about 0.5v in just one of the conductors. That's 27W over 20 feet of wire. Not an issue.

Not reccomended for charging because of the percentage voltage drop...just not a safety issue.
 

snoobler

Solar Honey Badger
Moderator

I'll go with the manufacturer's manual over an Amazon listing:


3 stage charger.

Progressive Dynamics 4 stage converter


"EQUALIZATION Mode 14.4 Volts – Every 21 hours for a period of 15 minutes prevents battery stratification & sulfation – the leading cause of battery failure."

That's not an equalization mode just because they call it one. That's the 4th stage as I describe above - a re-bulk to the absorption voltage, every 21 hours for 15 minutes in this case.
 

snoobler

Solar Honey Badger
Moderator
the voltage drop is the heat... it turns the wires into a nice resistance heater.
Here is a calculator that has the NEC allowable voltage drop equation...


a 6awg wire 20' long would have a 12% voltage drop.

6.04%

 

time2roll

Solar Enthusiast
Do you really want to hit LFP with 14.4 volts every day even if in storage? Maybe 15 minutes is not a big deal.

I suppose it might activate the BMS balancing so it could be called 'equalizing' in that sense.
 

snoobler

Solar Honey Badger
Moderator
Do you really want to hit LFP with 14.4 volts every day even if in storage? Maybe 15 minutes is not a big deal.

I suppose it might activate the BMS balancing so it could be called 'equalizing' in that sense.

The discussion at hand is equalization. Equalization is a deliberate over charge at notably higher than normal voltages specifically for the purposes of increasing specific gravity of FLA. It's this cycle that has the potential to devastate unprotected LFP as well as AGM/GEL batteries.

Would I use the PD converter? In a cyclic application, sure. Plugged into shore power "floating" the LFP? No. I'd replace it.

My point in this and other threads like this:

LFP batteries don't NEED LFP converters. Existing converters may work just fine with some or no compromises. Wiring issues (voltage drop) represent the bigger issue regardless of battery chemistry, and even a "LFP" converter may under charge LFP in some situations and overcharge them in others.

Three steps when installing LFP in an RV:
  1. Confirm your existing converter has compatible voltages/charge profiles (14.6V max absorption, 13.6V max float).
  2. Try it to see if it works.
  3. Fix your wiring or replace your converter based on the results.
 

Jbarnes1719

New Member
The discussion at hand is equalization. Equalization is a deliberate over charge at notably higher than normal voltages specifically for the purposes of increasing specific gravity of FLA. It's this cycle that has the potential to devastate unprotected LFP as well as AGM/GEL batteries.

Would I use the PD converter? In a cyclic application, sure. Plugged into shore power "floating" the LFP? No. I'd replace it.

My point in this and other threads like this:

LFP batteries don't NEED LFP converters. Existing converters may work just fine with some or no compromises. Wiring issues (voltage drop) represent the bigger issue regardless of battery chemistry, and even a "LFP" converter may under charge LFP in some situations and overcharge them in others.

Three steps when installing LFP in an RV:
  1. Confirm your existing converter has compatible voltages/charge profiles (14.6V max absorption, 13.6V max float).
  2. Try it to see if it works.
  3. Fix your wiring or replace your converter based on the results.
I am emailing my favorite manufacture to suggest that lifepo4 is the future of rv boon docking and solar power for rv’s. Hopefully they will in the future build with that in mind. Having to reengineer and rewire a new rv or even an old one to accommodate higher amperages and longer off grid times is a pain.
 

Flux

New Member
Not an RV, but I am in the process of adding LiPo to my van. I have a 200AH AGM but it is half dead so I am adding a 100AH Li to it as well. My electrical needs are really simple and small. Lights, device chargers, 12volt fridge. Never more than 10 amps. I am keeping the AGM as a secondary load/starter battery, redundancy is key with me. I plan on putting the lithium on the main house loads and eventually the solar when i install that.

If you have a converter, then add a Victron Orion Smart Charger in between. It could handle that or the alternator if that feeds it. My AGM handles an alternator charge fine, but I don't want it pushing to my Li.

I bought a Victron IP65 charger 10A for general use. I will be hooking up extra charger lead plugs to both the AGM and the Li battery for shore charging. I just have to change the settings and swap the leads if I am charging one or the other.

Simple setup that could do the trick if you are only running 200AH. You can get a 30A Orion, I am opting for the 18A which is plenty for me. Nice thing is I can set up a custom profile for the Li if I feel like I have an unbalanced cell, although I could do the same with the BMS.
 

time2roll

Solar Enthusiast
Yes all the converters have something missing. I think I want 14.4 and then off. Adjustable on at maybe 13 volts. Is there any stand alone chargers that do this?
 

Jbarnes1719

New Member
Not an RV, but I am in the process of adding LiPo to my van. I have a 200AH AGM but it is half dead so I am adding a 100AH Li to it as well. My electrical needs are really simple and small. Lights, device chargers, 12volt fridge. Never more than 10 amps. I am keeping the AGM as a secondary load/starter battery, redundancy is key with me. I plan on putting the lithium on the main house loads and eventually the solar when i install that.

If you have a converter, then add a Victron Orion Smart Charger in between. It could handle that or the alternator if that feeds it. My AGM handles an alternator charge fine, but I don't want it pushing to my Li.

I bought a Victron IP65 charger 10A for general use. I will be hooking up extra charger lead plugs to both the AGM and the Li battery for shore charging. I just have to change the settings and swap the leads if I am charging one or the other.

Simple setup that could do the trick if you are only running 200AH. You can get a 30A Orion, I am opting for the 18A which is plenty for me. Nice thing is I can set up a custom profile for the Li if I feel like I have an unbalanced cell, although I could do the same with the BMS.
I have thought of using a dc-dc charger. Another poster suggested a stand alone charger that could be plugged in anytime you have access to shore power or use my Yamaha gennie. Charge times are fairly quick on lifepo4. I believe that is the way I am going. I also have currently a 200 watt solar setup that will eventually be 600-800 watts. I have 6 gauge wire but I probably rewire to 2-4 gauge to be safe. My draws are not that great. Just want to be able run everything but the air.
 

HRTKD

Boondocker
I have thought of using a dc-dc charger. Another poster suggested a stand alone charger that could be plugged in anytime you have access to shore power or use my Yamaha gennie. Charge times are fairly quick on lifepo4. I believe that is the way I am going. I also have currently a 200 watt solar setup that will eventually be 600-800 watts. I have 6 gauge wire but I probably rewire to 2-4 gauge to be safe. My draws are not that great. Just want to be able run everything but the air.

6 gauge is likely fine for your solar. Or did you mean 6 gauge for everything except the solar?
 

Jbarnes1719

New Member
6 gauge is likely fine for your solar. Or did you mean 6 gauge for everything except the solar?
I have 6 gauge between the batteries and the rv power center (charge/converter). I know when I install my stand alone charger I will install 4gauge between the charger and the batteries.
 
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