RV Genny starting with Lifepo04

[John From Detroit]

If you are wanting a LiFePO4 port-a-power system I'd say make one
Among many other companies this one makes LiFePO4 batteries in 10-20AH sizes. Nice and light weight (compared to same size Lead acid) also the proper charger which works with solar or 'Other" sources they sell a charger too.

Bioenno Power

Bioenno Power provides high performing LiFePO4 (Lithium Iron Phosphate), LiPo (Lithium Polymer) batteries, and solar products to users.

www.bioennopower.com

Add some connectors a bit of wire and a 12 volt accessory socket all from auto-parts-r-us and a ammo case from Horrible freight (or small tool box you got it.

I use them for portable ham radio work.. Very nice.

 

[DonTom]

If you are wanting a LiFePO4 port-a-power system I'd say make one
Among many other companies this one makes LiFePO4 batteries in 10-20AH sizes.

My HFT Power Station runs from a 294 WH lith battery, so it's light. Has USB (including "c"), 12V and 120 VAC outputs (350 w continuous output), It can charge from 120VAC, DC, solar panels and the "C" is both an input for charging as well as an output to use.

These days there are many options for portable power. Here is another.

It can be charged as it is being used, as I am doing right now. It is very handy and a lot more useful than I expected.

Yes, I could build my own but that will not be nearly as neat and handy.

I moved my Starlink to inside this RV still using the HFT Power Station as it is being kept charged up and warm. It will not charge when it gets too cold from being outside here--until I use the RV's furnace to first warm it up.

-Don- Kingston Campground, NV

 

[d23haynes57]

This 2022 Class A has two 6V Harris, HBDAGMG6-A 224ah six-volt batteries in series.

I am thinking about changing them to two of these in parallel. And adding a lith converter since the stock Xantrex Freedom X 1200 has no lith profile.

This RV uses the house batteries to start the Onan 5500 genny.

I would think the two Lifepo04 in parallel (400 AH) would be fine for RV genny starting. But when I ask Rufus on Amazon if I can do such I get this as the reply:

"No, two of the LiTime 12V 200Ah Mini LiFePO4 RV Battery batteries connected in parallel would still not be suitable for starting RV generators.

Here's why:
•
Peak current limitations: Each battery supports up to 1000A peak discharge, but generator starting requires sustained high current over several seconds. LiFePO4 batteries are designed to limit discharge to protect their chemistry—they're not optimized for engine cranking.
•
Cold cranking amps (CCA) specification: RV generators require 800-1,500 CCA ratings. The LiTime battery doesn't publish CCA specs because lithium batteries handle cold temperatures differently than lead-acid. Two of them together won't change this fundamental mismatch.
•
BMS protection: The battery's management system may shut down during extreme starting loads to protect the cells, leaving you stranded.
Best practice: Use a dedicated lead-acid or AGM starting battery (800+ CCA) for generator starts, and keep the LiTime batteries as your auxiliary/house power system"
Should I believe above or not?

-Don- Kingston Campground, NV

I'll go back to the beginning here. When it comes to Lithium batteries, there is a lot of crap and mis information out there. In general, standard Life Po batteries should not be used for vehicle engine starting applications. Note I used the word vehicle. There are a lot of considerations and starting current is a very small part of that.
Now, from the though point of view, Lithium batteries are used for deep cycle applications and these incudes inverters. Doing simple rounding, an inverter on 12 volts needs 100 amps for every 1,000 watts produced. This will typically be a sustained load. You will size the battery bank to deliver the required power for the time you want it and you need BMS capacity to meet the demand plus some room for surge and other loads. So, if you have a 2,000-watt inverter you probably looking at 400 A/H capacity and a total of 300 A/H BMS. Your gas genny maybe on a real cold day will need a peak of 75 amps to get going. If you have Diesel generator, the 12.5K Onan will need up to 260 amps and maybe for 15 seconds. Still, not an issue.

Dennis

 

[triplethreat]

I'll go back to the beginning here. When it comes to Lithium batteries, there is a lot of crap and mis information out there. In general, standard Life Po batteries should not be used for vehicle engine starting applications. Note I used the word vehicle. There are a lot of considerations and starting current is a very small part of that.
Now, from the though point of view, Lithium batteries are used for deep cycle applications and these incudes inverters. Doing simple rounding, an inverter on 12 volts needs 100 amps for every 1,000 watts produced. This will typically be a sustained load. You will size the battery bank to deliver the required power for the time you want it and you need BMS capacity to meet the demand plus some room for surge and other loads. So, if you have a 2,000-watt inverter you probably looking at 400 A/H capacity and a total of 300 A/H BMS. Your gas genny maybe on a real cold day will need a peak of 75 amps to get going. If you have Diesel generator, the 12.5K Onan will need up to 260 amps and maybe for 15 seconds. Still, not an issue.

Dennis

I have a clamp on meter that measures either AC or DC (different setting of course) and my 5500W onboard Onan generator will consistently pull right around 100 amps +/- a bit. The last time I check it, the ambient temperature was around 70° F outside.

 

[d23haynes57]

I have a clamp on meter that measures either AC or DC (different setting of course) and my 5500W onboard Onan generator will consistently pull right around 100 amps +/- a bit. The last time I check it, the ambient temperature was around 70° F outside.

While I would not fully recommend still within limit for even a single 100 A/H battery with 100 amp BMS.

Dennis

 

[triplethreat]

While I would not fully recommend still within limit for even a single 100 A/H battery with 100 amp BMS.

Dennis

Yea, I'm good to go. I did a DIY build of a 302 A/H LFP battery back in early 2022 and used a 200A BMS. I knew the generator starting motor would likely be the highest amp draw in my camper, and it is, thus the 200A BMS vs. something larger.

 

[DonTom]

I just did a search on my Brave browser for the Onan 5500 in this motorhome.

Look at the "Battery Compatibility" part below:

"The Onan 5500 starter motor typically draws 75-80 amps during the cranking process, according to measurements taken with shunt meters. While the generator's manual often specifies a requirement of 350 Cold Cranking Amps (CCA), this rating refers to the initial inrush spike which lasts less than half a second and is defined for lead-acid batteries that experience significant voltage sag.

• Sustained Cranking Current: Approximately 75-80 amps once the initial spike settles.
• Initial Inrush: The peak spike is captured by the 350 CCA rating, but actual sustained load is much lower.
• Voltage Impact: Lithium (LFP) batteries maintain a stable voltage (~12-13V) compared to lead-acid batteries (~8-10V during cranking), resulting in lower amp draw for the same power requirement.
• Battery Compatibility: A single 100Ah LiFePO4 battery with a BMS supporting 200-280 amps for short bursts is generally sufficient to start the generator."

And just one of those batteries:

"Continuous Discharge: 200A max
•
Surge/Peak Discharge: 1000A for up to 5 seconds (5C rate)
•
BMS Current Rating: 200A (both charge and discharge)."

And I will have two of them.

-Don- Kingston Campground, NV

 

[garyb1st]

Have two Lion Energy 105 aH lithium batteries. Just replaced the two lead acid and wired them in parallel. That was all. No battery to battery protection and used existing converter until it died of natural causes. That was about 5 years ago.

Replaced with a new WFCO Auto Detect. Got that since original died while on travel and only option for immediate replacement was one they had at Camping World. As best I know, it's never charged in the lithium mode. So the new WFCO works just like the old.

FWIW, they start the Onan 5500 without hesitation. The only issue has been overcharging the starting battery. Turning off the salesmans switch didn't work. My solution was to install a shutoff on the starter battery. That was a year ago and so far over 3,000 miles no problems.

 

[DonTom]

The only issue has been overcharging the starting battery.

What was causing that?

-Don- Kingston Camp, NV

 

[garyb1st]

Not sure why. Maybe the way gas coaches were wired back in the day. In any event, if I didn't turn off both the house and chassis batteries at the Battery Control Center, the batteries would slowly and continuously discharge. Before I had the shutoff installed, while parked at my home and plugged into the 120v house power, the lithium batteries discharged at a rate of about 1% a day. After installing the shut off, the batteries discharge at a rate of maybe .005%.

 

[Lou Schneider]

In spite of warnings to the contrary, I've been running 3 non-golf cart rated 12 volt 100 a/h LiFeP04 batteries in my golf cart for a couple of years now. 36 volts in series, cheap Chins batteries. No issues. When I first put them in I measured the locked rotor current (the highest possible - full throttle into a stall caused by locked brakes) at 80 amps. Running load is approximately half that. Well within the battery's 1C (100 amp) continuous rating.

 

[DonTom]

I am thinking about changing them to two of these in parallel. And adding a lith converter since the stock Xantrex Freedom X 1200 has no lith profile.

Boy, was I confused. I was thinking the converter was built into my inverter. I just double checked things and discovered my inverter is only an inverter and 2022 Class A has a PD 4590 (90-amp) with a LI battery switch. Not real obvious because of its location, and a lot smaller than I would expect.

This PD converter draws 17.7 amps @ 120 VAC (2,214 V*A /1,550 useable watts input) 1,314 watts output at 14.6 VDC, or 90 amps to charge with. Looks like really didn't need the new lith convert I just purchased.

It's a 50 amp RV, so not a problem there, but I think that is more current draw than any other item I have owned @120 VAC.

However, Amazon AI says the recommended charge rate on these batteries is just 20-amps each (40-amps total or 584 watts @ 14.6 VDC), which seems rather low for 400 AH worth of lith batteries, but these batteries are built in she smaller cases. But it also says since my PD4590 has a lith profile, it should be good to go as is.

If that is the case, I have a spare new lith converter I will not be able to use for the 400 AH batts in my Class A as I am already over the recommended charge rate. But I can use it with the large 300 AH battery in my Y2K RV, as it says 60-amps is the best charge rate for it. I think I have a 40 amp lith converter in it now, which I can remove and replace with the 60 amp.

A bit strange that I can safely charge my 300 AH Lifepo4 battery with more current than my 400 AH worth of Lifepo4.

-Don- Auburn, CA

 

[triplethreat]

I would check the stats on LiTime's website. I'm putting this link here, see if that is the battery you are considering to get. Recommended charge amps is 40A (0.2C), but the max continuous charge current is 200A (1C). They likely suggest the lower current charging to help with cell balancing, so going over the 40A by a bit would not bother me at all....

https://www.litime.com/products/12v-200ah-xtra-mini-rv-lithium-battery?variant=47608591417564

 

[DonTom]

They likely suggest the lower current charging to help with cell balancing, so going over the 40A by a bit would not bother me at all....

I hope you're correct that it is only for the cell balancing, which makes sense as then the slower the charge the better, But balancing just once in a while, such as when boondocking with only solar should take care of that, so it's not really much of an issue,

see if that is the battery you are considering to get.

The two batteries that I should receive here in two days are these two. Going from two six volt L-A in series (225 AH) to two 12-volt Lifepo4 batteries in parallel (400 AH):

-Don- Auburn, CA

 

[DonTom]

t. Recommended charge amps is 40A (0.2C).

I was glad to see that, because Amazon said 20 amps each for the same battery. A 40-amp charge rate each is 80-amps for both so even my 90- amp possible charge rate is close enough, besides the fact I assume it will not charge long at 90-amp as it will drop with the SOC--if it is ever that discharged to begin with to draw the 90 amps which is very unlikely,

So it looks like there is really no issue at all with my 90-amp converter--thanks for the info.

-Don- Auburn, CA

 

[triplethreat]

I was glad to see that, because Amazon said 20 amps each for the same battery. A 40-amp charge rate each is 80-amps for both so even my 90- amp possible charge rate is close enough, besides the fact I assume it will not charge long at 90-amp as it will drop with the SOC--if it is ever that discharged to begin with to draw the 90 amps which is very unlikely,

So it looks like there is really no issue at all with my 90-amp converter--thanks for the info.

-Don- Auburn, CA

You're welcome Don. One thing that I do when charging my DIY LFP battery (302AH) is the converter/charger I selected for it has settings and I selected the setting that outputs no more than 14.2V max. My battery never gets close to the max cell volt of 3.65 or total of 14.6V. Yes, it takes a bit longer to charge that way, but I'm not in a real hurry, and to me, not approaching that max voltage is actually a bit better for longer battery life as well as cell balancing.

 

[DonTom]

not approaching that max voltage is actually a bit better for longer battery life as well as cell balancing.

Isn't cell balancing done at the very high end, such as when the batteries are nearly done charging or perhaps charging already done?

Or does setting a lower voltage limit only mean the balancing starts at a lower voltage?

-Don- Auburn, CA

 

[DonTom]

BTW, I just now received the 60-amp converter. If I put this in my Y2K RV, and remove the 40-amp, then I can remove the 90-amp from my 2022 and install the 40-amp to be right at the recommended level, But I do not think it is worth the trouble based on your messages.

BTW, I could be a little higher than the 90 amps on a sunny day. My roof solar is 190 watts (~13 amps), So I could be as high as 103 amps total.

Do you still think I am safe with such or should I use the 40-amp lower converter instead?

Oh, another option is I can unplug the solar when I am using the converter. Very simple to do because I installed a connection in serries with the roof solar at the controller so I can unplug when boondocking to add two more solar panels in series. I need to close this back up with a plug to use only the roof solar. If I leave the plug out, then no solar at all.

My gut feeling is none of this is an issue as everything (solar, converter, alternator) will be on a very low current float charge as the batteries near that 14.4 V in a rather short time, in most cases for me.

-Don- Auburn, CA

 

[bigbAZ]

I have a single 100ah LiFeP04 and when it's fully charged it will start my Onan 3200 diesel just fine, but when it's discharged down to around 50% it won't do it. I can still start the generator if I engage the boost. I may be able to start it just by starting the coach but I haven't tried and I'm not sure if it would get enough through the DC-DC charger. Might test that theory tomorrow as my LiFeP04 is down around 35% right now.

 

[triplethreat]

Isn't cell balancing done at the very high end, such as when the batteries are nearly done charging or perhaps charging already done?

Or does setting a lower voltage limit only mean the balancing starts at a lower voltage?

-Don- Auburn, CA

I pretty much have total control over my BMS via the settings. Remember I built the battery and bought a BMS, so pretty much every possible setting is available to change/adjust where I want it for my application. On mine, since none of my cells should ever see more than 3.6 volts (14.4 total for the battery), I have my balancing start at 3.4V if there is at least a 0.02V differential between cells. the normal cell differential usually stays below that 0.02V. Realistically, if a cell hits 3.45V that is very, very close to being fully charged.... 99.xx SOC.