Starting an Onan 5500 With LiFePO4 House Batteries

[DonTom]

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%

That is to be expected, but I will have 400 AHs worth of LifePO4 in a couple of days.

I already have my RV ready for the install. I have all the lead acids removed, my solar off and converter and solar controller ready for lith, and the BIM unmounted and the starter battery removed too.

My Go-Power Solar Controller also charges my engine battery, which is "batt 2". I have it set for Li on batt one and LA for batt two.

And I remembered to take photos of everything before starting the job, such as this one:

-Don- Auburn, CA

 

[triplethreat]

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

I think you would be fine charging with the 90 amp, but I've always chosen to charge at a lower/slower rate. I bought a Meanwell brand converter/charger for my application that is rated at 750 Watts. The most I ever charge at is 43.xx amps....that is all she's got..........so low and slow is my preference, and keeping the cells/battery away from that 3.65 and 14.60 number

 

[DonTom]

, I have my balancing start at 3.4V if there is at least a 0.02V differential between cells.

I am curious how that works. What is changed to start the balancing at a lower cell volage?

-Don- Auburn, CA

 

[DonTom]

I think you would be fine charging with the 90 amp,

I will probably never be discharged enough to see the 90-amps anyway. And when it gets to full, it will not be drawing much of anything, so I also think I will be fine, even with the solar on, when I have shore power, I will turn off the solar, such as when at an RV Park.

I thought of even another option. The converter I added for my toys (ham radio), MW oven and etc. in my Class A is already a 40-amp. I did this before my first long trip in it (which was to the Everglades of FL).

But I do not see a reason to not use the stock stuff on my new batteries,

I was surprised to find a 90-amp converter in my Class A. I have never seen my LA batteries draw anything near that.

The whole LI thing is overkill for me, I normally am at ~85% SOC even with my LA before I hit the sack, as I always check my Smart shunt then to see where I am at, looking more at voltages than SOC%, because I have my soc calibrated for 100% when to know when to shut off the genny when boondocked--when the batteries no longer draw any current for 100% SOC.

-Don- Auburn, CA

 

[triplethreat]

I am curious how that works. What is changed to start the balancing at a lower cell volage?

-Don- Auburn, CA

When you have a BMS that is a separate unit instead of being built into the battery, like I do, most all of those BMS' have BT and an app for accessing them. With that app, you have to set up all the parameters relative to whichever battery build you are doing......AH, Voltage, etc, etc. So on mine, and with me having the charger that I have and the setting I use for charging, I simply go into the app and decide what voltage I want to start the balancing at...and set the differential trigger point. On mine, I could have chosen any number and trigger point voltage (within range of course). I simply chose the numbers that work for my setup because of my max voltage of 14.2V.

If you notice, I posted 14.2V ^^^^. In my previous post I had said 14.4.....THAT IS INCORRECT....I had a brain fart....the output is a maximum of 14.2V, the way I have it set. The 14.4V is the default setting as it came from the factory on that converter/charger. I have it setup for 14.2V

NOTE: I just edited my previous brain fart post and changed the output voltage number to 14.2V

 

[DonTom]

My new Li-time batteries that were not expected until Friday came today!

The first thing I did was to RTFM.

This I believe more than any other source and this manual only covers my Li-Time Minis so it's not a generic manual.

So here are the real true facts:

Recommended charge rate: 0.2 to 0.5C or 40 to 100 amps to each of my 200 AH batteries.

This means I can charge my two batteries at a total of 200 amps! ~2 hrs. empty to full.

My 60 amp Li-Time charger/converter is coming in handy right now, as the manual says I should charge each battery to 100% SOC before I connect them together. I am charging one to full right now, and when it is done, I will charge the other. The Li-time charger itself will tell me when it is at 100 SOC (>13.33 volts at rest).

Then it says I should connect them in parallel unused for 24 hours or longer.

This is to ensure best cell balancing before they are being used,

No hurry as I do not yet have my Li-BIM, that should be here on Friday. I will have everything ready by then. I am not sure when I will use this RV next anyway. I will most likely do a trip in my Y2K before I do a road test on my 2022 Class A.

I found a bunch of new unused 175 amp Anderson cables with 24" of 1AWG, in my RV junk box that I didn't even know I had. All in an unopened package, I decided to use two of them to tie the batteries together and another to feed to house with from the two batteries in parallel.

My RV had six wires going to the positive terminal, so I put in a large terminal strip so I will only have one wire wire on each side of the battery pair.

In other news, I checked to see what converter I had in my Y2K RV. It is an 80-amp PD9180AL. Twice the AH rating that I expected. I have never seen it charge at anything near that rate. I assume to get that high rate of charge, the battery has to be quite discharged-- but to what around 25% SOC or what? I never let my batteries get that low so I do not know.

This 400 AH of Lith is a big overkill for me, I also have the 300 AH Li-Time battery in there that I added for my toys, so that is 700 AH worth of Lifepo4 battery total. I am getting close to 10 KWH worth total!

-Don- Auburn, CA

 

[DonTom]

I now have the entire motorhome ready to drive off with my new LifePo4 batteries. All is working well, and I adjusted my solar controller, Converter and even a setting in the Inverter (so it will drop out at a higher voltage than before) for the 400 AH worth of new lifepo4 house batteries .

I also have my other 300 AH Li-time in there too, so I do not load down the stock system by running the MW oven, Keurig, hair driers, ham radio junk and other high current items when using the larger inverter I installed years ago instead of the genny.

I changed the engine battery from flooded lead acid to AGM and set the solar controller for it too (separate settings for each battery).

I spend a lot of time changing other things too. I now have the two Li-time 200 AH batteries in parallel with 175-Amp Anderson cables and the output of the batteries is on another 175-Amp Anderson cable. I also have the smaller Anderson 125 Amp cable installed so I can charge and balance them when not connected to the motorhome with my 60-amp Li-Time Lifepo4 converter, in case I ever feel such is necessary. The only wires that touch these batteries are the Anderson cables. I added large busbars like these to make that possible.

Needless to say, the genny starts up super fast from these new batteries that AI said would not work.

One minor issue is when the Engine battery is disconnected, it sometimes makes the leveler LEDs all light up and then will not work. All I had to do is disconnect the engine battery for a few seconds to reboot it and then it came back to normal.

Other than being time consuming, the modification went very well.

-Don- Auburn, CA