Lithium over Lead Acid Batteries

[SolarPoweredRV]

Onan 5500 generator.

Yeah. Going to a 100AH battery fine.

Having to get 4 batterrie$$ to be able to start the generator. I can buy a ton of gas for the genset for $3000

I was looking to "run non AC loads for longer" between solar and lithium, but still run the genset when AC is needed, or it's been cloudy for x days.

The only having to run for maybe an hour to charge batteries without solar was enticing.

The lack of cranking amps (genset and HYD pump) is what holds me back.

I believe JCR GD only mentioned that he had upgraded to 4 Lithium batteries for reasons other than starting his Genset. He said that he was starting his Genset just fine with only two Lithium batteries.

I am not sure how you came to the 4 battery, $3,000 conclusion.

In regards to operating your Hydraulic pump, a single 100ah Lithium battery can easily operate your pump, as long as your battery is capable of a 1c discharge rate (check the specs of your battery, many have a 1c discharge rate and a lower charging rate i.e.: 0.25c or 0.5c).

In your situation, where you might need more than a single 100ah Lithium battery is your need to start your Generator, this is where the recommendation for having two Lithium batteries comes in to play. Based on the $299 price of the Lithium batteries mentioned in the first post above that would only run you $600, not $3,000.

If you are actually looking to "Run Non AC loads for longer", 200ah of Lithium batteries would be a good starting point for your battery bank. You may also find, just like JCR GD did, that you want more battery capacity and eventually wind up with 400ah of battery storage.

[timelinex]

In your situation, where you might need more than a single 100ah Lithium battery is your need to start your Generator, this is where the recommendation for having two Lithium batteries comes in to play. Based on the $299 price of the Lithium batteries mentioned in the first post above that would only run you $600, not $3,000.

I'm new to Lithium batteries, so I'm just checking that I understand correctly. My Onan 5500 may not start if I only bought a single 100ah Lithium? But 2 of them is fine?

[JKellerJr]

I'm new to Lithium batteries, so I'm just checking that I understand correctly. My Onan 5500 may not start if I only bought a single 100ah Lithium? But 2 of them is fine?

I have a buddy that starts his onan 5500 without issue on 2 BB 100ah lithium’s. Not sure if all lithium’s are the same in regards to cranking power.

[SolarPoweredRV]

I'm new to Lithium batteries, so I'm just checking that I understand correctly. My Onan 5500 may not start if I only bought a single 100ah Lithium? But 2 of them is fine?

I have a buddy that starts his onan 5500 without issue on 2 BB 100ah lithium’s. Not sure if all lithium’s are the same in regards to cranking power.

Yes, a single 100ah Lithium (LiFePo4) battery may not start your Onan Generator.

The issue is not because a single battery does not have enough energy to start the Generator, the issue is that the battery is not designed to produce enough power all at once. Lead Acid batteries are often rated with Cold Cranking Amps (i.e.: 675 CCA), and can produce a lot of power quickly (in short bursts). Lithium batteries have a built in Battery Management System (BMS) which limits the power output of the battery through internal electronic circuitry to a pre-set limit, most often for a 100ah LiFePo4 battery the limit is set to 100 amps. This 100 amps is not enough power to start your Generator.

However, two LiFePo4 batteries, properly wired, can deliver 200 amps of power, which should be enough to start your Generator (three LiFePo4 batteries would be better).

When I say "Properly wired", I mean each battery is tied to a Buss Bar, and the load of the generator is then attached to the Buss Bar. Why you should use a Buss Bar in this application is covered in the attached research paper on wiring batteries in parallel. Using a Buss Bar system is the only way each battery can contribute their full energy potential toward starting your generator.

Here is the research paper:

Note: I have also included an example of the type of Buss Bar I am talking about (you will need one for the Positive cables and one for the Negative cables).

[rootusrootus]

Personally, I'd probably just figure out how to use an small AGM battery just for the generator before I'd upsize all the wiring to make LFPs work for that. Starter cables can be relatively small because they're located so close to the load. Wiring up the house LFPs to support 300A would be an expensive PITA.

Just IMO. YMMV, etc.

[ajg617]

I have a buddy that starts his onan 5500 without issue on 2 BB 100ah lithium’s. Not sure if all lithium’s are the same in regards to cranking power.

This is exactly what I have and had no problem starting the factory Onan/Cummins. Ran the Generator pretty much every morning for coffee - some mornings after a full night at a Harvest Host with the furnace going.

[SolarPoweredRV]

Personally, I'd probably just figure out how to use an small AGM battery just for the generator before I'd upsize all the wiring to make LFPs work for that. Starter cables can be relatively small because they're located so close to the load. Wiring up the house LFPs to support 300A would be an expensive PITA.

Just IMO. YMMV, etc.

If you are wiring the battery bank to run a 3000 Watt Inverter, the wires are already properly sized to start your Generator (generally 4/0 on a 12v system).

[FT4NOW]

Didnt see this thread earlier. On my 399, I had the Onan 5500 watt generator and 1 Lions Energy 105AH battery (UT1300), and there was never any trouble running the generator, and I used it pretty frequently.

[CX500T]

Looking at how it is wired, I wonder if you only have the 12V Gen leads on the Generator Start battery (and not otherwise hook them to the house loads/chargers) if the generator will recharge it's own starter battery while keeping it independent of the house load. Now, having this tie into the Auto Start function on the One Control, it would basically depend on the genset battery being able to start the genset which might not be 100% always if you don't keep it charged via running the genset occasionally.

I have "portable" generators that rechage their 12V battery independent of the generator side, but I'm not 100% sure on the Onan 5500 and the manual is less than clear on this.

[Harvestmoon]

When I say "Properly wired", I mean each battery is tied to a Buss Bar, and the load of the generator is then attached to the Buss Bar. Why you should use a Buss Bar in this application is covered in the attached research paper on wiring batteries in parallel.

Great info and timely since I am sketching out an electrical upgrade for our new 22MLE. I have been a 2xFLA guy, which easily satisfied our modest off grid power needs in our previous TT along with a portable panel. I am a big fan of the 12VDC compressor refrigerators that are rapidly becoming the norm, but they do cause us boondockers to sharpen our pencils on daily energy demand. Exploring our 22MLE, there is a practically ready-made space under the dinette seat, right next door to the converter and electrical bay, which could conveniently house a couple of batteries and an inverter. Of course, this means going to a sealed battery, so I had been thinking AGM. As you point out, with AGMs being $200ish for 100Ah and knock-off LFPs out there for $300ish, going LFP seems like a no-brainer. Especially considering GD is wisely now installing lithium ready converters and solar charge controllers, there's not much left to do.

Thanks for attaching the paper on batteries in parallel. Bus bars can be the best choice as you collect more batteries. For the special case of 2 identical batteries in parallel, I think lots of us use the "Method 2" described by the paper, which is to connect to positive load lead to one battery and the negative load lead to the other battery, which balances out the battery-to-battery ties. I have seen most 2 battery installations done this way because it is simple and it works. Quoting from the paper, "Finally, if you only have 2 batteries, then simply linking them together and taking the main feeds from diagonally opposite corners cannot be improved upon. Once the number of batteries gets to 3 or more then these other methods have to be looked at."