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Phil_C's avatar
Phil_C
Explorer
Jul 04, 2023

Making the change to lithium and starting the Onan.

Short story of "McGoo'ing" my way through it.

I replaced my 2 wet deep cycle batteries with a SOK 100 AH. I did this on the research my buddy did while making the change for his trailer. My buddy though doesn't have an on board generator. So, as I know now, while everything looked great with the 200 watt solar system charging the new battery when I went to start the generator I sent the battery into protect mode. After the initial panic and "WTF did I just do to a 600 dollar battery!" I found out how to reset it and that there are some lithium's that can be starter batteries and some that are only house batteries and limit current to about 100 amps. That is what I have in the SOK. This was last year. I ended up putting one of the lead/acids back in there wired only to the generator which worked last year.

This year I bought a little 6 AH starting battery and tried to use a battery isolator to charge both from the solar system. after wiring in the Victron isolator I discovered that you cannot do this as the charger has to be directly connected to the bank it is charging.
No problem right? I'll just charge the little battery has needed, this worked fine for microwaving stuff for dinner when you only run the gen of a few minutes. I needed the AC last week which leads to the next discovery.

Not only do these Onan generators lack charging capacity for the starting systems which I knew about, they have to have voltage for the field and the spark, a 6 AH battery will crank it a few times but will only run it for about 4 hours.

Too fix this issue I need to get a Xantrex Echo charger to charge from the house system to the 6 AH battery. From the measurements I made, I should be about to fit another 100 AH SOK and the charger and little starting battery in the space that my AF 996 has.

I did a quick check and it looks like this is still a less expensive way to go than buying lithium starting/house batteries.

Though I would share this with the group as I have learned so much here.

Phil
Truck Campers
  • KansasKen's avatar
    KansasKen
    Explorer
    Jul 05, 2023
    thanks for posting this, I had not given thought to weather the LI-ion batteries would start my Onan. I was just about to do a conversion from 4 100ah AGMs to 4 100ah Li-ions so the timing of this post saved me from the same situation. I’ve never run the Onan more than a few minutes, so the 6ah solution will not be a problem for me. I think your solution would be a great idea to copy.
  • pianotuna's avatar
    pianotuna
    Nomad III
    Jul 05, 2023
    Hi Phil,

    I solved the generator battery charging issue by using an SiO2 (8 amps) and a relay that doesn't close until it 'sees' 13.5 volts.

    I needed the charging to operate the remote electric start from pinella's.
  • Tom_M1's avatar
    Tom_M1
    Explorer
    Jul 05, 2023
    I have a Renogy 170AH battery and a Generac QP40 3.6KW generator. The battery is four years old. I don't know how much current the starter draws, but I have no problem starting the generator.
  • deltabravo's avatar
    deltabravo
    Nomad
    Jul 05, 2023
    Echo Charge is awesome. I remember when Heart Interface invented that gem back when I worked there in the late 90s.
    Heart was the predecessor to Xantrex.

    I have a pair of Battleborns in my AF 992. They start my Onan 2500 inverter generator fine.
  • skanj0's avatar
    skanj0
    Explorer
    Jul 06, 2023
    My onboard onan starts fine from my 300 ah lithium battery. The generator starter leads are connected to positive and negative buss bars fed from the Lynx Distributor. Its a 2.5k onan.

    Are you connecting directly to the 2 lithium batteries or elsewhere in the system?
  • StirCrazy's avatar
    StirCrazy
    Moderator
    Jul 06, 2023
    KansasKen wrote:
    thanks for posting this, I had not given thought to weather the LI-ion batteries would start my Onan. I was just about to do a conversion from 4 100ah AGMs to 4 100ah Li-ions so the timing of this post saved me from the same situation. I’ve never run the Onan more than a few minutes, so the 6ah solution will not be a problem for me. I think your solution would be a great idea to copy.


    they will, you just have to have enough current capability to meet the requirements of your genny for amperage. one LFP depending on the installed BMS may not put out enough amperage, if that is the case then you need to have more in parallel to increase the amperage available for starting.
  • Phil_C's avatar
    Phil_C
    Explorer
    Jul 10, 2023
    The BMS on my battery only allows a little over 100 AMPs for a very short time. The Onan's in our truck campers are listed to require 360CCA to start, I'm sure a good bit less than that will turn them over fine. I think the "manual" also says if you are starting below zero then use a 480CCA, but I'll never do that. Back to the 360 CCA and the BMS even with a second battery I think it was going to be around 230Amp'ish before the safety tripped, maybe it'd work maybe not.
    In my Camper the space I have for batteries is pretty limited even if you take out the side that they have in it. I can fit 2 SOK's in there with the little cranking battery.
    I thought about a relay that would switch when the transfer switch does when the generator is running, but the little battery manual reads like it wants the charger to limit the charge current. That and the fact that reaching the transfer switch to wire in the relay was going to be a real pain, I figured the money for that echo charger was worth that.
    For the money it is not a bad way to go, 2 house batteries and the cranking battery with echo charger. If cost wasn't an issue I'd would go with 2 Battle Born's, I think they make some that are rated as starting batteries, and just be done with it.

    Phil
  • StirCrazy's avatar
    StirCrazy
    Moderator
    Jul 11, 2023
    Phil_C wrote:
    The BMS on my battery only allows a little over 100 AMPs for a very short time. The Onan's in our truck campers are listed to require 360CCA to start, I'm sure a good bit less than that will turn them over fine. I think the "manual" also says if you are starting below zero then use a 480CCA, but I'll never do that. Back to the 360 CCA and the BMS even with a second battery I think it was going to be around 230Amp'ish before the safety tripped, maybe it'd work maybe not.
    In my Camper the space I have for batteries is pretty limited even if you take out the side that they have in it. I can fit 2 SOK's in there with the little cranking battery.
    I thought about a relay that would switch when the transfer switch does when the generator is running, but the little battery manual reads like it wants the charger to limit the charge current. That and the fact that reaching the transfer switch to wire in the relay was going to be a real pain, I figured the money for that echo charger was worth that.
    For the money it is not a bad way to go, 2 house batteries and the cranking battery with echo charger. If cost wasn't an issue I'd would go with 2 Battle Born's, I think they make some that are rated as starting batteries, and just be done with it.

    Phil


    ya you really must look at your amperage requirements when shopping for any type of batteries. there are some cheaper LFP batteries that will put out 200A of current and you can get a 270ah battery from dragonfly that is a 300amp output. I went with a 150amp BMS for my battery I built which is more than I'll every use for the camper but when I put three in the 5th wheel I will be able to run anything I want.

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