Independent starter battery size for 20kw gen?? - Printable Version
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Independent starter battery size for 20kw gen?? - Gem930 - 12-18-2024
I’m switching out my batteries and inverter to a 48 volt victron system. This is obviously causing me to have to rework the 12v systems in the coach. Most of what I need to accomplish can be done with a 48 to 12 volt Dc to dc converter (or actually 2) but the generator start system has me thinking an independent start battery might be the best option. I suppose I could change the generator start over to the chassis batteries (as I’m going to with the slide hydraulic motors) but I fell like having its own battery may be a good idea. I could always wire up a starter relay to the chassis batteries as a back up. Can anybody think of a reason why I shouldn’t do this and any recommendations on a battery size. Just for fun I used my 330 cca lawnmower battery and it seemed to start the generator fine, but it was a brand new battery.
RE: Independents starter battery size for 20kw gen?? - Gem930 - 12-18-2024
It just occurred to me that it may not be real easy to separate the generator, slide hydraulic motors, house lights and heating systems up. There are 3 positive wires in my battery compartment. One I know goes to the inverter and I’ll utilize it solely for the 48 volt path to the new inverter. The other two I’ll have to energize independently and see what is on what wire.
This just got more complicated!
RE: Independents starter battery size for 20kw gen?? - Jack Houpe - 12-19-2024
We went 48v growatt 8k split phase inverter but our coach had six 8d house batteries so I just kept two 8ds for the house and charged them from the 48v system which is charged from the solar system and growatt split phase inverter charger. The system works flawlessly for over 1 year now.
On another note we have a Prevost bus and did the victron conversion with 4000 watts of solar and if I had to do it over again I would go with growatt. Victron is great equipment but the only way to utilize your solar potential is unplug from the grid (boondocking) or turn on inverter only. Driving down the road the system will run the AC heat pumps with no problem long as the sun is out but if your plugged into a campground that charges by the kilowatt hour your screwed. The growatt has 3 priority's 1 solar (Solar energy provides power to the loads as first priority) first 2 UPS mode (runs on grid all the time till grid goes down) 3 Solar Battery (Solar energy provides power to the loads as first priority.
If solar energy is not sufficient to power all connected loads, battery energy will supply power to the loads at the same time) You do not have these settings with victron. Just my opinion from experience.
RE: Independents starter battery size for 20kw gen?? - bestgenman - 12-19-2024
Greg, a 4tn Yanmar does well with a group 24 battery.
RE: Independents starter battery size for 20kw gen?? - Gem930 - 12-19-2024
Jack thanks for the info…. You must not be the only person that was unhappy with the way the victron prioritized the power supplied, as they have upgrade the firmware to do exactly as you describe. I have installed a Growatt in a system a year or so ago and really like them (especially the price) but since we “moochdock” at the kids house in California and they only have 15 amp power , Victron’s additional feature of limiting shore power amps and assisting with the difference made them the only choice.
Gordon thanks for the info. I’m going to go out and try to see what systems are connected to what positive feed wire. If the slide hydraulic motors are on the same feed as the generator, I’ll just connect them to the chassis batteries and then feed the rest of the house 12 systems with the DC to DC converter from the 48v. I hope that is the case as I do not want to pull continuous loads from the chassis batteries then the engine is not started.
On a side note, can anyone explain the 3 way switch on the emergency start solenoid? I obviously need to disconnect this when it have 2 separate voltage systems, but was surprise to see it was a 3 position (center off) switch.
RE: Independent starter battery size for 20kw gen?? - Richard - 12-19-2024
Yes . The purpose of the switch is to activate the merge solenoid joining the house and chassis batteries. One position uses voltage from the house side to close the solenoid. The other position uses voltage from the chassis side. That way no matter which side is dead the solenoid can be activated.
Gem930 - Gem930 - 12-19-2024
(12-19-2024, 08:26 AM)Richard Wrote: Yes . The purpose of the switch is to activate the merge solenoid joining the house and chassis batteries. One position uses voltage from the house side to close the solenoid. The other position uses voltage from the chassis side. That way no matter which side is dead the solenoid can be activated.
ahhhh that makes sense…. I’ve had a few coaches and have only ever seen it one way! Thx
RE: Independent starter battery size for 20kw gen?? - Gnawrocki1 - 12-19-2024
I too went to a 48V system and decided to use the engine batteries only for all 12V and to charge from the 48V using a solar controller (vs a battery to battery charger), all by Victron, I saw no need to add another battery for the loads. I have not had any issues with the system operating fine, even though the engine batteries are 7 years old and counting.
Gem930 - Gem930 - 12-19-2024
(12-19-2024, 08:48 AM)Gnawrocki1 Wrote: I too went to a 48V system and decided to use the engine batteries only for all 12V and to charge from the 48V using a solar controller (vs a battery to battery charger), all by Victron, I saw no need to add another battery for the loads. I have not had any issues with the system operating fine, even though the engine batteries are 7 years old and counting.
So you are using a solar charge controller connected to your batteries instead of panels? I wondered if that would work. I ordered 2 25 amp 48 to 12 V DC Buck converters to do the same thing, but I think the charge controller might work better.
RE: Independent starter battery size for 20kw gen?? - cwl1979 - 12-19-2024
As we all know, no two Newells are identical. That said, under your coach, where all the electrical connections are made, you should find three 4/0 wires and somewhere in the area should be a larger 8 AWG wire. The 4/0 wires go to the following places.
1. From the chassis batteries. This wire should head towards the rear or the coach
2. From the house batteries. This should be the easiest to track down.
3. To the generator. This should run up and through the "pipes" in the center of the coach.
4. 8AWG powers the Aqua hot
5. In typing this I've realized i don't have a merge solenoid and should probably put one in.
Hope this helps save you some time tracing wires.