My genset starter is wired to the house batteries. This seems backwards to me. What's your opinion?
Pretty standard across the industry.
Designed like that. If you shut down engine and maybe leave the driving lights on and your start battery goes dead, you can start generator and close boost switch to recharge start batteries. It works the other way automatically from your alternator and isolator.
Thanks Jim I was thinking that I was more likely to run the house battery down while boondocking. New smart isolator will keep both charged while plugged or running genset. I now have a 80 amp 4 stage charger for only $30.
If you run the house battery down to where the genny doesn't start you are ruining the batteries.
What house voltage is too low for lead acid combo deep cycle/start? My genset isn't currently autostart. Years ago when I had sailboat I seen a cycle chart that compared life span to discharge %, maybe west marine
About 12.2 is 50% discharge. Wet cell life below that voltage is short.
General rule is 12.2 volts is 50% discharged, and many gen autostarts are set at this, or lower. Personally I think that is too low for lead acid batteries and will shorten your number of charging cycles. I start mine at 12.3 or 12.4. Investing in a trimetric or other battery monitor is a good idea.
You will then know your real battery capacity and lite off gen. accordingly.
Ours will start off of either bank. Isuzu requires 3-400. Ran cable to chassis battery's and installed a marine dual bank switch. Ends limit on boost switch. Both have independent solar. No issues so far. Can't bring myself to have genset auto start. Try to manage so it isn't necessary. Just a personal preference.
Chart (approximate, no/little load, no surface charge):
Chassis batteries start coach engine, house batteries start generator. Two chances to start a engine to begin charging. (not to mention boost switch on many Foretravels).
Some fancier coaches sometimes had a separate gen start battery
If all else fails. I always carry this one with 40 amp 12 volt charger. Had a buddy that got stuck in a field and ran both battery banks down, [left boost switch on], carried it out to him and he charged start batteries for 30 min. and started coach. It is as quiet as a Honda 2000 and runs about 12 hours on less than a gallon of gas. Great for boondocking if you don't want to run your big gen. https://www.youtube.com/watch?v=FEHVQd9WG6Y