dickandlois Report post Posted April 7, 2016 The question just came up regarding replacing the coach batteries with GEL cell and still charging Wet cell batteries from a Inverter / Charger. NOW! this leads to another issue: If one replaces the chassis wet cell(s) with GEL cells, what changes need to be made to the engine alternator to properly charge them? I have no clue at this time, but think it is an item that requires more research. I refer this to as opening, Pandora's Box!!! Thinking to water got muddied up some! Rich. Share this post Link to post Share on other sites
wolfe10 Report post Posted April 7, 2016 Rich, Reality is that motorhomes do NOT have "smart regulators", so for all intents and purposes, all the alternators are "stupid". Yes, smart regulators have been available for a long time-- we have had them on our sailboats for decades. But, they are not inexpensive. The good news is that even though all battery types are somewhat overcharged by alternator output of around 14 VDC, the time the engine is running is actually a pretty small percent of the time. If you have a smart charger or smart inverter/charger, you probably notice if you plug in after driving for awhile that the smart charger goes in to float mode pretty quickly. Alternator overcharging is the reason. Share this post Link to post Share on other sites
dickandlois Report post Posted April 7, 2016 Thanks for the update and information! Never owned a large boat of any kind, answers the question regarding the alternator and GEL cells. Rich. Share this post Link to post Share on other sites
jleamont Report post Posted April 7, 2016 Brett, this post and the few others made me place a call to find out what the problems we had (called my old employer), during the call the light bulb went on in my head. brought back the memories. Two issues listed below 1, We were running the Optima battery, No issues with a day cab tractor, when you put them into a sleeper tractor (batteries have no air flow around them unlike like a day cab) they would over heat. Burnt two tractors to the ground, cause of fire was ruled overheated batteries, it happened while driving in both instances, which might go back to the post above with the alternators. In this case both were equipped with Delco 40SI, which does have remote sense to monitor the batteries state of charge, so you would think it would adjust the current on a fully charged battery. After further inspection most of the sleeper fleet had signs of over heated batteries, (melted housings, disfigured wire loom in the area of the batteries etc.) They switched them all out with wet cell's on sleepers only, no more issues. No signs of over heating on the day cabs, also equipped with the same alternator and battery configuration. Both units came with the Delco/Optima equipment from their manufactures, they were not added after. 2, The AGM battery paired up with a starter motor equipped with an over crank protection system, when the AGM drops below 12.0V the starter will not engage. I can think of a few things that could have caused the #1 concern above, but since I mentioned some concerns on a different post I wanted to dig into it to refresh my memory and share it. Share this post Link to post Share on other sites
manholt Report post Posted April 7, 2016 Joe. I'm not familiar with a "Sleeper Cab", just my lil old Coach. My house batteries are located in a basement bay and I suspect it has plenty of air circulation...where are they in a "Sleeper Cab"! Share this post Link to post Share on other sites
jleamont Report post Posted April 7, 2016 Just under the drivers door, they do not get much air if any. They are accessed by removing a panel with the drivers door open. Share this post Link to post Share on other sites
manholt Report post Posted April 8, 2016 Joe. You, just made my day! I'm so HAPPY to know that the RV Industry is not the only craps shoot out there! Share this post Link to post Share on other sites
w5txxt5w Report post Posted April 15, 2016 If there is a battery isolator between the chassis batteries and the house batteries, there should be no issue. The alternator will produce 14-14.5 volts when running. The isolator will have between .3 and .6 volts drop going to the house batteries which places the voltage near the Gel float voltage and should not cause an issue. If there is not an isolator, then that's another problem as the house batteries can discharge the chassis batteries or visa versa. Typically the MH has a switch on the dash that allows one to use the coach battery to start the engine if there is an issue with the chassis batteries. When this switch is activated, the isolator is bypassed and coach batteries are connected to starter and usually to the chassis batteries at the same time. Share this post Link to post Share on other sites
dickandlois Report post Posted April 15, 2016 9 hours ago, w5txxt5w said: If there is a battery isolator between the chassis batteries and the house batteries, there should be no issue. The alternator will produce 14-14.5 volts when running. The isolator will have between .3 and .6 volts drop going to the house batteries which places the voltage near the Gel float voltage and should not cause an issue. If there is not an isolator, then that's another problem as the house batteries can discharge the chassis batteries or visa versa. Typically the MH has a switch on the dash that allows one to use the coach battery to start the engine if there is an issue with the chassis batteries. When this switch is activated, the isolator is bypassed and coach batteries are connected to starter and usually to the chassis batteries at the same time. Bob, Welcome to the FMCA Forum ! There are a number of coaches that do not use battery isolators. One item that can be left out to keep cost down. Many coach builders use an Isolater / Emergency Start Relay to keep the Chassis and Coach Battery banks separated. This type set up keeps the coach batteries isolated from the charger / inverter charging system. Many builders bridge the 2 battery banks at the Isolator / Emergancy start relay so both banks get charged from the inverter and alternator.The coach batteries get charged from the inverter charger, but the chassis batteries do not get charged. When on the road this set up charges the chassis batteries, but not the coach batteries. Some builders have changed this setup by adding steering diodes in the alternator wiring to allow the coach batteries to charge from the alternator. Makes for some interesting challenges when trying to problem solve this areas charging system. Rich. Share this post Link to post Share on other sites
jleamont Report post Posted April 15, 2016 My C didn't use an isolator, the switch on the dash energized a relay (looked just like a Ford Starter relay) to bridge the two batteries. When I bought it had an AGM for a house battery (12v single) and the factory wet cell under the hood for the engine. My battery light would come on while driving after a while (several hours) when the AGM went bad (3 years later) I switched over to two 6v wet cells, never saw that light again. The odd part was even with the light on it was charging at 13.5v. Class A we have now has an isolator. Share this post Link to post Share on other sites
rsbilledwards Report post Posted April 21, 2016 This topic and a hands on would make for a good seminar by somebody that knew what they were talking about, including the headaches isolators present when they go bad...been there! Bill E Share this post Link to post Share on other sites
