Failed battery isolator October 08, 2021, 06:53:41 pm On the way home from a LD group campout at June Lake, CA on September 24, about 30 miles from home, I noticed that all of the Ford instruments had gone dead. And our E450 seemed to be running in some sort of diminished capacity, moving but struggling a bit. Transmission shifts in particular seemed problematic. It was Friday and on Saturday we were due to continue on a three month trip around the west.Luckily we'd left camp early so it was just before 8:00am. I headed for our local RV service shop, Bob's Performance in Gardnerville, NV. We made it there, just barely. I knew by then that we had some sort of electrical problem, so left the engine running as I explained to Bob what had happened. I decided to turn on the headlights to see if they worked, and the engine died.We unhooked our Jeep and left the LD with Bob, who made getting us back on the road his first priority of the day, greatly appreciated. When I checked in later he told me we had a failed battery isolator and as a result also needed a new alternator and chassis battery. And, since the coach batteries had likely suffered and were five years old we had him replace those too.The isolator used by LD on our 2003 motorhome was hard to find, but Bob found one in Sacramento, had it shipped overnight, installed it Saturday morning and we were on our way, on schedule. So all's well that ends well.I don't really understand how all this worked but it reminds me of the space shuttle imploding because of relatively inexpensive gasket. That a failed isolator could cause so much trouble surprised me. Maybe others can explain that. It has me contemplating carrying a spare and learning how to install it. I know from talking with them that LD no longer uses our isolator. Maybe we should upgrade.Had we simply pulled over and shut things down perhaps the damage would have been minimized. But then we'd have been out along the road somewhere. In our circumstances I'm glad we continued home. We're now in Utah on our trip and everything has been working well. I've posted this simply so others might learn something from our experience. 7 Likes
Re: Failed battery isolator Reply #1 – October 08, 2021, 08:33:04 pm You have a diode type isolator. The anodes of the two diodes are connected together to the alternator output, and the other end, the cathodes go respectively to the chassis an coach batteries. Since current can flow only in one direction through a diode, this isolates the batteries, but allows both to charge from the alternator. However, there is a voltage drop across the diodes of about a Volt. The alternator reads the voltage at the chassis battery, and outputs therefore about one volt more than appears across the battery. At high currents, this means the diode is dissipating a lot of power, e.g. at 40A charge, the diode is trying to shed about 40 Watts of heat, and if heat conduction to the heat sink or airflow around it is insufficient, the diode can reach a temperature at which it fails. Failure mode is typically open circuit, and this means the alternator puts out an excessively high voltage trying unsuccessfully to raise the battery voltage. However, this high voltage will also put too much charging voltage into your coach batteries, boiling them over time.The temporary solution when this occurs is to jumper across the faulty diode. This will allow the chassis battery, alternator, and other chassis functions to work normally, but the charge voltage to the coach batteries will be low. This jumper should be removed in camp to avoid discharging the chassis battery.Steve 6 Likes
Re: Failed battery isolator Reply #2 – October 08, 2021, 08:50:04 pm Terry:We were driving to Vegas in a motor home we owned prior to getting our Lazy Daze in 2001. About 30 miles past Barstow, the engine died and wouldn’t restart. The motor home was towed to Barstow where the the problem was found to be a bad isolator. The isolator was replaced. The chassis battery was then charged by the repair facility and everything worked fine after that. The alternator was not damaged nor the chassis battery, nor the house batteries. As a result of the experience, I obtained a new battery isolator for our Lazy Daze, from Amazon and replaced the isolator last year while the existing isolator was still working.
Re: Failed battery isolator Reply #3 – October 08, 2021, 08:54:03 pm Thanks Steve. Great explanation.
Re: Failed battery isolator Reply #4 – October 09, 2021, 03:42:38 am Isolator must have shorted to ground to take out the alternator and battery? Usually the failure mode is open circuit, I think.
Re: Failed battery isolator Reply #5 – October 09, 2021, 11:02:57 am Quote from: hbn7hj - October 09, 2021, 03:42:38 amIsolator must have shorted to ground to take out the alternator and battery? Usually the failure mode is open circuit, I think.Not likely - the battery was discharged from lack of charging, and the alternator would have been damaged from over-voltage due to unregulated output. There is no connection from the diode terminals to ground. If a diode shorted, the condition might not even be noticed until the battery was drained while camped.Steve
Re: Failed battery isolator Reply #6 – October 10, 2021, 07:01:51 pm This whole deal makes a good argument for a mechanical isolator relay. I installed one in the old motorhome and never had a problem again. Thoughts?Jon
Re: Failed battery isolator Reply #7 – October 10, 2021, 08:58:57 pm Quote from: JonS - October 10, 2021, 07:01:51 pmThis whole deal makes a good argument for a mechanical isolator relay. I installed one in the old motorhome and never had a problem again. Thoughts?The Factory agrees, LDs built from 2008 on have relays.Larry
Re: Failed battery isolator Reply #8 – October 10, 2021, 09:54:09 pm Not wanting to find myself with the same situation Terry experienced, what part would you get to either have a duplicate diode isolator or relay for our 2003 LD? My packet of original LD supplied products shows they installed a Sure Power Indistries diode isolator 100 Amp. Suggestions?And any tips as to how to remove the old unit? Do you need to remove the brake master cylinder?Steve K
Re: Failed battery isolator Reply #9 – October 11, 2021, 03:08:25 pm Quote from: Larry W - October 10, 2021, 08:58:57 pmThe Factory agrees, LDs built from 2008 on have relays.Make that from August of 2007 on, our TK has the DC Power Contactor.Charles 1 Likes
Re: Failed battery isolator Reply #10 – October 11, 2021, 09:27:44 pm I changed out the isolator myself. You don’t have to do anything with the brake system.
Re: Failed battery isolator Reply #11 – October 12, 2021, 07:03:38 am Quote from: DaleM - October 11, 2021, 09:27:44 pmI changed out the isolator myself. You don’t have to do anything with the brake system.Dale, can you share what actual part you purchased and a source?Thank you,Steve K
Re: Failed battery isolator Reply #12 – October 12, 2021, 10:07:52 am The isolator is Sure Power model 1202, with 3 terminals on top. Amazon has it for $84.95. 1 Likes
Re: Failed battery isolator Reply #13 – October 12, 2021, 10:24:51 am possibly this one?Amazon.com: Rareelectrical NEW SURE POWER 2 BATTERY ISOLATOR COMPATIBLE WITH... As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
Re: Failed battery isolator Reply #15 – October 12, 2021, 07:22:47 pm Quote from: DaleM - October 12, 2021, 10:07:52 amThe isolator is Sure Power model 1202, with 3 terminals on top. Amazon has it for $84.95.That looks to be a diode isolator similar to what LD used to use and not a continuous duty solenoid like what they now use.Just be sure of what you want.Art
Re: Failed battery isolator Reply #16 – October 12, 2021, 07:27:52 pm Quote from: DaleM - October 12, 2021, 10:07:52 amThe isolator is Sure Power model 1202, with 3 terminals on top. Amazon has it for $84.95.Thanks for the detailed answer. Much appreciated.Art, what part would be similar to what the folks at LD currently installs?Steve K
Re: Failed battery isolator Reply #17 – October 12, 2021, 07:50:07 pm Sure Power Industries invented the Battery Isolator in 1959 and is now part of Eaton/Cooper Bussmann. The isolator listed is Sure Power model 1202 and is a diode type isolator as Steve explained. This type of isolator is inefficient and sheds significant heat when passing high current. These isolators also suffer voltage drop. Newer and more efficient isolators are now available such as the Victron Argo FET Isolators and DC Power Contactors such as the White-Rodgers (now discontinued) 586-903 Contactor installed in our 2007 LD. I do not know what LD now uses for this function. If I had a Sure Power Isolator and did not want to rewire its replacement I would go to a Victron Argo FET unit.https://allbatterysalesandservice.com/sure-power-multi-battery-isolator-120-amp-1-input-2-output-1202 http://allbatterysalesandservice.com/information/DataSheets/SurePower/Multi-Battery_Isolators.pdfEATON's Sure Power 1202 Multi Battery Isolator | WaytekArgo FET Battery Isolators - Victron EnergyAmazon.com : Victron Energy Argo FET Battery Isolators 100-2AC (2 Batteries...White-Rodgers - 586-903 - Contactor, Power; Single; 200 A (Continuous); 15...Charles 2 Likes As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
Re: Failed battery isolator Reply #18 – October 12, 2021, 10:19:25 pm Thank you Charles & Donna! That was the info and help I was hoping for.Steve K.
Re: Failed battery isolator Reply #19 – October 13, 2021, 10:53:39 am Steve, here is a photo of the solenoid LD currently installs. This is my setup in our 2021 RB. It connects both battery banks when the engine is running. I added the Trik-L-Start (TLS) later. It will send charging current to the engine battery if the house batteries are receiving a charge from the converter or solar panels when the engine is off. If the coach batteries are only discharging the TLS will disconnect. It has worked for me over the years. 2 Likes
Re: Failed battery isolator Reply #20 – October 13, 2021, 10:57:14 am Reading the numbers and searching, it look like this one:Emerson 586 108111 DC Power Solenoid, 15V - Hvac Controls - Amazon.comRich 1 Likes As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
Re: Failed battery isolator Reply #21 – October 13, 2021, 11:39:44 am Quote from: rich - October 13, 2021, 10:57:14 amReading the numbers and searching, it look like this one:Emerson 586 108111 DC Power Solenoid, 15V - Hvac Controls - Amazon.comRichThat is the same unit as the White-Rodgers 586-903 LD installed in our 2007 TK, Emerson just changed the part number.Updated - All you need to know....White-Rodgers 586-108111586 Series Spec Sheet586 Series InstructionsCharles 1 Likes As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
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