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| Battery charging [message #358940] |
Fri, 25 September 2020 14:06  |
NextGenGMC
Messages: 146
Registered: December 2017
Location: Washington State
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Just a small thought experiment here - what is a better way (more efficient and/or I suppose a faster way) to charge the house batteries when not connected to the grid - Onan generator or 455 main engine?
Onan generator is 6,000W. It feeds power into 110 house system, which is then connected to batteries through InteliPower battery charger/maintainer.
Main engine is 455 with what I believe a standard no frills alternator setup. Is there a way to poke the head into the engine compartment and figure out how many Amps the alternator is rated for?
Vadim Jitkov
'76 Glenbrook 26'
Pullman, WA
[Updated on: Fri, 25 September 2020 14:12] Report message to a moderator |
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| Re: [GMCnet] Battery charging [message #358944 is a reply to message #358942] |
Fri, 25 September 2020 15:38  |
NextGenGMC
Messages: 146
Registered: December 2017
Location: Washington State
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Didn't think about distance from source of electricity to the battery. In my case, the house batteries are in the back by the generator. This puts the alternator much further away than the charger/converter. I guess I'll try to find a datasheet on the charger to see what it can output. Is there some simple formula or rule of thumb for what the current/voltage drop is depending on wire length and size?
Vadim Jitkov
'76 Glenbrook 26'
Pullman, WA
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| Re: [GMCnet] Battery charging [message #358951 is a reply to message #358944] |
Fri, 25 September 2020 19:55 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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NextGenGMC wrote on Fri, 25 September 2020 16:38Didn't think about distance from source of electricity to the battery. In my case, the house batteries are in the back by the generator. This puts the alternator much further away than the charger/converter. I guess I'll try to find a datasheet on the charger to see what it can output. Is there some simple formula or rule of thumb for what the current/voltage drop is depending on wire length and size?
Vadim,
There are some know difficulties in charging the house bank aboard a TZE.
It is also well know to engine guys (like me) that nothing good happens in an idling engine. Given the build year of your coach, it most likely has an 80 amp alterator. This matters little as there is a single run of #10SAE (about a 0.9 #10AWG) wire to the rear and the loss in the ground path through the frame is also not insignificant. The data for line length voltage drop is very available, but most of it is junk as it calls out the loss in percent. Percent absolutely does not matter. What completely matters is the actual voltage drop in (milli)volts. The 400mV drop I had to deal with took my charging time from the converter from the two hours I had expected to over four hours.
If you have a Progressive Dynamics 9?XX the data you are looking for is on their website. What I could not find was the tables that they used to have with the graphics of lead/acid charging. PD 9 is the series, ? 1/2 is with or without the charge wizard built in, XX is the peak current rating. Unless you make very special considerations (I did), this peak will only matter for a small number of minutes. With a pair of GC2s back there, you will get about all you can hope for with PD9245 or if you have a 91xx. get the wizard pendant.
http://gmc.mybirdfeeder.net/GMCforum/index.php?t=tree&th=43774&goto=356071&rid=1184#msg_356071
If you digest the above and still have questions, that means I didn't explain everything that was important. I need to try again. As said, this was the result of some special testing with expensive instruments and time for me to set up. But when I did it about 10 years ago, it was all for me alone. I honestly thought that I was the only one with the problem.
As you have the house bank in the rear, you may well be able to make a good improvement by just running a pair of #8 AWG from your existing converter to the house bank directly with the fewest possible detours.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Battery charging [message #358956 is a reply to message #358940] |
Sat, 26 September 2020 02:04 |
NextGenGMC
Messages: 146
Registered: December 2017
Location: Washington State
Karma: -1
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Matt,
What you describe makes total sense. It looks like I'm sitting pretty here... I have PD9160A Charger/Converter with a Charge Wizard pendant. The unit is located pretty close to the house battery bank - in the mid-section of the coach above the driver side rear wheels. Logically, it seems that if we were to camp off the grid, then running Onan and manually putting Charge Wizard into Boost mode (if it doesn't do it on its own) would be the best option for a quick battery recharge. Just need to figure out what my power use balance is, i.e. how much power all lights and most importantly the furnace will draw and how long I can last on batteries only. I've changed all lights to LEDs, so the power draw from lights will not be significant. I need to test the furnace power draw to see how many amps it "eats" each time it kicks in. I may get a chance to do a test run for this soon. We are planning a weekend outing in couple weeks, where we will have access to shore power. I'm tempted to run on house power only for awhile to see how long it can last. Then we can test battery recharge rate with Onan and/or plug in to external power after that.
Thanks everyone for your input. Always much appreciated.
Vadim Jitkov
'76 Glenbrook 26'
Pullman, WA
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| Re: Battery charging [message #358958 is a reply to message #358940] |
Sat, 26 September 2020 07:29 |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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Matt,
I'm not sure what coaches had only a #10 wire running to the batteries in the rear. Was 23ft coaches with the batteries up front that had only #10 wire to the back?
My 77 Palm Beach, 26ft with the house batteries at the rear has a #0 gauge wire running from the front boost solenoid to the rear batteries. The wiring diagrams for the 75 and 77/78 show the #0 wire running back to the junction terminal behind the electric cabinet, then onward to the rear solenoid with #1 cable. Voltage drop during charging should approach 0V through those cables from either the engine or power converter/charger. I would expect his '76 to be similar.
My experience with deep cycle batteries is in public safety radio communications systems for emergency power backup. The chargers had a separate output to the battery so they could monitor the battery voltage and current. The charger could then tell the current state of charge for quickest recharge without overcharging. Our GMC's use a "loaded battery" system... the loads and the battery are connected together so the power converter has no idea how much current is being consumed by loads (lights etc) and how much is being used by the battery in recharging. So the converter either just goes through a set time in each stage or steps through the stages based on current flow, some of which was consumed by other loads. Not the ideal for quickest charge and longest battery life.
Our alternators are fairly dumb in comparison to the converters. The Delco service manual shows the schematic. Its basically a constant voltage regulator with a thermistor to sense operating temperature. As the alternator heats up, the thermistor would reduce the output voltage slightly. This would give a faster charge (higher voltage) after starting that would taper down a bit when the engine warms up. This works fine for a passenger car or light truck typically used for short commutes. I can't find any information on the output vs temperature of the regulator. Newer replacement regulators may have more smarts, but if they do they don't publish any info on it, so I doubt it. I just rebuilt my alternator using a Transpro regulator. I logged a 1 hour trip on my EBL and the voltage stayed withing +/- 0.1 volt the whole time, so I'm guessing it does not have a temperature sensor, or being cooler the alternator did not get that hot.
As far as how long your battery will last, with lead acid batteries that is a crap shoot. My experience with deep cycle batteries is since about 2010, most don't meet capacity specs right off the delivery truck (most now made off-shore). You mentioned using the furnace, so that means its cold out and your batteries will be cold, so their capacity drops significantly. Add to that the duty cycle of your furnace is going to vary widely depending on outside temperature. A few years ago I measured the current draw of my furnace and I believe it was about 8 Amps when on shore power.
So depending on your battery's age, quality of construction, state of charge, battery temperature and furnace draw and duty cycle, no one can give you a hard answer.. it is what it is.
One thing I noted was my furnace would run and there didn't seem to be much air flow out of it. I checked all the ducts and vents for obstructions and they are clear. I could hear the high limit switch click and the flame would shut down while the fan continued to run, they it would restart the flame. So obviously the chamber was hitting the high temperature limit. One cold rainy camping day, I took off the front cover of the furnace and WOW the blast of hot air was unbelievable. The coach was warmed in minutes and the duty cycle of the furnace dropped considerably. Finally a tasty warm coach in minutes. To this day the cover is off and we just open the door when we use the furnace.
Just my experience.
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
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| Re: Battery charging [message #358960 is a reply to message #358958] |
Sat, 26 September 2020 09:30 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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RF_Burns wrote on Sat, 26 September 2020 08:29Matt,
I'm not sure what coaches had only a #10 wire running to the batteries in the rear. Was 23ft coaches with the batteries up front that had only #10 wire to the back?
My 77 Palm Beach, 26ft with the house batteries at the rear has a #0 gauge wire running from the front boost solenoid to the rear batteries. The wiring diagrams for the 75 and 77/78 show the #0 wire running back to the junction terminal behind the electric cabinet, then onward to the rear solenoid with #1 cable. Voltage drop during charging should approach 0V through those cables from either the engine or power converter/charger. I would expect his '76 to be similar.
<snip>
Bruce,
I know my 73-23 is a #10 to the rear where the converter lives. As nearly as I can tell from the diagrams I have, this was the case with all the house bank in the front coaches made in at least 73&4. And, I got the gauge messed up on the later because the wire coming off the isolator is still listed as #10(SAE). So, later coaches with the #1 to the rear have some advantage at charging from the main engine alternator. But they will still have more loss than they could because the coach frame is not all that good a conductor. (My measured drop under load.) This is why I abandon my plan to upsize the single conductor for bank recovery on the APU.
My solution? I cheated. I put in a PD9260 at the passenger's right ankle and two stout cables to the house back about 3' of cable away. That cable is actually a cluster of #10 AWG that add to #7 because I couldn't bent the #6 I had the ways it needed to go. I had to run a new AC line to that corner of the coach to supply it. The 9260 was chosen because: A-It is an inch shorter and so encroaches on the copilots ankle less and B- I got a deal.
Hope you are well and we can open the border before too long.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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