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No chassis power?
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Jon wrote: “I have a hard time thinking you could have 14V on the 12V side and zero on the 24.” I agree with Jon. You need to isolate the problem before you buy new batteries; unless batteries are really the problem.
Back to your Guest/Marinco charger … if I understand what you said, you’re thinking that whatever phantom draw you have on the batteries is MORE THAN what the charger can replace hence the batteries are being completely drained to zero over time because the charger doesn’t put out enough juice to overcome the phantom draw. That seems like an awfully HIGH phantom draw. Its almost as if some high wattage lights that are tied to the chassis batteries are being left on and you don’t realize it or can’t see it.
Is the charger wired directly to the chassis batteries? If so, flip the 12 volt and 24 volt masters off and see if the charge comes up in the batteries. That way if the phantom load is beyond those masters the phantom load won’t be draining the batteries and stealing juice from the charger. If the batteries come back, then you know the phantom load is between those two cut-outs and batteries; probably something a previous owner wired direct to the batteries that should make it easier to find.
Added: If you have a phantom load larger than your charger’s output, you will NEVER, EVER charge the batteries or even maintain a charge. The math just won’t work.
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Look for a dirty 24v positive battery cable at the battery or chassis. You have 12 volts cause the connections to that point are good. Check the cables.
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Dick, not sure if I have a phantom draw, since I have never had an issue with the charging of the chassis batteries, I find it hard to believe that it would come up out of nowhere. But this is a prevost, so nothing is off the table 😉
Will check on the volts on the battery posts and jumper posts, but I will also check the cables to make sure they are good/clean before I pull anything and get new batteries.
Hope it’s an easy fix, not really near anyone convenient to come out and check on it. Kind of in the middle of Jacksonville and Clearwater and really far from ETLC. Haven’t come across any other service companies that know Prevost chassis in the Ocala/Gainsville area.
Jeff and Lindsay
91 Marathon XL -
The equalizer is seeing the exact battery voltages and is easy to access and there is no chance to misinterpret voltages.
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Correct Dick,
I forgot to add to my description that after turning off the engine I turned the switches off to let the charger do its work. Also your thought of a Phantom load greater than the charger can keep up with seems excessive. I Know I have something going on because if i let the charger do its thing to float with the switches off the batteries come up. Then the red charge light comes on immediately when I turn the switches on. My main reason for posting was to let Charles know that the charger could show float if the batteries are completely dead. That seemed to be throwing him off. I may have gotten too deep in the weeds with the other info. Jeff
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So I have two vanner compents.
60-100D Voltmaster. Has three posts on it. Ground, 12V and 24V. I am assuming I can put a lead on the 24v post and a lead on the ground post and should read 24v on my meter. Same for the 12v side.
THe other is a EM70D Electrical Monitor. Has 7 leads on it.
24v ignition SW
Monitor Input: Ground, 12v, 24v
Lamp Output
Batt Low, Batt High, Batt Balance.
How best to test the monitor component? I assume this is what feeds the BAL light on the dash, which has come on every once in a while in the past, but goes away after running the coach for a little while. Doesn’t happen all the time and doesn’t seem to matter how long it’s been since I ran the coach last.
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Check the voltage at the Equalizer. The 24v terminal should be twice the 12v within a 1/2 volt.
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Charles,
The starting point for you issue is to get voltages.
If you do have zero on the 24 V side the next step if it were me would be to separate the batteries after they have gone to float and load test each one individually.
Your phantom load(s) could actually be a battery gone bad, and one bad one has the potential to suck the others down.
If you cannot get all 4 into float with the charger and the master switch off it is likely a battery issue. If the batteries charge and test OK then the issue is downstream from them and you are going to have to just follow the circuits until you find the offender that is robbing them of power.
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Checked batteries
From outside to inside.
Batteries
1 10.66 v
2 13.25 v
3 13.25 v
4 10.66 v (this is the forward battery)
This is with all batteries hooked up.
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If all the batteries are hooked up the voltages are not valid.
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More data… there are in line fuses from batteries to chargers. One was blown. Replaced and now getting dash action when I turn key. But batteries are low. So Will keep on charger and see where they go.
Of course I go in for Hernia surgery Friday so final trouble shooting may need to wait a while. Ah the joys of lifting heavy thinks over a lifetime because im too impatient and independent to wait or ask for help.
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Jon, I think the 12v batteries are correct (13.25v), while the 24v batteries are drained some due to the blown fuse on the charger. When I check the vanner posts, it show you 13.25v on the 12v post, and 10.33v on the 24v post.
Not sure why the ready light was showing, but with a new fuse, the charging light is on.
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also, not knowing how long the fuse has been blown, I have been using my load lights for lighting and door light over the past month. So that could be the “phantom” drain that has been brought up. If it was something more then that, I would suspect the batteries would be much more drained then down to 10.xV.
Still questioning why the charger “Ready” light was green. I would suspect that both the green and red lights would have been out on that side of the charger.
Will check the charge tomorrow and Friday morning and if it gets to an expected level, will run the coach and let it run for a while. Hopefully this is the issue as I don’t have time to go beyond my diagnosis after Friday morning, for a while.
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The chassis batteries are wired two in parallel and then in series with the other pair to produce 24V. Based on your measurements one of the parallel pairs is at 10.66V, the other is fine. The Vanner equalizer should have kept both pairs close but the charger only charging the lower pair probably confused it.
With the fuse replaced, check the voltage the charger is putting on the low voltage pair. Depending on the amps the charger is capable of putting out, it may take a few hours for the voltage to come up.
In any case, your charger is not very smart. A blown fuse should not produce a green light. It obviously only looks at voltage and not if any current actually flows into the battery.
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After replacing the fuse, the 24v post on the equilizer measure at 25.6, while the 12v measured at 13.66. Basically where I would expect it to measure. Charger still needs to charge two batteries, then I will check everything before starting it. Batteries where swapped out in June 2014 per my label put on the batteries. So hopefully they should take a charge as they are not that old and where not 100% drained.
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