The coach has an echo battery tender that doesn't seem to keep up. For some reason the batteries aren't staying up. Today we took the negative cable off the engine battery and connected a DVM between it and the the negative post. With the key off it was drawing what showed to be 16.2 amps. I don't know how it didn't pop the fuse in my meter. What could be drawing that much with the key off? Or ami reading/using my meter wrong?
Possible alternator or isolator
No, μ, the letter Mu; stands for "micro" or "one millionth". It's Greek.
Pierce
Thanks Pierce, I see the giant orange capital A two clicks over now. 🤯 I was using a different one earlier today at the house on my Jeep because it decided it wants to do the same thing. It sparked pretty good when I touched the lead to it. I'll go back tomorrow and check it again properly.
There went all my credibility. I thought it was strange it was exceeding the maximum of 10a without any pops or smoke.
Cheap learning experience. You rally don't want to know how much the quick blow fuse in a Fluke multimeter costs.
If your battery tender doesn't keep up, it's because the internal leakage in the battery is too high. Disconnect the ground terminal from the battery and check again after 24 hours.
Expanded:
Lead acid battery voltage measurements are only valid after 3 hours of rest due to the sluggishness of the battery chemistry. So disconnect the negative cable to isolate your battery from the load, wait 3 hours and measure the voltage. Wait 24 hours and measure the voltage again. If the battery resting voltage has changed for the worse buy a new battery. If not buy a new RV. Or find out where the electricity is going.
Thank you. I didn't think to check the voltage yesterday when I disconnected it. I did exactly that on my Jeep yesterday. I did stop by this morning and check the draw with the DVM on the correct setting and I got .173A and the voltage is at 12.24. I'll check again tomorrow. How much draw is acceptable with the key off?
Draw can be from alarm system, radio memory, keyless entry, etc. so it varies with individual vehicles.
One amp = 1000 milliamps. You have 173 milliamps. This sounds like double what is considered high if your reading is accurate. I do not know what you are powering. You might check your owners manual for the vehicle. I remember having one vehicle., manual said to turn off keyless entry if parked more than two weeks. No easy answer to your question. I hope this helps.
"A normal amount of parasitic draw for newer cars is between 50-milliamp to 85-milliamp current draw. A normal amount of parasitic draw for older cars is a reading less than 50-milliamp. Anything past these amounts indicates an electrical issue and should be addressed by a mechanic."
Thanks Jack it does help, I had it on the big orange capital A this time. I held the leads on there close to a minute I'd say to see if it would go lower. When I do it on my Jeep it will be at 1-200 milliamps then within a few seconds it will drop off to about 30 or maybe less even. I will start looking for something that's drawing that shouldn't be. Does the ecm draw all of the time?
The ECM generally gets power from the ignition switch being activated.
My solution to your same issue was to put in a new AGM, Odyssey battery. Afterwards I installed a battery cutoff to totally protect my new battery.
So maybe look at the Odyssey, or something like the best AGM battery from Napa, Oriellys, Interstate, or Autozone. They will run approx $200.
https://www.autozone.com/ignition-tune-up-and-routine-maintenance/battery
Yes, Both engine and transmission memory in the ECM use power unless you unhook the batteries
Mike
The electric system for the engine is not optimized for a AGM. The float voltage is as I understand it is different for a a flooded cell versus an AGM.
Probably why the oem alternator had and adjustable voltage that Wolfe has mentioned adjusting to be at 13.6 volts float.
RSL(run, start, lighting) batteries are normally higher voltage than agm's.
Bmw's come with AGM batteries. The float voltage as I understand it is set lower than flooded cells used in other cars.
Running higher voltage into agm's may be overcharging them over the long run.
This info came from my Lexus boards as to why Lexus did not equip my 12 year old model with an AGM versus a sealed VRLA battery.
Like I posted this maybe why the adjustable voltage alternator was being used?
Food for thought
My 96 U320 has the engine and transmission connected directly to the battery. Disconnecting the Neg cable from coach's chassis ground will not disconnect the control modules if they are connected directly to the positive negative battery terminals.
I put a cutoff switch on the negative battery cable.
With it on off, nothing passes from the batteries.
I did this when I replaced my batteris with Exide AGM grp 34 Edge batteries. I am very happy with these. Exide changed the name now to Exise Max.
I added a short, stiff, extension cable and the following switch, which did not require a mounting bracket. The Blue Sea switch has 1/2 inch studs and is rated for 600 amps since the starter could posibly draw over 400 amps.
Amazon.com : Battery Switch HD ON/Off : Boating Battery Switches : Sports &... (https://www.amazon.com/dp/B000MMDLB6/ref=cm_sw_r_em_apa_i_qyG1EbNZVJADH)
That's what my brother is telling me to do. I like the idea of it. I would have to run a longer cable and do away with one of the grounds. MOT put another one on there trying to help the starter out. You have to get up underneath the coach to get to the batteries. It's not very convenient. At the same time I feel like the batteries shouldn't drain that fast. Also, we've got the red top optimas which are agm also. Have been in there about two years now I think.
DJ and Jane wrote: "...... the draw with the DVM on the correct setting and I got .173A and the voltage is at 12.24."
010 You could install a suitably rated master control relay with a toggle switch and a red guard.
Let's do the math. With labels.
.173A(1 Hour) = .173 Amp Hour.
A BCI Group 31 battery holds about 100 amp hours. If we set a lower limit of 50 amp hours then
50 amp hours divided by .173 amp hour = 289 hours after you cancel out the amp labels.
Since I'm feeling snarky this morning, although the coffee is nearly ready, 289 hours divided by the 24 hours in a standard* day gives us 12 days.
GOTO 010
* Listening to scientists, especially astronomers can really mess up your mind, from, the earth's got the jitters, to the earth moved in relationship to the sun and the stars while spinning about its axis.
Running a start battery down at all unless designed to be deep cycle will quickly damage it.
Hence the industry wide use of auto combiners for battery banks
I have found no other way to 100% reliably charge the engine batteries.
Had 2 different chassis batteries chargers fail. Two sets of batteries killed dead
Agree, battery combiners are one option.
So are low amp, stand alone 120 VAC smart chargers dedicated to the chassis battery bank. Yes, only if you have 120 VAC where you store the coach.
Either option will keep them charged.
As I said I had 2 dedicated 110 volt chargers fail. One was a trickl charger. Green light on. No output.
Too expensive if you are using nice batteries
I actually did end up putting a 110v battery tender on there and it was keeping up pretty well. But no power where it's at.
I'm gonna run over today and see what the voltage is down to. The more the wheels turn in my head, where it doesn't have power the cutoff would be best
If you have the ability to keep the battery charged (120 VAC, solar, etc) that IS preferable to disconnecting them.
The transmission and engine computers prefer to have their memory lead (notice TWO fuses to Allison ECU-- the 5 amp one for memory) stay hot.
I thought of a solar panel too. I would like to keep them up.
I checked the voltage on the engine batteries. They're at 12.20v. Yesterday when I disconnected them they were at 12.24.
Those readings show a 50% discharged battery (assuming they are on good condition.
Time to recharge!
Worse case, use the boost switch and shore power or generator to power the inverter/charger.
Thanks Brett. It seems like they always are at about 12.2-12.5 or somewhere around there. Usually below 13v. Except when I put the 110v battery tender on it.
12.8 is a fully charged battery at rest.
50% discharge is damaging them. External solar panel? Or remove the batteries?
I don't have a solar panel. I'll look into one tonight. I wouldn't think one to maintain the batteries in a situation like this would be overly expensive.
Just curious. What would the voltage be at 50 percent discharge?
12.2 VDC is the commonly accepted 50% SOC.
Removing the batteries this time of year will just keep the discharge process going. Rather than me giving a clumsy explanation, read the page here: Battery Basics - Progressive Dynamics (https://www.progressivedyn.com/service/battery-basics/)
Pierce
I hooked my truck up to it yesterday because it was at 11.1v. I need to get these voltages all squared away and clean all my connections. Then move on to why it doesn't want to start very good.
I really appreciate and value everyone's input on here. We couldn't afford to own one if we had to take it to a shop every time something needed fixed.
If the voltage keep going down with the battery disconnected, you have an internal short* that is only going to get worse. When you choose to replace the battery depends on you pain tolerance. I met a person on this list who tried to get by with too little battery. He learned just how expensive the starter motor can be to purchase.
*In my personal experience, the lead sponge that makes up the active material in a lead acid battery slowly sifts down to the bottom of the battery cell where it piles up until it touches the bottom of one or more plate. AGM and Gel constructions delay this action.
FWIW I use Battery University as my main on-line source for battery facts and figures. More reliable than my memory.
Same here. I think smart phones have made it worse. I will check out battery university. We've got all AGM's.
Asked my guru buddy today what 50% discharged would be on gels. 12.4. Which equates to 12.2 for agm's.
The reason that a gel battery at 50% discharge reads 12.4 rather than 12.2 (the accepted 50% discharge voltage) is because the internal resistance of a gel battery is lower than the internal resistance of a flooded battery. The fully charged voltage of a gel is also higher than the fully charged voltage of a flooded battery, such that the voltage drop to 50% discharged is circa 0.5 volts for any battery.
On a side note: using a battery desulfator also raises the fully charged and 50% discharged voltages. The previous gel batteries I had actually reached 13.1 volts when fully charged. I have not measured the fully charged voltage of the AGM batteries I currently have.
My Guru buddy yesterday mentioned the resting 13.1 volts for mk gels as well as the 12.4 volts at 50% discharged.
Thank you for the input. I built up three precision test/load bank setups to test all my 7 year old gels at once just for time constraints.
Have not finalized the amount of load I will use as each device is adjustable from zero to 20amps.
Separately powered. Not off the batteries themselves.
Any input Wyatt? You would like the setups. May lend them out after testing
Bob, I look forward to your test results. On the following two links from my Dropbox, at the bottom of the screen that pops up, click on continue to wesite.
Found this info from Deca on capacity testing their Gel 8D and record keeping of testing.
https://www.dropbox.com/s/9xmd9hsmzf6o683/8A-8G-IO-Manual-1833%20%281%29.pdf?dl=0
Gel tech manual from East Penn.
https://www.dropbox.com/s/so0pah5514crtug/0139%20%286%29.pdf?dl=0
From MK.
https://youtu.be/vCRDWN_6K8U
From beamalarm.
Load Testing Gell Cell and AGM Batteries (http://beamalarm.com/Documents/load_testing_gell_cell_and_agm_batteries.html)
An interesting read from some others that did capacity testing on their 8D.
Lifeline Batteries: Long Term Review and Capacity Test | Expedition Portal (https://expeditionportal.com/forum/threads/lifeline-batteries-long-term-review-and-capacity-test.198873/)
Some history on MK built by East Penn.
MK Battery Celebrates 30 Years of Business - East Penn Manufacturing (https://www.eastpennmanufacturing.com/mk-battery-celebrates-30-years-business/)
Great machine. Can print reports or go to usb. $1070.
My guru buddy yesterday mentioned I was the only rv'er who had ever asked him these type of questions.
Which is a good thing. I think
Especially if you might REALLY. need the coach to work correctly.
I have 3 of these.
12V Electronic Load Battery Capacity Tester Module 0-20A 250W Intelligent... (https://www.amazon.com/Electronic-Capacity-Intelligent-Constant-Discharge/dp/B07XY6X79B)
And three of these
Powerwerx Watt Meter, DC Inline Power Analyzer, 45A Continuous, 12 Gauge,... (https://powerwerx.com/watt-meter-analyzer-inline-dc-powerpole)
And a bunch of Anderson powerpole cables to connect them
And three 12 volt separate power supplies to power the testers
A little update:
Last week I got around to getting the batteries out and brought them home to put a charger on them to run some tests to see how the voltage held up. I had one that didn't seem to want to hold a charge so I took them to O'reillys to get them tested. Out of the three one was bad according to their machine. Another one said that it had 25% life left. The guy didn't seem like he knew what that meant. I didn't get a chance to see what the other was said. They ended up replacing the one that was bad. This morning, I went to the coach to put them in. First I removed all of the cables and cleaned all of the connections including on the starter. I found some conductive grease at Lowes with zinc and added it to the connections before I reconnected them. I hope that will help. Just before I went to put the batteries up in the rack I thought I should check them quick. the new one read 12.6v and the old ones read 12.53v and 11.74v. Both of them had been on the charger within the last two days. I took the 11.74v one with me to get retested. now that I think of it I may go back in the morning and check the other old one to be sure.
If it were me, I'd change all 3.
Only a set.
You say "they ended up replacing", was it under warranty? Good advice from others to replace all three. Being on charger two days, does not mean they are fully charged. It depends on charge amps, voltage, and battery charge profile. Good agm batteries, when fully charged, will test at rest, and not combined, 12.8 volts or above. That is from the maker of the grey cased, black top AGMs, that East Penn make.
It was under warranty. I replaced them all at the same time. I'm going off of my battery tender with a solid green light which is supposed to mean fully charged.
I had a trickl Charger green light on that put out no power,
Thanks Bob, This one's working. I make sure to check it. It's been putting out like 13.6v. It got the other one up to 12.5v. The more I think about it the one in the coach is probably working right but the house batteries go below 13v for so long before the gen kicks on it isn't keeping the engine batteries up. The one in the coach stops charging the engine batteries below 13v and it won't charge if there's over 2v difference between them. I'm going to go get the other battery, check it and take it to get it tested again with the other one.
Alright, I got them both tested one was bad. I hoped the other one was but two places couldn't kill it for me. I had a professional That could read/use the DVM properly come over and help me reinstall the batteries and check my voltages all came out good. I turned the boost on just because. The engine turned over and fired right up like it had been running all day.
Also one of the lugs or whatever it's called had a big cut in it when I was cleaning them the other day. I replaced it. I'm not sure where it goes because the label was gone.
Peel the cover back to ensure it's not green and crappy inside.
Thanks. It was clean. I replaced it.
I recognize that cut. That's what's left after you saw through the nut and bolt flush with the washer/lug to free the cables from captivity.
Well that explains that.
I started it up yesterday and this morning with the boost on. Fired up really good. This afternoon I caved and bought another battery to go with my two new ones so I've got a whole set of new ones. It just so happens that the battery in the Jeep is out of warranty and keeps dying on me also. So I'll take the "good" old one and put it in there. I had the negative secured out of the way and it became unsecured and made contact with the battery post draining the battery on our way back from outlet recent trip to NH.
This evening after I installed the 3rd new battery In the coach I Figured I would try to start it again. This time without the boost because I feel like it should be able to start easily without the boost. It turned over almost as fast as it did earlier with the boost on. So I'm very happy with that.
I'm still watching the voltage to see if it's going to drain. I didn't check to see what kind of draw it had though. I may do that next week.