Hello all,
I had a couple questions about the charging system and the chassis batteries. Firstly, my coach originally came with 3 batteries of some sort (rumored to be optima yellow top group 34). Right now, the previous owner made the incredibly silly decision to remove all of that and install one 4D battery. As you'd expect, the engine will not crank without boost.
During my research to remedy the situation (new batteries, terminals, cables and a hydraulic crimper), it occurred to me that the Optima yellow top AGM require a different charging profile (more like regular flooded) than the GEL house batteries. Yet the alternator is connected to both banks.
So my question is, is the voltage regulator a lower voltage setup for Gel batteries and in effect does not properly charge the AGM chassis batteries or is it standard and overcharges the GEL batteries?
The voltage is typically set up for the AGM chassis batteries, and the longer run combined with the diode drop at the isolator, drops it about the right amount for the Gel house batteries. Or at least, I believe that was the intention and it fits what I know about the setup. For most coaches retaining the OEM setup, it seems to have worked pretty well over the years. Someone can correct me if they know better...
Don
Actually, the alternator/regulator are NOT smart-- they do not have multi-stage charging protocol or allow different charge algorithms for different battery technologies.
The sense wire is on the chassis battery, but there is the same voltage drop across the battery isolator diodes for both banks. Said another way, they both receive very close to the same voltage, particularly as they reach full charge.
My coach has gel batteries for the house ( 8D's- for long deep cycling) and 2 AGM for chassis ( starting batteries). The chassis batteries are not deep cycle as they need to give a lot of cold cranking amps to start the big engine. When my chassis batteries needed replacing I went with Duralast Platinum AGM's- each with 750 cold cranking amps which starts my ICS350 just fine. I find that running my Cummins with the stock voltage regulator charges my chassis batteries fine and my house gels get charged as well.
You probably need 3 starting batteries to start your bigger engine Mark as was your original set up. After you get your chassis batteries set up again, you will be able to see how they hold a charge and also monitor/test your house gel batteries.
Best of luck.
The Optima gel batteries are put in automobiles and are sold at Costco. My son works for the Auto Club of Southern California and says they last about 7 to 10 years. The alternator on the cars don't know what they are charging so the gels must be able to hold up to the 14.2 that most cars charge at.
Mark, I needed new start batteries on our 2001 U320 a few years back.. The originals were 11 years old. I checked with James T and he suggested sticking with the original Optima Yellow Tops to provide the longer term deep discharge that all parasitic loads place on the start batteries. The LP gas detector, the CO detector, the smoke detector and many more items put a continuous drain on the start battery. Made sense to me. Three of these in good condition with the wiring in good shape starts the M11 with no boost needed. If we are stopped and land line connected then a smart BatteyMinder keeps them fully charged.
Best price at the time was at Amazon with free shipping and a $25 rebate from Optima.
I stand corrected about the diode voltage drop, of course it affects both banks the same. Still the run to the house batteries is quite a bit longer on our coach. I haven't done any calculations for voltage drop, but I believe it to be significant. I am not sure how much difference in length of each respective run, but the chassis battery (1 8D AGM) is a lot closer to the isolator than the house batteries which are also AGM 8Ds (4 of them). I would estimate the the difference is close to 10'. In any case the isolator is bypassed right now so the alternator only charges the house batteries if the boost switch is on. Fortunately, the solar keeps them up pretty well on its own. On my project list to address the isolator issue with something else than a diode based isolator altogether. When ours failed, there were several failures that happened right then or in close succession. When it failed, it was putting out 17 volts according to my Seelevel, which then smoked and died...
Don
Don,
I replaced my isolator with a Sterling Zero Voltage Drop isolator, three battery banks, 250 amp. Engine, house, refrigerator batteries.
Sterling ProSplit-R – Zero Voltage Drop Battery Isolator (http://baymarinesupply.com/store/electrical/wiring/isolators/sterling-prosplit-isolator.html)
They also make a smart alternator regulator that charges batteries in 4 step progressive charge, faster and to a higher level of full charge. Still thinking about this one.
Sterling ProReg-D Advanced Alternator Regulator (http://baymarinesupply.com/store/electrical/chargers-inverters/sterling/sterling-proreg-d-alternator-regulator.html)
And a smart Alternator to Battery charger that for two battery banks eliminates the isolator. Thinking about this one too.
Sterling Alternator-to-Battery Charger / 12 Volt - 210 Amp (http://baymarinesupply.com/store/electrical/chargers-inverters/sterling/sterling-alt-to-battery-charger-210-amp.html)
And these get a Forum member discount from Alan at Bay Marine Supply.
Don,
Yes, you are exactly correct. As I posted in the last sentence of my post: " Said another way, they both receive very close to the same voltage, particularly as they reach full charge."
If carrying a lot of amps (batteries deeply discharged), there will be a voltage drop on the long run to the house bank. But, as amps drop, so does voltage drop. So, after an hour or so (if house bank deeply discharged), you should see the same voltage at both banks.
Just a quick, curious question: when we had our start batteries replaced, the recommendation was Optima Red Tops. I've looked on their website, to read about the differences — but probably didn't grasp all I was reading. Ours seem to be serving us well. Good? Bad? OK but . . . ?
The Optima Red Tops have an initial start push that is higher than the Yellow Tops. Either should be fine. Many others are selecting other brands. If you are boondocking for some time and aren't charging the start batteries with solar for example, then the Yellow Tops might have an advantage. If you are usually plugged in and have a charger on your start batteries then Red Tops are fine. Someone told me that FOT was having a hard time getting Red Tops in 2001 and that is why they were using Yellow Tops. Most likely Urban Legend.
The Optima red tops are superior to the yellow tops for starting purposes. Unless one has a true deep-cycle application there is no reason to go with the yellow tops.
And our 2003 came with Blue Tops.....
There is some good discussion of start battery brands here on the forum. IIRC Jim McNeece is one of the folks who posted some good stuff.
Optima is recommending Blue Tops for Marine and Motorhome applications where there are higher deep cycle loads. Yellow Tops are somewhere between the Red Tops and Blue Tops. Almost the same starting specs as the Red Tops, more deep cycle capability. Red Tops are not recommended or warranted for use in deep cycle applications according to Optima.
DWMYH
Lead-Acid Battery | OPTIMA® AGM Batteries | OPTIMABATTERIES (http://www.optimabatteries.com/en-us/products)
Read it for yourself.
All of the Red Top batteries on their web side have black cases and there is a Blue Top with a black case.
That's not accurate. Optima says blue tops are dual-purpose just like yellow tops. The terminals are different but the interior construction is the same. Optima says the case color shows the application: A dark gray case is a starting battery while a light gray case is a dual-purpose battery.
To me, at least, it doesn't make sense to use a dual-purpose battery, which by definition is a compromise, in a starting application for a large diesel engine.
Interesting. Sounds to me like if you leave on a very long drive (say 12 hours with no main engine shutdown) day with fully charged house batteries, they could get cooked a bit. I don't recall what the voltage settles at but I think it was 13.8-14.0v which is too high to float a gel battery at.
Guessing we're OK (but are we?) since the previous owner installed a — forgive lack of what is probably the proper vocabulary — a voltage-sensitive "bridge" between the house batteries and the start batteries. In theory, if the start batteries fall below a certain voltage, the "bridge" opens and the house batteries will charge the start batteries (until the voltage in the house batteries drops to a certain point).
Richard,
Yes, a smart battery combiner is a fine way (one of several) to keep chassis battery charged with power coming from the house bank when it is over a pre-set voltage.
I don't think the batteries, coach or house, ever get fully charged by the alternator especially after the voltage drop cross the isolator. The voltage coming out of the alternator and its (not smart) voltage regulator is probably set low to protect the batteries. Batteries might get up to 75% or so. All of this seems to be a bit not fully defined to me.
The Red Tops are a common choice. They are designed to provide very high power output over a short time. The others have more capacity to act as a start battery and also provide a lower power output over a long(er) time.
Actually with the external sense alternator Foretravel fit (voltage sensed on chassis battery side of diode-based battery isolator, batteries do see the full 14 VDC. The alternator just has to put out about .7 more (that is turned into heat in the diode-based isolator).
And, 14 VDC, particularly if driving for a couple of hours should get you to full charge.
Roger, what engine batteries do you have?
Thanks for your time.
Jeff
3 Yellow Top Optimas, D31T, new in 2012.
That is sort of what I thought but not what I am seeing on my coach. The voltage coming out of the alternator at high idle set with cc with some loads on is low to mid 13's. By what Brett says I should be seeing closer to high 14's. Some adjustment required.
The Optima Website lists the max CCA for any Red Top at 800 amps and the max MCA for any Red Top at 1000 amp
The website lists the D31T CCA at 900 and the MCA at 1125.
The website lists the D 31M CCA at 900 and the MCA at 1125.
Am I reading this wrong? Aren't these the measures for starting capacity?
Like I said earlier, and I will include the entire sentence here, "The others have more capacity to act as a start battery and also provide a lower power output over a long(er) time"
The other Optima batteries (yellow tops or blue tops with a light-gray case do
not have "more capacity to act as a start battery" when compared with the Optima red top batteries. The red top Optimas provide superior starting capacity. The light-gray-case Optima batteries are a compromise and according to Optima's website provide less starting power than do the Optima red tops.
Where is the voltage sensing for the alternator attached in your particular system?
The alternator sense wire can be on the chassis battery itself, chassis battery terminal of the diode-based battery isolator or really any place with a good large-gauge connection to the chassis battery. If in doubt, remove the old one and put in a new one.
And, easy to diagnose: With engine at fast idle (around 1000 RPM), check voltage at the diode-based battery isolator. Should be around 14 at the two outer posts (one to chassis battery, one to house battery). Center lug from B+ terminal of the alternator should read about .7 VDC higher.
Note, it is common for voltage readings at the dash to be a little lower, particularly with high loads up front. It is really voltage at the batteries that counts!
Thanks, Brett. I do have a new 10ga sense wire from the sense terminal to the alternator and have measured in both places you suggest.
I have yellow top chassis batteries and MK gel house batteries. They seem to work well together. At one time I had red top chassis and the resting voltage after charging was a bit different, but with the yellow tops it's almost the same.
Both the Optima red top and yellow top batteries are AGM technology and so the fully-charged resting voltage should be the same. The details of the spiral plate design are different but the chemistry is the same.
I wonder then if you potentially have a failing regulator that just can't deliver the requested voltage. Or perhaps your regulator was replaced with one that delivers lower voltage. There are regulators with lower voltage setpoints, adjustable regulators, 3 stage, etc so unless you are sure you have OE there might not be a "problem" exactly.
Wow what a technical discusion. You guys are way over my head. My 95 has three red tops which are old not sure of age. When in storage and plugged in I have a battery tender hooked up. When ready to travel they fire that cat engine and away we go. When its time to replace I will again use red tops.
Joe that's the ownership experience I didn't sign up for when I bought my coach from a Sleezy dealer ;)
Yup Mark you are correct and even if you didn't buy from a sleezy dealer, the help that you get from this forum cannot be bought anywhere.
Mark, it is the original LN alternator. It does work but the voltage seems low. There is a voltage adjustment that I have to try. That is next. It has probably worked this way since we got the coach. Who knows what was done earlier.
Joe, a smart battery tender type charger is good for the start batteries. Just sitting there, plugged in to a land line or not, even with the salesman switch off (turns off the house batteries) the start batteries see a small but constant load. A smart solar charger or smart battery minder at 1-2 amps per battery is good,
Roger,
Look at the alternator drive belt. If it is old, hard or glazed it is slipping under load (the reason it's glazed) and that will effect alternator output.
JD
Thanks, John. The belt is new and properly tightened. At some point the alternator voltage adjustment screw must have been backed off a bit by the previous owner. I am going to try turning that up a bit if I can.
Voltage Regulator Adjustment (http://www.beamalarm.com/Documents/voltage_regulator_adjustment.html)
Roger:
I read the Leece-Neville adjustment procedure. Does your alternator have a sense wire connection? If you do, I think the better place to measure the voltage for adjustment would be at the point where the sense wire is connected (typically at the chassis battery post on the isolator, or directly at the chassis battery), to account for any voltage drops between the alternator and battery.
That makes sense. I do have a new sense wire from my Sterling zero voltage drop isolator to the alternator. Voltage coming out of the alternator is low 13's last time I measured it.
Not the best time of the year to be out fussing with this stuff although this might be a very short winter. Or not.