Chassis Batteries

Topic: Chassis Batteries (Read 1547 times) previous topic - next topic

Chassis Batteries

December 21, 2015, 09:19:15 pm

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?

Re: Chassis Batteries

Reply #1 – December 21, 2015, 09:43:54 pm

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

Re: Chassis Batteries

Reply #2 – December 21, 2015, 09:51:08 pm

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.

Re: Chassis Batteries

Reply #3 – December 21, 2015, 09:58:43 pm

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.

Re: Chassis Batteries

Reply #4 – December 21, 2015, 10:36:57 pm

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.

Re: Chassis Batteries

Reply #5 – December 21, 2015, 10:43:41 pm

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.

Re: Chassis Batteries

Reply #6 – December 21, 2015, 10:45:56 pm

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

Quote from: wolfe10 – December 21, 2015, 09:51:08 pm

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.

Re: Chassis Batteries

Reply #7 – December 21, 2015, 11:00:55 pm

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

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

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
And these get a Forum member discount from Alan at Bay Marine Supply.

Re: Chassis Batteries

Reply #8 – December 22, 2015, 08:15:30 am

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.

Re: Chassis Batteries

Reply #9 – December 22, 2015, 09:18:17 am

Quote from: Roger & Susan in Home2 – December 21, 2015, 10:43:41 pm

I needed new start batteries on our 2001 U320 a few years back. I checked with James T and he suggested sticking with the original Optima Yellow Tops

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 . . . ?

Re: Chassis Batteries

Reply #10 – December 22, 2015, 09:25:55 am

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.

Re: Chassis Batteries

Reply #11 – December 22, 2015, 09:33:14 am

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.

Re: Chassis Batteries

Reply #12 – December 22, 2015, 09:55:39 am

Quote from: Roger & Susan in Home2 – December 22, 2015, 09:25:55 am

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.

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.

Re: Chassis Batteries

Reply #13 – December 22, 2015, 12:04:09 pm

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

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.

Re: Chassis Batteries

Reply #14 – December 22, 2015, 12:39:14 pm

Quote from: Roger & Susan in Home2 – December 22, 2015, 12:04:09 pm

Yellow Tops are somewhere between the Red Tops and Blue Tops. Almost the same starting specs as the Red Tops, more deep cycle capability.

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.

Re: Chassis Batteries

Reply #15 – December 22, 2015, 02:45:47 pm

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.

Re: Chassis Batteries

Reply #16 – December 22, 2015, 02:49:43 pm

Quote from: Roger & Susan in Home2 – December 22, 2015, 12:04:09 pm

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 . . . Red Tops are not recommended or warranted for use in deep cycle applications according to Optima.

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).

Re: Chassis Batteries

Reply #17 – December 22, 2015, 03:12:34 pm

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.

Re: Chassis Batteries

Reply #18 – December 22, 2015, 04:21:56 pm

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.

Re: Chassis Batteries

Reply #19 – December 22, 2015, 04:24:32 pm

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.

Re: Chassis Batteries

Reply #20 – December 22, 2015, 04:30:16 pm

Roger, what engine batteries do you have?

Thanks for your time.

Jeff

Re: Chassis Batteries

Reply #21 – December 22, 2015, 04:31:26 pm

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"

Re: Chassis Batteries

Reply #22 – December 22, 2015, 04:35:00 pm

Quote from: Roger & Susan in Home2 – December 22, 2015, 04:21:56 pm

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.

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.

Re: Chassis Batteries

Reply #23 – December 22, 2015, 04:36:53 pm

Quote from: Roger & Susan in Home2 – December 22, 2015, 04:31:26 pm

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 about 1500 rpm 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.

Where is the voltage sensing for the alternator attached in your particular system?

Re: Chassis Batteries

Reply #24 – December 22, 2015, 04:45:35 pm

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!

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