Starter Batteries 101

Topic: Starter Batteries 101 (Read 919 times) previous topic - next topic

Starter Batteries 101

April 20, 2021, 07:55:32 pm

OK.....
I should know this. But I need a little schooling. It is important that you read everything that I describe, in order to " set me straight".
I KNOW my house batteries are old. I should have replaced them this past summer, but we have been in Mexico for close to six months now, without incident. Well, not exactly.....
We disconnect the coach from the land line, every morning, and just use the inverter and my 360 watts of solar that a previous owner had installed. At night, we reset the breaker box, and have been doing this for months. Please NOTE: when I reset the breaker for land line power, I DO NOT press the " CHARGER" button on the Magnum Control.
It is my understanding that the HOUSE batteries would get charged without my having to press this button. I MAY BE WRONG.

So......
Last month, I went to start up the coach, just to see what"s what.....DEAD. Wouldn't start even with the boost switch on.
In fairness, these were good Crown batteries with 940 cca, BUT they were six years old.
When we first bought the coach about five years ago, I brought it to OLD TOWN MOTORS, and they talked me into installing a BEF Digital Voltage Relay which they explained was necessary to charge BOTH BATTERY BANKS......

??
I thought that meant that the house batteries would charge and THEN the coach batteries, while driving, OR when plugged into land line.
I had been able to throw a charge on the start batteries, and the coach would "fire"ok. We are getting ready to return to the states, so I was debating whether or not to buy batteries here, or hope to hobble the coach back to Texas, and buy them there.
I opted to buy here, and just installed three HD batteries, made in Mexico by Johnson Controls, with 950cca each.
MY QUESTION IS:
what might I be doing wrong?
As of yet, I did NOT connect the negative side of the batteries. I fear that I might somehow be draining them, when I THINK I am charging them.
Can someone set me straight.
do I have to press the charging button when we are on land line?
Is that just for house batteries???
Or, with that BEP unit, are BOTH battery banks charging???
Please help me understand this. I don"t want to ruin my shiny new batteries.
Thanks

Re: Starter Batteries 101

Reply #1 – April 20, 2021, 08:06:11 pm

Not being a Magnum owner I can tell you that with my Xantrex SW3012 If I don't activate charge there is nothing being put into my batteries. I would think a Magnum would work the same way.

Re: Starter Batteries 101

Reply #2 – April 20, 2021, 08:11:09 pm

I keep the charge button activated. I have my chassis batteries set up so they are charged from the house batteries.

Re: Starter Batteries 101

Reply #3 – April 20, 2021, 08:46:39 pm

I hate surprises so as in my old posts, I installed LED voltmeters where the old Audit system was. That way, I can see in a split second what the voltage is in each bank. I do tie them together with a jumper from one lighter plug to another. The voltmeters are on 24/7 for the last 12 years. Even when I wake up during the night, the big red numbers make it hard to miss low voltage.

You have to keep it simple and easily monitored. I don't trust any other way. Our old house batteries still are working really well years and years later.

Pierce

Re: Starter Batteries 101

Reply #4 – April 20, 2021, 10:34:31 pm

Glenn,

We have a Magnum MS2812. I think all the Magnum pure sine inverter/chargers work pretty much the same.

On my Magnum control panel, there is a separate button for the charger and the inverter. I can manually turn on either function, or both functions, as desired. I keep both functions turned on all the time. That way the Magnum automatically switches between charger and inverter in case we lose shore power at night. I will guess that yours works the same, so I think you should turn ON the charger whenever you want your HOUSE batteries charged. Doesn't matter how the inverter/charger is being powered - shore power or generator - works the same either way.

The BEP solenoid is supposed to do just what the OLD TOWN tech said: it charges the START batteries when the HOUSE batteries are receiving a charge. This is the same thing as turning on your BOOST switch, but the BEP does it automatically. The BEP will also disconnect the two battery banks when the HOUSE batteries are not being charged. See if the model linked below looks like what they put on your coach (yours may be a older version of the same thing):

Digital Voltage Sensing Relay (DVSR) 12/24V | BEP

Check the resting voltage on both battery banks with your voltmeter. Then plug in to shore power and try turning on the battery charger function and see what happens. You should quickly see the voltage on both battery banks increase if everything is working right. If the HOUSE battery bank voltage goes up, but the START battery bank does not, then the BEP might not be working.

Re: Starter Batteries 101

Reply #5 – April 20, 2021, 11:44:05 pm

By default, the Magnum inverter should charge your house batteries when 120V is applied to it's input (charge LED on). Pressing the charge button on your ME-RC, after applying power (shore or generator) will put the charger in standby mode (charge LED blinking) and will not charge.

Regarding the BEP Digital Voltage Relay, the overview states "Charges engine starting batteries before combining auxiliary bank for charging" I take that as it's an alternator driven combiner with chassis battery priority. Meaning, while the engine is running, it will charge your house battery once the chassis battery is mostly charged. It does not appear to allow charging of the chassis battery from the house battery charging systems. You can charge the chassis battery by turning on the boost switch whenever your house battery is charging (via solar or inverter/charger)

Greg

Re: Starter Batteries 101

Reply #6 – April 21, 2021, 12:31:42 am

I won't argue with Greg's statement about the Magnum (above) but I will add this from my experience. Regardless of the default on the Magnum inverter/charger, it will not charge the HOUSE battery bank unless the yellow "CHARGER" LED is on steady. SO, if you have shore power connected (or generator running), and the yellow "CHARGER" light is off, turn it on. If it is blinking, push button again so LED is on steady.

As to the BEP device, I believe it can be connected with either the HOUSE battery bank OR the START battery bank as "primary". The poop sheet on the page I linked simply says:

"The Digital Voltage Sensing Relay (DVSR) allows the charging of a second battery bank from any single charging source."

AND

"Safely charge two or more independent battery banks from one charge source such as an alternator or battery charger."

The BEP may indeed prioritize the START battery bank when charging, however I don't think this rules out the possibility that it could be connected to the inverter/charger rather than to the alternator as the primary charging source. In fact, according to the installation instructions, it provides bi-directional charging capability so both charging sources may be fully utilized:

"DVSR Operation Explained - Charging: The DVSR is connected between two battery banks. When the DVSR senses a charging voltage (13.4VDC or 26.8VDC) on either of the banks, it automatically activates and joins the two battery banks after a short delay (5 seconds), so they are charged as one battery bank."

https://www.bepmarine.com/en/~/media/inriver/329437-25323.pdf

Without examining Glenn's coach in person, I don't think we can state with certainty how his coach is wired. The simple check I suggested at the end of my post (above) should tell if my theory is correct.

Re: Starter Batteries 101

Reply #7 – April 21, 2021, 01:04:14 am

Having read the info provided in the above link, I have to agree with Chuck's opinion that the BEP should allow inverter/charger charging of the chassis battery, provided the house battery voltage is reaching 13.4VDC.

Re: Starter Batteries 101

Reply #8 – April 21, 2021, 08:43:39 am

Good theory above.

Now, pull out your digital voltmeter, hook up the new batteries and test voltage at both banks:

No shore power

On shore power charge button OFF and then with it ON

You certainly want to confirm that it actually works as it should.

Yes, a draw is something else. If you have an ammeter function on your digital voltmeter, you can check that as (immediately before) hooking up the ground cables to your chassis batteries.

Re: Starter Batteries 101

Reply #9 – April 21, 2021, 09:39:40 am

Regarding the Magnum MS2812,you can have one of 2 control panels,one has more funtions.

Re: Starter Batteries 101

Reply #10 – April 21, 2021, 10:37:00 am

If Glenn has a BEP DVSR (instead of a BEF DVR as he stated) and it is connected as described in the BEP instructions it may be fried. Max intermittent current is 140 amps and continuous is 125 amps.

360 watts of solar is likely not enough to maintain charge during the day. If he has a BEP and he plugs in overnight and actually charges the house batteries and they get to 13.4v then the start batteries should get charged until the house batteries fall below 12.8v.

So it seems his start batteries should have been getting some charge, if they are dead then probably not.

There are several ways this could have been installed. How is unknown. Maybe buy a decent multi step charger for the start batteries and hook it up to 120v. Disconnect the BEP if that is what he has especially if has malfunctioned. Leave the coach plugged in until you leave, Magnum charger on, inverter off until you disconnect.

Re: Starter Batteries 101

Reply #11 – April 21, 2021, 12:58:34 pm

It IS a BEP DVSR.
I believe I was told ( it was a long time ago), that it would allow house batteries to charge , THEN the coach batteries, BUT would assure me that I would have charge in start batteries.
I thought it worked with the alternator, not off the inverter/charger.
How can I tell if is fried??

Re: Starter Batteries 101

Reply #12 – April 21, 2021, 01:45:30 pm

Quote from: GleamB – April 21, 2021, 12:58:34 pm

It IS a BEP DVSR.
I believe I was told ( it was a long time ago), that it would allow house batteries to charge , THEN the coach batteries, BUT would assure me that I would have charge in start batteries.
I thought it worked with the alternator, not off the inverter/charger.
How can I tell if is fried??

Alternator should charge both batteries with/without the BEP device in place (through the battery isolator).

Again, pull out your digital voltmeter to "tell if it is fried". If you don't yet have one, even a test light should show change in brightness with higher voltage.

Before plugging in, check voltage at both house and then chassis/start batteries. Post the voltages for us.

Plug in, and once house bank reads above 13.4 VDC verify that chassis/start battery voltage is going up and unless deeply discharged, should read the same as the house battery bank.

Re: Starter Batteries 101

Reply #13 – April 21, 2021, 06:24:56 pm

Quote from: GleamB – April 20, 2021, 07:55:32 pm

As of yet, I did NOT connect the negative side of the batteries. I fear that I might somehow be draining them, when I THINK I am charging them.
Can someone set me straight.

Both battery terminals need to be connected for the current to flow.

FWIW I finally broke down and purchased a PD 9260 for my chassis battery, so I'm dedicating a $220 3-stage 60A battery charger just to my chassis battery because I've ruined too many by leaving the headlights on.

FWIW 2 You can purchase a bi-directional disconnect relay that connects whichever battery is higher to the one that's lower. But Foretravels come from the factory with a sold state battery isolator and house and chassis batteries charge when the engine is running.

Re: Starter Batteries 101

Reply #14 – April 21, 2021, 07:49:01 pm

Again, pull out your digital voltmeter to "tell if it is fried". If you don't yet have one, even a test light should show change in brightness with higher voltage.

I have three voltmeters with me. How do I check the BEP. What am I checking? Are there four terminals...

??I need to open up the engine and start checking things. We're leaving soon. I'll test it then. Thanks

Brett, how do I test the battery banks? Do I just go pos/neg on one of the three? I haven't yet hooked up the neg of my brand new start batteries. Don"t see the need at this point in time

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Re: Starter Batteries 101

Reply #15 – April 21, 2021, 08:02:50 pm

You will do all the checks at the batteries.

If they are 12 VDC batteries wired in parallel, check between any positive and any negative.

If 6 VDC wired in series/parallel, check between the positive with the cable going to house/loads and the negative of the ground cable going to chassis ground.

Re: Starter Batteries 101

Reply #16 – April 21, 2021, 09:33:44 pm

Quote from: GleamB – April 21, 2021, 07:49:01 pm

I have three voltmeters with me. How do I check the BEP. What am I checking? Are there four terminals...??I need to open up the engine and start checking things. We're leaving soon. I'll test it then. Thanks

The quickest way to test connections is to turn something on to make electrons move, then measure the voltage across the contacts. Voltage=Bad. No voltage=Good.

Re: Starter Batteries 101

Reply #17 – April 23, 2021, 08:45:02 am

Maybe I'm wrong but I don't like the idea of using a device like that to charge dissimilar battery Banks. Your house batteries and much more capacity than your start batteries I think parallel and them together using a boost switch temporarily would be okay but I prefer separate chargers for each system. When I replace my optima start batteries with odysseys, I upgraded the trickle start to the AGM model as he original was for a wet cell lead acid. Each battery technology requires a slightly different charge profile. I have course don't have your setup but yes you have to have the inverter set to charge to charge your battery Bank. And it's a good idea to monitor the voltages from time to time if not continuous. My system I have the victron energy color control as well as a battery monitor from victron I think it's the 712 but I forget for sure and I'm not in the coach right now. Or you can do is Pierce does and monitor it through the cigarette lighter plugs on the dash. That will tell you the voltage and whether or not they're charging or not. But the alternator should charge your start batteries and if not then that needs to be troubleshooted. My coach, a 99, as older systems in place originally and a lot has changed in both battery technology and charging ability and capability since then. Batteries cost a lot of money so it's really important to charge them properly.
Also I'm not sure what you mean by you didn't hook up the negative on the battery yet? Are you talking about your charger or are you talking about actually hooking the batteries up,? If so why wouldn't you hook them up?

Re: Starter Batteries 101

Reply #18 – April 23, 2021, 08:53:40 am

If the two battery banks are the same or at least compatible in terms of "best charge program", I have no problem with a battery combiner. Wet cells and AGM's play nice together. Wet cells or AGM's and Gels, not so much. Lithium ion NO.

So, no one answer for all coaches.

Re: Starter Batteries 101

Reply #19 – April 23, 2021, 10:10:18 am

Our AGM house and Wet conventional have worked well together. I keep them connected unless underway where the alternator/isolator keeps both charged.

Pierce

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