Questions on Battery Charging

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Questions on Battery Charging

December 18, 2013, 11:59:10 am

Even after reading through past posts and Barry's excellent site, I still have some questions concerning my charging system and my batteries. I am currently using 2 12 volt 8 D wet cell batteries for my house batteries. I replaced my 8 D starting battery in January with a sealed wet cell maintenance free w/ 950 CCA at 0 deg. I do not winterize my coach as I begin my annual Florida trip in the first week of January. On nights that will be below freezing, I plug into shore power (30 amps) and set the thermostat at it's lowest setting ( 50 deg. ). I disconnect when the temp. rises above freezing because leaving it connected boils, for lack of a better term, the water from my house batteries.
Question 1: Does the coach charger only charge the house batteries if the boost switch is not on?
Question 2: Would the same thing occur with sealed maintenance free batteries?
Question 3: Will disconnecting the house batteries while connected to shore power cause any problems?
I did this last night and checked the voltage on the cables going to the house batteries and I have 13.4 volts coming from the house charger.
I have a Genius Battery Charger/Maintainer connected to my starter battery.
If this set up causes no problems, it beats trying to keep the batteries filled.
Question 4: As I do very little dry camping, could I get by with 1 house battery? If so, what kind and size should I buy?

Thank you all in advance and Merry Christmas.
Jerry

Re: Questions on Battery Charging

Reply #1 – December 18, 2013, 12:04:34 pm

ANSWERS IN SOLID LETTER CAPS.

Quote from: Jerryetc – December 18, 2013, 11:59:10 am

Even after reading through past posts and Barry's excellent site, I still have some questions concerning my charging system and my batteries. I am currently using 2 12 volt 8 D wet cell batteries for my house batteries. I replaced my 8 D starting battery in January with a sealed wet cell maintenance free w/ 950 CCA at 0 deg. I do not winterize my coach as I begin my annual Florida trip in the first week of January. On nights that will be below freezing, I plug into shore power (30 amps) and set the thermostat at it's lowest setting ( 50 deg. ). I disconnect when the temp. rises above freezing because leaving it connected boils, for lack of a better term, the water from my house batteries.

Question 1: Does the coach charger only charge the house batteries if the boost switch is not on? CORRECT

Question 2: Would the same thing occur with sealed maintenance free batteries? YES, WIRING DETERMINES WHAT BANKS GET CHARGED, NOT BATTERY TYPE.

Question 3: Will disconnecting the house batteries while connected to shore power cause any problems? MAYBE. A BATTERY ACTS AS A "FILTER" FOR THE DC POWER YOUR CONVERTER OR CHARGER PUTS OUT. SOME ELECTRONICS MAY BE SENSITIVE TO "UNFILTERED" 12 VDC

I did this last night and checked the voltage on the cables going to the house batteries and I have 13.4 volts coming from the house charger. CORRECT READING.

I have a Genius Battery Charger/Maintainer connected to my starter battery. SHOULD WORK-- WHAT ARE VOLTAGE READINGS AT THE CHASSIS BATTERY?

If this set up causes no problems, it beats trying to keep the batteries filled.

Question 4: As I do very little dry camping, could I get by with 1 house battery? If so, what kind and size should I buy? YES. NOT SURE I WOULD GO LESS THAN A SINGLE 8D OR PAIR OF GOLF CART 6 VDC BATTERIES IN SERIES.

BRETT

Thank you all in advance and Merry Christmas.
Jerry

Re: Questions on Battery Charging

Reply #2 – December 18, 2013, 12:29:48 pm

Jerry,

Boost switch/solenoid has a constant current draw to keep it on. It will draw more current than a trickle charger can supply. You could install a "latching solenoid" and eliminate the loss. I just connect a couple of jumpers from the house to the engine battery. Keeps the engine battery full. Your charger should not boil the water out of the batteries unless the voltage is too high.

Follow Brett's advice on the batteries. A shallow discharge on two batteries will greatly extend battery life over just one that discharges more. Lots of folks use a pair of Trojan 6 volt T-105 batteries and swear by them. Couple of web blogs from RV owners if you search. From just over $100/ea to $225/ea for the "true deep cycle" type. I had a couple in my Buffalo Bus and loved them.

Pierce

Re: Questions on Battery Charging

Reply #3 – December 18, 2013, 02:13:42 pm

Thanks to you both. Brett, the chassis battery read 12.3 volts this morning. It was connected to the Genius charger though.
I am wondering what DC load would be on besides the heater motor?
Also I re-read my second question and it should have said " would the boiling of the water from the cells occur with a sealed wet cell battery"?
Thanks again.
Jerry

Re: Questions on Battery Charging

Reply #4 – December 18, 2013, 02:16:46 pm

Golf cart batteries are taller than 8D batteries, so they may not fit in your battery box. You should measure it first.

Re: Questions on Battery Charging

Reply #5 – December 18, 2013, 04:50:08 pm

Quote from: Jerryetc – December 18, 2013, 02:13:42 pm

Thanks to you both. Brett, the chassis battery read 12.3 volts this morning. It was connected to the Genius charger though.
I am wondering what DC load would be on besides the heater motor?
Also I re-read my second question and it should have said " would the boiling of the water from the cells occur with a sealed wet cell battery"?
Thanks again.
Jerry

Jerry,

12.3 is a 50% discharged battery. Clearly, either that small charger for the chassis battery is not working or there is some other load on even with the key off. You mention fan. The only fan powered by the chassis battery is the dash HVAC fan. Furnace fan, etc are powered by the house battery.

And overcharging will hurt any battery. What converter, charger or inverter/charger do you have?

Brett

Re: Questions on Battery Charging

Reply #6 – December 18, 2013, 07:41:45 pm

Jerry,

When the boost solenoid is switched on, the solenoid control circuit draws .70 amps so can draw down the batteries if no shore charger. Memory for radio(s), clocks, etc. will also add up. Heater motor(s) on a cold night can also run the battery(s) down. Won't take long for a 12.7 full charge down to 12.3V in the morning to shorten the battery life. That is 50%.

Pierce

Re: Questions on Battery Charging

Reply #7 – December 18, 2013, 10:04:55 pm

A 91 u240 would have come with a progressive converter or the silver converter. These were notorious for overcharging the batteries. Many people on here have changed to the smart chargers on this vintage of coach.

Re: Questions on Battery Charging

Reply #8 – December 18, 2013, 10:11:11 pm

Quote from: red tractor – December 18, 2013, 10:04:55 pm

A 91 u240 would have come with a progressive converter or the silver converter. These were notorious for overcharging the batteries. Many people on here have changed to the smart chargers on this vintage of coach.

So right. We really need to know what he has. Even the best batteries can be badly abused by a "not-smart" converter.

Re: Questions on Battery Charging

Reply #9 – December 19, 2013, 04:12:39 pm

OK, first let me thank you all. You have confirmed pretty much what I thought each battery feeds. I installed the Genius charger charger on the chassis battery and plugged it into the outdoor receptacle over the battery compartment. Thus when the coach is connected to shore power with the boost switch off, the chassis battery is kept charged.
The fan (on the furnace ) is the only DC draw that I know of. By disconnecting the positive side of the house battery, I hope to keep from overcharging ( boiling ) the house batteries. Brett, there should be no problem with the 12 volt electronics if only the furnace fan is running, correct? Red Tractor, how do I identify which converter I have? As I said in an earlier reply, I am reading 13.4 volts on the house battery cables.
With only the furnace fan running periodically, this seems like a lot unless it would cut back once the converter senses the batteries are fully charged. I do not think this is happening.
By the way, I just checked the chassis battery after it had been off charge all night and the voltage was 12.6. I think I am good with it.
You opinions are much appreciated.
Jerry

Re: Questions on Battery Charging

Reply #10 – December 19, 2013, 04:19:47 pm

Jerry,

13.4 VDC is just fine unless it in the hot summertime. That will not overcharge the batteries. If you have excessive outgassing at that voltage, you likely have a bad cell. Something you need to check out by disconnecting and having a load test done after fully charging them (any place that sells batteries can do that for free.

If your U240 is set up as the 1993's the converter is behind the entrance step-- access is from the driver's side bay just behind the generator.

Clearly, if you have the OE converter, there are a LOT of better smart chargers out there.

I still highly recommend solving the battery/charging/overcharging issue and leaving the batteries and converter or charger on.

Brett

Re: Questions on Battery Charging

Reply #11 – December 19, 2013, 05:50:03 pm

Quote from: wolfe10 – December 19, 2013, 04:19:47 pm

Clearly, if you have the OE converter, there are a LOT of better smart chargers out there.

I still highly recommend solving the battery/charging/overcharging issue and leaving the batteries and converter or charger on.

+1 to this advice.

The OE converter/charger was the first upgrade I did to my U225. Access is... um... interesting; we have a Joey Bed so one of us laid on it and the other pushed it in and then stood by for crimping connectors, etc. We chose a 45-amp Progressive Electronics model with the "charge wizard". For about $150 it is an excellent investment. My Tri Tec 2500 battery voltage monitor shows 13.1VDC most of the time and it shows me the current flow (amps or, mostly, milliamps). (The TriTec was the second upgrade; then LED HDTV set forward and aft.) Another $150 but invaluable if you plan to do solar.

Craig

Re: Questions on Battery Charging

Reply #12 – December 19, 2013, 08:28:47 pm

Craig, I guess I have my priorities backwards. I did the TV upgrades first. I will definitely
look into the converter/charger swap. That will give me something to do while the DW is searching for shells in Florida.
Thanks to everyone for your help.
Jerry

Re: Questions on Battery Charging

Reply #13 – December 19, 2013, 09:05:51 pm

Like Brett said about the location of the converter. I can not remember the name of the silver converter, but they ruined many a battery. They are a 75 amp converter charger, but do not go into float mode so tend to overcharge the batteries.

Re: Questions on Battery Charging

Reply #14 – December 19, 2013, 10:11:18 pm

another vote on the converter. Had one of those silver ones and boiled/ruined coach batteries. Easy replacement to a PD converter.

Re: Questions on Battery Charging

Reply #15 – December 20, 2013, 01:03:28 am

While driving is it ok to keep the boost switch on?
By leaving the boost switch on while driving the alternator should also charge the house batteries?
Thank you

Re: Questions on Battery Charging

Reply #16 – December 20, 2013, 01:23:35 am

Quote from: propman – December 20, 2013, 01:03:28 am

While driving is it ok to keep the boost switch on?
By leaving the boost switch on while driving the alternator should also charge the house batteries?
Thank you

It should not be needed, as the isolator connects the house batteries to the alternator when the engine is running. But it shouldn't do any harm either.

Re: Questions on Battery Charging

Reply #17 – December 20, 2013, 07:28:13 am

Mineral Oil and wet cell batteries go well together, unless you get your jollies checking levels and cleaning batteries.
Add enough to cover the surface of the cell and note how well it controls gassing issues (not quit maintenance free.. but close).
A 10 amp floating & temp sensitive charger (new design) keeps batteries going for years. pc

Re: Questions on Battery Charging

Reply #18 – December 20, 2013, 09:02:50 am

Greetings

Just my experience on boost switch, (GV ORED) electrical guru's needed- same setup

I did this on a 200 mile trip because engine bat was down, then turned it off.
12v did not work at camp. Checked batteries to find solenoid was melted in the battery box and the boost switch was non functional.

So after it was fixed, I installed a jumper #14 wire to prevent that.. trouble with it, it will draw both ways, house-engine.

Hope our experience helps you!

Re: Questions on Battery Charging

Reply #19 – December 20, 2013, 10:16:24 am

"isolator connects the house batteries to the alternator when the engine is running" Yes :-) I knew that

Thank you.

Re: Questions on Battery Charging

Reply #20 – December 20, 2013, 10:52:47 am

John,

Jumper wires around batteries are a very sensitive subject.

A small wire carrying lots of current= resistance heater. Have seen them glow red hot and can easily cause a fire.

Even large-gauge wires are subject to major issues. Since both ends are connected to batteries, if either end of the jumper comes off and touches a negative terminal or any piece of metal on the coach-- DEAD SHORT.

A better way to bypass a solenoid is to: 1. Label the wires on one large lug. 2. Remove them from that lug and join them to the wires on the other large lug. You have electrically achieved the same thing as if the solenoid was working with no danger of fire.

Brett

Re: Questions on Battery Charging

Reply #21 – December 20, 2013, 11:08:55 am

Brett

Total agreement!

Re: Questions on Battery Charging

Reply #22 – December 20, 2013, 05:35:52 pm

Brett and Craig,
You were correct on the location of my converter. It is under the top entrance step and is silver in color, so I am assuming that is one of the battery killers. Changing out is another challenge. Craig, I am also assuming you you are not 6'4' and 270 lbs. Maybe I will find a dealer offering free installation, though most of the time the price tag is increased to make you realize that very few things are free.
Thanks again.
Jerry

Re: Questions on Battery Charging

Reply #23 – December 20, 2013, 11:05:41 pm

Does your charger-converter look anything like this? On the end opposite the wiring, there is a cooling fan. I believe this unit was original equipment on our '93 U280 SE. I am in the process of replacing it with a "smart" charger-converter.

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Re: Questions on Battery Charging

Reply #24 – December 20, 2013, 11:47:12 pm

Quote from: cajk – December 20, 2013, 11:05:41 pm

Does your charger-converter look anything like this? On the end opposite the wiring, there is a cooling fan. I believe this unit was original equipment on our '93 U280 SE. I am in the process of replacing it with a "smart" charger-converter.

It doesn't look anything like the one I took out of our '93 U225. It looks a decade newer. I suspect someone replaced the OE version. You might want to see if it's already smart enough.

Craig

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