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Old 02-18-2011, 06:52 PM   #1
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1989 29' Excella
1979 31' Sovereign
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Only one battery charging

I have a 1989 29' with dual batteries. Went to start spring cleaning, and saw that batteries seemed to be showing signs of boiling over. I pulled both batteries and had them checked out. Street side showed 11.10v with 102 CCA but curbside showed 13.41v with 899 CCA. Batteries are identical age and size (2yrs old). These are the specifics:

The TT was connected to shore power full time.
Have new 40 amp 3 stage converter.
The built in battery checker showed 3/4 charge.
Ground from each battery goes to a common lug. Positive lead from each battery goes to Airstream OEM battery shut off switch.
PO had 100w solar panels installed but wired to rear of refridg, not to batteries. Solar has 3 stage charging and indicator lights appear be functioning properly.

How should I split batteries and their respective charging so I can check on each battery individually and/or isolate each? It appears that converter is reading only one battery as "charged" and switches to float mode and does not complete charge to 2nd battery.

I am stumped and could use any and all imput.
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Old 02-18-2011, 07:15 PM   #2
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Battery Cables

The cables should be attached + on one battery and - on the other. It has to charge when hooked like this. You may have a loose cable on the bad battery? which is possible the way yours is attached.
I don't think the solar attached to the heavy wire to the fridge is a problem, but if there is no charged controller attached to the solar, that would boil the batteries. You need an MPPT controller for max. benifit.
Dave
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Old 02-19-2011, 05:19 AM   #3
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masseyfarm thanks for the reply.
Solar has a MPPT charge controller attached. Could the solar MPPT be conflicting with the converter?

The (-) terminal goes to a common lug (original from AS). Do you think I should remove (-) from lug and route directly to the other battery?

I have been considering installing a Perko marine battery switch/isolater so I can manually Isolate/test/charge each battery. All my connections to batteries are clean and tight.
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Old 02-19-2011, 05:27 AM   #4
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I would charge the "low" battery, let it sit 24 hours, and check it again. If it's still low, it will need to be replaced.
And, of course, the other one should be replaced at the same time so they are both "matched".
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Old 02-19-2011, 08:20 AM   #5
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Battery Cable

I believe your two batteries are individually connected to a common lug. If you have a loose or corroded cable only one battery will charge. I think they should be connected in PARALLEL. (search Google for many informative sites)
After you charge and specific gravity test the battery, if it looks OK reinstall in PARALLEL.

"Why parallel?
A parallel arrangement means that current is shared between batteries and this means that each battery is exercised less vigorously which may increase usable capacity. Since removing any single battery will not change the voltage, there is a redundancy in batteries that can be useful in the event of failure (if that failure is detected early enough). Parallel is also useful in low voltage systems because it may be easier to find batteries at needed supply voltages. A failed cell in a parallel bank will sap energy as the other cells try to charge it (all the time, which adds up in sapping energy). This can cause heat and loss of water in the failed cell that run a battery down by itself."


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Originally Posted by heslinhotel View Post
masseyfarm thanks for the reply.
Quote:
Originally Posted by heslinhotel View Post
Solar has a MPPT charge controller attached. Could the solar MPPT be conflicting with the converter?

The (-) terminal goes to a common lug (original from AS). Do you think I should remove (-) from lug and route directly to the other battery?

I have been considering installing a Perko marine battery switch/isolater so I can manually Isolate/test/charge each battery. All my connections to batteries are clean and tight.

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Old 02-20-2011, 06:03 AM   #6
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Question Battery

I charged the weak battery seperatly per overlander66 suggestion. It has since tested good. I will switch to a parallel wireing configuration and see how it responds. Can't thank you guys enough, both masseyfarm and overlander66. Karma to you both for the assist.Do either of you see a benefit or drawback to installing battey isolater swich such as the ones in boats that would replace the OEM battery switch? It would give me ability to direct charging to one or both batteries.
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Old 02-20-2011, 06:44 AM   #7
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Originally Posted by heslinhotel View Post
Do either of you see a benefit or drawback to installing battey isolater swich such as the ones in boats that would replace the OEM battery switch? It would give me ability to direct charging to one or both batteries.
It would also give you the ability to switch everything "off" for longer term storage.
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Old 02-20-2011, 08:40 AM   #8
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Battery Disconnect Switch

Unfortunately, when the batteries are wired in simple Parallel pattern, you can not disconnect one without losing all power.
You could wire in a bypass with the disconnect switches, but that just gives more connections to create more potential problems.
With your solar, you would not want to shut off your batteries anyway, except for emergency.
If you want to charge each individually, leave them wired independent and install disconnects, and digital volt gauges, so that you can easily monitor them. You have a good supply of solar that will be wasted if both batteries can not benefit.

If you disconnect the batteries, the solar controller may supply more juice to the fridge curcit than wanted and that could result in burning the print board????????? so you may want to disconnect the solar also?
Dave



Do either of you see a benefit or drawback to installing battey isolater swich such as the ones in boats that would replace the OEM battery switch? It would give me ability to direct charging to one or both batteries.[/QUOTE]
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Old 02-21-2011, 06:02 AM   #9
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Battery

Dave
Thanks for the insight about solar panels wired to fridge. I think I will go with parallel configuration. The thought of frying my new fridge was something I had not considered. I will also install volt gages as well to monitor the batteries. Will parallel hook up let me monitor each battery or will it just read combined batteries?
Steve
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Old 02-21-2011, 08:27 AM   #10
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Battery Monitor

Good question. (On my own setup, when I test with my digital meter, each battery will read a minor voltage difference, but they are wired together so I don't think that is a true reading. I would disconnect one cable for a accurate test.)

So, I think it necessary only to have one meter on parallel wire batteries.
If wired in parallel, as noted in above post, a bad cell will draw down both batteries, so you will see the problem with a single Volt Meter. If you have access to them, a specific gravity test then is really the only way to determine where a problem is.
If you were going to keep the 2 batteries separated, and manually control the charge, it would be important to have a Volt gauge on each.
Just for info I copied from another post how I have mine set up. It is a bit more info than you need as I have a charge source to each battery bank.
Dave


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Dave
Quote:
Originally Posted by heslinhotel View Post
Thanks for the insight about solar panels wired to fridge. I think I will go with parallel configuration. The thought of frying my new fridge was something I had not considered. I will also install volt gages as well to monitor the batteries. Will parallel hook up let me monitor each battery or will it just read combined batteries?
Steve


Here is what I did on my CLIPPER. (Cummins CT300)
I have a upgraded Delco SI 22 130A alternator, charging 2 X HD wet cell starting batteries, bank #1, (soon to be replaced with the same type), and have removed the ISOLATOR because of the voltage drop.

I have installed a SurePower 1315-200 SEPARATOR.(replaces the isolator) and allows charging both ways over 13.2V.
I have installed a cockpit controlled solenoid between the chassis and the ISOALTOR so I can manually control the combined or separate charge.
I have 4 X 6V T105's for the house bank #2.
I have one Trojan deep cycle wet cell 12V up front for the electronics. This has a charge line from the house battery circuit and another tie to the chassis circuit, which both have manual switches in the cockpit that I control as needed.
Xantrex Freedom Inverter Charger 2000 Watt 12 VDC 3 stage charger for the house #2 battery bank. (will charge all if switches and solenoid activated. AUX diesel 7000W slightly used.
All system are monitored in the cockpit with DIGITAL VOLT GAUGES.
SOLAR: 20W polycrystalline, charge controller, manual switch (to feed chassis or house depending on the need) Can be left on either, depending on solenoid setting between battery bank #1 or #2.
253W polycrystalline panels (4) run thru a MMPT controller to the #2 battery bank.
2 X 5.5W monocrystaline panels (no charge controller) to the #3 battery up front. Powers a 400W invertor for the electronics.

My experience with this setup is:
While camping, if the sun is shinning next day, I can boomdock overnight and leave the house batteries on all the SOLAR and they will completely charge. (in this case I have the solenoid between 1&2 bank connected so that any solar over capacity goes to the chassis battery. If not using the #3 invertor I will tie this panel in also to the house.

When travelling during the sunny day after boomdocking, I will separate the #1, #2, #3 banks. This allows SOLAR to charge the #2 and #3 and the Delco to run the chassis load of DRL, AC, fans, etc.
In theory I should get better fuel mileage as the alternator is not running the # 2 or #3 if not necessary.
NOTE: THE SOLAR WILL NOT PRODUCE IF YOU ARE CHARGING FROM THE ALTERNATOR AT THE SAME TIME AS THE CONTROLLER WILL SIGNAL THE BATTERY IS AT CAPACITY.
ALWAYS DOCUMENT UPGRADES SO THAT FUTURE SERVICE WILL BE POSSIBLE WITHOUT UNNECESSARY EXPLORATION COST.
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Old 02-21-2011, 11:14 AM   #11
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If your wiring was as you've described (parallel), and both ends of the battery cable connections are secure and corrosion free, both batteries should be receiving the same charging current...

A dirty, or corroded connection on any one of the cables could account for the difference in charge levels between batteries - as others have noted above...

Usually, if one of the batteries' voltage is around 10 volts, you have a shorted cell in that battery. In a parallel connection, the charger will detect a low state of charge status for the 'pair' and try to charge at a high rate. This could (usually) result in water loss (evaporating), especially in the 10 volt battery!

I wouldn't think the AS battery meter would show '3/4' level for the batteries with the new converter/charger running??? That's somewhat of a mystery?? I would think the output voltage of the C/C would be high enough to show a 'full' charge, especially due to the one battery being charged up fully...? You've got me on that one...

With regard to the solar input hook-up...I've always hooked my solar 'charging' wires directly to the batteries themselves (with a fuse for protection) to eliminate as few connections as possible and any inherit resistance caused by mechanical connectors, etc...

Some suggestions:
1. I'd let that low voltage battery 'rest' about 24 hours with one of the cables removed, to allow it to stabilize without any activity - then test it again to see if it's voltage has dropped again indicating a 'weak' cell...or...if possible take hydrometer cell readings before and after 'resting' to see if you have one weak cell...

2. check all battery cable connections on both ends of the cables...

3. With the C/C OFF, you can take voltage readings of both batteries - then turn the C/C back ON and read the voltages again to see if BOTH batteries are receiving the same charging voltage...

4. As others have pointed out, you want two batteries of the same 'vintage' in your AS, so with your batteries being two years old, it's probably best if you replace BOTH if one is indeed bad...

Happy Trails...
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Old 02-21-2011, 08:49 PM   #12
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Quote:
Originally Posted by heslinhotel View Post
Ground from each battery goes to a common lug. Positive lead from each battery goes to Airstream OEM battery shut off switch.
PO had 100w solar panels installed but wired to rear of refridg, not to batteries. Solar has 3 stage charging and indicator lights appear be functioning properly.


The original description indicates not a true parallel setup.
Parallel would have the + to the airstream, + and + of second battery connected, and - and - connected and - of the second battery connected to ground. This allows the current to travel through both batteries. Both batteries will charge or discharge equally unless there is a fault in one battery.
Dave
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