Increasing battery capacity (or am I?)

System · August 2011

My wife and I don't go off the grid really, we have wheelchair accessible 29 foot travel trailer. It was a standard model with the wheelchair option built in 2002 by Play-Mor. It was a great bargain, because accessible RV's are very expensive and we paid $22,000 at that time.
Although we stay at Missouri State campgrounds, we must have a reliable 12 volt source for the wheelchair lift to operate (for quick trips to use the bathroom while traveling).
Here is where we are, the battery box holds a single wet cell Walmart battery, barely enough to operate the lift a few times before recharging.
Once a year my wife's insurance replaces her wheelchair batteries, I was able to keep the last pair taken from her chair, they were charged nightly for the year they were in the power chair. The are Interstate "DCM 0055 AGM 12v 55 Ah 20 rate 1.75 VPC"
(taken from the top label). Definitely the price is right for the pair (free)

Since I'm only learning about this stuff now, my question is: if they are connected together in parallel, will they do the job? Is it still only 55 ampere hours?
It is quite a lot of battery (together) but 55 ah just seems is not as much power as most Rv batteries are advertised.
This is not a deep cycle situation, just a need for reliable power when we need it.
Thanks for any suggestions, I found the battery information pages on this site so good, I felt compelled asking my question here instead of a regular RV forum.
Ray D

mike95490 · August 2011

Re: Increasing battery capacity (or am I?)

Welcome.

Well, its handy to be able to keep that set of batteries. You sure save a bundle not buying them. They will need a 3 stage charger configured for AGM batteries, a regular flooded cell charger will over charge them.

Overcharge on AGM is bad, because you vent gas, which used to be electrolyte, but it's gone forever.

Any idea what the lift battery spec is ?

Cariboocoot · August 2011

Re: Increasing battery capacity (or am I?)

If you parallel two 55 Amp hour 12 Volt batteries you get 110 Amp hours @ 12 Volts.

But like Mike said you need to know the lift unit's battery specs to know if that will gain you anything.

BB. · August 2011

Re: Increasing battery capacity (or am I?)

First, knowing the load (i.e, 12 volt motor takes 50 amps for 30 seconds per cycle, etc...)...

If you do not have that information and want to learn a little bit more about electricity--a DC Current Clamp meter (really an AC/DC clamp meter with digital volt meter, ohm meter, etc.) would be really helpful. This Sears unit seems to be a very good value at ~$60. You can easily pay 2x to 7x or more for a very nice meter too, but this is a good one to start with.

What we are looking for is something like Amp*Hours per cycle... So, if your motor takes 50 amps for a 1/2 minute per cycle, it would look like:

50 amps * 0.5 min / 60 min per hour = 0.42 Amp*Hours per cycle

A 110 AH battery bank could, in theory supply:

110 AH / 0.42 AH per cycle = 262 cycles

Or ~131 round trip rides... Of course, this is nowhere near what you are seeing--So either my guesses are way off, or your battery bank is not working correctly.

And it is possible that you are not properly recharging the battery bank... So how are you doing it now (type/model of battery charger, how is it powered, what voltage is the battery bank being charged to, how long does it get charged, etc.).

It is not uncommon for batteries to be under charged (deficit charging) and have very little reserve capacity for operating the load--and/or sulfating in months which reduces capacity.

It is also possible that the battery bank is overcharged and being boiled dry. Again knowing the charging voltage(s) and time(s) would be helpful.

-Bill

Photowhit · August 2011

Re: Increasing battery capacity (or am I?)

...and it could be that the "...battery box holds a single wet cell Walmart battery,..." might be a car statrting battery, or asome other inapproprate battery, I'd start there.

What kind of battery is in the battery box? if you give use the complete listing, we can likely figure out the size as well as if it is the correct battery.

System2 · August 2011

Re: Increasing battery capacity (or am I?)

I want to thank you all for your time in responding to my post. I now know that I left a lot of information out.

The existing two year old battery is (from the top label)
everstart 75 AMPERE HOURS 100 RESERVE CAPACITY

(The following is from the Ricon service manual and ours is the 12 volt version)
The Ricon Wheel chair lift Power specs........................................................... electro-hydraulic Motor rating @ 12 volts DC ...... 65.0 amp avg/cycle, 1250 psi @ 24 volts DC....... 32.5 amp avg/cycle, 1250 psi Hydraulic cylinders ............ 2 ea, 1.5", power-up/gravity-down.

For a bit more information than any of you probably want to hear, this is the story of our trailer's battery/charging/converter system

The first season we used our trailer the Magnatek Power Converter worked perfectly. Battery power was nicely maintained (float?) minor electrolyte loss, it was great.
The second season, upon return from our first camping trip, I wasn't as vigilant in monitoring the system and discovered the battery was way overcharged and pretty much dry. Out of warrantee and short of money, I replaced the battery, and only kept it connected enough to charge and then I isolated the battery from the trailer and checked the battery every three weeks to maintain the charge. That worked for a couple of years, and then the system quit charging the battery at all.
When plugged in to our 30 amp the converter would run all of the 12 volt systems (except for the refrigerator, you need 12 volt from the battery to have that work), but not charge the battery. I thought it was somewhat of a blessing, because I could just use an external Sears auto charger to keep it going (even during our camping trips).
The price for the newer version of the charging part of the Magnatek is between 200.00 And 300.00.
Earlier this year I found a site describing a repair to the charging part of the converter
(http://www.hayseed.net/~jpk5lad/RV%20Information/MagnaTek%20Pwr%20Converter/rv%20power%20converter.html)
That was a relief as by following those instructions I was able to repair the unit for about $15.00. Life was good!
Midway through the first camping trip this year to Bennett Spring State Park in Missouri, it reverted to it's old behavior. I guess whatever caused the first failure to happen just happened again.
So here is my plan, yesterday I purchased from Amazon for $99.00 a NOCO G7200 NOCO Genius. This is going to be our new charging system, It is pretty new and appears to have quite a few redeeming qualities. It's small and I read it does a good job in maintaining a system.
I posed the question in my post because, the batteries I'm installing are not the type of throw away Walmart battery I was trying to keep alive previously, I would like to keep these two AGM's for a while. And not have to be carrying that Old fashioned Sears charger with an extension cord around the trailer.
What a story, I hope I've not bored anyone....
Thanks again for your time...
Ray S

mike95490 · August 2011

Re: Increasing battery capacity (or am I?)

The "lift battery" you describe, is a starting battery, and should be recharged after each use. It's able to supply the high amps needed for running the motor, but the thin plates don't like sitting discharged.

I'm not sure about the G7200 NOCO Genius charger, you need to be sure it selects the right battery type, using a flooded battery profile will ruin the AGM batteries - that's my only concern, is making sure the right type battery is selected. And it will take quite a while to charge a pair of low batteries at only 7 amps. 50% discharge is going to be in the neighborhood of 8 - 9 hours to recharge, with no loads.

AGM batteries are able to accept a high charge rate till they are nearly full, and then is a good time for the Genius charger to take over.

Cariboocoot · August 2011

Re: Increasing battery capacity (or am I?)

I agree with Mike: the NOCO charger isn't designed for the AGM batteries. It's high Voltage "desulphating" mode (EQ charge) will be bad for them. Pop the valve and they're done for. I think an Iota http://www.solar-electric.com/ioen12vo15am.html or similar that can do a two/three stage charge with a proper Voltage limit for AGM's would be better.

65 Amps average per cycle is a fairly high amount of current. The AGM batteries will be a better choice here, as they work with higher currents better than standard flooded cells. Even with 110 Amp hours of AGM battery that will be a difficult load.

System2 · August 2011

Re: Increasing battery capacity (or am I?)

Thanks for replying.

Momentarily getting back to the concept of using the wheel chair batteries, since they are of wheelchair design intent, they use 3/16 or 7/32 x 3/4" screws in the terminal holes. Does anyone know of a source of supply to connect to these terminal holes, (also to appropriately) connect the two batteries in parallel and to enable the connection to the trailer and the pretty heavy cable that must connect to the lift?

Regarding the 'Genius' line of products.
Marketing claims are always a bit suspect, but they are claiming a 'cold AGM mode' as an option, (although, I don't know how you employ the options)
They are a marketing dynamo. Check out the youtube at http://youtu.be/lhG3lMEnzeg

• Safely charges Wet, Gel, MF and AGM batteries...

These are their claims for the device...

G7200 is a smart, 12 Step, fully automatic switch-mode battery charger and maintainer. The G7200 restores batteries to their original capacity, recovers slightly sulfated batteries, charges batteries in cold climates, rescues drained batteries, and provides maintenance charging to increase battery life. A powerful battery charger with specialized charging modes for recovering severely drained batteries that will not accept a normal charge. Suitable for most 12V and 24V battery capacities from 14-230Ah, such as Motorcycles, ATVs, UTVs, Snowmobiles, Jet Skis, Cars, RVs, Boats and Trucks.
• Charges 12V and 24V batteries
• Returns to last selected mode when restarted
• Automatically adjusts itself to changing current needs
• Reverse polarity, short circuit, open circuit, spark proof, overheat, overcurrent and overcharge
• High-frequency, high-efficiency for a lightweight, compact charger
• Charges batteries 2X faster than traditional linear battery chargers
• 100-percent full charge even with varying A/C input voltages
• Recovers deeply discharged & sulfated batteries with pulse charging
• Safely charges Wet, Gel, MF and AGM batteries
• Automatically shuts off if charger remains in Bulk charge mode for an extended period of time
• Plug-n-play connectors for easy accessory changes
• Optimized charge mode for cold weather or AGM batteries
• Revive low voltage batteries & can act as a power supply
• Helps recover deeply discharged or sulfated batteries
• Includes: G7200 charger, battery clamp connectors, eyelet terminal connectors, owner's manual and user guide, product registration card
• ETL approved for US and Canada, RoHS compliant
• CONFORMS TO UL STD. UL1236 CERTIFIED TO CSA STD. C22.2 No.107.2

Does this mesh with anyones actual experiences?

I've read some reviews that thought that Iota products reliability are not so great. Failure rates and such. Experiences?

Thanks again from the pleasant (today) Missouri Ozarks,
Ray

Increasing battery capacity (or am I?)

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