Okay, time to buy a new battery... but, REPLACE my battery or ADD to it?!

[TMG51]

My class B motorhome had a 12v battery installed when I bought it. I'm planning to follow advice and install two 6v golf cart batteries, assuming I'll get better performance that way. My current battery is full all day with the solar panels charging it, but as soon as evening sets in I only get a couple charges on my laptop battery before the charge controller reports the house battery is overdischarged. So in other words, I'm not storing up that surplus during the daylight hours.

But when I buy two 6v batteries, should I take the old 12v battery out and REPLACE it? Or should I ADD the two new batteries in a series/parallel configuration? I'm not sure if this is a "more is merrier" situation or if the older battery would potentially inhibit performance. I have plenty of space to install a battery bank.

 

[WheelEstate USA]

Get rid of the old one. You'll need it for a core trade anyway.
You're quite correct...the old one will suck off the new set.

 

[highdesertranger]

I would remove the old battery and replace it with your two 6v. you should never mix old batteries with new batteries. I t sounds like that old battery is junk if you try to run it with your new batteries it will drain them as well. highdeserranger

 

[SternWake]

The remaining usable capacity of your current battery is has been too compromised.  It will likely short a cell soon if you keep draining it as far as you currently are.

2 6v golf carts will likely double your overall capacity, compared to when the single 12v was new, and they will be easier to fully charge and be more durable in a deep cycle application.

Your current battery will be a core charge for only one 6v golf cart so you will have to spend more for the core charge on the second.

Beware of blinking lights that indicate when a battery is full.  They are wrong 99% of the time on a deeply cycled battery. 
 The blinking green light indicates only that the controller has held absorption voltage as long as it was programmed to do so, and nothing more.  It does not mean some magical electrical wizardry has occurred where it has probed the battery and determined it can accept no more current, despite how much the general public would like to believe so.


Verification of full charge is only possible with a Hydrometer on flooded batteries, and with an ammeter on AGM.  Anything else is a guess, perhaps educated, but often the complete opposite with a good dose of ignorant arrogance thrown in for good measure.

Achieving full requires the right absorption voltage be held for long enough, and if one can figure this sweet spot out, one will get much enhanced battery life.  If not, battery life will be reduced in direct proportion to how well the battery is treated.

Discharge no more than 50% and achieve 100% SOC every day or nearly so, expect excellent battery longevity.

Take them below 50% and recharge them to 95%, expect less, and perhaps much much less.

 

[TMG51]

Great, sounds like I'm on the right track in replacing this battery and I'll turn in the old one.

Now just time to figure out where to buy golf cart batteries.

 

[LeeRevell]

Great, sounds like I'm on the right track in replacing this battery and I'll turn in the old one.

Now just time to figure out where to buy golf cart batteries.

Locally we have a "Battery Source" and a "Batteries Plus" stores.  Both deal in all types of batteries, and have the 6V Deep Cycle golfcart batteries.  BS also sells the carts and accessories.  They don't have the much-vaunted Trojans, but a supposedly 'equivalent' battery.

 

[ccbreder]

Batteries Plus Bulbs, did very well by me. The core was $12. Duracell 235AH, $109.

 

[TMG51]

I don't have a batteries plus or battery source in Vermont. The guy at Sears today tried to sell me on some 12v marine deep cycle batteries he had for $119 but I told him I was led to be skeptical that a 12v marine battery is a "real" deep cycle battery. I'll wait for interstate batteries to be open tomorrow and see what they have.

 

[SternWake]

Good call on the marine batteries, they are dual purpose and will have only half the cycle life, if that, compared to Golf cart batteries in deep cycle duties

Interstate is a battery marketer, not a manufacturer. Most of their batteries will be Johnson Controls offerings, who in my opinion make a good starting battery, and an OK marine battery, but are not known for their deep cycle offerings.

Their 6v GC batteries used to be made by USbattery, and were quite good, but no more. More profit margin for them with JC.

The price in gas you pay to travel to get real GC batteries could be significantly less than what it will cost to replace marine batteries much earlier.

The last battery distributor I went to relabelled Crown marine batteries as super cycling deep cycle batteries. They weighed 54 LBs and were marine batteries where as their deep cycle battery was supposed to be 64Lbs. When I confronted the distributor over this, they just repeated over and over that a marine battery is a deep cycle battery until I snapped and started scaring away other customers.

The sales men hid in the office and sent out the manager, who was wise enough not to argue. I wound up with a heavier USbattery for more money, and it performed pretty well, for being a 12v battery, but it wasted a lot of electricity to get it to last. It required rather obscene voltages be held for much longer before the SPecific gravity would max out, and this itself was abusive to the battery, but less abusive than chronically undercharging it..

A GC battery is much easier to fully recharge, and is more resilient to less than perfect recharging, and able to recover from abuse so much better.

It is worth the effort to obtain them, rather than settle for the compromised 12 volt jars that will resist efforts to attain full charge, and might fall over dead when accidentally abused by overdischarging

Any battery can be deep cycled. It is how well it stands up to repetitive deep cycling which differentiates the batteries.

A Marine battery is NOT a deep cycle battery. Its internals are much closer in design to a starting battery than it is to a true deep cycle battery.

Keep searching. Call up Golf Courses service departments. They generally retire/recycle GC batteries when they still have a lot of life left in them. Even these used batteries will likely outlast a new marine battery all factors being equal.

http://www.pbase.com/mainecruising/deep_cycle_battery

 

[MikeRuth]

You don't say what part of Vermont.
Try these folks and also call your local golf courses for there suppliers.

http://usabatterysales.com/default.cfm

Possibly no delivery charge if all works out.

 

[DannyB1954]

My experience with batteries in series or parallel is that if one goes bad it takes the other one with it. I prefer separate batteries on a selector switch. You can charge both of them at the same time with a solar cell and an isolator. The battery not being used by the selector switch will not stay at a low voltage condition for a long period of time.
(Just my opinion).

 

[TMG51]

Good call on the marine batteries,  they are dual purpose and will have only half the cycle life, if that, compared to Golf cart batteries in deep cycle duties

Interstate is a battery marketer, not a manufacturer.  Most of their batteries will be Johnson Controls offerings, who in my opinion make a good starting battery, and an OK marine battery, but are not known for their deep cycle offerings.

Their 6v GC batteries used to be made by USbattery, and were quite good, but no more.  More profit margin for them with JC.

The price in gas you pay to travel to get real GC batteries could be significantly less than what it will cost to replace marine batteries much earlier.

The last battery distributor I went to relabelled Crown marine batteries as super cycling deep cycle batteries.  They weighed 54 LBs and were marine batteries where as their deep cycle battery was supposed to be 64Lbs.  When I confronted the distributor over this, they just repeated over and over that a marine battery is a deep cycle battery until I snapped and started scaring away other customers.

The sales men hid in the office and sent out the manager, who was wise enough not to argue.  I wound up with a heavier USbattery for more money, and it performed pretty well, for being a 12v battery, but it wasted a lot of electricity to get it to last.  It required rather obscene voltages be held for much longer before the SPecific gravity would max out, and this itself was abusive to the battery, but less abusive than chronically undercharging it..

A GC battery is much easier to fully recharge, and is more resilient to less than perfect recharging, and able to recover from abuse so much better.

It is worth the effort to obtain them, rather than settle for the compromised 12 volt jars that will resist efforts to attain full charge, and might fall over dead when accidentally abused by overdischarging

Any battery can be deep cycled.  It is how well it stands up to repetitive deep cycling which differentiates the batteries.

A Marine battery is NOT a deep cycle battery.  Its internals are much closer in design to a starting battery than it is to a true deep cycle battery.

Keep searching.  Call up Golf Courses service departments.  They generally retire/recycle GC  batteries when they still have a lot of life left in them.  Even these used batteries will likely outlast a new marine battery all factors being equal.

http://www.pbase.com/mainecruising/deep_cycle_battery

Thanks, it's good to see my skepticism confirmed by someone who can articulate the rationale. I'd gathered the gist of this before through context of other discussions but you explained it well.

You don't say what part of Vermont.
Try these folks and also call your local golf courses for there suppliers.

http://usabatterysales.com/default.cfm

Possibly no delivery charge if all works out.

Well my current plan is to travel south next week so I was hoping not to have to mail order anything (but I could hang around and have it delivered to family if I need). That supplier does look pretty comprehensive. 

I spend time both in Burlington and in the central Vermont area.

So it sounds like interstate doesn't have a good deep cycle offering? I always heard them recommended for "regular" car batteries / cold starting amps.

 

[TMG51]

Looks like the T-105 is priced pretty reasonably. Wonder if I could go buy a couple at one of their NY distribution centers.....

 

[Sabatical]

I don't have a batteries plus or battery source in Vermont. The guy at Sears today tried to sell me on some 12v marine deep cycle batteries he had for $119 but I told him I was led to be skeptical that a 12v marine battery is a "real" deep cycle battery. I'll wait for interstate batteries to be open tomorrow and see what they have.

If you're in VT you have an excellent source for good batteries even Trojan if that's what you want. We live across the lake and have dealt with Dave Bonta at Sunnyside Solar. They are a couple hours south of Burlington. His prices are reasonable and he frequently does business elsewhere in the state, so he might neet up with you somewhere to deliver.

 

[Sabatical]

Looks like the T-105 is priced pretty reasonably. Wonder if I could go buy a couple at one of their NY distribution centers.....

I wasn't able to find anybody near northeastern NY when I looked.
Hello from across the pond. We are in Port Kent (on the other end of the ferry from the King st. dock).

 

[TMG51]

I lived on King St before giving up my place and taking to the van.

I think the Trojan T-105 or T-125 sound like they'd suit me well. I'll see if I can look up Sunnyside solar.

 

[DannyB1954]

I was just battery researching on the internet. If you are after 6 volt batteries the Trojan t105 come in two versions. The T105 and the T105RE.
The RE stands for renewable energy. They are built with thicker plates. Golf carts are still charged every day, maybe even twice a day. The batteries designed for situations in which they may be in a discharged state for a longer period of time have the RE designation. The web site I was on said they would last for more years than the golf cart design. They have more lead in them, so the cost is higher.

One thing that I stumbled on was Lithium Deep Cycle Batteries. A lot lighter, a lot more expensive, but said to last 10x longer. One other feature of them is you get more usable power out of the amp hour rating. A lead acid battery can be discharged to 60% of rated capacity, the lithium 80%. As time goes on I am sure they will get cheaper.
I am thinking about going that route myself because of the weight. 20lb vs. 70lb. In a half ton rig, I would rather not have the weight.
Here is an info link to a video about them.

 

[Sabatical]

I've misplaced the phone number but it's in W. Brattleboro.

 

[Sabatical]

Try sunnysidesolar.com

 

[Optimistic Paranoid]

One thing that I stumbled on was Lithium Deep Cycle Batteries. A lot lighter, a lot more expensive, but said to last 10x longer. One other feature of them is you get more usable power out of the amp hour rating. A lead acid battery can be discharged to 60% of rated capacity, the lithium 80%. As time goes on I am sure they will get cheaper.
I am thinking about going that route myself because of the weight. 20lb vs. 70lb. In a half ton rig, I would rather not have the weight.
Here is an info link to a video about them.

If you're thinking of going this route, Technomadia has a great series of articles you should check out:

http://www.technomadia.com/lithium/

Regards
John