Battery Tenders

[Daddy_Bear]

I have two new RV Batteries and want to keep them completely charged. Stupid question I know, but here goes. What size battery tender do I need to get and can I just hook it to one of the batteries in order to charge both of them. They are wired together. Does anyone have recommendations?

Thanks

[MEXICOWANDERER]

WFCO. Makes me grin...

In two years connected without interruption, original length 6 gauge wires connected directly to the Lifeline, it has never gone to float.

But it can jump to the highest step. Unfortunately that isn't 14.4 volts - it's 14.75

Some kind of piece of equipment that thing is.

But it makes an excellent high amperage fixed voltage power supply.

Don't forget the MEGAWATT. 40 amps worth of float when adjusted to 13.2 $65.00
Makes Battery Minders look foolish dollars per amp.

[westend]

Three things you should have with your new batteries: A disconnect switch so that when in storage you are not powering any alarms or other parasitic draws, a meter to accurately monitor voltage in the 12V system, and a hydrometer to see what is happening, chemically, inside the batteries. The electrolyte should be checked with the hydrometer during the first 10 or so charge cycles to arrive at a base line Specific Gravity. That measurement will be referenced for the life of your batteries.

If you are one of those that doesn't have time to do the steps to insure correct battery health ("they should be OK...."), no harm, no foul. You will just be buying new batteries sooner rather than later.

BTW, the WFCO chargers (various models) are known to have problems with correct staging/output and may lead to early battery demise. I'd suggest you shop for another converter to be used concurrently with your 12V system. You can pull the WFCO, let it remain but unpowered, or use it too.

FWIW, I have a Progressive Dynamics converter that is 45 yrs. old and works perfectly. I guess nothing more needs to be said.

[Sam_Spade]

Daddy Bear wrote:
So, I think the batteries were discharged when we brought it home.

It is dangerous to ASSume things based on only one tiny piece of evidence.

You STILL need to check the voltage after they have been resting for a while.....that is, not charging from any source.

[beemerphile1]

Daddy Bear wrote:
I unplugged from shore power yesterday and no alarms this am. So, I think the batteries were discharged when we brought it home.

It has a WF9875 (75amp) converter. Does anyone have experience with this particular model...good/bad??

It is adequate, not super, but adequate for the average owner. It should keep your system charged fine.

[Daddy_Bear]

I unplugged from shore power yesterday and no alarms this am. So, I think the batteries were discharged when we brought it home.

It has a WF9875 (75amp) converter. Does anyone have experience with this particular model...good/bad??

[SCVJeff]

MEXICOWANDERER wrote:
Amperage is affected slightly by temperature of the battery. In a 30F - 60F day temp swing amperage will not remain constant merely predictable.

Check your PM

[Daddy_Bear]

Beemerphile1 wrote:
Maybe you left the dealer with batteries that were already discharged.

The CO detector did not drain the battery overnight. Did you accidentally pull the breakaway pin?


Not all converters are created equal. That is why you need to research what you have.

Does your tow vehicle charge the trailer batteries as you drive?

Leaving the dealer with discharged batteries is a possibility. The whole time we were there the TH was on shore power. I don't expect that the CO detector drew the batteries down. The fuse that controls the charge line on my truck is blown, so no it did not charge during the tow home.

It has bee on shore power now for 5 days. Im gonna disconnect from shore power this evening and check it in the am to see if it does it again.

[Sam_Spade]

Bobbo wrote:

While my original statement is, to you, not true because you can attach to the wrong terminals, your statement is NEVER true.

Sorry my post was phrased poorly.

In a parallel arrangement, you can follow your statement without qualification because connecting to either battery will work.

In a series arrangement your statement needs a bit of qualification......because some people have NO CLUE about electricity.

[MEXICOWANDERER]

Amperage is affected slightly by temperature of the battery. In a 30F - 60F day temp swing amperage will not remain constant merely predictable.

[beemerphile1]

Daddy Bear wrote:

We brought the new TH home last weekend. supposedly equipped with two new RV batteries. When I parked it in our yard and disconnected it from the tk it was late and we went to bed. The next am I went out to find the CO alarm was going off and would not reset. After looking up the flashing/beeping code it said the alarm was due to LOW Voltage. I hooked up shore power and the alarm silenced itself. The TH has been attached to shore power since. The TH does have a battery disconnect switch, but it was in the ON position.

Why would two brand new RV batteries not have enough voltage to run a CO detector? All of our other fifth wheel and trailers have had converters that was suppose to keep the batteries at full charge, but I have found over the years that that's not always the case. So I want to take better care from the start with these two new batteries.

Maybe you left the dealer with batteries that were already discharged.

The CO detector did not drain the battery overnight. Did you accidentally pull the breakaway pin?

Not all converters are created equal. That is why you need to research what you have.

Does your tow vehicle charge the trailer batteries as you drive?

[coolbreeze01]

The alarm may need a new backup battery. 9V or AA's.

[Daddy_Bear]

There was nothing else on in the trailer Fridge was not On either.

[red31]

Daddy Bear wrote:


Why would two brand new RV batteries not have enough voltage to run a CO detector?

what other things are on like the fridge?

[Bobbo]

Sam Spade wrote:

Bobbo wrote:
Only, you hook them to the terminals that are NOT wired together.

My 2007 Winnebago came with a cheap Magnatek 7345 single stage converter that always put out about 13.5 volts. It was a battery killer. After about 3 years, I junked it and bought a good 3 stage converter, a PD4655V.

You added information. The original statement by itself is NOT true because you can attach to the wrong terminals.

What brand is the 4655 ? And was it "plug and play" or was some modification necessary to get a good fit ??

While my original statement is, to you, not true because you can attach to the wrong terminals, your statement is NEVER true. You said attaching to the terminals of different batteries could "only" be done if the batteries were in parallel. You actually used the word "only." In parallel batteries, it is optional. In series batteries, it is mandatory.

Sam Spade wrote:
The advice of connect one lead to one battery and the other lead to the other battery only works in a parallel arrangement.

I prefer the term "clarified my post" to "added information." While I thought it was obvious which posts you had to connect to, some here must have difficulty with battery concepts. They must have thought it was feasible to connect to posts that are directly connected to each other with a 2/0 gauge wire.

As is specified in the quote above, I upgraded to a PD4655V.

Google it if you want specifics.

Daddy Bear wrote:
Here's another tidbit of info. I checked the voltage last evening once with the shore power connected and got 14 volts and once w/O shore power connected and they bounced b/t 13 & 14 volts.

There is a phenomenon known as "surface charge." If you charge batteries, then remove the charger, they appear to keep the much higher charging voltage for a while. You can put a temporary load, like an incandescent light on it, or just wait a day or two for the surface charge to dissipate.