Battery Tenders

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

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

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?

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.

Daddy Bear wrote:
So I want to take better care from the start with these two new batteries.

The first thing you need to do is get a little multi-meter so that you can read the actual voltages instead of guessing at things.

You can get a pretty good one at WalMart or Lowes etc. for $20 or less. You can get one from Harbor Freight that is adequate for about $7....or less on sale.

Edit: I see that you have that covered so......it is possible that they gave you the batteries in a discharged state and it might take several days of continuous charge to bring them up to near full.
Leave them on charge for about 3 days; then leave the battery switch ON with the charging off for 24 hours and see what the voltage is.

If this is a brand new unit and they gave you batteries that had been sitting around in a discharged state for months on end, they might be shot already.

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. I didn't leave the shore power disconnected long enough to see if the CO detector set off an alarm or not. Will do that this evening.

We are heading out on a one week trip to the Oregon coast next week and don't to deal with an alarm that I cant shut off if we are on batter power.

Bobbo wrote:
Depends on the draw. You need to get one big enough to cover all parasitic draws plus about 5 amps.

Hook the positive cable to one battery, and the negative cable to the other battery.

This what I did but I disconnected the main negative cable from the battery before installing the battery tender. When I exercise my generator or get ready for a trip, I connect the negative cable back to the battery. Has worked for me for about 2 years now.

Beemerphile1 wrote:
Tell us the brand and model number of the converter in your Grand Design and we will tell you what it does.

I don't know right off what brand the converter is. I will look through the paperwork this evening. Here's what started the whole idea that I need a battery maintainer/tender.

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.

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 ??

Kayteg1 wrote:

"Float circuit" will adjust the amperage without voltage jumps.

Highly unlikely.
Unless the resistance changes, you cannot change the current without also changing the voltage.