Dead battery already?

[Headtrustee]

It will take more than over night to fully charge a dead deep cycle battery. Charge slowly and for a long time. May take 2 - 3 days to fully charge it.

[DoubleJ73]

So...battery is charged and slideout is functioning properly! Guess I just need to make sure that I recharge the battery every so often to keep it in good working condition. Thank you all for responding. This is a great site and as a newbie I am learning something new everyday!

[papachaz57]

my TT says to plug in the shore line for at least 8 hours a month to keep the battery charged up. one of the things mentioned above was the battery fully charged when you disconnected it? it does make a difference if it is or not.
good luck!

[Shadowcatche]

You need to monitor the battery! A volt meter at the very least to make sure it is fully charged Car and Deep Cycle Battery FAQ, Battery Manufacturers and Brand Names List, and

[RedRocket]

Originally Posted by wa8yxm

OTHER RV's have modern 3-stage converters, and with these ... Well first they charge the battery much faster, they can keep up with radio and other "Clean power" devices no problem... And once the battery is full.. They shut down to a "Maintenance mode" (Float charge) where basically no current flows in the battery.

The result is very long battery life.

Hopefully you or someone else knowledgeable on the subject are still monitoring this thread...

Let's say I have purchased a 3 stage charger separate from my RV where I will remove the batteries from the RV for about 4 months during the winter.

Should I be leaving the 3 stage charger powered up and connected to the battery for the entire 4 months?

Also, can I hook both batteries in parallel and use a single 3 stage charger to maintain both batteries during this 4 month duration?

Thank you.

[GaryKD]

Hi RedRocket,
You can leave the 3 stage charger connected to the batteries. You can connect the 12 VDC batteries in parallel and use one charger to maintain both batteries.

[GaryKD]

Hi papachaz57,
The battery should be fully charged before disconnecting the charger. While not a death sentence if not fully charged, if one continues to do this over time the battery will not regain its' full capacity.

[Shadowcatche]

GaryKD You can not tie two batteries in parallel unless they are identical AH, age, manufacturer. Otherwise both batteries take on the characteristic of the weaker battery (over simplified). I have three batteries in my garage, lawn tractor, Saab Sonett I am restoring, and an AGM that is faulty but still has some value. I regularly recharge (weekly) the two lead acid and every couple of months the AGM (much lower self discharge).
To help with understanding of what a marine starting battery is
" Marine batteries are usually a "hybrid", and fall between the starting and deep-cycle batteries, though a few (Rolls-Surrette and Concorde, for example) are true deep cycle. In the hybrid, the plates may be composed of Lead sponge, but it is coarser and heavier than that used in starting batteries. It is often hard to tell what you are getting in a "marine" battery, but most are a hybrid. Starting batteries are usually rated at "CCA", or cold cranking amps, or "MCA", Marine cranking amps - the same as "CA". Any battery with the capacity shown in CA or MCA may or may not be a true deep-cycle battery. It is sometimes hard to tell, as the term deep cycle is often overused. CA and MCA ratings are at 32 degrees F, while CCA is at zero degree F. Unfortunately, the only positive way to tell with some batteries is to buy one and cut it open - not much of an option." http://www.windsun.com/Batteries/Bat...ery%20Charging

[BryanL]

re: "You can not tie two batteries in parallel unless they are identical AH, age, manufacturer. Otherwise both batteries take on the characteristic of the weaker battery (over simplified)" -- There are factors that need to be considered here. All lead acid batteries have nearly the same voltage versus state of charge profile and old batteries are mainly distinguished by having a higher internal impedance and less capacity. That means that mismatched lead acid batteries just put more of the work on the bigger and newer battery - not that they take on the "characteristic of the weaker" - this is why most RV's will have both the house and engine batteries connected in parallel at least while on the road with no undue consequence.

That is, connecting two of the same type and voltage lead acid battery should present no significant problems. The 'better' one will undertake a proportionate share of the work so it may age a bit faster but otherwise there will be no calamity.

As for the "true deep cycle" and "hybrid" and 'thick plates' whatnot - it is best IMHO to stick to what you can measure that is pertinent to your needs and to those batteries commonly available for RV use. The NAWS FAQ comment on having to 'cut it open' also notes that for batteries in this context, there is very little difference in construction (they all have thin plates, for instance).

As for the CCA and such measures, I see many RVers who like to use the coffee pot and microwave for breakfast in the morning. That is a CCA type concern. The best comment I have seen on this is at the site where Battery Performance Characteristics - How to specify and test a battery is- that suggests that maybe a 20% headroom might cover the distance between a 'deep cycle' and 'SLI' targeted battery. That 20% thing is the sort of variance you can get in lead acid batteries from factors such as temperature, use profile, age, and cycle to cycle variation.

Another point is that of battery storage. A smart modern charger should be no problem leaving connected for several months. It may even have a storage mode which would make it a very good option. Battery storage needs a device that will assure a full charge without overcharging and will apply a sulfation inhibiting technique. Some of the better RV converters do this. Float or trickle chargers don't.

[RedRocket]

Originally Posted by Shadowcatche

GaryKD You can not tie two batteries in parallel unless they are identical AH, age, manufacturer. Otherwise both batteries take on the characteristic of the weaker battery (over simplified).

Thank you all for a much better understanding. GaryKD did answer what I was looking for and in my case, the two batteries to be in parallel would be identical, purchased at the same time with as close to identical manufacturing dates. But thank you for adding that extra piece of information.

[trackman]

Always have a charged battery(tested by you)before venturing off to the unknown

[JohnBoyToo]

You may be experiencing what I suspect I am too...
maybe your tow vehicle is not recharging your coach battery ....

I am on a mission tomorrow to test that theory !