Charging deep cycle marine/rv batteries w/a battery tender international

Rgrigutis · 12-04-2015, 05:21 PM

Just brought home my 323 lkts. Batteries are dead. One at 9.7 v and the other at 12.1. Is it ok to charge these w/a battery tender 12v and 1.25 amps? Charge my motorcycles with this charger. Not sure about deep cycle. If not ok then I have a 2-10 amp charger would that be better. New to rvs and deep cycle battery is. Battery is exile marine/rv 24 mdcst. Thanks in advance guys

ALJO · 12-04-2015, 05:46 PM

The 1.25 amp is more like a maintainer. Use the 10 amp for recharge first.

Ela1948 · 12-04-2015, 05:49 PM

You didn't say where the batteries were and the situation that caused the batteries to be in such a low voltage condition. I would start by putting each battery on your 10 amp charger individually for 12 hours each. Giving each battery a load test after they have been charged. Batteries with voltages as low as 9.7 volts are questionable if they will hold a charge if recharged. If the batteries prove to still be serviceable, you have the option to either keep the batteries charged with your RV assuming that you have a multistage converter. The other way is keep them on a tender AFTER they have been fully charged.

**Mustang65** · 12-04-2015, 06:57 PM

Like Ela1948 said... charge them individually.

Mark the battery that had the lower voltage, for future reference. When you finish charging the first battery, the voltage should be about 13.2 volts. Disconnect the battery and let it rest (no load or charge) for either 24 or 48 hours (I prefer 48 hours), then test its voltage, it should be at 12.6 or higher. Using the same charger, do the same for the other battery and take its voltage reading at the end of the rest period. The voltages should be within .1 or .2 Volts of each other at the end of the rest period. If they are both about the same voltage, I would then put them both on the charger and top them off before putting them in the TT. Make sure you check the water level on the batteries, especially the lower voltage one. I would keep a close watch on them for a week or 2.

The best way (most accurate) to know if your batteries are OK, would be to go to an auto parts store and pick up a Specific Gravity tester, and after the rest period, test each cell against the mfr specifications... this is the best way to see if the battery is good. You will see if there are any damaged cells.

If they are OK, fully charged and are "Deep Cycle" Flooded Lead Acid battery types, see if there is any way that you can EQUALIZE each battery. Equalizing is actually over charging a battery (between 15 and 15.5 volts) for a specific amount of time as determined by the mfr. It reverses the build up of negative chemical effects like stratification (acid is greater at the bottom of the battery than at the top of the battery). It also removes sulfate crystals that might have built up on the plates.. (which reduces the battery capacity)

Now for the bad news.... If one of the batteries is no longer usable and you are going to replace it, you need to purchase 2 new batteries. If you replace one, the old one that was discharged will eventually bring the new battery down to its level and its life will be about the same as the old battery.

Lastly, keep checking the water levels while charging (safety glasses) and feel if the battery is getting hot or starts to boil, if so stop the charging.

Good Luck!!

Don

Rgrigutis · 12-05-2015, 06:50 AM

Thanks for the replies. They're sealed batteries. Brand new in my new fiver. Just picked it up. Had it on the tender and voltages this morn are 10.4 and 12.3. I'll hook them up one at a time to 10 amps

Rgrigutis · 12-05-2015, 07:11 AM

Check that. The batteries are not sealed. I'll have to get a hydrometer

Ela1948 · 12-05-2015, 07:11 AM

If you have a new fifth wheel, it most certainly has a multistage converter in it. If you can hook up your fiver to shore power, you don't to manage your voltage as much. The smart chargers today do a very good job of maintaining your batteries.
If they are brand new and the trailer is new, why were the batteries dead??

Rgrigutis · 12-05-2015, 08:05 AM

Batteries were installed 2 months ago. Don't know if they were charged prior. Calling salesman now

SmokerBill · 12-05-2015, 10:15 AM

I would check all the connections to the batteries, and the connections of the negative wire to frame, and positive wire to converter. While you're at it, I'd also check all the connections on the converter for tightness, since new RVs are made in such a hurry. Many of us find that many of the electrical connections are loose from the factory.

A loose connection would negatively affect (in a bad way, haha) the charging of the batteries.

Ela1948 · 12-05-2015, 11:03 AM

Quote:

Originally Posted by Rgrigutis

Batteries were installed 2 months ago. Don't know if they were charged prior. Calling salesman now

If the fiver wasn't hooked up to shore power for those two month's, the batteries would surely be drastically discharged. There is enough electronics and sensors in your rig to discharge them in 2 weeks. If you can't leave your rig hooked up to shore power constantly, you need to put in.a disconnect switch inline or disconnect your batteries when it's not being used.

Rgrigutis · 12-08-2015, 02:40 PM

Ok one came up to 13.3 v. The others stalled at 11.7. These are exide marine/rv batteries you can get at tractor supply for 70.00. They give cold cranking and other stats for a typical starter battery. Camping world says that they install these exclusively. Taking the trailer in for some work and am going to make a strong case for free replacement, only I don't want the exide Marin's/rv battery. Any suggestions for a replacement battery that won't break the bank and is a true deep cycle? When I store the trailer and turn off the red battery disconnect how long will a true deep cycle last? Thanks, rick

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