RV Battery charging

To finally determine how healthy the battery is, use of a hydrometer is essential. The hydrometer measures the electrolyte fluid's specific gravity, That is the indicator of how healthy the chemical reaction is within the battery and if the battery has reached maximum SOC (State Of Charge).

A good hydrometer costs around $20 and an inexperienced user would need to follow measuring procedures for safety and accuracy. Most folks won't try it since it involves battery acid but it is the definitive measurement. Hydrometers have saved me hundreds of dollars over the years.

UPDATE:::::

So I've had this battery off the charger for afew days. Decided to try again with the 8amp charger/maintainer that I have. It seems to have taken a charge this time. Put it on the charger around 4:30ish pm last night...checked it before heading to bed for the night and it was still charging and not showing a bad battery. Checked it this morning before leaving for work and it's showing charged and still no bad battery. Might have gotten lucky with this one this time. Lesson learned on this one for sure.

Happy camping :B

I really appreciate all the help on this. Definitely a lesson learned on these type of batteries and batteries in general. Still all new to this stuff so I'll take all this advice that I can. Going to get some distilled water (which if I'm not mistaken is what you wanna put back in these) and try hooking it in parallel to a good battery in my Jeep. Worse comes to worse I'll just have to get a new one and try not to mess that one up.....

Thanks again for all the help

Running jumpers from an engine battery being charged by an alternator sometimes also works. This has to be done very carefully, with heavy cables, because it is almost like hooking up a short circuit, you can expect major sparking on the final connection, enough to explode any hydrogen gas that might be venting from either battery.

This is worked around up here in the frozen North by connecting the last connection, the (-) phase to the vehicle frame where no concentrated gas would be present. Removal of jumper cables is exactly the reverse. My own experience from personal jumper cable use and my stint as a mobile charging service is that explosions from hydrogen gas are more a myth than based on any science but it doesn't cost anything to be careful. I did find that a frozen battery with 200 amps instantly supplied may erupt in an acid geyser if the cell caps are removed.

If the OP can, or has, removed the battery for maintenance, he could take it to an auto parts retailer for load testing. Most stores now offer this service.

Pulling down a lead-acid battery too far can kill it. This can happen the first time you do it, or after several cycles of this abuse over time. A lot of RV batteries that could last 4-8 years or more die in 1-2 years from being discharged too deeply, or being "cooked" while left attached to the wrong type of charger.

That your charger-tender shows the battery to be bad could be a charger-tender issue. A battery pulled down too low has too little resistance for the charger circuitry to handle, so the charger protects itself by refusing to try. Many "booster" systems do the same, though some have a manual over-ride.

Higher-end chargers might be able to get a charge started on a really low battery, some old resonance chargers could do it, but another way to get started is to hook it up in parallel to a charged starting battery, which should be able to handle the high initial load, which might be comparable to spinning a starter motor. Running jumpers from an engine battery being charged by an alternator sometimes also works. This has to be done very carefully, with heavy cables, because it is almost like hooking up a short circuit, you can expect major sparking on the final connection, enough to explode any hydrogen gas that might be venting from either battery.

My experience, however, is that a battery reaching this stage often also has a cell shorted, or has lost a lot of usable plate area, and really should be replaced.

most times not a problem. anything being powered by battery does not care where the power is coming from battery or charger.

On the other subject on a dead battery not charging, I hooked one up to the car and ran at fast idle for 5 or so mins and gave it enough volts for the smart charge to see and start the charging program. It took over two days to completely get it up and i checked water every day adding as needed but it came back ok.

Seamutt wrote:
Question, is it okay to connect a charger directly to the batteries while they are still connected to the trailer?

Question, is it okay to connect a charger directly to the batteries while they are still connected to the trailer?

It doesn't charge any differently than you are accustomed to. Be aware that some smart chargers will not start charging a severely depleted battery. You will have to jumper it to a good battery until it starts charging.

Most batteries die of abuse and neglect, not old age. Consider this ruined battery the cost of education in the battery 101 class.

If a battery is totally discharged, some chargers wont recognize that the battery is connected. If you can find a non-smart charger, charge it for about an hour and then put back on smart charger. the battery capacity is probably permanently limited

You just can't leave a battery connected for more than a couple of weeks. There are many things still on in the RV's that will discharge your battery over time.... When a DEEP CYCLE battery gets below the 50% charge state (12.0VDC) for any extended time it is usually toast.

You need to pull the negative battery cable if you are going to leave the battery installed unattended for any length of time...

Alot of folks add disconnect switches to do this... Others have added trickle charge from either low amps trickle chargers or small solar setup to over come the parasitic drains but this sometimes creates another problem where you may overcharge the battery and boil out its fluids. This also kills the battery.

Sometimes it is just best to start out with a charged battery and then disconnect the negative battery lead. It will last a long time doing this...

I disconnected my batteries around September last year and just checked my levels the other day of my disconnected batteries. They were reading 12.4VDC since being disconnected since September...

Roy Ken