Maybe a dumb question

[smitty1020]

Can you or is it safe to charge your house battery's while on shore power. Seems not to be charging as quick. RV park for a month

[Judge]

Yes….

If you have a quality Converter / Charger or Inverter / Charger, they will be properly maintained from a voltage perspective.

However, if they are wet batteries and not AGM, you need to check the acid level occasionally and add distilled - deionized water as necessary. If the cells dry out, they will be permanently damaged.

Now if your batteries are not holding a charge, it could be time to replace them. Especially if they are the original factory batteries, which are cheap and usually not maintained properly by the dealers.

[EA37TS]

I will add that if the batteries are good and not being adequately charged while on shore power you could have a converter/charger issue.

You shouldn’t have to use a separate battery charger when connected to shore power. If you must then something’s wrong.

[16ACE27]

Originally Posted by smitty1020

Can you or is it safe to charge your house battery's while on shore power. Seems not to be charging as quick. RV park for a month

When on SP your house battery is automatically charged by the converter IF the battery disconnect is shut (USE/STORE in USE). You should not need to use an external battery charger.

Can you be more specific when you say "Seems not to be charging as quick."? How are you measuring the state of charge?

[Bob Denman]

https://www.thorforums.com/forums/at...1&d=1652192218

[smitty1020]

I just had 2 new batteries, transfer switch, inverter and converter replaced. 3 weeks ago. sitting here stationary for 3 weeks, the batteries were at 13.6 now at 12.5. shouldn't the charging system try to keep up and maintain 13.6 + -. when on a trip after 5 or 6 hours the batteries are charged.

[lwmcguir]

Originally Posted by smitty1020

I just had 2 new batteries, transfer switch, inverter and converter replaced. 3 weeks ago. sitting here stationary for 3 weeks, the batteries were at 13.6 now at 12.5. shouldn't the charging system try to keep up and maintain 13.6 + -. when on a trip after 5 or 6 hours the batteries are charged.

Use your VOM and check voltage across whatever type battery controller you have

Same time you will determine what the voltage from the charger is providing

[bevedfelker]

I don't want to impute anyone's intellegence here, but when answering any questions about house battery charging, it bears constant repeating -- the USE/STORE switch must be in USE for the house batteries to be charged by the converter.

When on shore power and you don't have the USE/STORE in USE you get a false sense of security because all the RV 110V AC and 12 VDC circuits get power from the converter. Everything will be working in the RV from the converter power. But what WON'T be happening is the house batteries will not be charging.

[16ACE27]

Originally Posted by smitty1020

I just had 2 new batteries, transfer switch, inverter and converter replaced. 3 weeks ago. sitting here stationary for 3 weeks, the batteries were at 13.6 now at 12.5. shouldn't the charging system try to keep up and maintain 13.6 + -. when on a trip after 5 or 6 hours the batteries are charged.

Not necessarily 13.6 VDC but certainly 13.1 VDC.
It sounds like the converter is supplying your DC loads but is not connected to the house batteries. You need to get the DC Voltmeter out and check voltage across:
The reverse polarity fuses in the DC load center/fuse panel.
The battery disconnect latching relay
The 50 Amp DC breaker near your house batteries.

Also double check the battery wiring to insure it is wired correctly.

Are you in the Saint Petersburg area?
I'll be in Largo Monday and could stop by for another set of eyes on it if you don't have it figured out by then. PM me if that sounds like an option you want to pursue.

[ScottyB410]

Well,

An everyday lead acid battery, whether deep cycle or starting, has a nominal voltage per cell of ~2.1 VDC. Therefore, a fully charged 6 cell battery will show a voltage of ~12.6 volts. Period.
although certain batteries might show 12.7 or 12.8, the basic chemistry of the battery does not allow it to rise beyond that.

If you are looking at your volt meter, and it is showing 13.1 or 13.6 (or some at 14.2), you are looking at the voltage being output by the charger, not the voltage held in the battery. To charge a lead acid battery, the charger will output between 2.25 for fast charge then reduce to 13.1-13.5 (know as a float charge)

[Judge]

This ^^^^^

Give that man a cigar for a very accurate and thorough answer.

[ScottyB410]

I'll take the Cigar
Edit to the original Post:
Fast charge will usually sit around 2.35 V per/cell then reduce to 2.25 for float.

[Beau388]

Originally Posted by ScottyB410

Well,

An everyday lead acid battery, whether deep cycle or starting, has a nominal voltage per cell of ~2.1 VDC. Therefore, a fully charged 6 cell battery will show a voltage of ~12.6 volts. Period.
although certain batteries might show 12.7 or 12.8, the basic chemistry of the battery does not allow it to rise beyond that.

If you are looking at your volt meter, and it is showing 13.1 or 13.6 (or some at 14.2), you are looking at the voltage being output by the charger, not the voltage held in the battery. To charge a lead acid battery, the charger will output between 2.25 for fast charge then reduce to 13.1-13.5 (know as a float charge)

If you are checking the battery's state of charge, you need to be aware of a physical condition known as a surface charge. During the last minutes of the absorptive stage of charging, the conversion of lead sulfate to lead and lead dioxide is a very slow process. During this process, hydrogen is absorbed into the sulfuric acid. This process causes the battery to act like a big capacitor and take a non-chemical charge. This effect will show a voltage of 12.8 to 13.2 volts depending on the temperature of the converter or battery temperature probe if one is installed. This charge will gradually dissipate over several hours or it can be used by turning on the lights for a couple minutes. If the batteries were discharged and recharged to about 90% of capacity, removing the charger and immediately checking the voltage will read above 12.7 volts. Thus the battery voltage should only be checked after the battery has rested for several hours after charging (24 hours is the recommended resting time) or after the surface charge is drawn off the batteries by using some electrical device for several minutes with the charger removed.

[ScottyB410]

Hey Beau388

Completely Agree.

This is what us engineers call “Fantom Voltage”. It is a function of charge that travels outside the realm of the “Resting State EMF” of a lead acid battery. Basically, it’s a ghost that once exposed to a load will dissipate very quickly.

The only true way to determine the State of Charge (SOC) of a lead acid battery is to measure the Specific Gravity (SG) using a hygrometer. A hydrometer is a simple gauge based on the principles of Archimedes.

Basically, it measures the buoyancy of an object in the liquid in which it floats.
Why is this useful with batteries? Well, as you discharge a lead acid battery, water is produced and dilutes the electrolyte. Consequently, the specific gravity of the liquid (electrolyte) drops (a discharge battery will usually show a SG of ~1.17). However, as you charge a lead acid battery, the specific gravity will rise (a full charged battery will usually show a SG of ~1.250).

Great conversation BTW.
This is a great thread.

[lwmcguir]

All of us Gray Beards had more than one hydrometer on the work bench

All of my batteries are now sealed so the hydrometers gather dust

Certainly did work well but now a load tester and quality Volt meter have taken their place

[ScottyB410]

LOL, oh trust me. Lots of grey here for sure.
I am enjoying this thread.

[Mablunk]

Where might this USE STORE SWITCH be located?

[16ACE27]

Originally Posted by Mablunk

Where might this USE STORE SWITCH be located?

Generally, with the other switches near the entry door that control inside lights, awning, outside light, and steps. Different RVs may have it in different places and call it different things like MAIN POWER, BATTERY DISCONNECT.

[Beau388]

I have two banks of three switches each on the left side of the entry well. Bottom row left to right is use/store, patio awning in/out, entry step disengage. The top row left to right is interior lights (main room only), patio awning lights, and exterior courtesy light (door light). All are clearly labeled.