Utilizing the correct charger and following proper charging methods is one of the primary keys to enhancing battery service life and performance.
Although an RV manufacturer will generally choose a combination of components (batteries, charge controller, converter) that works together to properly charge the coach battery power supply, occasionally something goes wrong. Perhaps a mismatch has occurred, or one component is approaching failure or has fallen below specs.
Avoid problems by watching for signs of battery charging issues and having the battery and charging system tested regularly.
Signs of Improper Battery Charging
According to Interstate, there are a number of signs that an RV battery may not be charging properly, including
- Batteries are going dry and frequently need additional distilled water
- Batteries become very warm during charging
- Batteries seem to “run down” very quickly
- Battery service life does not meet expectations.
Testing RV Battery Charging
A good battery charger (such as a “smart charger”) is a good investment, because it can be set to provide optimal charging cycles for the battery being charged.
Lead-acid batteries should be charged at a rate of C/10, where C is the battery’s Capacity in Amp-Hours (this specification can be found on the battery). A battery with a 190Ah rating should not be charged in excess of 19A. A 10A charger would thus be acceptable. A battery service center can determine if an overcharge condition exists.
A properly charged12V battery will have a hydrometer (specific gravity) reading of of about 1.260 to 1.275 or a voltage reading of 12.66V to 12.75V. Immediately after charging, a battery’s voltage reading may reflect a “surface charge” rather than the true charge. To clear this, apply a small load (10 or 15A, such as a few lights) for two or three minutes, then allow the battery to rest for one minute. The subsequent voltage test will give a better measure of the true state of charge. The owner may perform these tests with a good quality digital multimeter.
To check compatibility between batteries and charging system, check and/or test the battery or batteries every two or three weeks.
- If batteries require additional water the charger may be overheating and/or overcharging them.
- If batteries are not meeting the performance expected, the charger may be undercharging them.
- If the batteries are low-maintenance, test with a multimeter as above.
Battery Charging Conditions to Avoid
Proper charging with a charger designed or set for the specific battery is essential to battery performance and service life. Any of the following is to be avoided:
- Excessively fast charging
- Excessive time between use and recharging
- A consistent low state of charge.
The charging conditions listed above will reduce the performance and service life of the battery.
Interstate recommends having the batteries professionally tested by a dealer every six months to determine if battery function is good, bad (imminent failure), or marginal (pre-failure). Other manufacturers may recommend a different test schedule.