Battery Problem

wildmandmc · August 24, 2015

Long story short. replaced eng batterys a few months ago. other day rv would not start (DP). put a charger on. also seems coach batterys were really low on water. filled up. Got the Generator started. then when i went to start the eng. all shut off. with not enough juice to start gen or eng .

wildmandmc · August 24, 2015

Also let me add this. last week rv started up great. took got new front tires. the gauge showed battery level just below (but in the normal range) the middle line. seems it will never go up to that middle line. when i had old eng batterys it would go up past the line. new one's never did. but when i finally got rv started battery leve was way below, hit the peddle an slowly went upwards still not to middle. on board said coach battery 12.6 an eng battery 12.7

SCClockDr · August 24, 2015

If those voltages were with engine above idle they are low. I would want to look at the alternator. Does the computer throw any codes?

EDIT:

When the engine batteries were replaced was anything bypassed/altered like engine/coach battery isolation etc.?

wildmandmc · August 24, 2015

its a 2000 horizon, doesn't have that option. those numbers were with eng at idle

Chief 62 · August 24, 2015

Your alternator should be putting out about 14.7 volts at about 1500 RPM. You may have an alternator problem if you are only seeing battery voltage on your gauge. If you have a volt meter hook it up to the engine battery with the coach running and see what you are getting.

Yarome · August 24, 2015

If those voltages were with engine above idle they are low.

I agree. At idle you really want to be seeing more around 14. Have you tried getting a reading directly off your alternator?

oldjohnt · August 24, 2015

I agree with the other gents, sounds like your alternator and/or its voltage regulation circuit (internal or external I don't know?) may be bad. Id expect the engine battery shortly after start up to rise to at least the high thirteens up to fourteen plus volts, subject to RPM if the alternator and battery are basically okay.

On your comment "also seems coach batterys were really low on water."

If your Converter/Charger is the older technology noisy humming Buzz Box that acted more like a constant voltage source (say 13.4 to 13.6 volts) instead of a modern 3 or 4 stage so called "Smart Charger", if the charger is left on for extended periods it can cause overcharging and excess outgassing and boiling over of the lead/acid. KEEP BATTERY LEVELS CHECKED IF CHARGER IS ON EXTENDED TIME PERIODS.

Other thoughts are if the RV is equipped with a solid state or mechanical isolation relay that connects coach batteries to engine battery while driving so the coach batteries get charged and if the coach batteries are bad, that can really load down an alternator.

John T

Kirk W · August 24, 2015

Unless your RV is wired differently than motorhomes that I am familiar with, your chassis engine is started from the chassis battery and the generator's engine is started from the coach battery. The chassis engine can charge both since there is a relay that connects the coach batteries to the supply from the alternator, once it is up and putting out power but when the chassis engine is not running the coach and chassis 12V systems are isolated from each other. That battery gauge inside of the coach is only reading the voltage of the coach system and has no connection to the chassis battery. In addition, most of those gauges are just a cheap volt meter that actually tells you very little since they are not accurate enough to give much charge level information. You need a digital meter with at least two decimal places to know charge level based upon voltage.

Yours may be different, but all that I have seen were connected in this way.

Biker56 · August 24, 2015

You should be getting 13.8 to 14.0 at the alternator output connection. If only 12.5 to 12.7 at high idle it is time for a new alternator.

Get a VMSpc system for it to know what the output is in real time.

You did replace the chassis batteries with 2 Maintenance Free and at least 950 CCA didn't you?

You can download the software to play with Free.

Many different set ups pictures

wildmandmc · August 24, 2015

going to buy a volt meter, thanks to all who replied.

mscans · August 25, 2015

To use a volt meter on an RV requires the ability to see 4 digits as 12.34 to view the hundredths of a volt reading to properly anaylze the system. Fluke's are great, use 'em myself! HD does have some reasonably priced units also.

skp51443 · August 25, 2015

1/100 (XX.00 scale) of a volt is really needed for battery system checking as was said. Another nice feature is a 20 amp current range, that will let you monitor most anything but large motors in your slides and jacks. A 10 amp range is acceptable but you need to pay attention to your currents or you'll be looking for a difficult to replace fuse in a lot of meters, others are easy to replace but expensive.