Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 15, 2025 ...

Discharged chassis batteries

September 30, 2016, 06:59:54 pm

I was about to flush distilled water through my cooling system when the engine would not start.  It tried to turn over, but obviously not enough battery power.  I checked the voltage and it was just under 11 V, by my multi meter and portable charger.
The RV was at the A/C shop for 5 days last week without shore power.  It started without problems last Friday, when I drove it home.  It has been connected to 30A shore power since then with the boost switch on.  The batteries were purchased in July and are 720 CCA Optima Red Tops.  Even with the house batteries, no luck.  We have had the roof air on all day, while Kristi was working on the inside.
Any ideas?

Quote Selected

Re: Discharged chassis batteries

Reply #1 – September 30, 2016, 07:04:11 pm

Have you verified that house battery bank is being charged (meaning 13.2+ VDC).

If so, the boost switch is NOT working.  Were it working both banks would read the same.

I am not big proponent of the boost switch as a means of keeping the chassis batteries charged.  Too many other/better alternatives including low amp smart chargers for chassis battery maintenance and the "thief" kind of devices such as Xantrex Echo charger that charge chassis battery when house bank above XX volts.

Quote Selected

Re: Discharged chassis batteries

Reply #2 – September 30, 2016, 07:35:32 pm

My house batteries are at 13.75V, going my the panel.  It is very possible that the boost switch isn't working, but would that account for the chassis batteries being drawn down?  My understanding is that an on board converter will supply the 12V systems while plugged in.  Could the converter be the issue?

Quote Selected

Re: Discharged chassis batteries

Reply #3 – September 30, 2016, 07:37:34 pm

The charger on the inverter only charges the house batteries

Quote Selected

Re: Discharged chassis batteries

Reply #4 – September 30, 2016, 08:42:27 pm

Correct.  OE was to ONLY charge the house battery bank from the inverter/charger.

Quote Selected

Re: Discharged chassis batteries

Reply #5 – October 01, 2016, 12:09:02 am

I thought the chassis batteries were also charged if the booster switch was on.  Any ideas on how the chassis batteries might have been drawn down while plugged in (headlights were off).

Quote Selected

Re: Discharged chassis batteries

Reply #6 – October 01, 2016, 12:12:40 am

Boost solenoid is faulty. Take it apart and fix it-simple and cheap. A much better idea is put a small 70watt solar panel on roof permanently and wire it down to engine batteries and you will never have a problem with them again.
JohnH

Quote Selected

Re: Discharged chassis batteries

Reply #7 – October 01, 2016, 12:24:35 am

Or, buy a  battery combiner, 3 wire hookup.  BLUE SEA SYSTEMS Starting Isolation (SI) Dual Sensing Automatic Charging...

Quote Selected

Re: Discharged chassis batteries

Reply #8 – October 01, 2016, 11:31:17 am

I find a diode-based device like Trik L Start to be the one that does the job for us. 

We have installed two brands of relay-based devices from Magnum and Blue Sea that combine when one battery bank is being charged at a high enough voltage setting, and disconnect when voltage drops to another set point.  We noticed issues when battery bank temperature is high, like around 100 degrees, our battery charge profile will lower charge voltage to protect GEL battery, which can be too low to trigger this type of device to combine banks.  One of the two that we tested, even had adjustable set points, but it still was a problem.

Sure diode-based charge start battery bank at about 8/10ths lower, and relay-based do not lower start voltage, the other issues just made me put the relay-based aside and switch back to the trusty Trik-L-Start.  We even found issues with relay-based when starting engine caused voltages to drop to about 10-volts.  The Blue-Sea tries to compensate by running a wire to the start circuit so it will not trigger low voltage problems.

So to keep start battery bank charged, this one gets our vote:
Ultra TRIK-L-START Starting Battery Charger/Maintainer 

Quote Selected

Re: Discharged chassis batteries

Reply #9 – October 02, 2016, 06:45:57 pm

15 amp  AMP-L Start start will guarantee chassis batteries stay charged whether on shore power or generator. about $65. I mounted mine inside at base of bed to keep it away from engine heat.

AMP-L-START Starting Battery Charger/Maintainer - Overview Page

Quote Selected