Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 13, 2025 ...

Convertor and charger

August 28, 2017, 05:12:52 pm

my 89 GV has the battery charger installed (hung) in the wet bay, and there appears to be a convertor below the bed.  Is the charger multistage, looks like it may be OEM - cant find a data plate? Convertor is wired to the 12 volt panel in the bed face.

Thanks - Phred

Quote Selected

Re: Convertor and charger

Reply #1 – August 28, 2017, 05:16:40 pm

Because those items are so often changed/replaced by prior owners, you'll probably have to post a photo before anyone can identify the unit.

Photo below: The converter/charger that was originally installed in our coach.  Don't suppose it resembles either of the units you have...

Quote Selected

Re: Convertor and charger

Reply #2 – August 28, 2017, 05:19:28 pm

Is the old converter unplugged? Seems strange previous owners would relocate new converter under the bed.

Quote Selected

Re: Convertor and charger

Reply #3 – August 28, 2017, 05:21:41 pm

Yup, you will need to determine make and model for us to give you good advice.  And, connected vs just hanging there.

Quote Selected

Re: Convertor and charger

Reply #4 – August 28, 2017, 08:42:16 pm

Wet bay unit appears connected, haven't probed for power may be dead. Underbed unit is a 9100 series 80 amp inteli power by progressive. Good news is this unit can be upgraded for $32 to a 4 stage charger. That is a bargain, unless it dies two weeks later. May just buy a straight pure sine inverter instead of the high $ inverter/charger. Coach had 3 house dual battery banks. 2 batteries were completely dead. Huge 1/2" conducter diameter cables to the 8D.

Quote Selected

Re: Convertor and charger

Reply #5 – August 28, 2017, 09:43:23 pm

Two house 8ds being charged at 1/5 capacity would be close to the max actual charging  capacity  of 90 amps with your 80 amp.

Three matching house 8'ds would take 130 range.

That being said the current units having battery temp monitoring controls of the charging process saves either over or under charging the batteries.

Most set the voltage low so in hot weather you are not damaging the batteries.

Meaning they are not being fully charged and the charging rate is lower.

Non BTS inverters come with a chart to allow you to change the parameters constantly as the battery temp changes continuously.

Charging voltage can vary from over 14 to just over 13 depending on temps in the battery bay itself.

The correct charging parameters should greatly extend the batteries life, allow quicker charging and less gen run time.

Other than that making the 80 amp unit into a progressive is nice but there are better choices Imo.

I set my non BTS freedom 25 charging voltage at 13.6 like the alternator and the solar as unless I am at high temps the batteries should not be overcharged too much.

Gen run or shore power then allows the smarter inverter/charger to correctly max the charge rate and voltage.

Killed hundreds of batteries long ago with no progressive charging and no temp compensation.

The freedom 25 had the progressive but my early unit had no BTS availability.

Plus the full sine wave inverter is like a home power source.

Quote Selected

Re: Convertor and charger

Reply #6 – August 29, 2017, 08:11:15 pm

If that converter in the wet bay hanging from the top is that silver box thing make sure that the 120 volt plug is unplugged. The 12 volt wires could remain wired to the coach, but if the 120 is active to the unit, it will overcharge the batteries as it is not a smart charger. I have changed many of them as they killed many batteries. Hopefully someone has unplugged it and when they installed the one under the bed did not take it out as it is hard to remove as the bolts holding it come down through the floor making it difficult to remove the bolts.

Quote Selected

Re: Convertor and charger

Reply #7 – August 29, 2017, 10:33:29 pm

4 group 27 House batteries (2017) are disconnected. 8d (2017) start battery has been only intermittently connected to newer convertor. Have mostly been using my 4 stage 15 amp portable to recharge. Newer 80 amp convertor under bed has only 8 gauge thhn solid wires on the 12v side to a yellow crimp ring terminal so that will be redone. Newer convertor was mounted upside down with the heat sink fins horizontal under the unit, so that will get redone. New smart 200 amp isolator without diodes and smart output 4 stage brain to modulate the newer smart convertor volts to the batteries shipped today. Shopping for a new pure sine wave inverter to operate microwave while on road trips.

Quote Selected

Re: Convertor and charger

Reply #8 – August 31, 2017, 04:20:02 pm

$26 smart 4 stage charger coversion for the progressive 9180 convertor.  Plug and play

Quote Selected

Re: Convertor and charger

Reply #9 – August 31, 2017, 07:46:29 pm

Took me a while to find this BTS chart as the std magnum inverter manual only mentions the battery temp installation and the idea it adjusts the absorbtion and float voltages based on temps.

Going to Magnum's parent corporation  Sensata's  web site the more comprehensive manual is available showing the chart.

Was not aware that the magnum turns off the float maintaining charge after four hours if the batteries have not dropped below 12.7 volts.

If they have then it turns on the float cycle for another four hours.

That way the magnum unit "does not boil the batteries dry."

So a constant float voltage that's never off may not be good for a long battery life and adding in no temp compensation to the absorb and float may lower the life even more.

equalizing ever 21 hours at 14.4  volts is something I have not heard of.  Not sure if good or bad.

Noticed my battery voltage on my dash gauges dropped to nearly 13 volts driving through Las Vegas this month.

Hmmm.  Something wrong? 

Ah.  Gen running.  Radiator in the compartment in front of wheel well.  Road temp 120? 

So at the battery the BTS reduced the nominal charge volts to correct for the temps like it was supposed to do.

My alternator and solar are both set at 13.6 at the engine battery and with the combiner the house is within .1 volts normally.

If in shore power with no alternator then the charger can finally fully charge the last amount subject to the batteries temp if below 77 degrees.

May be nit picking but i wanted the longest possible battery life with the batteries in top condition as we dry camp a lot.

Pole to pole not as important.

I would think the continued float not temp compensated would be the biggest concern.

Quote Selected

Re: Convertor and charger

Reply #10 – September 05, 2017, 04:53:31 pm

Installed smart charger in 5 min. Removed heavy oem converter and left hanger rods for future shelf. Disconnected 12v wiring and tagged for future use on each end.

Quote Selected