Have three 8d gel cell house batteries, three group 31 wet cell chassis batteries. Have a Magnum 2812 psw inverter/charger. From reading here and on other forums, understand gel cells very sensitive to charging rates. The inverter/charger is temperature compensated and is set specifically for gel cells. The alternator/voltage regulator is less capable.
Other posts have indicated one problem with gel cells in Foretravels is the temperature in the battery compartment which can get quite high and affect the proper charging rate.
Would I be better off adding a switch to the alternator/house battery connection so I could decide when to permit the alternator to charge the house batteries and when to stop the charging?
The main concern about the gell cells is not to let the charging voltage go over 14.1 Volts DC, Not heard about Foretravels haveing issues on compartment temps. Guess I need to read the SOB forums to find the skinny about our Foretravel .
Dave M
My batteries are next to buy fuel tank. I have not seen the temps in there get too hot. I charge per silver leave about 13.8-14 max.... I have gels for start and house.
Actually, the issue of high compartment temps was noted on this forum in a 2010 thread (don't know how to link this). Barry Beam installed a fan at the battery compartment vent to attempt to solve, noted temps over 100F for extended period in beautiful Texas summer. East Penn gives maximum charging voltage at 100f is 13.3, optimum is 13.0. If I stay at a campground with hookups, house batteries will typically be fully charged when I leave in the AM. Is the alternator going to then proceed to give my house batteries more than 13.3 volts?
The battery compartment on a 2002-4 (maybe a year or so after) like Barry's and our 2003 coaches is a much more confined space than in a 2001 and older, hence the higher temperatures.
If you can see your batteries without emptying the contents of a bay and removing a rearward-facing panel, you probably won't have as great a concern with temperatures :)
Michelle
The charger should act the exact same on either the generator or the post you plug into. If there is a difference in voltage causing the charger to over charge, you need your generator checked and fixed.
In the generator business, you never want to know your on the generator, due to how bright the lights are, nor how fast the clock is gaining or loosing time.
The speed / hertz / rpm stability is controled by the governor on the generator engine, all Power Tech units have a good mechanical governor and they are rated at +/- 5%, the newer units would have an electronic isochronous governor, big difference. For me, I prefer the mechanical and the less accurate as they will give less problems and get you home.
Dave M
Mike, your engine alternator is likely set to charge the cranking batteries (lead acid) and cuts out around 13.8-14.5V. Running 2 diffrent types of batteries with 2 diffrent charge rates could be a problem. Your engine alternator likely has an adjustable regulator (or one can be installed). However in the real world I doubt it is going to hurt your gel batteries. As you say the only way to isolate the house batteries from the engine alternator would be to put a disconnect in the charge line to the house batteries. The other solution is to get 3 new gel cranking batteries and have the engine alternator set to the correct charging voltage. Also remember the house battery's are along ways from the engine alternator (if they are in front of the coach) so in reality with a little voltage drop over the 30 or so feet of wire and connections your charging voltage is real close, you can check it with a meter with the engine running.
If one has an attached temperature sensor connected to the inverter/charger and or solar panels there is no problem with the proper charging as it is adjusted by the sensor/s.
That being said, the usual culprit is the engine alternator which may be putting out OVER 13.8 which is the FLOAT for gels.
When everything else fails, there's solar
Regards,
Jon Twork
On the subject of batteries and charging, I've tried to get somebody a lot smarter than me(and there are so many of you out there) to give me a tip on an intermittant voltmeter overcharging issue. On several occasions, while drive at my normal 60MPH, the dash voltmeter shows over 14V, sometimes like 16V.
I think this may be the reason my new starting batteries lasted less than 2 years. I replaced them and have an appt at MOT in a week. In the event the pegging of the voltmeter happens on my 800 mile trek, what would you recommend as a roadside stopgap measure.
I thought of just disconnecting these new engine batteries leaving the engine running, until MOT can fix the problem, ANY IDEAS?
Dick Lokar
Dick,
You alternator will be destroyed if your disconnect both battery banks-- you could isolate one bank, but not both.
First thing I would do is to clean and tighten the connections of the alternator sense wire. Probably connected to the chassis battery terminal of the battery isolator. Corrosion/resistance on the sense wire can easily cause over-voltage.
A false signal due to corrosion to the voltage regulator can easily be diagnosed as a bad voltage regulator (which it could be as well).
Brett
Dick my u270 did this.. After the short swings from 14 to 16 volts it pegged out at 17 volts for less than a 60 seconds than nothing... It was a bad voltage reg on the alternator..The rest of the trip I just used the gennie to keep the engine battery up
I'd disconnect the alternator, running the generator to keep the batteries up, until I could get the alternator checked out.
Dick, I hope this got that done when at MOT last week, and you and Pat are well on the way to the party.
Mike, recall you and I have the same model coach. My alternator got a little high on the voltage (not intermittent) and the technicians turned it down to a proper level. I then monitored that for about 1700 miles and it stayed set. I guess that is more or less a permanent fix (adjustment).
Also, I think from the location of our batteries, unless yours are different than mine, as Michelle says, we are not in sealed compartments on the engine batteries so there is some ventilation of the heat there. My house batteries are in a sealed compartment. I imagine it gets really hot....it was 105 ambient in Vernon Texas in August when we went thru there. I do have gel batteries for both house and engine.
Sustained over voltage can cause failure or damage in very expensive components like the engine/transmission computers. Contact/wiring corrosion besides causing high voltage can trigger transient voltage spikes, again shortening the lives of electronic components. An uncontrolled alternator can generate VERY high voltages.
Pierce