View Full Version : Hope someone can help Electrical Issue

02-06-2010, 12:56 AM
My 99 8362 has a 1000 watt inverter charger made by heart Int. I want too increase my battery capacity. Add 4 golf cart battiers to the two deep cycles already in. Can I add wattage by adding just an inverter (much cheaper than a new inverter/charger) Also will mixing the battiers cause a problem. I could still add capacity with just the 4 cart batteirs. Can anyone advise me about the electrical issues that will come up.

Chuck v
02-06-2010, 02:22 PM

Lead acid batteries don't behave very well when connected in parallel, particularly if they are different sizes or even different manufacturing dates/condition if they are the same size and brand. The issue comes from the characteristic of the lead acid cell being a very low impedance when fully charged but a higher impedance when discharged. This causes a discharged battery to not charge very well when in parallel, but the least charged cells charge first when all are in series.

If you look at electric vehicle arrangements, you will see that the batteries are almost always in series, and the operating voltages are often 48 volts or higher. When I had my cabin running on solar power, it was a 24 volt system with very large cells all in series.

My coach uses 6 volt golf cart style batteries in a series/parallel combination to power the 2000 watt inverter -- not the ideal, but a workable solution that uses commonly available battery sizes. Just remember that you should replace all the batteries at the same time and with the same manufacturer, size and if possible date code.


02-06-2010, 07:46 PM
Dexter, I recommend that you read this article that is very informative about 12 volt batteries at the bottom of this link:


Chuck v
02-06-2010, 08:07 PM

Very good article! As you can see from the table entry for the L-16 batteries (which were the ones that were in my cabin's solar system) the size and weight of these pretty much precludes them from use in a motor coach. Another factor against the L-16 for RV use is that they are meant for "stationary" applications, so the lead formulations/compounds used in making the plates are not as rugged as those chosen for vehicle uses. Under vibration, there can be sloughing and the particles that fall to the bottom of the cell can short the electrodes...


02-06-2010, 08:52 PM
Hi Dexter, It generally is not a good idea to mix 2 different types of batteries. Are your current batteries 12V or 6V? You may be able to get by if you add 4 6V batteries to your existing 6V batteries, however the older batteries will not last long and will probably cause trouble.

I assume you are wanting to increase inverter output? Or, are you trying to get the inverter running longer on the current you are drawing presently?

02-06-2010, 10:07 PM
What I want to Achive is more amp Hrs And more wattage from the inverter/ charger. I am using 2 12volt deepcycle battiers at present I don,t know there age Came with home.

Thanks for all the advice so far. I read the article Ron Suggested cover to cover. Really good information About battires and monitoring. I need to know more about mixing Charger/Inverters with chargers and inverters as separate units.

David Bott
02-09-2010, 08:37 PM

"What I want to Achive is more amp Hrs And more wattage from the inverter/ charger."

You can not achieve more wattage, if you have a 1000 watt inverter, the max you will have is 1000 watts. If you want more wattage, you need to replace the inverter, so please keep that in mind. The batteries will determine the run time you will have. based on the amp draw.

02-09-2010, 10:53 PM
Thanks David I was afraid that was the way it was.

02-21-2010, 08:37 AM
additional capacity 'could' be added if you choose to add an additional bank of battery's and inverter. The inverters output would have to be dedicated, that is run separate outlets in the coach that come off the new inverter only. The two systems would not be connected in any way but increase the headache of troubleshooting if problems arise.

maybe there are some EE's onboard that could explain if the use of 1:1 transformers could be used to transfer the energy from a #2 inverter to the #1 electrical circuit (factory installed 120v circuit).


Chuck v
02-21-2010, 11:37 AM

Inverters are not candidates for being operated in tandem unless they are designed to be 'synchronized' so their output waveforms are perfectly overlapped and in-phase and at the precise same frequency. I would not expect many of the consumer RV type inverters or inverter/changers to have this level of sophistication. Transformer isolaton does nothing for solving the issues of different output frequency/wave-shape/phase characteristics between to converters of even the same model and rating, and all of these parameters will be effected slightly by load, temperature, battery condition, etc.

Dexter, your best bet if you must have a larger capacity for your inverter is to replace the current one with a 2000 watt model and power it by a larger battery bank (if room and money allow...)

I once was involved with having a Prevost coach built to our company requirements for the commercial display of advanced telecommunications/video processing equipment. It toured the entire US showcasing our products and systems for IPTV to small telephone companies. It did have two 2000 watt inverters that were synchronized to operated in tandem, plus a very nice, quiet turbo diesel generator that was housed in a foamed lead lined sound deadening enclosure. We could run all our gear and several of the basement air conditioners without the shore power connected...

Even without all our special gear installed (3 full racks of equipment and lots of video/computer equipment...) that coach ran abut 4 times the cost of my Tour Master, and that coach was built a decade earlier than my 2007 TM! It was very nice, but I don't expect to ever have one personally from purely a cost standpoint.


David Bott
02-21-2010, 12:10 PM
Hey Chuck...

I think you missed the part where he said " The inverters output would have to be dedicated, that is run separate outlets in the coach..."


Chuck v
02-21-2010, 12:37 PM

Sorry if I was not clear...yes, I saw the part about running it as a separate system of dedicated outlets with out ANY connection to other AC outlets (which would require a separate additional transfer switch to allow these dedicated outlets of the added inverter to be active when on shore power.)

I was specifically replying in my post above to the notion/question of possibly using a passive transformer for 'summing' the output of #1 and #2 inverters as 72chevy4x4 described it. My rambling answer was why it was not likely without specially built equipment...and a simple transformer was not the means to that end.

As always, if GS would publish the schematics for our coaches (even generic ones if they do not want to commit to disclosing variations per coach VIN number...) we could discuss these questions in a more detailed and helpful way. That Prevost coach my prior company had Vantare' build out had complete CAD drawings of all the AC wiring, the DC wiring and fiber optic cabling that was installed, along with about three file drawers of other documentation... I have nothing like that for my Tour Master T-40C :(


02-21-2010, 07:37 PM
it's been awhile since I took field theory, but the phase's may/would be out so I get what you are saying.

Chuck, question about the fancy build you mentioned the diesel genset being treated to sound deadening materials. Can you elaborate and also describe if the generator was in the forward postiion as is common w/ a diesel pusher or located elsewhere?

Chuck v
02-22-2010, 01:03 AM

Always a risk to trust too much to my memory from a decade ago, so I looked it up! Good thing I went back and referenced the real data, as the inverters were twice as large as I had recalled them to be...

The Prevost H3-45 coach we had built by Vantare' in Florida (a Featherlight company by that time...October of 2000) had a 17.5 KW turbo diesel generator in Bay 3 of the basement, along with two each 4000 watt inverters with one on each leg of the 220 V system, so either inverter could add 35 amps of AC power to its leg of the AC supply. The coach had enough battery storage (each inverter was 24 VDC input..) with 8 AGM 4-D batteries to power the stateroom air overnight without starting the genset, and the main engine alternator was 270 amp 24 volt. Plenty of juice for those times when shore power was not available, although this was not a machine that you would take in the boonies and dry camp.:lol: It was 45 feet long and weighed just under 50,000 lbs as we had it equipped for our business needs.

All the air conditioners were basement mounted units as well. I have some pictures I could send you or post here, but would need to scan them into the computer. The generator was in a steel cabinet with shock isolation mounts, and the interior of that enclosure was lined with foamed lead much like found in the very expensive high end yachts. It was amazingly quiet for such a large generator.