Typical Voltages and Electrical Battery Charging Issues

[Woods]

I am waiting on the power monitor. My smart battery charger indicates the battery is fine. When the battery monitor arrives and I disconnect the battery. I'll take it to AutoZone for a check. I think that I may need a new converter/battery charger (11.57 volts). I am not sure the type supplied in a 2001 Coachmen. I haven't been able to find it? Maybe, it's mounted underneath the coach? Anyway the new ones seem to be microprocessor controlled and multi-stage. My RV manual seems to recommend not leaving on shore power too long due to overcharging? The new smart chargers and hopefully converters should manage that automatically. Sounds like a good upgrade. Anyone have an opinion or suggestion on a converter? I am considering the PowerMax PM3-100 100amp. I keep thinking that I am finished upgrading. But, it seems to be an ongoing process

 

[Woods]

Thank you all so much! After 11 months the battery was shot. The place that I always buy batteries has gone out of business. I am camping next week so I just got a 100ah Diehard from Advance Auto. The Victron Smart Shunt is installed and the app is connected. Generator starts right up and lights are bright! The charging voltage from the converter increasing as current into the battery decreases.

 

[Bob K4TAX]

I am waiting on the power monitor. My smart battery charger indicates the battery is fine. When the battery monitor arrives and I disconnect the battery. I'll take it to AutoZone for a check. I think that I may need a new converter/battery charger (11.57 volts). I am not sure the type supplied in a 2001 Coachmen. I haven't been able to find it? Maybe, it's mounted underneath the coach? Anyway the new ones seem to be microprocessor controlled and multi-stage. My RV manual seems to recommend not leaving on shore power too long due to overcharging? The new smart chargers and hopefully converters should manage that automatically. Sounds like a good upgrade. Anyone have an opinion or suggestion on a converter? I am considering the PowerMax PM3-100 100amp. I keep thinking that I am finished upgrading. But, it seems to be an ongoing process

If you have one of the older style converters, one that uses a saturable core reactor, then yes, don't leave it plugged in indefinitely. If you have a converter that is a "smart converter" then it has 3 or 4 stages of charging and will not overcharge a battery.

For an efficient converter, I suggest talking with the folks at Progressive Dynamics. They have a wealth of accurate information and can correctly advise you on the proper choice for your application.

Bob

 

[Woods]

The smart shunt was a good upgrade! Now I can see that the converter is pretty much junk. Seems to always stop charging at 12.6 volts. The truck running charges until 13.7 volts. (see below) When the converter stops the truck will still push over 30 amps into the battery. Dry camping is pretty much impossible with the generator . Must use the truck engine. 1st picture truck. 2nd picture generator. Tested back to back.

As noted above, I will need to upgrade my converter. Or possibly just plug in my 100amp microprocessor controlled charger with the generator running? Or just continue to run the truck (V10 engine) to charge the batteries. For 3 day weekend mileage went down from 7mpg to 5mpg for battery charging gas use. Is it safe to use a battery charger while using the motorhome and appliances? What do you all think about upgrading to a combination converter / inverter (multi-stage, microprocessor controlled)? Appliances and charging work fine when truck is running and voltage gets close to 14v. Thanks for all your help!

 

[TheLooks]

First let me go back to the fridge issue. No matter what source of power it is using you need 12v dc. If you are on shore power or generator, or propane, 12 vdc still runs the show. It is the control power regardless of what is doing the hard work. It is safe to use a charger to maintain the batteries. Most if not all maintainers are low amperage and are not made to supply fast amps. You only have one battery and when it is taxed the convertor fills in the gap. Speaking of one battery, you will need more then one to run an inverter for long, a 100 ah battery is only good for half that or you will damage it. I recommend doing a lot of research on this subject to get better acquainted with how batteries and the related equipment work. It is not rocket science but I don't think it is intuitive for many. Take the time to learn Ohms law. Watts = Amps x Volts. Amps = Watts/Volts. Volts = Watts/Amps. Just understanding this and the reality of how much power(watts) is available from a given battery will serve you well. And this...https://deepcyclebatterystore.com/how-to-maintain-batteries/

 

[TheLooks]

You mentioned buying a 100 ah battery.....I hope it was a marine/rv battery or deep cycle type.

 

[Kevin D Pem]

Wow!
Long post to have missed so much.
A lead battery dead voltage is 12.0 anything less tells me a cell has shorted or fallen out of the circuit.

What is the converter voltage with the battery out of the circuit?

12.67 = full charge of a sitting disconnect battery! The converter voltage should be 13.6 minimum to fully charge the battery!

It is a slow charge at best at 13.6 so we are talking days not hours.

As I recall MD on a marine battery means deep cycle. You should make sure the battery is not a starting battery.

A rv fridge likely will not run with battery voltage of 12v.

The only way to make it thru the night on battery power is to start with a fully charged battery. Even then a furnace running the chance of making it thru with 100ah is a crapshoot.

 

[Woods]

A good point about the furnace fan. We slept with the door open (just screen). The heat was set to 68 and never came on. Heating requirement would be a whole new variable.

The Diehard is 100ah AGM battery. Running the truck for an hour or so in the morning and an hour or so before bed worked great. Using the Victron shunt, I would make sure nonessentials were off before leaving the camper (or going to bed). The Victron would usually say between 16 hours and 4 days left depending on the current load. With only sensors and refrigerator on, I would usually draw between 0.8 to 2 amps. Usually the batteries were about 80% in the morning and 80% upon returning for bed. I would charge the battery every morning and night until indicator said 100% and amps went below 2 amps. Extra battery capacity would be great. I don't camp without power very often and extra battery would take up cargo storage. So weighing the pros and cons. Thanks for all you guys help. The Victron gives a lot of visibility into the battery usage and charging. Using the converter / generator to charge did very little to actually charge the batteries. They would trickle charge until 12.6 volts and then stop per the pictures. I haven't checked the voltage with the batteries disconnected yet. I have a MagneTek 900 Series Converter. The Victron helped make this an awesome first trip of the year! I'll have maybe 2 more trips without shore power.

 

[Woods]

I plan to install the plumbing accumulator tank next month. The battery monitor and accumulator tank should be standard equipment. Dry camping is nothing but guess work without the monitor. Thanks again for all of your help! Looking back on all my adventures, I wish that I had never bought a new generator (mine went out). Only need enough power to run the microwave for 3 minutes each day. $5000 for a bag of microwave popcorn is too much! Maybe the generator would be useful, if the converter actually had the power to charge my batteries in a short amount of time (like the truck). I can't stand to hear the generator run continuously for days to slowly trickle a battery charge. I might spend even more on this money pit and get a real converter / charger? Probably just make do!

 

[Bob K4TAX]

I plan to install the plumbing accumulator tank next month. The battery monitor and accumulator tank should be standard equipment. Dry camping is nothing but guess work without the monitor. Thanks again for all of your help! Looking back on all my adventures, I wish that I had never bought a new generator (mine went out). Only need enough power to run the microwave for 3 minutes each day. $5000 for a bag of microwave popcorn is too much! Maybe the generator would be useful, if the converter actually had the power to charge my batteries in a short amount of time (like the truck). I can't stand to hear the generator run continuously for days to slowly trickle a battery charge. I might spend even more on this money pit and get a real converter / charger? Probably just make do!

A $650 Champion generator, 2500 watt inverter, will do the job and save you $4300. If your converter won't charge the batteries, I'd say one needs to look at the type and size of the converter. Ours is a 50A-rated converter and will bring our batteries to full charge in less than 4 hrs., depending on the level of discharge.

Bob