Battery Charging

MEXICOWANDERER wrote:
I would rather put the limit at 15 volts because no automotive voltage regulator meaning alternator control is going to top out less than 14 volts unless the alternator warms up and the thermistor within the voltage divider network starts ramping control set point downward. Most Delco and Ford integral regs commonly start out in the 14.2 - 14.4 range at 25c. Motorhomes traveling long distances will arrive at set point limit for hour after hour. Hard to keep the Hatfield chassis batteries satisfied with a house battery diet and verce-visa.

I will give a normal example of Chassis Alternator failure indicator lights on Motorhomes. Roadmaster and Ford(Freightliner and Spartan and Workhorse/chevy do not seem to have this problem). You Start the Engine. You then start the Genset and you have an Inverter/Charger. When the Inverter/Charger goes to BULK charge(over 14.1 volts), during that time it is in Bulk charge the Dash Alternator trouble light will come ON. Once the Bulk charge stops the Light goes out. OR, you just turn the headlamps and Dash AC ON and that amp draw will usually drop the voltage below the 14.2 that is the fault threshold. This is not a real problem but concerns some when they see that red Fault light. Doug

I will use my own RV as and example

But basically ... When you are on Shore or Generator power and you use 12 volts, be it for Lights, Fans, or whatever.. The power comes FIRST from the converter.. This reduces amps for charging.. Then if you need more power than the CONVERTER can pump out. power comes from the batteries.



Progressive Dynamics 9180 capable of up to 80 amps output
Over 500 amp hours of battery STORAGE.

Multiple loads including lights ranging from Small LED loads (say 2 watts) to 20 watt incandascent lamps (roughly 1.5 amps) and my #3 big load, a Kenwood TS-2000 (100 watt 2-way Radio) #2 is the furnace, #1 is the inverter. But on shore power the inverter is NOT a load.

Now when I click Transmit that TS-2000 can suck close to 15 amps

On shore power that comes from the CONVERTER, so now I only have a max of 65 amps for battery charging. (Less what the lights and fans and other stuff are pulling) I will never have the full 80 amps for battery charging.

In fact, though the factory put in an 80 amp converter.. Max safe charge, as delivered (I've upgraded the battery bank) was 70 amps.. So the factory took that into account in designing my RV.

Mandalay Parr wrote:
Everything stays attached to the batteries. That is the proper design.
No damage is done.

SoundGuy wrote:
Not true at all ... equalize @ 16 volts and you could easily expect to see some smoke. :E

MrWizard wrote:
No Body was talking equalizing
that is a special situation, where things should be dis-connected
before doing it

BUT that is NOT normal operation

Nor did Mandalay Parr exclude it either. :R I'll repeat - charge at too high a voltage without first disconnecting the battery from the trailer and you could easily see smoke. :E

SoundGuy wrote:

Mandalay Parr wrote:
Everything stays attached to the batteries. That is the proper design.
No damage is done.

Not true at all ... equalize @ 16 volts and you could easily expect to see some smoke. :E

No Body was talking equalizing
that is a special situation, where things should be dis-connected
before doing it

BUT that is NOT normal operation

I would rather put the limit at 15 volts because no automotive voltage regulator meaning alternator control is going to top out less than 14 volts unless the alternator warms up and the thermistor within the voltage divider network starts ramping control set point downward. Most Delco and Ford integral regs commonly start out in the 14.2 - 14.4 range at 25c. Motorhomes traveling long distances will arrive at set point limit for hour after hour. Hard to keep the Hatfield chassis batteries satisfied with a house battery diet and verce-visa.

1. Unless your add on charger goes OVER 14.2 or so volts, no damage will happen. Lets take charger at 14.2 volts. The 14.2 volts will be seen and transmitted to all DC lines and appliances.
2. AMPS is the work term. Very doubtful that any extra charger will supply MORE than 40 or 50 amps. Probably closer to 2 to 20 amps as most aftermarket battery chargers run in that range
3. NOW, a responder stated an equalization charge up to 16 volts. YES, the ideal is to DISCONNECT all loads(12 volt appliances) when doing a Equalization charge and the Manuals for chargers that can do equalization state to have NO 12 volt appliances connected when doing the high dc voltage charge. Sustained DC voltages OVER 14 volts can damage some DC appliances. Doug

Mandalay Parr wrote:
Everything stays attached to the batteries. That is the proper design.
No damage is done.

Not true at all ... equalize @ 16 volts and you could easily expect to see some smoke. :E

everything stays attached
power will be used if things are tuned on
AKA using the inverter to watch Tv or use the PC etc..
amps produced by the charger will be applied at the battery terminals
the inverter , lights etc.. will use some of that power, the part not being used goes to the batteries, depending on the battery state of charge
in other words, they might or might not accept everything that is left over
depends on how much they need, and how large the charger/converter is

Thanks everyone. I figured it had to be something like that but I wasn't going to assume anything and not knowing for sure, I knew this was the place to ask!

None of your DC circuits are isolated from the battery, thus whatever voltage you apply to the battery is also applied to all your DC circuits. Normally not an issue unless your charger supplies too high a voltage. The maximum recommended voltage for the circuit board on my refrigerator is 15.4vdc thus I set the maximum voltage setting on my solar charger to 15.3 so it will never go above that. Unless your charger has an equalize function, or can be set to a higher voltage "top off", or "mini Equalization" you'll probably never see too high a voltage even with temperature compensation.