One thing you have to consider, the wire size is not too critical on
charging....it is more critical on discharging.
In the beginning--(when the battery is discharged)
there is a high current and some drop in the charge power (current and
voltage) due to resistance of the charge wire. However, as long as the
wire does not get hot or create a hazard, this time is short and the charge
current tapers down quite fast. But the real worry is not over heating the
batteries which the charger should consider.
In the end--(when the battery charge is being topped off) The current is
very low and the charger is going for soak or float voltage and almost any
size wire would do since there is low power going to the battery and the
charger is going for voltage considerations which are effected little by
the wire size.
Converter operation
If you are like Heinz and Henry, and want to use the charger as another
battery bank,(drawing almost the full output of the charger to operate
equipment), you will need cables to the load just like a battery bank.
But this is a supply problem, not a charge problem.
Discharge is the problem.
If you have an 1000 watt inverter, it had better be within inches of the
battery with cables the size of your thumb. The GMC has large cables to
the boost relay because we are going to help crank the engines through the
boost position.
So you have some flexibility depending upon your requirements. If you just
want to charge the battery, the wire size is not that critical. If you
think you are going to draw 50 amps from the charger and another 50 amps
from the battery at the same time, you need to consider the wire size.
gene
>>Thanks Emery and Henry and everyone else who commented. I follow you
>>loud and clear. Installing as advised. A couple more questions .
>>Statpower advises not to use the existing cables going to the batteries
>>but to use a direct #2 to replace and also a dedicated negative to
>>replace the chasis which was originally used as a conductor.
>
>Their reasons have some validity. But, the gauge wire that should be used
>is a function of the distance between the battery and the charger. There
>are circumstances under which you would need 4/0 wire to hook up the
>charger (get a long enough distance and you'll need the big gauge). There's
>very little magical about the TrueCharge aside from the automatic voltage
>monitoring function. It puts out 40 amps max. Size your connection wire
>accordingly and you'll be safe. There may be advantages to using the large
>size wire for the monitoring functions.
>
>>I
>>understand the latter, but it seems to me if the connections are kept
>>clean the existing positive cable should be OK .
>
>The existing ground can be fine too. Make certain that it's clean. That's a
>tall order given the multiple connections through aluminum on the GMC
>frame. I installed a 1/0 wire for the inverter so that gets used now for
>ground in my case. Likewise, the positive wire provides a convenient way of
>getting a very low resistance connection for the 12V. I did run my
>TrueCharge for 1 year using the coach ground and the 12V wiring that was in
>place. The gauges were acceptable to me according to standard wires tables.
>SInce I'm trying to get more out of my battery system, I no longer use the
>standard tables in the usual manner. I go up a gauge on the "marine table
>for use in engine environments". Still I have a lot of original wire in the
>coach.
>
>> It does ,however, have
>>a 60 amp circuit breaker which might show some voltage loss. Some have
>>recommended 50 amp fuses in the new positive lines but I'm afraid that
>>also would show a voltage drop and confuse the statpowers voltage
>>readings when charging.
>
>Not a problem that I can tell. You do want to fuse the wires close to the
>battery as a safety item.
>
>>Since the difference between a a full and
>>discharged battery is only about a half a volt, a tenth of a volt might
>>be a significant error. More comments please.
>
>At 70 degrees F you have close to 0.8V span. But your point is still well
>taken. Take the time to clean everything completely. It's a pain in the
>rear but I think that it's well worth the effort.
>
>Henry
>
>
>
>
Genef -- 77PB/ore/ca
GMC MOTORHOME INFORMATION
mr.erf
http://www.california.com/~eagle/
charging....it is more critical on discharging.
In the beginning--(when the battery is discharged)
there is a high current and some drop in the charge power (current and
voltage) due to resistance of the charge wire. However, as long as the
wire does not get hot or create a hazard, this time is short and the charge
current tapers down quite fast. But the real worry is not over heating the
batteries which the charger should consider.
In the end--(when the battery charge is being topped off) The current is
very low and the charger is going for soak or float voltage and almost any
size wire would do since there is low power going to the battery and the
charger is going for voltage considerations which are effected little by
the wire size.
Converter operation
If you are like Heinz and Henry, and want to use the charger as another
battery bank,(drawing almost the full output of the charger to operate
equipment), you will need cables to the load just like a battery bank.
But this is a supply problem, not a charge problem.
Discharge is the problem.
If you have an 1000 watt inverter, it had better be within inches of the
battery with cables the size of your thumb. The GMC has large cables to
the boost relay because we are going to help crank the engines through the
boost position.
So you have some flexibility depending upon your requirements. If you just
want to charge the battery, the wire size is not that critical. If you
think you are going to draw 50 amps from the charger and another 50 amps
from the battery at the same time, you need to consider the wire size.
gene
>>Thanks Emery and Henry and everyone else who commented. I follow you
>>loud and clear. Installing as advised. A couple more questions .
>>Statpower advises not to use the existing cables going to the batteries
>>but to use a direct #2 to replace and also a dedicated negative to
>>replace the chasis which was originally used as a conductor.
>
>Their reasons have some validity. But, the gauge wire that should be used
>is a function of the distance between the battery and the charger. There
>are circumstances under which you would need 4/0 wire to hook up the
>charger (get a long enough distance and you'll need the big gauge). There's
>very little magical about the TrueCharge aside from the automatic voltage
>monitoring function. It puts out 40 amps max. Size your connection wire
>accordingly and you'll be safe. There may be advantages to using the large
>size wire for the monitoring functions.
>
>>I
>>understand the latter, but it seems to me if the connections are kept
>>clean the existing positive cable should be OK .
>
>The existing ground can be fine too. Make certain that it's clean. That's a
>tall order given the multiple connections through aluminum on the GMC
>frame. I installed a 1/0 wire for the inverter so that gets used now for
>ground in my case. Likewise, the positive wire provides a convenient way of
>getting a very low resistance connection for the 12V. I did run my
>TrueCharge for 1 year using the coach ground and the 12V wiring that was in
>place. The gauges were acceptable to me according to standard wires tables.
>SInce I'm trying to get more out of my battery system, I no longer use the
>standard tables in the usual manner. I go up a gauge on the "marine table
>for use in engine environments". Still I have a lot of original wire in the
>coach.
>
>> It does ,however, have
>>a 60 amp circuit breaker which might show some voltage loss. Some have
>>recommended 50 amp fuses in the new positive lines but I'm afraid that
>>also would show a voltage drop and confuse the statpowers voltage
>>readings when charging.
>
>Not a problem that I can tell. You do want to fuse the wires close to the
>battery as a safety item.
>
>>Since the difference between a a full and
>>discharged battery is only about a half a volt, a tenth of a volt might
>>be a significant error. More comments please.
>
>At 70 degrees F you have close to 0.8V span. But your point is still well
>taken. Take the time to clean everything completely. It's a pain in the
>rear but I think that it's well worth the effort.
>
>Henry
>
>
>
>
Genef -- 77PB/ore/ca
GMC MOTORHOME INFORMATION
mr.erf
http://www.california.com/~eagle/
