Salvo
California
Senior Member
Joined: 06/01/2008
View Profile
 Offline
|
Phil-
I wish you luck in proving the 7345 works with your batteries. I guess it all depends on how patient you are with the charge times. Why not invest in a nice 100A panel meter? Here's one for $20.
100A Panel meter
With that meter you'll have the tools to complete your analysis.
I have a similar meter. Couldn't do without it!
BTW, you'll need a separate power source for the meter. I would suggest a 9V battery with ON/OFF switch.
You're right, I'm too hard on the 7345. It's really not the converter's fault. It's Winnebago's fault. I don't think they have any electronic/electricity knowledge. They installed the converter under the fridge. The fridge is far, far away from the batteries. They build for looks, not for function.
PS. CJW8 may have a WFCO for sale.
I also offered to buy somebody's WFCO last week. But it doesn't seem like he took my $25 offer. I'm interested in doing some testing on the unit to see if my theory pans out.
Sal
|
pnichols
Santa Cruz Mountains
Senior Member
Joined: 04/26/2005
View Profile
|
"Why not invest in a nice 100A panel meter? Here's one for $20."
Sal,
I've installed these quite some time ago to monitor my coach batteries:
http://www.ecovantageenergy.com/catalog/items/item204.htm
http://store.solar-electric.com/mka-100-100.html
http://www.bestconverter.com/Voltminder_p_178.html
The meters are mounted right on the dash so I can also keep an eye on things while driving. The ammeter shows me when the alternator has the batteries topped up. The voltmeter tells me that A) I didn't forget to switch ON the coach battery switch so the refrig is operating, and B) that the boost relay that connects the coach and chassis batteries together is operating reliably. I recently had to change this to a silver alloy contact relay because Winnebago's stock relay was getting intermittent (probably corrosion on the contacts).
Phil, 2005 E450 Itasca 324V Spirit
|
CJW8
Arizona
Full Member
Joined: 10/18/2007
View Profile
Good Sam RV Club
Offline
|
Salvo,
Thx for the reply. Are you saying you removed part of your circuit and reloacted it next to the batteries? More than I want to do. Randy at Best Converter took the WFCO's back and sold me the Xantrex XADC40. What a great guy! I do still have my parallex 7345 that I kept as a spare. I had originally 12 feet of #6 on the + and 3 feet of #6 on the - going to frame ground. I ran a parallel #6 fine strand and I still couldn't get the WFCO to go into boost. B4 I returned the last WFCO I ran a test on the bench with very short #6 wire and an amp meter inline. It worked great there.
2004 F350 PSD FX4 SB CC, Banks Cold Air Intake, Banks 5" turbo back exhaust
18,000 Superglide
2003 37SP Forest River Sierra Toyhauler
2008 Polaris RZR
|
Salvo
California
Senior Member
Joined: 06/01/2008
View Profile
Offline
|
CJW8 wrote:Are you saying you removed part of your circuit and reloacted it next to the batteries?
That's correct. I modified the 7345 voltage feedback circuit. It no longer senses the regulation voltage within the converter, but directly at the battery. I needed to run a small secondary cable from converter to battery to sense the voltage.
I figured I had nothing to lose. It was either going to work or blow up.
That's great that Randy took back your WFCO.
Sal
|
AstroBruce
Bucks County, PA
Full Member
Joined: 02/17/2005
View Profile
Good Sam RV Club
|
Salvo wrote:CJW8 wrote:Are you saying you removed part of your circuit and reloacted it next to the batteries?
That's correct. I modified the 7345 voltage feedback circuit. It no longer senses the regulation voltage within the converter, but directly at the battery. I needed to run a small secondary cable from converter to battery to sense the voltage.
I figured I had nothing to lose. It was either going to work or blow up.
That's great that Randy took back your WFCO.
Sal
Would you mind showing us how you did that?
Regards,
Bruce
2006 Trailmanor 3124KB
Cummins Turbodiesel (Came with a 1999 RAM 2500)
|
|
|
smkettner
Southern California
Senior Member
Joined: 03/21/2005
View Profile
Good Sam RV Club
|
CJW8 wrote:I ran a parallel #6 fine strand and I still couldn't get the WFCO to go into boost. B4 I returned the last WFCO I ran a test on the bench with very short #6 wire and an amp meter inline. It worked great there.
I think the a 35 amp WFCO would have worked far better than the 55 amp WFCO.
Water under the bridge now and I am glad you like the XADC-40.
2001 F150 SuperCrew
2006 Keystone Springdale 249FWBHLS
|
Salvo
California
Senior Member
Joined: 06/01/2008
View Profile
Offline
|
Here's my mod to the 7345 converter. R32 is the voltage feedback sense resistor. I lifted the left side of the resistor (R32-1). A 100 ohm resistor is soldered to the lifted R32 lead. The other end of the 100 ohm resistor goes directly to the battery.
I added a protection circuit. If the wire going to the battery gets disconnected, the converter will over voltage and destroy itself. A diode is added from the vacated hole of the R32 resistor (this is the anode side of the diode) to a 390 ohm resistor. The other end of the resistor goes to the junction of the 100 ohm resistor and R32. The schematic does not show the 390 ohm resistor.
The diode will limit output voltage to about 0.4 V greater than battery voltage. You could place 2 diodes in series to get even more power out.
Sal
|
pnichols
Santa Cruz Mountains
Senior Member
Joined: 04/26/2005
View Profile
|
What Sal did could be a great - but tricky - feature addition to any high end multi-stage charger to remove cable size effects. However so far I've seen none with remote voltage sensing.
This may be because remote voltage sensing has potentially serious downsides:
First the charger must be internally protected from over-voltage and over-current damage which is not difficult to include, and is often included, in designs - some of which Sal's modification takes into account with regards to his 7345 converter. The second danger could be much greater and a possible product liability issue for a charger manufacturer. Remote voltage sensing improperly installed could easily "fool" many users into thinking their high power charger could now be used with long runs of 10 or 12 or even 14 awg charge cabling (not talking about the separate sensing wire) because they might try it and initially see that -"Gee, look at that ... 14.6 volts on the battery terminals 25 feet from the charger and the charger is pumping 60 amps into the battery".
This is because the charger would now be maintaining the 14.6 volts on the battery terminals no matter what and normal battery acceptance rates would allow the battery to draw the 60 amps. In a few minutes or seconds the too-small charge cabling would begin to get really hot - maybe in some hidden place or at some connector along it's length - and start a fire in their rig. The charge cabling awg size would have to be chosen carefully/properly so as to be able to carry the charger's maximum current without the cabling or it's connectors heating past safe limits. Charge cabling would also now have to definitely be fused properly based on it's awg size, it's length, any corroded connectors along it's length, and the charger's maximum current.
Without remote voltage sensing, manufacturers and us users can now pay little attention to the above heating hazards since voltage drop in too-small charge cabling is keeping us safe because battery acceptance is getting "automatically" depressed enough such that charger current maximums are not getting pumped through too-small cabling due to the physics. We are OK on safety - but not OK on getting all the current from our chargers and into our batteries that we paid for.
My vote is for chargers to be as close to batteries as possible (just like with large inverters) and to use very large cabling/connector sizes so as to both maximize charger current delivery plus therefore wind up with cabling/connector sizes so beefy that heating is not an issue with most converters or chargers that are commonly used in RVs.
i.e. Many, many Parallax 7345 converters are in the field. Other than the problem of their fixed voltage float boiling some lead acid batteries, how many of us are using 2 awg cabling on their 7345 outputs? Their output terminal lugs are sized for this and they would do much better charging batteries starting at low SOC values.
|
Salvo
California
Senior Member
Joined: 06/01/2008
View Profile
Offline
|
Phil, you can put lipstick on a pig, but it'll still be a pig. Changing to 2 awg cable will not provide much benefit. There's an order of magnitude difference in charge times between the 7345 and XDAC. A larger cable can not make up that difference.
pnichols wrote:i.e. Many, many Parallax 7345 converters are in the field. Other than the problem of their fixed voltage float boiling some lead acid batteries, how many of us are using 2 awg cabling on their 7345 outputs? Their output terminal lugs are sized for this and they would do much better charging batteries starting at low SOC values.
Looks like you have all the tools you need to test your charging system. It's time to roll up the sleeves and do some work!
These would be my suggestions for a complete test.
1. Measure line resistance (both 12V and gnd lines).
2. Measure AGM battery internal resistance.
3. Discharge battery to 50%. Record: time, converter voltage, battery voltage and charging current.
I can give further assistance in completing/defining these tests.
Sal
|
pnichols
Santa Cruz Mountains
Senior Member
Joined: 04/26/2005
View Profile
|
"These would be my suggestions for a complete test."
Sal,
I did several tests similar to what you list a couple of years ago and the data is in the rig and unavailable right now. Our Class C rig is in the shop getting the overhead forward facing bunk window replaced after being shattered by a rock this summer. 
All my testing at this time indicated "pretty good" current replacement by the 7345 (~8 feet of 8 AWG cabling and frame ground) into my 200 AH AGM coach battery set. The batteries reached 90%-95% SOC, if my memory serves me right, in around 3 hours from around 55% SOC (30 amps discharge rate for 3 hours). Alternatively, this time was shortened a bit as indicated by comparison data I took using the V10's alternator (~8 feet of 6 AWG cabling and frame ground). I estimated reaching 90%-95% SOC by watching the ammeter sink to under 5 amps charge acceptance rate and then cross-checking terminal voltage after 24 hours of settling - however I can't recall if my batteries's performance curves showed under 5 amps as being above 90% SOC, but the curves in my last link below definitely show 90%-95% as being about right in this amount of time.
My batteries may be the reason for my thinking the 7345 was doing well, as they are somewhat unusual for use in an RV. They're a couple of Interstate labeled but C&D Technologies manufactured "motive power" 100 AH-each 12V AGM batteries intended for use in wheelchairs, residential solar systems, etc.
Note from this .pdf spec, that since they are to be floated at 13.5V to 13.8V, the 7345 does not damage them. However, since they are AGM ("VRLA") batteries, the 7345 applied voltages also happen to charge them quite fast. As for needing to "sock" them with 14+V periodically, the V10's engine alternator serves this purpose:
http://www.cdstandbypower.com/product/battery/vrla/pdf/dcs_100it.pdf
Notice below in this C&D Technologies technical paper on their VRLA ("AGM") batteries in Figure 1 & Figure 10 that charging voltages right in the range of what the 7345 is capable of (2.25 V/cell = 13.5V and 2.30 V/cell = 13.8V) for outputs of 20 to 30 amps gives times of 2 to 4 hours for recharging from around 50%-55% SOC to around 95% SOC. Note also the "0.1C" shown in the curves. This is 20 amps for my 200 AH battery set:
http://www.cdtechno.com/custserv/pdf/2130.pdf
The subtle learning for me after studying these curves was that the terminal voltage versus energy replacement time for charging of AGM/VRLA batteries is VERY CRITICAL ... especially so in my situation of achieving terminal voltage in the high end of the 7345's 13.5V to 13.8V heavy loading range. Hence my constant emphasis that charge cable size is VERY CRITICAL and that one should strive for every tenth of a volt improvement they can make in applying the highest voltage possible on the terminals of the battery being charged - depending of course on how fast you want to charge plus maximum currents recommended by the battery manufacturer.
As I talked about above, my batteries may be OK with the single stage 7345 assuming I'm OK with around 3 hours charge time. However this degree of terminal voltage sensitivity may not be present with wet cell lead acid battereis, so maybe the use of brute force 14.X higher charge voltages is what's required with them for anywhere near reasonable charging times.
My thinking at this point is that it's not all battery and cable resistance issues, but also may depend upon the chemistry, materials, and construction of the battery as to how well the 73XX single stage converter family does with RV deep cycle batteries.
|
|
|
