Everything I said in my previous postings applies to XADC as well. I own Truecharge 40+ and Prosine 2.0 and it applies to those as well. The following Xantrex explanation should help: Xantrex 3-stage charging
Keep on mind that to force any of those chargers into bulk stage (constant current) there has to be ENOUGH load on the charger as per previous postings.
That's exactly what I did to my Parallax 7345 converter. I have a +12V cable run of perhaps 20 ft from converter to batteries. Due to the line voltage drop, the batteries took 'ages' to charge. I opened up the feedback loop (within the converter), and added a resistor and small diode (diode clamps output voltage in case of a failure) to the converter. I then ran a small cable from the opened feedback to the battery. When not in current limit, the converter will now supply 13.7V directly at the battery, regardless of line drop. Charging times are significantly reduced.
Cal
pnichols wrote: "....and the terminal voltage on CHARGER TERMINALS"
That's why it's best to use the largest cables and/or shortest length cables that you can afford and/or fit between the charger's output terminals and your battery terminals - so that the voltage on the charger's terminals is as close as possible to that on the battery terminals almost regardless of current flow up to the limits of the charger or safe battery acceptance.
(Another way to design a charger to ensure minimum charge time would be to eliminate this large-as-possible-cable-size requirement by incorporating remote battery terminal voltage sensing into the charger's control circuitry so it would be absolutely controlling the battery terminal voltage instead of the cable size versus current relationship controlling what voltage winds up on the battery terminals. This approach would require expert installation in RVs as an engineered total system, however, with minimum intervention/tampering by non-expert owners or RV technicians afterwards - as cable heating or battery meltdown could be a safety concern.)
Cal, excellent idea. I've always thought this could be done as it has been standard on industrial power supplies for years. Could you give a few more details?
Jim, I suspect you have more line drop than you think. You are not maintaining a constant 60A of charging current. Your voltage measurement location is probably at the battery. If you place the voltmeter directly at the converter, you will see a different story. The voltage at the converter is where the converter 'thinks' the battery is at. Your charts show that the converter is hardly ever (less than a minute) in constant current mode.
A simple way to measure line drop is to place your voltmeter between the positive output terminal of the converter and the positive terminal of the battery. Now charge your battery while recording charging current and line drop voltage. To avoid measurement errors, I would disconnect all MH 12V loads.
Line resistance = line drop voltage/charging current
Do the same measurement for the ground side.
Cal
bigfootford wrote: Look carefully at the charts I posted.....Your explanation is from text (what you have read). My charts pose a similar situation as the OP. Short cables with no voltage drop or long cables with less than .15 drop, 50% discharged battery and 25% discharged batteries. The XADC does not perform like you described or from the MFG. White papers.
Note from the beginning of the charge the voltage climbs and the amps go down. That wouldn't be constant anything would it?
Quote: suspect you have more line drop than you think. You are not maintaining a constant 60A of charging current
The other determining factor is the batteries internal resistance which will very according to temp, size, state of charge and condition... just to name a few.
My Parallax 7345 converter (2-stage) was so slow in charging, I decided to either chuck it or modify it into a turbo mode. It was slow in charging because I had 20 mohm line drop on the positive cable. It would have been a major hassle (and expense) to replace my 8 awg cable which is over 20 ft long. I decided to modify the converter and locate the feedback voltage directly at the battery. The 20 mohm line drop is now eliminated.
This procedure only works for the 7345 converter. There's a resistor divider network consisting of R32, R33, R34. One side of R32 connects to the output voltage (this is the feedback voltage), the other side connects to R33. Lift the lead of R32 that connects to the output voltage. Solder into the vacated resistor lead hole a small signal diode (1N4148 or what ever) - anode side into the hole. Connect the diode's cathode side to resistor R32 lead that's in the air. Solder a 100 ohm resistor to the same junction (R32 & diode cathode). Connect a wire to the other side of the 100 ohm, 1/8W resistor and run it to the battery positive terminal. That's it!
The diode is for protection. Should the feedback wire (the new wire going to the battery) open, the converter will limit output voltage to a safe level.
Hurricaner- I go to Gooseberry Mesa to mountainbike every spring. Great place!
Cal
Hurricaner wrote: Cal, excellent idea. I've always thought this could be done as it has been standard on industrial power supplies for years. Could you give a few more details?
It would probably work for any of the 7300 or 7400 series converters, good info if I ever run across one. It has always surprised me that none of the converter manufactures have done this, but one of the reasons is it only works if the converter is ran directly to the battery and the panel is wired off the battery. If the converter powers the panel first the voltage could exceed a safe threshold at the panel.
Salvo wrote: Jim, I suspect you have more line drop than you think. You are not maintaining a constant 60A of charging current. Your voltage measurement location is probably at the battery. If you place the voltmeter directly at the converter, you will see a different story. The voltage at the converter is where the converter 'thinks' the battery is at. Your charts show that the converter is hardly ever (less than a minute) in constant current mode.
A simple way to measure line drop is to place your voltmeter between the positive output terminal of the converter and the positive terminal of the battery. Now charge your battery while recording charging current and line drop voltage. To avoid measurement errors, I would disconnect all MH 12V loads.
Line resistance = line drop voltage/charging current
Do the same measurement for the ground side.
Cal
bigfootford wrote: Look carefully at the charts I posted.....Your explanation is from text (what you have read). My charts pose a similar situation as the OP. Short cables with no voltage drop or long cables with less than .15 drop, 50% discharged battery and 25% discharged batteries. The XADC does not perform like you described or from the MFG. White papers.
Note from the beginning of the charge the voltage climbs and the amps go down. That wouldn't be constant anything would it?
Jim
The charts show both long cables actual application and short cables bench testing.
Short cables 6 ft total with crimped and soldered...= no drop.
Jim
94 F-250 ex cab,460, E40D tranny,airbags w/pump,bilstein shocks, 2000 Bigfoot 9.6 2500 camper, Xantrex XADC 60 converter, 1 Universal group 30 AGM and an eu2000i honda genny.
Wife and Molly- Ausie,Queensland healer
You state: "Note from the beginning of the charge the voltage climbs and the amps go down. That wouldn't be constant anything would it?"
You never get into constant current mode (which would be ~60A), but you are in constant voltage mode (~14.35V). You don't get into constant current mode because you just don't have enough load. The converter has the potential to deliver more than the battery can accept. There's just one battery, right?
Looking at your second chart, we can determine your line resistance. When the converter delivers 25A the battery is at ~13.98V. When at 10A, the battery is ~14.2V.
During the phase where battery voltage is rising and current is dropping the output of the converter maintains a constant output voltage. This voltage is:
You state: "Note from the beginning of the charge the voltage climbs and the amps go down. That wouldn't be constant anything would it?"
You never get into constant current mode (which would be ~60A), but you are in constant voltage mode (~14.35V). You don't get into constant current mode because you just don't have enough load. The converter has the potential to deliver more than the battery can accept. There's just one battery, right?
Looking at your second chart, we can determine your line resistance. When the converter delivers 25A the battery is at ~13.98V. When at 10A, the battery is ~14.2V.
During the phase where battery voltage is rising and current is dropping the output of the converter maintains a constant output voltage. This voltage is:
Salvo, Yes in the chart examples they were obtained with one AGM 110ah battery. I do have others derived from 2 group 24's.
The math shows a .37 volt drop.....actual measurements during initial charging showed less than .3 measured at the converter and then at the battery. (200 mv of that from 2 100 mv shunts). I was attempting to keep under .3 for my actual system.
The 3rd chart was derived with the short cables. The resistance with the math then is about 5 Milli ohms and a drop of .1 vdc. That equates to the value of the 100 mv shunt I use for testing.
My system was installed to represent the average Joe's installation.
Shunt for the trimetric, cutoff switch, disaster fuse (85 amp) and a magnetek converter modification to incorp. a multi-stage converter. There is going to be drops in voltage in all our systems.
Despite all this discussion.....
If I was to put a 20 ah battery that was down 50% SOC and I put the XADC 60 on it to charge I would expect it to do the bulk mode and give the battery what ever it can accept, It wouldn't be much but still it should be bulk mode, then after bulk mode It should switch to absorb mode and do that for 2 hrs or so. in theory get the battery close to 100%. Then drop into Float of 13.5. I have not seen the XADC perform that way.
Same applies to the others PD, WFCO etc. Do they perform exactly as specified???? No. But the PD is the one that does the best in my book.
We've heard now of 2 different PD users modifying the electronics to compensate for performance.
Maybe this has hijacked the OP's post and I apologize for that.
His problem is not resolved, although early on we all said his wiring was probably to fault. I hope we haven't scared him off.
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