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Old 10-09-2013, 10:04 AM   #1
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Default How to test the "bulk charge" function of my conve

After Shadow and Webslave's recent discussion of upgrading the charger, I watched part of the excellent video that Shadow posted. But before I undertake a big upgrade, I have a very basic question -- how does one test whether the bulk charging function of the stock converter is adequate or not?

I understand that I need to deplete the battery in order to trigger the charging cycle -- I know how to do that. The video said that although the stock converter says it is charging at about 22 amps, it really isn't -- it'll dwindle down to 8 amps. What testing tool will provide that info? Will my ordinary digital multimeter do the job? I know it is a basic question, but I have been unable to find the answer on Google.

Second, I happen to have a separate stand-alone plug-in "deep cycle" charger that I bought at Napa. It has three settings: 10 amp, 2 amp, and 55 amp. The 55 amp setting says it is for starting a car -- I have never tried using it on my trailer batteries. Shadow's video mentions that the new charger he installed would put out 55 amps.

Does this mean that I can use the 55 amp setting on the Napa charger without harming the battery?? If so, I could plug it into my Honda 2000 generator and recharge my battery right quick, without having to upgrade my converter. I never let my deep cycle batteries get below 12.1 volts, or 50% state of charge. So with a 110 amp hour group 31 battery, that means (I think) that I would only need an hour at 55 amps to fully charge the battery. Is that right?

Again, sorry for the very basic questions -- and thanks in advance for your advice!!

PS -- when we are not on the road, my batteries are hooked up to a Battery Minder Plus -- after three seasons of hard use, the batteries are in great shape -- I test the cells with a hydrometer, and they are all doing just fine.
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Old 10-09-2013, 10:18 AM   #2
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multimeter will do the job, one with clamps so you can measure current draw. open the wfco panel and probe the connections there when you start charging, I was surprised by the fact that it was in maintenance mode all the time and my unit is only 1 year old. I have solar so not a huge deal, this forum is what made me check it out and prior to solar I ran a gen for 7 hours and the charge was crap! should have figured it our then. You can also measure voltage in peak charge you should be at 14.4+volts, wfco maxs at 13.2 on my unit. If you look at both units side by side you can see that more thought went into the pd4600 design. Good luck, if you do get the 4600 55amp there is one error in the directions on step 9. tells you to hook converter wire to terminal marked VCC, hook to term marked CONV. spoke with the owner about the error and I guess they are fixing the typo.
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Old 10-09-2013, 10:21 AM   #3
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missed the 55amp question. Deep cycles always a good idea to charge on turtle mode, won't screw the plates up as quickly. The 4600 has the quick charge which should be used only if boon docking and have limited charging time. the nicd thing about the 4600 is it senses battery state and manages so you don't mess up the batteries and gives you the manual override option
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Old 10-09-2013, 10:53 AM   #4
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Default Turtle mode, 55 amp, or something in-between?

Shadow, thanks for the fast response!! My plug-in charger (not the converter) charges at 10 amps. The direct DC charger from my generator charges (I think) at 8 amps. The 55 amp option sounds like it could damage the plates, and the only time I need to charge is when I am boondocking.

So here is my question -- what is the happy medium between a too-fast charge and a too-slow charge? Maybe 20 or 30 amps? Do you know of a stand-alone charger that could do the job, without having to upgrade the converter?

As always, thanks for your willingness to share your expertise!
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Old 10-09-2013, 11:57 AM   #5
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3 stage chargers wont hurt your battery, read on
Battery charging takes place in 3 basic stages: Bulk, Absorption, and Float.

Bulk Charge - The first stage of 3-stage battery charging. Current is sent to batteries at the maximum safe rate they will accept until voltage rises to near (80-90%) full charge level. Voltages at this stage typically range from 10.5 volts to 15 volts. There is no "correct" voltage for bulk charging, but there may be limits on the maximum current that the battery and/or wiring can take.

Absorption Charge: The 2nd stage of 3-stage battery charging. Voltage remains constant and current gradually tapers off as internal resistance increases during charging. It is during this stage that the charger puts out maximum voltage. Voltages at this stage are typically around 14.2 to 15.5 volts. (The internal resistance gradually goes up because there is less and less to be converted back to normal full charge).

Float Charge: The 3rd stage of 3-stage battery charging. After batteries reach full charge, charging voltage is reduced to a lower level (typically 12.8 to 13.2) to reduce gassing and prolong battery life. This is often referred to as a maintenance or trickle charge, since it's main purpose is to keep an already charged battery from discharging. PWM, or "pulse width modulation" accomplishes the same thing. In PWM, the controller or charger senses tiny voltage drops in the battery and sends very short charging cycles (pulses) to the battery. This may occur several hundred times per minute. It is called "pulse width" because the width of the pulses may vary from a few microseconds to several seconds. Note that for long term float service, such as backup power systems that are seldom discharged, the float voltage should be around 13.02 to 13.20 volts.

Chargers: Most garage and consumer (automotive) type battery chargers are bulk charge only, and have little (if any) voltage regulation. They are fine for a quick boost to low batteries, but not to leave on for long periods. Among the regulated chargers, there are the voltage regulated ones, such as Iota Engineering, PowerMax, and others, which keep a constant regulated voltage on the batteries. If these are set to the correct voltages for your batteries, they will keep the batteries charged without damage. These are sometimes called "taper charge" - as if that is a selling point. What taper charge really means is that as the battery gets charged up, the voltage goes up, so the amps out of the charger goes down. They charge OK, but a charger rated at 20 amps may only be supplying 5 amps when the batteries are 80% charged. To get around this, Xantrex (and maybe others?) have come out with "smart", or multi-stage chargers. These use a variable voltage to keep the charging amps much more constant for faster charging.
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