I have seen a number of posts that here that talk about using more than one battery charger at the same time to speed up the charge when on generator power. I am hoping to do this with the following setup. I just boutht a B&D 40 amp charger (as recommended on this forum) and have an IOTA 45A 2 stage charger/converter built into the trailer. The IOTA doesn't have the IQ4 controller, as this is the "special" model created for Jayco that will not accept the IQ4.
What I'd like to do is hook both the B&D (connected directly to the generator) and the IOTA (through the shore power cable to the generator) and do a bulk charge to get the recharge started in the morning and then let the solar top them up throughout the day. This way I should be able to have a theoretical maximum charge rate of around 85A.
Is this reasonable? What will happen when the B&D wants to go into absorption mode at 14.4V but the IOTA will only do 13.7V?
It's possible to do what want but it's tricky. You need to have both chargers sharing the load and that's very hard to obtain unless the chargers have very precise voltage controllers. In all likelihood one of the two chargers will hog the voltage and do the charging to its capacity. The other charger will just sit and idle and do nothing.
Your best bet is to just charge the battery with one charger. If you want charge at a higher rate, then you'll need to buy a higher capacity charger.
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Quote: "Is this reasonable? What will happen when the B&D wants to go into absorption mode at 14.4V but the IOTA will only do 13.7V?"
If that happens you will get around 50 amps each hour until B&D charger falls back to 13.7 volts too. Then you will be at about 20 amps, or possibly one falls back to float-mode.
Generally; if the batteries are low both may stay in "bulk-mode - 14.4 volts" for a while before one charger drops back, so you can still save time with both charging.
If you stop and think about it, motor-homes are almost always in multiple charging modes. My 2 9-watt solar panels are always on during daylight. The engine alternator is charging both sets while driving/idling. The generator may also be on to run house heat or air. That means the converter/charger may also be on. None of this causes any problems and some may go back to float-mode as batteries near full charge.
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While in theory it might seem an improvement to add an additional charger to the mix the limiting factor is actually the battery's acceptance resistance.
If you are employing say a 60 amp capable charger/converter, And say it is producing 40 amps charge to the battery. 5 additional chargers all at the same voltage will gain no additional current to the battery. They will consume more shore power though.
Where adding an additional charger might help initially is where there is a LARGE depleted bank and the charger is producing Max output. Then an additional charger would help till the overall charge rate drops below the max output of the most robust of the chargers.
* This post was
edited 04/12/12 04:37pm by SCClockDr *
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I agree using two chargers will disrupt the smart mode charging of the smart mode battery charger. The smart mode 40AMP charger should re-charge your batteries to a 90% charge rate in a short 2-3 hours all by itself. You will not gain anything by adding a second battery charger. Its more related to different charging voltage levels and not the brute force high charging currents like used to be the normal way to get a quick battery charge.
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The B & D and Iota will both contribute amps (40a from BD and a few tapering ones from the Iota) until the battery reaches the Iota's voltage (which will not take long) then the B & D will do it all from there. If you had the IQ4, then they both would add their amps the way you want, because now the Iota would be near the same voltage as the charger.
This shows the action where the B&D with the higher voltage than the other Vectors stays on while the others eventually drop out of play as battery voltage rises.
Really all I'm hoping to do is limit the generator run time and maximize my solar charging. So it appears that I will get a short boost in amps until the voltage hits 13.7 and then the Iota will drop out. I guess there is a slight advantage to this as it will add a few additional amps during the short generator run. Then I just let the solar top them off. I'll give this a trial run and put an ammeter on the Iota to see how many extra amps I actually get.
You want two of those BD 40 ampers to do it rught at 80 amps, but any old charger you have lying around that will do 10 or 15 amps and go up to 14.4 volts (typical) will add amps longer than the straight Iota will, and you will get 50 -55 amps for a while. Pile on every charger you own and let them sort it out among themselves.
One thing that works for me is to have a separate deep-cycle battery to use for HD television, recharging phone, computer, Kindle Fire. The two T-105's handle the house when off shore-power.
The generator is run to power converter/3-stage charger for T-105's and chassis-battery. A Schummacher Speed-charger, SC12000A, recharges the separate 12V, 80 AH, Trojan (just replaced 9 year old Optima Blue Top 55AH) while plugged into outside M.H. outlet. This way both reach "bulk-rate 14.4 v" charging. Generator needs to run only 2 hours to meet our needs, and T-105's will have their 10th birthday this fall.