I'm upgrading my 1972 converter. For those who aren't familiar with the converters of this era, they have a massive transformer and a relay. When not plugged in, the relay connects the 12V system to the battery. When plugged in, it automatically disconnects the battery and connects the converter to 12V devices. A separate battery charger taps off the output of the converter and charges the battery while it's offline. I haven't yet decided how I'm going to replace mine, as I've extensively modified it to handle charging of 3 systems - coach, chassis and generator.
I dry camp exclusively and have a gen. I want to charge as quickly as possible with the gen then shut down. I'll use two Trojan T105s 6volts 220AH. I have light 12 volt loads - no steps, popouts etc. My only load is refrigerator control, radio, lights and some computer/cell phone charging. No 12V TV. The biggest load is an occasional 1200 watt inverter, but it gets very limited use. That's background. I prefer to replace the old converter with a new converter, but I can live with the existing converter and just add a smart charger. My goal is to find the best charger for the batteries.
My question is simple - What battery charger will do the job best in accordance with the Trojan recommendations for long battery life? The Trojan recommended charge profile is in Fig. 4 here:
Trojan's recommended charge profile is to charge at constant current of at least 22 amps and no more than 28.6 amps (10% to 13% of 20hr discharge AH capacity) until 90% charge is reached. They show that this will take from 14.7 to 16.7 volts to hold that constant current rate.
Once the batteries have reached 90% charge, they recommend constant voltage charge of 14.1 to 14.7 volts until 95% charge is reached at about 1-3% of the AH capacity. During this period from 90-95% the charge amp rate will drop linearly. At about 95% charge the rate will have dropped to 2.2 to 6.6 amps. Then they recommend holding that amp charge rate until 100% charge is reached. They don't recommend equalization unless measurements of the specific gravity show it's needed, but if it is, equalization should be at 15.5 volts.
Another chart they provide shows the "Daily Charge" should be 14.8 volts.
It's important to me to find a charger that will actually charge at 28.6 amps until 90% charge is reached to minimize generator run time. I need one that will charge up to the recommended value of 14.8 volts and would like one that will equalize also, but equalization is less critical to me as I can manually equalizer with other equipment.
I've looked closely at several well regarded combo converter chargers. One is the Progressive Dynamics 9200 series. I've read their six patents and the literature on the converters.
Their "Boost Mode" is the highest voltage available and that's only 14.4 volts. To reach that voltage there are several timers and overrides that may prevent it from getting there. Their anti sulphation mode is only 14.4 volts also, so it won't equalize as recommended, and it does this every day anyway.
I understand that it's difficult for a charger to know the state of charge. The best way is to measure SG, and no chargers measure SG. However, I do measure it. I also have a battery monitor TriMetric 2025 and I watch the condition of the battery, so I know it's charge state. I'd like a nearly automatic battery charger, for when I just want it to do the work. The PD9200 series looks fine for that. It will go to float mode, and won't harm the battery with its conservative settings, but when I'm camping, and know the exact charge state, I want a charger that will charge according to the recommended charge profile I don't mind setting it up exactly. Charge so many hours at constant 28 amps, then linearly drop the charge rate over a specified number of hours to 1-3% (2.2-6.6 amps) to get to 95% (or hold constant voltage over this period until the specified low current rate is reached), then hold that current rate until the last 5% is topped off.
Does anyone know of a charger that will let me set up a charge profile or at least one that uses the specified constant current rate charge for bulk charging?
Thanks for steering me towards any charger or converter/charger that might charge according to what Trojan recommends for this battery.
You actually probably want a 45 amp charger, sure it will put out 45 amps when the generator is first started, but this will not damage the Trojans. And not all 45 amps will go to battery charging. Once you have about 14.4 volts at the charger's terminals, the charger will start to reduce amperage, and drop way below 40 amps, down into the 30-35 amps range. Within 1 hour, it will be less than 30 amps, probably down around the ideal 25- 28 range.
Your converter probably is marked 40/5, that was typical of the era. It will put out up to 40 amps to run the RV loads, such as lights, water pump, furnace, ect. And has a circuit for charging the battery that has a maximum of 5 amps output. This is unregulated voltage output, so stay parked in a campground with 120 - 125 volts, and it will fry the battery. If in a campground with 110 volts or a little less, it will not get a decent charge overnight, or even in a week, because the output might only be 11.8 volts. And the 40 amp output is not regulated either, it might be anything from 12.8 to 15.5 depending on the input voltage, so it caused the light bulbs to overheat at 14+ volts and burn out frequently.
What I did on a class C was install a 45 amp charger, then cut the black wire going to the converter, and install a 120 volt receptacle in that same storage compartment. Plugged in the new charger to that receptacle, and put #8 wire from the new charger to the battery + and - terminals.
The old converter is still there, it has all the 120 and 12 volt fuses built into the cabinet it is mounted into. So it would have meant buying about $200 in new circuit breaker panels and fuse holders to remove that 45 pound boat anchor, so it stayed put.
You will not need the old converter (other than a fuse holder) and can leave it behind for that reason. Disconnect the wires, the new charger will do fine in overcoming the RV loads while also recharging the battery.
Or install some solar panels, and don't worry about running the generator. 100 - 120 watts will satisfy the very limited needs on your older RV. You don't have a huge load, modern RV's with propane and CO detectors typically use 35 AH daily, yours is probably less than 15 AH daily, and that is easy enough to make with the engine alternator in about 10 minutes.
sunelec.com has a few solar panels with 18 volt output that can go to a simple controller for $65. This will meet your needs.
I am dealing with a similar issue. I just got a great deal on some AGM batteries. On another thread I asked for some help about how to use them as a second house battery bank along with the golf cart batteries I have now. I found that the difficult part is that the AGM's have totally different charging requirements than the golf carts, and no converters that I could find would be able to properly charge those two types of batteries at the same time. The solution I found is to use a relay that isolates the AGM's from the system during charging. I have a Sears automotive charger that has a specific setting for AGM batteries. It will deliver 40 amps to the AGM's at the specific voltage that they need. The regular converter powers the house system and charges the golf carts. I replaced the Magnatek with a PowerMax 75 amp. converter.
Miles and Darcey
1989 Holiday Rambler Crown Imperial
Those Trojan charging recommendations for "long life" are not applicable to Rving where you want short gen times.
You have to get real and use the higher amp smart chargers (that don't hurt the batteries anyway) and forget all that happy stuff about long life, low amp charging.
A pair of 6v at 50% SOC can take an initial 80 amps easy. Amps will taper following the batteries' "natural acceptance rate" curve down as SOC rises once a threshold voltage is reached and held by the charger. The batteries and the smart chargers will take care of themselves, so don't worry about shortening their lives by any amount you will ever notice.
So it is all down to money and convenience whether to use say, two 40 amp VEC1093DBDs at once for 80 amps at $110 each (which is what I would do and keep the old converter for when on shore power) or buy an 80 amp converter or whatever (assuming you can ever find a converter that will do high voltage charging--good luck with that!)
2003 Chev 2500HD Gas, 2003 Komfort 26FS 5er
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, sure it will put out 45 amps when the generator is first started, but this will not damage the Trojans. And not all 45 amps will go to battery charging. Once you have about 14.4 volts at the charger's terminals, the charger will start to reduce amperage, and drop way below 40 amps, down into the 30-35 amps range. Within 1 hour, it will be less than 30 amps, probably down around the ideal 25- 28 range.
It's been my experience that a 45 amp charger won't charge a battery anywhere near 45 amps. Buying a 100 amp charger won't help either. A battery is just a load - like a light, except that the load varies depending on the charge in the battery and its AH capacity. The voltage applied to that load sets how much current it will take. The highest voltage I can hope for with the 9200 series converter charger is 14.4 volts, and if it works the way the patents says, I may not be able to get that (because it drops out of boost for various reasons) unless I manually force it into Boost Mode, and then I'll only get a maximum of 4 hours of 14.4 volts.
I can't figure this out. I can't get even one more sentence to upload, yet it lets me post this ?????
The chart doesn't even go as low as 14.4. volts. Whatever charge current I get at that voltage would be the same regardless of whether I bought a 40 amp charger or a 100 amp charger, and it will be less than the charge current I'd get between 14.7 and 16.7 volts.
* This post was
edited 05/07/12 08:58am by Magnetite *