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We purchased a cabin that came with a 12V solar system. The battery bank is comprised of 8 x 6V Trojan T-105s in 4 parallel strings of 2. I know you're not supposed to exceed three strings, but we inherited this configuration. We have a 7500W dual-fuel generator (we use propane) that feeds into 2 x Iota DLS-55 AC/DC converters, which then feed into the bank. How long should it take to charge the bank from 12.0V to full?
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.Should charge pretty quick. If the chargers really charge at 110 amps together and the batteries never go below 50%, then three hours should nearly charge them. You have around 440 ah of usable power, 880 ah total. 3 Hours charging will get you 330 ah.
Now for some problems. THe batteries will start in bulk mode dumping as much amps as it can into it. I’m not sure what that point is, but maybe its at 100 ah. So that last hour looks like charging will take an hour, but takes a bit longer as the charger stops pushing 110 amps and goes to 0.
THere’s some good stickies on how batteries charge. Bulk = Constant Amperage as volts go up to SCC programmed charging voltage. Once this voltage is reached the charger enters absorption, volts stay steady, and amperage slows until the battery is charged. The final part is going to a lower float voltage.
I have a battery monitor that tracks better than measuring voltage. If you don’t have a monitor, try a hydrometer test, also in the stickies.
The other problem with the Iota 55 amp, is it may not deliver the full amperage. On another forum, someone posted he did not see that 55 amps. This will slow it down. Seems if you want higher than a 55 amp charger, you need to get a 20 amp plug.
I got this document from Mike at this forum to show to how to correctly wire parallel batteries:
Last edited by chrisski; 05-28-2021, 10:52 PM. -
Thanks for the feedback! 3 hours is about how long we typically run the generator. The weird part is that we don't seem to get much energy back from the batteries. Our heat, water heater, and fridge are propane. The only things we power with electricity are LED bulbs, a TV, personal electronics, wireless router, and small USB fans. We connected a Kill-A-Watt to the output port of the 2000W inverter, so I know that our whole cabin only draws about 150-250W even with every light and device in the house turned on. But a 3-hour run of the generator only buys us about 8 hours of battery life before the meter is flashing 12.0 again. The T-105's are 2 years old and I've watered them every 3 months or so. The level has never dipped low enough to expose the plates, and I am pretty religious about not letting the voltage meter drop below 12.0 (although I confess to accidentally letting it get as low as 11.6 a few times).
I'll definitely re-wire my bank using the method described in the document you provided.
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