Charging batteries

[Go_Dawgs]

I think my Intellipower 9200 converter/charger is toast on our AF990. I need to get a multimeter to verify but in the mean time I unplugged the converter from the 110 outlet that it is plugged into (when connected to shore power) and the outlet is fine and in working order.

In the mean time I have a question on charging the batteries. I have two group 27 batteries wired in parallel in the camper. Since my inverter/charger in bad and does not charge them when I am plugged into shore power can I simply hook up my 15amp Stanley battery charger directly to one of the batteries? Do I need to disconnect the batteries individually and charge them individually? Or can I just hook up my charger to one of the batters and both batteries will charge?

Also, I have a battery disconnect switch under the sink, should I flip the disconnect switch while charging? I wouldn't think that would be necessary.

So far I have left the batteries as is (connected and wired in parallel) and not bothered with the battery disconnect switch. I have hooked up the charger to the front batter and let it charge. Once the batteries are fully charged the charger goes into a trickle charge mode. Everything seems to be ok, running fine but I figured I should ask and get some opinions.

Thanks for the help,
JT

[jimh406]

If these are the original batteries, I'd also consider a bad or both batteries as bad.

[Go_Dawgs]

I checked and replaced the two fuses on the inverter/charger. The originals were fine but I changed them anyway. Supposedly the fuses will blow only when the batteries are hooked up in reverse. The outlet that supplies power is in working order too.

[Paradox123]

Before you buy a new Intellipower, make sure it's not just a blown fuse or breaker. I'm going through the same thing and the converted seems to be working fine. I'm looking for a bad fuse now.

[Go_Dawgs]

Ouch on the Husky jab! You know we are opening our renovated Husky Stadium in a little more than a month!

[Mello_Mike]

And we won't hold it against you that you're a Huskies fan. 🙂

[Go_Dawgs]

Thanks for all the replies. I do leave it plugged into shore power at the house ans when it is stored. According to Progressive Dynamics (who makes the converter/charger) it has a built in "charge wizard" that constantly monitors the batteries to determine and then goes into one of four charging modes (boost, normal, storage and desulfation).

Mainly I wanted to make sure I wasn't doing something that was inadvertently damaging something. I just ordered a new converter/charger so once I get that in it should be good to go.

Thanks again for the replies,
JT

[mkirsch]

Connect the charger + to the + on one battery, and the charger - to the - on the other battery.

That's how you'd hook up two batteries in parallel to draw from them balanced. I can't see why it wouldn't work/help/whatever for charging.

[Jeepers92]

Actually, parallel charging is what unbalances the batteries. The charger makes decisions on the voltage it sees. It only sees the parallel voltage and not individual voltage. Read your batteries parallel (open circuit)'. Then disconnect a parallel leads and read each battery separate. The ideal way is to have both batteries the same age, manuf,manuf date,etc. In an RV, the best practical solution is have the batteries matched as close as possible, charge them individually with a good charger before installing them, assure your on board charger is working correctly, ( not overcharging or undercharging ), and balance them periodically. There are huge differences in batteries from different manufactures. There are diff in charge profiles from chargers. There are differences in weather, how much the batteries are cycled, do you leave your camper plugged in while stored, etc. The most elaborate method of charging was electric vehicle systems. The chargers had sensors which measured each battery for voltage and temp. The sensors based computer would vary the charge to each battery ( very small amounts ) to keep the batt voltages balanced. I retired 3 years ago so I am sure that may have changed by now.

[KD4UPL]

The best way to keep your batteries balanced, that is, a matched set, is to treat them as one battery. Leave them connected in parallel all the time. Discharge them and recharge them as one. There should be very little chance for an imbalance to occur.

[Super_Dave]

I don't know if this relates to unbalanced or not but I was told that a charger hooked up to one battery connected in parrell to another will be over charging itself while charge is passing to the second battery. Hence, the recommendation to charge them individually. Another possible way to do it would be to mount a dual bank battery charger like I use on my boat. It is a smart charger and evaluates the charge on each battery as to when to go into trickle mode. For instance, my current charger is a variable 20 amp charger and will send more juice to the weakest battery until it has caught up.

[bobndot]

quote wrote:
When batteries are parallel charged, the more unbalanced, the shorter the life.

Hi, This seems like a good idea,to balance the batts from time to time. So one battery is not fighting the other.
If someone does this with a two 12 v. battery bank and finds one of the batts to be 'off the mark' , i would think both batts would need to be changed ??? or is not correct ?
In other words, can i use this as an excuse to buy myself two new camper batteries and use the leftover good one for my trolling motor :@ir

Im only asking this question because some people say batts should be of equal size and age.

Bob

[Jeepers92]

You can charge parallel, that's the on board works. It is best to charge each individually. You can unhook the parallel wire between the two pos connectors then charge each battery individually. You want the two batteries as balanced as possible. Charge both individually, let set for 5 min after the last bat is charged, then check with voltmeter. The voltages should be close. While charging with an external charger, disconnect the battery from the on board by turning off batt switch located under the sink. When batteries are parallel charged, the more unbalanced, the shorter the life. If cutoff on the charger is 14 volts, that can be 16 on one and 12 on the other. They will try to balance on discharge, but the more cycles, the more out they get. It's a great idea to balance them every year.

[Raften]

Just hook the charger up. That is pretty much how your converter charges them.