Two chargers on same battery

[Snowman9000]

I recall BFL (I think it was) saying he could use the Vector 1093 on a battery while it was also being charged, albeit feebly, by the stock converter charger.

We dry camped all week, with no solar, so I had to run the Onan 4000 to charge. I was using a Wal-Mart B&D 40 amp charger, which is not their version of the 1093, but something a bit cheaper, I think. Nevertheless it's supposed to be smart, has a desulfate button, amp display, all that.

My charging routine was the same thing every day. In the morning I'd be at about 12.1v. Some days, the big charger worked fine along with the built in 7355 running. But a couple of times, the big charger reported Battery Fully Charged after just a couple of minutes. I had to shut off the 7355 and start again with the big one.

By itself, the battery voltage when the B&D was running was 14.6. When the 7355 was running by itself, the voltage was 13.2-13.4 (poor wiring). On the days when the B&D was not bothered by being paired up, the charging voltage was again 14.6.

What's the scoop on using two chargers?

[MEXICOWANDERER]

VERSUS





Which one is more likely to deduce? Which one is more likely to be suspicious? Which one can be programmed erroneously by someone living 40 miles outside Bombay that has never seen a deep cycle battery?

[time2roll]

BFL13 wrote:
Always get the portable smart charger running first, then apply the converter.

+1, this is the scoop.

[BFL13]

Snowman9000 wrote:
..........

I tried turning off the converter but they've wired some outlets to the same breaker, so we had issues. I intend to change that too.

Off-topic, but this will also help when plugging shore power cord into the inverter for "whole house." You must turn off the converter but you don't want to also turn off the receptacle circuit which is on the same breaker as the converter.

You can also instead insert a switch in the black wire coming up from the converter to the breaker before it joins with the receptacles' black wire. Now you can leave the breaker on so the receptacles work and just turn the converter on or off with the switch. I used a regular stick house light switch. (before mounting, check which way is off and have that pointing down 🙂 )

[wa8yxm]

There are two "Worst case" Seneraos.. I will describer them both.

Batteries and chargers connected properly: WOrst case is one charger works, the other idles

Batteries and chargers connected wrong (one or both connected backwards) Worst case is excape of magic smoke (you blow a converter.... or two).

But that second case applies with just one converter/charger as well.

[mbopp]

From a previous HTT I had a deck-mount IOTA-55 w/ IQ4 controller (HTT came with a "dumb" single-stage Elixir.) The new TT has a WFCO converter, not known for going into boost mode easily. The IOTA seems to start in boost mode whenever it's first turned on.
The IOTA got mounted to the ceiling of the front pass-through and it's a hard-wired 3' cable run to the dual G27 batteries. For 110V I tapped off a front bedroom outlet and fished a cable to a switched outlet for the IOTA. In the home parts box I had a compatible breaker for the WFCO so it got put on its own circuit. Now I can turn either or both converters on & off.
With cg power I run solely on the WFCO. For charging off the Honda 2000i I flip the disconnect switch on the batteries. The TT 12V circuits now run off the WFCO and the full boost output of the IOTA goes to the batteries. And since the WFCO isn't in boost mode the TT 12V side doesn't see the high boost voltage.
OK, it may be overkill but it works for me.

[Snowman9000]

BFL13 wrote:
Always get the portable smart charger running first, then apply the converter.

I don't try to get the 1093 and the 7355 to work together to add their amps since the 7355 does not add much to the job with its much lower voltage than the 1093's. Instead, I use the battery disconnect and run the rig on the 7355 for 12v stuff while charging the batts with the 1093.

This means there is no draw from the rig subtracting from the charging and making it take longer. eg, say there is a 5 amp draw from the rig. 40 amp charger at 40 amps. Net charging is 35 amps instead of 40.

Ah, that makes sense. If I had thought about it for many days, I might have realized I should simply turn off the battery disconnect to solve my problem.
🙂

I tried turning off the converter but they've wired some outlets to the same breaker, so we had issues. I intend to change that too.

[RoyB]

This BATTERY MONITOR PANEL I made up saves me big time knowing what is going on when camping off the power grid.

I have two battery banks connected together with BLUE SEA battery four position switches.

The BANK1 and BANK2 is looking at each BANK on the battery side.

The DC AMPS is feeding the battery bank switches.

With this arrangement I can work with either battery bank at a time and can see what DC current is going into the batteries or being drawn from the batteries.

Sometimes I use the on-board converter/charger on one battery bank and the portable B&D 1093 on the other battery bank...





I have never really put the B&D 1093 in parallel with the on-broad PD9260C but it should not harm anything...

By always never letting the batteries get below 12.0VDC (approx 50% charge state) I never run into into a problem where my B&D1093 will not stay in its selected mode. I have seen if a battery is real low you have to start out charging at a real low rate for period of time to get it charged back up to a certain point before the B&D will start charging for you. i.e. work your way back up... usually a battery is dead and won't start building up a charge at this point...

I normally re-charge all the time using the PD9260C and only have the B&D 1093 around for a PLAN B backup when camping off the power grid.

I have rescued many folks including myself with my truck bed mounted 2KW generator and the B&D 1093 portable battery charger plugged into it.

Roy Ken

[BFL13]

Always get the portable smart charger running first, then apply the converter.

I don't try to get the 1093 and the 7355 to work together to add their amps since the 7355 does not add much to the job with its much lower voltage than the 1093's. Instead, I use the battery disconnect and run the rig on the 7355 for 12v stuff while charging the batts with the 1093.

This means there is no draw from the rig subtracting from the charging and making it take longer. eg, say there is a 5 amp draw from the rig. 40 amp charger at 40 amps. Net charging is 35 amps instead of 40.

For multiple chargers on the same battery, you get better results (adding their amps) when the chargers are of similar voltage. You could use two 1093s and get 80 amps that way. I routinely ran four Vector portables on one battery bank to get a total of 130amps in bulk. ( a 40, two 35s, and a 20) 130 was the most the Honda 3000 could do before popping its breaker. ( if I changed the third 35 up from the 20 amp setting to 35, that would blow the Honda)

BTW, the two chargers will not total any more amps than the battery will accept. So if the batt acceptance rate at that voltage is 60, then the two 40s will do 30 each. Or if one charger has a higher voltage than the other, then it might be 40 and 20 say. Then (with two 40s of same voltage) when down to 40, each is doing 20. At that point you might as well yank one charger and the other will bounce back from 20 to 40 and continue on down.

[Snowman9000]

Thanks. I know the wiring problem: too long, too skinny.
I have the Sears clamp meter, that's how I got the amps on the 7355. I was taking the voltage across the battery terminals.

My question is, why did the B&D work fine most days, but a couple of days it saw the battery as fully charged right away, when the 7355 was charging?

[MNtundraRet]

You answered your own question. Get the wiring from the built-in charger checked out. 13.2 to 13.4 volts is not charging. It's only in maintenance mode.

Loose or corroded grounds, connections, or undersized wires, cause the converter/charger to think the battery-bank is charged.

Multiple charging source is normal for modern RVs. Solar-panel + generator running converter/charger + alternator from MH while driving.

A clamp-meter is nice for checking amps being supplied from each source while charging. While using your BD charger at the same time, if the total amps add up to more than the best single source you are gaining ground using more than one source.

By the way most voltage readings are taken across the battery-bank terminals. A reading below 14.4 volts early on does not necessarily mean the amp output is low and not in "bulk" mode. That's why ability to read amps is better when charging.