Bestconverter ad says,"The PD9100L Series can be wired in parallel to charge at much higher current rates. They can also be wired in series/parallel to charge 36, 48, 60, 72 and higher voltage battery packs at high charge rates"I keep thinking about going 24v battery bank. I have several 12v converters (PowerMax brand) Reading the above, I am wondering how that would actually work.Say I put my adjustable 100 amper and my adjustable 55 amper in series to make a 24v charger. I would want the voltage to be 2 x 14.8, so I would set 14.8 on each.How many amps would that make to the battery bank? I am thinking 55 where you get the lowest amps (like with solar panels in series?) but that 55 with 24v is like 110 amps with 12v, so that is not too bad? Is that how it works? Or what? Thanks.

I highly recommend equally rated converters when in series.

I would have their voltages as equal as possible. If I don't mind just getting the lower of the two amps (55 and 100) what is the harm?EDIT--would I even get that 55 amps? With one charger same power, twice the voltage, half the amps. But here we have two chargers, total power is the same, twice the voltage, but how do they split the half amps ?

Converters in series act basically like batteries in series, assuming they are capable of being put in series. (If the DC output is not isolated from the chassis ground, for instance, they definitely won't work properly in series.) In both cases, the voltages add but the current is constant through both, as a straightforward application of Kirchhoff's current law would show.You would in theory max out at 55 amps or so. The power involved would, of course, be the current multiplied by the total voltage, ignoring conversion losses. The 100A converter would not be operating at full power output.If you don't need to be using the batteries while charging them, you would get faster charging by rewiring the batteries in parallel and operating the two converters in parallel because they could both operate at full power, assuming of course the batteries can accept that much charge current and the wiring is up to snuff and other such details are accounted for.

Hi BFL13,If you put a 2 amp charger and a 50 amp charger in series the output will be limited to 2 amps, just as it would for batteries.

"You would in theory max out at 55 amps or so. The power involved would, of course, be the current multiplied by the total voltage, ignoring conversion losses. The 100A converter would not be operating at full power output."If they were both 75 ampers at double the voltage then at the same full power, output would be 75 amps--37.5 amps each?So now we have 100 and 55, but ISTR in series you get the lower amps if they are not the same. But wouldn't that be 55/2 = 27.5?Meanwhile the 100 amper is still at 14.8v, making half the total voltage, but if it is not doing full power then what amps is it doing at how much of its full power?With both at full power, my Honda 3000 can just manage to run them making 155 amps at "12v" If somehow doing "24v" the 100 is doing less than full power, does that mean it is easier on the Honda?If so, maybe I could run my 75 amper and the 100 at 24v instead of the 55 and the 100, which the Honda can't do at 12v. If it can on 24v, then the lower amp charger (noow a 75) is higher amps so I would do better than with the 55? I really am confused.

Series 12v Chargers ? | Good Sam Community

BFL13
Explorer II
Jan 03, 2017
I Googled "stacking inverters" and got the info on that. Never mind.
pianotuna
Nomad III
Jan 03, 2017
Hi Mr Wizard,

Yes, for most of the thread, and that is usually safe to do.

MrWizard wrote:
PT
he is talking about stacking 'converters' aka chargers, in series
like solar panels in series

NOT inverters
BFL13
Explorer II
Jan 03, 2017
Naio wrote:
DrewE wrote:
you would get faster charging by rewiring the batteries in parallel and operating the two converters in parallel

Most of this discussion is over my head, but in case it is useful I will mention that you probably don't have to rewire to do this.

I have 2x12v gel cells running the 24v motor on my ice machine, and I have hooked them up to 2x12v chargers, one charger on each battery, a few hundred times over the past 10 years, without disconnecting the batteries from each other. Batteries are still perky.

When using non-identical chargers, I do swap which charger goes on which battery.

Ok, back to regularly scheduled :B

That works of course. Good point. It does by-pass the Trimetric monitor though, if that matters.
westend
Explorer
Jan 03, 2017
BFL13 wrote:
So it's not that horrendous in price to get a 24v inverter that would run the microwave, etc. (Not recommending, just noting the price)

http://www.boatandrvaccessories.com/powerbright-ml2300-24-inverter.html

Ask Bob in Denver about that inverter brand, they are Chinese junk.

Probably cheaper to go the higher amp DC-DC converter route and keep what you have: Victron DC-DC converter
MrWizard
Moderator
Jan 03, 2017
PT
he is talking about stacking 'converters' aka chargers, in series
like solar panels in series

NOT inverters
BFL13
Explorer II
Jan 03, 2017
So it's not that horrendous in price to get a 24v inverter that would run the microwave, etc. (Not recommending, just noting the price)

http://www.boatandrvaccessories.com/powerbright-ml2300-24-inverter.html
pianotuna
Nomad III
Jan 03, 2017
Hi BFL13,

You want to let the magic blue smoke out? Some inverters can be "stacked". Some can be in series, but most stacking is in parallel. The few I've seen require a sync cable to do so.

BFL13 wrote:

The big inverter is still an issue. Hmmmm can you use two 12v inverters as a 24 somehow? I have a 2000w and 3000w same brand MSW I could combine if so. Then just run a 12v converter (got some) from the inverter "bank" to make 12v for the rig.
BFL13
Explorer II
Jan 03, 2017
Thanks Mr Wiz. So everyone seems to agree, and I got my answers. Thanks everyone! Happy New Year!
MrWizard
Moderator
Jan 02, 2017
Mr Wizard, do you agree with the others like PT who say the 55 amper will be at 14.8v (as set) doing 55 amps while the 100 amper will be at 14.8v(as set) also doing 55 amps? (output 55 amps on 24v same as 110 amps on 12v)

yes provided the generator can supply it and the batteries will accept it

And if I swapped the 55 out and put in the 75 amper, it would do 75 amps and now the 100 amper would also do 75 amps? (output 75 amps on 24v same as 150 amps on 12v)

Yes .. same answer
BFL13
Explorer II
Jan 02, 2017
"Actually the 75 and 100 may work in series (24v) as each will only be at max 75 amps output. This is similar to the 155 amp 12v that seems to work."

That's what I have been trying to figure out from some calculations previously posted. The PFed 100 doing 75 should pull less VA than the non-PFed 75 doing 75. I figure 1279VA vs 1693 and total is 2972 doing 75 on 24v, much lower than the 3293VA total doing that 155a on 12v.

I'm kind of curious now to see if this would work, even though I am not planning on going 24v for now. Never know. It would save getting a new 24v converter if you could use the 12v chargers you already have.

The big inverter is still an issue. Hmmmm can you use two 12v inverters as a 24 somehow? I have a 2000w and 3000w same brand MSW I could combine if so. Then just run a 12v converter (got some) from the inverter "bank" to make 12v for the rig.

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