Converter/Charger Output

[Country Campers]

A question has arose in a conversation that I thought might be a good one to ask here.

If the converter/charger output is say 100 amps, Will this be split between 2 batteries, only 50 amps going to each battery?

I realize that there is amps being used by the RV but this is just to keep it general.

Brian

[TedS]

Only if the batteries' internal resistances are equal.

[howson]

Country Campers -- are those two batteries in parallel or in series? In parallel (keeping it simple) the answer is "yes", the current is split between the two batteries. If in series, the 100A current is supplied to both batteries. (Think of a setup with two 6V batteries.)

[TedS]

howson current still depends on resistance. In parallel they will see equal voltage, maybe not equal current unless internal resistances are equal. I = V/R

In series they not see equal voltage drop at the same current if their internal resistances are not equal.

Battery health will make a difference.

[Yoda]

A question has arose in a conversation that I thought might be a good one to ask here.

If the converter/charger output is say 100 amps, Will this be split between 2 batteries, only 50 amps going to each battery?

I realize that there is amps being used by the RV but this is just to keep it general.

Brian

Great answers above. Lost a few more gray cells remembering here. So the real answer is it depends, ..just kidding However you do need to be careful on the charging current. All batterys are different on what the max charge current can be, and usually have a optimal charge rate. Best to read the battery specifications first.

There, I have now exhausted what I know on battery charging.

Keith

[howson]

howson current still depends on resistance. In parallel they will see equal voltage, maybe not equal current unless internal resistances are equal. I = V/R

In series they not see equal voltage drop at the same current if their internal resistances are not equal.

Battery health will make a difference.

Of course...but Brian's post did say to keep it simple. At a basic level, current is the same throughout a series circuit.

[Dave27]

I have been wondering about this question. I am planning to change to lithium batteries. I am looking at SOK 12V 206AH LiFePO4 batteries. The maximum charge rate is 70 A. If I only get one, I assume I should not get a 100 A converter/charger, that a 55 A would be safer. But if I get two and wire them in parallel, then each would only "see" about 50 A (I realize if the internal resistance was slightly different between the two, the split would not necessarily be equal). I would like to get a 100 A converter/charger, the batteries should recharge much faster, and if I'm using a generator, I like to minimize the time running it. But I am concerned if one of the batteries malfunctioned, and I could only use one, would I be able to use a 100 A converter/charger on it?

Thanks,
Dave

[TucsonJim]

Remember that most of the converter/chargers are "smart". As a the battery charge increases, the voltage or current starts to decrease depending on the type of charger. A converter charger won't be cranking the maximum current unless the battery is completely dead.

Another consideration. Make sure that you never install a converter charger with more current capability than the OEM version unless you increase the wiring to the appropriate size.

Jim

[Scott'n'Wendy]

. I would like to get a 100 A converter/charger, the batteries should recharge much faster

Wiring to support high amperage becomes very costly......not saying you can't do it....just to do it correctly, the big wire size to support it aint cheap.

[TucsonJim]

Wiring to support high amperage becomes very costly......not saying you can't do it....just to do it correctly, the big wire size to support it aint cheap.

Exactly. A 100 amp circuit with a run of 30 feet (out and back) will require a minimum of 4 AWG wire and will have a 10% voltage drop. That same 30 foot circuit will require 0 AWG with a 3% voltage drop. (Source: Blue Sea current table).

Jim

[Dave27]

TucsonJim Scott'n'Wendy Country Campers Thank you for the comments about wiring size. When I installed the solar system five years ago, I upgraded my converter/charger to 60 A, I moved it close to the batteries, and I used 2AWG to connect the batteries (two Trojan 6v), inverter (300W), and charger. I didn't change any other wires distributing power to the camper. I put a 100A fuse on the batteries. Do I need to be concerned about any other wires in the camper? Here are photos of my setup.
Thanks, Dave

[AlexPeterson]

I have been wondering about this question. I am planning to change to lithium batteries. I am looking at SOK 12V 206AH LiFePO4 batteries. The maximum charge rate is 70 A. If I only get one, I assume I should not get a 100 A converter/charger, that a 55 A would be safer. But if I get two and wire them in parallel, then each would only "see" about 50 A (I realize if the internal resistance was slightly different between the two, the split would not necessarily be equal). I would like to get a 100 A converter/charger, the batteries should recharge much faster, and if I'm using a generator, I like to minimize the time running it. But I am concerned if one of the batteries malfunctioned, and I could only use one, would I be able to use a 100 A converter/charger on it?

Thanks,
Dave

The converters or chargers should be thought of as a voltage source with a maximum rated current. Lithium chargers typically have 2 voltage stages, while lead acid chargers perhaps 3. The battery itself "decides" how much current it will draw based on its state of charge and the applied voltage (some of this "deciding" is the battery's basic chemistry while some of it is the battery management system, in the case of lithium).

It would be ok to hook a 12v charger with 1000 amp capacity to a 12v battery which has a 50a max charge current, the battery would not know if it is a 50a or a 1000a charger, as long as the voltage profiles are correct for the battery voltage/chemistry.

As others have noted, the wiring would need to be upgraded if you upsize the amperage from stock.

[Scott'n'Wendy]

Wiring to individual loads within the trailer are fine as is. I was only referring to the wiring from power source to battery. And perhaps battery to inverter if you are so equipped.

[Dave27]

TucsonJim Country Campers howson
What size fuse is needed for two 206AH lithium batteries? I ordered 2 SOK batteries. I checked my wire sizes, and I used 2AWG when I put in my solar system. So they can handle 100 A easily. I talked to PowerMax today, and I feel comfortable with how their charger works. I think I will order the 100A, as soon as I figure out what size fuse I need. Do I need a fuse on each battery if they are wired in parallel?

Thanks,
Dave

[howson]

Dave27 -- what PowerMax model? Usually the manual has specific recommendations for fusing and wire sizes (not forgetting the length of the wire is also a consideration).

The number of batteries in parallel is not a consideration for the fuse. Think of it in terms of a water tank connected to a standard RV pump. Given there's water in the tank the pump will push X amount of water through over Y time. Just because an additional tank is added (or a larger one is installed) the pump will still push the same X amount of water over Y time. The only difference is the pump will do it longer since there is more water available. Same with the battery bank. What's connected to the batteries (charger, inverter, etc) and the most critical consideration--wire size--determines the fuse. If I remember correctly 25% over the maximum sustained current expected is the fuse rating (google will know).