Double Your Voltage or Runtime From 12 Volt Batteries

Today let's take a look at how to wire up your batteries in series or parallel to get the most out of them!

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[DonzLockz]

About 20yrs ago, I installed an SLA battery for a military site. It was 12v 200Ah and weighed 63kg. A literal back breaker! I'll take new LiFePo4 any day!

[carlleon]

Whether in series or parallel, you get the same total POWER (watts). In parallel 12V x 200Amps = 2400 watts. In series, 24V x 100 amps = 2400 watts. If you then step the 24V down to 12V (for amateur gear for example), you'll still get 2400 watts total (less any loss in the buck converter). As a ham, whose first interest is powering radio equipment, I stay at 12 volts. But if my primary concern was powering an inverter to get AC, I'd go with 24 (or 48) volts, as then my cabling needs would be less (lower amperage). Yet you still get the same life/longevity out of x number of watt hours.

[Frank_KFMH]

Another good one, TO!

One thing to remember for parallel recharging…each battery box has its own BMS, programmed to optimize the relative charge current to each individual cell. The two battery boxes in parallel can charge simultaneously as long as none of the separate sets of individual cells do not get too different from the others. This will indeed happen over time! Then, the vampire cell will get more charge current at the expense of the others, eroding the SOC for the other battery box. Long term: not so good for the batteries.

My attempt to deal with this was to unhitch the parallel cables and optimally charge each battery individually. PITA! When the price/ah came down in the lifepo4 world, I just bought larger cap batteries and repurposed the smaller units.

Interestingly, I stuck on a power monitor meter and a Powerpole cluster on each of smaller batteries … making very useful shorter-term power sources for a lot of situations…very lightweight!

[robertmeyer]

love them Mini Batteries ! Great for RV get more AH in small space. I charge them one at a time before connecting them. I set up a 24V Power queen battery for a RM italy 24V amp for a friend. they have great manuals ! so does REDODO . 73's

[WHNorthcote]

I did one some weeks back with 2 small 12V 7.4Ah slab batteries. These are the ones from security lights or those exit signs. I now have 12V 14.8Ah to take out. Maybe double the weight but they are quite good for the price as LiPo4 battery is a bit expensive at the moment in the UK.

[hazer]

I have a yellow Radio Shack VOM that I love because it's that compact/self contained.

[GerForever]

An alternative to tape is colored shrink tube to keep things neat

[KeepEveryGuessing]

If you have to charge at below freezing temperatures, lead acid isn't dead. But yeah.

And note, for series connection, the batteries need not have the same AH rating (or even the same chemistry). You will only get the AH of the lesser battery, but it is safe. I wouldn't charge them that way, as a rule. (Good for things like a 24V CPAP machine when camping.) For parallel connection, it had best be the same chemistry.

[Sylvan_dB]

In addition to planning your wire gauge to safely supply the current you need to draw, be sure to include a fuse small enough to protect the wire.

[nitekry]

Thanks, I just hooked up 3 240AH eco-worthy in parallel to the home power. I used 0/2, maybe I should use 0/4 but the batteries and leads are not even getting warm, so it may be okay. I may end up moving to 48v when I add solar, just not ready for that yet.

[victorcharlie]

Double the Power, triple the Fun! Looks like You're having a great day there in the Sun, tnx Man!

[GerForever]

Depending on brand. Not all LiFePO4 batteries are recommended to used in series or parallel. Some have great balencing, charging and protection circutry that may not work so well when connecting to other batteries.

[cornbread-KORN]

Safety First Boys, when connecting batteries always use your eye protection 😎👋wright

[EVPF]

you have a dually... you win ham radio youtube.

[ShooterReadyStandBy]

I run 2 15aH Miadys in parallel. Runs my 891 ssb all day.

[dougdaniels]

Great tutorial, you're correct, most manuals are lacking in this area. Regarding cable gauge, if I'm only running a 25A radio, I see that 12ga is recommended. It that for just the cables going to the radio, or can the cables between the two batteries also be 12 ga, or should those be more stout?

[RayDabkowski]

TO, How does connecting dual batteries affect the BMS in each battery?

[zercool]

love the video's .. I have 4 12.8v 20ah lifepo4 battery's wired in parallel so i have 80ah?? or 160ah? ECO-WORTHY 12V 20Ah Lithium Battery, 3000+ Deep Cycle Rechargeable LiFePO4 Lithium Ion Phosphate Battery with BMS for Trolling Motor, Fish finder, Kids Scooters, Power Wheels, Outdoor Camping

[dreupen]

Respectfully, what you state suggests that you do not have a clear grasp of electricity. Your first statements, "double your voltage or runtime" and "more power or longer running" are poor meaningless statements. For example, both the parallel and series configurations have the same power. Not more, not less! Power which is energy/time (units of Watts) is equal to Voltage*Current. The 2 batteries connected together have the same Energy (power*time) independent of a 2S series (26.4V*100AH=2640WattH) or a 2P parallel (13.2V*200AH=2640WH) connection. Your radio likely is not designed to operate on with a large spread of voltages and would likely blow a fuse at best if connected to 26.4V, but it could be fine if designed too(but would need more components and be more expensive). If it were designed so, then the load Current for the 2S (26.4V) would be half that of the 2P (13.2V). This is basic conservation of energy. Don't violate it. Let's say a radio that transmits 100W RF consumes 150W of total DC power when transmitting. Then the 2P combination would draw (150W/13.2V=11.4A) whereas the 2S combination would draw (150W/26.4V=5.7A) so that in both cases the power consumed (i.e. Energy) would be equivalent.

Also, the manual is hokey too with regards to wire sizing. One would use a large wire gauge to minimize the voltage drop due to the resistance of the wire itself. Total wire resistance is directly proportional to the wire length. Resistance R= rho * L/A where rho is the resistivity of the material(copper, iron, etc), L is the length and A is the cross sectional area of the wire. This states that if you double the wire length L, then you would need to double the wire area A to maintain the same resistance. I good rule of thumb is to keep the voltage drop along the wire length to less than 10%(i.e. Vdrop <= 0.1*Vbattery). With Vdrop = I*R, one can calculate R for a given battery voltage and Current load. And then given the length of wire one needs, determine a minimum wire size (i.e. A).   This is why 24V (or even better 48V) batteries are commonly utilized with DC to AC inverters. One needs 1/2 (or 1/4) the wire size compared to a 12V system (can be a HUGE $$$ saving) .

Sorry if I come across too pedantic.