Batteries in parallel

[blindfire]

Hello brain-trust.

What is the easiest way to wire 4 batteries with this type of connector in parallel and then would allow me to hook into my radio.

I have the ability to use power pole connectors as well as standard wire connectors.

 

[jtnf]

No pics, Chrome as the client. Is Imgur still having issues?

 

[FreeWillie]

No pics with Firefox

 

[Chet0729]

I would use good spade connectors and bind the other ends together to some sort of connector for the radio.

 

[mibro]

The 100% kosher way to do it would be with AMP PIDG piggyback Fastons. You would need the correct crimp tool. I buy this kind of stuff from Mouser Electronics which has no minimum order and low shipping costs.

 

[Goliathan]

Fast-Ons.

You can use regular female ones and double-crimp wires into them:
http://www.digikey.com/product-detail/en/2-520183-2/A27817TR-ND/289249

Or you can use female/male ones and daisy chain them using single-crimp pigtails:
http://www.digikey.com/product-detail/en/62253-2/A27634CT-ND/456726


Edit: mibro beat me to it!

 

[quincy]

Probably not a good idea to wire batteries in parallel. If the voltage is not exactly equal, you will get current flow from the higher to lower voltage battery and heat. Series is good.

 

[Sparkey]

Probably not a good idea to wire batteries in parallel. If the voltage is not exactly equal, you will get current flow from the higher to lower voltage battery and heat. Series is good.

I would assume the OP is looking for more amperage that is why he would wire in parallel I assume they are 12 volt batteries if you wire themin series heis going to get 48 volts.

 

[BenDover]

Batteries in parallel is fine...4 of them might be a lot. Personally I would opt to just buy a marine battery if you need more AH. Perhaps the OP has space restraints? Or just has the batteries?

Make sure they are all the same AH rating and fully charged before connecting them together. You might also run a capacity test on each battery to make sure they are reasonably well matched. An 1157 bulb, dvm, and stop watch and you can do a crude test.

If you have power pole connectors you could snap them into an 8 conductor plug/socket. The advantage is that you disconnect the batteries from each other when the plug is disconnected. If you share the (-) lead you could also do it with just a 5 conductor plug.

 

[Another_David]

The 100% kosher way to do it would be with AMP PIDG piggyback Fastons. You would need the correct crimp tool. I buy this kind of stuff from Mouser Electronics which has no minimum order and low shipping costs.

that works.

you could also use a terminal block with jumpers, which is more parts but IF you're feeding multiple components it's a neat way to keep power distribution organized and not just have a ball or wires looking at you (don't forget the jumpers). Use multiple colored wires and get all fancy!:

http://www.mcmaster.com/#terminal-blocks/=8ius925eouikdazqwr

many other styles to choose from: http://www.mcmaster.com/#terminal-blocks/=1110kme

and yes, the crimper is the most expensive part if you don't already have one

You Do It electronics in needham will have some of this stuff.

 

[blindfire]

Batteries in parallel is fine...4 of them might be a lot. Personally I would opt to just buy a marine battery if you need more AH. Perhaps the OP has space restraints? Or just has the batteries?

Make sure they are all the same AH rating and fully charged before connecting them together. You might also run a capacity test on each battery to make sure they are reasonably well matched. An 1157 bulb, dvm, and stop watch and you can do a crude test.

If you have power pole connectors you could snap them into an 8 conductor plug/socket. The advantage is that you disconnect the batteries from each other when the plug is disconnected. If you share the (-) lead you could also do it with just a 5 conductor plug.

Space is an issue. Trying to build s mobile box. Probably can get away with 2 in parallel. They are 12V batteries. 15AH.

They shipped charged and the two I've tested so far show 12.7V +/- .05

I like the piggy back faston option. Will run with that.

Thanks guys!

 

[AHM]

Space is an issue. Trying to build s mobile box. Probably can get away with 2 in parallel. They are 12V batteries. 15AH. ...

This point remains open:

Probably not a good idea to wire batteries in parallel. If the voltage is not exactly equal, you will get current flow from the higher to lower voltage battery and heat. ...

Design to account for potential heating effects from differential discharge or risk a fire. That's not a foregone conclusion. However, the more the batteries differ by lot, prior usage, make/model, and technology, the greater the risk:

Can I Connect Dissimilar Batteries in Parallel?

Adequately sized wiring, individual fuses/breakers and isolation diode networks can address issues:

Parallel Operation of Lead-Acid Batteries

At the very least, don't scrimp on the wiring harness between the batteries, and fuse each separately with a fuse rated below the wiring's current capacity, so that the wires don't burn up in order to protect the fuse...

Also, how will the batteries be wired during charging?

• Separately?
• While wired together?

and how will the batteries be charged?

• Throwing them across a DC power bus (13.8V?) permanently?
• ... just occasionally?
• Using a three-stage trickle charger?

Battery University BU-403: Charging Lead-Acid

Offhand it seems to me that if and when parallel batteries drift apart in characteristics, three-stage smart chargers are more likely to be mislead, and supply voltage/current/float mismatched to some of the batteries. I don't see it discussed, but it's something to consider.

Here's some guy in 1999 obsessing over buying the most appropriate Schottky isolation diodes:

Wiring 2 lead-acid 12v batteries in parallel -- safety questions

He eventually went without rather than solve the problem. I don't know whether the specific components are still sold, but DigiKey and Mouser remain in business.

P. S. The Apollo Command/Service Module could potentially connect two batteries to the same power bus: Electrical Power System (CSM): DC, but could only charge one battery at a time: Electrical Power System (CSM): Bat charger. Maybe that's how silver oxide-zinc batteries roll...

73's

 

[blindfire]

This point remains open:



Design to account for potential heating effects from differential discharge or risk a fire. That's not a foregone conclusion. However, the more the batteries differ by lot, prior usage, make/model, and technology, the greater the risk:

Can I Connect Dissimilar Batteries in Parallel?

Adequately sized wiring, individual fuses/breakers and isolation diode networks can address issues:

Parallel Operation of Lead-Acid Batteries

At the very least, don't scrimp on the wiring harness between the batteries, and fuse each separately with a fuse rated below the wiring's current capacity, so that the wires don't burn up in order to protect the fuse...

Also, how will the batteries be wired during charging?

• Separately?
• While wired together?

and how will the batteries be charged?

• Throwing them across a DC power bus (13.8V?) permanently?
• ... just occasionally?
• Using a three-stage trickle charger?

Battery University BU-403: Charging Lead-Acid

Offhand it seems to me that if and when parallel batteries drift apart in characteristics, three-stage smart chargers are more likely to be mislead, and supply voltage/current/float mismatched to some of the batteries. I don't see it discussed, but it's something to consider.

Here's some guy in 1999 obsessing over buying the most appropriate Schottky isolation diodes:

Wiring 2 lead-acid 12v batteries in parallel -- safety questions

He eventually went without rather than solve the problem. I don't know whether the specific components are still sold, but DigiKey and Mouser remain in business.

P. S. The Apollo Command/Service Module could potentially connect two batteries to the same power bus: Electrical Power System (CSM): DC, but could only charge one battery at a time: Electrical Power System (CSM): Bat charger. Maybe that's how silver oxide-zinc batteries roll...

73's

WOW! Thanks for this info. I guess I still have a lot to learn and decide.

I have a charge controller and will probably charge each battery separately to remove any potential for bad things happening.

Perhaps I am being cheap here. Maybe I should have gone with a larger capacity deep cycle marine battery and work around the size constraints instead of going with a smaller set of batteries in parallel to accomplish the same task.

Thanks!

 

[ToddDubya]

This isn't a unique problem. People with solar systems have lots of large batteries in parallel. It sounds like you have four of the same battery, which will only help with balancing and safety. Personally, I would charge them together just as you intend to use them. This will help keep them balanced. Some chargers will also handle the balancing for you.

Wikipedia article on battery balancing: https://en.wikipedia.org/wiki/Battery_balancing

 

[mibro]

This isn't a unique problem. People with solar systems have lots of large batteries in parallel. It sounds like you have four of the same battery, which will only help with balancing and safety. Personally, I would charge them together just as you intend to use them. This will help keep them balanced. Some chargers will also handle the balancing for you.

Good advice. Connecting two or more identical batteries in parallel should not be a problem. Charging them in parallel should also not be a problem. The batteries will self-equalize.

 

[n1bsbri]

Good advice. Connecting two or more identical batteries in parallel should not be a problem. Charging them in parallel should also not be a problem. The batteries will self-equalize.

This, the non-overthinking it solution.

 

[economist]

If the idea is significant current supply in a small package, check out LiPo batteries used in RC applications. They will be overkill for any reasonable amount of run time and come in a huge range of shapes/sizes. Downside is that charging requires some care and excessive discharge can ruin the battery.

 

[AHM]

WOW! Thanks for this info. I guess I still have a lot to learn and decide. ...

I concede that cemeteries aren't littered with headstones that say "He connected batteries in parallel". But it strikes me that at the very least the interconnects have to be sized more stringently than the harness running to the rig, because the issues are more subtle.

---

This isn't a unique problem. People with solar systems have lots of large batteries in parallel. It sounds like you have four of the same battery, which will only help with balancing and safety. Personally, I would charge them together just as you intend to use them. This will help keep them balanced. Some chargers will also handle the balancing for you.

Wikipedia article on battery balancing: https://en.wikipedia.org/wiki/Battery_balancing

Thanks - nice existence proof; good grist.

 

[richc]

 

[BenDover]

My house runs on a pair of deep cycle marine batteries (120-140 AH typ). The only precaution I take is to fully charge them independently, make sure they have the same date code. When I first connect them together I connect the (-) terminals, then use an amp meter to make the (+) connection. I have never had more than an amp or two flowing and that settles out after a few minutes. From that point on they are charged and discharged as a bank. I've been thru 3 sets of batteries in the past 4 years and never had a problem.

 

[Chet0729]

It wont make any difference if they are not close in voltage just so long as they are all rated at the same voltage. We had a few of these home made packs to run inverters that we used to charge off the car when it was running and the batteries normalized pretty quickly. The only thing I will caution you on is 4 in parallel are going to have a lot of current available. Make sure they are fused properly and the wire size is appropriate for the total amperage. 60AMPs is going to require at least 8 gauge wire to be safe. If you do 4 15 amp in parallel that is 60amps that would be available.

 

[blindfire]

It wont make any difference if they are not close in voltage just so long as they are all rated at the same voltage. We had a few of these home made packs to run inverters that we used to charge off the car when it was running and the batteries normalized pretty quickly. The only thing I will caution you on is 4 in parallel are going to have a lot of current available. Make sure they are fused properly and the wire size is appropriate for the total amperage. 60AMPs is going to require at least 8 gauge wire to be safe. If you do 4 15 amp in parallel that is 60amps that would be available.

Ok, I was wondering about that part. I'll google it, but if you can suggest a site or something that discusses gauge vs current, that would be great.

ETA: I found this: http://www.powerstream.com/Wire_Size.htm
Is that an accurate table? If so, do I use the chassis wiring column or the power transmission column for determining proper gauge?


Thanks.

 

[Goliathan]

Parallel batteries will self balance if they're close in voltage, but you do want to make sure they're the same age to begin with, as charge/discharge profiles can change dramatically over their life.

It's not ideal and certainly not how I would design a system, but you'll probably get away with it.

 

[Goliathan]

I found this: http://www.powerstream.com/Wire_Size.htm
Is that an accurate table? If so, do I use the chassis wiring column or the power transmission column for determining proper gauge?

It may be tricky finding connectors for 8AWG wire, and the wire itself it going to be expensive. What's your actual expected current load? I'd recommend sizing your wiring and fusing for that (with a bit of headroom) instead.

 

[blindfire]

It may be tricky finding connectors for 8AWG wire, and the wire itself it going to be expensive. What's your actual expected current load? I'd recommend sizing your wiring and fusing for that (with a bit of headroom) instead.

Basically, I'm looking for extended run time on my radio (Kenwood TM-281)...and MAYBE and I say maybe...a amp...but that is overly optimistic.

 

[Goliathan]

Basically, I'm looking for extended run time on my radio (Kenwood TM-281)...and MAYBE and I say maybe...a amp...but that is overly optimistic.

Well, transmit power is going to be quite a lot higher than standby/receive power, so if you want to cover that, bump up to like 16AWG or 14AWG and 15 amp automotive fusing and I think you'll be all set. Fastons do come in different tab widths so make sure you measure your battery tabs. At a glance, those look like 0.187" to me.


EDIT: If I've guessed right about the tabs, these should do you:

http://www.digikey.com/product-detail/en/1217151-1/A100450CT-ND/2233326

 

[Another_David]

Basically, I'm looking for extended run time on my radio (Kenwood TM-281)...and MAYBE and I say maybe...a amp...but that is overly optimistic.

looks like no more than 14 amps: http://www.universal-radio.com/catalog/fm_txvrs/0281spec.html

I would use 14 gauge solid copper, which is what is typically used for 15 amp household circuits.

Don't connect or disconnect anything while the unit is powered on and certainly not while transmitting.

Using a factor of 1.5 time max load, you'd probably want about a 20 amp fuse.

 

[ToddDubya]

looks like no more than 14 amps: http://www.universal-radio.com/catalog/fm_txvrs/0281spec.html

I would use 14 gauge solid copper, which is what is typically used for 15 amp household circuits.

Don't connect or disconnect anything while the unit is powered on and certainly not while transmitting.

Using a factor of 1.5 time max load, you'd probably want about a 20 amp fuse.

Keep in mind that you still want fuse protection for each device. So overall you might use a 30A fuse but your radio might have a smaller 20A fuse, any tuners/amps would have their own fuses, etc. just like your house has a main breaker and individual breakers for smaller circuits. Some devices may have their own built-in fuses.

Oops, I see that what I'm quoting is for just the radio itself and that's all you plan to run.

 

[AHM]

My house runs on a pair of deep cycle marine batteries ... When I first connect them together I connect the (-) terminals, then use an amp meter to make the (+) connection. I have never had more than an amp or two flowing and that settles out after a few minutes. ...

Nice quantitative sanity check.

---

Ok, I was wondering about that part. I'll google it, but if you can suggest a site or something that discusses gauge vs current, that would be great.

ETA: I found this: http://www.powerstream.com/Wire_Size.htm
Is that an accurate table? If so, do I use the chassis wiring column or the power transmission column for determining proper gauge? ...

... In careful engineering the voltage drop, insulation temperature limit, thickness, thermal conductivity, and air convection and temperature should all be taken into account. The Maximum Amps for Power Transmission uses the 700 circular mils per amp rule, which is very very conservative. The Maximum Amps for Chassis Wiring is also a conservative rating, but is meant for wiring in air, and not in a bundle. ...

The Power Transmission rating assumes multiple insulated wires in close contact, heating each other and blocking each other's cooling. The Chassis Wiring rating assume that the individual wires have some air around them. (Jumpers inside a battery box might not get as much air cooling as inside a radio chassis).

 

[Another_David]

The 100% kosher way to do it would be with AMP PIDG piggyback Fastons. You would need the correct crimp tool. I buy this kind of stuff from Mouser Electronics which has no minimum order and low shipping costs.

can we go back to these now that we're talking about 4 batteries with a 14 amp load in a box? I don't like it. This might sound like a bit of nit picking but these connections have a lot of exposed metal. You shouldn't use these if you plan to put the batteries in anything metal or you'll short out the battery when the exposed metal contacts the chassis. Secondly, if you have to pull a single battery you're going to have two live exposed metal tabs floating around. You can get them insulated but there's still some exposed metal, particularly when you don't have the piggy back connection in use.

Easy method would be to get insulated female quick disconnect to mate with the battery tabs then run those wires together with you feed wire and nut them together. You can use push connects if you don't want to twist 5 wires together, which might be hard (impossible?) if you're using 14 ga solid copper.

5 wire push connects are hard to find but they exist: http://www.newark.com/wago/222-415/...n/dp/28K2062?MER=PPSO_N_P_EverywhereElse_None

Those terminal blocks I recommended are exposed too, although some styles are better shielded. If you wanted to make it really nice use the terminal block in a small box and use a panel mount fuse with a light up rocker switch with flip cover.

To be clear, 12 volts is not enough to penetrate the skin so you won't get zapped but shorting these batteries won't be pretty.

Edit: if you're in to wood working, I could imagine making a nifty carrier for those batteries, each with it's own little compartment. wood is a great insulator, nice strength to weight ratio, and finishes nicely.