Connecting batteries in parallel

There are two ways to wire batteries together, parallel and series. The illustration below show how these wiring variations can produce different voltage and amp hour outputs.

In the graphics we’ve used sealed lead acid batteries but the concepts of how units are connected is true of all battery types.

Wiring batteries in parallel and series
Different wiring configurations give us different voltages or amp hour capacities.

This article deals with issues surrounding wiring in parallel (i.e. increasing amp hour capacity). For more information on wiring in series see Connecting batteries in series, or our article on building battery banks.

Connecting in parallel increases amp hour capacity only

The basic concept is that when connecting in parallel, you add the amp hour ratings of the batteries together, but the voltage remains the same. For example:

  • two 6 volt 4.5 Ah batteries wired in parallel are capable of providing 6 volt 9 amp hours (4.5 Ah + 4.5 Ah).
  • four 1.2 volt 2,000 mAh wired in parallel can provide 1.2 volt 8,000 mAh (2,000 mAh x 4).

But what happens if you wire batteries of different voltages and amp hour capacities together in parallel?

Connecting batteries of different voltages in parallel

This is the big “no go area”. The battery with the higher voltage will attempt to charge the battery with the lower voltage to create a balance in the circuit.

  • primary (disposable) batteries – they are not designed to take a charge and so the lower voltage battery is likely to overheat, it may leak or bulge and in extreme circumstances where the voltages are very different, it may explode.
  • secondary (rechargeable) batteries – these only fair a little better. The lower voltage battery is not designed to charge above a certain point, but the higher voltage battery will try anyway. The result can be over heating, leaking or bulging in the lower voltage battery and/or overheating in the higher voltage battery as it drains rapidly. Again, the larger the difference in voltage the greater the chance of fire or explosion.

It’s worth pointing out that many people accidentally connect batteries of different voltages in parallel every day. For example:

  • If you mix brands even of the same labelled voltage – you can experience problems. Due to different manufacturing processes, the exact voltages of batteries from different producers can vary slightly. This means a 1.5 volt battery from brand X could actually be 1.6 volts, while a 1.5 volt battery from brand Y could be 1.55 volts. If these were connected in parallel, you are unlikely to see fireworks, but would experience other issues.
    • for primary (disposable) batteries – the stronger battery would still try to charge the weaker one reducing the lifespan of both.
    • for secondary (rechargeable) batteries – the stronger battery would charge the weaker one, draining itself and wasting energy.
  • If you connect rechargeable batteries in parallel and one is discharged while the others are charged – the charged batteries will attempt to charge the discharged battery. With no resistance to slow this charging process, the charged units can overheat as they rapidly drain and the discharged battery can overheat as it attempts to charge at well above its design capabilities.
  • If you mix batteries of different ages – the older batteries will always have a lower voltage as all batteries self-discharge over time. Even rechargeable batteries will not recharge to the same level as new ones.

As such, the following guidelines are important:

  • With primary (disposable) batteries – only use batteries of the same brand and age (ideally from the same packet). If this isn’t possible, double check the voltages of each unit with a voltmeter.
  • With secondary (rechargeable) batteries – only use batteries of the same brand and age and make sure all the units are fully charged before connecting them together in parallel. If you are uncertain about the state of charge, either connect them individually to a charger until the charger confirms they are fully charged, or check the voltage with a voltmeter.

Connecting batteries of different amp hour capacities in parallel

This is possible and won’t cause any major issues, but it is important to note some potential issues:

  • Check your battery chemistries – Sealed Lead Acid batteries for example have different charge points than flooded lead acid units. This means that if recharging the two together, some batteries will never fully charge. The result here would be sulfation of those that never reach a full state of charge, reducing their lifespan.
  • Double check voltages – if you are using batteries with different amp hour capacities, it is highly likely that the voltages will be different (even if the stated voltage on the labels match). Check this with a voltmeter or you will experience problems (covered in connecting batteries of different voltages in parallel above).

It is for these reasons that you are advised to use batteries of the same brand, voltage and capacity. Failing to do so (if you don’t have the knowledge and tools to check what you are doing) could create a potentially dangerous circuit.

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  1. Peter

    I was looking on amazon for a converter to allow me to use a AA battery in place of a D cell. Many of the ones sold seem to use 3 AA hooked in parralel. This seems very dangerous to me, so I didn’t buy them. What would happen if someone put an alkaline and a NiMH in together?

  2. BatteryGuy Editor

    You never want to mix battery chemistries together. NIMH is meant to be recharged and Alakaline used and thrown out. Very bad idea. If an Alkaline battery were to be charged with a NIMH in a device with a charging circuit, it would probably explode in the device and ruin the product it was in. If it were a standard Lithium battery charged within a device, it could create a fire. In a device not meant to charge the batteries where you mixed Alkaline and NIMH chemistries, one would negate the other battery and damage the device or batteries. NIMH on their own can replace Alkaline, but have to be charged once they run down, the benefit being a longer lifetime. However, never mix the chemistries.

    To replace an Alkaline D Cell with AA Alkaline batteries you would need approx. 6 or 7 AA Alkaline batteries. You would run them in Parralel and it would be based on the AH rating of the AA -vs- the AH rating of the D cell. Most AA cells are around 3AH and most D cells are around 20AH.

  3. mark

    batteries connected in series, Why does it not increase a/h please explain.

    1. BatteryGuy Editor

      EXAMPLE: Two 6 Volt 4.5AH SLA batteries wired in Series would be a total output of 12 Volt 4.5ah. A battery has two terminals, one that gains electrons and one which gives electrons. Within the battery an electrochemical reaction occurs to produce electrons. Since the resistance of a battery is low, when connected in series, an increased concentration of electrons goes to the negative terminal. Once you connect wire from the positive (+) terminal of battery #2 to the negative (-) terminal of battery #1 the concentration of electrons shift toward the negative terminal and join forces in battery #1 as they flow forward.

      Why do the electrons not move to the positive (+) terminal from inside the battery? – This is because of a formation of a magnetic field / barrier which only allows the flow of current in one direction. Since the electrons cannot move against the flow, they move with the current and exit the only viable way via battery #1 through the positive red wire to the object being powered, compensating for the loss of electrons from the positive (+) terminal. The electrons have now combined forces for a total output of 12 volts 4.5ah.

  4. Robert P DiPuppo

    I have a secondary sump pump that is supposed to pump water out of the sump pit in the event I lose power while I’m not at home. This is very important as I live in an area that when the wind blows a little we can lose power. I test this unit monthly and change batteries every 2-3 years. Recently a friend who is a plumber removed a similar system from a house and the former owner gave him permission to take the charger, battery case and battery. He gave it to me and now I want to hook these units together. The batteries are the same voltage, deep cycle marine batteries, however they are from different manufacturers, and I have no idea how old the gifted battery is although it looks newer than my battery which is 18 months in service. My question is this: How do I hook the charging system (which delivers a trickle charge and disconnects when the battery is at maximum) to the batteries when they are in parallel hook up? (I assume parallel is best for this application because the pump is designed for 12v DC so combining 2 would give me longer service at the same voltage. Correct?) Do I need both chargers, one for each battery? [NOTE: Since my battery is 18mos old and I don’t know the age of the other battery, I am content to wait a couple months and buy 2 new identical batteries. I have no long trips planned and I have a generator to power the pump in case of an outage. Unfortunately it’s not a whole house generator but one step at a time.] I would appreciate it if you gave me a sketch or schematic (of the circuit) of how to hook the batteries in parallel with the chargers and the pump. And Thank You Very Much, your time is much appreciated. I’ve had several floods in my basement including 1 with the back up pump installed. The motor seized and my now finished basement needed new drywall and flooring.
    Thank you once again!

    1. BatteryGuy Editor



  5. Lou

    It’s time to replace my 3 12 v batteries wired in series (36V system) with new ones. When removing the old batteries do I remove all 3 negative leads first then do all the positives? Or do I remove one batteries neg. then the same batteries pos. then move to the next and the final battery? I’ll reverse what ever method you recommend when installing of course. Any other tips?Thanks

  6. Kevin Wallace

    I’m upgrading my power in my truck camper because replaced my absorption fridge for a compressor fridge. I bought a new AGM group 31 battery 12 volt. I would like to buy one more new AGM battery but half the size. Both new from same manufacturer same model and wire them parallel. I don’t have space for 2 group 31. What do you think? Thank you

  7. Mark

    Please is it possible to connect two 6volt, 4.5 ah battery together to give 12volts and 9ah?

    1. Greg

      No; you can have either 12 volts, 4.5 Ah or 6 volts, 9 Ah. You can only get as much out of a system as you put into it.

    2. Don Schap

      To get the 12v 9ah result you are asking for would require four-batteries of the 6-volt 4.5ah type. They would be wired in two-pairs. First, you would wire each pair in Parallel to provide the 9ah current (4.5ah + 4.5ah). Then you would wire those two-pairs that you made in Series (treat each pair as a single-battery that you want to stack.) to get them to add 6v + 6v for your desired 12v. Again, it would take four to do this and people do it all the time. It’s how you grow a battery-bank to meet your desired-size in both voltage and current.
      The biggest-rule is that you must use identical-batteries, when you wire them in “Parallel.” The cells are a lot less sensitive to additive-stacking to obtain a higher-voltage.

    3. Doodsky McAwesomesauce

      That would take four 6v 4.5ah batteries. two in parallel to double the AH, and then another pair to double the voltage.
      The Watts, and Amp Hours double in parallel
      the Watts and Voltage double in series.
      double both and you get 108 watts.
      each battery has 27 watts (watts=VxA). You can’t get 108 watts (12vX9ah=108w) out of a pair of 27w batteries. 27X2 batteries=54 watts.

      but… as you increase battery capacity and the load does not change, you actually get more usable AH from the same watts, because the battery chemistry has more time to react, instead of a more rapid discharge that reduces both time and efficiency.

  8. Chris

    If i have two batteries connected in parallel, i want to charge them together by connecting the charger to 1 battery’s positive and the other battery’s negative correct? Also when I’m using them to power my trolling motor do i connect it the same way with the positive of one battery and the negative of the other one?

    1. Don Schap

      If you are actually wired “in Parallel”, the bottoms and tops of the batteries are “electically” at the same place. If you attach your leads to the top and bottom of just one battery… the two batteries will both charge… because they are, already, tied together to operate in that way.

    2. Maria

      It’s better to connect your battery bank to the charger and to the load (trolling motor) the way you proposed. It will work if you connect both hot (+) and ground (-) to the same battery but the battery you connect to will be discharged more and see higher voltage when charging because it experiences less resistance than the other battery. This will make your bank become unbalanced over time and shorten its life.

  9. RS

    I have 4 renogy 6v 260ah batteries hooked to a small 24v system. I had planned on adding battery capacity every year I cant get the renogy’s for some reason so I was wandering if I could a go to a 6v Crown 232ah, and use the batteries I already have. I would like to double my ah but since I cant get them can I go two banks of renogy, and two banks of crown?

  10. Nathan Garcia

    Let’s say I’m using lithium ion tool batteries to power a mini bike I am putting 2 20v 4Ahr in series to make 40 v then I want to put two 20v 2ah in series but parallel with the first two. Do I need to put diodes between the two 40v banks?
    Thank you in advance.

  11. William

    Hey… I have 10 12x 202AH batteries. I wish to create a 24v battery bank. Can you provide a diagram how to wire and recommend what size charger to charge the bank.

  12. Ariel Altura

    Hi, is it possible to connect 2 batteries of 3V 1500 mAh in parallel to get 3000 mAh
    and then connect that pack to another single battery of 3V 1500 mAh in Series to get 6V?

    the 2 packs will have different mAh but the same V

  13. jimmy

    Hi. I am using two identical batteries in parallel that I bought a month ago (12v). If I wanted to increase my ah, can I connect a third identical one (in parallel)? or do i need to increase in pairs?

  14. todd bailey

    I have an rv and need to connect 2 size 8D batteries in parallel. the theory is easy pos to pos, neg to neg, same voltage twice the amperage. easy peasy, right. well not so fast, the batteries only have a single pair of terminals, or rather posts. i need to run some 00 size cable ( yeah that 5/8 dia stuff) between the two batteries while keeping the 1 set of posts available to connect to the rv electrical system. Has any one ever run across an adapter that does this?

  15. Kevin Mullin

    What kind of charge would I get if I hooked up the same charger to each battery separately without connecting the batteries together? (Assuming a 12V charger & two 12V batteries) So there would be 4 wires coming out of my charger:
    From “+” pole of charger to “+” pole of battery A.
    From “-” pole of charger to “-” pole of battery A.
    From “+” pole of charger to “+” pole of battery B.
    From “-” pole of charger to “-” pole of battery B.
    Is there any pro or con to this approach vs a parrallel connection?
    When I tried it the amp needle on my charger seemed to fluctuate a bit.

  16. ernest robbins

    Hey, Battery Guy. My question is: What size wire should be used? What’s the minimum per Voltage, Amps, Etc. and is bigger better or can bigger be too big?

  17. nitram

    How does it work connecting batteries in BOTH series and parallel?
    Isn’t ‘ah’ the capacity? Is the draw from the batteries restricted and there’s less current to deliver?

  18. Trey

    Hi. Thanks for the helpful article. I have a question that no one seems to definitively answer in any of my research as I prep for audio upgrades: Is a fuse necessary between two batteries wired in parallel? One will be in the factory location under the hood. The other will be placed in the trunk for an audio system. I even plan on installing an isolator. Both batteries will be purchased new, at the same time, the same brand, and same model. Thanks

  19. Gianni Brill

    Can I hook in parallel a 12V D8 with a 12V D4 obviously with different amp hour and manufacture?

  20. Tommy

    I’m doing a small solar setup and using one 12v marine battery but also have a seal battery 12v/18ah battery. I like to hook them both up but not sure which is best? I like to keep it 12v but extend my ah by using both. Is this possible? Another reason also is I notice for 2-3 hrs my solar charger is getting more charge then my current marine battery can hold. So thinking adding the second seal battery will help and extend my ah usages.

  21. aji

    your description is parallel two batteries, how about three or four battery in whole parallel connection? can we do it and safe?
    if the battery is same brand and capacity, let’s say that the individual battery is 3,7v 1500mAh each.

  22. Richard

    I have 8 – 2 volt 362ah batteries for a solar bank. I would like to use all the batteries with a 12 volt charger/inverter. My question, can I connect 2 of the 8 in parallel and the remaining batteries in series?
    8 batteries all equal in age and size – 2 volt 362 ah
    2 in parallel = 2 volt 724 ah
    6 in series = 12 volt 362 ah
    Total bank would be 14 volt 1086 ah? will that work?

  23. Billy

    Thank you in advance I recently purchased three thunderbolt Magnum solar batteries 12-volt and hook them in parallel and at 1 say battery number 3 is the battery I hooked up the power inverter to the end I hook the solars plugs into positive battery number three- And then negative battery number one to charge with solar is this correct

  24. DJ

    I have always had the feeling that putting lead-acid or other high capacity batteries in parallel could lead to high currents between the batteries and cause a fire (potentially). To keep me from worrying about it, I put fuses between the batteries. Am I over reacting.

  25. Peter Houlder

    I have 2 12v batteries connected in parralel in a caravan. Therefore the charging and use are to the 1st battery. They work fine but I am told the charge would be better if connected to 2nd battery. Any thoughts thanks

    1. BatteryGuy

      If the wiring is good and the terminal connections are clean and tight it should make no difference.

  26. Kona

    Just asking as I don’t know, If you have 3 1.5 volt button battery’s stacked on top all facing the same way. does this just increase the lifespan of the use or does it increase voltage or AH? Thank you for any thoughts.

  27. Ahmed

    I have two strings of batteries. The first string Four batteries 12V 200AH connected in series to give 48V 200AH. The second string four batteries of 12V 180AH connected in series to give 48V 180AH. Can i connect the two strings now in parallel.

  28. J B

    I have a UPS with 96V battery packs (8 x 12V batteries in series). I’d like to use this as an off-grid power source charged from solar panels. I have a number of 100W 12V panels. Can I attach a parallel wiring harness onto the battery strings to charge them at 12V while leaving the series connections in place to supply the load?

  29. Mark W

    My question is about parallel battery hookups. I would like to use a 12V deep cycle lead acid battery from my trailer to run my 120VAC well pump in emergencies for a short period (through an inverter). The running current to that pump is about 7A, but the startup current, as I measured it, was 38A. Assuming I have an inverter that can handle that startup load (about 38Ax120V=4560W), I’ll also need a battery that can supply that current short term (4560w/12v= approx 380 Amps). The deep cycle battery I have is rated at 400 cranking amps, and after the inverter losses, effects of age ,etc it seems it would be only marginally capable of supplying that surge load. Could I safely parallel a “regular” starting battery from a car (500+ cranking amps available) to this setup for the 30 seconds needed to get the pump started, then disconnnect the car battery and allow the pump to run on the deep cycle battery? Both batteries would be recharged separately with a “smart” solar charger. Thanks for any assistance.

    1. BatteryGuy

      I would suggest you try asking this question on an electrical / pump / off grid forum. We do not sell pumps or inverters so cannot advise on your set up


    I ordered a second 12 volt battery to hook up parallel with the same brand battery. The problem is they sent me a battery that is 56 amp hours and the other is 55 amp hours both 12 volt same brand. Is this going to be a problem? Thank You Craig

    1. BatteryGuy

      Yes, one battery will cause a drag on the other and the lifespan of both will be shortened.

  31. Lea-Carol Glennon

    Hello, I know very little about batteries and I am now living off grid. The house comes with a 6 x 12V battery Outback 200 NC system. I notice the following:
    Battery 1 – Negative post goes to charge controller AND negative connected to negative on battery 3
    Battery 1 – Positive post not connected to anything
    Battery 2 – Negative not connected to anything
    Battery 2 – Positive post connected to positive post on battery 4
    Battery 3 – Negative connected to negative on battery 1 AND connected to negative Battery 5
    Battery 3 – Positive not connected to anything
    Battery 4 – Negative not connected to anything
    Battery 4 – Positive connected to positive post on battery 2
    Battery 5 – Negative connected to negative battery 3
    Battery 5 – Positive not connected to anything
    Battery 6 – Negative not connected to anything
    Battery 6 – Positive post connected to positive post battery 4 AND connected to charge controller

    What does this mean in terms of my system? Is it a 72Volt system? Any guidance much appreciated!

  32. Warren

    I will be running 2 x 120Ah 12V LiFePO4 batteries in parallel in our motorhome, giving us a total storage capacity of 240Ah. Each battery claims to have a continuous current capacity of 100 amps (for use with an AC inverter).

    How is the ‘continuous current capacity’ affected by the parallel connection? Does it remain at 100 amps, or increase to 200 amps?


  33. Dennis

    Could i connect a 150 ah SLD and 180 Gel type battery in parallel?

  34. Patrick

    I am looking tio out a 2nd 12v house battery in my RV, I currently have a group 27 battery in and was wondering if i could safely add a group 24 battery in parallel in order to increase my amp hours?

  35. Francois Provost

    I built 2 LiFePo batteries (8S, 24 V, 176 Ah) with a 100 A BMS each (the one sold by OverKill solar). They are connected in parallel. They are hooked up to a 3000 W interter. When I put a load of 1500 W on the inverter I remarked on the BMS xiaoxiang app that one battery was delivering 38.2 A and the other 26.3 A so that after about an hour, their was 132 Ah left on the first battery and 146 Ah on the second battery. I would like to understant why each battery is not delivering the same current.

    1. BatteryGuy

      As we do not supply inverters we cannot advise and would recommend you ask this question in a specialist/electrical forum.

  36. Pete

    People use nickel or nickel plated steel for battery connectors/tabs in battery packs. I am wondering what improvements/ advantages/ disadvantages you can see with this material or what imporvements could be made here – I dont undersatdn why people use Nickel. Can you help me please?

  37. Alan h Mathies

    You would have 12v @
    4.5ah in that configuration

  38. Kevin Joe Brooks

    I hope you can answer my batteries are all rechargeable ..’m confused..
    My charger is 15 volt ..DC
    I have 1…. 2 volt..5.0 oah d cell

    I have 2..4 packs that I think are in series..
    I don’t know the voltage of the 2 ..4 packs there nothing but dust

    What voltage are the…2….4 packs ?

    I appreciate your help..if the 4 packs are 2 volts each battery…8 batteries X 2 volt each. = 16 volts…+ the single d cell ( 2 volt) = total of 18 volts..

    1. BatteryGuy

      If you are not sure how the packs are wired or the voltage I’m afraid there is very little we can do to help.

  39. Kevin Joe Brooks

    Will the 15 volt wall charger charge the battries..this is all out of a toy you know where I could by all of the battries ? I really appreciate your help

  40. John

    I have 2 batteries connected in parallel. That was easy. I have connectors. How do I connect 4 batteries? All the posts are taken up to connect the 2. How do I reach out to the 2nd two? What kind of connectors do I look for?

  41. Nana Taryana

    When install the Battery in parallel but the cable different length.. whicc cable carrying more load? Longer or short one?

    1. BatteryGuy

      If the cables are of good quality it should make no difference

  42. arthur eugene pletcher

    Is it safe to connect nine 12V 100ah new AGM batteries in parallel using a BUSBAR, with same length wires? Thank you

    1. BatteryGuy

      You would probably be best asking this question in an electrical forum as we do not deal in BUSBARs

  43. Scott Perry

    I have a 52 Packard it’s a 6 volt + ground is there a way to run 2, 6 volt batteries in series and parallel at the same time .so the car stays 6 volt and uses the factory generator and I could run a 12 volt stereo and 12 volt halo headlights.

  44. Karl

    I have 2x200Ah gel batteries. When charged they have the same voltage.
    When I put a fairly light load on them, the one’s voltage will suddenly drop to say 10V. The other one is fine. My first question is what could cause this reastion? What intrigues me is that the voltage returns to almost normal once the load is removed!
    Is there any chance to rectify the problem?
    My other question is what would happen if I connect them in parallel?
    Thank you for your information.
    Regards Karl

    1. BatteryGuy

      The one that drops to 10 volts probably has a faulty cell so can only be treated as a 10ah battery. As such you should not try to wire it in series or parallel with a 12 volt battery.


    Why is it that the charging current draws in a battery connected in parallel is not the same?
    EX. 2 x 200ah 48v connected in parallel
    When the battery is charging at 40Amp the other battery is charging to 20 Amp

    1. BatteryGuy

      It sounds like they are not the same battery. Is on significantly older than the other?

  46. Theodore Hoffert

    We have a rusted away escape hybrid with 6.3 volt nimh’s. Can I use them to replace my lead 12 volts in our rv?

    1. BatteryGuy

      There’s not enough information here for a clear answer. Perhaps refer to your RV manufacturer.

  47. Philip Bailey

    I would like to add a 70ah deep cycle battery in parallel with my 100ah lithium. Both are 12v. The desire is to add additional amps available in my camper. I understand I will need to charge them separately. Will this result in providing 170ah of available power?

  48. Ray

    can I take 2 battery banks already wired in parallel and then wire those 2 battery banks together in parallel to increase voltage and amps

    1. BatteryGuy

      Have a look at the following graphic which shows how to wire in parallel and in series at the same time (3rd graphic in the first row)

  49. Meredith

    Hi Battery Guy,
    Im wondering how you would handle this scenario: I have 4 outdoor string lights and they are each powered by a battery pack of 3 AA batteries. Is there any way I can connect them all together and have them powered by one button (as opposed to turning on four)?
    Apologies if this is answered elsewhere, I looked around but couldn’t find. Thank you

    1. BatteryGuy

      Yes, you could but you would probably need an electrician to wire the lights together correctly so they could all be powered from one source.

  50. Trevor

    I have 4 22v 14ah batteries in paralell (sealed lead acid). I’ve read that 24v is safer so I’m thinking of doing two pairs in series and then connect both pairs in paralell. I’m using an inverter to power appliances. Question, wouldn’t the new lay out mean that I need twice as many batteries to get the same capacity?


  51. Tawanda

    I am getting different voltage readings from 2 batteries connected in parallel. They are both 12v but one is 102ah the other 105ah. When I test, I get 13.2v on A and 12.8v on B even though they are connected. Then 13.2v when I measure across i.e + on A and – on B and 12.8 when it’s – on A and + on B. My charger is on battery A

  52. N Parker

    I purchased 6 – 6V 225 Ah DEEP CYCLE FLOODED batteries my desired outcome is 12volt with the highest Ah possible. How should I wire to achieve this?

  53. David

    Hi. I have 6 agm 12v 120amh batteries I’d like to hook up in parallel config. I’d like to make sure they are balanced. Can you tell me what wiring configuration would be best? Judging from what I’ve read on this site, you are the people who will have the answer.

  54. Jared K

    If you want to run 2 batteries in parallel, can you connect A+ to B+ and A- to B- and then output from battery B + and – ? (instead of output + from battery A and output – from battery B)

  55. Trevor

    I have a e-bike battery it’s lithium ion it has 36 cells in it they’re packed in groups of five I believe one of the packs of five got disconnected the weld connection broke so that pack of five is lower voltage than the rest can I simply just re-weld it to the rest of them and charge it back up to normal or do I have to take them out separately to charge them up fully to match and then reconnect them??

    1. BatteryGuy

      Your best bet here is to contact the ebike manufacturer for advice.

  56. john

    how would i do this , but have a dpdt switch to switch between rhe 12 volt 9 amp hr, and/or 6 volt 9 amp hr?

  57. Denis Kaye

    Would this work?
    Battery 1: 12v 5ah internally fitted to an amplifier.
    Battery 2: 12v 7ah remotely connected in parallel to battery 1
    Both the same brand and age.
    Comments welcomed and appreciated.

    1. BatteryGuy

      No this won’t work. You will end up damaging one or both batteries. In any wiring set up, parallel or series, the batteries should all have the same voltage and amperage. Ideally they should come from the same batch when manufactured.

  58. Luis Capobianco

    I currently have each of my Internet devices power backed up by a 12v rechargeable battery matching or surpassing the amp consumption of the device. Each battery charges from a 12v power supply. When the power goes out, the battery module just continues to provide power. The cost was a fraction of a 220v UPS for the desired capacity.

    Unfortunately, I bought a new equipment that is 24v. I can’t find a similar kind of battery that will provide 24v pass-through charging capabilities (I am not sure if I am using the term right, it can charge and provide power at the same time).

    Is it possible to connect two 12v rechargeable batteries in series to obtain 24v while keeping each connected to a 12v charger (assuming both batteries and chargers are the same)?

  59. Vasant Joseph

    I want to expand the capacity of my powerbank. The existing powerbank is of 12V 2A. I have a lead acid battery of 12V 1.3A. Can i connect my lead acid battery to the powernbank internal battery to expand the capcity.

    1. BatteryGuy

      You would need to consider the following:
      – The batteries in your powerbank must also be lead acid
      – The batteries in your powerbank must also be 12V 1.3Ah (very doubtful if the overall output is 2Ah)

      If either are not true you should not extend the powerbank as you are suggesting.

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