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Dual Battery Set up.

Discussion in 'Commercial Snow Removal' started by GeoffD, Nov 26, 2001.

  1. GeoffD

    GeoffD PlowSite.com Veteran
    Messages: 2,266

    When you guys do your dual battery set ups on picks ups how do you do it. Do you connect the two + terminals together, and ground the - on the second battery. Or do you Connect the two + terminals together, and also connect the two - terminals together?

    Kinda going back and forth on which way is the correct way.

  2. CT18fireman

    CT18fireman Banned
    Messages: 2,133

    I ground the second battery. Running the ground cable is really uneccessary because the steel of the truck will provide a route just as well as the biggest power cable. Make sure that you use good clean connectors and clean grounds.
  3. Rooster

    Rooster Member
    from Kansas
    Messages: 650


    I connect postive to postive and only run 1 ground.

  4. DaveK

    DaveK Senior Member
    Messages: 420

    I have been thinking about installing a second battery. But not just wired together. The trouble with that is that both batteries must be the same identical batteries of the same age. If not, the weaker battery will actually drain from the stronger one.
    The best way is to use some form of battery isolation.

    A simple method is to install a constant duty solenoid between the 2 batteries. So that when the engine is running, both batteries are connected, system will draw off both, and both will be charged. When engine is not running, solenoid cuts out and connection between both batteries is cut. Another advantage is that if the main battery goes dead (leave lights on) you can power the solenoid from the good battery and jump start yourself , with a cab mounted push button switch wired from the secondary battery to the solenoid you wouldn't even have to open the hood.

    Then there are true battery isolators that send the charging current to the battery that needs it most when engine is running, and isolates them when not.

    Then I found this, (haven't actually ordered it yet, still considering the simplicity of the solenoid setup, see the bottom of this post) a review of a product from Hellroaring Technologies, Inc. You can get an optional remote module to put the switch right in the cab. You would simply turn the system to ON when you are plowing or need a self-jump, or AUTO when not plowing, or OFF when you plan on using power for an extended time with the engine off (so that you won't drain the second battery. The system is $129.95 The remote module is $39.95 So together it's $169.90 with only $5.00 shipping to anywhere in the U.S. and only $10 to our canadian friends.
    The best thing about this setup is that you can use different size batteries. Maybe one optima and one regular? One deep cycle?

    This quote is from Hellroaring's website, Hellroaring.com
    Here is a good solenoid setup wiring diagram
    Last edited: Nov 27, 2001
  5. DaveO

    DaveO PlowSite.com Veteran
    from Ma.
    Messages: 299


    Good info on the dual battery setup. Isolators are a good idea, used commonly in marine applications.

    It is preferred to have the same type/size of batteries, but not necessary. It is correct that if one of the batteries is weaker, it will charge off the stronger when the charging system is off. When the two batteries equalize(voltage wise), that will stop.

    Two different capacity batteries will not do this unless one is weak. The static voltage difference is the only concern, not the available current capacity(cranking amps).


    Neg to Neg is preferred, providing the existing battery has a good ground cable. Especially for electric/hydro packs. They almost always connect to the battery negative, not chassis ground. In fact Fisher has seen some problems when customers connected the negative to the frame instead of the battery. This may create a poor ground to the electric motor in the SEHP, resulting in poor operation, and arching of the motor shaft(trying to get to ground).

  6. John Allin

    John Allin PlowSite.com Addict
    Messages: 1,327

    You guys make me glad I have a full time mechanic..... I get confused easily.
  7. jason2

    jason2 PlowSite.com Veteran
    Messages: 117

    Another company to offer dual battery setups is Painless wiring. They offer different multi-battery solutions. One neat product they have is a battery manager. It allows use of: Main only, normal, main + aux 1, main + aux 2, maintainer, main + aux1 + aux2. They have marine grade 250 amp dual battery kits. Plus lot's of other goodies. all controllable from in the cab.

    I will be buying from them in the future. Lot's of the 4x4 crowd swears by their products.
  8. DaveK

    DaveK Senior Member
    Messages: 420

    In reply to DaveO
    I don't think that is entirely correct, it has something to do with the charging of two different capacity batteries. I think the lower capacity batt can be overcharged (I'm not an electrical engineer, so don't hang me if I'm wrong):) I am just going by what I have read in the following two quotes.

    In reply to jason2
    Hellroaring has the same (can have three batts) but I didn't think many people here would actually want or need three. I'm suprised to see their (Painless wiring's) website up. Back when I was researching this I found information reffering them (including the website address) but could not get to the website. ( I bookmarked it and tried every few days to see if it was just a server problem, but after about 2 weeks, I gave up.
    Last edited: Nov 27, 2001
  9. DaveO

    DaveO PlowSite.com Veteran
    from Ma.
    Messages: 299

    Dual Batteries


    There is no hanging on this site. Just goes to show you that you can't always believe what you read, especially from someone trying to sell you something.

    Without getting into the electronics in detail.....If one battery is ALMOST dead it will load down the alternator, and the other battery. It will not stop the other battery from charging. A battery is like a transformer, as it charges up, it draws less current from the source(impedance changes). Provided the charging system does not exceed 15VDC, the battery will not overcharge. FYI common car/truck/bike batteries have 6 cells. Each cell is capable of charging to 2.2VDC, thus totaling 13.2VDC when fully charged. If you measure a fully charged battery, it will be closer to 12.8VDC, because the "surface charge" drains off fast. If you charge it OVER ~15VDC, it willl "boil out" and end up damaged.

    I install a second battery in many of my customers "bikes" without any problems. And I don't usually use the same size/capacity either due to space considerations. Done this for years.

    BTW...I am an electrical engineer working for a leading audio manufacturer. In case you were wondering....

  10. CT18fireman

    CT18fireman Banned
    Messages: 2,133

    I have used different size battery connected without isolators in my boats and trucks. Now I have gone all Optima Yellow tops (blue for the boat) so they are all the same. When I ran differents I never had a problem. I always recommend to put the most powerful (amps) battery that you can run.
  11. GeoffD

    GeoffD PlowSite.com Veteran
    Messages: 2,266

    Even with full time mechanics, they still come to the boss with the electronics degree some days.

    And its been a while from my last visit to school.

  12. DaveK

    DaveK Senior Member
    Messages: 420

    That is assuming that the engine is running and charging.

    See INFO #2 below. Why would they recommend using relays to cut charging of the string when the voltage reaches to an adjusted voltage if they cannot be overcharged?

    Yes, I knew this.

    I have read that you should use batteries of the same capacity from sources that are not trying to sell anything.

    INFO #1 "In the PARALLEL CONNECTION, batteries of like voltages and capacities are connected to increase the capacity of the bank. The positive terminals of all batteries are connected together, or to a common conductor, and all negative terminals are connected in the same manner. The final voltage remains unchanged while the capacity of the bank is the sum of the capacities of the individual batteries of this connection. Amp-Hours Cranking Performance and Reserve Capacity increases while Voltage does not."


    INFO #2 “you should never connect non homogeneous (same capacity) batteries in parallel. Batteries connected in parallel must be even of the same age (as the sulfating occurs a resistance as well) The smaller in capacity batteries, are charged quicker. During charging you can disconnect the strings with relays and charge the strings simultaneously separated by diodes. Then each string will need a voltage control unit to cut charging of the string when the voltage reaches to an adjusted voltage. When all strings reach to the adjusted voltage then charging is stopped automatically or manually and relays will close to reconnect the batteries' strings.” The last quote was from a discussion group at http://csf.colorado.edu

    Some info about over discharging here. “OVERDISCHARGING is a problem which originates from insufficient battery capacity causing the batteries to be overworked. Discharges deeper than 50% (in reality well below 12.0 Volts or 1.200 Specific Gravity) significantly shorten the Cycle Life of a battery without increasing the usable depth of cycle. Infrequent or inadequate complete recharging can also cause overdischarging symptoms called SULFATION. Despite that charging equipment is regulating back properly, overdischarging symptoms are displayed as loss of battery capacity and lower than normal specific gravity. Sulfation occurs when sulfur from the electrolyte combines with the lead on the plates and forms lead-sulfate. Once this condition becomes chronic, battery chargers will not remove the hardened sulfate. Sulfation can usually be removed by a proper desulfation or equalization charge with external manual battery chargers. To accomplish this task, the flooded plate batteries must be charged at 6 to 10 amps. at 2.4 to 2.5 volts per cell until all cells are gassing freely and their specific gravity returns to their full charge concentration. Sealed AGM batteries should be brought to 2.35 volts per cell and then discharged to 1.75 volts per cell and their this process must be repeated until the capacity returns to the battery. Gel batteries may not recover. In most cases, the battery may be returned to complete its service life after performing this.”

    I am not saying that you must use an isolator on a dual battery system. They don’t put them on at the factory for trucks with dual batteries, but then they have identical batteries don’t they. From all the information I have found, you are the only one who claims that you can use different capacity batteries without an isolator. All the others say they must be the same capacity and often say they must be the same age. Sure it will work, but not for as long, especially with gel batteries (see proper desulfation above) unless you want to perform proper desulfation on your batteries when the capacity is reduced. And who wants to spend their free time doing that.

    Besides using different capacity batteries, the isolators (either from Hellroaring or Painless or many others ) offer other great benefits. Self jump for when you drain the main battery. You can even run your vehicle electrical system off one battery, and your plow off the other. Those are MAJOR benefits. They have been using these on RVs (for extended power use ) and off-road 4x4s (winches, lights etc.) for years.

    CT18fireman "When I ran differents I never had a problem" So are you still using the same batteries, or was their useful life used up? Perhaps prematurely?

    BTW...I am an not an electrical engineer. I'm not a computer programmer either, although I do have a degree in computer programming. In case you were wondering.... But when I have an interest in anything, I do in depth research till I find the facts and understand them fully.
    Last edited: Nov 28, 2001
  13. wolfie

    wolfie Senior Member
    Messages: 174

    Chevy has an isolated dual battery option available. It use 600 CCA & a 770 CCA batteries. the RPO code is 8BO I found out about it too late to get it on my new truck. I'm going to see how it goes with the standard 600 CCA battery this year and then decide what to do next.
  14. CT18fireman

    CT18fireman Banned
    Messages: 2,133

    No the reason I switched was that I put a single Optima into my 4runner which has a stereo system. Worked well. So I swapped all my batteries that year to Optimas (Expensive but worth it IMO) I have done different size batteries in other people's trucks and they are still running strong today.
  15. DaveK

    DaveK Senior Member
    Messages: 420

    Well, look at that. Even the factory uses an isolator when there are two different capacity batteries. That must mean something. I am sure that GM has a large team of electrical engineers that know what they are doing. I don't think they would use an isolator if it wasn't needed. (somebody would eventually file a class action lawsuit claiming that their batteries didn't last as long as they could have)

    I don't doubt that. You can also mix alkaline and nicad batteries in your flashlight and it will work, but it isn't recommended. And certainly doesn't give the optimum performance or optimum battery life.

    I am already convinced that with different capacity batteries, you shuold have an isolator. But I will continue to research it to find undisputable evidence that will convince the non-beleivers, if needed. If anyone else can find undisputable evidence from a credible source, please post it.
  16. CT18fireman

    CT18fireman Banned
    Messages: 2,133

    Their pumps and accessories work better than with one battery and the truck starts every morning. What more could they want in terms of battery performance?
  17. DaveO

    DaveO PlowSite.com Veteran
    from Ma.
    Messages: 299


    Obviously you have read a fair amount on this subject. I would have guessed on the degree in Computers, based on your proficiency(sp) with the keyboard. I really don't want to get into a pissin contest on this issue. So......

    Yes a parallel circuit will increase current with NO increase in voltage. Electronics 101. Two batteries of the same voltage and SIMILIAR capacity(i.e. 400 vs 500 CCA) will function perfectly, with no decreased lifespan. Yes the smaller capacity will charge up faster, but this creates no problems. When the smaller battery is charged fully it will stop drawing current, and the other battery will draw the rest as needed. On the same note, the smaller battery will discharge quicker also due to it's reduced current capacity. Again this is not normally a problem. REMEMBER, THAT NO TWO BATTERIES ARE EXACTLY THE SAME IN CAPACITY, there will always be production variances. The batteries will always split the load requirement in half, providing each can supply 1/2 of the current demand.

    About sulfation....Everything you stated is correct. The most common cause of sulfation is a heavily discharged battery(low S.G.) exposed to freezing temperatures. This causes the sulfation to occur on the plates. As you stated, you have to "shock" this coating off the plates to recover the battery's performance by a high current, high voltage cycle. This is VERY common in vehicles unused for extended periods in the winter months. This method is usually only utilized on lead/acid batteries. And they average about an 80-90% recovery of performance. We have never seen 100% recovery. And I have NEVER performed this on GEL cells, only lead/acids. Sulfation is the leading failure mechanism on lead/acids.

    The whole point of having two batteries in a plow truck is to have DOUBLE the current reserve to supply power to the electric/hydro pump. Isolating one will just leave you with a one battery supply. Yes there are many other benefits to isolation, but we are more concerned with the current available during a "surge", just like a stater motor concern. This is why diesels have dual batteries, to ensure starting after glow plug/grid heater operation, and then a high torque starter demanding current.

    I find it ironic that I am the ONLY person who has these beliefs. I do NOT argue that two identical batteries of the same age is preferred. But my experience and education supports my belief that it is not NECESSARY. You seem to be relying TOTALLY on verbage aquired from a couple of different sources. Like I said, don't always believe what you read(including my advice...LOL). There is always a difference between the textbook and the lab(real world) also. My best advice to you would be to use experience to assist your knowledge gained by research. I have found this to be VERY beneficial to me in the past.

    Just FYI....REAL world example, not copied from an educational site....LOL. I installed a Fisher E Force harness on a customers F250 powerstroke. It was fairly involved, took a few hours. Required disconnecting both batteries. After finishing I connected up only one battery to test it. The truck refused to start, and the pump perated erratically. Appeared to have inadequate current suppply. So I connected the 2nd battery up. Truck started, ran fine, electric/hydro worked fine. I checked the S.G. on both batteries, and one was basically dead, the other 90%+ charged. I mentioned it to the customer when he picked it up. He said "yea, I know that battery is N/G, " he had replaced ONLY ONE battery TWO YEARS AGO. The truck runs/plows OK. Is he going to reduce the life of the new battery? Maybe, but it hasn't killed it in 2 years. Definitely not suggested IMO.

    GM electrical engineers that know what they are doing? No wonder they pay me to design/test audio equipment for their "high end" vehicles. I suppose they save $$ by paying me to do it.

    Good job on the homework BTW.

    Last edited: Nov 28, 2001
  18. DaveK

    DaveK Senior Member
    Messages: 420

    But in this application (snow plowing) they are not isolated during use, only when the key is turned off, or when not plowing. We aren't talking about "bikes" here, at least I'm not.

    Perhaps you should re-read my posts, I don't think I ever stated that it was NECESSARY. I said that it "is preferred" and "the best way." For those that will accept less than the best, mix your batteries however you want. But for me, and I am sure others, that DO want the best preferred method, it will be two identical (in age AND capacity) OR battery isolation. And I think that being able to give my truck a self-jump, when needed is a worth a few extra bucks. Will it save me money in the long run, who knows, but when you are stranded or your truck won't start on a cold morning when you really need it, money isn't my first concern.

    I don't find it ironic, I find it questionable. Since I am not an electrical engineer, my credibility is not at stake. I am not relying on my experience or education as you are, therefor I can only rely on multiple outside sources (you are ONLY relying on your education and experience). Then when I feel that I have adequate information, I simply believe the most prevalent facts. Which in this case, is that an isolator while not NECESSARY, is certainly the BEST way to combine batteries of differing capacities. <small>I put it in bold so that Dave0 won't miss my point this time.</small>

    I think I would have then disconnected the "dead" battery so that the reduction of life for the good battery wouldn't be "Maybe..." common sense 101.

    I don't know why you were LOL. Is there something wrong with educational sites that I am not aware of. No matter how intelligent a person is or thinks they are, education should be a life-long commitment. Learning shouldn't stop after achieving any degree.

    Perhaps they are busy designing battery isolators and leaving the easy stuff to the less fortunate electrical engineers. LOL (I finally saw some humor in this topic)

    Do you tell your customers that you aren't doing it the preferred or best way?

    One quick question for Dave0.... Do they use many dual battery setups in "high end" car audio these days? Never mind, I'll ask my brother-in-law, he doesn't have a degree in anything but he does work for Siemens testing anti-lock brake systems and compass/GPS systems.

    Both Dave0 and I have said that using an isolator is the best preferred method to connect differing capacity and/or age batteries, although not necessary. That is what I have said throughout this thread. I have never claimed that is was necessary, and in fact I stated that it was not necessary. It appears that Dave0 has somehow reached the conclusion that I said it was necessary. And it also seems that Dave0 is discouraging the use of isolators. (why, I don't know) At least that is how I see it since we have both said virtually the same thing. I on the other hand am encouraging the use of them when it is the best way. That is the only real difference of opinion that I can see.

    Don't try to patronize me. And I never did homework when I was in school.

    FYI... I have NEVER competed in a pissin contest. Debates are another story.
    Last edited: Nov 28, 2001
  19. CT18fireman

    CT18fireman Banned
    Messages: 2,133

    Easy guys!

    Actually many competition car stereos may use 5-6 batteries to handle the power going to the amps. Add to this capacitors and you are talking about a lot of amps.

    While you may decrease the life of the batteries I think the obverall benefit outweighs this. Installing the biggest batteries you can fit will lead to your accessories getting the most current they need. Total amps is what is important.
  20. DaveK

    DaveK Senior Member
    Messages: 420

    CT18fireman, I am going easy. :) Neither of us mentioned competition car stereos. And the stereo itself doesn't require multiple batteries. Certainly not the ones used in "high end" automobiles.

    I am not sure what you mean by that. It sounds as if you are saying either
    1) having 2 batteries will decrease the life but having more power is worth it.
    2)you think one of us is saying that simply having two batteries will decrease their life, but it is worth it.

    You didn't mention "with or without an isolator" or "same size or differing size batteries" which is what is being discussed.