MIXING BATTERIES ?

[larglo]

Hi all,

I have one deep cycle battery, but have not used it as I don't have a way yet to charge it. I was going to get new group 29 battery the first of the month, and I think the one I have now is a group 27. I was also going to buy a single battery charger. I wasn't going to use the group 27 battery, but I was wondering if I could use both the group 27 and the new group 29 batteries together as house batteries?

They could have separate chargers even thought they will be hooked together in order to get a higher amp hour. Would there be a problem hooking the two together even though they will have separate chargers? Tomorrow, I'm bring the group 27 home check the water and charge it, the fellows at West Marine tested it and said it looked OK.

Any thoughts you have would be a lot of help.

Awwwww spring.

Larry

[Big D]

You should always have similar batteries in size, rating and age that make up a given bank. I never heard of two chargers on one bank, don't know if it would work as you plan. I'm not sure but one of the chargers may see a conflict or detect a high enough voltage (from the other charger) and not put out anything at all thinking that the bank is already charged. I wonder if you'll create a loop where both chargers will keep turning on and off. Has anybody else tried this?

[wowzer52]

You would be fine if you use them one at a time by putting a switch in between. When one gets to 50% switch to the other. The same when charging. charge one at a time. This will lengthen the life of both batteries. Even if you use two chargers you need to seperate the batteries due to the different sizes and ratings.

[larglo]

How do you charge a two battery bank connected in parallel,,with one charger?
How would you hook up the leads of the charger,,the pos lead to the pos post of one battery and the neg lead connected to the neg post of the other battery? If both batteries were the same type, etc.

Larry

[Allen Sr]

If both batteries are connected together as one bank then it won't make a difference which terminals are connected to as long as positive is connected to positive and neg. to neg. I/E battery's have to be wired paralell not in series. In series would make for increased voltage wich you don't want. You want increased amperage so you need to wire paralell. You could use two matching batteries as one bank and a single as another just keep them separated with a perko switch. I know your more confused than ever now after I put my 2cts worth in!

[g36]

yes big d 2 chargers on one battery will keep each from charging properly easily seen with digital meters on the chargers showing a reduction to basically no output. becasue they will be "fighting"each other. a constant output charger of course would be different story

larglo dont make this too complicated its simple
in parallel (battery switch to both)for use as a house bank you look at the batteries together and consider them to be like one big battery. for charging you will need to seperate them using some type of disconnect (1-2 or both perko switch etc) but they could be of different sizes it wouldnt matter for use as the house battery bank. the amperage of the smaller battery will shorten the total amperage you have to use so you will still need some means of measuring this. as stated earlier you could use them seperate (battery switch to 1 or 2) and switch over to the other when apx 50 % is used. but you shouldnt leave them together and use 2 seperate chargers that would not charge each seperately which they will need, regardless if they were different sizes or the same size. each battery will need its own charger use the 2 you have or such as a multibank charger. or charge each one at a time with one charger switching them after each is charged. i wouldnt reccommend this. more of pita it would be smarter to use a multibank charger with a disconnect(perko battery switch etc). after some time the chemistries of the batteries will change and IF left parrallel ALL the time and charged with ONE charger one battery could start to ge t weaker than the other and require more to charge it, then the charger will over charge one because it thinks the battery is still needing charging and so on. this would shorten the life of the good battery then. so just make sure that you can disconnect them and you will have no problems

[larglo]

Are you all saying that every one having multiple batteries (battery banks) as house batteries separate the batteries when you charge them?

I was going to have the start battery completely separated from the house batteries and use it the same way as in a car. The engine will charge the battery when running, but have on board charger when at the dock for it

My house batteries were to be connected in parallel so as to increase the amp hours, and use 2 on board chargers to charge them rather than buy a charger that charges two batteries at a time, which I'm not sure I trust?

I already have a deep cell battery, but not sure what type (group) etc. I was hoping to buy a second deep cell to use with it. If I can buy the second deep cell the same type as the one I have now,,,,I will,,,but if I couldn't, I wasn't sure if I could still hook it to my present deep cell?

But from what I can figure out from what I'm reading here is,,,,,,,,

I can't charge a house bank (of 2 batteries) with 2 separate chargers, and I will have to separate the house batteries either by using a switch to separate them or unhook them in order to charge them, separately. I'm glad I wasn't planning on using more that 2 batteries in the bank, otherwise I'll be spending most of my time charging all the batteries. I didn't realize that battery banks had to be separated before they are charged?

I think my best bet is to throw my present house battery into the lake, throw my fridge into the lake, use only the start battery and keep the charger connected to it as it is now,,,,,buy me a big a$$ cooler,,,,and forget the whole frigin' thing,,,,,,

Larry

[g36]

man i really think you are worrying about this way to much.
leave the engine start battery just as you have it. if you just want to charge the house bank at the dock

if you want to charge battereis correctly then they must be charged seperately. a switch is the simpiliest method to understand
my house bank is tied to one engine so as i am running i may have my switch on both or maybe or 1 or the other. they will charge but when i am done for the day or tied to shore power i turn my switch so they arent parallel and my charger takes over each seperately

.if you have 2 batteries parralleled. the pos and negatives of each battery are hooked together. putting a charger on the actual terminals of each battery will be the same as hooking it up anywhere on the cable or connecting the 2 chargers together. thats what the switch does it breaks the parallel connection. when you charge the batteries seperate them by turning the switch. if not, just use one charger because putting 2 chargers wont help do anything. if you want to charge two batteries in parralel its not going to fry anything its just not going to be the optimal way to do it. thats all i am saying. you asked how to do it. just trying to simplify this so its easy to understand

[larglo]

I guess what I'm confussed about is the idea I have to charge each of the batteries of a bank seperately using one charger?

When I Google searched this subject there was this picture of 6 batteries hooked in parellel. It did not mention how the batteries were charged, but if I had to place a switch between each battery or unhook each battery and charge it, by it's self, then that's not for me.

Thanks for trying to help though.

Larry

[g36]

dont concern yourself with 6 your only trying to do 2.
post the link. their doing something more than just hooking up batteries and putting on a charger to charge them all.

[larglo]

Try this answer on for size, it goes on and on about all this crap,,,,and NEVER answers the question. It's enough to drive ya crazy.

http://www.rversonline.org/ArtFAQ8.html

Larry

[g36]

i have an rv also. i can tell you that the convertor that is mentioned is also breaking out 110v for the rv in addtion to be a 12vdc power supply and battery charger. something we arent discussing. the 12 vdc reference to boondocking is in principal the same for the boat. i use 6 volt golf cart battereis for my trojan and also my rv. i have them in series and in parrallel as mentioned. you are confusing this whole thing. forget the rv link and please reread what i have posted. it is very simple for 2 batteries to be connected in the way you want. and charged properly with a switch. if you dont want to use the switch then realize you might not charge both batteries completely. they will be charged and one might be overcharged(depending on its own electrolyte value) but the charger will keep charging till its sees the set voltage for the charger. like i said you arent going to fry anything it just is not the best method for battery life

[larglo]

OK, I'll try this,,Lets say the 2 batteries are connected in parallel, this I understand, so,,,if I take a switch,,say a heavy duty toggle switch and place it between the neg cable of the two batteries, then to charge each battery seperatly, throw the switch, thus breaking the connection between the 2 batteries, I can then charge the two batteried seperatly.

If I'm on the right track here, I'll be brave and take it a step farther,,,,could I hook a charger to each battery or use a single charger that can charge 2 batters at once,,,,OR use the single charger to charge them one at a time?

Holding my breath on this one.

Larry

[larglo]

Just found this on line, what do ya think?



How to Charge Two 12 Volt Batteries with One Charger

I’ve seen quite a few people coming to this site with search queries identical to this article’s title. Since there is nothing explicitly written anywhere on how to charge two 12 volt batteries with a single 12 volt battery charger, here you go. Really, it’s quite simple, but there are a few “best practices” to keep in mind.

The first thing you need to do is to take the batteries out of the vehicle. It’s not actually a strict requirement, but it’s a very good thing to do. You don’t need to mess up your vehicle electrical system, and if you’ve got two batteries, who knows how they’re connected, what they power, if you have a charging isolator, or other complications.

Now that the batteries are safely on your workbench, connect them together in parallel. Take a set of jumper cables and connect the positive terminal of one battery to the positive terminal of the other battery. Do the same for the two negative terminals. Remember to keep things simple – the red goes to positive, the black goes to negative.

By connecting the two batteries in parallel, we are allowing the charge between them to equalize – if one battery is charged more than the other, then the excess charge in one will be driven to the other, until the charge (measured by voltage) is exactly the same on each battery.

Be sure not to connect a completely dead battery to a fully charged battery. The amount of differential voltage can tend to send a large amount of current (amperage) to the dead battery, causing a significant amount of heat to build up. This is a bad thing and should be avoided. If you have a completely dead battery, charge it on its own before connecting the two together.

Finally you need to connect your battery charger. Now here’s the trick: don’t just connect the charger directly to one battery. Instead, connect the positive lead from the charger to the positive terminal on one battery, then connect the negative lead on the charger to the negative terminal on the second battery. This is a small detail, and in truth makes only a bit of difference.

Turn on the charger, and let it do its thing. Remember to select the correct amperage on your charger for you battery type (although not all chargers give you the choice), and also remember that you’ll need twice the time to charge two batteries in parallel as you would need to charge a single battery.

We hope this helps – have more questions? Ask below and we’ll see what we can do!


Larry

[Paul]

Hi Larry,

Below is a simple diagram of how to connect and charge two identical batteries for a dedicated house bank. No switches. This set up will recharge only when your plugged into shore power. (no alternator charging) If you want to recharge with the alternator, let me know and I'll draw you another diagram.



Hope this helps.