12 volt batteries

It is all about the actual scenario. In my real life scenario there is no problem, because I allow for the mixed set. I can and often have gone four weeks or so on a mixed set of batteries for the last eight years.

There is
A. while camping to get by, and there is
B. at home to get ready for the next camping trip.

While camping, strap what ever collection of batteries together to get the most AH in your bank, and have fun camping. Then at home, separate the various batteries to charge them up according to their various specs to get then truly "full" and desulphated as best you can.

You can now float them as a bunch or separately if they have different floating specs until it is time to head out again.

EG, I have a pair of 6v Exide 135s rated at 226AH but more like 200 last test for that, in parallel with two beat up (ex-golf car) T-1275s in parallel, so the two big 12s are in parallel as one 12. The 150 rated 12s are now about 118 each last test, so total bank is about 436AH let's say.

Going great for camping up to four or so weeks in a row-just did that- (have solar plus a gen if it clags in). Get only 0.6 voltage drop with the microwave on, plus the furnace on ( morning instant coffee water in kettle, plus a furnace hit to take the chill off at 0 dark 30, and a light so I can see)

I just don't understand all these posts about explosions and personal doom if you mix your battery bank. All you need to do is whenever you do get some shore power, is bring each battery up to speed separately to meet its own specs, before banking them all again for more for camping fun time.

To do that, you do need battery chargers that can do the various battery specs' charging profiles--IE, an adjustable voltage charger or two. Your one and only RV converter is probably not going to cut the mustard. However there are lots of other chargers that can.


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Matt,
ABC Battery provided me with a Mix & Match pallet of 8-D batteries to test. Their curiosity infectious. How do good used batteries get along with brand new batteries.

I tested them in groups of (4) paralleled. Brought them to 14.0 volts for 4 hours until all indicated they were absororbing < .5 ampere each.

I forgot the number of batteries. Age is creeping up to me but my best recollection says (24) DUTs.

Three or four batteries of the pallet failed to reduce to .5 ampere or less. They were rejected on the spot.

The test protocol was to raise voltage in .10 volt steps for a period of 2 hours and observe the level of gassing in all 24 cells at the 2 hour point.

Of the pallet total only three made it to the 14.5 volt stage. To be specific, 3 batteries had 18 cells bubbling equally at 14.5 volts. I believe 3 other new batteries did not reach that point. Therefore they failed to pass.

Even though the batteries that "failed" the test could pass the BCI carbon pile load test, they did not pass with equality. 500 ampere load was applied for 15 seconds, and voltage droop was used as the comparison. Load was then adjusted to achieve voltage equivalence. A span of 10% amperage was noted. I forgot to add here, all DUTs were 29 plate 8-D's. All fell within the 143 to 147 pounds weight category.

Conclusion?

These guys had personalities. Generally speaking age of DUT was a major influence (as determined by lid date code branding.

At >14 volts the personalities really came into their own. Some batteries would bubble with consistency while others did not.

I ran out of time. This was a "trade" agreement. ABC was to build ,070" plate group 24 batteries for me to see if car car batteries could tolerate true cyclable 5% antimony plates.

Keep in mind, all batteries passed the BCI load test. None failed a hydrometer dipping.

Reduce maintenance voltage to agree with the first sign of bubbling. Maintenance voltage is the potential at which eliminates a majority of bubbling. Some commercial marine batteries would see maintenance voltage for weeks at a time. It was generally agreed upon that 13.6 volts was safe at 65F.

Jerry told me he now had conclusive ammunition to insist his commercial vessel batteries be kept at 13.6 volts. He said most draggers and tuna boats were referencing 14.0 volts as an alternator voltage set point.

The experiment with the heavy plate group 24 battery was a tremendous failure. Laughably so. Many of them load tested to 200 CCA agmperes or less. But subsequently failed entirely. Autopsy revealed severe acid starvation.

I am going to stand back and read subsequent comments about this on the forum. My reward for aching fingers posting this :)

You can all believe what you want, and I will not interfere.

I did a lot of boat work on big expensive boats before the depression of 2010 hit here hard. A lot of what I (or we - company) did was house power upgrades of performance cruisers (retired racing sloops). Many had increased the house bank by simply adding to it.

The resulting banks ware always a disappoint to the owner in that they never got the added capacity that was expected. This is because they could not effectively charge the two different 12V jars. The internal resistance and leakage resistance all change with age, cycles and temperature. Even if the jars are adjacent, the one that absorbs the most charge will get warmer and so charge better.

The thing I liked most about 12V jars strapped in parallel was that I would get an emergency call to come and clean up after a bank explosion. This means that I had to pack up and tote lots of clean-up gear and then bill the owner's insurance company for the clean-up and required repairs. I still have the standard cover letter in my file if you should need it to explain to your carrier that this was not a foreseeable event and a direct result of a lack of proper maintenance.

Just if you plan to do this, please carry at least two boxes of baking soda onboard to neutralize the spilled acid.

Also look up the article "Balance of Power" by Gary Bunzer that was in Family Motor Coaching - January 2012. I am sure it is out there somewhere. You will have to read it as the pictures show both the typical wrong ways and some better ways to do this.

Matt

CJW8 wrote:
In a pinch, yes it is ok short term. New install- get two new identical batteries.

My post and this post is the only accurate post on this subject. Interstate Battery will replace ALL batteries in a battery bank under warranty if just one battery fails because it is NOT a good idea to mix batteries. Doug

3 oaks and Scott beat me to it. :R

In a pinch, yes it is ok short term. New install- get two new identical batteries.

No real problem as long as both batteries are indeed still functioning fine. Ideally, mixing batteries of different age or brands will not give you the best results over the long haul, but for short term expectations they will suffice. Biggest problem is they will charge and discharge at different rates with the weakest battery of the pair causing the stronger battery to languish in overall performance. If one battery is particularly weaker than the other, using Blue Sea or Perko marine battery selector switch could be incorporated to keep them isolated until they are needed. Otherwise, if both are healthy and strong keeping them paired up would take advantage of Peukert's Law.

JimVan wrote:
Is there any problem mixing 2 different brands of batteries

No.

When they die get two that match.

3oaks wrote:

Matt_Colie wrote:
Jim,
..........................................
If you are going to strap 2ea 12V jars in parallel, expect trouble. Even if the batteries came off the final line sequentially, they still will not necessarily play nicely in parallel. Lead acid batteries just don't do that well..................

Really? :R

I got 9 years use from my two 12v lead acid batteries connected in parallel before I traded for a new TT. That's more than good enough for me. :)

Not to mention every diesel truck and millions of floor scrubbers.
The only possible problem is very long term storage where they tend to discharge each other.
Otherwise it just isn't a big deal.

Matt_Colie wrote:
Jim,
..........................................
If you are going to strap 2ea 12V jars in parallel, expect trouble. Even if the batteries came off the final line sequentially, they still will not necessarily play nicely in parallel. Lead acid batteries just don't do that well..................

Really? :R

I got 9 years use from my two 12v lead acid batteries connected in parallel before I traded for a new TT. That's more than good enough for me. :)