Basic wiring question

[Wiley]

Aux battery died going to buy a yellow top as I'm limited to choices here. I still have the sears as a starter. Should I still tie these together or do I recall mixing battery types is bad, nut orherwise I'll only have the 120 watt panel charging it. Thanks

[4RunAmok]

Everything I've read and been told, you do NOT mix AGM and Flooded Cell. There is a difference in their voltage capacities. Put the 7622 ACR in manual mode and disconnect them.

Sure would be nice if you could avoid the Optima route, they don't last like they used to.

[LandCruiserPhil]

There can be a lot of argument on wiring fusing and in the end its all about being safe. I break it down into categories 1 being loaded and the other being a dead short. I have #4 between my batteries and fused at 150A. For my application I don't ever see a 150A load being used for no more then 10 sec. in a self jumping situation and #4 fused at 150A is fine. The other side in the event of a dead short I found 150A to blow in under a second. I see my system safe under the perimeters I use it in. That being said I would not dump a 100A load for any given time on #4. The biggest problem with dual battery set up I see is the owner not understanding how his/hers system works. Keep it simple

[4RunAmok]

With regards to mixing battery types, here's where the problem is.. AGM batteries recover/charge faster than Flooded Cell, and mixing the two in a system that pairs them for charging will confuse the voltage regulator, which will continue to deliver voltage at the rate needed by the battery measuring as low, the Flooded Cell, and the voltage regulator will continue to charge both batteries, in essence overcharging the AGM, weakening it, if not kill it!

[Borrego60]

x2

With regards to mixing battery types, here's where the problem is.. AGM batteries recover/charge faster than Flooded Cell, and mixing the two in a system that pairs them for charging will confuse the voltage regulator, which will continue to deliver voltage at the rate needed by the battery measuring as low, the Flooded Cell, and the voltage regulator will continue to charge both batteries, in essence overcharging the AGM, weakening it, if not kill it!

[Wiley]

Unfortunately what I feared. Thanks for the quick replies

[dwh]

With regards to mixing battery types, here's where the problem is.. AGM batteries recover/charge faster than Flooded Cell, and mixing the two in a system that pairs them for charging will confuse the voltage regulator, which will continue to deliver voltage at the rate needed by the battery measuring as low, the Flooded Cell, and the voltage regulator will continue to charge both batteries, in essence overcharging the AGM, weakening it, if not kill it!

Nah.

It's impossible to confuse a voltage regulator. It's just a dumb switch. When the voltage drops to X, it turns on, when the voltage rises to Y, it turns off.

Since both Flooded and AGM batteries are considered fully charged at approximately the same voltage (14.4v while charging or 12.8v resting) it doesn't matter if they are connected together when charging with a dumb charger.

The problem described in the quote happens when batteries of different types (or sizes or ages) are connected to a "smart charger" or "3-stage" charger. I.e., a charger which has an "absorb stage". With that type of charger, then yes, in the absorb stage, what is described in the quote can happen. The charger can get hung up holding an elevated voltage for many hours to get the FLA fully topped off, and it ends up being far too many hours for the AGM. (Or with different size batteries, the smaller gets full first, and ends up overcharged by the time the larger finally gets full.)

But for a dumb single-stage charger (i.e., cheapo benchtop automotive charger, or automotive alternator/voltage regulator setup), or a "two-stage charger" (such as Iota without IQ/4 or a Progressive Dynamics), it's a non-issue. For instance with a 2-stage, since there is no absorb stage, the charger will run a bulk stage until both batteries reach a 14.4v "surface charge" and then the charger will drop down to float voltage and it doesn't matter if the AGM absorbs and reaches full in 12 hours and it takes the FLA 18 hours to get there. Either way, the float voltage isn't going to overcharge anything.

For a dumb benchtop charger, it's likely just taking the batteries to 12.8v and then holding there, and again, it doesn't matter how long it takes each individual battery to finally reach 100% - 12.8v isn't going to overcharge either of them.


You DON'T mix batteries of different types, sizes or ages in a PERMANENT battery bank. You DON'T mix them if charging with a charger that has an absorb stage.

Tying different batteries together WHILE CHARGING with a charger that does not have an absorb stage is fine.

[LandCruiserPhil]

Nah.

It's impossible to confuse a voltage regulator. It's just a dumb switch. When the voltage drops to X, it turns on, when the voltage rises to Y, it turns off.

Since both Flooded and AGM batteries are considered fully charged at approximately the same voltage (14.4v while charging or 12.8v resting) it doesn't matter if they are connected together when charging with a dumb charger.

The problem described in the quote happens when batteries of different types (or sizes or ages) are connected to a "smart charger" or "3-stage" charger. I.e., a charger which has an "absorb stage". With that type of charger, then yes, in the absorb stage, what is described in the quote can happen. The charger can get hung up holding an elevated voltage for many hours to get the FLA fully topped off, and it ends up being far too many hours for the AGM. (Or with different size batteries, the smaller gets full first, and ends up overcharged by the time the larger finally gets full.)

But for a dumb single-stage charger (i.e., cheapo benchtop automotive charger, or automotive alternator/voltage regulator setup), or a "two-stage charger" (such as Iota without IQ/4 or a Progressive Dynamics), it's a non-issue. For instance with a 2-stage, since there is no absorb stage, the charger will run a bulk stage until both batteries reach a 14.4v "surface charge" and then the charger will drop down to float voltage and it doesn't matter if the AGM absorbs and reaches full in 12 hours and it takes the FLA 18 hours to get there. Either way, the float voltage isn't going to overcharge anything.

For a dumb benchtop charger, it's likely just taking the batteries to 12.8v and then holding there, and again, it doesn't matter how long it takes each individual battery to finally reach 100% - 12.8v isn't going to overcharge either of them.


You DON'T mix batteries of different types, sizes or ages in a PERMANENT battery bank. You DON'T mix them if charging with a charger that has an absorb stage.

Tying different batteries together WHILE CHARGING with a charger that does not have an absorb stage is fine.

Does this mean you are safer with a dumb charger then a 3-stage charger if batteries are at different levels and they cannot be separated during charging?

[keezer37]

they cannot be separated during charging?

Am I missing something? The cables cannot be removed from the posts? I have a AGM (sec) and flooded cell (pri), had this set up for five years. I disconnect and run a three stage charge every fall and spring. Flooded takes about 18 hours, Odyssey takes about 3 hours. Same thing every year. Same results every year (almost).

You know, you can gnat's *** this electron flow thing from now until hell freezes over, you will always hear comments about "best practices". The thing to consider is, to what extent is this detrimental? Is this really a concern?

Someone once told me (3 years ago) about the see-saw effect because I have my ground running through the frame. I'm still waiting for that to destroy my batteries.
Horsepucky.

[dwh]

Does this mean you are safer with a dumb charger then a 3-stage charger if batteries are at different levels and they cannot be separated during charging?

Different levels? As in one more drained than the other?

If they are the same size, age and type, then it won't make much difference if one is lower than the other, they'll both end up at the bulk stage surface charge voltage and then require roughly the same time on absorb to reach 100%. So a 3-stage would be okay there.