Building a battery Pack

[jharkin]

BTW, person at NOCO said they do not recommend charging and drawing at the same time.

Not suprising, the load on the battery will ocnfuse the microprossessor in the charger and it wont know when to switch from bulk to absorb, etc.

A system like your cars charging circuit can handle charging with a load because its a simple fixed voltage source. It just keeps the battery at 14.5 volts and supplies as much or as little current the battery will take at that voltage. As the battery gets full the current will just taper off to zero.

 

[mass_burner]

so a 3 stage charger will prevent overcharging because it will go into float mode and maintain the battery.

saw this one: http://www.amazon.com/Duracell-D15A...383669094&sr=1-11&keywords=AGM+15+amp+charger

 

[mass_burner]

this charger recommends 6 - 50 Ah batteries. if i'm charging my battery pack, wouldn't that be a 105 AH battery. why does the charger care about the AH of the battery?

 

[woodgeek]

because the trickle current is proportional to Ah.

 

[mass_burner]

so could i use this charger on my battery bank as a whole?

 

[mass_burner]

i think this is it: for AGM, do not exceed the C/3 rule:

C (AH) / 3 hours = C/3 A

so my battery bank would be 105AH/3=35A, or it would take 35A to charge it in 3 hours. so for C/7 (7 hours), I would need 15 A charge rate.

 

[mass_burner]

Finally finished my rolling battery pack for now. Decided to go with 70 ah to start, can always scale up later.

 

[woodgeek]

Finally finished my rolling battery pack for now. Decided to go with 70 ah to start, can always scale up later.

Usually you wire parallel like this:

to ensure they charge evenly....prob a 2 minute change.

 

[mass_burner]

Hmmm. I would need to reposition the inverter toward the center of the top to keep the cables the same length. I was planning on using most of the top as a platform/table top for whatever. But I guess I'll have two smaller areas except one larger one.

 

[mass_burner]

also, would I put both charging clamps on one battery, or 1 clamp on each each end?

 

[mass_burner]

is this guy doing it wrong?

http://mymilescity.com/how-to-solar-power/parallel_wiring_batteries.html

 

[woodgeek]

is this guy doing it wrong?

http://mymilescity.com/how-to-solar-power/parallel_wiring_batteries.html

its a subtle issue, but yes, he is. The connectivity is obviously correct, but if you substituted the wires for resistors, the batteries would not charge evenly. I don't know how big an issue is, but hypothetically it becomes a problem when the resistance of the cables is close to the effective resistance of the batteries...and I could imagine that could be pretty low.

For something to see light duty from time to time, you are prob aok. For an off-grid solar system doing heavy duty, I would do it the symmetric way.

I don't think you should move the inverter, just make two longer cables. And I would charge it symmetrically also.....one clamp on each battery.

 

[jharkin]

Agree with geek. With parallel setup they typically run the positive to one battery and the negative to the other. In fact off grid folks try to avoid parralel as much as possible and run series. You avoid a lot of problems that way, no need to balance and if you ever get a bad cell its obvious in series.

 

[mellow]

I ran my batteries in parallel like woodgeek showed when I was doing car stereo competitions back in the day... way back in the day.

 

[mass_burner]

thanks for the info, I will make the corrections. maybe is why my charger read 95% charged after I had a 1amp fan for 3 hours.

 

[mass_burner]

I have a smaller xantrrex 600 HD pack and just replaced the battery. I am not happy with the charging rates (35 hours using house plug) and would like to charge the battery directly using my smart charger.

Would there be any issues to adding cables directly from the battery out through the case for attaching to my charger?

 

[woodgeek]

Not that I can see....so long as the Ah and chemistry are appropriate for the charger.

 

[mass_burner]

Battery is 12v, 26 ah. My charger has built in step down amp rate to maintenance.

 

[mass_burner]

So, this Xantrex pack has jumper cables you use to jump a car, 50 AMP. They plug into the side and are removable. The user manual says you can hook up the jumper cables to another battery and extend the capacity of the pack. So if the that's true, won't the battery in the xantrex be charged via these same cables by a charger?

 

[woodgeek]

I would think so. Do you know the charger is SLA and not Gel Cell? I had a Jumper pack at on one time that was a bunch of NiCads strung together. I wouldn't want to use a Lead-Acid charger on that.

 

[mass_burner]

The charger has a setting for AGM, GEL and STD. The battery is AGM, I just replaced it.