AGM deep cycle state of charge table?

[NickBee]

I have seen Sly's post on deep cycles and his chart. But I think AGM batteries sit at a slightly higher voltage. I have seen a few charts online but I am wondering if someone has a reliable chart that they know works.

Today I used my 80AH AGM deep cycle for the 1st time. I charged 5 6s 3300's (from 30%) and my resting voltage is at 12.68. I think the resting voltage at full charge was around 12.85.

Thanks!

[Slyster]

Free energy! I would 'guess' that the deep cycle is simply holding its voltage better than a lead/acid and the voltage will drop more sharply towards the end and my chart would still apply. Again just a guess.. I'll wait for others to chime in.

[NickBee]

Originally Posted by Slyster

Free energy! I would 'guess' that the deep cycle is simply holding its voltage better than a lead/acid and the voltage will drop more sharply towards the end and my chart would still apply. Again just a guess.. I'll wait for others to chime in.

Who knows. See this chart which kinda makes sense.

Just wondering if anyone using an AGM has seen results consistent with something like this chart.

[Slyster]

Yeah that charge kindof proves the point that the different batteries end up the same.. but the AGMs hold their voltage longer.

[Crowbar]

Just got my first deep cycle battery today. Not a big one (13Ah/20Ah AGM) but it fills out my charging case quite nicely and should provide for 8 full recharges of the 450's batteries ( 13.000 / 0.8 * 2.200 = 0.74, I rarely run my batteries down to 20% though).

It's a 12V AGM battery and according to my research, those should be somewhere between 12.65V and 12.8V when fully charged.

My chargers (all IMAX B6 clones or originals, don't know really) an I can only tell it how many cells to use in the Pb charging program. Choosing 6 cells shows up as 12V so I went with that and set it to 1.3A charging rate (i.e. 1/10 C). Now it's hovering at 14.70V charge and the charger went down to 0.5A charging rate. Am I correct that this battery is full? I barely put 1 Ah into it.

I also noticed that when using it as a power source to charge LiPos (with the same charger), I'm not getting 12V input voltage (charging at 6A). Also the cable with crocodile clamps on one end and 12V plug on the other end (came with all the chargers) gets warm when I use the deep cycle as power source. Is that okay? Can't really solder another cable on because the 12V plug is quite small.

Here's the full battery name:
Longex 12LCP-12 / 12V - 13Ah AGM Deep Cycle
It has a 20Ah capacity but says you should only use 13Ah of it

[willr001]

At my work, we make large battery powered machines. A wet cell we use 10.5 as the cutoff voltage, and AGM we use 10.875.

AGM batteries you only want to discharge a max of 70% versus the wet's 80%.

Sent from my Nexus 4 using Tapatalk 2

[Slyster]

Don't worry about deep cycles voltage (except for the low end).. they will always be over 13v when full and cannot be overcharged.

When the voltage drop, amps go up... = hotter wires. If you put two in parallel for 24V the wires would stay room temp.. but for you.. you can just get bigger wires if you want.. like 10awg.

Deep cycles voltage sags a lot when charging.. normal.

Plus... the more you use it the better it gets. Deep cycles really need 5-10 solid cycles to reach full capacity.

and always store full!

[Crowbar]

Awesome, thanks for the super fast and informative replies.
My cable says 22 AWG on it (it says " AWM 2468 22AWG VW-1 80°C 300V " on the red wire insulation).

[Slyster]

wow those are tiny! do they have bullets? or go straight into the charger? I'd see about moving to at least 12AWG (thicker)

plus I just noticed you are using small chargers.. I doubt they could handle 24v input!... don't try that unless you look up the specs.

[willr001]

To clarify, my voltages I gave are for no or small load, but also no recovery time. If the battery sits idle, the voltage recovers to what is in that resting voltage state of charge table that was posted, and as Sly said, fully loaded voltages will be lower and don't mean too much.

And also seconding what Sly said, forget your lipo habits and store lead cells fully charged. It's worth repeating.

[NickBee]

Originally Posted by Slyster

Don't worry about deep cycles voltage (except for the low end).. they will always be over 13v when full and cannot be overcharged.

When the voltage drop, amps go up... = hotter wires. If you put two in parallel for 24V the wires would stay room temp.. but for you.. you can just get bigger wires if you want.. like 10awg.

Deep cycles voltage sags a lot when charging.. normal.

Plus... the more you use it the better it gets. Deep cycles really need 5-10 solid cycles to reach full capacity.

and always store full!

+1... but two batts in series for 24V, not parallel

[Slyster]

opps.. my mistake!

[Crowbar]

Nah, the chargers take 11V-18V DC input. The built-in power supplies say around 15V on the display. No 24V fun there.
I don't know whether I can solder thicker wires to that 12V AC plug (it's the same as you have on these standard 9V or 12V power bricks), the cables just come out of it.

Also, does it matter whether I connect or disconnect + and - in a certain order? I know it matters on a car because negative is connected to the chassis and accidentally touching the metal bits of the car with the red cable just instantly solders the cable to the car and the battery shorts out.

Here's my charger case if you curious. Took forever to make it all weight-balanced and still fit all the chargers and cables in there: https://www.helifreak.com/showthread...55#post5098755

[Crowbar]

Resoldered some cables and had a test run today. My deep cycle now has a deans connector.
Charges up 2 2200 3S lipos in 20 minutes with no extra heat in the cables.

Pulling 6 Amps out of the battery using the old 10 AWG cable made it dance around 30°C (86°C), that was 7°C more than ambient temperature, still worked well though and didn't get any hotter than that. Now it's all cool with the thicker cables though. And it's much more easy to charge and discharge now. Just gotta be careful not to run my finger through the deans plug when disconnecting. I got zapped twice a few years back awkwardly unplugging a power cable from a power strip under the bed in the USA. European plugs have twice the voltage but are insulated everywhere but the tip of the plug so you can't just halfway plug it in and short it with your finger.

Shorting 200mAh 2S LiPos (cable failure) was already exciting, don't wanna know what a 13.000 mAh 6 cell battery will do.