Battery Voltage question

[Outnabout]

My AGM batteries show 70-80% SOC but when not getting charge from solar, night, the voltage drops to below 12v. My batteries are on the older side. Is this the signal that they are shot? Thanks.

 

[pvstoy]

Might be.

If you can bring them up to 100 percent, disconnect all loads and see what the resting voltage is. Put a load on it and see how fast the volts go down.

All this is easy after you get the battery fully charged take it to a place locally to get it load tested.

How old are those battery?

 

[Outnabout]

Thanks. The batteries are 9 years old and have been treated with care but they are old. I can’t get the batteries up to 100% in my current situation but when I turned off the fridge I could get a resting voltage of 12.6 to last through the night. I should just get new batteries as it is probably time but I always remain curious for future reference. Thanks again.

 

[craig333]

You did well getting nine years out of them.

 

[pvstoy]

Thanks. The batteries are 9 years old and have been treated with care but they are old. I can’t get the batteries up to 100% in my current situation but when I turned off the fridge I could get a resting voltage of 12.6 to last through the night. I should just get new batteries as it is probably time but I always remain curious for future reference. Thanks again.

+Craig's post... 9 years is great!

Resting voltage is fine but getting it to 100 percent and have it rest then put some load on it will give you a idea.

Agree that if you are questing them now, then for peace and ease of mind replacing them now when you have the time might be more pleasant than rushing later.

I have 9 years going on my 2015 Flatbed Hawk. Seems to be doing fine. Since we bought it used the two 80 amp hour batteries have been well cared for.

Let us know what replacements you source as I might be getting close for replacement also. There was a post a couple years back that discussed sources of true RV deep cycle AGM's.

 

[Outnabout]

Mine is 2015 Grandby. Original batteries. It has been really hot on this trip so maybe that was the last straw for them. Thanks again. I will post what I find about replacements. Renogy has a 200ah AGM. Need to check dimensions.

 

[pods8]

Have you considered going lithium? That renogy AGM is $400, you can get a 200ah lithium under $550 or a pair of 100ah under $600.

 

[pvstoy]

I have thought going lithium, but the two agm have been serving our need well. With 480 watts of solar recharge has been doing well. Thought of seeing if two larger agm would fit in the space.

Cost is a factor for the lithium along with needing to change out the ACR relay to DC to DC adding more cost. We dont use the ACR, just relay on solar

I do like that the manual switch with the ACR allows the truck AGM battery to be charged with the IOTA using the same AGM charger profile as the camper batteries. Plus allows to connect all three batteries and alternator for extra capacity for air compressor, or even a jump start if truck battery goes dead.

Charged batteries couple weeks ago with IOTA and camper batteries are sitting at 12.87 volts.

When I was doing all the wiring and installing all the upgrades, then was the time to switch to lithium. At the moment the system just plain works for our needs. Replacing just the 9 year old batteries is cheaper, less work and should get us the same level of proformance for years to come.

Sure if someone plopped lithium batteries and a DC to DC charger in front of me ,I sure would not complain. I do see the advantages with lithium. At the moment it is the calculation, return on you invested dollars.

Have you considered going lithium? That renogy AGM is $400, you can get a 200ah lithium under $550 or a pair of 100ah under $600.

 

[Outnabout]

I hear you about going the lithium route. I am not crazy about all the added wiring for dc-dc and the cost factor. The big Renogy won’t fit in my battery box, too wide.

I do wonder if I just changed my solar charge controller, my current one is not lithium compatible, and only used solar to charge the battery if that could work. My existing panel is 160w and I have a 100w portable to supplement when parked. I was thinking Victron 100/30 MPPT controller. I already have a Victron shunt.

What do you think about only charging with the solar I current own? I could also plug in occasionally if needed. I realize my IOTA does not charge to the lithium profile but in reading KP’s manifesto, it could do a good enough job. I only use power for my 12v compressor fridge and phone charging.

Thanks!

 

[Outnabout]

Have you considered going lithium? That renogy AGM is $400, you can get a 200ah lithium under $550 or a pair of 100ah under $600.

I have considered but am not crazy about added expense of hardware. I wonder if I could charge enough with a 160w panel and a compatible controller. My current one is not lithium compatible. I also have a 100w portable panel.

 

[pods8]

I have considered but am not crazy about added expense of hardware. I wonder if I could charge enough with a 160w panel and a compatible controller. My current one is not lithium compatible. I also have a 100w portable panel.

Do you have an old PWM controller? A smart solar victron mppt 75/15 is $67 on Amazon so it’s not a major expense to gain lithium compatibility and mppt (vs pwm) if you were inclined.

Completely cool if you want to run AGM as is, I just get the impression some folks may not be aware of the pricing shifts on this stuff in the last year or two.

There are <$300 100ah lithium batteries that are fully usable (vs ideally never using more than 50% of a 200ah lead acid battery) that have temp protection and Bluetooth BMS that tell you what is going on with the battery vs guessing off voltage. When those batteries were $600+ a couple years ago the price dynamic was a totally different situation.

 

[Outnabout]

Yes, I have an old PWM and would go Victron. I was just looking at SOK batteries and they seem reasonable compared to a AGM of similar useful capacity, as you said 100ah usable versus 200ah and only 50%. Thanks for pointing out the price drops recently. More research on my end now. Question for you: I have a Victron smartshunt, can I use that in lieu of the battery BMS or will it interfere somehow with battery BMS. Thanks again

 

[pods8]

I had a hiccup with SOK (look in the members forum). I was planning to go with powerurus (when my trailer batteries wore down) and recommend a couple friends to do so (who are happy). The SOK price drops got me to go that route initially but too much drama unfortunately. I sent those back and got some powerurus as originally planned and they tested out fine. Aside from the silly name the teardowns of the powerurus show really good built quality.

All lithium batteries have an internal BMS, some have more features like low temp protection and Bluetooth connectivity. You can run a shunt with them still.

 

[craig333]

MPPT is not a requirement for lithium batteries. I did install a DC DC charger but solar does the bulk of the work. You could probably get by with just solar and maybe an occasional charge from the IOTA.

 

[pair to draw to]

My AGM batteries show 70-80% SOC but when not getting charge from solar, night, the voltage drops to below 12v. My batteries are on the older side. Is this the signal that they are shot? Thanks.

AGM yesterday report from desi the Harley rider. Pushing his bike when his fairly new AGM went south. “What gives”
The subject really interest us we’ve switched back to wet lead batteries over the years after having to have newest/best in everything. A behavior which I call throwing $ down a rat hole. Currently running two Walmart wet leads in our real tree badlands camper. Two motorcrafts in the 7.3 power stroke. The built 97 Cherokee Laredo another motor craft. Current build a67 C-j six banger another with a wet lead o-Riley’s special.
Soooo.. we just buy new batteries every year and chalk it up to cost of doing business in the south west heat.

 

[pods8]

MPPT is not a requirement for lithium batteries.

I didn’t mean to imply it was. But if he had an old controller that wasn’t lithium compatible (which was likely a lower cost pwm) AND wanted to upgrade it to one that was you might as well go mppt was what I was trying to suggest.

 

[Outnabout]

I had a hiccup with SOK (look in the members forum). I was planning to go with powerurus (when my trailer batteries wore down) and recommend a couple friends to do so (who are happy). The SOK price drops got me to go that route initially but too much drama unfortunately. I sent those back and got some powerurus as originally planned and they tested out fine. Aside from the silly name the teardowns of the powerurus show really good built quality.

All lithium batteries have an internal BMS, some have more features like low temp protection and Bluetooth connectivity. You can run a shunt with them still.

I have read about this hiccup with SOK that has an internal heater. Supposedly they have fixed this with an updated BMS. I appreciate you sharing your experience with SOK and the powerurus. No problems sending back the SOK and getting your money back? Did you get them from their site? Ok, time for me to do more research! Thanks

 

[pods8]

I have read about this hiccup with SOK that has an internal heater. Supposedly they have fixed this with an updated BMS. I appreciate you sharing your experience with SOK and the powerurus. No problems sending back the SOK and getting your money back? Did you get them from their site? Ok, time for me to do more research! Thanks

My issues had nothing to do with the heated battery specifically, it seemed like it was going to be a nice product. My issue was after a month of dealing with things I still didn't have a pair of working batteries that I ordered. I was tired of dealing with their mistakes/issues.

They sent me the wrong batteries (which were even mismatched within that shipment). Then sent me the right batteries but one performed very poorly. The "bad" one only discharged to 83ah and #4 cell had a large differential when it cut out. The acceptable one still underperformed a tad at 98-99ah and on that one the #4 cell was also creating a larger voltage differential which was a little concerning but I was going to accept it. Then the replacement they sent me was again the wrong battery, I was just over dealing with it.

On the flipside the powerurus replacements I ordered were the correct battery the first time and both discharged to ~101.5-101.8ah without any glitches, thus with days of placing an order I had two correct matching batteries.

I had ordered directly from SOK and yes the were polite in customer service and accepted the return and issued a refund.

 

[Outnabout]

+Craig's post... 9 years is great!

Resting voltage is fine but getting it to 100 percent and have it rest then put some load on it will give you a idea.

Agree that if you are questing them now, then for peace and ease of mind replacing them now when you have the time might be more pleasant than rushing later.

I have 9 years going on my 2015 Flatbed Hawk. Seems to be doing fine. Since we bought it used the two 80 amp hour batteries have been well cared for.

Let us know what replacements you source as I might be getting close for replacement also. There was a post a couple years back that discussed sources of true RV deep cycle AGM's.

Thanks for the advice to get the batteries load test. I brought them up to 100% and took them down to the auto parts store. One was in the 25% of life and the other was bad. Now to decide the route to take with replacement. Some of the well rated lithiums are less than the AGM replacement costs. I was already think of upgrading my 15+ year old controller. Maybe I will just depend on solar and see how that goes. Thanks again

 

[Outnabout]

The Powerurus looks like a nice battery and gets a good review. Did you get the self heating model? I would like to go skiing in winter and it seems as this might be necessary to keep the battery charging. Do you have any experience with using in cold temperatures? Thanks again for your advice.